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/**
 * Copyright (C) 2011 Ovea 
 *
 * 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.ovea.system.proc;

import com.ovea.system.pipe.PipeConnection;
import com.ovea.system.pipe.Pipes;
import com.ovea.system.util.IoUtils;

import java.io.*;
import java.util.ArrayList;
import java.util.LinkedList;
import java.util.List;
import java.util.Queue;
import java.util.concurrent.CountDownLatch;
import java.util.concurrent.TimeUnit;
import java.util.concurrent.TimeoutException;
import java.util.concurrent.atomic.AtomicReference;
import java.util.concurrent.locks.Lock;
import java.util.concurrent.locks.ReentrantLock;

/**
 * @author Mathieu Carbou ([email protected])
 */
public final class ProcessPipe extends Process {

    private final InputStream inputStream;
    private final InputStream errorStream;
    private final OutputStream outputStream;
    private final CountDownLatch finished;
    private final SharedErrorStream sharedErrorStream = new SharedErrorStream();
    private final AtomicReference exitValue = new AtomicReference();
    private final Queue processes = new LinkedList();
    private final Queue pipes = new LinkedList();

    public ProcessPipe(List processes) {
        processes = new ArrayList(processes);
        if (processes.size() < 2) throw new IllegalArgumentException("Requires at least two processes");
        finished = new CountDownLatch(processes.size());
        for (int i = 0; i < processes.size(); i++) {
            Process current = processes.get(i);
            final boolean isLast = i + 1 == processes.size();
            this.processes.add(new FutureProcess(current, new FutureProcessListener() {
                @Override
                public void onComplete(FutureProcess futureProcess) {
                    if (isLast) {
                        exitValue.compareAndSet(null, futureProcess.process().exitValue());
                    }
                    try {
                        sharedErrorStream.append(futureProcess.process().getErrorStream());
                    } catch (InterruptedException e) {
                        Thread.currentThread().interrupt();
                    }
                    onInterrupted(futureProcess);
                }

                @Override
                public void onInterrupted(FutureProcess futureProcess) {
                    if (isLast) {
                        IoUtils.close(sharedErrorStream);
                    }
                    finished.countDown();
                }
            }));
            if (i > 0) {
                pipes.add(Pipes.connect(processes.get(i - 1).getInputStream(), current.getOutputStream()));
            }
        }
        this.outputStream = processes.get(0).getOutputStream();
        this.inputStream = processes.get(processes.size() - 1).getInputStream();
        try {
            this.errorStream = new PipedInputStream(sharedErrorStream);
        } catch (IOException e) {
            throw new RuntimeException(e.getMessage(), e);
        }
    }

    /**
     * Output stream of the first process in the pipe
     */
    @Override
    public OutputStream getOutputStream() {
        return outputStream;
    }

    /**
     * Input stream of the last process in the pipe
     */
    @Override
    public InputStream getInputStream() {
        return inputStream;
    }

    /**
     * Error stream combination of all process error streams
     */
    @Override
    public InputStream getErrorStream() {
        return errorStream;
    }

    @Override
    public int waitFor() throws InterruptedException {
        if (Thread.interrupted())
            throw new InterruptedException();
        try {
            finished.await();
            return exitValue();
        } catch (InterruptedException e) {
            destroy();
            throw e;
        }
    }

    public int waitFor(long time, TimeUnit unit) throws InterruptedException, TimeoutException {
        if (Thread.interrupted())
            throw new InterruptedException();
        try {
            if (finished.await(time, unit)) {
                return exitValue();
            } else {
                throw new TimeoutException();
            }
        } catch (InterruptedException e) {
            destroy();
            throw e;
        }
    }

    @Override
    public int exitValue() throws IllegalThreadStateException {
        Integer i = exitValue.get();
        if (i == null) {
            throw new IllegalThreadStateException("Pipe as not completed");
        }
        return i;
    }

    @Override
    public void destroy() {
        while (!pipes.isEmpty()) {
            pipes.poll().interrupt();
        }
        for (FutureProcess process : processes) {
            process.cancel(true);
        }
        while (!processes.isEmpty()) {
            try {
                processes.poll().get();
            } catch (Throwable ignored) {
            }
        }
    }

    private static final class SharedErrorStream extends PipedOutputStream {

        private final Lock lock = new ReentrantLock();

        void append(InputStream stream) throws InterruptedException {
            if (Thread.interrupted()) {
                throw new InterruptedException();
            }
            try {
                int c;
                lock.lockInterruptibly();
                while ((c = stream.read()) != -1) {
                    write(c);
                }
            } catch (IOException ignored) {
            } finally {
                lock.unlock();
                IoUtils.close(stream);
            }
        }
    }
}