package com.cgi.atom.common.priorityexec;

/**
 * Created by nageswararao.vesepog on 8/24/2016.
 */

import java.util.*;
import java.util.concurrent.BlockingDeque;
import java.util.concurrent.TimeUnit;
import java.util.concurrent.locks.Condition;
import java.util.concurrent.locks.ReentrantLock;

public class PriorityBlockingDeque<E>
        extends AbstractQueue<E>
        implements BlockingDeque<E>, java.io.Serializable {

    /*
     * Implemented as a navigable set protected by a
     * single lock and using conditions to manage blocking.
     */

    private final int capacity;

    private final LinkedList<E> list;
    /**
     * Main lock guarding all access
     */
    private final ReentrantLock lock = new ReentrantLock();
    /**
     * Condition for waiting takes
     */
    private final Condition  notEmpty = lock.newCondition();
    /**
     * Condition for waiting puts
     */
    private final Condition notFull = lock.newCondition();
    private  Comparator<E> comparator;

    /**
     * Creates a <tt>PriorityBlockingDeque</tt> with a capacity of
     * {@link Integer#MAX_VALUE}.
     */
    public PriorityBlockingDeque() {
        this(null, Integer.MAX_VALUE);
    }

    /**
     * Creates a <tt>PriorityBlockingDeque</tt> with the given (fixed) capacity.
     *
     * @param capacity the capacity of this deque
     * @throws IllegalArgumentException if <tt>capacity</tt> is less than 1
     */
    public PriorityBlockingDeque(int capacity) {
        this(null, capacity);
    }

    public PriorityBlockingDeque(Comparator<E> comparator, int capacity) {
        if (capacity <= 0) throw new IllegalArgumentException();
        this.capacity = capacity;
        this.list = new LinkedList<E>();
        this.comparator = comparator;
    }

    // Basic adding and removing operations, called only while holding lock

    /**
     * Adds e or returns false if full.
     *
     * @param e The element to add.
     * @return Whether adding was successful.
     */
    private boolean innerAdd(E e) {
        if (list.size() >= capacity)
            return false;

        int insertionPoint = Collections.binarySearch(list, e, comparator);
        if (insertionPoint < 0) {
            // this means the key didn't exist, so the insertion point is negative minus 1.
            insertionPoint = -insertionPoint - 1;
        }

        list.add(insertionPoint, e);
        notEmpty.signal();

        return true;
    }

    /**
     * Removes and returns first element, or null if empty.
     *
     * @return The removed element.
     */
    private E innerRemoveFirst() {
        E f = list.pollFirst();
        if (f == null)
            return null;


        notFull.signal();
        return f;
    }

    /**
     * Removes and returns last element, or null if empty.
     *
     * @return The removed element.
     */
    private E innerRemoveLast() {
        E l = list.pollLast();
        if (l == null)
            return null;

        notFull.signal();
        return l;
    }

    // BlockingDeque methods

    /**
     * @throws IllegalStateException {@inheritDoc}
     * @throws NullPointerException  {@inheritDoc}
     */
    public void addFirst(E e) {
        if (!offerFirst(e))
            throw new IllegalStateException("Deque full");
    }

    /**
     * @throws IllegalStateException {@inheritDoc}
     * @throws NullPointerException  {@inheritDoc}
     */
    public void addLast(E e) {
        if (!offerLast(e))
            throw new IllegalStateException("Deque full");
    }

    /**
     * @throws NullPointerException {@inheritDoc}
     */
    public boolean offerFirst(E e) {
        if (e == null) throw new NullPointerException();
        lock.lock();
        try {
            return innerAdd(e);
        } finally {
            lock.unlock();
        }
    }

    /**
     * @throws NullPointerException {@inheritDoc}
     */
    public boolean offerLast(E e) {
        if (e == null) throw new NullPointerException();
        lock.lock();
        try {
            return innerAdd(e);
        } finally {
            lock.unlock();
        }
    }

    /**
     * @throws NullPointerException {@inheritDoc}
     * @throws InterruptedException {@inheritDoc}
     */
    public void putFirst(E e) throws InterruptedException {
        if (e == null) throw new NullPointerException();
        lock.lock();
        try {
            while (!innerAdd(e))
                notFull.await();
        } finally {
            lock.unlock();
        }
    }

