#include <u.h>
#include <libc.h>
#include <bio.h>

#define MAX(a,b) ((a) > (b) ? (a) : (b))

enum {
	Maxsamples = 64,
	Maxargs = 8,
	Bufsize = 4096,
};

typedef struct Sample Sample;
typedef struct Event Event;

struct Sample {
	Sample *next;
	int len;
	short *data;
	char *name;
};

struct Event {
	Event *next, *prev;
	int t, len;
	int vol;
	short *data;
};

Event E = { .prev = &E, .next = &E };
Event P = { .prev = &P, .next = &P };
Sample *S;
Biobuf in, out;
int last;

void
unlink(Event *e)
{
	e->prev->next = e->next;
	e->next->prev = e->prev;
}

void
link(Event *h, Event *e)
{
	e->prev = h->prev;
	e->next = h;
	h->prev->next = e;
	h->prev = e;
}

int 
playone(int t)
{
	Event *e;
	int s;

	while((e = E.next) != &E && e->t == t){
		unlink(e);
		link(&P, e);
	}
	for(s = 0, e = P.next; e != &P; e = e->next){
		if(e->len == 0)
			unlink(e);
		s = s + e->vol * *e->data++;
		e->len--;
	}
	return s;
}

int 
find0xing(Sample *s, int k)
{
	int sign;
	if(k < 0 || k >= s->len)
		return s->len;
	if(k == 0)
		return 0;
	sign = s->data[k-1] >= 0;
	for(; k < s->len && sign == (s->data[k] > 0); k++)
		;
	return k;
}

void *
readfile(char *name, int *len)
{
	int fd;
	Dir *dir;
	void *p;
	int l;
	
	fd = open(name, OREAD);
	if(fd < 0)
		sysfatal("%s: %r", name);
	dir = dirfstat(fd);
	if(dir == nil)
		sysfatal("%s: %r", name);
	l = dir->length;
	p = malloc(l);
	if(readn(fd, p, l) != l)
		sysfatal("%s: %r", name);
	close(fd);
	*len = l;
	return p;
}

void 
parse(char *line, int no)
{
	char *argv[Maxargs];
	int argc;
	Event *e;
	Sample *s;
	
	argc = tokenize(line, argv, Maxargs);
	if(argc == 0)
		return;
	if(argv[0][0] == '#')
		return;
	if(argc < 3)
		goto err;
	if(argc > 3 && strtol(argv[3], 0, 0) == 0){
		last = MAX(last, strtol(argv[0], 0, 0));
		return;
	}
	for(s=S; s; s=s->next){
		if(strcmp(s->name, argv[1]) == 0)
			break;
	}
	if(s == nil){
		s = malloc(sizeof(*s));
		s->data = readfile(argv[1], &s->len);
		s->name = strdup(argv[1]);
		s->len /= 2;
		s->next = S;
		S = s;
	}
	e = malloc(sizeof *e);
	e->t = strtol(argv[0], 0, 0);
	e->vol = strtol(argv[2], 0, 0);
	e->len = find0xing(s, argc > 3 ? strtol(argv[3], 0, 0) : -1);
	e->data = s->data;
	if(e->vol > 128 || e->vol < 0 || E.prev->t > e->t)
		goto err;
	link(&E, e);
	last = MAX(last, e->t + e->len);
	return;
err:
	sysfatal("parser error on line %d", no);
}

void
putsample(Biobuf *b, int s)
{
	Bputc(b, s & 0xff);
	Bputc(b, (s >> 8) & 0xff);
}

void
main(int, char *)
{
	char *line;
	int no;
	int t, s;
	
	Binit(&in, 0, OREAD);
	Binit(&out, 1, OWRITE);
	
	for(no=1; (line = Brdline(&in, '\n')) != nil; no++){
		line[Blinelen(&in)-1] = 0;
		parse(line, no);
	}
	for(t=0; t < last; t++){
		s = playone(t) / 128;
		putsample(&out, s);
		putsample(&out, s);
	}
	
	Bterm(&in);
	Bterm(&out);
	exits(nil);
}