/*
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF licenses this file
 * to you 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.apache.flink.runtime.io.disk.iomanager;

import java.io.IOException;
import java.util.ArrayList;
import java.util.List;

import org.apache.flink.core.memory.MemorySegment;

/**
 *
 */
public class AsynchronousBulkBlockReader extends AsynchronousFileIOChannel<MemorySegment, ReadRequest> implements BulkBlockChannelReader {
	
	private final ArrayList<MemorySegment> returnBuffers;
	
	
	protected AsynchronousBulkBlockReader(FileIOChannel.ID channelID, RequestQueue<ReadRequest> requestQueue, 
			List<MemorySegment> sourceSegments, int numBlocks)
	throws IOException
	{
		this (channelID, requestQueue, sourceSegments, numBlocks, new ArrayList<MemorySegment>(numBlocks));
	}
	
	private AsynchronousBulkBlockReader(FileIOChannel.ID channelID, RequestQueue<ReadRequest> requestQueue, 
			List<MemorySegment> sourceSegments, int numBlocks, ArrayList<MemorySegment> target)
	throws IOException
	{
		super(channelID, requestQueue, new CollectingCallback(target), false);
		this.returnBuffers = target;
		
		// sanity check
		if (sourceSegments.size() < numBlocks) {
			throw new IllegalArgumentException("The list of source memory segments must contain at least" +
					" as many segments as the number of blocks to read.");
		}
		
		// send read requests for all blocks
		for (int i = 0; i < numBlocks; i++) {
			readBlock(sourceSegments.remove(sourceSegments.size() - 1));
		}
	}
	
	private void readBlock(MemorySegment segment) throws IOException {
		addRequest(new SegmentReadRequest(this, segment));
	}
	
	@Override
	public List<MemorySegment> getFullSegments() {
		synchronized (this.closeLock) {
			if (!this.isClosed() || this.requestsNotReturned.get() > 0) {
				throw new IllegalStateException("Full segments can only be obtained after the reader was properly closed.");
			}
		}
		
		return this.returnBuffers;
	}
	
	// --------------------------------------------------------------------------------------------
	
	private static final class CollectingCallback implements RequestDoneCallback<MemorySegment> {
		
		private final ArrayList<MemorySegment> list;

		public CollectingCallback(ArrayList<MemorySegment> list) {
			this.list = list;
		}
		
		@Override
		public void requestSuccessful(MemorySegment buffer) {
			list.add(buffer);
		}
		
		@Override
		public void requestFailed(MemorySegment buffer, IOException e) {
			list.add(buffer);
		}
	}
}