#include <stdlib.h>
#include <string.h>
#include <math.h>
#include <plibsys.h>
#include "channel.h"


void channel_init(struct channel_t *chan)
{
	chan->active = false;
	chan->paused = false;
	chan->volume = 255;
	chan->pan_left = -128;
	chan->pan_right = 128;

	chan->sound_mutex = p_mutex_new();
	chan->sound.left = NULL;
	chan->sound.right = NULL;
	chan->pos = 0;
}


void channel_reset(struct channel_t *chan)
{
	p_atomic_int_set(&(chan->paused), false);
	p_atomic_int_set(&(chan->volume), 255);
	p_atomic_int_set(&(chan->pan_left), -128);
	p_atomic_int_set(&(chan->pan_right), 128);
	chan->pos = 0;
	p_atomic_int_set(&(chan->active), false);
}


void channel_pause(struct channel_t *chan)
{
	p_atomic_int_set(&(chan->paused), true);
}


void channel_resume(struct channel_t *chan)
{
	p_atomic_int_set(&(chan->paused), false);
}


void channel_set_volume(struct channel_t *chan, float volume)
{
	if (volume > 1.0f) volume = 1.0f;
	if (volume < 0.0f) volume = 0.0f;

	p_atomic_int_set(&(chan->volume), 255*volume);
}


void channel_set_pan(struct channel_t *chan, float pan_left, float pan_right)
{
	if (pan_left > 1.0f) pan_left = 1.0f;
	if (pan_left < -1.0f) pan_left = -1.0f;

	if (pan_right > 1.0f) pan_right = 1.0f;
	if (pan_right < -1.0f) pan_right = -1.0f;

	p_atomic_int_set(&(chan->pan_left), 128*pan_left);
	p_atomic_int_set(&(chan->pan_right), 128*pan_right);
}


#define QUARTER_PI 0.785397
static void pan_gain(float *gain_l, float *gain_r, float pan)
{
	float theta = (QUARTER_PI * pan) + QUARTER_PI; /* 0-PI/2 */
	*gain_l = cos(theta);
	*gain_r = sin(theta);
}


void channel_get_next_sample(float *left, float *right, struct channel_t *chan)
{
	bool active = p_atomic_int_get(&(chan->active));
	bool paused = p_atomic_int_get(&(chan->paused));
	if (!active || paused) {
		/* skip this channel */
		*left = 0;
		*right = 0;
		return;
	}

	if (!p_mutex_trylock(chan->sound_mutex)) {
		/* can't lock mutex, skip */
		*left = 0;
		*right = 0;
		return;
	}

	float volume = ((float)p_atomic_int_get(&(chan->volume)))/255;

	if (chan->sound.mono) {
		float x = chan->sound.left[chan->pos];
		float pan = ((float)p_atomic_int_get(&(chan->pan_left)))/128;
		float gain_l, gain_r;
		pan_gain(&gain_l, &gain_r, pan);
		*left = volume * gain_l * x;
		*right = volume * gain_r * x;
	}
	else {
		float l, r;
		l = chan->sound.left[chan->pos];
		r = chan->sound.right[chan->pos];

		float pan_l = ((float)p_atomic_int_get(&(chan->pan_left)))/128;
		float pan_r = ((float)p_atomic_int_get(&(chan->pan_right)))/128;
		float gain_ll, gain_lr, gain_rl, gain_rr;
		pan_gain(&gain_ll, &gain_lr, pan_l);
		pan_gain(&gain_rl, &gain_rr, pan_r);

		*left = volume * ((gain_ll * l) + (gain_rl * r));
		*right = volume * ((gain_lr * l) + (gain_rr * r));
	}

	chan->pos += 1;

	if (chan->pos >= chan->sound.len) {
		channel_reset(chan);
	}

	p_mutex_unlock(chan->sound_mutex);
}