/*
    * 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.nio.charset.Charset;
  
  import org.apache.commons.logging.Log;
  import org.apache.commons.logging.LogFactory;
  import org.springframework.batch.item.ItemReader;
  import org.springframework.batch.item.ReaderNotOpenException;
  import org.springframework.batch.item.file.separator.RecordSeparatorPolicy;
  import org.springframework.batch.item.file.separator.SimpleRecordSeparatorPolicy;
  import org.springframework.batch.item.support.AbstractItemCountingItemStreamItemReader;
  import org.springframework.beans.factory.InitializingBean;
  import org.springframework.core.io.Resource;
  import org.springframework.util.Assert;
  import org.springframework.util.ClassUtils;
  import org.springframework.util.StringUtils;
  
  /**
   * Restartable {@link ItemReader} that reads lines from input {@link #setResource(Resource)}. Line is defined by the
   * {@link #setRecordSeparatorPolicy(RecordSeparatorPolicy)} and mapped to item using {@link #setLineMapper(LineMapper)}.
   * If an exception is thrown during line mapping it is rethrown as {@link FlatFileParseException} adding information
   * about the problematic line and its line number.
   * 
   * @author Robert Kasanicky
   */
  public class FlatFileItemReader<T> extends AbstractItemCountingItemStreamItemReader<T> implements
  		ResourceAwareItemReaderItemStream<T>, InitializingBean {
  
  	private static final Log logger = LogFactory.getLog(FlatFileItemReader.class);
  
  	// default encoding for input files
  	public static final String DEFAULT_CHARSET = Charset.defaultCharset().name();
  
  	private RecordSeparatorPolicy recordSeparatorPolicy = new SimpleRecordSeparatorPolicy();
  
  	private Resource resource;
  
  	private BufferedReader reader;
  
  	private int lineCount = 0;
  
  	private String[] comments = new String[] { "#" };
  
  	private boolean noInput = false;
  
  	private String encoding = DEFAULT_CHARSET;
  
  	private LineMapper<T> lineMapper;
  
  	private int linesToSkip = 0;
  
  	private LineCallbackHandler skippedLinesCallback;
  
  	private boolean strict = true;
  
  	private BufferedReaderFactory bufferedReaderFactory = new DefaultBufferedReaderFactory();
  
  	public FlatFileItemReader() {
  		setName(ClassUtils.getShortName(FlatFileItemReader.class));
  	}
  
  	/**
  	 * In strict mode the reader will throw an exception on
  	 * {@link #open(org.springframework.batch.item.ExecutionContext)} if the input resource does not exist.
  	 * @param strict <code>true</code> by default
  	 */
  	public void setStrict(boolean strict) {
  		this.strict = strict;
  	}
  
  	/**
  	 * @param skippedLinesCallback will be called for each one of the initial skipped lines before any items are read.
  	 */
  	public void setSkippedLinesCallback(LineCallbackHandler skippedLinesCallback) {
  		this.skippedLinesCallback = skippedLinesCallback;
  	}
  
  	/**
  	 * Public setter for the number of lines to skip at the start of a file. Can be used if the file contains a header
  	 * without useful (column name) information, and without a comment delimiter at the beginning of the lines.
  	 * 
 	 * @param linesToSkip the number of lines to skip
 	 */
 	public void setLinesToSkip(int linesToSkip) {
 		this.linesToSkip = linesToSkip;
 	}
 
 	/**
 	 * Setter for line mapper. This property is required to be set.
 	 * @param lineMapper maps line to item
 	 */
 	public void setLineMapper(LineMapper<T> lineMapper) {
 		this.lineMapper = lineMapper;
 	}
 
 	/**
 	 * Setter for the encoding for this input source. Default value is {@link #DEFAULT_CHARSET}.
 	 * 
 	 * @param encoding a properties object which possibly contains the encoding for this input file;
 	 */
 	public void setEncoding(String encoding) {
 		this.encoding = encoding;
 	}
 
 	/**
 	 * Factory for the {@link BufferedReader} that will be used to extract lines from the file. The default is fine for
 	 * plain text files, but this is a useful strategy for binary files where the standard BufferedReaader from java.io
 	 * is limiting.
 	 * 
 	 * @param bufferedReaderFactory the bufferedReaderFactory to set
 	 */
 	public void setBufferedReaderFactory(BufferedReaderFactory bufferedReaderFactory) {
 		this.bufferedReaderFactory = bufferedReaderFactory;
 	}
 
 	/**
 	 * Setter for comment prefixes. Can be used to ignore header lines as well by using e.g. the first couple of column
 	 * names as a prefix.
 	 * 
 	 * @param comments an array of comment line prefixes.
 	 */
 	public void setComments(String[] comments) {
 		this.comments = new String[comments.length];
 		System.arraycopy(comments, 0, this.comments, 0, comments.length);
 	}
 
