#include "LinkedBlockingQueue.h"

/* Destroy the linked blocking queue and associated mutex and event */
PLINKED_BLOCKING_QUEUE_ENTRY LbqDestroyLinkedBlockingQueue(PLINKED_BLOCKING_QUEUE queueHead) {
	PltDeleteMutex(&queueHead->mutex);
	PltCloseEvent(&queueHead->containsDataEvent);
	
	return queueHead->head;
}

/* Flush the queue */
PLINKED_BLOCKING_QUEUE_ENTRY LbqFlushQueueItems(PLINKED_BLOCKING_QUEUE queueHead) {
	PLINKED_BLOCKING_QUEUE_ENTRY head;
	
	PltLockMutex(&queueHead->mutex);

	// Save the old head
	head = queueHead->head;

	// Reinitialize the queue to empty
	queueHead->head = NULL;
	queueHead->tail = NULL;
	queueHead->currentSize = 0;
	PltClearEvent(&queueHead->containsDataEvent);

	PltUnlockMutex(&queueHead->mutex);

	return head;
}

/* Linked blocking queue init */
int LbqInitializeLinkedBlockingQueue(PLINKED_BLOCKING_QUEUE queueHead, int sizeBound) {
	int err;
	
	err = PltCreateEvent(&queueHead->containsDataEvent);
	if (err != 0) {
		return err;
	}

	err = PltCreateMutex(&queueHead->mutex);
	if (err != 0) {
		return err;
	}

	queueHead->head = NULL;
	queueHead->tail = NULL;
	queueHead->sizeBound = sizeBound;
	queueHead->currentSize = 0;

	return 0;
}

int LbqOfferQueueItem(PLINKED_BLOCKING_QUEUE queueHead, void* data, PLINKED_BLOCKING_QUEUE_ENTRY entry) {
	entry->flink = NULL;
	entry->data = data;

	PltLockMutex(&queueHead->mutex);

	if (queueHead->currentSize == queueHead->sizeBound) {
		PltUnlockMutex(&queueHead->mutex);
		return LBQ_BOUND_EXCEEDED;
	}

	if (queueHead->head == NULL) {
		LC_ASSERT(queueHead->currentSize == 0);
		LC_ASSERT(queueHead->tail == NULL);
		queueHead->head = entry;
		queueHead->tail = entry;
		entry->blink = NULL;
	}
	else {
		LC_ASSERT(queueHead->currentSize >= 1);
		LC_ASSERT(queueHead->head != NULL);
		queueHead->tail->flink = entry;
		entry->blink = queueHead->tail;
		queueHead->tail = entry;
	}

	queueHead->currentSize++;

	PltUnlockMutex(&queueHead->mutex);

	PltSetEvent(&queueHead->containsDataEvent);

	return LBQ_SUCCESS;
}

// This must be synchronized with LbqFlushQueueItems by the caller
int LbqPeekQueueElement(PLINKED_BLOCKING_QUEUE queueHead, void** data) {
    if (queueHead->head == NULL) {
        return LBQ_NO_ELEMENT;
    }
    
    PltLockMutex(&queueHead->mutex);
    
    if (queueHead->head == NULL) {
        PltUnlockMutex(&queueHead->mutex);
        return LBQ_NO_ELEMENT;
    }
    
    *data = queueHead->head->data;
    
    PltUnlockMutex(&queueHead->mutex);
    
    return LBQ_SUCCESS;
}

int LbqPollQueueElement(PLINKED_BLOCKING_QUEUE queueHead, void** data) {
    PLINKED_BLOCKING_QUEUE_ENTRY entry;
    
    if (queueHead->head == NULL) {
        return LBQ_NO_ELEMENT;
    }
    
    PltLockMutex(&queueHead->mutex);
    
    if (queueHead->head == NULL) {
        PltUnlockMutex(&queueHead->mutex);
        return LBQ_NO_ELEMENT;
    }
    
    entry = queueHead->head;
    queueHead->head = entry->flink;
    queueHead->currentSize--;
    if (queueHead->head == NULL) {
        LC_ASSERT(queueHead->currentSize == 0);
        queueHead->tail = NULL;
        PltClearEvent(&queueHead->containsDataEvent);
    }
    else {
        LC_ASSERT(queueHead->currentSize != 0);
        queueHead->head->blink = NULL;
    }
    
    *data = entry->data;
    
    PltUnlockMutex(&queueHead->mutex);
    
    return LBQ_SUCCESS;
}

int LbqWaitForQueueElement(PLINKED_BLOCKING_QUEUE queueHead, void** data) {
	PLINKED_BLOCKING_QUEUE_ENTRY entry;
	int err;

	for (;;) {
		err = PltWaitForEvent(&queueHead->containsDataEvent);
		if (err != PLT_WAIT_SUCCESS) {
			return LBQ_INTERRUPTED;
		}

		PltLockMutex(&queueHead->mutex);

		if (queueHead->head == NULL) {
			PltClearEvent(&queueHead->containsDataEvent);
			PltUnlockMutex(&queueHead->mutex);
			continue;
		}

		entry = queueHead->head;
		queueHead->head = entry->flink;
		queueHead->currentSize--;
		if (queueHead->head == NULL) {
			LC_ASSERT(queueHead->currentSize == 0);
			queueHead->tail = NULL;
			PltClearEvent(&queueHead->containsDataEvent);
		}
		else {
			LC_ASSERT(queueHead->currentSize != 0);
			queueHead->head->blink = NULL;
		}

		*data = entry->data;

		PltUnlockMutex(&queueHead->mutex);

		break;
	}

	return LBQ_SUCCESS;
}