jshell/tool/JShellTool.java

/*
 * Copyright (c) 2014, 2016, Oracle and/or its affiliates. All rights reserved.
 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
 *
 * This code is free software; you can redistribute it and/or modify it
 * under the terms of the GNU General Public License version 2 only, as
 * published by the Free Software Foundation.  Oracle designates this
 * particular file as subject to the "Classpath" exception as provided
 * by Oracle in the LICENSE file that accompanied this code.
 *
 * This code is distributed in the hope that it will be useful, but WITHOUT
 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
 * version 2 for more details (a copy is included in the LICENSE file that
 * accompanied this code).
 *
 * You should have received a copy of the GNU General Public License version
 * 2 along with this work; if not, write to the Free Software Foundation,
 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
 *
 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
 * or visit www.oracle.com if you need additional information or have any
 * questions.
 */

package jdk.internal.jshell.tool;

import java.io.BufferedReader;
import java.io.BufferedWriter;
import java.io.File;
import java.io.FileNotFoundException;
import java.io.FileReader;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.io.PrintStream;
import java.io.Reader;
import java.io.StringReader;
import java.nio.charset.Charset;
import java.nio.file.FileSystems;
import java.nio.file.Files;
import java.nio.file.Path;
import java.nio.file.Paths;
import java.text.MessageFormat;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.Collection;
import java.util.Collections;
import java.util.HashMap;
import java.util.HashSet;
import java.util.Iterator;
import java.util.LinkedHashMap;
import java.util.LinkedHashSet;
import java.util.List;
import java.util.Locale;
import java.util.Map;
import java.util.Map.Entry;
import java.util.Scanner;
import java.util.Set;
import java.util.function.Consumer;
import java.util.function.Predicate;
import java.util.prefs.Preferences;
import java.util.regex.Matcher;
import java.util.regex.Pattern;
import java.util.stream.Collectors;
import java.util.stream.Stream;
import java.util.stream.StreamSupport;

import jdk.internal.jshell.debug.InternalDebugControl;
import jdk.internal.jshell.tool.IOContext.InputInterruptedException;
import jdk.jshell.DeclarationSnippet;
import jdk.jshell.Diag;
import jdk.jshell.EvalException;
import jdk.jshell.ExpressionSnippet;
import jdk.jshell.ImportSnippet;
import jdk.jshell.JShell;
import jdk.jshell.JShell.Subscription;
import jdk.jshell.MethodSnippet;
import jdk.jshell.Snippet;
import jdk.jshell.Snippet.Status;
import jdk.jshell.SnippetEvent;
import jdk.jshell.SourceCodeAnalysis;
import jdk.jshell.SourceCodeAnalysis.CompletionInfo;
import jdk.jshell.SourceCodeAnalysis.Suggestion;
import jdk.jshell.TypeDeclSnippet;
import jdk.jshell.UnresolvedReferenceException;
import jdk.jshell.VarSnippet;

import static java.nio.file.StandardOpenOption.CREATE;
import static java.nio.file.StandardOpenOption.TRUNCATE_EXISTING;
import static java.nio.file.StandardOpenOption.WRITE;
import java.util.MissingResourceException;
import java.util.Optional;
import java.util.ResourceBundle;
import java.util.ServiceLoader;
import java.util.Spliterators;
import java.util.function.Function;
import java.util.function.Supplier;
import jdk.internal.joptsimple.*;
import jdk.internal.jshell.tool.Feedback.FormatAction;
import jdk.internal.jshell.tool.Feedback.FormatCase;
import jdk.internal.jshell.tool.Feedback.FormatErrors;
import jdk.internal.jshell.tool.Feedback.FormatResolve;
import jdk.internal.jshell.tool.Feedback.FormatUnresolved;
import jdk.internal.jshell.tool.Feedback.FormatWhen;
import jdk.internal.editor.spi.BuildInEditorProvider;
import jdk.internal.editor.external.ExternalEditor;
import static java.util.Arrays.asList;
import static java.util.Arrays.stream;
import static java.util.stream.Collectors.joining;
import static java.util.stream.Collectors.toList;
import static jdk.jshell.Snippet.SubKind.VAR_VALUE_SUBKIND;
import static java.util.stream.Collectors.toMap;
import static jdk.internal.jshell.debug.InternalDebugControl.DBG_COMPA;
import static jdk.internal.jshell.debug.InternalDebugControl.DBG_DEP;
import static jdk.internal.jshell.debug.InternalDebugControl.DBG_EVNT;
import static jdk.internal.jshell.debug.InternalDebugControl.DBG_FMGR;
import static jdk.internal.jshell.debug.InternalDebugControl.DBG_GEN;
import static jdk.internal.jshell.debug.InternalDebugControl.DBG_WRAP;
import static jdk.internal.jshell.tool.ContinuousCompletionProvider.STARTSWITH_MATCHER;

/**
 * Command line REPL tool for Java using the JShell API.
 * @author Robert Field
 */
public class JShellTool implements MessageHandler {

    private static final Pattern LINEBREAK = Pattern.compile("\\R");
            static final String RECORD_SEPARATOR = "\u241E";
    private static final String RB_NAME_PREFIX  = "jdk.internal.jshell.tool.resources";
    private static final String VERSION_RB_NAME = RB_NAME_PREFIX + ".version";
    private static final String L10N_RB_NAME    = RB_NAME_PREFIX + ".l10n";

    final InputStream cmdin;
    final PrintStream cmdout;
    final PrintStream cmderr;
    final PrintStream console;
    final InputStream userin;
    final PrintStream userout;
    final PrintStream usererr;
    final PersistentStorage prefs;
    final Map<String, String> envvars;
    final Locale locale;

    final Feedback feedback = new Feedback();

    /**
     * The complete constructor for the tool (used by test harnesses).
     * @param cmdin command line input -- snippets and commands
     * @param cmdout command line output, feedback including errors
     * @param cmderr start-up errors and debugging info
     * @param console console control interaction
     * @param userin code execution input, or null to use IOContext
     * @param userout code execution output  -- System.out.printf("hi")
     * @param usererr code execution error stream  -- System.err.printf("Oops")
     * @param prefs persistence implementation to use
     * @param envvars environment variable mapping to use
     * @param locale locale to use
     */
    JShellTool(InputStream cmdin, PrintStream cmdout, PrintStream cmderr,
            PrintStream console,
            InputStream userin, PrintStream userout, PrintStream usererr,
            PersistentStorage prefs, Map<String, String> envvars, Locale locale) {
        this.cmdin = cmdin;
        this.cmdout = cmdout;
        this.cmderr = cmderr;
        this.console = console;
        this.userin = userin != null ? userin : new InputStream() {
            @Override
            public int read() throws IOException {
                return input.readUserInput();
            }
        };
        this.userout = userout;
        this.usererr = usererr;
        this.prefs = prefs;
        this.envvars = envvars;
        this.locale = locale;
    }

    private ResourceBundle versionRB = null;
    private ResourceBundle outputRB  = null;

    private IOContext input = null;
    private boolean regenerateOnDeath = true;
    private boolean live = false;
    private Options options;

    SourceCodeAnalysis analysis;
    private JShell state = null;
    Subscription shutdownSubscription = null;

    static final EditorSetting BUILT_IN_EDITOR = new EditorSetting(null, false);

    private boolean debug = false;
    public boolean testPrompt = false;
    private Startup startup = null;
    private boolean isCurrentlyRunningStartup = false;
    private String executionControlSpec = null;
    private EditorSetting editor = BUILT_IN_EDITOR;

    private static final String[] EDITOR_ENV_VARS = new String[] {
        "JSHELLEDITOR", "VISUAL", "EDITOR"};

    // Commands and snippets which can be replayed
    private ReplayableHistory replayableHistory;
    private ReplayableHistory replayableHistoryPrevious;

    static final String STARTUP_KEY  = "STARTUP";
    static final String EDITOR_KEY   = "EDITOR";
    static final String FEEDBACK_KEY = "FEEDBACK";
    static final String MODE_KEY     = "MODE";
    static final String REPLAY_RESTORE_KEY = "REPLAY_RESTORE";

    static final Pattern BUILTIN_FILE_PATTERN = Pattern.compile("\\w+");
    static final String BUILTIN_FILE_PATH_FORMAT = "/jdk/jshell/tool/resources/%s.jsh";

    // match anything followed by whitespace
    private static final Pattern OPTION_PRE_PATTERN =
            Pattern.compile("\\s*(\\S+\\s+)*?");
    // match a (possibly incomplete) option flag with optional double-dash and/or internal dashes
    private static final Pattern OPTION_PATTERN =
            Pattern.compile(OPTION_PRE_PATTERN.pattern() + "(?<dd>-??)(?<flag>-([a-z][a-z\\-]*)?)");
    // match an option flag and a (possibly missing or incomplete) value
    private static final Pattern OPTION_VALUE_PATTERN =
            Pattern.compile(OPTION_PATTERN.pattern() + "\\s+(?<val>\\S*)");

    // Tool id (tid) mapping: the three name spaces
    NameSpace mainNamespace;
    NameSpace startNamespace;
    NameSpace errorNamespace;

    // Tool id (tid) mapping: the current name spaces
    NameSpace currentNameSpace;

    Map<Snippet, SnippetInfo> mapSnippet;

    // Kinds of compiler/runtime init options
    private enum OptionKind {
        CLASS_PATH("--class-path", true),
        MODULE_PATH("--module-path", true),
        ADD_MODULES("--add-modules", false),
        ADD_EXPORTS("--add-exports", false),
        TO_COMPILER("-C", false, false, true, false),
        TO_REMOTE_VM("-R", false, false, false, true),;
        final String optionFlag;
        final boolean onlyOne;
        final boolean passFlag;
        final boolean toCompiler;
        final boolean toRemoteVm;

        private OptionKind(String optionFlag, boolean onlyOne) {
            this(optionFlag, onlyOne, true, true, true);
        }

        private OptionKind(String optionFlag, boolean onlyOne, boolean passFlag,
                boolean toCompiler, boolean toRemoteVm) {
            this.optionFlag = optionFlag;
            this.onlyOne = onlyOne;
            this.passFlag = passFlag;
            this.toCompiler = toCompiler;
            this.toRemoteVm = toRemoteVm;
        }

    }

    // compiler/runtime init option values
    private static class Options {

        private Map<OptionKind, List<String>> optMap = new HashMap<>();

        private String[] selectOptions(Predicate<Entry<OptionKind, List<String>>> pred) {
            return optMap.entrySet().stream()
                    .filter(pred)
                    .flatMap(e -> e.getValue().stream())
                    .toArray(String[]::new);
        }

        String[] remoteVmOptions() {
            return selectOptions(e -> e.getKey().toRemoteVm);
        }

        String[] compilerOptions() {
            return selectOptions(e -> e.getKey().toCompiler);
        }

        String[] commonOptions() {
            return selectOptions(e -> e.getKey().passFlag);
        }

        void addAll(OptionKind kind, Collection<String> vals) {
            optMap.computeIfAbsent(kind, k -> new ArrayList<>())
                    .addAll(vals);
        }

        void override(Options newer) {
            newer.optMap.entrySet().stream()
                    .forEach(e -> {
                        if (e.getKey().onlyOne) {
                            // Only one allowed, override last
                            optMap.put(e.getKey(), e.getValue());
                        } else {
                            // Additive
                            addAll(e.getKey(), e.getValue());
                        }
                    });
        }
    }

    // base option parsing of /env, /reload, and /reset and command-line options
    private class OptionParserBase {

        final OptionParser parser = new OptionParser();
        private final OptionSpec<String> argClassPath = parser.accepts("class-path").withRequiredArg();
        private final OptionSpec<String> argModulePath = parser.accepts("module-path").withRequiredArg();
        private final OptionSpec<String> argAddModules = parser.accepts("add-modules").withRequiredArg();
        private final OptionSpec<String> argAddExports = parser.accepts("add-exports").withRequiredArg();
        private final NonOptionArgumentSpec<String> argNonOptions = parser.nonOptions();

        private Options opts = new Options();
        private List<String> nonOptions;
        private boolean failed = false;

        List<String> nonOptions() {
            return nonOptions;
        }

        void msg(String key, Object... args) {
            errormsg(key, args);
        }

        Options parse(String[] args) throws OptionException {
            try {
                OptionSet oset = parser.parse(args);
                nonOptions = oset.valuesOf(argNonOptions);
                return parse(oset);
            } catch (OptionException ex) {
                if (ex.options().isEmpty()) {
                    msg("jshell.err.opt.invalid", stream(args).collect(joining(", ")));
                } else {
                    boolean isKnown = parser.recognizedOptions().containsKey(ex.options().iterator().next());
                    msg(isKnown
                            ? "jshell.err.opt.arg"
                            : "jshell.err.opt.unknown",
                            ex.options()
                            .stream()
                            .collect(joining(", ")));
                }
                return null;
            }
        }

        // check that the supplied string represent valid class/module paths
        // converting any ~/ to user home
        private Collection<String> validPaths(Collection<String> vals, String context, boolean isModulePath) {
            Stream<String> result = vals.stream()
                    .map(s -> Arrays.stream(s.split(File.pathSeparator))
                        .map(sp -> toPathResolvingUserHome(sp))
                        .filter(p -> checkValidPathEntry(p, context, isModulePath))
                        .map(p -> p.toString())
                        .collect(Collectors.joining(File.pathSeparator)));
            if (failed) {
                return Collections.emptyList();
            } else {
                return result.collect(toList());
            }
        }

