#include "chirp.h"
#include <stdlib.h>
#include <string.h>
#include <SDL2/SDL.h>
//1 2 3 4 6 8 12 16 24 32
//f s   c   n    b     r

#define SILENCE 		128
#define	NOISE			129

#define AUDIO_NONE		0
#define AUDIO_PLAY		1

#define MAX_CHANNELS	5

typedef void (*waveform_t)(const uint16_t, const uint32_t, uint8_t*);
waveform_t waveforms[1];

const static uint16_t lengths[10] = { 313, 625, 938, 1250, 1875, 2500, 3750, 5000, 7500, 10000 };
const static uint16_t tempos[10] = { 13230, 8820, 6615, 5292, 4410, 3780, 3308, 2940, 2646, 2406 };
const float periods[108] = { 1348.49207, 1272.80688, 1201.37, 1133.94214, 1070.29871, 1010.22772, 953.527893, 900.010376, 849.496887, 801.818176, 756.815613, 714.338745, 674.246033, 636.403564, 600.684875, 566.971069, 535.149475, 505.11377, 476.763947, 450.005249, 424.748352, 400.909088, 378.407806, 357.169373, 337.123016, 318.201782, 300.342438, 283.485535, 267.574738, 252.556885, 238.381973, 225.002625, 212.374176, 200.454544, 189.203888, 178.584702, 168.561508, 159.100876, 150.171234, 141.742767, 133.787354, 126.278458, 119.190987, 112.501305, 106.187096, 100.227272, 94.6019516, 89.2923508, 84.2807541, 79.5504379, 75.0856171, 70.8713837, 66.8936768, 63.139225, 59.5954933, 56.2506561, 53.0935478, 50.113636, 47.3009758, 44.6461754, 42.140377, 39.775219, 37.5428085, 35.4356918, 33.4468384, 31.5696125, 29.7977467, 28.1253281, 26.5467739, 25.056818, 23.650486, 22.3230877, 21.0701885, 19.8876095, 18.7714043, 17.7178459, 16.7234192, 15.7848072, 14.8988733, 14.0626631, 13.273387, 12.528409, 11.8252439, 11.1615429, 10.5350943, 9.94380569, 9.38570118, 8.85892296, 8.36171055, 7.89240265, 7.44943666, 7.03133202, 6.636693, 6.2642045, 5.91262197, 5.58077145, 5.26754713, 4.97190285, 4.69285059, 4.42946148, 4.18085527, 3.94620132, 3.72471833, 3.51566601, 3.3183465, 3.13210225, 2.95631051, 2.7903862 };

SDL_AudioDeviceID audio_device;
uint8_t audio_state = AUDIO_NONE;

struct channel_t {
	char* 		song 		= NULL;
	char* 		song_ptr 	= NULL;
	float		length 		= 0.25f;
	uint8_t 	volume 		= 32;
	uint8_t 	octave 		= 4;
	uint32_t	tempo 		= 44100;
	uint8_t 	waveform 	= 0;
	Uint8* 		play_pos;
	Uint32 		play_len;
	Uint8 		play_buffer[132300];
};
channel_t channels[MAX_CHANNELS];

static float default_length = 0.25f;
static uint8_t volume = 32;
static uint8_t octave = 4;
static uint32_t tempo = 44100;
static uint8_t waveform = 0;
static char* song_ptr = NULL;
static char* song = NULL;

static Uint8* play_pos;
static Uint32 play_len;
static Uint8 play_buffer[132300];



void audioCallback(void * userdata, uint8_t * stream, int len) {
    if (audio_state == AUDIO_PLAY) {
    	while( len > 0 ) {
		    while( play_len == 0 ) {
			    play_len = interpret_next_token(play_buffer);
			    if (play_len == -1) { audio_state=AUDIO_NONE; if (song != NULL) {free(song);song=NULL;}; SDL_memset( stream, 0, len ); return; }
			    play_pos = play_buffer;
		    }
		    const int actual_len = ( len > play_len ? play_len : len );
		    //SDL_memset( stream, 0, actual_len );
		    //SDL_MixAudio( stream, audio_pos, actual_len, SDL_MIX_MAXVOLUME );
            SDL_memcpy(stream, play_pos, actual_len);

		    stream += actual_len;
		    play_pos += actual_len;
		    play_len -= actual_len;
		    len -= actual_len;
	    }
    } else {
        SDL_memset(stream, 0, len);
    }
}