    /**
     * @throws NullPointerException {@inheritDoc}
     * @throws InterruptedException {@inheritDoc}
     */
    public void putLast(E e) throws InterruptedException {
        if (e == null) throw new NullPointerException();
        lock.lock();
        try {
            while (!innerAdd(e))
                notFull.await();
        } finally {
            lock.unlock();
        }
    }

    /**
     * @throws NullPointerException {@inheritDoc}
     * @throws InterruptedException {@inheritDoc}
     */
    public boolean offerFirst(E e, long timeout, TimeUnit unit)
            throws InterruptedException {
        if (e == null) throw new NullPointerException();
        long nanos = unit.toNanos(timeout);
        lock.lockInterruptibly();
        try {
            for (; ;) {
                if (innerAdd(e))
                    return true;
                if (nanos <= 0)
                    return false;
                nanos = notFull.awaitNanos(nanos);
            }
        } finally {
            lock.unlock();
        }
    }

    /**
     * @throws NullPointerException {@inheritDoc}
     * @throws InterruptedException {@inheritDoc}
     */
    public boolean offerLast(E e, long timeout, TimeUnit unit)
            throws InterruptedException {
        if (e == null) throw new NullPointerException();
        long nanos = unit.toNanos(timeout);
        lock.lockInterruptibly();
        try {
            for (; ;) {
                if (innerAdd(e))
                    return true;
                if (nanos <= 0)
                    return false;
                nanos = notFull.awaitNanos(nanos);
            }
        } finally {
            lock.unlock();
        }
    }

    /**
     * @throws NoSuchElementException {@inheritDoc}
     */
    public E removeFirst() {
        E x = pollFirst();
        if (x == null) throw new NoSuchElementException();
        return x;
    }

    /**
     * @throws NoSuchElementException {@inheritDoc}
     */
    public E removeLast() {
        E x = pollLast();
        if (x == null) throw new NoSuchElementException();
        return x;
    }

    public E pollFirst() {
        lock.lock();
        try {
            return innerRemoveFirst();
        } finally {
            lock.unlock();
        }
    }

    public E pollLast() {
        lock.lock();
        try {
            return innerRemoveLast();
        } finally {
            lock.unlock();
        }
    }

    public E takeFirst() throws InterruptedException {
        lock.lock();
        try {
            E x;
            while ((x = innerRemoveFirst()) == null)
                notEmpty.await();
            return x;
        } finally {
            lock.unlock();
        }
    }

    public E takeLast() throws InterruptedException {
        lock.lock();
        try {
            E x;
            while ((x = innerRemoveLast()) == null)
                notEmpty.await();
            return x;
        } finally {
            lock.unlock();
        }
    }

    public E pollFirst(long timeout, TimeUnit unit)
            throws InterruptedException {
        long nanos = unit.toNanos(timeout);
        lock.lockInterruptibly();
        try {
            for (; ;) {
                E x = innerRemoveFirst();
                if (x != null)
                    return x;
                if (nanos <= 0)
                    return null;
                nanos = notEmpty.awaitNanos(nanos);
            }
        } finally {
            lock.unlock();
        }
    }

    public E pollLast(long timeout, TimeUnit unit)
            throws InterruptedException {
        long nanos = unit.toNanos(timeout);
        lock.lockInterruptibly();
        try {
            for (; ;) {
                E x = innerRemoveLast();
                if (x != null)
                    return x;
                if (nanos <= 0)
                    return null;
                nanos = notEmpty.awaitNanos(nanos);
            }
        } finally {
            lock.unlock();
        }
    }

    /**
     * @throws NoSuchElementException {@inheritDoc}
     */
    public E getFirst() {
        E x = peekFirst();
        if (x == null) throw new NoSuchElementException();
        return x;
    }

