#include "itc.h"

void itc_chan_create(itc_chan *chan)
{
	memset(chan, 0, sizeof(itc_chan));

	chan->mutex = SDL_CreateMutex();
	assert(chan->mutex);

	chan->sem = SDL_CreateSemaphore(0);
	assert(chan->sem);
}

void itc_chan_destroy(itc_chan *chan)
{
	// todo: free queue

	SDL_DestroySemaphore(chan->sem);
	SDL_DestroyMutex(chan->mutex);
}

void itc_chan_push(itc_chan *chan, int number, void *data)
{
	itc_message *msg;

	msg = calloc(1, sizeof(itc_message));
	assert(msg);

	msg->number = number;
	msg->data = data;

	SDL_LockMutex(chan->mutex);
	
	if (!chan->oldest) {      
		chan->oldest = msg;
		chan->newest = msg;
	} else {
		/*
		 *   head <---> ... <---> tail
		 *
		 */

		chan->newest->newer = msg;
		msg->older = chan->newest;
		chan->newest = msg;
	}

	SDL_SemPost(chan->sem);
	SDL_UnlockMutex(chan->mutex);
}

int itc_chan_pop(itc_chan *chan, int *number, void **data)
{
	itc_message *msg;

	SDL_LockMutex(chan->mutex);

	if (!chan->oldest) {
		SDL_UnlockMutex(chan->mutex);
		return 1;
	}

	msg = chan->oldest;

	if (msg->newer) {
		msg->newer->older = NULL;
		chan->oldest = msg->newer;
	} else {
		chan->newest = NULL;
		chan->oldest = NULL;
	}

	SDL_SemWait(chan->sem); // should be instant
	SDL_UnlockMutex(chan->mutex);

	*number = msg->number;
	*data = msg->data;
	free(msg);

	return 0;
}

int itc_chan_pop_block(itc_chan *chan, int *number, void **data)
{
	itc_message *msg;

	SDL_SemWait(chan->sem);
	SDL_LockMutex(chan->mutex);

	if (!chan->oldest) {
		SDL_UnlockMutex(chan->mutex);
		return 1;
	}

	msg = chan->oldest;

	if (msg->newer) {
		msg->newer->older = NULL;
		chan->oldest = msg->newer;
	} else {
		chan->newest = NULL;
		chan->oldest = NULL;
	}

	SDL_UnlockMutex(chan->mutex);

	*number = msg->number;
	*data = msg->data;
	free(msg);

	return 0;
}