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/*
SDL - Simple DirectMedia Layer
Copyright (C) 1997-2009 Sam Lantinga

This library is free software; you can redistribute it and/or
modify it under the terms of the GNU Lesser General Public
License as published by the Free Software Foundation; either
version 2.1 of the License, or (at your option) any later version.

This library is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
Lesser General Public License for more details.

You should have received a copy of the GNU Lesser General Public
License along with this library; if not, write to the Free Software
Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA

Sam Lantinga
slouken@libsdl.org
*/
#include "SDL_config.h"

#include "SDL_timer.h"
#include "SDL_timer_c.h"
#include "SDL_mutex.h"
#include "SDL_systimer.h"

/* #define DEBUG_TIMERS */

int SDL_timer_started = 0;
int SDL_timer_running = 0;

/* Data to handle a single periodic alarm */
Uint32 SDL_alarm_interval = 0;
SDL_TimerCallback SDL_alarm_callback;

/* Data used for a thread-based timer */
static int SDL_timer_threaded = 0;

struct _SDL_TimerID {
Uint32 interval;
SDL_NewTimerCallback cb;
void *param;
Uint32 last_alarm;
struct _SDL_TimerID *next;
};

static SDL_TimerID SDL_timers = NULL;
static SDL_mutex *SDL_timer_mutex;
static volatile SDL_bool list_changed = SDL_FALSE;

/* Set whether or not the timer should use a thread.
This should not be called while the timer subsystem is running.
*/
int SDL_SetTimerThreaded(int value)
{
int retval;

if ( SDL_timer_started ) {
SDL_SetError("Timer already initialized");
retval = -1;
} else {
retval = 0;
SDL_timer_threaded = value;
}
return retval;
}

int SDL_TimerInit(void)
{
int retval;

retval = 0;
if ( SDL_timer_started ) {
SDL_TimerQuit();
}
if ( ! SDL_timer_threaded ) {
retval = SDL_SYS_TimerInit();
}
if ( SDL_timer_threaded ) {
SDL_timer_mutex = SDL_CreateMutex();
}
if ( retval == 0 ) {
SDL_timer_started = 1;
}
return(retval);
}

void SDL_TimerQuit(void)
{
SDL_SetTimer(0, NULL);
if ( SDL_timer_threaded < 2 ) {
SDL_SYS_TimerQuit();
}
if ( SDL_timer_threaded ) {
SDL_DestroyMutex(SDL_timer_mutex);
SDL_timer_mutex = NULL;
}
SDL_timer_started = 0;
SDL_timer_threaded = 0;
}

void SDL_ThreadedTimerCheck(void)
{
Uint32 now, ms;
SDL_TimerID t, prev, next;
SDL_bool removed;

SDL_mutexP(SDL_timer_mutex);
list_changed = SDL_FALSE;
now = SDL_GetTicks();
for ( prev = NULL, t = SDL_timers; t; t = next ) {
removed = SDL_FALSE;
ms = t->interval - SDL_TIMESLICE;
next = t->next;
if ( (int)(now - t->last_alarm) > (int)ms ) {
struct _SDL_TimerID timer;

if ( (now - t->last_alarm) < t->interval ) {
t->last_alarm += t->interval;
} else {
t->last_alarm = now;
}
#ifdef DEBUG_TIMERS
printf("Executing timer %p (thread = %d)\n",
t, SDL_ThreadID());
#endif
timer = *t;
SDL_mutexV(SDL_timer_mutex);
ms = timer.cb(timer.interval, timer.param);
SDL_mutexP(SDL_timer_mutex);
if ( list_changed ) {
/* Abort, list of timers modified */
/* FIXME: what if ms was changed? */
break;
}
if ( ms != t->interval ) {
if ( ms ) {
t->interval = ROUND_RESOLUTION(ms);
} else {
/* Remove timer from the list */
#ifdef DEBUG_TIMERS
printf("SDL: Removing timer %p\n", t);
#endif
if ( prev ) {
prev->next = next;
} else {
SDL_timers = next;
}
SDL_free(t);
--SDL_timer_running;
removed = SDL_TRUE;
}
}
}
/* Don't update prev if the timer has disappeared */
if ( ! removed ) {
prev = t;
}
}
SDL_mutexV(SDL_timer_mutex);
}