    /**
     * @throws NoSuchElementException {@inheritDoc}
     */
    public E getLast() {
        E x = peekLast();
        if (x == null) throw new NoSuchElementException();
        return x;
    }

    public E peekFirst() {
        lock.lock();
        try {
            return list.size() == 0 ? null : list.peekFirst();
        } finally {
            lock.unlock();
        }
    }

    public E peekLast() {
        lock.lock();
        try {
            return list.size() == 0 ? null : list.peekLast();
        } finally {
            lock.unlock();
        }
    }

    public boolean removeFirstOccurrence(Object o) {
        if (o == null) return false;
        lock.lock();
        try {
            for (Iterator<E> it = list.iterator(); it.hasNext();) {
                E e = it.next();
                if (o.equals(e)) {
                    it.remove();
                    return true;
                }
            }
            return false;
        } finally {
            lock.unlock();
        }
    }

    public boolean removeLastOccurrence(Object o) {
        if (o == null) return false;
        lock.lock();
        try {
            for (Iterator<E> it = list.descendingIterator(); it.hasNext();) {
                E e = it.next();
                if (o.equals(e)) {
                    it.remove();
                    return true;
                }
            }
            return false;
        } finally {
            lock.unlock();
        }
    }

    // BlockingQueue methods

    /**
     * Inserts the specified element to the deque unless it would
     * violate capacity restrictions.  When using a capacity-restricted deque,
     * it is generally preferable to use method {@link #offer(Object) offer}.
     * <p/>
     * <p>
This method is equivalent to {@link #addLast}.
     *
     * @throws IllegalStateException if the element cannot be added at this
     *                               time due to capacity restrictions
     * @throws NullPointerException  if the specified element is null
     */
    @Override
    public boolean add(E e) {
        addLast(e);
        return true;
    }

    /**
     * @throws NullPointerException if the specified element is null
     */
    public boolean offer(E e) {
        return offerLast(e);
    }

    /**
     * @throws NullPointerException {@inheritDoc}
     * @throws InterruptedException {@inheritDoc}
     */
    public void put(E e) throws InterruptedException {
        putLast(e);
    }

    /**
     * @throws NullPointerException {@inheritDoc}
     * @throws InterruptedException {@inheritDoc}
     */
    public boolean offer(E e, long timeout, TimeUnit unit)
            throws InterruptedException {
        return offerLast(e, timeout, unit);
    }

    /**
     * Retrieves and removes the head of the queue represented by this deque.
     * This method differs from {@link #poll poll} only in that it throws an
     * exception if this deque is empty.
     * <p/>
     * <p>
This method is equivalent to {@link #removeFirst() removeFirst}.
     *
     * @return the head of the queue represented by this deque
     * @throws NoSuchElementException if this deque is empty
     */
    @Override
    public E remove() {
        return removeFirst();
    }

    public E poll() {
        return pollFirst();
    }

    public E take() throws InterruptedException {
        return takeFirst();
    }

    public E poll(long timeout, TimeUnit unit) throws InterruptedException {
        return pollFirst(timeout, unit);
    }

    /**
     * Retrieves, but does not remove, the head of the queue represented by
     * this deque.  This method differs from {@link #peek peek} only in that
     * it throws an exception if this deque is empty.
     * <p/>
     * <p>
This method is equivalent to {@link #getFirst() getFirst}.
     *
     * @return the head of the queue represented by this deque
     * @throws NoSuchElementException if this deque is empty
     */
    @Override
    public E element() {
        return getFirst();
    }

    public E peek() {
        return peekFirst();
    }

    /**
     * Returns the number of additional elements that this deque can ideally
     * (in the absence of memory or resource constraints) accept without
     * blocking. This is always equal to the initial capacity of this deque
     * less the current <tt>size</tt> of this deque.
     * <p/>
     * <p>
Note that you cannot always tell if an attempt to insert
     * an element will succeed by inspecting <tt>remainingCapacity</tt>
     * because it may be the case that another thread is about to
     * insert or remove an element.
     */
    public int remainingCapacity() {
        lock.lock();
        try {
            return capacity - list.size();
        } finally {
            lock.unlock();
        }
    }

    /**
     * @throws UnsupportedOperationException {@inheritDoc}
     * @throws ClassCastException            {@inheritDoc}
     * @throws NullPointerException          {@inheritDoc}
     * @throws IllegalArgumentException      {@inheritDoc}
     */
    public int drainTo(Collection<? super E> c) {
        if (c==null)
            throw new NullPointerException();
        if (c.equals(this))
            throw new IllegalArgumentException();
        lock.lock();
        try {
            for (E e : list) {
                c.add(e);
            }
            int n = list.size();
            list.clear();
            notFull.signalAll();
            return n;
        } finally {
            lock.unlock();
        }
    }

