#include "csapp.h"
#include "taskq.h"

/* Create and reap queue of tasks */
task_queue_ptr new_task_queue() {
    task_queue_ptr tq = Malloc(sizeof(task_queue_t));
    tq->active_count = tq->max_active_count = 0;
    tq->head = tq->tail = NULL;
    pthread_mutex_init(&tq->mutex, NULL);
#ifdef SEM
    sem_init(&tq->reap_ok, 0, 0);
#endif
    return tq;
}


void free_task_queue(task_queue_ptr tq) {
    /* Assumes that queue is already empty */
    free((void *) tq);
}

/* Create a new task, spawning thread.  Return nonzero if successful */
void spawn_task(task_queue_ptr tq, thread_routine_t routine, void *tdata) {
    int first_task = 0;
    /* Create new task element */
    task_list_ptr ele = Malloc(sizeof(task_list_t));
    ele->next = NULL;
    /* Acquire lock to queue state */
    pthread_mutex_lock(&tq->mutex);
    first_task = tq->max_active_count == 0;
    if (tq->tail)
	tq->tail->next = ele;
    else
	tq->head = ele;
    tq->tail = ele;
    tq->active_count++;
    if (tq->active_count > tq->max_active_count)
	tq->max_active_count = tq->active_count;
    Pthread_create(&ele->tid, NULL, routine, tdata);
#ifdef SEM
    if (first_task)
	sem_post(&tq->reap_ok);
#endif
    pthread_mutex_unlock(&tq->mutex);
}



/* Join all tasks in queue.  Won't return until queue becomes empty.
   Returns maximum number of concurrrent tasks
*/
int join_tasks(task_queue_ptr tq) {
#ifdef SEM
    /*
      This may be needed at the very beginning
      in case no tasks have been queued yet
    */
    P(&tq->reap_ok);
#endif
    /* Basic loop:
       Assumes that queue won't become empty until all tasks completed. */
    while (1) {
	pthread_mutex_lock(&tq->mutex);
	task_list_ptr old_head = tq->head;
	if (old_head == NULL) {
	    pthread_mutex_unlock(&tq->mutex);
	    return tq->max_active_count;
	} else {
	    pthread_t tid = old_head->tid;
	    tq->head = old_head->next;
	    if (old_head == tq->tail)
		tq->tail = NULL;
	    tq->active_count--;
	    pthread_mutex_unlock(&tq->mutex);
	    free((void *) old_head);
	    Pthread_join(tid, NULL);
	}
    }
}