/*
 * This file is subject to the terms of the GFX License. If a copy of
 * the license was not distributed with this file, you can obtain one at:
 *
 *              http://ugfx.io/license.html
 */

// We need to include stdio.h below. Turn off GFILE_NEED_STDIO just for this file to prevent conflicts
#define GFILE_NEED_STDIO_MUST_BE_OFF

#include "../../gfx.h"

#if GFX_USE_OS_LINUX

// Linux seems to have deprecated pthread_yield() and now says to use sched_yield()
#define		USE_SCHED_NOT_PTHREAD_YIELD		GFXON

#include <stdio.h>
#include <unistd.h>
#include <time.h>
#if USE_SCHED_NOT_PTHREAD_YIELD
	#include <sched.h>
	#define linuxyield()	sched_yield()
#else
	#define linuxyield()	pthread_yield()
#endif

static gMutex		SystemMutex;

void _gosInit(void)
{
	/* No initialization of the operating system itself is needed */
	gfxMutexInit(&SystemMutex);
}

void _gosPostInit(void)
{
}

void _gosDeinit(void)
{
	/* ToDo */
}

void gfxSystemLock(void) {
	gfxMutexEnter(&SystemMutex);
}

void gfxSystemUnlock(void) {
	gfxMutexExit(&SystemMutex);
}

void gfxYield(void) {
	linuxyield();
}

void gfxHalt(const char *msg) {
	if (msg)
		fprintf(stderr, "%s\n", msg);
	exit(1);
}

void gfxSleepMilliseconds(gDelay ms) {
	struct timespec	ts;

	switch(ms) {
		case gDelayNone:
			linuxyield();
			return;

		case gDelayForever:
			while(1)
				sleep(60);
			return;

		default:
			ts.tv_sec = ms / 1000;
			ts.tv_nsec = (ms % 1000) * 1000000;
			nanosleep(&ts, 0);
			return;
	}
}

void gfxSleepMicroseconds(gDelay us) {
	struct timespec	ts;

	switch(us) {
		case gDelayNone:
			linuxyield();
			return;

		case gDelayForever:
			while(1)
				sleep(60);
			return;

		default:
			ts.tv_sec = us / 1000000;
			ts.tv_nsec = (us % 1000000) * 1000;
			nanosleep(&ts, 0);
			return;
	}
}

gTicks gfxSystemTicks(void) {
	struct timespec	ts;

	clock_gettime(CLOCK_MONOTONIC, &ts);
	return ts.tv_sec * 1000 + ts.tv_nsec / 1000000;
}

gThread gfxThreadCreate(void *stackarea, gMemSize stacksz, gThreadpriority prio, GFX_THREAD_FUNCTION((*fn),p), void *param) {
	gThread		th;
	(void)				stackarea;
	(void)				stacksz;
	(void)				prio;

	// Implementing priority with pthreads is a rats nest that is also pthreads implementation dependent.
	// Only some pthreads schedulers support it, some implementations use the operating system process priority mechanisms.
	// Even those that do support it can have different ranges of priority and "normal" priority is an undefined concept.
	// Across different UNIX style operating systems things can be very different (let alone OS's such as Windows).
	// Even just Linux changes the way priority works with different kernel schedulers and across kernel versions.
	// For these reasons we ignore the priority.

	if (pthread_create(&th, 0, fn, param))
		return 0;

	return th;
}

gThreadreturn gfxThreadWait(gThread thread) {
	gThreadreturn	retval;

	if (pthread_join(thread, &retval))
		return 0;

	return retval;
}

#if GFX_USE_POSIX_SEMAPHORES
	void gfxSemInit(gSem *pSem, gSemcount val, gSemcount limit) {
		pSem->max = limit;
		sem_init(&pSem->sem, 0, val);
	}
	void gfxSemDestroy(gSem *pSem) {
		sem_destroy(&pSem->sem);
	}
	gBool gfxSemWait(gSem *pSem, gDelay ms) {
		switch (ms) {
		case gDelayForever:
			return sem_wait(&pSem->sem) ? gFalse : gTrue;

		case gDelayNone:
			return sem_trywait(&pSem->sem) ? gFalse : gTrue;

		default:
			{
				struct timespec	tm;

				clock_gettime(CLOCK_REALTIME, &tm);
				tm.tv_sec += ms / 1000;
				tm.tv_nsec += (ms % 1000) * 1000000;
				return sem_timedwait(&pSem->sem, &tm) ? gFalse : gTrue;
			}
		}
	}
	void gfxSemSignal(gSem *pSem) {
		int	res;

		res = 0;
		sem_getvalue(&pSem->sem, &res);
		if (res < pSem->max)
			sem_post(&pSem->sem);
	}
#else
	void gfxSemInit(gSem *pSem, gSemcount val, gSemcount limit) {
		pthread_mutex_init(&pSem->mtx, 0);
		pthread_cond_init(&pSem->cond, 0);
		pthread_mutex_lock(&pSem->mtx);
		pSem->cnt = val;
		pSem->max = limit;
		pthread_mutex_unlock(&pSem->mtx);
	}
	void gfxSemDestroy(gSem *pSem) {
		pthread_mutex_destroy(&pSem->mtx);
		pthread_cond_destroy(&pSem->cond);
	}
	gBool gfxSemWait(gSem *pSem, gDelay ms) {
		pthread_mutex_lock(&pSem->mtx);

		switch (ms) {
			case gDelayForever:
				while (!pSem->cnt)
					pthread_cond_wait(&pSem->cond, &pSem->mtx);
				break;

			case gDelayNone:
				if (!pSem->cnt) {
					pthread_mutex_unlock(&pSem->mtx);
					return gFalse;
				}
				break;

			default:
				{
					struct timespec	tm;

					clock_gettime(CLOCK_REALTIME, &tm);
					tm.tv_sec += ms / 1000;
					tm.tv_nsec += (ms % 1000) * 1000000;
					while (!pSem->cnt) {
						// We used to test the return value for ETIMEDOUT. This doesn't
						//	work in some current pthread libraries which return -1 instead
						//	and set errno to ETIMEDOUT. So, we will return gFalse on any error
						//	including a ETIMEDOUT.
						if (pthread_cond_timedwait(&pSem->cond, &pSem->mtx, &tm)) {
							pthread_mutex_unlock(&pSem->mtx);
							return gFalse;
						}
					}
				}
				break;
		}

		pSem->cnt--;
		pthread_mutex_unlock(&pSem->mtx);
		return gTrue;
	}
	void gfxSemSignal(gSem *pSem) {
		pthread_mutex_lock(&pSem->mtx);

		if (pSem->cnt < pSem->max) {
			pSem->cnt++;
			pthread_cond_signal(&pSem->cond);
		}

		pthread_mutex_unlock(&pSem->mtx);
	}
#endif // GFX_USE_POSIX_SEMAPHORES

#endif /* GFX_USE_OS_LINUX */