/*
 * Copyright 2013 Websquared, 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 org.fastcatsearch.ir.document;

import java.io.File;
import java.io.IOException;
import java.util.zip.DataFormatException;
import java.util.zip.Deflater;
import java.util.zip.Inflater;

import org.fastcatsearch.ir.common.IRException;
import org.fastcatsearch.ir.common.IndexFileNames;
import org.fastcatsearch.ir.io.BufferedFileInput;
import org.fastcatsearch.ir.io.BufferedFileOutput;
import org.fastcatsearch.ir.io.BytesDataInput;
import org.fastcatsearch.ir.io.IOUtil;
import org.fastcatsearch.ir.io.IndexInput;
import org.fastcatsearch.ir.io.IndexOutput;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;


public class DocumentRestorer {
	private static Logger logger = LoggerFactory.getLogger(DocumentRestorer.class);
	private final int BUFFER_SIZE = 3 * 1024 * 1024;
	private File dir;
	
	public DocumentRestorer(File dir) throws IOException, IRException{
		this.dir = dir;
	}
	
	public void setSize(int newSize) throws IRException, IOException{
		
		IndexInput docInput = new BufferedFileInput(dir, IndexFileNames.docStored);
		IndexInput positionInput = new BufferedFileInput(dir, IndexFileNames.docPosition);
		
		//check document count and block size
		int prevDocumentCount = docInput.readInt();
		if(newSize >= prevDocumentCount){
			//do nothing
			return;
		}
		logger.info("DocumentRestorer size ={} => {}", prevDocumentCount, newSize);
		int blockSize = docInput.readInt();
		int docNo = newSize - 1;
		int docIndex = docNo / blockSize;
		int docOffset = docNo % blockSize;
		
		positionInput.seek(docIndex * IOUtil.SIZE_OF_LONG);
		long pos = positionInput.readLong();
		docInput.seek(pos);
		int len = docInput.readInt();
		positionInput.close();
		
		if(newSize % blockSize == 0){
			docInput.close();
			IndexOutput out = new BufferedFileOutput(dir, IndexFileNames.docStored, true);
			out.seek(0);
			out.writeInt(newSize);
			out.setLength(pos + len);
			logger.info("restored doc.stored file size() = {}", out.length());
			out.close();
		}else{
			//if doc is in last block
			byte[] infOutput = new byte[BUFFER_SIZE];
			byte[] defOutput = new byte[BUFFER_SIZE];
			byte[] data = new byte[len];
			docInput.readBytes(data, 0, len);
			docInput.close();
			
			Inflater decompresser = new Inflater();
			decompresser.setInput(data);
			int resultLength = -1;
			try {
				resultLength = decompresser.inflate(infOutput);
			} catch (DataFormatException e) {
				throw new IOException("DataFormatException");
			} finally {
				decompresser.end();
			}
//			logger.debug("BlockLength="+resultLength);
			BytesDataInput bai = new BytesDataInput(infOutput, 0, resultLength);
			for (int i = 0; i <= docOffset; i++) {
				int docLen = bai.readInt();
//				logger.debug("bai.position() = "+bai.position()+", docLen = "+docLen);
				bai.seek(bai.position() + docLen);
			}
			int end = (int) bai.position();
			Deflater compresser = new Deflater(Deflater.BEST_SPEED);
			compresser.setInput(infOutput, 0, end);
			compresser.finish();
			
			int compressedDataLength = compresser.deflate(defOutput);
			
			IndexOutput out = new BufferedFileOutput(dir, IndexFileNames.docStored, true);
			out.seek(0);
			out.writeInt(newSize);
			out.setLength(pos);
			out.seek(out.length());//move to end of file
			out.writeInt(compressedDataLength);
			out.writeBytes(defOutput, 0, compressedDataLength);
			logger.info("restored doc.stored file size() = {}", out.length());
			out.close();
		}
		
	}
	
	
	
	
	
}