ComboParameter.java revision 3019:176472b94f2e 
1/*
2 * Copyright (c) 2015, Oracle and/or its affiliates. All rights reserved.
3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
4 *
5 * This code is free software; you can redistribute it and/or modify it
6 * under the terms of the GNU General Public License version 2 only, as
7 * published by the Free Software Foundation.
8 *
9 * This code is distributed in the hope that it will be useful, but WITHOUT
10 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
11 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
12 * version 2 for more details (a copy is included in the LICENSE file that
13 * accompanied this code).
14 *
15 * You should have received a copy of the GNU General Public License version
16 * 2 along with this work; if not, write to the Free Software Foundation,
17 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
18 *
19 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
20 * or visit www.oracle.com if you need additional information or have any
21 * questions.
22 */
23
24package combo;
25
26import java.util.regex.Matcher;
27import java.util.regex.Pattern;
28
29/**
30 * A combo parameter represents an 'hole' in a template that can be replaced with a given string.
31 * The schema of such holes is defined in {@link ComboParameter#pattern}; the main routine for
32 * replacing holes in a template scheme is {@link ComboParameter#expandTemplate(String, Resolver)}.
33 */
34public interface ComboParameter {
35
36    /**
37     * A combo parameter can take the form:
38     * <p>
39     * #{MAJOR}
40     * #{MAJOR.}
41     * #{MAJOR.MINOR}
42     * <p>
43     * where MAJOR can be IDENTIFIER or IDENTIFIER[NUMERIC_INDEX]
44     * and MINOR can be an identifier.
45     */
46    Pattern pattern = Pattern.compile("#\\{([A-Z_][A-Z0-9_]*(?:\\[\\d+\\])?)(?:\\.([A-Z0-9_]*))?\\}");
47
48    /**
49     * Entry point for the customizable replacement logic. Subclasses must implement this method to
50     * specify how a given template hole should be expanded. An optional contextual argument is passed
51     * in as parameter, to make expansion more flexible.
52     */
53    String expand(String optParameter);
54
55    /**
56     * Helper class for defining 'constant' combo parameters - i.e. parameters that always expand
57     * as a given string value - regardless of the context.
58     */
59    class Constant<D> implements ComboParameter {
60
61        D data;
62
63        public Constant(D data) {
64            this.data = data;
65        }
66
67        @Override
68        public String expand(String _unused) {
69            return String.valueOf(data);
70        }
71    }
72
73    /**
74     * Helper interface used to lookup parameters given a parameter name.
75     */
76    interface Resolver {
77        ComboParameter lookup(String name);
78    }
79
80    /**
81     * Main routine for replacing holes in a template string. Holes are repeatedly searches, their
82     * corresponding parameters retrieved, and replaced through expansion; since an expansion can
83     * lead to more holes, the process has to be applied until a fixed point is reached.
84     */
85    static String expandTemplate(String template, Resolver resolver) {
86        CharSequence in = template;
87        StringBuffer out = new StringBuffer();
88        while (true) {
89            boolean more = false;
90            Matcher m = pattern.matcher(in);
91            while (m.find()) {
92                String parameterName = m.group(1);
93                String minor = m.group(2);
94                ComboParameter parameter = resolver.lookup(parameterName);
95                if (parameter == null) {
96                    throw new IllegalStateException("Unhandled parameter name " + parameterName);
97                }
98
99                String replacement = parameter.expand(minor);
100                more |= pattern.matcher(replacement).find();
101                m.appendReplacement(out, replacement);
102            }
103            m.appendTail(out);
104            if (!more)
105                return out.toString();
106            else {
107                in = out;
108                out = new StringBuffer();
109            }
110        }
111    }
112}
113