001/*
002 * Copyright (C) 2006 The Guava Authors
003 *
004 * Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except
005 * in compliance with the License. You may obtain a copy of the License at
006 *
007 * http://www.apache.org/licenses/LICENSE-2.0
008 *
009 * Unless required by applicable law or agreed to in writing, software distributed under the License
010 * is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express
011 * or implied. See the License for the specific language governing permissions and limitations under
012 * the License.
013 */
014
015package com.google.common.base;
016
017import static com.google.common.base.Preconditions.checkNotNull;
018
019import com.google.common.annotations.GwtCompatible;
020import java.io.Serializable;
021import org.checkerframework.checker.nullness.qual.Nullable;
022
023/**
024 * Utility class for converting between various ASCII case formats. Behavior is undefined for
025 * non-ASCII input.
026 *
027 * @author Mike Bostock
028 * @since 1.0
029 */
030@GwtCompatible
031public enum CaseFormat {
032  /** Hyphenated variable naming convention, e.g., "lower-hyphen". */
033  LOWER_HYPHEN(CharMatcher.is('-'), "-") {
034    @Override
035    String normalizeWord(String word) {
036      return Ascii.toLowerCase(word);
037    }
038
039    @Override
040    String convert(CaseFormat format, String s) {
041      if (format == LOWER_UNDERSCORE) {
042        return s.replace('-', '_');
043      }
044      if (format == UPPER_UNDERSCORE) {
045        return Ascii.toUpperCase(s.replace('-', '_'));
046      }
047      return super.convert(format, s);
048    }
049  },
050
051  /** C++ variable naming convention, e.g., "lower_underscore". */
052  LOWER_UNDERSCORE(CharMatcher.is('_'), "_") {
053    @Override
054    String normalizeWord(String word) {
055      return Ascii.toLowerCase(word);
056    }
057
058    @Override
059    String convert(CaseFormat format, String s) {
060      if (format == LOWER_HYPHEN) {
061        return s.replace('_', '-');
062      }
063      if (format == UPPER_UNDERSCORE) {
064        return Ascii.toUpperCase(s);
065      }
066      return super.convert(format, s);
067    }
068  },
069
070  /** Java variable naming convention, e.g., "lowerCamel". */
071  LOWER_CAMEL(CharMatcher.inRange('A', 'Z'), "") {
072    @Override
073    String normalizeWord(String word) {
074      return firstCharOnlyToUpper(word);
075    }
076  },
077
078  /** Java and C++ class naming convention, e.g., "UpperCamel". */
079  UPPER_CAMEL(CharMatcher.inRange('A', 'Z'), "") {
080    @Override
081    String normalizeWord(String word) {
082      return firstCharOnlyToUpper(word);
083    }
084  },
085
086  /** Java and C++ constant naming convention, e.g., "UPPER_UNDERSCORE". */
087  UPPER_UNDERSCORE(CharMatcher.is('_'), "_") {
088    @Override
089    String normalizeWord(String word) {
090      return Ascii.toUpperCase(word);
091    }
092
093    @Override
094    String convert(CaseFormat format, String s) {
095      if (format == LOWER_HYPHEN) {
096        return Ascii.toLowerCase(s.replace('_', '-'));
097      }
098      if (format == LOWER_UNDERSCORE) {
099        return Ascii.toLowerCase(s);
100      }
101      return super.convert(format, s);
102    }
103  };
104
105  private final CharMatcher wordBoundary;
106  private final String wordSeparator;
107
108  CaseFormat(CharMatcher wordBoundary, String wordSeparator) {
109    this.wordBoundary = wordBoundary;
110    this.wordSeparator = wordSeparator;
111  }
112
113  /**
114   * Converts the specified {@code String str} from this format to the specified {@code format}. A
115   * "best effort" approach is taken; if {@code str} does not conform to the assumed format, then
116   * the behavior of this method is undefined but we make a reasonable effort at converting anyway.
117   */
118  public final String to(CaseFormat format, String str) {
119    checkNotNull(format);
120    checkNotNull(str);
121    return (format == this) ? str : convert(format, str);
122  }
123
124  /** Enum values can override for performance reasons. */
125  String convert(CaseFormat format, String s) {
126    // deal with camel conversion
127    StringBuilder out = null;
128    int i = 0;
129    int j = -1;
130    while ((j = wordBoundary.indexIn(s, ++j)) != -1) {
131      if (i == 0) {
132        // include some extra space for separators
133        out = new StringBuilder(s.length() + 4 * wordSeparator.length());
134        out.append(format.normalizeFirstWord(s.substring(i, j)));
135      } else {
136        out.append(format.normalizeWord(s.substring(i, j)));
137      }
138      out.append(format.wordSeparator);
139      i = j + wordSeparator.length();
140    }
141    return (i == 0)
142        ? format.normalizeFirstWord(s)
143        : out.append(format.normalizeWord(s.substring(i))).toString();
144  }
145
146  /**
147   * Returns a {@code Converter} that converts strings from this format to {@code targetFormat}.
148   *
149   * @since 16.0
150   */
151  public Converter<String, String> converterTo(CaseFormat targetFormat) {
152    return new StringConverter(this, targetFormat);
153  }
154
155  private static final class StringConverter extends Converter<String, String>
156      implements Serializable {
157
158    private final CaseFormat sourceFormat;
159    private final CaseFormat targetFormat;
160
161    StringConverter(CaseFormat sourceFormat, CaseFormat targetFormat) {
162      this.sourceFormat = checkNotNull(sourceFormat);
163      this.targetFormat = checkNotNull(targetFormat);
164    }
165
166    @Override
167    protected String doForward(String s) {
168      return sourceFormat.to(targetFormat, s);
169    }
170
171    @Override
172    protected String doBackward(String s) {
173      return targetFormat.to(sourceFormat, s);
174    }
175
176    @Override
177    public boolean equals(@Nullable Object object) {
178      if (object instanceof StringConverter) {
179        StringConverter that = (StringConverter) object;
180        return sourceFormat.equals(that.sourceFormat) && targetFormat.equals(that.targetFormat);
181      }
182      return false;
183    }
184
185    @Override
186    public int hashCode() {
187      return sourceFormat.hashCode() ^ targetFormat.hashCode();
188    }
189
190    @Override
191    public String toString() {
192      return sourceFormat + ".converterTo(" + targetFormat + ")";
193    }
194
195    private static final long serialVersionUID = 0L;
196  }
197
198  abstract String normalizeWord(String word);
199
200  private String normalizeFirstWord(String word) {
201    return (this == LOWER_CAMEL) ? Ascii.toLowerCase(word) : normalizeWord(word);
202  }
203
204  private static String firstCharOnlyToUpper(String word) {
205    return word.isEmpty()
206        ? word
207        : Ascii.toUpperCase(word.charAt(0)) + Ascii.toLowerCase(word.substring(1));
208  }
209}