 	/**
 	 * Public setter for the input resource.
 	 */
     @Override
 	public void setResource(Resource resource) {
 		this.resource = resource;
 	}
 
 	/**
 	 * Public setter for the recordSeparatorPolicy. Used to determine where the line endings are and do things like
 	 * continue over a line ending if inside a quoted string.
 	 * 
 	 * @param recordSeparatorPolicy the recordSeparatorPolicy to set
 	 */
 	public void setRecordSeparatorPolicy(RecordSeparatorPolicy recordSeparatorPolicy) {
 		this.recordSeparatorPolicy = recordSeparatorPolicy;
 	}
 
 	/**
 	 * @return string corresponding to logical record according to
 	 * {@link #setRecordSeparatorPolicy(RecordSeparatorPolicy)} (might span multiple lines in file).
 	 */
 	@Override
 	protected T doRead() throws Exception {
 		if (noInput) {
 			return null;
 		}
 
 		String line = readLine();
 
 		if (line == null) {
 			return null;
 		}
 		else {
 			try {
 				return lineMapper.mapLine(line, lineCount);
 			}
 			catch (Exception ex) {
 				throw new FlatFileParseException("Parsing error at line: " + lineCount + " in resource=["
 						+ resource.getDescription() + "], input=[" + line + "]", ex, line, lineCount);
 			}
 		}
 	}
 
 	/**
 	 * @return next line (skip comments).getCurrentResource
 	 */
 	private String readLine() {
 
 		if (reader == null) {
 			throw new ReaderNotOpenException("Reader must be open before it can be read.");
 		}
 
 		String line = null;
 
 		try {
 			line = this.reader.readLine();
 			if (line == null) {
 				return null;
 			}
 			lineCount++;
 			while (isComment(line)) {
 				line = reader.readLine();
 				if (line == null) {
 					return null;
 				}
 				lineCount++;
 			}
 
 			line = applyRecordSeparatorPolicy(line);
 		}
 		catch (IOException e) {
 			// Prevent IOException from recurring indefinitely
 			// if client keeps catching and re-calling
 			noInput = true;
 			throw new NonTransientFlatFileException("Unable to read from resource: [" + resource + "]", e, line,
 					lineCount);
 		}
 		return line;
 	}
 
 	private boolean isComment(String line) {
 		for (String prefix : comments) {
 			if (line.startsWith(prefix)) {
 				return true;
 			}
 		}
 		return false;
 	}
 
 	@Override
 	protected void doClose() throws Exception {
 		lineCount = 0;
 		if (reader != null) {
 			reader.close();
 		}
 	}
 
 	@Override
 	protected void doOpen() throws Exception {
 		Assert.notNull(resource, "Input resource must be set");
 		Assert.notNull(recordSeparatorPolicy, "RecordSeparatorPolicy must be set");
 
 		noInput = true;
 		if (!resource.exists()) {
 			if (strict) {
 				throw new IllegalStateException("Input resource must exist (reader is in 'strict' mode): " + resource);
 			}
 			logger.warn("Input resource does not exist " + resource.getDescription());
 			return;
 		}
 
 		if (!resource.isReadable()) {
 			if (strict) {
 				throw new IllegalStateException("Input resource must be readable (reader is in 'strict' mode): "
 						+ resource);
 			}
 			logger.warn("Input resource is not readable " + resource.getDescription());
 			return;
 		}
 
 		reader = bufferedReaderFactory.create(resource, encoding);
 		for (int i = 0; i < linesToSkip; i++) {
 			String line = readLine();
 			if (skippedLinesCallback != null) {
 				skippedLinesCallback.handleLine(line);
 			}
 		}
 		noInput = false;
 	}
 
     @Override
 	public void afterPropertiesSet() throws Exception {
 		Assert.notNull(lineMapper, "LineMapper is required");
 	}
 
 	@Override
 	protected void jumpToItem(int itemIndex) throws Exception {
 		for (int i = 0; i < itemIndex; i++) {
 			readLine();
 		}
 	}
 
 	private String applyRecordSeparatorPolicy(String line) throws IOException {
 
 		String record = line;
 		while (line != null && !recordSeparatorPolicy.isEndOfRecord(record)) {
 			line = this.reader.readLine();
 			if (line == null) {
 				if (StringUtils.hasText(record)) {
 					// A record was partially complete since it hasn't ended but
 					// the line is null
 					throw new FlatFileParseException("Unexpected end of file before record complete", record, lineCount);
 				}
 				else {
 					// Record has no text but it might still be post processed
 					// to something (skipping preProcess since that was already
 					// done)
 					break;
 				}
 			}
 			else {
 				lineCount++;
 			}
 			record = recordSeparatorPolicy.preProcess(record) + line;
 		}
 
 		return recordSeparatorPolicy.postProcess(record);
 
 	}
 
 }