    /**
     * @throws UnsupportedOperationException {@inheritDoc}
     * @throws ClassCastException            {@inheritDoc}
     * @throws NullPointerException          {@inheritDoc}
     * @throws IllegalArgumentException      {@inheritDoc}
     */
    public int drainTo(Collection<? super E> c, int maxElements) {
        if (c ==null)
            throw new NullPointerException();
        if (c.equals(this))
            throw new IllegalArgumentException();
        lock.lock();
        try {
            int n = 0;
            for (Iterator<E> it = list.iterator(); n < maxElements && it.hasNext();) {
                E e = it.next();
                c.add(e);
                it.remove();
                ++n;
            }

            notFull.signalAll();
            return n;
        } finally {
            lock.unlock();
        }
    }

    // Stack methods

    /**
     * @throws IllegalStateException {@inheritDoc}
     * @throws NullPointerException  {@inheritDoc}
     */
    public void push(E e) {
        addFirst(e);
    }

    /**
     * @throws NoSuchElementException {@inheritDoc}
     */
    public E pop() {
        return removeFirst();
    }

    // Collection methods

    /**
     * Removes the first occurrence of the specified element from this deque.
     * If the deque does not contain the element, it is unchanged.
     * More formally, removes the first element <tt>e</tt> such that
     * <tt>o.equals(e)</tt> (if such an element exists).
     * Returns <tt>true</tt> if this deque contained the specified element
     * (or equivalently, if this deque changed as a result of the call).
     * <p/>
     * <p>
This method is equivalent to
     * {@link #removeFirstOccurrence(Object) removeFirstOccurrence}.
     *
     * @param o element to be removed from this deque, if present
     * @return <tt>true</tt> if this deque changed as a result of the call
     */
    @Override
    public boolean remove(Object o) {
        return removeFirstOccurrence(o);
    }

    /**
     * Returns the number of elements in this deque.
     *
     * @return the number of elements in this deque
     */
    @Override
    public int size() {
        lock.lock();
        try {
            return list.size();
        } finally {
            lock.unlock();
        }
    }

    /**
     * Returns <tt>true</tt> if this deque contains the specified element.
     * More formally, returns <tt>true</tt> if and only if this deque contains
     * at least one element <tt>e</tt> such that <tt>o.equals(e)</tt>.
     *
     * @param o object to be checked for containment in this deque
     * @return <tt>true</tt> if this deque contains the specified element
     */
    @Override
    public boolean contains(Object o) {
        if (o == null) return false;
        lock.lock();
        try {
            return list.contains(o);
        } finally {
            lock.unlock();
        }
    }

    /**
     * Returns an array containing all of the elements in this deque, in
     * proper sequence (from first to last element).
     * <p/>
     * <p>
The returned array will be"safe" in that no references to it are
     * maintained by this deque.  (In other words, this method must allocate
     * a new array).  The caller is thus free to modify the returned array.
     * <p/>
     * <p>
This method acts as bridge between array-based and collection-based
     * APIs.
     *
     * @return an array containing all of the elements in this deque
     */
    @Override
    public Object[] toArray() {
        lock.lock();
        try {
            return list.toArray();
        } finally {
            lock.unlock();
        }
    }

    /**
     * Returns an array containing all of the elements in this deque, in
     * proper sequence; the runtime type of the returned array is that of
     * the specified array.  If the deque fits in the specified array, it
     * is returned therein.  Otherwise, a new array is allocated with the
     * runtime type of the specified array and the size of this deque.
     * <p/>
     * <p>
If this deque fits in the specified array with room to spare
     * (i.e., the array has more elements than this deque), the element in
     * the array immediately following the end of the deque is set to
     * <tt>null</tt>.
     * <p/>
     * <p>
Like the {@link #toArray()} method, this method acts as bridge between
     * array-based and collection-based APIs.  Further, this method allows
     * precise control over the runtime type of the output array, and may,
     * under certain circumstances, be used to save allocation costs.
     * <p/>
     * <p>
Suppose <tt>x</tt> is a deque known to contain only strings.
     * The following code can be used to dump the deque into a newly
     * allocated array of <tt>String</tt>:
     * <p/>
     * [cc lang="java"]
     *     String[] y = x.toArray(new String[0]);