        // Adapted from compiler method Locations.checkValidModulePathEntry
        private boolean checkValidPathEntry(Path p, String context, boolean isModulePath) {
            if (!Files.exists(p)) {
                msg("jshell.err.file.not.found", context, p);
                failed = true;
                return false;
            }
            if (Files.isDirectory(p)) {
                // if module-path, either an exploded module or a directory of modules
                return true;
            }

            String name = p.getFileName().toString();
            int lastDot = name.lastIndexOf(".");
            if (lastDot > 0) {
                switch (name.substring(lastDot)) {
                    case ".jar":
                        return true;
                    case ".jmod":
                        if (isModulePath) {
                            return true;
                        }
                }
            }
            msg("jshell.err.arg", context, p);
            failed = true;
            return false;
        }

        Options parse(OptionSet options) {
            addOptions(OptionKind.CLASS_PATH,
                    validPaths(options.valuesOf(argClassPath), "--class-path", false));
            addOptions(OptionKind.MODULE_PATH,
                    validPaths(options.valuesOf(argModulePath), "--module-path", true));
            addOptions(OptionKind.ADD_MODULES, options.valuesOf(argAddModules));
            addOptions(OptionKind.ADD_EXPORTS, options.valuesOf(argAddExports).stream()
                    .map(mp -> mp.contains("=") ? mp : mp + "=ALL-UNNAMED")
                    .collect(toList())
            );

            return failed ? null : opts;
        }

        void addOptions(OptionKind kind, Collection<String> vals) {
            if (!vals.isEmpty()) {
                if (kind.onlyOne && vals.size() > 1) {
                    msg("jshell.err.opt.one", kind.optionFlag);
                    failed = true;
                    return;
                }
                if (kind.passFlag) {
                    vals = vals.stream()
                            .flatMap(mp -> Stream.of(kind.optionFlag, mp))
                            .collect(toList());
                }
                opts.addAll(kind, vals);
            }
        }
    }

    // option parsing for /reload (adds -restore -quiet)
    private class OptionParserReload extends OptionParserBase {

        private final OptionSpecBuilder argRestore = parser.accepts("restore");
        private final OptionSpecBuilder argQuiet   = parser.accepts("quiet");

        private boolean restore = false;
        private boolean quiet = false;

        boolean restore() {
            return restore;
        }

        boolean quiet() {
            return quiet;
        }

        @Override
        Options parse(OptionSet options) {
            if (options.has(argRestore)) {
                restore = true;
            }
            if (options.has(argQuiet)) {
                quiet = true;
            }
            return super.parse(options);
        }
    }

    // option parsing for command-line
    private class OptionParserCommandLine extends OptionParserBase {

        private final OptionSpec<String> argStart = parser.accepts("startup").withRequiredArg();
        private final OptionSpecBuilder argNoStart = parser.acceptsAll(asList("n", "no-startup"));
        private final OptionSpec<String> argFeedback = parser.accepts("feedback").withRequiredArg();
        private final OptionSpec<String> argExecution = parser.accepts("execution").withRequiredArg();
        private final OptionSpecBuilder argQ = parser.accepts("q");
        private final OptionSpecBuilder argS = parser.accepts("s");
        private final OptionSpecBuilder argV = parser.accepts("v");
        private final OptionSpec<String> argR = parser.accepts("R").withRequiredArg();
        private final OptionSpec<String> argC = parser.accepts("C").withRequiredArg();
        private final OptionSpecBuilder argHelp = parser.acceptsAll(asList("h", "help"));
        private final OptionSpecBuilder argVersion = parser.accepts("version");
        private final OptionSpecBuilder argFullVersion = parser.accepts("full-version");
        private final OptionSpecBuilder argShowVersion = parser.accepts("show-version");
        private final OptionSpecBuilder argHelpExtra = parser.acceptsAll(asList("X", "help-extra"));

        private String feedbackMode = null;
        private Startup initialStartup = null;

        String feedbackMode() {
            return feedbackMode;
        }

        Startup startup() {
            return initialStartup;
        }

        @Override
        void msg(String key, Object... args) {
            startmsg(key, args);
        }

        @Override
        Options parse(OptionSet options) {
            if (options.has(argHelp)) {
                printUsage();
                return null;
            }
            if (options.has(argHelpExtra)) {
                printUsageX();
                return null;
            }
            if (options.has(argVersion)) {
                cmdout.printf("jshell %s\n", version());
                return null;
            }
            if (options.has(argFullVersion)) {
                cmdout.printf("jshell %s\n", fullVersion());
                return null;
            }
            if (options.has(argShowVersion)) {
                cmdout.printf("jshell %s\n", version());
            }
            if ((options.valuesOf(argFeedback).size() +
                    (options.has(argQ) ? 1 : 0) +
                    (options.has(argS) ? 1 : 0) +
                    (options.has(argV) ? 1 : 0)) > 1) {
                msg("jshell.err.opt.feedback.one");
                return null;
            } else if (options.has(argFeedback)) {
                feedbackMode = options.valueOf(argFeedback);
            } else if (options.has("q")) {
                feedbackMode = "concise";
            } else if (options.has("s")) {
                feedbackMode = "silent";
            } else if (options.has("v")) {
                feedbackMode = "verbose";
            }
            if (options.has(argStart)) {
                List<String> sts = options.valuesOf(argStart);
                if (options.has("no-startup")) {
                    startmsg("jshell.err.opt.startup.conflict");
                    return null;
                }
                initialStartup = Startup.fromFileList(sts, "--startup", new InitMessageHandler());
                if (initialStartup == null) {
                    return null;
                }
            } else if (options.has(argNoStart)) {
                initialStartup = Startup.noStartup();
            } else {
                String packedStartup = prefs.get(STARTUP_KEY);
                initialStartup = Startup.unpack(packedStartup, new InitMessageHandler());
            }
            if (options.has(argExecution)) {
                executionControlSpec = options.valueOf(argExecution);
            }
            addOptions(OptionKind.TO_REMOTE_VM, options.valuesOf(argR));
            addOptions(OptionKind.TO_COMPILER, options.valuesOf(argC));
            return super.parse(options);
        }
    }

    /**
     * Encapsulate a history of snippets and commands which can be replayed.
     */
    private static class ReplayableHistory {

        // the history
        private List<String> hist;

        // the length of the history as of last save
        private int lastSaved;

        private ReplayableHistory(List<String> hist) {
            this.hist = hist;
            this.lastSaved = 0;
        }

        // factory for empty histories
        static ReplayableHistory emptyHistory() {
            return new ReplayableHistory(new ArrayList<>());
        }

        // factory for history stored in persistent storage
        static ReplayableHistory fromPrevious(PersistentStorage prefs) {
            // Read replay history from last jshell session
            String prevReplay = prefs.get(REPLAY_RESTORE_KEY);
            if (prevReplay == null) {
                return null;
            } else {
                return new ReplayableHistory(Arrays.asList(prevReplay.split(RECORD_SEPARATOR)));
            }

        }

        // store the history in persistent storage
        void storeHistory(PersistentStorage prefs) {
            if (hist.size() > lastSaved) {
                // Prevent history overflow by calculating what will fit, starting
                // with most recent
                int sepLen = RECORD_SEPARATOR.length();
                int length = 0;
                int first = hist.size();
                while (length < Preferences.MAX_VALUE_LENGTH && --first >= 0) {
                    length += hist.get(first).length() + sepLen;
                }
                if (first >= 0) {
                    hist = hist.subList(first + 1, hist.size());
                }
                String shist = String.join(RECORD_SEPARATOR, hist);
                prefs.put(REPLAY_RESTORE_KEY, shist);
                markSaved();
            }
            prefs.flush();
        }

        // add a snippet or command to the history
        void add(String s) {
            hist.add(s);
        }

        // return history to reloaded
        Iterable<String> iterable() {
            return hist;
        }

        // mark that persistent storage and current history are in sync
        void markSaved() {
            lastSaved = hist.size();
        }
    }

    /**
     * Is the input/output currently interactive
     *
     * @return true if console
     */
    boolean interactive() {
        return input != null && input.interactiveOutput();
    }

    void debug(String format, Object... args) {
        if (debug) {
            cmderr.printf(format + "\n", args);
        }
    }

    /**
     * Base output for command output -- no pre- or post-fix
     *
     * @param printf format
     * @param printf args
     */
    void rawout(String format, Object... args) {
        cmdout.printf(format, args);
    }

    /**
     * Must show command output
     *
     * @param format printf format
     * @param args printf args
     */
    @Override
    public void hard(String format, Object... args) {
        rawout(prefix(format), args);
    }

    /**
     * Error command output
     *
     * @param format printf format
     * @param args printf args
     */
    void error(String format, Object... args) {
        rawout(prefixError(format), args);
    }

    /**
     * Should optional informative be displayed?
     * @return true if they should be displayed
     */
    @Override
    public boolean showFluff() {
        return feedback.shouldDisplayCommandFluff() && interactive();
    }

    /**
     * Optional output
     *
     * @param format printf format
     * @param args printf args
     */
    @Override
    public void fluff(String format, Object... args) {
        if (showFluff()) {
            hard(format, args);
        }
    }

    /**
     * Resource bundle look-up
     *
     * @param key the resource key
     */
    String getResourceString(String key) {
        if (outputRB == null) {
            try {
                outputRB = ResourceBundle.getBundle(L10N_RB_NAME, locale);
            } catch (MissingResourceException mre) {
                error("Cannot find ResourceBundle: %s for locale: %s", L10N_RB_NAME, locale);
                return "";
            }
        }
        String s;
        try {
            s = outputRB.getString(key);
        } catch (MissingResourceException mre) {
            error("Missing resource: %s in %s", key, L10N_RB_NAME);
            return "";
        }
        return s;
    }

    /**
     * Add normal prefixing/postfixing to embedded newlines in a string,
     * bracketing with normal prefix/postfix
     *
     * @param s the string to prefix
     * @return the pre/post-fixed and bracketed string
     */
    String prefix(String s) {
         return prefix(s, feedback.getPre(), feedback.getPost());
    }

    /**
     * Add error prefixing/postfixing to embedded newlines in a string,
     * bracketing with error prefix/postfix
     *
     * @param s the string to prefix
     * @return the pre/post-fixed and bracketed string
     */
    String prefixError(String s) {
         return prefix(s, feedback.getErrorPre(), feedback.getErrorPost());
    }

    /**
     * Add prefixing/postfixing to embedded newlines in a string,
     * bracketing with prefix/postfix
     *
     * @param s the string to prefix
     * @param pre the string to prepend to each line
     * @param post the string to append to each line (replacing newline)
     * @return the pre/post-fixed and bracketed string
     */
    String prefix(String s, String pre, String post) {
        if (s == null) {
            return "";
        }
        String pp = s.replaceAll("\\R", post + pre);
        if (pp.endsWith(post + pre)) {
            // prevent an extra prefix char and blank line when the string
            // already terminates with newline
            pp = pp.substring(0, pp.length() - (post + pre).length());
        }
        return pre + pp + post;
    }

    /**
     * Print using resource bundle look-up and adding prefix and postfix
     *
     * @param key the resource key
     */
    void hardrb(String key) {
        hard(getResourceString(key));
    }

    /**
     * Format using resource bundle look-up using MessageFormat
     *
     * @param key the resource key
     * @param args
     */
    String messageFormat(String key, Object... args) {
        String rs = getResourceString(key);
        return MessageFormat.format(rs, args);
    }

    /**
     * Print using resource bundle look-up, MessageFormat, and add prefix and
     * postfix
     *
     * @param key the resource key
     * @param args
     */
    @Override
    public void hardmsg(String key, Object... args) {
        hard(messageFormat(key, args));
    }

    /**
     * Print error using resource bundle look-up, MessageFormat, and add prefix
     * and postfix
     *
     * @param key the resource key
     * @param args
     */
    @Override
    public void errormsg(String key, Object... args) {
        if (isRunningInteractive()) {
            rawout(prefixError(messageFormat(key, args)));
        } else {
            startmsg(key, args);
        }
    }

    /**
     * Print command-line error using resource bundle look-up, MessageFormat
     *
     * @param key the resource key
     * @param args
     */
    void startmsg(String key, Object... args) {
        cmderr.println(messageFormat(key, args));
    }

    /**
     * Print (fluff) using resource bundle look-up, MessageFormat, and add
     * prefix and postfix
     *
     * @param key the resource key
     * @param args
     */
    @Override
    public void fluffmsg(String key, Object... args) {
        if (showFluff()) {
            hardmsg(key, args);
        }
    }

    <T> void hardPairs(Stream<T> stream, Function<T, String> a, Function<T, String> b) {
        Map<String, String> a2b = stream.collect(toMap(a, b,
                (m1, m2) -> m1,
                LinkedHashMap::new));
        for (Entry<String, String> e : a2b.entrySet()) {
            hard("%s", e.getKey());
            rawout(prefix(e.getValue(), feedback.getPre() + "\t", feedback.getPost()));
        }
    }

    /**
     * Trim whitespace off end of string
     *
     * @param s
     * @return
     */
    static String trimEnd(String s) {
        int last = s.length() - 1;
        int i = last;
        while (i >= 0 && Character.isWhitespace(s.charAt(i))) {
            --i;
        }
        if (i != last) {
            return s.substring(0, i + 1);
        } else {
            return s;
        }
    }

