#include <stdlib.h>

#include "dataq.h"

int dataq_init(dataq_t* q, data_item_killer_t killer)
{
    q->head = q->tail = NULL;
    q->killer         = killer;
    mylock_init(&(q->lock));
    return 0;
}

static data_item_t* dataq_deq_head(dataq_t* q)
{
    if (q->head != NULL) {
        data_item_t* b = NULL;
        b              = q->head;
        q->head        = b->next;
        b->next        = NULL;
        if (q->head == NULL) {
            q->tail = NULL;
        }

        return b;
    }

    return NULL;
}

static data_item_t* dataq_deq_first_match(dataq_t* q, data_item_match_fn_t f)
{
    data_item_t* prev = NULL;
    data_item_t* curr = q->head;

    while (curr != NULL) {
        if ((*f)(curr)) { // Found the item to remove
            if (prev == NULL) {
                // Removing the head item
                q->head = curr->next;
                if (q->head == NULL) {
                    // Queue became empty after removing head
                    q->tail = NULL;
                }
                // else: tail remains unchanged (it wasn't the head)
            } else {
                // Removing an item after prev (middle or tail)
                prev->next = curr->next;
                if (curr == q->tail) { // Check if we are removing the tail
                    // We removed the tail item, prev is the new tail
                    q->tail = prev;
                }
                // else: tail remains unchanged (it was further down the list)
            }
            curr->next = NULL; // Isolate the removed item
            return curr;       // Return the removed item
        }
        // Move to the next item
        prev = curr;
        curr = curr->next;
    }

    return NULL;
}

data_item_t* dataq_deq(dataq_t* q, data_item_match_fn_t f)
{
    data_item_t* b = NULL;

    mylock_lock(&(q->lock));
    if (f == NULL) {
        b = dataq_deq_head(q);
    } else {
        b = dataq_deq_first_match(q, f);
    }

    mylock_unlock(&(q->lock));

    return b;
}

int dataq_enq(dataq_t* q, data_item_t* b)
{
    int rc = 0;

    b->next = NULL;

    mylock_lock(&(q->lock));
    if (q->tail != NULL) {
        q->tail->next = b;
    }

    if (q->head == NULL) {
        q->head = b;
    }

    q->tail = b;
    mylock_unlock(&(q->lock));

    return rc;
}

void dataq_fini(dataq_t* q)
{
    data_item_t* it;
    while ((it = dataq_deq_head(q)) != NULL) {
        if (q->killer != NULL) {
            (q->killer)(it);
        }
        // Note: dataq_deq_head already isolates 'it' (it->next = NULL)
    }

    q->head = q->tail = NULL; // Explicitly set just in case.
    q->killer         = NULL;

    return;
}