static SDL_TimerID SDL_AddTimerInternal(Uint32 interval, SDL_NewTimerCallback callback, void *param)
{
SDL_TimerID t;
t = (SDL_TimerID) SDL_malloc(sizeof(struct _SDL_TimerID));
if ( t ) {
t->interval = ROUND_RESOLUTION(interval);
t->cb = callback;
t->param = param;
t->last_alarm = SDL_GetTicks();
t->next = SDL_timers;
SDL_timers = t;
++SDL_timer_running;
list_changed = SDL_TRUE;
}
#ifdef DEBUG_TIMERS
printf("SDL_AddTimer(%d) = %08x num_timers = %d\n", interval, (Uint32)t, SDL_timer_running);
#endif
return t;
}

SDL_TimerID SDL_AddTimer(Uint32 interval, SDL_NewTimerCallback callback, void *param)
{
SDL_TimerID t;
if ( ! SDL_timer_mutex ) {
if ( SDL_timer_started ) {
SDL_SetError("This platform doesn't support multiple timers");
} else {
SDL_SetError("You must call SDL_Init(SDL_INIT_TIMER) first");
}
return NULL;
}
if ( ! SDL_timer_threaded ) {
SDL_SetError("Multiple timers require threaded events!");
return NULL;
}
SDL_mutexP(SDL_timer_mutex);
t = SDL_AddTimerInternal(interval, callback, param);
SDL_mutexV(SDL_timer_mutex);
return t;
}

SDL_bool SDL_RemoveTimer(SDL_TimerID id)
{
SDL_TimerID t, prev = NULL;
SDL_bool removed;

removed = SDL_FALSE;
SDL_mutexP(SDL_timer_mutex);
/* Look for id in the linked list of timers */
for (t = SDL_timers; t; prev=t, t = t->next ) {
if ( t == id ) {
if(prev) {
prev->next = t->next;
} else {
SDL_timers = t->next;
}
SDL_free(t);
--SDL_timer_running;
removed = SDL_TRUE;
list_changed = SDL_TRUE;
break;
}
}
#ifdef DEBUG_TIMERS
printf("SDL_RemoveTimer(%08x) = %d num_timers = %d thread = %d\n", (Uint32)id, removed, SDL_timer_running, SDL_ThreadID());
#endif
SDL_mutexV(SDL_timer_mutex);
return removed;
}

/* Old style callback functions are wrapped through this */
static Uint32 SDLCALL callback_wrapper(Uint32 ms, void *param)
{
SDL_TimerCallback func = (SDL_TimerCallback) param;
return (*func)(ms);
}

int SDL_SetTimer(Uint32 ms, SDL_TimerCallback callback)
{
int retval;

#ifdef DEBUG_TIMERS
printf("SDL_SetTimer(%d)\n", ms);
#endif
retval = 0;

if ( SDL_timer_threaded ) {
SDL_mutexP(SDL_timer_mutex);
}
if ( SDL_timer_running ) { /* Stop any currently running timer */
if ( SDL_timer_threaded ) {
while ( SDL_timers ) {
SDL_TimerID freeme = SDL_timers;
SDL_timers = SDL_timers->next;
SDL_free(freeme);
}
SDL_timer_running = 0;
list_changed = SDL_TRUE;
} else {
SDL_SYS_StopTimer();
SDL_timer_running = 0;
}
}
if ( ms ) {
if ( SDL_timer_threaded ) {
if ( SDL_AddTimerInternal(ms, callback_wrapper, (void *)callback) == NULL ) {
retval = -1;
}
} else {
SDL_timer_running = 1;
SDL_alarm_interval = ms;
SDL_alarm_callback = callback;
retval = SDL_SYS_StartTimer();
}
}
if ( SDL_timer_threaded ) {
SDL_mutexV(SDL_timer_mutex);
}

return retval;
}
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