    /**
     * The entry point into the JShell tool.
     *
     * @param args the command-line arguments
     * @throws Exception catastrophic fatal exception
     */
    public void start(String[] args) throws Exception {
        OptionParserCommandLine commandLineArgs = new OptionParserCommandLine();
        options = commandLineArgs.parse(args);
        if (options == null) {
            // Abort
            return;
        }
        startup = commandLineArgs.startup();
        // initialize editor settings
        configEditor();
        // initialize JShell instance
        resetState();
        // Read replay history from last jshell session into previous history
        replayableHistoryPrevious = ReplayableHistory.fromPrevious(prefs);
        // load snippet/command files given on command-line
        for (String loadFile : commandLineArgs.nonOptions()) {
            runFile(loadFile, "jshell");
        }
        // if we survived that...
        if (regenerateOnDeath) {
            // initialize the predefined feedback modes
            initFeedback(commandLineArgs.feedbackMode());
        }
        // check again, as feedback setting could have failed
        if (regenerateOnDeath) {
            // if we haven't died, and the feedback mode wants fluff, print welcome
            if (feedback.shouldDisplayCommandFluff()) {
                hardmsg("jshell.msg.welcome", version());
            }
            // Be sure history is always saved so that user code isn't lost
            Thread shutdownHook = new Thread() {
                @Override
                public void run() {
                    replayableHistory.storeHistory(prefs);
                }
            };
            Runtime.getRuntime().addShutdownHook(shutdownHook);
            // execute from user input
            try (IOContext in = new ConsoleIOContext(this, cmdin, console)) {
                while (regenerateOnDeath) {
                    if (!live) {
                        resetState();
                    }
                    run(in);
                }
            } finally {
                replayableHistory.storeHistory(prefs);
                closeState();
                try {
                    Runtime.getRuntime().removeShutdownHook(shutdownHook);
                } catch (Exception ex) {
                    // ignore, this probably caused by VM aready being shutdown
                    // and this is the last act anyhow
                }
            }
        }
        closeState();
    }

    private EditorSetting configEditor() {
        // Read retained editor setting (if any)
        editor = EditorSetting.fromPrefs(prefs);
        if (editor != null) {
            return editor;
        }
        // Try getting editor setting from OS environment variables
        for (String envvar : EDITOR_ENV_VARS) {
            String v = envvars.get(envvar);
            if (v != null) {
                return editor = new EditorSetting(v.split("\\s+"), false);
            }
        }
        // Default to the built-in editor
        return editor = BUILT_IN_EDITOR;
    }

    private void printUsage() {
        cmdout.print(getResourceString("help.usage"));
    }

    private void printUsageX() {
        cmdout.print(getResourceString("help.usage.x"));
    }

    /**
     * Message handler to use during initial start-up.
     */
    private class InitMessageHandler implements MessageHandler {

        @Override
        public void fluff(String format, Object... args) {
            //ignore
        }

        @Override
        public void fluffmsg(String messageKey, Object... args) {
            //ignore
        }

        @Override
        public void hard(String format, Object... args) {
            //ignore
        }

        @Override
        public void hardmsg(String messageKey, Object... args) {
            //ignore
        }

        @Override
        public void errormsg(String messageKey, Object... args) {
            startmsg(messageKey, args);
        }

        @Override
        public boolean showFluff() {
            return false;
        }
    }

    private void resetState() {
        closeState();

        // Initialize tool id mapping
        mainNamespace = new NameSpace("main", "");
        startNamespace = new NameSpace("start", "s");
        errorNamespace = new NameSpace("error", "e");
        mapSnippet = new LinkedHashMap<>();
        currentNameSpace = startNamespace;

        // Reset the replayable history, saving the old for restore
        replayableHistoryPrevious = replayableHistory;
        replayableHistory = ReplayableHistory.emptyHistory();
        JShell.Builder builder =
               JShell.builder()
                .in(userin)
                .out(userout)
                .err(usererr)
                .tempVariableNameGenerator(() -> "$" + currentNameSpace.tidNext())
                .idGenerator((sn, i) -> (currentNameSpace == startNamespace || state.status(sn).isActive())
                        ? currentNameSpace.tid(sn)
                        : errorNamespace.tid(sn))
                .remoteVMOptions(options.remoteVmOptions())
                .compilerOptions(options.compilerOptions());
        if (executionControlSpec != null) {
            builder.executionEngine(executionControlSpec);
        }
        state = builder.build();
        shutdownSubscription = state.onShutdown((JShell deadState) -> {
            if (deadState == state) {
                hardmsg("jshell.msg.terminated");
                live = false;
            }
        });
        analysis = state.sourceCodeAnalysis();
        live = true;

        // Run the start-up script.
        // Avoid an infinite loop running start-up while running start-up.
        // This could, otherwise, occur when /env /reset or /reload commands are
        // in the start-up script.
        if (!isCurrentlyRunningStartup) {
            try {
                isCurrentlyRunningStartup = true;
                startUpRun(startup.toString());
            } finally {
                isCurrentlyRunningStartup = false;
            }
        }
        // Record subsequent snippets in the main namespace.
        currentNameSpace = mainNamespace;
    }

    private boolean isRunningInteractive() {
        return currentNameSpace != null && currentNameSpace == mainNamespace;
    }

    //where -- one-time per run initialization of feedback modes
    private void initFeedback(String initMode) {
        // No fluff, no prefix, for init failures
        MessageHandler initmh = new InitMessageHandler();
        // Execute the feedback initialization code in the resource file
        startUpRun(getResourceString("startup.feedback"));
        // These predefined modes are read-only
        feedback.markModesReadOnly();
        // Restore user defined modes retained on previous run with /set mode -retain
        String encoded = prefs.get(MODE_KEY);
        if (encoded != null && !encoded.isEmpty()) {
            if (!feedback.restoreEncodedModes(initmh, encoded)) {
                // Catastrophic corruption -- remove the retained modes
                prefs.remove(MODE_KEY);
            }
        }
        if (initMode != null) {
            // The feedback mode to use was specified on the command line, use it
            if (!setFeedback(initmh, new ArgTokenizer("--feedback", initMode))) {
                regenerateOnDeath = false;
            }
        } else {
            String fb = prefs.get(FEEDBACK_KEY);
            if (fb != null) {
                // Restore the feedback mode to use that was retained
                // on a previous run with /set feedback -retain
                setFeedback(initmh, new ArgTokenizer("previous retain feedback", "-retain " + fb));
            }
        }
    }

    //where
    private void startUpRun(String start) {
        try (IOContext suin = new ScannerIOContext(new StringReader(start))) {
            run(suin);
        } catch (Exception ex) {
            hardmsg("jshell.err.startup.unexpected.exception", ex);
            ex.printStackTrace(cmdout);
        }
    }

    private void closeState() {
        live = false;
        JShell oldState = state;
        if (oldState != null) {
            state = null;
            analysis = null;
            oldState.unsubscribe(shutdownSubscription); // No notification
            oldState.close();
        }
    }

    /**
     * Main loop
     * @param in the line input/editing context
     */
    private void run(IOContext in) {
        IOContext oldInput = input;
        input = in;
        try {
            String incomplete = "";
            while (live) {
                String prompt;
                if (isRunningInteractive()) {
                    prompt = testPrompt
                                    ? incomplete.isEmpty()
                                            ? "\u0005" //ENQ
                                            : "\u0006" //ACK
                                    : incomplete.isEmpty()
                                            ? feedback.getPrompt(currentNameSpace.tidNext())
                                            : feedback.getContinuationPrompt(currentNameSpace.tidNext())
                    ;
                } else {
                    prompt = "";
                }
                String raw;
                try {
                    raw = in.readLine(prompt, incomplete);
                } catch (InputInterruptedException ex) {
                    //input interrupted - clearing current state
                    incomplete = "";
                    continue;
                }
                if (raw == null) {
                    //EOF
                    if (in.interactiveOutput()) {
                        // End after user ctrl-D
                        regenerateOnDeath = false;
                    }
                    break;
                }
                String trimmed = trimEnd(raw);
                if (!trimmed.isEmpty() || !incomplete.isEmpty()) {
                    String line = incomplete + trimmed;

                    // No commands in the middle of unprocessed source
                    if (incomplete.isEmpty() && line.startsWith("/") && !line.startsWith("//") && !line.startsWith("/*")) {
                        processCommand(line.trim());
                    } else {
                        incomplete = processSourceCatchingReset(line);
                    }
                }
            }
        } catch (IOException ex) {
            errormsg("jshell.err.unexpected.exception", ex);
        } finally {
            input = oldInput;
        }
    }

    private void addToReplayHistory(String s) {
        if (isRunningInteractive()) {
            replayableHistory.add(s);
        }
    }

    private String processSourceCatchingReset(String src) {
        try {
            input.beforeUserCode();
            return processSource(src);
        } catch (IllegalStateException ex) {
            hard("Resetting...");
            live = false; // Make double sure
            return "";
        } finally {
            input.afterUserCode();
        }
    }

    private void processCommand(String cmd) {
        if (cmd.startsWith("/-")) {
            try {
                //handle "/-[number]"
                cmdUseHistoryEntry(Integer.parseInt(cmd.substring(1)));
                return ;
            } catch (NumberFormatException ex) {
                //ignore
            }
        }
        String arg = "";
        int idx = cmd.indexOf(' ');
        if (idx > 0) {
            arg = cmd.substring(idx + 1).trim();
            cmd = cmd.substring(0, idx);
        }
        Command[] candidates = findCommand(cmd, c -> c.kind.isRealCommand);
        switch (candidates.length) {
            case 0:
                if (!rerunHistoryEntryById(cmd.substring(1))) {
                    errormsg("jshell.err.no.such.command.or.snippet.id", cmd);
                    fluffmsg("jshell.msg.help.for.help");
                }   break;
            case 1:
                Command command = candidates[0];
                // If comand was successful and is of a replayable kind, add it the replayable history
                if (command.run.apply(arg) && command.kind == CommandKind.REPLAY) {
                    addToReplayHistory((command.command + " " + arg).trim());
                }   break;
            default:
                errormsg("jshell.err.command.ambiguous", cmd,
                        Arrays.stream(candidates).map(c -> c.command).collect(Collectors.joining(", ")));
                fluffmsg("jshell.msg.help.for.help");
                break;
        }
    }

    private Command[] findCommand(String cmd, Predicate<Command> filter) {
        Command exact = commands.get(cmd);
        if (exact != null)
            return new Command[] {exact};

        return commands.values()
                       .stream()
                       .filter(filter)
                       .filter(command -> command.command.startsWith(cmd))
                       .toArray(Command[]::new);
    }

    static Path toPathResolvingUserHome(String pathString) {
        if (pathString.replace(File.separatorChar, '/').startsWith("~/"))
            return Paths.get(System.getProperty("user.home"), pathString.substring(2));
        else
            return Paths.get(pathString);
    }

    static final class Command {
        public final String command;
        public final String helpKey;
        public final Function<String,Boolean> run;
        public final CompletionProvider completions;
        public final CommandKind kind;

        // NORMAL Commands
        public Command(String command, Function<String,Boolean> run, CompletionProvider completions) {
            this(command, run, completions, CommandKind.NORMAL);
        }

        // Special kinds of Commands
        public Command(String command, Function<String,Boolean> run, CompletionProvider completions, CommandKind kind) {
            this(command, "help." + command.substring(1),
                    run, completions, kind);
        }

        // Documentation pseudo-commands
        public Command(String command, String helpKey, CommandKind kind) {
            this(command, helpKey,
                    arg -> { throw new IllegalStateException(); },
                    EMPTY_COMPLETION_PROVIDER,
                    kind);
        }

        public Command(String command, String helpKey, Function<String,Boolean> run, CompletionProvider completions, CommandKind kind) {
            this.command = command;
            this.helpKey = helpKey;
            this.run = run;
            this.completions = completions;
            this.kind = kind;
        }

    }

    interface CompletionProvider {
        List<Suggestion> completionSuggestions(String input, int cursor, int[] anchor);

    }

    enum CommandKind {
        NORMAL(true, true, true),
        REPLAY(true, true, true),
        HIDDEN(true, false, false),
        HELP_ONLY(false, true, false),
        HELP_SUBJECT(false, false, false);

        final boolean isRealCommand;
        final boolean showInHelp;
        final boolean shouldSuggestCompletions;
        private CommandKind(boolean isRealCommand, boolean showInHelp, boolean shouldSuggestCompletions) {
            this.isRealCommand = isRealCommand;
            this.showInHelp = showInHelp;
            this.shouldSuggestCompletions = shouldSuggestCompletions;
        }
    }

    static final class FixedCompletionProvider implements CompletionProvider {

        private final String[] alternatives;

        public FixedCompletionProvider(String... alternatives) {
            this.alternatives = alternatives;
        }

        // Add more options to an existing provider
        public FixedCompletionProvider(FixedCompletionProvider base, String... alternatives) {
            List<String> l = new ArrayList<>(Arrays.asList(base.alternatives));
            l.addAll(Arrays.asList(alternatives));
            this.alternatives = l.toArray(new String[l.size()]);
        }

