modal/src/modal.c

#include <stdio.h>

typedef struct {
	int id;
	char *a, *b;
} Rule;

static int direction;
static Rule rules[0x1000], *rules_ = rules;
static char dict[0x8000], *dict_ = dict;
static char bank_a[0x4000], *prog_ = bank_a;
static char bank_b[0x4000], *outp_ = bank_b;
static char *regs[0x100];

#define spacer(c) (c < 0x21 || c == '(' || c == ')')

static char *
walk(char *s)
{
	char c;
	int depth = 0;
	if(s[0] == '(') {
		while((c = *s++)) {
			if(c == '(') depth++;
			if(c == ')') --depth;
			if(!depth) return s;
		}
	}
	while((c = *s) && !spacer(c)) s++;
	return s;
}

static char *
plode(char *s)
{
	int i, depth = 0;
	char c;
	if(s[0] == '(') { /* implode */
		while((c = *s++)) {
			if(c == '(') depth++;
			if(!spacer(c)) *outp_++ = c;
			if(c == ')') --depth;
			if(!depth) return s;
		}
	} else { /* explode */
		*outp_++ = *s++;
		if(!spacer(*s)) *outp_++ = ' ';
		while((c = *s++) && !spacer(c)) {
			*outp_++ = '(', *outp_++ = c, depth++, c = *s;
			if(!spacer(c)) *outp_++ = ' ';
		}
		for(i = 0; i < depth; i++)
			*outp_++ = ')';
	}
	return s;
}

static int
set_reg(int r, char *b)
{
	if(regs[r]) {
		char *a = regs[r], *aa = walk(a), *bb = walk(b);
		while(a < aa && b < bb)
			if(*a++ != *b++) return 0;
	} else
		regs[r] = b;
	return 1;
}

static int
put_reg(char r)
{
	char *s = regs[(int)r];
	if(r == '*')
		s = plode(s);
	else if(r == '~') {
		char buf;
		while(fread(&buf, 1, 1, stdin) && buf >= ' ')
			*outp_++ = buf;
	} else if(s) {
		char *ss = walk(s);
		if(r == ':') {
			if(*s == '(') s++, --ss;
			while(s < ss) {
				char c = *(s++);
				if(c == '\\' && *(s++) == 'n') c = 0xa;
				putc(c, stdout);
			}
		} else
			while((s < ss)) *outp_++ = *s++;
	} else
		*outp_++ = r;
	return 1;
}

static char *
match_rule(Rule *r, char *p)
{
	int i;
	char c, *a = r->a, *b = p;
	for(i = 0x21; i < 0x7f; i++)
		regs[i] = 0;
	while((c = *a)) {
		if(c == '?') {
			if(!set_reg(*(++a), b)) return NULL;
			a++, b = walk(b);
			continue;
		}
		if(*a != *b) return NULL;
		a++, b++;
	}
	c = *b;
	return spacer(c) ? b : NULL;
}

static int
commit_rule(Rule *r, char *s, int create)
{
	while((*outp_++ = *s++))
		;
	*outp_++ = 0;
	if((direction = !direction))
		prog_ = bank_b, outp_ = bank_a;
	else
		prog_ = bank_a, outp_ = bank_b;
	if(create)
		fprintf(stderr, "<> (%s) (%s)\n", r->a, r->b);
	else
		fprintf(stderr, "%02d %s\n", r->id, prog_);
	return 1;
}

static char *
parse_frag(char *s)
{
	char c, *ss;
	while((c = *s) && c <= ' ') s++;
	ss = walk(s);
	if(*s == '(') s++, ss--;
	while((s < ss)) *dict_++ = *s++;
	*dict_++ = 0;
	s++;
	return s;
}

static int
write(Rule *r, char last, char *res)
{
	char cc, *b = r->b;
	if(!*b && last == ' ') outp_--;
	while((cc = *b++))
		if(cc == '?')
			put_reg(*b++);
		else
			*outp_++ = cc;
	return commit_rule(r, res, 0);
}

static int
rewrite(void)
{
	char c, last = 0, *p = direction ? bank_b : bank_a, *res;
	while((c = *p) && c <= ' ') p++;
	while((c = *p)) {
		if(spacer(last)) {
			Rule *r;
			if(p[0] == '<' && p[1] == '>') {
				r = rules_++;
				r->id = rules_ - rules - 1;
				p += 2, r->a = dict_, p = parse_frag(p), r->b = dict_, p = parse_frag(p);
				return commit_rule(r, p, 1);
			}
			if(p[0] == '?' && p[1] == '(') {
				Rule lambda;
				lambda.id = -1;
				p += 2, lambda.a = dict_, p = parse_frag(p), lambda.b = dict_, p = parse_frag(p);
				p++;
				while((c = *p) && c <= ' ') p++;
				if((res = match_rule(&lambda, p)) != NULL)
					return write(&lambda, last, res);
			}
			for(r = rules; r < rules_; r++)
				if((res = match_rule(r, p)) != NULL)
					return write(r, last, res);
		}
		*outp_++ = last = c;
		p++;
	}
	*outp_++ = 0;
	return 0;
}

int
main(int argc, char **argv)
{
	FILE *f;
	char c, *w = bank_a;
	if(argc < 2)
		return !printf("usage: modal [-v] source.modal\n");
	if(argc < 3 && argv[1][0] == '-' && argv[1][1] == 'v')
		return !printf("Modal Interpreter, 10 Apr 2024.\n");
	if(!(f = fopen(argv[1], "r")))
		return !printf("Invalid Modal file: %s.\n", argv[1]);
	while(fread(&c, 1, 1, f)) {
		if(w > bank_a) {
			if(c == ' ' && *(w - 1) == '(') continue;
			if(c == ')' && *(w - 1) == ' ') w--;
			if(c == ' ' && *(w - 1) == ' ') w--;
		}
		*w++ = c;
	}
	while(*(--w) <= ' ') *w = 0;
	fclose(f);
	while(rewrite())
		;
	return 0;
}