content: /*
   * Copyright (C) 2011 The Android Open Source Project
   *
   * 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 android.filterfw.io;
  
  import java.util.regex.Matcher;
  import java.util.regex.Pattern;
  
  /**
   * @hide
   */
  public class PatternScanner {
  
      private String mInput;
      private Pattern mIgnorePattern;
      private int mOffset = 0;
      private int mLineNo = 0;
      private int mStartOfLine = 0;
  
      public PatternScanner(String input) {
          mInput = input;
      }
  
      public PatternScanner(String input, Pattern ignorePattern) {
          mInput = input;
          mIgnorePattern = ignorePattern;
          skip(mIgnorePattern);
      }
  
      public String tryEat(Pattern pattern) {
          // Skip ignore pattern
          if (mIgnorePattern != null) {
              skip(mIgnorePattern);
          }
  
          // Create the matcher
          Matcher matcher = pattern.matcher(mInput);
          matcher.region(mOffset, mInput.length());
  
          // Attempt to match
          String result = null;
          if (matcher.lookingAt()) {
              updateLineCount(mOffset, matcher.end());
              mOffset = matcher.end();
              result = mInput.substring(matcher.start(), matcher.end());
          }
  
          // Skip ignore pattern
          if (result != null && mIgnorePattern != null) {
              skip(mIgnorePattern);
          }
  
          return result;
      }
  
      public String eat(Pattern pattern, String tokenName) {
          String result = tryEat(pattern);
          if (result == null) {
              throw new RuntimeException(unexpectedTokenMessage(tokenName));
          }
          return result;
      }
  
      public boolean peek(Pattern pattern) {
          // Skip ignore pattern
          if (mIgnorePattern != null) {
              skip(mIgnorePattern);
          }
  
          // Create the matcher
          Matcher matcher = pattern.matcher(mInput);
          matcher.region(mOffset, mInput.length());
  
          // Attempt to match
          return matcher.lookingAt();
      }
  
      public void skip(Pattern pattern) {
          Matcher matcher = pattern.matcher(mInput);
          matcher.region(mOffset, mInput.length());
          if (matcher.lookingAt()) {
              updateLineCount(mOffset, matcher.end());
              mOffset = matcher.end();
          }
      }
  
      public boolean atEnd() {
          return mOffset >= mInput.length();
      }
  
      public int lineNo() {
          return mLineNo;
      }
  
      public String unexpectedTokenMessage(String tokenName) {
          String line = mInput.substring(mStartOfLine, mOffset);
          return "Unexpected token on line " + (mLineNo + 1) + " after '" + line + "' <- Expected " +
                  tokenName + "!";
      }
  
      public void updateLineCount(int start, int end) {
          for (int i = start; i < end; ++i) {
              if (mInput.charAt(i) == '\n') {
                  ++mLineNo;
                  mStartOfLine = i + 1;
              }
          }
      }
  }
  