        @Override
        public List<Suggestion> completionSuggestions(String input, int cursor, int[] anchor) {
            List<Suggestion> result = new ArrayList<>();

            for (String alternative : alternatives) {
                if (alternative.startsWith(input)) {
                    result.add(new ArgSuggestion(alternative));
                }
            }

            anchor[0] = 0;

            return result;
        }

    }

    static final CompletionProvider EMPTY_COMPLETION_PROVIDER = new FixedCompletionProvider();
    private static final CompletionProvider SNIPPET_HISTORY_OPTION_COMPLETION_PROVIDER = new FixedCompletionProvider("-all", "-start ", "-history");
    private static final CompletionProvider SAVE_OPTION_COMPLETION_PROVIDER = new FixedCompletionProvider("-all ", "-start ", "-history ");
    private static final CompletionProvider SNIPPET_OPTION_COMPLETION_PROVIDER = new FixedCompletionProvider("-all", "-start " );
    private static final FixedCompletionProvider COMMAND_LINE_LIKE_OPTIONS_COMPLETION_PROVIDER = new FixedCompletionProvider(
            "-class-path ", "-module-path ", "-add-modules ", "-add-exports ");
    private static final CompletionProvider RELOAD_OPTIONS_COMPLETION_PROVIDER = new FixedCompletionProvider(
            COMMAND_LINE_LIKE_OPTIONS_COMPLETION_PROVIDER,
            "-restore ", "-quiet ");
    private static final CompletionProvider SET_MODE_OPTIONS_COMPLETION_PROVIDER = new FixedCompletionProvider("-command", "-quiet", "-delete");
    private static final CompletionProvider FILE_COMPLETION_PROVIDER = fileCompletions(p -> true);
    private static final Map<String, CompletionProvider> ARG_OPTIONS = new HashMap<>();
    static {
        ARG_OPTIONS.put("-class-path", classPathCompletion());
        ARG_OPTIONS.put("-module-path", fileCompletions(Files::isDirectory));
        ARG_OPTIONS.put("-add-modules", EMPTY_COMPLETION_PROVIDER);
        ARG_OPTIONS.put("-add-exports", EMPTY_COMPLETION_PROVIDER);
    }
    private final Map<String, Command> commands = new LinkedHashMap<>();
    private void registerCommand(Command cmd) {
        commands.put(cmd.command, cmd);
    }

    private static CompletionProvider skipWordThenCompletion(CompletionProvider completionProvider) {
        return (input, cursor, anchor) -> {
            List<Suggestion> result = Collections.emptyList();

            int space = input.indexOf(' ');
            if (space != -1) {
                String rest = input.substring(space + 1);
                result = completionProvider.completionSuggestions(rest, cursor - space - 1, anchor);
                anchor[0] += space + 1;
            }

            return result;
        };
    }

    private static CompletionProvider fileCompletions(Predicate<Path> accept) {
        return (code, cursor, anchor) -> {
            int lastSlash = code.lastIndexOf('/');
            String path = code.substring(0, lastSlash + 1);
            String prefix = lastSlash != (-1) ? code.substring(lastSlash + 1) : code;
            Path current = toPathResolvingUserHome(path);
            List<Suggestion> result = new ArrayList<>();
            try (Stream<Path> dir = Files.list(current)) {
                dir.filter(f -> accept.test(f) && f.getFileName().toString().startsWith(prefix))
                   .map(f -> new ArgSuggestion(f.getFileName() + (Files.isDirectory(f) ? "/" : "")))
                   .forEach(result::add);
            } catch (IOException ex) {
                //ignore...
            }
            if (path.isEmpty()) {
                StreamSupport.stream(FileSystems.getDefault().getRootDirectories().spliterator(), false)
                             .filter(root -> Files.exists(root))
                             .filter(root -> accept.test(root) && root.toString().startsWith(prefix))
                             .map(root -> new ArgSuggestion(root.toString()))
                             .forEach(result::add);
            }
            anchor[0] = path.length();
            return result;
        };
    }

    private static CompletionProvider classPathCompletion() {
        return fileCompletions(p -> Files.isDirectory(p) ||
                                    p.getFileName().toString().endsWith(".zip") ||
                                    p.getFileName().toString().endsWith(".jar"));
    }

    // Completion based on snippet supplier
    private CompletionProvider snippetCompletion(Supplier<Stream<? extends Snippet>> snippetsSupplier) {
        return (prefix, cursor, anchor) -> {
            anchor[0] = 0;
            int space = prefix.lastIndexOf(' ');
            Set<String> prior = new HashSet<>(Arrays.asList(prefix.split(" ")));
            if (prior.contains("-all") || prior.contains("-history")) {
                return Collections.emptyList();
            }
            String argPrefix = prefix.substring(space + 1);
            return snippetsSupplier.get()
                        .filter(k -> !prior.contains(String.valueOf(k.id()))
                                && (!(k instanceof DeclarationSnippet)
                                     || !prior.contains(((DeclarationSnippet) k).name())))
                        .flatMap(k -> (k instanceof DeclarationSnippet)
                                ? Stream.of(String.valueOf(k.id()) + " ", ((DeclarationSnippet) k).name() + " ")
                                : Stream.of(String.valueOf(k.id()) + " "))
                        .filter(k -> k.startsWith(argPrefix))
                        .map(ArgSuggestion::new)
                        .collect(Collectors.toList());
        };
    }

    // Completion based on snippet supplier with -all -start (and sometimes -history) options
    private CompletionProvider snippetWithOptionCompletion(CompletionProvider optionProvider,
            Supplier<Stream<? extends Snippet>> snippetsSupplier) {
        return (code, cursor, anchor) -> {
            List<Suggestion> result = new ArrayList<>();
            int pastSpace = code.lastIndexOf(' ') + 1; // zero if no space
            if (pastSpace == 0) {
                result.addAll(optionProvider.completionSuggestions(code, cursor, anchor));
            }
            result.addAll(snippetCompletion(snippetsSupplier).completionSuggestions(code, cursor, anchor));
            anchor[0] += pastSpace;
            return result;
        };
    }

    // Completion of help, commands and subjects
    private CompletionProvider helpCompletion() {
        return (code, cursor, anchor) -> {
            List<Suggestion> result;
            int pastSpace = code.indexOf(' ') + 1; // zero if no space
            if (pastSpace == 0) {
                // initially suggest commands (with slash) and subjects,
                // however, if their subject starts without slash, include
                // commands without slash
                boolean noslash = code.length() > 0 && !code.startsWith("/");
                result = new FixedCompletionProvider(commands.values().stream()
                        .filter(cmd -> cmd.kind.showInHelp || cmd.kind == CommandKind.HELP_SUBJECT)
                        .map(c -> ((noslash && c.command.startsWith("/"))
                                ? c.command.substring(1)
                                : c.command) + " ")
                        .toArray(String[]::new))
                        .completionSuggestions(code, cursor, anchor);
            } else if (code.startsWith("/se")) {
                result = new FixedCompletionProvider(SET_SUBCOMMANDS)
                        .completionSuggestions(code.substring(pastSpace), cursor - pastSpace, anchor);
            } else {
                result = Collections.emptyList();
            }
            anchor[0] += pastSpace;
            return result;
        };
    }

    private static CompletionProvider saveCompletion() {
        return (code, cursor, anchor) -> {
            List<Suggestion> result = new ArrayList<>();
            int space = code.indexOf(' ');
            if (space == (-1)) {
                result.addAll(SAVE_OPTION_COMPLETION_PROVIDER.completionSuggestions(code, cursor, anchor));
            }
            result.addAll(FILE_COMPLETION_PROVIDER.completionSuggestions(code.substring(space + 1), cursor - space - 1, anchor));
            anchor[0] += space + 1;
            return result;
        };
    }

    // command-line-like option completion -- options with values
    private static CompletionProvider optionCompletion(CompletionProvider provider) {
        return (code, cursor, anchor) -> {
            Matcher ovm = OPTION_VALUE_PATTERN.matcher(code);
            if (ovm.matches()) {
                String flag = ovm.group("flag");
                List<CompletionProvider> ps = ARG_OPTIONS.entrySet().stream()
                        .filter(es -> es.getKey().startsWith(flag))
                        .map(es -> es.getValue())
                        .collect(toList());
                if (ps.size() == 1) {
                    int pastSpace = ovm.start("val");
                    List<Suggestion> result = ps.get(0).completionSuggestions(
                            ovm.group("val"), cursor - pastSpace, anchor);
                    anchor[0] += pastSpace;
                    return result;
                }
            }
            Matcher om = OPTION_PATTERN.matcher(code);
            if (om.matches()) {
                int pastSpace = om.start("flag");
                List<Suggestion> result = provider.completionSuggestions(
                        om.group("flag"), cursor - pastSpace, anchor);
                if (!om.group("dd").isEmpty()) {
                    result = result.stream()
                            .map(sug -> new Suggestion() {
                                @Override
                                public String continuation() {
                                    return "-" + sug.continuation();
                                }

                                @Override
                                public boolean matchesType() {
                                    return false;
                                }
                            })
                            .collect(toList());
                    --pastSpace;
                }
                anchor[0] += pastSpace;
                return result;
            }
            Matcher opp = OPTION_PRE_PATTERN.matcher(code);
            if (opp.matches()) {
                int pastSpace = opp.end();
                List<Suggestion> result = provider.completionSuggestions(
                        "", cursor - pastSpace, anchor);
                anchor[0] += pastSpace;
                return result;
            }
            return Collections.emptyList();
        };
    }

    // /reload command completion
    private static CompletionProvider reloadCompletion() {
        return optionCompletion(RELOAD_OPTIONS_COMPLETION_PROVIDER);
    }

    // /env command completion
    private static CompletionProvider envCompletion() {
        return optionCompletion(COMMAND_LINE_LIKE_OPTIONS_COMPLETION_PROVIDER);
    }

    private static CompletionProvider orMostSpecificCompletion(
            CompletionProvider left, CompletionProvider right) {
        return (code, cursor, anchor) -> {
            int[] leftAnchor = {-1};
            int[] rightAnchor = {-1};

            List<Suggestion> leftSuggestions = left.completionSuggestions(code, cursor, leftAnchor);
            List<Suggestion> rightSuggestions = right.completionSuggestions(code, cursor, rightAnchor);

            List<Suggestion> suggestions = new ArrayList<>();

            if (leftAnchor[0] >= rightAnchor[0]) {
                anchor[0] = leftAnchor[0];
                suggestions.addAll(leftSuggestions);
            }

            if (leftAnchor[0] <= rightAnchor[0]) {
                anchor[0] = rightAnchor[0];
                suggestions.addAll(rightSuggestions);
            }

            return suggestions;
        };
    }

    // Snippet lists

    Stream<Snippet> allSnippets() {
        return state.snippets();
    }

    Stream<Snippet> dropableSnippets() {
        return state.snippets()
                .filter(sn -> state.status(sn).isActive());
    }

    Stream<VarSnippet> allVarSnippets() {
        return state.snippets()
                .filter(sn -> sn.kind() == Snippet.Kind.VAR)
                .map(sn -> (VarSnippet) sn);
    }

    Stream<MethodSnippet> allMethodSnippets() {
        return state.snippets()
                .filter(sn -> sn.kind() == Snippet.Kind.METHOD)
                .map(sn -> (MethodSnippet) sn);
    }

    Stream<TypeDeclSnippet> allTypeSnippets() {
        return state.snippets()
                .filter(sn -> sn.kind() == Snippet.Kind.TYPE_DECL)
                .map(sn -> (TypeDeclSnippet) sn);
    }

    // Table of commands -- with command forms, argument kinds, helpKey message, implementation, ...

    {
        registerCommand(new Command("/list",
                this::cmdList,
                snippetWithOptionCompletion(SNIPPET_HISTORY_OPTION_COMPLETION_PROVIDER,
                        this::allSnippets)));
        registerCommand(new Command("/edit",
                this::cmdEdit,
                snippetWithOptionCompletion(SNIPPET_OPTION_COMPLETION_PROVIDER,
                        this::allSnippets)));
        registerCommand(new Command("/drop",
                this::cmdDrop,
                snippetCompletion(this::dropableSnippets),
                CommandKind.REPLAY));
        registerCommand(new Command("/save",
                this::cmdSave,
                saveCompletion()));
        registerCommand(new Command("/open",
                this::cmdOpen,
                FILE_COMPLETION_PROVIDER));
        registerCommand(new Command("/vars",
                this::cmdVars,
                snippetWithOptionCompletion(SNIPPET_OPTION_COMPLETION_PROVIDER,
                        this::allVarSnippets)));
        registerCommand(new Command("/methods",
                this::cmdMethods,
                snippetWithOptionCompletion(SNIPPET_OPTION_COMPLETION_PROVIDER,
                        this::allMethodSnippets)));
        registerCommand(new Command("/types",
                this::cmdTypes,
                snippetWithOptionCompletion(SNIPPET_OPTION_COMPLETION_PROVIDER,
                        this::allTypeSnippets)));
        registerCommand(new Command("/imports",
                arg -> cmdImports(),
                EMPTY_COMPLETION_PROVIDER));
        registerCommand(new Command("/exit",
                arg -> cmdExit(),
                EMPTY_COMPLETION_PROVIDER));
        registerCommand(new Command("/env",
                arg -> cmdEnv(arg),
                envCompletion()));
        registerCommand(new Command("/reset",
                arg -> cmdReset(arg),
                envCompletion()));
        registerCommand(new Command("/reload",
                this::cmdReload,
                reloadCompletion()));
        registerCommand(new Command("/history",
                arg -> cmdHistory(),
                EMPTY_COMPLETION_PROVIDER));
        registerCommand(new Command("/debug",
                this::cmdDebug,
                EMPTY_COMPLETION_PROVIDER,
                CommandKind.HIDDEN));
        registerCommand(new Command("/help",
                this::cmdHelp,
                helpCompletion()));
        registerCommand(new Command("/set",
                this::cmdSet,
                new ContinuousCompletionProvider(Map.of(
                        // need more completion for format for usability
                        "format", feedback.modeCompletions(),
                        "truncation", feedback.modeCompletions(),
                        "feedback", feedback.modeCompletions(),
                        "mode", skipWordThenCompletion(orMostSpecificCompletion(
                                feedback.modeCompletions(SET_MODE_OPTIONS_COMPLETION_PROVIDER),
                                SET_MODE_OPTIONS_COMPLETION_PROVIDER)),
                        "prompt", feedback.modeCompletions(),
                        "editor", fileCompletions(Files::isExecutable),
                        "start", FILE_COMPLETION_PROVIDER),
                        STARTSWITH_MATCHER)));
        registerCommand(new Command("/?",
                "help.quest",
                this::cmdHelp,
                helpCompletion(),
                CommandKind.NORMAL));
        registerCommand(new Command("/!",
                "help.bang",
                arg -> cmdUseHistoryEntry(-1),
                EMPTY_COMPLETION_PROVIDER,
                CommandKind.NORMAL));

