/*
 * (Somewhat) simple program demonstrating the use of a "bounded
 *    buffer" class of size N, with P producer threads and C consumer 
 *    threads.
 * Each producer thread will insert into the buffer M "messages"
 *   (pairs of integers); consumer threads will read from the buffer
 *   and print.
 * Consumers stop when they detect that the producers are all done and the
 *   buffer is empty.  Detection that the producers are done is accomplished by
 *   having the main program interrupt the consumers.  This is not necessarily
 *   the best approach, but illustrates the use of interrupts.
 *
 * Command-line arguments are P (producers), C (consumers), N (bufsize), 
 *   M (messages per producer), DP (minimum delay for producers),
 *   DC (minimum delay for consumers).
 *
 * Notes:
 *   Short output goes to System.out, more verbose output to System.err.
 *   We assume that calls to System.out.println() and System.err.println() 
 *   are atomic.
 */

/* ---- Main class for test program ---------------------------------- */

public class TestBoundedBuffer {

    /* Main program. */
    public static void main(String[] args) {

        if (args.length < 6) {
            System.err.println("Arguments:  " +
                    "nProducers nConsumers bufsize msgs " +
                    "minProducerDelay minConsumerDelay");
            System.exit(1);
        }

        int nProducers = 0;
        int nConsumers = 0;
        int bufsize = 0;
        int msgs = 0;
        int minPdelay = 0;
        int minCdelay = 0;
        try {
            nProducers = Integer.parseInt(args[0]);
            nConsumers = Integer.parseInt(args[1]);
            bufsize = Integer.parseInt(args[2]);
            msgs = Integer.parseInt(args[3]);
            minPdelay = Integer.parseInt(args[4]);
            minCdelay = Integer.parseInt(args[5]);
        }
        catch (NumberFormatException e) {
            System.err.println("Arguments:  " +
                    "nProducers nConsumers bufsize msgs " +
                    "minProducerDelay minConsumerDelay");
            System.exit(1);
        }

        BoundedBuffer buffer = new BoundedBuffer(bufsize);
        RandomDelayer pDelayer = new RandomDelayer(minPdelay);
        RandomDelayer cDelayer = new RandomDelayer(minCdelay);

        /* create producer, consumer threads */
        Thread[] producers = new Thread[nProducers];
        for (int i = 0; i < producers.length; ++i) {
            producers[i] = new Thread(new Producer(i, msgs, buffer, pDelayer));
        }
        Thread[] consumers = new Thread[nConsumers];
        for (int i = 0; i < consumers.length; ++i) {
            consumers[i] = new Thread(new Consumer(i, buffer, cDelayer));
        }
        /* start all threads */
        for (int i = 0; i < producers.length; ++i) {
            producers[i].start();
        }
        for (int i = 0; i < consumers.length; ++i) {
            consumers[i].start();
        }
        /* wait for producers to finish */
        try {
            for (int i = 0; i < producers.length; ++i) {
                producers[i].join();
            }
        }
        catch (InterruptedException e) {
            System.err.println("this should not happen");
        }
        /* interrupt consumers (so they know producers are done) */
        for (int i = 0; i < consumers.length; ++i) {
            consumers[i].interrupt();
        }
        /* wait for consumers to finish */
        try {
            for (int i = 0; i < consumers.length; ++i) {
                consumers[i].join();
            }
        }
        catch (InterruptedException e) {
            System.err.println("this should not happen");
        }
        System.out.println("That's all, folks!");
    }

    /* ---- Class for producers ------------------------------------------ */

    /* Each producer thread has one object of this class. */

    private static class Producer implements Runnable {

        private int myID;
        private int msgs;
        private BoundedBuffer buffer; 
        private RandomDelayer delayer;

        public Producer(int myID, int msgs, BoundedBuffer buffer, 
                RandomDelayer delayer) {
            this.myID = myID;
            this.msgs = msgs;
            this.buffer = buffer;
            this.delayer = delayer;
        }

        /* Method containing code for thread to run. */
        public void run() {
            try {
                for (int i = 0; i < msgs; ++i) {
                    delayer.delay();
                    TestMessage m = new TestMessage(myID, i);
                    buffer.put(m);
                    System.out.println("Message " + m + " produced");
                }
            }
            catch (InterruptedException e) { 
                System.err.println("this should not happen");
            }
            System.out.println("Producer " + myID + " done");
        }
    }

    /* ---- Class for consumers ------------------------------------------ */

    /* Each consumer thread has one object of this class. */

    private static class Consumer implements Runnable {

        private int myID;
        private BoundedBuffer buffer; 
        private RandomDelayer delayer;

        public Consumer(int myID, BoundedBuffer buffer, RandomDelayer delayer) {
            this.myID = myID;
            this.buffer = buffer;
            this.delayer = delayer;
        }

        /* Method containing code for thread to run. */
        public void run() {
            boolean producersDone = false;
            boolean done = false;
            while (!done) {
                if (Thread.interrupted()) {
                    producersDone = true;
                    System.out.println("Consumer " + myID + 
                            " detected interrupted status");
                }
                try {
                    delayer.delay();
                    TestMessage m = null;
                    /* synchronize here because otherwise we could get
                     * stuck waiting to get something from a buffer that
                     * has been emptied by another consumer.
                     */
                    synchronized(buffer) {
                        if (producersDone && buffer.isEmpty())
                            done = true;
                        else 
                            m = (TestMessage) buffer.get();
                    }
                    if (!done)
                        System.out.println("Message " + m + 
                                " consumed by " + myID);
                }
                catch (InterruptedException e) { 
                    System.out.println("Consumer " + myID + " interrupted");
                    producersDone = true;
                }
            }
            System.out.println("Consumer " + myID + " done");
        }
    }

    /* ---- Class for messages for bounded-buffer test program ----------- */

    private static class TestMessage {

        private int producerID;
        private int msgNum;

        public TestMessage(int producerID, int msgNum) {
            this.producerID = producerID;
            this.msgNum = msgNum;
        }

        public String toString() {
            return "(" + producerID + ", " + msgNum + ")";
        }
    }

    /* ---- Class for generating random delay times ---------------------- */

    private static class RandomDelayer {

        private int minDelay;
        private int maxDelay;
        private java.util.Random rand;

        public RandomDelayer(int minDelay) {
            this.minDelay = minDelay;
            this.maxDelay = minDelay * 2;
            rand = new java.util.Random(1);
        }

        /* Method to wait for a randomly-generated interval. 
         * Allows exceptions thrown by Thread.sleep() to bubble up. 
         */
        public void delay() throws InterruptedException {
            int d = (int) (rand.nextDouble()*(maxDelay - minDelay)
                    + minDelay);
            Thread.sleep(d * 1000);
        }
    }
}