001/*
002 * Copyright (C) 2006 The Guava Authors
003 *
004 * Licensed under the Apache License, Version 2.0 (the "License");
005 * you may not use this file except in compliance with the License.
006 * You may obtain a copy of the License at
007 *
008 * http://www.apache.org/licenses/LICENSE-2.0
009 *
010 * Unless required by applicable law or agreed to in writing, software
011 * distributed under the License is distributed on an "AS IS" BASIS,
012 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
013 * See the License for the specific language governing permissions and
014 * limitations under the License.
015 */
016
017package com.google.common.base;
018
019import com.google.common.annotations.GwtCompatible;
020
021/**
022 * Utility class for converting between various ASCII case formats.
023 *
024 * @author Mike Bostock
025 * @since 1.0
026 */
027@GwtCompatible
028public enum CaseFormat {
029  /**
030   * Hyphenated variable naming convention, e.g., "lower-hyphen".
031   */
032  LOWER_HYPHEN(CharMatcher.is('-'), "-"),
033
034  /**
035   * C++ variable naming convention, e.g., "lower_underscore".
036   */
037  LOWER_UNDERSCORE(CharMatcher.is('_'), "_"),
038
039  /**
040   * Java variable naming convention, e.g., "lowerCamel".
041   */
042  LOWER_CAMEL(CharMatcher.inRange('A', 'Z'), ""),
043
044  /**
045   * Java and C++ class naming convention, e.g., "UpperCamel".
046   */
047  UPPER_CAMEL(CharMatcher.inRange('A', 'Z'), ""),
048
049  /**
050   * Java and C++ constant naming convention, e.g., "UPPER_UNDERSCORE".
051   */
052  UPPER_UNDERSCORE(CharMatcher.is('_'), "_");
053
054  private final CharMatcher wordBoundary;
055  private final String wordSeparator;
056
057  CaseFormat(CharMatcher wordBoundary, String wordSeparator) {
058    this.wordBoundary = wordBoundary;
059    this.wordSeparator = wordSeparator;
060  }
061
062  /**
063   * Converts the specified {@code String s} from this format to the specified {@code format}. A
064   * "best effort" approach is taken; if {@code s} does not conform to the assumed format, then the
065   * behavior of this method is undefined but we make a reasonable effort at converting anyway.
066   */
067  public String to(CaseFormat format, String s) {
068    if (format == null) {
069      throw new NullPointerException();
070    }
071    if (s == null) {
072      throw new NullPointerException();
073    }
074
075    if (format == this) {
076      return s;
077    }
078
079    /* optimize cases where no camel conversion is required */
080    switch (this) {
081      case LOWER_HYPHEN:
082        switch (format) {
083          case LOWER_UNDERSCORE:
084            return s.replace('-', '_');
085          case UPPER_UNDERSCORE:
086            return Ascii.toUpperCase(s.replace('-', '_'));
087        }
088        break;
089      case LOWER_UNDERSCORE:
090        switch (format) {
091          case LOWER_HYPHEN:
092            return s.replace('_', '-');
093          case UPPER_UNDERSCORE:
094            return Ascii.toUpperCase(s);
095        }
096        break;
097      case UPPER_UNDERSCORE:
098        switch (format) {
099          case LOWER_HYPHEN:
100            return Ascii.toLowerCase(s.replace('_', '-'));
101          case LOWER_UNDERSCORE:
102            return Ascii.toLowerCase(s);
103        }
104        break;
105    }
106
107    // otherwise, deal with camel conversion
108    StringBuilder out = null;
109    int i = 0;
110    int j = -1;
111    while ((j = wordBoundary.indexIn(s, ++j)) != -1) {
112      if (i == 0) {
113        // include some extra space for separators
114        out = new StringBuilder(s.length() + 4 * wordSeparator.length());
115        out.append(format.normalizeFirstWord(s.substring(i, j)));
116      } else {
117        out.append(format.normalizeWord(s.substring(i, j)));
118      }
119      out.append(format.wordSeparator);
120      i = j + wordSeparator.length();
121    }
122    if (i == 0) {
123      return format.normalizeFirstWord(s);
124    }
125    out.append(format.normalizeWord(s.substring(i)));
126    return out.toString();
127  }
128
129  private String normalizeFirstWord(String word) {
130    switch (this) {
131      case LOWER_CAMEL:
132        return Ascii.toLowerCase(word);
133      default:
134        return normalizeWord(word);
135    }
136  }
137
138  private String normalizeWord(String word) {
139    switch (this) {
140      case LOWER_HYPHEN:
141        return Ascii.toLowerCase(word);
142      case LOWER_UNDERSCORE:
143        return Ascii.toLowerCase(word);
144      case LOWER_CAMEL:
145        return firstCharOnlyToUpper(word);
146      case UPPER_CAMEL:
147        return firstCharOnlyToUpper(word);
148      case UPPER_UNDERSCORE:
149        return Ascii.toUpperCase(word);
150    }
151    throw new RuntimeException("unknown case: " + this);
152  }
153
154  private static String firstCharOnlyToUpper(String word) {
155    int length = word.length();
156    if (length == 0) {
157      return word;
158    }
159    return new StringBuilder(length)
160        .append(Ascii.toUpperCase(word.charAt(0)))
161        .append(Ascii.toLowerCase(word.substring(1)))
162        .toString();
163  }
164}