        // Documentation pseudo-commands
        registerCommand(new Command("/<id>",
                "help.id",
                CommandKind.HELP_ONLY));
        registerCommand(new Command("/-<n>",
                "help.previous",
                CommandKind.HELP_ONLY));
        registerCommand(new Command("intro",
                "help.intro",
                CommandKind.HELP_SUBJECT));
        registerCommand(new Command("shortcuts",
                "help.shortcuts",
                CommandKind.HELP_SUBJECT));
        registerCommand(new Command("context",
                "help.context",
                CommandKind.HELP_SUBJECT));

        commandCompletions = new ContinuousCompletionProvider(
                commands.values().stream()
                        .filter(c -> c.kind.shouldSuggestCompletions)
                        .collect(toMap(c -> c.command, c -> c.completions)),
                STARTSWITH_MATCHER);
    }

    private ContinuousCompletionProvider commandCompletions;

    public List<Suggestion> commandCompletionSuggestions(String code, int cursor, int[] anchor) {
        return commandCompletions.completionSuggestions(code, cursor, anchor);
    }

    public List<String> commandDocumentation(String code, int cursor, boolean shortDescription) {
        code = code.substring(0, cursor);
        int space = code.indexOf(' ');
        String prefix = space != (-1) ? code.substring(0, space) : code;
        List<String> result = new ArrayList<>();

        List<Entry<String, Command>> toShow =
                commands.entrySet()
                        .stream()
                        .filter(e -> e.getKey().startsWith(prefix))
                        .filter(e -> e.getValue().kind.showInHelp)
                        .sorted((e1, e2) -> e1.getKey().compareTo(e2.getKey()))
                        .collect(Collectors.toList());

        if (toShow.size() == 1) {
            result.add(getResourceString(toShow.get(0).getValue().helpKey + (shortDescription ? ".summary" : "")));
        } else {
            for (Entry<String, Command> e : toShow) {
                result.add(e.getKey() + "\n" +getResourceString(e.getValue().helpKey + (shortDescription ? ".summary" : "")));
            }
        }

        return result;
    }

    // Attempt to stop currently running evaluation
    void stop() {
        state.stop();
    }

    // --- Command implementations ---

    private static final String[] SET_SUBCOMMANDS = new String[]{
        "format", "truncation", "feedback", "mode", "prompt", "editor", "start"};

    final boolean cmdSet(String arg) {
        String cmd = "/set";
        ArgTokenizer at = new ArgTokenizer(cmd, arg.trim());
        String which = subCommand(cmd, at, SET_SUBCOMMANDS);
        if (which == null) {
            return false;
        }
        switch (which) {
            case "_retain": {
                errormsg("jshell.err.setting.to.retain.must.be.specified", at.whole());
                return false;
            }
            case "_blank": {
                // show top-level settings
                new SetEditor().set();
                showSetStart();
                setFeedback(this, at); // no args so shows feedback setting
                hardmsg("jshell.msg.set.show.mode.settings");
                return true;
            }
            case "format":
                return feedback.setFormat(this, at);
            case "truncation":
                return feedback.setTruncation(this, at);
            case "feedback":
                return setFeedback(this, at);
            case "mode":
                return feedback.setMode(this, at,
                        retained -> prefs.put(MODE_KEY, retained));
            case "prompt":
                return feedback.setPrompt(this, at);
            case "editor":
                return new SetEditor(at).set();
            case "start":
                return setStart(at);
            default:
                errormsg("jshell.err.arg", cmd, at.val());
                return false;
        }
    }

    boolean setFeedback(MessageHandler messageHandler, ArgTokenizer at) {
        return feedback.setFeedback(messageHandler, at,
                fb -> prefs.put(FEEDBACK_KEY, fb));
    }

    // Find which, if any, sub-command matches.
    // Return null on error
    String subCommand(String cmd, ArgTokenizer at, String[] subs) {
        at.allowedOptions("-retain");
        String sub = at.next();
        if (sub == null) {
            // No sub-command was given
            return at.hasOption("-retain")
                    ? "_retain"
                    : "_blank";
        }
        String[] matches = Arrays.stream(subs)
                .filter(s -> s.startsWith(sub))
                .toArray(String[]::new);
        if (matches.length == 0) {
            // There are no matching sub-commands
            errormsg("jshell.err.arg", cmd, sub);
            fluffmsg("jshell.msg.use.one.of", Arrays.stream(subs)
                    .collect(Collectors.joining(", "))
            );
            return null;
        }
        if (matches.length > 1) {
            // More than one sub-command matches the initial characters provided
            errormsg("jshell.err.sub.ambiguous", cmd, sub);
            fluffmsg("jshell.msg.use.one.of", Arrays.stream(matches)
                    .collect(Collectors.joining(", "))
            );
            return null;
        }
        return matches[0];
    }

    static class EditorSetting {

        static String BUILT_IN_REP = "-default";
        static char WAIT_PREFIX = '-';
        static char NORMAL_PREFIX = '*';

        final String[] cmd;
        final boolean wait;

        EditorSetting(String[] cmd, boolean wait) {
            this.wait = wait;
            this.cmd = cmd;
        }

        // returns null if not stored in preferences
        static EditorSetting fromPrefs(PersistentStorage prefs) {
            // Read retained editor setting (if any)
            String editorString = prefs.get(EDITOR_KEY);
            if (editorString == null || editorString.isEmpty()) {
                return null;
            } else if (editorString.equals(BUILT_IN_REP)) {
                return BUILT_IN_EDITOR;
            } else {
                boolean wait = false;
                char waitMarker = editorString.charAt(0);
                if (waitMarker == WAIT_PREFIX || waitMarker == NORMAL_PREFIX) {
                    wait = waitMarker == WAIT_PREFIX;
                    editorString = editorString.substring(1);
                }
                String[] cmd = editorString.split(RECORD_SEPARATOR);
                return new EditorSetting(cmd, wait);
            }
        }

        static void removePrefs(PersistentStorage prefs) {
            prefs.remove(EDITOR_KEY);
        }

        void toPrefs(PersistentStorage prefs) {
            prefs.put(EDITOR_KEY, (this == BUILT_IN_EDITOR)
                    ? BUILT_IN_REP
                    : (wait ? WAIT_PREFIX : NORMAL_PREFIX) + String.join(RECORD_SEPARATOR, cmd));
        }

        @Override
        public boolean equals(Object o) {
            if (o instanceof EditorSetting) {
                EditorSetting ed = (EditorSetting) o;
                return Arrays.equals(cmd, ed.cmd) && wait == ed.wait;
            } else {
                return false;
            }
        }

        @Override
        public int hashCode() {
            int hash = 7;
            hash = 71 * hash + Arrays.deepHashCode(this.cmd);
            hash = 71 * hash + (this.wait ? 1 : 0);
            return hash;
        }
    }

    class SetEditor {

        private final ArgTokenizer at;
        private final String[] command;
        private final boolean hasCommand;
        private final boolean defaultOption;
        private final boolean deleteOption;
        private final boolean waitOption;
        private final boolean retainOption;
        private final int primaryOptionCount;

        SetEditor(ArgTokenizer at) {
            at.allowedOptions("-default", "-wait", "-retain", "-delete");
            String prog = at.next();
            List<String> ed = new ArrayList<>();
            while (at.val() != null) {
                ed.add(at.val());
                at.nextToken();  // so that options are not interpreted as jshell options
            }
            this.at = at;
            this.command = ed.toArray(new String[ed.size()]);
            this.hasCommand = command.length > 0;
            this.defaultOption = at.hasOption("-default");
            this.deleteOption = at.hasOption("-delete");
            this.waitOption = at.hasOption("-wait");
            this.retainOption = at.hasOption("-retain");
            this.primaryOptionCount = (hasCommand? 1 : 0) + (defaultOption? 1 : 0) + (deleteOption? 1 : 0);
        }

        SetEditor() {
            this(new ArgTokenizer("", ""));
        }

        boolean set() {
            if (!check()) {
                return false;
            }
            if (primaryOptionCount == 0 && !retainOption) {
                // No settings or -retain, so this is a query
                EditorSetting retained = EditorSetting.fromPrefs(prefs);
                if (retained != null) {
                    // retained editor is set
                    hard("/set editor -retain %s", format(retained));
                }
                if (retained == null || !retained.equals(editor)) {
                    // editor is not retained or retained is different from set
                    hard("/set editor %s", format(editor));
                }
                return true;
            }
            if (retainOption && deleteOption) {
                EditorSetting.removePrefs(prefs);
            }
            install();
            if (retainOption && !deleteOption) {
                editor.toPrefs(prefs);
                fluffmsg("jshell.msg.set.editor.retain", format(editor));
            }
            return true;
        }

        private boolean check() {
            if (!checkOptionsAndRemainingInput(at)) {
                return false;
            }
            if (primaryOptionCount > 1) {
                errormsg("jshell.err.default.option.or.program", at.whole());
                return false;
            }
            if (waitOption && !hasCommand) {
                errormsg("jshell.err.wait.applies.to.external.editor", at.whole());
                return false;
            }
            return true;
        }

        private void install() {
            if (hasCommand) {
                editor = new EditorSetting(command, waitOption);
            } else if (defaultOption) {
                editor = BUILT_IN_EDITOR;
            } else if (deleteOption) {
                configEditor();
            } else {
                return;
            }
            fluffmsg("jshell.msg.set.editor.set", format(editor));
        }

        private String format(EditorSetting ed) {
            if (ed == BUILT_IN_EDITOR) {
                return "-default";
            } else {
                Stream<String> elems = Arrays.stream(ed.cmd);
                if (ed.wait) {
                    elems = Stream.concat(Stream.of("-wait"), elems);
                }
                return elems.collect(joining(" "));
            }
        }
    }

    // The sub-command:  /set start <start-file>
    boolean setStart(ArgTokenizer at) {
        at.allowedOptions("-default", "-none", "-retain");
        List<String> fns = new ArrayList<>();
        while (at.next() != null) {
            fns.add(at.val());
        }
        if (!checkOptionsAndRemainingInput(at)) {
            return false;
        }
        boolean defaultOption = at.hasOption("-default");
        boolean noneOption = at.hasOption("-none");
        boolean retainOption = at.hasOption("-retain");
        boolean hasFile = !fns.isEmpty();

        int argCount = (defaultOption ? 1 : 0) + (noneOption ? 1 : 0) + (hasFile ? 1 : 0);
        if (argCount > 1) {
            errormsg("jshell.err.option.or.filename", at.whole());
            return false;
        }
        if (argCount == 0 && !retainOption) {
            // no options or filename, show current setting
            showSetStart();
            return true;
        }
        if (hasFile) {
            startup = Startup.fromFileList(fns, "/set start", this);
            if (startup == null) {
                return false;
            }
        } else if (defaultOption) {
            startup = Startup.defaultStartup(this);
        } else if (noneOption) {
            startup = Startup.noStartup();
        }
        if (retainOption) {
            // retain startup setting
            prefs.put(STARTUP_KEY, startup.storedForm());
        }
        return true;
    }

