/**
 * (C) Copyright IBM Corp. 2010, 2015
 *
 * 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.ibm.bi.dml.runtime.io;

import java.io.BufferedWriter;
import java.io.IOException;
import java.io.OutputStreamWriter;
import java.util.ArrayList;
import java.util.List;
import java.util.concurrent.Callable;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;
import java.util.concurrent.Future;

import org.apache.hadoop.fs.FileSystem;
import org.apache.hadoop.fs.Path;
import org.apache.hadoop.mapred.JobConf;

import com.ibm.bi.dml.conf.DMLConfig;
import com.ibm.bi.dml.hops.OptimizerUtils;
import com.ibm.bi.dml.runtime.controlprogram.parfor.stat.InfrastructureAnalyzer;
import com.ibm.bi.dml.runtime.matrix.data.IJV;
import com.ibm.bi.dml.runtime.matrix.data.MatrixBlock;
import com.ibm.bi.dml.runtime.matrix.data.OutputInfo;
import com.ibm.bi.dml.runtime.matrix.data.SparseRowsIterator;
import com.ibm.bi.dml.runtime.util.MapReduceTool;

public class WriterTextCellParallel extends WriterTextCell
{
	/**
	 * 
	 * @param path
	 * @param job
	 * @param src
	 * @param rlen
	 * @param clen
	 * @param brlen
	 * @param bclen
	 * @throws IOException
	 */
	@Override
	protected void writeTextCellMatrixToHDFS( Path path, JobConf job, MatrixBlock src, long rlen, long clen )
		throws IOException
	{
		//estimate output size and number of output blocks (min 1)
		int numPartFiles = (int)(OptimizerUtils.estimateSizeTextOutput(src.getNumRows(), src.getNumColumns(), src.getNonZeros(), 
				              OutputInfo.TextCellOutputInfo)  / InfrastructureAnalyzer.getHDFSBlockSize());
		numPartFiles = Math.max(numPartFiles, 1);
		
		//determine degree of parallelism
		int numThreads = OptimizerUtils.getParallelTextWriteParallelism();
		numThreads = Math.min(numThreads, numPartFiles);
		
		//fall back to sequential write if dop is 1 (e.g., <128MB) in order to create single file
		if( numThreads <= 1 ) {
			super.writeTextCellMatrixToHDFS(path, job, src, rlen, clen);
			return;
		}
		
		//create directory for concurrent tasks
		MapReduceTool.createDirIfNotExistOnHDFS(path.toString(), DMLConfig.DEFAULT_SHARED_DIR_PERMISSION);

		//create and execute tasks
		try 
		{
			ExecutorService pool = Executors.newFixedThreadPool(numThreads);
			ArrayList<WriteTextTask> tasks = new ArrayList<WriteTextTask>();
			int blklen = (int)Math.ceil((double)rlen / numThreads);
			for(int i=0; i<numThreads & i*blklen<rlen; i++) {
				Path newPath = new Path(path, String.format("0-m-%05d",i));
				tasks.add(new WriteTextTask(newPath, job, src, i*blklen, (int)Math.min((i+1)*blklen, rlen)));
			}

			//wait until all tasks have been executed
			List<Future<Object>> rt = pool.invokeAll(tasks);	
			pool.shutdown();
			
			//check for exceptions 
			for( Future<Object> task : rt )
				task.get();
		} 
		catch (Exception e) {
			throw new IOException("Failed parallel write of text output.", e);
		}
	}

	
	/**
	 * 
	 * 
	 */
	private static class WriteTextTask implements Callable<Object> 
	{
		private JobConf _job = null;
		private MatrixBlock _src = null;
		private Path _path =null;
		private int _rl = -1;
		private int _ru = -1;
		
		public WriteTextTask(Path path, JobConf job, MatrixBlock src, int rl, int ru)
		{
			_path = path;
			_job = job;
			_src = src;
			_rl = rl;
			_ru = ru;
		}

		@Override
		public Object call() throws Exception 
		{
			boolean entriesWritten = false;
			FileSystem fs = FileSystem.get(_job);
			BufferedWriter bw = null;			
			int cols = _src.getNumColumns();

			try
			{
				//for obj reuse and preventing repeated buffer re-allocations
				StringBuilder sb = new StringBuilder();
		        bw = new BufferedWriter(new OutputStreamWriter(fs.create(_path,true)));
				
				if( _src.isInSparseFormat() ) //SPARSE
				{			   
					SparseRowsIterator iter = _src.getSparseRowsIterator(_rl, _ru);
					
					while( iter.hasNext() )
					{
						IJV cell = iter.next();

						sb.append(cell.i+1);
						sb.append(' ');
						sb.append(cell.j+1);
						sb.append(' ');
						sb.append(cell.v);
						sb.append('\n');
						bw.write( sb.toString() );
						sb.setLength(0); 
						entriesWritten = true;
					}
				}
				else //DENSE
				{
					for( int i=_rl; i<_ru; i++ )
					{
						String rowIndex = Integer.toString(i+1);					
						for( int j=0; j<cols; j++ )
						{
							double lvalue = _src.getValueDenseUnsafe(i, j);
							if( lvalue != 0 ) //for nnz
							{
								sb.append(rowIndex);
								sb.append(' ');
								sb.append( j+1 );
								sb.append(' ');
								sb.append( lvalue );
								sb.append('\n');
								bw.write( sb.toString() );
								sb.setLength(0); 
								entriesWritten = true;
							}
							
						}
					}
				}
				
				//handle empty result
				if ( !entriesWritten ) {
			        bw.write("1 1 0\n");
				}
			}
			finally
			{
				IOUtilFunctions.closeSilently(bw);
			}
			
			return null;
		}
	}
}