/*
 * 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.operators;

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

import org.apache.flink.api.common.typeutils.TypeSerializer;
import org.apache.flink.api.common.typeutils.TypeSerializerFactory;
import org.apache.flink.core.memory.DataInputView;
import org.apache.flink.core.memory.MemorySegment;
import org.apache.flink.runtime.io.disk.InputViewIterator;
import org.apache.flink.runtime.io.disk.SpillingBuffer;
import org.apache.flink.runtime.io.disk.iomanager.IOManager;
import org.apache.flink.runtime.jobgraph.tasks.AbstractInvokable;
import org.apache.flink.runtime.memory.ListMemorySegmentSource;
import org.apache.flink.runtime.memory.MemoryAllocationException;
import org.apache.flink.runtime.memory.MemoryManager;
import org.apache.flink.runtime.operators.util.CloseableInputProvider;
import org.apache.flink.util.MutableObjectIterator;

/**
 * 
 */
public class TempBarrier<T> implements CloseableInputProvider<T> {
	
	private final SpillingBuffer buffer;
	
	private final TypeSerializer<T> serializer;
	
	private final TempWritingThread tempWriter;
	
	private final MemoryManager memManager;
	
	private final Object lock = new Object();
	
	private volatile Throwable exception;
	
	private final ArrayList<MemorySegment> memory;
	
	private volatile boolean writingDone;
	
	private volatile boolean closed;

	// --------------------------------------------------------------------------------------------
	
	public TempBarrier(AbstractInvokable owner, MutableObjectIterator<T> input, TypeSerializerFactory<T> serializerFactory,
			MemoryManager memManager, IOManager ioManager, int numPages) throws MemoryAllocationException
	{
		this.serializer = serializerFactory.getSerializer();
		this.memManager = memManager;
		
		this.memory = new ArrayList<MemorySegment>(numPages);
		memManager.allocatePages(owner, this.memory, numPages);
		
		this.buffer = new SpillingBuffer(ioManager, new ListMemorySegmentSource(this.memory), memManager.getPageSize());
		this.tempWriter = new TempWritingThread(input, serializerFactory.getSerializer(), this.buffer);
	}
	
	// --------------------------------------------------------------------------------------------

	public void startReading() {
		this.tempWriter.start();
	}

	/**
	 * 
	 * This method resets the input!
	 * 
	 * @see org.apache.flink.runtime.operators.util.CloseableInputProvider#getIterator()
	 */
	@Override
	public MutableObjectIterator<T> getIterator() throws InterruptedException, IOException {
		synchronized (this.lock) {
			while (this.exception == null && !this.writingDone) {
				this.lock.wait(5000);
			}
		}
		
		if (this.exception != null) {
			throw new RuntimeException("An error occurred creating the temp table.", this.exception);
		} else if (this.writingDone) {
			final DataInputView in = this.buffer.flip();
			return new InputViewIterator<T>(in, this.serializer);
		} else {
			return null;
		}
	}


	@Override
	public void close() throws IOException {
		synchronized (this.lock) {
			if (this.closed) {
				return;
			}
			if (this.exception == null) {
				this.exception = new Exception("The dam has been closed.");
			}
			this.lock.notifyAll();
		}
		
		try {
			this.tempWriter.shutdown();
			this.tempWriter.join();
		} catch (InterruptedException iex) {
			throw new IOException("Interrupted");
		}
		
		this.memManager.release(this.buffer.close());
		this.memManager.release(this.memory);
	}
	
	private void setException(Throwable t) {
		synchronized (this.lock) {
			this.exception = t;
			this.lock.notifyAll();
		}
		try {
			close();
		} catch (Throwable ex) {}
	}
	
	private void writingDone() throws IOException {
		synchronized (this.lock) {
			this.writingDone = true;
			this.lock.notifyAll();
		}
	}
	
	// --------------------------------------------------------------------------------------------
	
	private final class TempWritingThread extends Thread {
		
		private final MutableObjectIterator<T> input;
		
		private final TypeSerializer<T> serializer;
		
		private final SpillingBuffer buffer;
		
		private volatile boolean running = true;
		
		private TempWritingThread(MutableObjectIterator<T> input, TypeSerializer<T> serializer, SpillingBuffer buffer) {
			super("Temp writer");
			setDaemon(true);
			
			this.input = input;
			this.serializer = serializer;
			this.buffer = buffer;
		}
		
		@Override
		public void run() {
			final MutableObjectIterator<T> input = this.input;
			final TypeSerializer<T> serializer = this.serializer;
			final SpillingBuffer buffer = this.buffer;
			
			try {
				T record = serializer.createInstance();
				
				while (this.running && ((record = input.next(record)) != null)) {
					serializer.serialize(record, buffer);
				}
				
				TempBarrier.this.writingDone();
			}
			catch (Throwable t) {
				TempBarrier.this.setException(t);
			}
		}
		
		public void shutdown() {
			this.running = false;
			this.interrupt();
		}
	}
}