    // show the "/set start" settings (retained and, if different, current)
    // as commands (and file contents).  All commands first, then contents.
    void showSetStart() {
        StringBuilder sb = new StringBuilder();
        String retained = prefs.get(STARTUP_KEY);
        if (retained != null) {
            Startup retainedStart = Startup.unpack(retained, this);
            boolean currentDifferent = !startup.equals(retainedStart);
            sb.append(retainedStart.show(true));
            if (currentDifferent) {
                sb.append(startup.show(false));
            }
            sb.append(retainedStart.showDetail());
            if (currentDifferent) {
                sb.append(startup.showDetail());
            }
        } else {
            sb.append(startup.show(false));
            sb.append(startup.showDetail());
        }
        hard(sb.toString());
    }

    boolean cmdDebug(String arg) {
        if (arg.isEmpty()) {
            debug = !debug;
            InternalDebugControl.setDebugFlags(state, debug ? DBG_GEN : 0);
            fluff("Debugging %s", debug ? "on" : "off");
        } else {
            int flags = 0;
            for (char ch : arg.toCharArray()) {
                switch (ch) {
                    case '0':
                        flags = 0;
                        debug = false;
                        fluff("Debugging off");
                        break;
                    case 'r':
                        debug = true;
                        fluff("REPL tool debugging on");
                        break;
                    case 'g':
                        flags |= DBG_GEN;
                        fluff("General debugging on");
                        break;
                    case 'f':
                        flags |= DBG_FMGR;
                        fluff("File manager debugging on");
                        break;
                    case 'c':
                        flags |= DBG_COMPA;
                        fluff("Completion analysis debugging on");
                        break;
                    case 'd':
                        flags |= DBG_DEP;
                        fluff("Dependency debugging on");
                        break;
                    case 'e':
                        flags |= DBG_EVNT;
                        fluff("Event debugging on");
                        break;
                    case 'w':
                        flags |= DBG_WRAP;
                        fluff("Wrap debugging on");
                        break;
                    default:
                        hard("Unknown debugging option: %c", ch);
                        fluff("Use: 0 r g f c d e w");
                        return false;
                }
            }
            InternalDebugControl.setDebugFlags(state, flags);
        }
        return true;
    }

    private boolean cmdExit() {
        regenerateOnDeath = false;
        live = false;
        fluffmsg("jshell.msg.goodbye");
        return true;
    }

    boolean cmdHelp(String arg) {
        ArgTokenizer at = new ArgTokenizer("/help", arg);
        String subject = at.next();
        if (subject != null) {
            // check if the requested subject is a help subject or
            // a command, with or without slash
            Command[] matches = commands.values().stream()
                    .filter(c -> c.command.startsWith(subject)
                              || c.command.substring(1).startsWith(subject))
                    .toArray(Command[]::new);
            if (matches.length == 1) {
                String cmd = matches[0].command;
                if (cmd.equals("/set")) {
                    // Print the help doc for the specified sub-command
                    String which = subCommand(cmd, at, SET_SUBCOMMANDS);
                    if (which == null) {
                        return false;
                    }
                    if (!which.equals("_blank")) {
                        hardrb("help.set." + which);
                        return true;
                    }
                }
            }
            if (matches.length > 0) {
                for (Command c : matches) {
                    hard("");
                    hard("%s", c.command);
                    hard("");
                    hardrb(c.helpKey);
                }
                return true;
            } else {
                // failing everything else, check if this is the start of
                // a /set sub-command name
                String[] subs = Arrays.stream(SET_SUBCOMMANDS)
                        .filter(s -> s.startsWith(subject))
                        .toArray(String[]::new);
                if (subs.length > 0) {
                    for (String sub : subs) {
                        hardrb("help.set." + sub);
                        hard("");
                    }
                    return true;
                }
                errormsg("jshell.err.help.arg", arg);
            }
        }
        hardmsg("jshell.msg.help.begin");
        hardPairs(commands.values().stream()
                .filter(cmd -> cmd.kind.showInHelp),
                cmd -> cmd.command + " " + getResourceString(cmd.helpKey + ".args"),
                cmd -> getResourceString(cmd.helpKey + ".summary")
        );
        hardmsg("jshell.msg.help.subject");
        hardPairs(commands.values().stream()
                .filter(cmd -> cmd.kind == CommandKind.HELP_SUBJECT),
                cmd -> cmd.command,
                cmd -> getResourceString(cmd.helpKey + ".summary")
        );
        return true;
    }

    private boolean cmdHistory() {
        cmdout.println();
        for (String s : input.currentSessionHistory()) {
            // No number prefix, confusing with snippet ids
            cmdout.printf("%s\n", s);
        }
        return true;
    }

    /**
     * Avoid parameterized varargs possible heap pollution warning.
     */
    private interface SnippetPredicate<T extends Snippet> extends Predicate<T> { }

    /**
     * Apply filters to a stream until one that is non-empty is found.
     * Adapted from Stuart Marks
     *
     * @param supplier Supply the Snippet stream to filter
     * @param filters Filters to attempt
     * @return The non-empty filtered Stream, or null
     */
    @SafeVarargs
    private static <T extends Snippet> Stream<T> nonEmptyStream(Supplier<Stream<T>> supplier,
            SnippetPredicate<T>... filters) {
        for (SnippetPredicate<T> filt : filters) {
            Iterator<T> iterator = supplier.get().filter(filt).iterator();
            if (iterator.hasNext()) {
                return StreamSupport.stream(Spliterators.spliteratorUnknownSize(iterator, 0), false);
            }
        }
        return null;
    }

    private boolean inStartUp(Snippet sn) {
        return mapSnippet.get(sn).space == startNamespace;
    }

    private boolean isActive(Snippet sn) {
        return state.status(sn).isActive();
    }

    private boolean mainActive(Snippet sn) {
        return !inStartUp(sn) && isActive(sn);
    }

    private boolean matchingDeclaration(Snippet sn, String name) {
        return sn instanceof DeclarationSnippet
                && ((DeclarationSnippet) sn).name().equals(name);
    }

    /**
     * Convert user arguments to a Stream of snippets referenced by those
     * arguments (or lack of arguments).
     *
     * @param snippets the base list of possible snippets
     * @param defFilter the filter to apply to the arguments if no argument
     * @param rawargs the user's argument to the command, maybe be the empty
     * string
     * @return a Stream of referenced snippets or null if no matches are found
     */
    private <T extends Snippet> Stream<T> argsOptionsToSnippets(Supplier<Stream<T>> snippetSupplier,
            Predicate<Snippet> defFilter, String rawargs, String cmd) {
        ArgTokenizer at = new ArgTokenizer(cmd, rawargs.trim());
        at.allowedOptions("-all", "-start");
        List<String> args = new ArrayList<>();
        String s;
        while ((s = at.next()) != null) {
            args.add(s);
        }
        if (!checkOptionsAndRemainingInput(at)) {
            return null;
        }
        if (at.optionCount() > 0 && args.size() > 0) {
            errormsg("jshell.err.may.not.specify.options.and.snippets", at.whole());
            return null;
        }
        if (at.optionCount() > 1) {
            errormsg("jshell.err.conflicting.options", at.whole());
            return null;
        }
        if (at.hasOption("-all")) {
            // all snippets including start-up, failed, and overwritten
            return snippetSupplier.get();
        }
        if (at.hasOption("-start")) {
            // start-up snippets
            return snippetSupplier.get()
                    .filter(this::inStartUp);
        }
        if (args.isEmpty()) {
            // Default is all active user snippets
            return snippetSupplier.get()
                    .filter(defFilter);
        }
        return argsToSnippets(snippetSupplier, args);
    }

    /**
     * Convert user arguments to a Stream of snippets referenced by those
     * arguments.
     *
     * @param snippetSupplier the base list of possible snippets
     * @param args the user's argument to the command, maybe be the empty list
     * @return a Stream of referenced snippets or null if no matches to specific
     * arg
     */
    private <T extends Snippet> Stream<T> argsToSnippets(Supplier<Stream<T>> snippetSupplier,
            List<String> args) {
        Stream<T> result = null;
        for (String arg : args) {
            // Find the best match
            Stream<T> st = layeredSnippetSearch(snippetSupplier, arg);
            if (st == null) {
                Stream<Snippet> est = layeredSnippetSearch(state::snippets, arg);
                if (est == null) {
                    errormsg("jshell.err.no.such.snippets", arg);
                } else {
                    errormsg("jshell.err.the.snippet.cannot.be.used.with.this.command",
                            arg, est.findFirst().get().source());
                }
                return null;
            }
            if (result == null) {
                result = st;
            } else {
                result = Stream.concat(result, st);
            }
        }
        return result;
    }

    private <T extends Snippet> Stream<T> layeredSnippetSearch(Supplier<Stream<T>> snippetSupplier, String arg) {
        return nonEmptyStream(
                // the stream supplier
                snippetSupplier,
                // look for active user declarations matching the name
                sn -> isActive(sn) && matchingDeclaration(sn, arg),
                // else, look for any declarations matching the name
                sn -> matchingDeclaration(sn, arg),
                // else, look for an id of this name
                sn -> sn.id().equals(arg)
        );
    }

    private boolean cmdDrop(String rawargs) {
        ArgTokenizer at = new ArgTokenizer("/drop", rawargs.trim());
        at.allowedOptions();
        List<String> args = new ArrayList<>();
        String s;
        while ((s = at.next()) != null) {
            args.add(s);
        }
        if (!checkOptionsAndRemainingInput(at)) {
            return false;
        }
        if (args.isEmpty()) {
            errormsg("jshell.err.drop.arg");
            return false;
        }
        Stream<Snippet> stream = argsToSnippets(this::dropableSnippets, args);
        if (stream == null) {
            // Snippet not found. Error already printed
            fluffmsg("jshell.msg.see.classes.etc");
            return false;
        }
        List<Snippet> snippets = stream.collect(toList());
        if (snippets.size() > args.size()) {
            // One of the args references more thean one snippet
            errormsg("jshell.err.drop.ambiguous");
            fluffmsg("jshell.msg.use.one.of", snippets.stream()
                    .map(sn -> String.format("\n/drop %-5s :   %s", sn.id(), sn.source().replace("\n", "\n       ")))
                    .collect(Collectors.joining(", "))
            );
            return false;
        }
        snippets.stream()
                .forEach(sn -> state.drop(sn).forEach(this::handleEvent));
        return true;
    }

    private boolean cmdEdit(String arg) {
        Stream<Snippet> stream = argsOptionsToSnippets(state::snippets,
                this::mainActive, arg, "/edit");
        if (stream == null) {
            return false;
        }
        Set<String> srcSet = new LinkedHashSet<>();
        stream.forEachOrdered(sn -> {
            String src = sn.source();
            switch (sn.subKind()) {
                case VAR_VALUE_SUBKIND:
                    break;
                case ASSIGNMENT_SUBKIND:
                case OTHER_EXPRESSION_SUBKIND:
                case TEMP_VAR_EXPRESSION_SUBKIND:
                case UNKNOWN_SUBKIND:
                    if (!src.endsWith(";")) {
                        src = src + ";";
                    }
                    srcSet.add(src);
                    break;
                case STATEMENT_SUBKIND:
                    if (src.endsWith("}")) {
                        // Could end with block or, for example, new Foo() {...}
                        // so, we need deeper analysis to know if it needs a semicolon
                        src = analysis.analyzeCompletion(src).source();
                    } else if (!src.endsWith(";")) {
                        src = src + ";";
                    }
                    srcSet.add(src);
                    break;
                default:
                    srcSet.add(src);
                    break;
            }
        });
        StringBuilder sb = new StringBuilder();
        for (String s : srcSet) {
            sb.append(s);
            sb.append('\n');
        }
        String src = sb.toString();
        Consumer<String> saveHandler = new SaveHandler(src, srcSet);
        Consumer<String> errorHandler = s -> hard("Edit Error: %s", s);
        if (editor == BUILT_IN_EDITOR) {
            return builtInEdit(src, saveHandler, errorHandler);
        } else {
            // Changes have occurred in temp edit directory,
            // transfer the new sources to JShell (unless the editor is
            // running directly in JShell's window -- don't make a mess)
            String[] buffer = new String[1];
            Consumer<String> extSaveHandler = s -> {
                if (input.terminalEditorRunning()) {
                    buffer[0] = s;
                } else {
                    saveHandler.accept(s);
                }
            };
            ExternalEditor.edit(editor.cmd, src,
                    errorHandler, extSaveHandler,
                    () -> input.suspend(),
                    () -> input.resume(),
                    editor.wait,
                    () -> hardrb("jshell.msg.press.return.to.leave.edit.mode"));
            if (buffer[0] != null) {
                saveHandler.accept(buffer[0]);
            }
        }
        return true;
    }
    //where
    // start the built-in editor
    private boolean builtInEdit(String initialText,
            Consumer<String> saveHandler, Consumer<String> errorHandler) {
        try {
            ServiceLoader<BuildInEditorProvider> sl
                    = ServiceLoader.load(BuildInEditorProvider.class);
            // Find the highest ranking provider
            BuildInEditorProvider provider = null;
            for (BuildInEditorProvider p : sl) {
                if (provider == null || p.rank() > provider.rank()) {
                    provider = p;
                }
            }
            if (provider != null) {
                provider.edit(getResourceString("jshell.label.editpad"),
                        initialText, saveHandler, errorHandler);
                return true;
            } else {
                errormsg("jshell.err.no.builtin.editor");
            }
        } catch (RuntimeException ex) {
            errormsg("jshell.err.cant.launch.editor", ex);
        }
        fluffmsg("jshell.msg.try.set.editor");
        return false;
    }
    //where
    // receives editor requests to save
    private class SaveHandler implements Consumer<String> {

        String src;
        Set<String> currSrcs;

        SaveHandler(String src, Set<String> ss) {
            this.src = src;
            this.currSrcs = ss;
        }

        @Override
        public void accept(String s) {
            if (!s.equals(src)) { // quick check first
                src = s;
                try {
                    Set<String> nextSrcs = new LinkedHashSet<>();
                    boolean failed = false;
                    while (true) {
                        CompletionInfo an = analysis.analyzeCompletion(s);
                        if (!an.completeness().isComplete()) {
                            break;
                        }
                        String tsrc = trimNewlines(an.source());
                        if (!failed && !currSrcs.contains(tsrc)) {
                            failed = processCompleteSource(tsrc);
                        }
                        nextSrcs.add(tsrc);
                        if (an.remaining().isEmpty()) {
                            break;
                        }
                        s = an.remaining();
                    }
                    currSrcs = nextSrcs;
                } catch (IllegalStateException ex) {
                    hardmsg("jshell.msg.resetting");
                    resetState();
                    currSrcs = new LinkedHashSet<>(); // re-process everything
                }
            }
        }

        private String trimNewlines(String s) {
            int b = 0;
            while (b < s.length() && s.charAt(b) == '\n') {
                ++b;
            }
            int e = s.length() -1;
            while (e >= 0 && s.charAt(e) == '\n') {
                --e;
            }
            return s.substring(b, e + 1);
        }
    }

    private boolean cmdList(String arg) {
        if (arg.length() >= 2 && "-history".startsWith(arg)) {
            return cmdHistory();
        }
        Stream<Snippet> stream = argsOptionsToSnippets(state::snippets,
                this::mainActive, arg, "/list");
        if (stream == null) {
            return false;
        }

