#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <math.h>

#define MSG(s) fprintf(stderr, "%s() %s L%d : %s\n", __func__, __FILE__, __LINE__, s)
#define ERR(s) do{ fprintf(stderr, "ERR "); MSG(s); exit(1); }while(0)

int bk_buf = -1;

int
rd(void)
{
	int v;

	if((v = bk_buf) < 0) return getchar();
	bk_buf = -1;
	return v;
}

void
bk(int v)
{
	if(bk_buf >= 0) ERR("give up");
	bk_buf = v;
}

void
rd_str(int n, char *s)
{
	int i;

	for(i=0; i<n; i++) s[i] = rd();
	s[i] = '\0';
}

int
rd_str_chk(int n, char *s)
{
	char buf[256];

	rd_str(n, buf);
	return strcmp(buf, s) == 0;
}

int
rd_int(int n) /* big endian */
{
	int i, v;

	v = 0;
	for(i=0; i<n; i++) v = (v << 8) | rd();
	return v;
}

int
rd_delta(void)
{
	int v, c;

	v = 0;
	do{
		if((c = rd()) == EOF) return EOF;
		v = (v << 7) | (c & 0x7f);
	}while(c & 0x80);
	return v;
}


#define NOTE_BUF_N	256

struct note_rec{
	int ch;
	int note;
	int onoff;
	double on_sec;
	double off_sec;
	int velo;
	double cycle, sec, freq;
	double off_v;
} note_buf[NOTE_BUF_N];

int
note_buf_is_free(int i)
{
	return note_buf[i].ch < 0;
}

void
note_buf_free(int i)
{
	note_buf[i].ch = -1;
}

void
note_buf_init(void)
{
	int i;

	for(i=0; i<NOTE_BUF_N; i++) note_buf_free(i);
}

int
note_buf_search(int ch, int note, int onoff)
{
	int i;

	for(i=0; i<NOTE_BUF_N; i++) {
		if( (ch < 0 && note_buf[i].ch < 0) ||
		    (note_buf[i].ch == ch &&
		     note_buf[i].note == note &&
		     note_buf[i].onoff == onoff) ) return i;
	}
	return -1;
}

int
header(void)
{
	int v;

	if(!rd_str_chk(4, "MThd")) ERR("header id");
	if(rd_int(4) != 6) ERR("header size");
	if(rd_int(2) != 0) ERR("header format type");
	if(rd_int(2) != 1) ERR("header track num");
	if((v = rd_int(2)) & 0x8000) ERR("header division");
	return v; /* div4 */
}

double
note_to_freq(int note)
{
	return 440 * pow(2, (note - 69) / 12.0);
}

int
opt_idx(char *key, int ac, char **av)
{
	int i;

	for(i=1; i<ac; i++) if(strcmp(av[i], key) == 0) return i;
	return -1;
}

char *
opt_str(char *key, int ac, char **av, char *def)
{
	int i;

	i = opt_idx(key, ac, av);
	if(i < 0 || i+1 >= ac) return def;
	return av[i+1];
}

int
opt_int(char *key, int ac, char **av, int def)
{
	char *s;

	if((s = opt_str(key, ac, av, NULL)) == NULL) return def;
	return strtol(s, NULL, 0);
}

struct out_rec{
	int smp_freq, smp_cnt;
	int bit_len;
	int sign;
	int ch_num;
	FILE *fp;

	int base;
	int amp;
	int iv_min;
	int iv_max;
};

void
out_init(struct out_rec *ot, int ac, char **av)
{
	char cmd[1024], *fn;

	ot->smp_freq = opt_int("-r", ac, av, 8000);
	ot->smp_cnt = 0;
	ot->bit_len = opt_int("-b", ac, av, 8);
	if(ot->bit_len != 8 && ot->bit_len != 16) ERR("bit_len");
	ot->sign = (opt_idx("-s", ac, av) >= 0);
	ot->ch_num = opt_int("-c", ac, av, 1);

	ot->fp = stdout;
	cmd[0] = '\0';
	fn = "";
	if(opt_idx("-play", ac, av) >= 0){
		strcat(cmd, "play");
	}else if(opt_idx("-sox", ac, av) >= 0){
		strcat(cmd, "sox");
		fn = opt_str("-sox", ac, av, "-d");
	}
	if(cmd[0]){
		sprintf(cmd + strlen(cmd), " -t raw -r %d -b %d %s -c %d - %s",
			ot->smp_freq, ot->bit_len,
			ot->sign ? "-s" : "-u",
			ot->ch_num, fn);
		if((ot->fp = popen(cmd, "w")) == NULL) ERR("popen");
	}
	ot->amp = ot->bit_len == 8 ? 127 : 32767;
	ot->base = ot->sign ? 0 : ot->amp + 1;
	ot->iv_min = ot->base - (ot->amp + 1);
	ot->iv_max = ot->base + ot->amp;
}

void
out_do(struct out_rec *ot, double v)
{
	int iv;

	iv = ot->base + (int)(v *ot->amp);
	if(iv > ot->iv_max) iv = ot->iv_max;
	if(iv < ot->iv_min) iv = ot->iv_min;
	switch(ot->bit_len){
	case 8:
		fputc(iv, ot->fp);
		break;
	case 16:
		fputc(iv & 0xff, ot->fp);
		fputc((iv >> 8) & 0xff, ot->fp);
		break;
	}
}

