/*
 * The MIT License
 *
 * Copyright (C) 2017 Alexander Saprykin <saprykin.spb@gmail.com>
 *
 * Permission is hereby granted, free of charge, to any person obtaining
 * a copy of this software and associated documentation files (the
 * 'Software'), to deal in the Software without restriction, including
 * without limitation the rights to use, copy, modify, merge, publish,
 * distribute, sublicense, and/or sell copies of the Software, and to
 * permit persons to whom the Software is furnished to do so, subject to
 * the following conditions:
 *
 * The above copyright notice and this permission notice shall be
 * included in all copies or substantial portions of the Software.
 *
 * THE SOFTWARE IS PROVIDED 'AS IS', WITHOUT WARRANTY OF ANY KIND,
 * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
 * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.
 * IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY
 * CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT,
 * TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE
 * SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
 */

#include "patomic.h"
#include "pmem.h"
#include "pcondvariable.h"

#include <stdlib.h>

#define INCL_DOSSEMAPHORES
#define INCL_DOSERRORS
#include <os2.h>

struct PCondVariable_ {
	HEV	waiters_sema;
	pint	waiters_count;
	pint	signaled;
};

P_LIB_API PCondVariable *
p_cond_variable_new (void)
{
	PCondVariable *ret;

	if (P_UNLIKELY ((ret = p_malloc0 (sizeof (PCondVariable))) == NULL)) {
		P_ERROR ("PCondVariable::p_cond_variable_new: failed to allocate memory");
		return NULL;
	}

	if (P_UNLIKELY (DosCreateEventSem (NULL,
					   (PHEV) &ret->waiters_sema,
					   0,
					   FALSE) != NO_ERROR)) {
		P_ERROR ("PCondVariable::p_cond_variable_new: failed to initialize");
		p_free (ret);
		return NULL;
	}

	return ret;
}

P_LIB_API void
p_cond_variable_free (PCondVariable *cond)
{
	if (P_UNLIKELY (cond == NULL))
		return;

	if (P_UNLIKELY (DosCloseEventSem (cond->waiters_sema) != NO_ERROR))
		P_WARNING ("PCondVariable::p_cond_variable_free: DosCloseEventSem() failed");

	p_free (cond);
}

P_LIB_API pboolean
p_cond_variable_wait (PCondVariable	*cond,
		      PMutex		*mutex)
{
	APIRET ulrc;
	APIRET reset_ulrc;

	if (P_UNLIKELY (cond == NULL || mutex == NULL))
		return FALSE;

	do {
		p_atomic_int_inc (&cond->waiters_count);
		p_mutex_unlock (mutex);

		do {
			ULONG post_count;

			ulrc = DosWaitEventSem (cond->waiters_sema, SEM_INDEFINITE_WAIT);

			if (ulrc == NO_ERROR) {
				reset_ulrc = DosResetEventSem (cond->waiters_sema, &post_count);
				
				if (P_UNLIKELY (reset_ulrc != NO_ERROR &&
						reset_ulrc != ERROR_ALREADY_RESET))
					P_WARNING ("PCondVariable::p_cond_variable_wait: DosResetEventSem() failed");
			}
		} while (ulrc == NO_ERROR &&
			 p_atomic_int_compare_and_exchange (&cond->signaled, 1, 0) == FALSE);

		p_atomic_int_add (&cond->waiters_count, -1);
		p_mutex_lock (mutex);
	} while (ulrc == ERROR_INTERRUPT);

	return (ulrc == NO_ERROR) ? TRUE : FALSE;
}

P_LIB_API pboolean
p_cond_variable_signal (PCondVariable *cond)
{
	pboolean result = TRUE;

	if (P_UNLIKELY (cond == NULL))
		return FALSE;

	if (p_atomic_int_get (&cond->waiters_count) > 0) {
		ULONG	post_count;
		APIRET	ulrc;

		p_atomic_int_set (&cond->signaled, 1);

		ulrc = DosPostEventSem (cond->waiters_sema);

		if (P_UNLIKELY (ulrc != NO_ERROR &&
				ulrc != ERROR_ALREADY_POSTED &&
				ulrc != ERROR_TOO_MANY_POSTS)) {
			P_WARNING ("PCondVariable::p_cond_variable_signal: DosPostEventSem() failed");
			result = FALSE;
		}
	}

	return result;
}

P_LIB_API pboolean
p_cond_variable_broadcast (PCondVariable *cond)
{
	if (P_UNLIKELY (cond == NULL))
		return FALSE;

	pboolean result = TRUE;

	while (p_atomic_int_get (&cond->waiters_count) != 0) {
		if (P_UNLIKELY (p_cond_variable_signal (cond) == FALSE))
			result = FALSE;
	}

	return result;
}

void
p_cond_variable_init (void)
{
}

void
p_cond_variable_shutdown (void)
{
}