        // prevent double newline on empty list
        boolean[] hasOutput = new boolean[1];
        stream.forEachOrdered(sn -> {
            if (!hasOutput[0]) {
                cmdout.println();
                hasOutput[0] = true;
            }
            cmdout.printf("%4s : %s\n", sn.id(), sn.source().replace("\n", "\n       "));
        });
        return true;
    }

    private boolean cmdOpen(String filename) {
        return runFile(filename, "/open");
    }

    private boolean runFile(String filename, String context) {
        if (!filename.isEmpty()) {
            try {
                Path path = toPathResolvingUserHome(filename);
                Reader reader;
                String resource;
                if (!Files.exists(path) && (resource = getResource(filename)) != null) {
                    // Not found as file, but found as resource
                    reader = new StringReader(resource);
                } else {
                    reader = new FileReader(path.toString());
                }
                run(new ScannerIOContext(reader));
                return true;
            } catch (FileNotFoundException e) {
                errormsg("jshell.err.file.not.found", context, filename, e.getMessage());
            } catch (Exception e) {
                errormsg("jshell.err.file.exception", context, filename, e);
            }
        } else {
            errormsg("jshell.err.file.filename", context);
        }
        return false;
    }

    static String getResource(String name) {
        if (BUILTIN_FILE_PATTERN.matcher(name).matches()) {
            try {
                return readResource(name);
            } catch (Throwable t) {
                // Fall-through to null
            }
        }
        return null;
    }

    // Read a built-in file from resources
    static String readResource(String name) throws IOException {
        // Attempt to find the file as a resource
        String spec = String.format(BUILTIN_FILE_PATH_FORMAT, name);

        try (InputStream in = JShellTool.class.getResourceAsStream(spec);
                BufferedReader reader = new BufferedReader(new InputStreamReader(in))) {
            return reader.lines().collect(Collectors.joining("\n", "", "\n"));
        }
    }

    private boolean cmdReset(String rawargs) {
        if (!parseCommandLineLikeFlags(rawargs, new OptionParserBase())) {
            return false;
        }
        live = false;
        fluffmsg("jshell.msg.resetting.state");
        return true;
    }

    private boolean cmdReload(String rawargs) {
        OptionParserReload ap = new OptionParserReload();
        if (!parseCommandLineLikeFlags(rawargs, ap)) {
            return false;
        }
        ReplayableHistory history;
        if (ap.restore()) {
            if (replayableHistoryPrevious == null) {
                errormsg("jshell.err.reload.no.previous");
                return false;
            }
            history = replayableHistoryPrevious;
            fluffmsg("jshell.err.reload.restarting.previous.state");
        } else {
            history = replayableHistory;
            fluffmsg("jshell.err.reload.restarting.state");
        }
        boolean success = doReload(history, !ap.quiet());
        if (success && ap.restore()) {
            // if we are restoring from previous, then if nothing was added
            // before time of exit, there is nothing to save
            replayableHistory.markSaved();
        }
        return success;
    }

    private boolean cmdEnv(String rawargs) {
        if (rawargs.trim().isEmpty()) {
            // No arguments, display current settings (as option flags)
            StringBuilder sb = new StringBuilder();
            for (String a : options.commonOptions()) {
                sb.append(
                        a.startsWith("-")
                            ? sb.length() > 0
                                    ? "\n   "
                                    :   "   "
                            : " ");
                sb.append(a);
            }
            if (sb.length() > 0) {
                rawout(prefix(sb.toString()));
            }
            return false;
        }
        if (!parseCommandLineLikeFlags(rawargs, new OptionParserBase())) {
            return false;
        }
        fluffmsg("jshell.msg.set.restore");
        return doReload(replayableHistory, false);
    }

    private boolean doReload(ReplayableHistory history, boolean echo) {
        resetState();
        run(new ReloadIOContext(history.iterable(),
                echo ? cmdout : null));
        return true;
    }

    private boolean parseCommandLineLikeFlags(String rawargs, OptionParserBase ap) {
        String[] args = Arrays.stream(rawargs.split("\\s+"))
                .filter(s -> !s.isEmpty())
                .toArray(String[]::new);
        Options opts = ap.parse(args);
        if (opts == null) {
            return false;
        }
        if (!ap.nonOptions().isEmpty()) {
            errormsg("jshell.err.unexpected.at.end", ap.nonOptions(), rawargs);
            return false;
        }
        options.override(opts);
        return true;
    }

    private boolean cmdSave(String rawargs) {
        ArgTokenizer at = new ArgTokenizer("/save", rawargs.trim());
        at.allowedOptions("-all", "-start", "-history");
        String filename = at.next();
        if (filename == null) {
            errormsg("jshell.err.file.filename", "/save");
            return false;
        }
        if (!checkOptionsAndRemainingInput(at)) {
            return false;
        }
        if (at.optionCount() > 1) {
            errormsg("jshell.err.conflicting.options", at.whole());
            return false;
        }
        try (BufferedWriter writer = Files.newBufferedWriter(toPathResolvingUserHome(filename),
                Charset.defaultCharset(),
                CREATE, TRUNCATE_EXISTING, WRITE)) {
            if (at.hasOption("-history")) {
                for (String s : input.currentSessionHistory()) {
                    writer.write(s);
                    writer.write("\n");
                }
            } else if (at.hasOption("-start")) {
                writer.append(startup.toString());
            } else {
                String sources = (at.hasOption("-all")
                        ? state.snippets()
                        : state.snippets().filter(this::mainActive))
                        .map(Snippet::source)
                        .collect(Collectors.joining("\n"));
                writer.write(sources);
            }
        } catch (FileNotFoundException e) {
            errormsg("jshell.err.file.not.found", "/save", filename, e.getMessage());
            return false;
        } catch (Exception e) {
            errormsg("jshell.err.file.exception", "/save", filename, e);
            return false;
        }
        return true;
    }

    private boolean cmdVars(String arg) {
        Stream<VarSnippet> stream = argsOptionsToSnippets(this::allVarSnippets,
                this::isActive, arg, "/vars");
        if (stream == null) {
            return false;
        }
        stream.forEachOrdered(vk ->
        {
            String val = state.status(vk) == Status.VALID
                    ? feedback.truncateVarValue(state.varValue(vk))
                    : getResourceString("jshell.msg.vars.not.active");
            hard("  %s %s = %s", vk.typeName(), vk.name(), val);
        });
        return true;
    }

    private boolean cmdMethods(String arg) {
        Stream<MethodSnippet> stream = argsOptionsToSnippets(this::allMethodSnippets,
                this::isActive, arg, "/methods");
        if (stream == null) {
            return false;
        }
        stream.forEachOrdered(meth -> {
            String sig = meth.signature();
            int i = sig.lastIndexOf(")") + 1;
            if (i <= 0) {
                hard("  %s", meth.name());
            } else {
                hard("  %s %s%s", sig.substring(i), meth.name(), sig.substring(0, i));
            }
            printSnippetStatus(meth, true);
        });
        return true;
    }

    private boolean cmdTypes(String arg) {
        Stream<TypeDeclSnippet> stream = argsOptionsToSnippets(this::allTypeSnippets,
                this::isActive, arg, "/types");
        if (stream == null) {
            return false;
        }
        stream.forEachOrdered(ck
        -> {
            String kind;
            switch (ck.subKind()) {
                case INTERFACE_SUBKIND:
                    kind = "interface";
                    break;
                case CLASS_SUBKIND:
                    kind = "class";
                    break;
                case ENUM_SUBKIND:
                    kind = "enum";
                    break;
                case ANNOTATION_TYPE_SUBKIND:
                    kind = "@interface";
                    break;
                default:
                    assert false : "Wrong kind" + ck.subKind();
                    kind = "class";
                    break;
            }
            hard("  %s %s", kind, ck.name());
            printSnippetStatus(ck, true);
        });
        return true;
    }

    private boolean cmdImports() {
        state.imports().forEach(ik -> {
            hard("  import %s%s", ik.isStatic() ? "static " : "", ik.fullname());
        });
        return true;
    }

    private boolean cmdUseHistoryEntry(int index) {
        List<Snippet> keys = state.snippets().collect(toList());
        if (index < 0)
            index += keys.size();
        else
            index--;
        if (index >= 0 && index < keys.size()) {
            rerunSnippet(keys.get(index));
        } else {
            errormsg("jshell.err.out.of.range");
            return false;
        }
        return true;
    }

    boolean checkOptionsAndRemainingInput(ArgTokenizer at) {
        String junk = at.remainder();
        if (!junk.isEmpty()) {
            errormsg("jshell.err.unexpected.at.end", junk, at.whole());
            return false;
        } else {
            String bad = at.badOptions();
            if (!bad.isEmpty()) {
                errormsg("jshell.err.unknown.option", bad, at.whole());
                return false;
            }
        }
        return true;
    }

    private boolean rerunHistoryEntryById(String id) {
        Optional<Snippet> snippet = state.snippets()
            .filter(s -> s.id().equals(id))
            .findFirst();
        return snippet.map(s -> {
            rerunSnippet(s);
            return true;
        }).orElse(false);
    }

    private void rerunSnippet(Snippet snippet) {
        String source = snippet.source();
        cmdout.printf("%s\n", source);
        input.replaceLastHistoryEntry(source);
        processSourceCatchingReset(source);
    }

    /**
     * Filter diagnostics for only errors (no warnings, ...)
     * @param diagnostics input list
     * @return filtered list
     */
    List<Diag> errorsOnly(List<Diag> diagnostics) {
        return diagnostics.stream()
                .filter(Diag::isError)
                .collect(toList());
    }

    void displayDiagnostics(String source, Diag diag, List<String> toDisplay) {
        for (String line : diag.getMessage(null).split("\\r?\\n")) { // TODO: Internationalize
            if (!line.trim().startsWith("location:")) {
                toDisplay.add(line);
            }
        }

        int pstart = (int) diag.getStartPosition();
        int pend = (int) diag.getEndPosition();
        Matcher m = LINEBREAK.matcher(source);
        int pstartl = 0;
        int pendl = -2;
        while (m.find(pstartl)) {
            pendl = m.start();
            if (pendl >= pstart) {
                break;
            } else {
                pstartl = m.end();
            }
        }
        if (pendl < pstart) {
            pendl = source.length();
        }
        toDisplay.add(source.substring(pstartl, pendl));

        StringBuilder sb = new StringBuilder();
        int start = pstart - pstartl;
        for (int i = 0; i < start; ++i) {
            sb.append(' ');
        }
        sb.append('^');
        boolean multiline = pend > pendl;
        int end = (multiline ? pendl : pend) - pstartl - 1;
        if (end > start) {
            for (int i = start + 1; i < end; ++i) {
                sb.append('-');
            }
            if (multiline) {
                sb.append("-...");
            } else {
                sb.append('^');
            }
        }
        toDisplay.add(sb.toString());

        debug("printDiagnostics start-pos = %d ==> %d -- wrap = %s", diag.getStartPosition(), start, this);
        debug("Code: %s", diag.getCode());
        debug("Pos: %d (%d - %d)", diag.getPosition(),
                diag.getStartPosition(), diag.getEndPosition());
    }

    private String processSource(String srcInput) throws IllegalStateException {
        while (true) {
            CompletionInfo an = analysis.analyzeCompletion(srcInput);
            if (!an.completeness().isComplete()) {
                return an.remaining();
            }
            boolean failed = processCompleteSource(an.source());
            if (failed || an.remaining().isEmpty()) {
                return "";
            }
            srcInput = an.remaining();
        }
    }
    //where
    boolean processCompleteSource(String source) throws IllegalStateException {
        debug("Compiling: %s", source);
        boolean failed = false;
        boolean isActive = false;
        List<SnippetEvent> events = state.eval(source);
        for (SnippetEvent e : events) {
            // Report the event, recording failure
            failed |= handleEvent(e);

            // If any main snippet is active, this should be replayable
            // also ignore var value queries
            isActive |= e.causeSnippet() == null &&
                    e.status().isActive() &&
                    e.snippet().subKind() != VAR_VALUE_SUBKIND;
        }
        // If this is an active snippet and it didn't cause the backend to die,
        // add it to the replayable history
        if (isActive && live) {
            addToReplayHistory(source);
        }

        return failed;
    }

    // Handle incoming snippet events -- return true on failure
    private boolean handleEvent(SnippetEvent ste) {
        Snippet sn = ste.snippet();
        if (sn == null) {
            debug("Event with null key: %s", ste);
            return false;
        }
        List<Diag> diagnostics = state.diagnostics(sn).collect(toList());
        String source = sn.source();
        if (ste.causeSnippet() == null) {
            // main event
            for (Diag d : diagnostics) {
                hardmsg(d.isError()? "jshell.msg.error" : "jshell.msg.warning");
                List<String> disp = new ArrayList<>();
                displayDiagnostics(source, d, disp);
                disp.stream()
                        .forEach(l -> hard("%s", l));
            }

            if (ste.status() != Status.REJECTED) {
                if (ste.exception() != null) {
                    if (ste.exception() instanceof EvalException) {
                        printEvalException((EvalException) ste.exception());
                        return true;
                    } else if (ste.exception() instanceof UnresolvedReferenceException) {
                        printUnresolvedException((UnresolvedReferenceException) ste.exception());
                    } else {
                        hard("Unexpected execution exception: %s", ste.exception());
                        return true;
                    }
                } else {
                    new DisplayEvent(ste, FormatWhen.PRIMARY, ste.value(), diagnostics)
                            .displayDeclarationAndValue();
                }
            } else {
                if (diagnostics.isEmpty()) {
                    errormsg("jshell.err.failed");
                }
                return true;
            }
        } else {
            // Update
            if (sn instanceof DeclarationSnippet) {
                List<Diag> other = errorsOnly(diagnostics);

