/*
    * Copyright 2006-2007 the original author or authors.
    *
    * 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 org.springframework.batch.item.file;
  
  import java.io.BufferedReader;
  import java.io.IOException;
  import java.io.InputStreamReader;
  import java.io.Reader;
  import java.io.UnsupportedEncodingException;
  
  import org.springframework.core.io.Resource;
  
  /**
   * A {@link BufferedReaderFactory} useful for reading simple binary (or text)
   * files with no line endings, such as those produced by mainframe copy books.
   * The reader splits a stream up across fixed line endings (rather than the
   * usual convention based on plain text). The line endings are discarded, just
   * as with the default plain text implementation.
   * 
   * @author Dave Syer
   * 
   * @since 2.1
   */
  public class SimpleBinaryBufferedReaderFactory implements BufferedReaderFactory {
  
  	/**
  	 * The default line ending value.
  	 */
  	private static final String DEFAULT_LINE_ENDING = "\n";
  
  	private String lineEnding = DEFAULT_LINE_ENDING;
  
  	/**
  	 * @param lineEnding
  	 */
  	public void setLineEnding(String lineEnding) {
  		this.lineEnding = lineEnding;
  	}
  
      @Override
  	public BufferedReader create(Resource resource, String encoding) throws UnsupportedEncodingException, IOException {
  		return new BinaryBufferedReader(new InputStreamReader(resource.getInputStream(), encoding), lineEnding);
  	}
  
  	/**
  	 * BufferedReader extension that splits lines based on a line ending, rather
  	 * than the usual plain text conventions.
  	 * 
  	 * @author Dave Syer
  	 * 
  	 */
  	private final class BinaryBufferedReader extends BufferedReader {
  
  		private final String ending;
  
  		/**
  		 * @param in
  		 */
  		private BinaryBufferedReader(Reader in, String ending) {
  			super(in);
  			this.ending = ending;
  		}
  
  		@Override
  		public String readLine() throws IOException {
  
  			StringBuilder buffer = null;
  
  			synchronized (lock) {
  
  				int next = read();
  				if (next == -1) {
  					return null;
  				}
  
  				buffer = new StringBuilder();
  				StringBuilder candidateEnding = new StringBuilder();
  
  				while (!isEndOfLine(buffer, candidateEnding, next)) {
  					next = read();
  				}
  				buffer.append(candidateEnding);
  
  			}
  
  			if (buffer != null && buffer.length() > 0) {
 				return buffer.toString();
 			}
 			return null;
 
 		}
 
 		/**
 		 * Check for end of line and accumulate a buffer for next time.
 		 * 
 		 * @param buffer the current line excluding the candidate ending
 		 * @param candidate a buffer containing accumulated state
 		 * @param next the next character (or -1 for end of file)
 		 * @return true if the values together signify the end of a file
 		 */
 		private boolean isEndOfLine(StringBuilder buffer, StringBuilder candidate, int next) {
 
 			if (next == -1) {
 				return true;
 			}
 
 			char c = (char) next;
 			if (ending.charAt(0) == c || candidate.length() > 0) {
 				candidate.append(c);
 			}
 
 			if (candidate.length() == 0) {
 				buffer.append(c);
 				return false;
 			}
 
 			boolean end = ending.equals(candidate.toString());
 			if (end) {
 				candidate.delete(0, candidate.length());
 			}
 			else if (candidate.length() >= ending.length()) {
 				buffer.append(candidate);
 				candidate.delete(0, candidate.length());
 			}
 
 			return end;
 
 		}
 	}
 
 }