content: /*
   * Copyright 2016 Google Inc.
   *
   * Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except
   * in compliance with the License. You may obtain a copy of the License at
   *
   *     http://www.apache.org/licenses/LICENSE-2.0
   *
   * Unless required by applicable law or agreed to in writing, software distributed under the License
   * is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express
   * or implied. See the License for the specific language governing permissions and limitations under
   * the License.
   */
  
  package com.google.googlejavaformat.java.javadoc;
  
  import static com.google.common.base.Preconditions.checkArgument;
  import static com.google.common.base.Preconditions.checkNotNull;
  
  import java.util.regex.Matcher;
  import java.util.regex.Pattern;
  
  /**
   * String reader designed for use from the lexer. Callers invoke the {@link #tryConsume tryConsume*}
   * methods to specify what characters they expect and then {@link #readAndResetRecorded} to retrieve
   * and consume the matched characters. This is a slightly odd API -- why not just return the matched
   * characters from tryConsume? -- but it is convenient for the lexer.
   */
  final class CharStream {
    String remaining;
    int toConsume;
  
    CharStream(String input) {
      this.remaining = checkNotNull(input);
    }
  
    boolean tryConsume(String expected) {
      if (!remaining.startsWith(expected)) {
        return false;
      }
      toConsume = expected.length();
      return true;
    }
  
    /*
     * @param pattern the pattern to search for, which must be anchored to match only at position 0
     */
    boolean tryConsumeRegex(Pattern pattern) {
      Matcher matcher = pattern.matcher(remaining);
      if (!matcher.find()) {
        return false;
      }
      checkArgument(matcher.start() == 0);
      toConsume = matcher.end();
      return true;
    }
  
    String readAndResetRecorded() {
      String result = remaining.substring(0, toConsume);
      remaining = remaining.substring(toConsume);
      toConsume = 0; // TODO(cpovirk): Set this to a bogus value here and in the constructor.
      return result;
    }
  
    boolean isExhausted() {
      return remaining.isEmpty();
    }
  }
  