                // display update information
                new DisplayEvent(ste, FormatWhen.UPDATE, ste.value(), other)
                        .displayDeclarationAndValue();
            }
        }
        return false;
    }
    //where
    void printStackTrace(StackTraceElement[] stes) {
        for (StackTraceElement ste : stes) {
            StringBuilder sb = new StringBuilder();
            String cn = ste.getClassName();
            if (!cn.isEmpty()) {
                int dot = cn.lastIndexOf('.');
                if (dot > 0) {
                    sb.append(cn.substring(dot + 1));
                } else {
                    sb.append(cn);
                }
                sb.append(".");
            }
            if (!ste.getMethodName().isEmpty()) {
                sb.append(ste.getMethodName());
                sb.append(" ");
            }
            String fileName = ste.getFileName();
            int lineNumber = ste.getLineNumber();
            String loc = ste.isNativeMethod()
                    ? getResourceString("jshell.msg.native.method")
                    : fileName == null
                            ? getResourceString("jshell.msg.unknown.source")
                            : lineNumber >= 0
                                    ? fileName + ":" + lineNumber
                                    : fileName;
            hard("      at %s(%s)", sb, loc);

        }
    }
    //where
    void printUnresolvedException(UnresolvedReferenceException ex) {
        printSnippetStatus(ex.getSnippet(), false);
    }
    //where
    void printEvalException(EvalException ex) {
        if (ex.getMessage() == null) {
            hard("%s thrown", ex.getExceptionClassName());
        } else {
            hard("%s thrown: %s", ex.getExceptionClassName(), ex.getMessage());
        }
        printStackTrace(ex.getStackTrace());
    }

    private FormatAction toAction(Status status, Status previousStatus, boolean isSignatureChange) {
        FormatAction act;
        switch (status) {
            case VALID:
            case RECOVERABLE_DEFINED:
            case RECOVERABLE_NOT_DEFINED:
                if (previousStatus.isActive()) {
                    act = isSignatureChange
                            ? FormatAction.REPLACED
                            : FormatAction.MODIFIED;
                } else {
                    act = FormatAction.ADDED;
                }
                break;
            case OVERWRITTEN:
                act = FormatAction.OVERWROTE;
                break;
            case DROPPED:
                act = FormatAction.DROPPED;
                break;
            case REJECTED:
            case NONEXISTENT:
            default:
                // Should not occur
                error("Unexpected status: " + previousStatus.toString() + "=>" + status.toString());
                act = FormatAction.DROPPED;
        }
        return act;
    }

    void printSnippetStatus(DeclarationSnippet sn, boolean resolve) {
        List<Diag> otherErrors = errorsOnly(state.diagnostics(sn).collect(toList()));
        new DisplayEvent(sn, state.status(sn), resolve, otherErrors)
                .displayDeclarationAndValue();
    }

    class DisplayEvent {
        private final Snippet sn;
        private final FormatAction action;
        private final FormatWhen update;
        private final String value;
        private final List<String> errorLines;
        private final FormatResolve resolution;
        private final String unresolved;
        private final FormatUnresolved unrcnt;
        private final FormatErrors errcnt;
        private final boolean resolve;

        DisplayEvent(SnippetEvent ste, FormatWhen update, String value, List<Diag> errors) {
            this(ste.snippet(), ste.status(), false,
                    toAction(ste.status(), ste.previousStatus(), ste.isSignatureChange()),
                    update, value, errors);
        }

        DisplayEvent(Snippet sn, Status status, boolean resolve, List<Diag> errors) {
            this(sn, status, resolve, FormatAction.USED, FormatWhen.UPDATE, null, errors);
        }

        private DisplayEvent(Snippet sn, Status status, boolean resolve,
                FormatAction action, FormatWhen update, String value, List<Diag> errors) {
            this.sn = sn;
            this.resolve =resolve;
            this.action = action;
            this.update = update;
            this.value = value;
            this.errorLines = new ArrayList<>();
            for (Diag d : errors) {
                displayDiagnostics(sn.source(), d, errorLines);
            }
            if (resolve) {
                // resolve needs error lines indented
                for (int i = 0; i < errorLines.size(); ++i) {
                    errorLines.set(i, "    " + errorLines.get(i));
                }
            }
            long unresolvedCount;
            if (sn instanceof DeclarationSnippet && (status == Status.RECOVERABLE_DEFINED || status == Status.RECOVERABLE_NOT_DEFINED)) {
                resolution = (status == Status.RECOVERABLE_NOT_DEFINED)
                        ? FormatResolve.NOTDEFINED
                        : FormatResolve.DEFINED;
                unresolved = unresolved((DeclarationSnippet) sn);
                unresolvedCount = state.unresolvedDependencies((DeclarationSnippet) sn).count();
            } else {
                resolution = FormatResolve.OK;
                unresolved = "";
                unresolvedCount = 0;
            }
            unrcnt = unresolvedCount == 0
                    ? FormatUnresolved.UNRESOLVED0
                    : unresolvedCount == 1
                        ? FormatUnresolved.UNRESOLVED1
                        : FormatUnresolved.UNRESOLVED2;
            errcnt = errors.isEmpty()
                    ? FormatErrors.ERROR0
                    : errors.size() == 1
                        ? FormatErrors.ERROR1
                        : FormatErrors.ERROR2;
        }

        private String unresolved(DeclarationSnippet key) {
            List<String> unr = state.unresolvedDependencies(key).collect(toList());
            StringBuilder sb = new StringBuilder();
            int fromLast = unr.size();
            if (fromLast > 0) {
                sb.append(" ");
            }
            for (String u : unr) {
                --fromLast;
                sb.append(u);
                switch (fromLast) {
                    // No suffix
                    case 0:
                        break;
                    case 1:
                        sb.append(", and ");
                        break;
                    default:
                        sb.append(", ");
                        break;
                }
            }
            return sb.toString();
        }

        private void custom(FormatCase fcase, String name) {
            custom(fcase, name, null);
        }

        private void custom(FormatCase fcase, String name, String type) {
            if (resolve) {
                String resolutionErrors = feedback.format("resolve", fcase, action, update,
                        resolution, unrcnt, errcnt,
                        name, type, value, unresolved, errorLines);
                if (!resolutionErrors.trim().isEmpty()) {
                    hard("    %s", resolutionErrors);
                }
            } else if (interactive()) {
                String display = feedback.format(fcase, action, update,
                        resolution, unrcnt, errcnt,
                        name, type, value, unresolved, errorLines);
                cmdout.print(display);
            }
        }

        @SuppressWarnings("fallthrough")
        private void displayDeclarationAndValue() {
            switch (sn.subKind()) {
                case CLASS_SUBKIND:
                    custom(FormatCase.CLASS, ((TypeDeclSnippet) sn).name());
                    break;
                case INTERFACE_SUBKIND:
                    custom(FormatCase.INTERFACE, ((TypeDeclSnippet) sn).name());
                    break;
                case ENUM_SUBKIND:
                    custom(FormatCase.ENUM, ((TypeDeclSnippet) sn).name());
                    break;
                case ANNOTATION_TYPE_SUBKIND:
                    custom(FormatCase.ANNOTATION, ((TypeDeclSnippet) sn).name());
                    break;
                case METHOD_SUBKIND:
                    custom(FormatCase.METHOD, ((MethodSnippet) sn).name(), ((MethodSnippet) sn).parameterTypes());
                    break;
                case VAR_DECLARATION_SUBKIND: {
                    VarSnippet vk = (VarSnippet) sn;
                    custom(FormatCase.VARDECL, vk.name(), vk.typeName());
                    break;
                }
                case VAR_DECLARATION_WITH_INITIALIZER_SUBKIND: {
                    VarSnippet vk = (VarSnippet) sn;
                    custom(FormatCase.VARINIT, vk.name(), vk.typeName());
                    break;
                }
                case TEMP_VAR_EXPRESSION_SUBKIND: {
                    VarSnippet vk = (VarSnippet) sn;
                    custom(FormatCase.EXPRESSION, vk.name(), vk.typeName());
                    break;
                }
                case OTHER_EXPRESSION_SUBKIND:
                    error("Unexpected expression form -- value is: %s", (value));
                    break;
                case VAR_VALUE_SUBKIND: {
                    ExpressionSnippet ek = (ExpressionSnippet) sn;
                    custom(FormatCase.VARVALUE, ek.name(), ek.typeName());
                    break;
                }
                case ASSIGNMENT_SUBKIND: {
                    ExpressionSnippet ek = (ExpressionSnippet) sn;
                    custom(FormatCase.ASSIGNMENT, ek.name(), ek.typeName());
                    break;
                }
                case SINGLE_TYPE_IMPORT_SUBKIND:
                case TYPE_IMPORT_ON_DEMAND_SUBKIND:
                case SINGLE_STATIC_IMPORT_SUBKIND:
                case STATIC_IMPORT_ON_DEMAND_SUBKIND:
                    custom(FormatCase.IMPORT, ((ImportSnippet) sn).name());
                    break;
                case STATEMENT_SUBKIND:
                    custom(FormatCase.STATEMENT, null);
                    break;
            }
        }
    }

    /** The current version number as a string.
     */
    String version() {
        return version("release");  // mm.nn.oo[-milestone]
    }

    /** The current full version number as a string.
     */
    String fullVersion() {
        return version("full"); // mm.mm.oo[-milestone]-build
    }

    private String version(String key) {
        if (versionRB == null) {
            try {
                versionRB = ResourceBundle.getBundle(VERSION_RB_NAME, locale);
            } catch (MissingResourceException e) {
                return "(version info not available)";
            }
        }
        try {
            return versionRB.getString(key);
        }
        catch (MissingResourceException e) {
            return "(version info not available)";
        }
    }

    class NameSpace {
        final String spaceName;
        final String prefix;
        private int nextNum;

        NameSpace(String spaceName, String prefix) {
            this.spaceName = spaceName;
            this.prefix = prefix;
            this.nextNum = 1;
        }

        String tid(Snippet sn) {
            String tid = prefix + nextNum++;
            mapSnippet.put(sn, new SnippetInfo(sn, this, tid));
            return tid;
        }

        String tidNext() {
            return prefix + nextNum;
        }
    }

    static class SnippetInfo {
        final Snippet snippet;
        final NameSpace space;
        final String tid;

        SnippetInfo(Snippet snippet, NameSpace space, String tid) {
            this.snippet = snippet;
            this.space = space;
            this.tid = tid;
        }
    }

    static class ArgSuggestion implements Suggestion {

        private final String continuation;

        /**
         * Create a {@code Suggestion} instance.
         *
         * @param continuation a candidate continuation of the user's input
         */
        public ArgSuggestion(String continuation) {
            this.continuation = continuation;
        }

        /**
         * The candidate continuation of the given user's input.
         *
         * @return the continuation string
         */
        @Override
        public String continuation() {
            return continuation;
        }

        /**
         * Indicates whether input continuation matches the target type and is thus
         * more likely to be the desired continuation. A matching continuation is
         * preferred.
         *
         * @return {@code false}, non-types analysis
         */
        @Override
        public boolean matchesType() {
            return false;
        }
    }
}

abstract class NonInteractiveIOContext extends IOContext {

    @Override
    public boolean interactiveOutput() {
        return false;
    }

    @Override
    public Iterable<String> currentSessionHistory() {
        return Collections.emptyList();
    }

    @Override
    public boolean terminalEditorRunning() {
        return false;
    }

    @Override
    public void suspend() {
    }

    @Override
    public void resume() {
    }

    @Override
    public void beforeUserCode() {
    }

    @Override
    public void afterUserCode() {
    }

    @Override
    public void replaceLastHistoryEntry(String source) {
    }
}

class ScannerIOContext extends NonInteractiveIOContext {
    private final Scanner scannerIn;

    ScannerIOContext(Scanner scannerIn) {
        this.scannerIn = scannerIn;
    }

    ScannerIOContext(Reader rdr) throws FileNotFoundException {
        this(new Scanner(rdr));
    }

    @Override
    public String readLine(String prompt, String prefix) {
        if (scannerIn.hasNextLine()) {
            return scannerIn.nextLine();
        } else {
            return null;
        }
    }

    @Override
    public void close() {
        scannerIn.close();
    }

    @Override
    public int readUserInput() {
        return -1;
    }
}

class ReloadIOContext extends NonInteractiveIOContext {
    private final Iterator<String> it;
    private final PrintStream echoStream;

    ReloadIOContext(Iterable<String> history, PrintStream echoStream) {
        this.it = history.iterator();
        this.echoStream = echoStream;
    }

    @Override
    public String readLine(String prompt, String prefix) {
        String s = it.hasNext()
                ? it.next()
                : null;
        if (echoStream != null && s != null) {
            String p = "-: ";
            String p2 = "\n   ";
            echoStream.printf("%s%s\n", p, s.replace("\n", p2));
        }
        return s;
    }

    @Override
    public void close() {
    }

    @Override
    public int readUserInput() {
        return -1;
    }
}