void square_waveform(const uint16_t period, const uint32_t length, uint8_t *buffer) {
	for( int i = 0; i < length; i++ ) buffer[i] = ( (i % period) < (period >> 1) ? volume : -volume );
}
void saw_waveform(const uint16_t period, const uint32_t length, uint8_t *buffer) {
	for( int i = 0; i < length; i++ ) buffer[i] = -volume + uint16_t( float(i % period) / float(period) * volume*2 );
}
void triangle_waveform(const uint16_t period, const uint32_t length, uint8_t *buffer) {
	for( int i = 0; i < length; i++ ) {
		uint16_t pos = i % period;
		uint16_t half_period = period >> 1;
		if (pos < half_period) {
			buffer[i] = -volume + uint16_t( (float(pos) / float(half_period)) * float(volume*2) );
		} else {
			buffer[i] = volume - uint16_t( (float(pos-half_period) / float(half_period)) * float(volume*2) );
		}
	}
}
void pulse12_waveform(const uint16_t period, const uint32_t length, uint8_t *buffer) {
	for( int i = 0; i < length; i++ ) buffer[i] = ( (i % period) < (period >> 3) ? volume : -volume );
}
void pulse25_waveform(const uint16_t period, const uint32_t length, uint8_t *buffer) {
	for( int i = 0; i < length; i++ ) buffer[i] = ( (i % period) < (period >> 2) ? volume : -volume );
}
void pulse75_waveform(const uint16_t period, const uint32_t length, uint8_t *buffer) {
	for( int i = 0; i < length; i++ ) buffer[i] = ( (i % period) < (period-(period >> 2)) ? volume : -volume );
}

void chirp_init() {
    SDL_AudioSpec audioSpec = {22050, AUDIO_S8, 1, 0, 512, 0, 0, audioCallback, NULL};
    audio_device = SDL_OpenAudioDevice(NULL, 0, &audioSpec, NULL, 0);
    SDL_PauseAudioDevice(audio_device, 0);
	waveforms[0] = &square_waveform;
	waveforms[1] = &saw_waveform;
	waveforms[2] = &triangle_waveform;
	waveforms[3] = &pulse12_waveform;
	waveforms[4] = &pulse25_waveform;
	waveforms[5] = &pulse75_waveform;
}

uint32_t interpret_note(uint8_t* buffer, const char note, const char param ) {
	const uint32_t length = ( param == -1 ? default_length : ((float)lengths[param])/10000.0f ) * tempo;
	if( note == SILENCE ) { memset( buffer, 0, length ); return length; }
	if( note == NOISE ) { for( int i = 0; i < length; i++ ) buffer[i] = rand()%2==0 ? volume : -volume; return length; }

	const uint16_t period = periods[note + octave*12];
	waveforms[waveform](period, length, buffer);
	return length;
}

void chirp_play(const char* new_song) {
    play_pos = play_buffer;
	play_len = 0;

	volume=32;
	octave=4;
	tempo=44100;
    if (song != NULL) free(song);
	song = (char*)malloc( strlen( new_song ) + 1 );
	strcpy( song, new_song );
    song_ptr = song;

    audio_state = AUDIO_PLAY;
}

int32_t interpret_next_token(uint8_t* buffer) {
    char** token = &song_ptr;
	char note = 0;
	char param = -1;
	
	switch( **token ) {
		case 'b': note += 2;
		case 'a': note += 2;
		case 'g': note += 2;
		case 'f': note += 1;
		case 'e': note += 2;
		case 'd': note += 2;
		case 'c':
			param = *++*token;
			if( param == '#' || param == '+' ) { note++; param = *++*token; } else if( param == '-' ) { note--; param = *++*token; }
			if( param >= 48 && param <= 57 ) { param -= 48; ++*token; } else { param = -1; }
			return interpret_note( buffer, note, param );
		case 'r':
			param = *++*token;
			if( param >= 48 && param <= 57 ) { param -= 48; ++*token; } else { param = -1; }
			return interpret_note( buffer, SILENCE, param );
		case 'n':
			param = *++*token;
			if( param >= 48 && param <= 57 ) { param -= 48; ++*token; } else { param = -1; }
			return interpret_note( buffer, NOISE, param );
		case 'o':
			param = *++*token;
			if( param >= 48 && param <= 57 ) { octave = (param - 48) % 8; ++*token; }
			return 0;
		case '>':
			octave = (octave+1) % 8; ++*token;
			return 0;
		case '<':
			octave = (octave-1) % 8; ++*token;
			return 0;
		case 'l':
			param = *++*token;
			if( param >= 48 && param <= 57 ) { default_length = ((float)lengths[param - 48])/10000.0f; ++*token; }
			return 0;
		case 'v':
			param = *++*token;
			if( param >= 48 && param <= 57 ) { volume = (param - 48) << 3; ++*token; }
			return 0;
		case 't':
			param = *++*token;
			if( param >= 48 && param <= 57 ) { tempo = tempos[param - 48] * 10; ++*token; }
			return 0;
		case 'w':
			param = *++*token;
			if( param >= 48 && param <= 57 ) { waveform = param - 48; ++*token; }
			return 0;
		case '=':
			song_ptr = song;
			return 0;
		case '\0':
			return -1;
		default:
			++*token;
			return 0;
	};
}

void chirp_stop() {
	if (song != NULL) {
		free(song);
		song=NULL;
	}
	audio_state=AUDIO_NONE;
}