#define WAVE_SIN	0
#define WAVE_SAW	1
#define WAVE_SQUARE	2
#define WAVE_NOISE	3

double
wave_out(int wave, double cycle)
{
	cycle -= (int)cycle;

	switch(wave){
	case WAVE_SIN:
		return sin(2 * M_PI * cycle);
	case WAVE_SAW:
		cycle *= 2;
		if(cycle > 1) cycle -= 2;
		return cycle;
	case WAVE_SQUARE:
		return cycle < 0.5 ? 1 : -1;
	case WAVE_NOISE:
		return ((double)rand() / RAND_MAX) * 2 - 1;
	}
	return 0;
}

struct env_rec{
	double attack;	/* sec */
	double decay;	/* sec */
	double sustain;	/* 0..1 */
	double release;	/* sec */
};

void
env_set(struct env_rec *e, double a, double d, double s, double r)
{
	e->attack = a;
	e->decay = d;
	e->sustain = s;
	e->release = r;
}

struct tone_rec{
	int wave;
	struct env_rec env;
	double level;
} tone_inf[] = {
	{
		WAVE_SAW,
		{ 0.15, 0.5, 0.8, 0.5 },
		0.7
	},{
		WAVE_SAW,
		{ 0.05, 0.2, 0.4, 0.2 },
		0.7
	},{
		WAVE_SQUARE,
		{ 0.01, 0.2, 0.8, 0.3 },
		0.7
	},{
		WAVE_SIN,
		{ 0, 0.3, 0.2, 0.3 },
		1.0
	}
};

struct tone_rec *
tone_get(int prog)
{
	switch(prog){
	case 48: /* timpani */
	case 50: /* strings ensamble 2 */
		return &tone_inf[0];

	case 35: /* electric bass (pick) */
		return &tone_inf[1];

	case 79: /* whistle */
	case 81: /* lead 1 (square) */
	case 87: /* lead 7 (fifths) */
		return &tone_inf[2];

	case 24: /* tango accordion */
	case 67: /* tenor sax */
	default:
		break;
	}
	return &tone_inf[3];
}

#define MIDI_CH_N	16
struct ch_rec{
	int vol;
	int pan;
	int bend;
	int rpn;
	int bend_range;
	int prog;
} ch_inf[ MIDI_CH_N ];

#define CH_ENV(ch)	tone_get(ch_inf[ch].prog)->env

double
env_out(struct note_rec *nt)
{
	struct env_rec *e;
	double sec, v;

	sec = nt->sec;
	e = &CH_ENV(nt->ch);
	if(nt->onoff){
		sec -= nt->on_sec;
		if(sec < e->attack){
			v = sec / e->attack;
			return log10(1 + v * 9);
		}
		sec -= e->attack;
		if(sec < e->decay){
			v = sec / e->decay;
			v = log10(1 + v * 9);
			return 1 - v * (1 - e->sustain);
		}
		return e->sustain;
	}
	sec -= nt->off_sec;
	if(sec < e->release){
		v = sec / e->release;
		v = log10(1 + v * 9);
		return (1 - v) * nt->off_v;
	}
	return 0;
}

void
data_out(struct out_rec *ot, double evt_sec)
{
	double v, sec, freq, dsec;
	double vl, vr, pan;
	int i, nch;
	struct note_rec *nt;
	struct tone_rec *tn;

	while((sec = (double)ot->smp_cnt / ot->smp_freq) < evt_sec){
		vl = vr = 0;
		for(i=0; i<NOTE_BUF_N; i++){
			if(note_buf_is_free(i)) continue;
			nt = &note_buf[i];
			nch = nt->ch;
			freq = note_to_freq(nt->note);
			if(ch_inf[nch].bend != 0) freq *= pow(2, ch_inf[nch].bend / 8192.0 * ch_inf[nch].bend_range / 12);
			dsec = sec - nt->on_sec;
			if(dsec > 0.3) freq *= pow(2, sin(2 * M_PI * 6 * dsec) / (12 * 4) );
			nt->cycle += freq * (sec - nt->sec);
			nt->sec = sec;
			nt->freq = freq;
			tn = tone_get(ch_inf[nch].prog);
			v = wave_out(tn->wave, nt->cycle);
			v *= env_out(&note_buf[i]) * tn->level;
			v *= nt->velo / 127.0;
			v *= ch_inf[nch].vol / (double)((1<<14)-1);
			if(ot->ch_num == 1){
				vl += v;
			}else{
				pan = ch_inf[nch].pan / (double)(1<<14);
				vl += (1 - pan) * v;
				vr += pan * v;
			}
			if(nt->onoff == 0 && sec - nt->off_sec >= tn->env.release) note_buf_free(i);
		}
		out_do(ot, vl / 16);
		if(ot->ch_num > 1) out_do(ot, vr / 16);
		ot->smp_cnt++;
	}
}

