/**
 * Bounded buffer with synchronization.
 */
package csci3366sample.bbuf;

public class BoundedBuffer<T> {

    /* store as circular queue in array */
    private T[] buffer;
    private int nextToRemove;
    private int numElements;
    private boolean verbose;

    @SuppressWarnings("unchecked")
    public BoundedBuffer(int sz, boolean verbose) {
        buffer = (T[]) new Object[sz];
        nextToRemove = 0;
        numElements = 0;
        this.verbose = verbose;
    }

    /**
     * Print message if "verbose" flag on.
     */
    private void verbosePrint(String msg) {
        if (verbose) System.out.println("**"+msg);
    }

    /**
     * Put item into buffer.
     * Waits if buffer is full.
     * Allows exceptions thrown by wait() to bubble up.
     */
    public synchronized void put(T item) throws InterruptedException {
        verbosePrint("starting put with numElements = " + numElements);
        /* wait until not full */
        while (numElements == buffer.length) 
            wait();
        int next = (nextToRemove + numElements) % buffer.length;
        buffer[next] = item;
        ++numElements;
        /* 
         * wake up all waiting threads (just in case some are waiting
         * for "buffer not empty") 
         */
        notifyAll();
        verbosePrint("ending put with numElements = " + numElements);
    }

    /**
     * Get item from buffer.
     * Waits if buffer is empty.
     * Allows exceptions thrown by wait() to bubble up.
     * @return item
     */
    public synchronized T get() throws InterruptedException {
        verbosePrint("starting get with numElements = " + 
                numElements);
        /* wait until not empty */
        while (numElements == 0)
            wait();
        T item = buffer[nextToRemove];
        nextToRemove = (nextToRemove + 1) % buffer.length;
        --numElements;
        /* 
         * wake up all waiting threads (just in case some are waiting
         * for "buffer not full") 
         */
        notifyAll();
        verbosePrint("ending get with numElements = " + numElements);
        return item;
    }

    /**
     * Check if buffer is empty.
     */
    public synchronized boolean isEmpty() {
        return (numElements == 0);
    }
}