/*
 * 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.karaf.shell.wrapper;

import java.io.InputStream;
import java.io.OutputStream;
import java.io.IOException;

/**
 * Copies standard output and error of children streams to standard output and error of the parent.
 */
public class PumpStreamHandler {

    private final InputStream in;

    private final OutputStream out;

    private final OutputStream err;

    private final String name;

    private StreamPumper outputPump;

    private StreamPumper errorPump;

    private StreamPumper inputPump;

    //
    // NOTE: May want to use a ThreadPool here, 3 threads per/pair seems kinda expensive :-(
    //

    public PumpStreamHandler(final InputStream in, final OutputStream out, final OutputStream err, String name) {
        assert in != null;
        assert out != null;
        assert err != null;
        assert name != null;

        this.in = in;
        this.out = out;
        this.err = err;
        this.name = name;
    }

    public PumpStreamHandler(final InputStream in, final OutputStream out, final OutputStream err) {
        this(in, out, err, "<unknown>");
    }

    public PumpStreamHandler(final OutputStream out, final OutputStream err) {
        this(null, out, err);
    }

    public PumpStreamHandler(final OutputStream outAndErr) {
        this(outAndErr, outAndErr);
    }

    /**
     * Set the input stream from which to read the standard output of the child.
     */
    public void setChildOutputStream(final InputStream in) {
        assert in != null;

        createChildOutputPump(in, out);
    }

    /**
     * Set the input stream from which to read the standard error of the child.
     */
    public void setChildErrorStream(final InputStream in) {
        assert in != null;

        if (err != null) {
            createChildErrorPump(in, err);
        }
    }

    /**
     * Set the output stream by means of which input can be sent to the child.
     */
    public void setChildInputStream(final OutputStream out) {
        assert out != null;

        if (in != null) {
            inputPump = createInputPump(in, out, true);
        }
        else {
            try {
                out.close();
            } catch (IOException e) { }
        }
    }

    /**
     * Attach to a child streams from the given process.
     *
     * @param p     The process to attach to.
     */
    public void attach(final Process p) {
        assert p != null;

        setChildInputStream(p.getOutputStream());
        setChildOutputStream(p.getInputStream());
        setChildErrorStream(p.getErrorStream());
    }
    /**
     * Start pumping the streams.
     */
    public void start() {
        if (outputPump != null) {
            Thread thread = new Thread(outputPump);
            thread.setDaemon(true);
            thread.setName("Output pump for " + this.name);
            thread.start();
        }

        if (errorPump != null) {
            Thread thread = new Thread(errorPump);
            thread.setDaemon(true);
            thread.setName("Error pump for " + this.name);
            thread.start();
        }

        if (inputPump != null) {
            Thread thread = new Thread(inputPump);
            thread.setDaemon(true);
            thread.setName("Input pump for " + this.name);
            thread.start();
        }
    }

    /**
     * Stop pumping the streams.
     */
    public void stop() {
        if (outputPump != null) {
            try {
                outputPump.stop();
                outputPump.waitFor();
            }
            catch (InterruptedException e) {
                // ignore
            }
        }

        if (errorPump != null) {
            try {
                errorPump.stop();
                errorPump.waitFor();
            }
            catch (InterruptedException e) {
                // ignore
            }
        }

        if (inputPump != null) {
            inputPump.stop();
        }

        try {
            err.flush();
        } catch (IOException e) { }
        try {
            out.flush();
        } catch (IOException e) { }
    }

    /**
     * Create the pump to handle child output.
     */
    protected void createChildOutputPump(final InputStream in, final OutputStream out) {
        assert in != null;
        assert out != null;

        outputPump = createPump(in, out);
    }

    /**
     * Create the pump to handle error output.
     */
    protected void createChildErrorPump(final InputStream in, final OutputStream out) {
        assert in != null;
        assert out != null;

        errorPump = createPump(in, out);
    }

    /**
     * Creates a stream pumper to copy the given input stream to the given output stream.
     */
    protected StreamPumper createPump(final InputStream in, final OutputStream out) {
        assert in != null;
        assert out != null;

        return createPump(in, out, false);
    }

    /**
     * Creates a stream pumper to copy the given input stream to the
     * given output stream.
     *
     * @param in                    The input stream to copy from.
     * @param out                   The output stream to copy to.
     * @param closeWhenExhausted    If true close the inputstream.
     * @return                      A thread object that does the pumping.
     */
    protected StreamPumper createPump(final InputStream in, final OutputStream out, final boolean closeWhenExhausted) {
        assert in != null;
        assert out != null;

        StreamPumper pumper = new StreamPumper(in, out, closeWhenExhausted);
        return pumper;
    }

    /**
     * Creates a stream pumper to copy the given input stream to the
     * given output stream. Used for standard input.
     */
    protected StreamPumper createInputPump(final InputStream in, final OutputStream out, final boolean closeWhenExhausted) {
        assert in != null;
        assert out != null;

        StreamPumper pumper = new StreamPumper(in, out, closeWhenExhausted);
        pumper.setAutoflush(true);
        return pumper;
    }
}