void
note_onoff(int onoff, double evt_sec, int ch, int note, int velo)
{
	int i;

	if(ch == 9) return;

	if(onoff){
		if((i = note_buf_search(-1, -1, -1)) < 0){
			MSG("note_buf full");
			return;
		}
		note_buf[i].note = note;
		note_buf[i].ch = ch;
		note_buf[i].onoff = 1;
		note_buf[i].on_sec = evt_sec;
		note_buf[i].velo = velo;
		note_buf[i].cycle = 0;
		note_buf[i].sec = evt_sec;
	}else{
		if((i = note_buf_search(ch, note, 1)) < 0) return;
		note_buf[i].off_v = env_out(&note_buf[i]);
		note_buf[i].onoff = 0;
		note_buf[i].off_sec = evt_sec;
	}
}

void
msb_set(int *vp, int v)
{
	*vp &= ~(127<<7);
	*vp |= v<<7;
}

void
lsb_set(int *vp, int v)
{
	*vp &= ~127;
	*vp |= v;
}

void
bend_note_update(int ch, double sec)
{
	int i;
	struct note_rec *nt;

	for(i=0; i<NOTE_BUF_N; i++){
		if(note_buf_is_free(i)) continue;
		nt = &note_buf[i];
		if(nt->ch != ch) continue;
		nt->cycle += nt->freq * (sec - nt->sec);
		nt->sec = sec;
	}
}

int
main(int ac, char **av)
{
	int div4, delta_sum;
	int i, n, v, hi, low, note, velo;
	int ch, type;
	double sec;
	struct out_rec otr;
	int tempo, tempo_delta_sum;
	double tempo_sec;

	out_init(&otr, ac, av);
	note_buf_init();
	for(i=0; i<MIDI_CH_N; i++){
		ch_inf[i].vol = 0;
		ch_inf[i].pan = 1<<(14-1);
		ch_inf[i].bend = 0;
		ch_inf[i].rpn = 0;
		ch_inf[i].bend_range = 2;
		ch_inf[i].prog =-1;
	}
	tempo = 500000;
	tempo_delta_sum = 0;
	tempo_sec = 0;

	div4 = header();

	if(!rd_str_chk(4, "MTrk")) ERR("track id");
	v = rd_int(4); /* skip */

	hi = low = 0;
	delta_sum = 0;
	while((v = rd_delta()) != EOF){
		delta_sum += v;
		sec = tempo_sec + (double)(delta_sum - tempo_delta_sum) / div4 * tempo * 0.000001;
		
		if((v = rd()) & 0x80){
			hi = (v >> 4) & 0xf;
			low  = v & 0xf;
		}else bk(v);

		data_out(&otr, sec);

		ch = low;
		switch(hi){
		case 8:
		case 9:
			note = rd();
			velo = rd();
			note_onoff(hi == 9, sec, ch, note, velo);
			break;
		case 0xb: /* control change */
			type = rd();
			v = rd();
			switch(type){
			case 7: /* channel volume msb */
				msb_set(&ch_inf[ch].vol, v);
				break;
			case 39: /* channel volume lsb */
				lsb_set(&ch_inf[ch].vol, v);
				break;
			case 10: /* pan msb */
				msb_set(&ch_inf[ch].pan, v);
				break;
			case 42: /* pan lsb */
				lsb_set(&ch_inf[ch].pan, v);
				break;
			case 100: /* rpn lsb */
				lsb_set(&ch_inf[ch].rpn, v);
				break;
			case 101: /* rpn msb */
				msb_set(&ch_inf[ch].rpn, v);
				break;
			case 6: /* data entry msb */
				switch(ch_inf[ch].rpn){
				case 0: /* pitch bend range */
					ch_inf[ch].bend_range = v;
					break;
				}
				break;
			}
			break;
		case 0xa:
			rd();
			rd();
			break;
		case 0xe: /* pitch wheel change */
			bend_note_update(ch, sec);
			v = rd();
			v |= rd() << 7;
			ch_inf[ch].bend = v - 8192;
			break;
		case 0xc: /* program number */
			v = rd();
			ch_inf[ch].prog = v;
			break;
		case 0xd:
			rd();
			break;
		case 0xf:
			type = rd();
			switch(low){
			case 0:
				while(rd() != 0xf7);
				break;
			case 1:
			case 3:
				rd();
				break;
			case 2:
				rd();
				rd();
				break;
			case 0xf: /* meta */
				n = rd();
				switch(type){
				case 0x51: /* set tempo */
					v = rd_int(n);
					tempo = v;
					tempo_delta_sum = delta_sum;
					tempo_sec = sec;
					break;
				default:
					for(i=0; i<n; i++) rd();
					break;
				}
				break;
			default:
				break;
			}
			break;
		}
	}
	if(otr.fp != stdout) pclose(otr.fp);
	return 0;
}

/* EOF */