#include <stdio.h>

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

static int flip, quiet, debug, access, cycles = 0x200000;
static Rule rules[0x1000], *rules_ = rules;
static char dict[0x8000], *dict_ = dict;
static char bank_a[0x4000], *src_ = bank_a;
static char bank_b[0x4000], *dst_ = bank_b;
static char *regs[0x100], stack[0x10], *stack_ = stack;

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

static char *
copy(char *src, char *dst, int length)
{
	while(length--) *dst++ = *src++;
	return dst;
}

static int
sint(char *s)
{
	char c;
	int r = 0, n = 1;
	if(*s == '-') { n = -1, s++; }
	while((c = *s++) && !spacer(c)) r = r * 10 + c - '0';
	return r * n;
}

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

static void
device_write(char *s)
{
	char **reg = regs + '0';
	/* phase: ALU */
	if(*reg) {
		int acc = sint(*reg++);
		/* clang-format off */
		switch(*s) {
		case '+': while(*reg) acc += sint(*reg++); break;
		case '-': while(*reg) acc -= sint(*reg++); break;
		case '*': while(*reg) acc *= sint(*reg++); break;
		case '/': while(*reg) acc /= sint(*reg++); break;
		case '%': while(*reg) acc %= sint(*reg++); break;
		case '&': while(*reg) acc &= sint(*reg++); break;
		case '^': while(*reg) acc ^= sint(*reg++); break;
		case '|': while(*reg) acc |= sint(*reg++); break;
		case '=': while(*reg) acc = acc == sint(*reg++); break;
		case '!': while(*reg) acc = acc != sint(*reg++); break;
		case '>': while(*reg) acc = acc > sint(*reg++); break;
		case '<': while(*reg) acc = acc < sint(*reg++); break;
		}
		/* clang-format on */
		dst_ += snprintf(dst_, 0x10, "%d", acc);
		return;
	} else {
		/* phase: string */
		char *cap = walk(s);
		if(*s == '(') s++, --cap;
		while(s < cap) {
			char c = *s++;
			if(c == '\\') {
				switch(*s++) {
				case 't': putc(0x09, stdout); break;
				case 'n': putc(0x0a, stdout); break;
				case 's': putc(0x20, stdout); break;
				}
			} else
				putc(c, stdout);
		}
	}
}

static void
device_read(void)
{
	char c, *origin = dst_;
	while(fread(&c, 1, 1, stdin) && c >= ' ') *dst_++ = c;
	if(feof(stdin)) dst_ = copy("EOF", dst_, 3);
	if(dst_ - origin == 0) dst_--;
}

static char *
file_import(char *path, char *ptr)
{
	FILE *f;
	int pr = 0;
	if((f = fopen(path, "r"))) {
		char c;
		while(fread(&c, 1, 1, f)) {
			c = c <= 0x20 ? 0x20 : c;
			if(c == '(') pr++;
			if(c == ')') pr--;
			*ptr++ = c;
		}
		fclose(f);
		if(pr) fprintf(stderr, "Modal program imbalanced.\n");
		return ptr;
	}
	return copy("NAF", ptr, 3);
}

static void
write_reg(char r, char *reg)
{
	switch(r) {
	case ':': device_write(reg); return;
	case '~': device_read(); return;
	case '_': {
		char filepath[0x80];
		copy(reg, filepath, walk(reg) - reg);
		dst_ = file_import(filepath, dst_);
		return;
	}
	case '^': { /* op: join */
		char c, *cap = walk(reg);
		if(*reg == '(') reg++, --cap;
		while(reg < cap && (c = *reg++))
			if(!spacer(c)) *dst_++ = c;
		return;
	}
	case '.': { /* op: unwrap */
		char *cap = walk(reg);
		if(*reg == '(') reg++, --cap;
		dst_ = copy(reg, dst_, cap - reg);
		return;
	}
	case '*': { /* op: explode */
		int i, depth = 0;
		char c, *cap = walk(reg);
		if(*reg == '(' && reg[1] != ')') { /* tuple */
			reg++;
			while(reg < cap) {
				while((c = *reg) && !spacer(c))
					*dst_++ = c, reg++;
				*dst_++ = ' ';
				*dst_++ = '(', reg++, depth++;
			}
		} else /* token */
			while((c = *reg++) && !spacer(c))
				*dst_++ = c, *dst_++ = ' ', *dst_++ = '(', depth++;
		for(i = 0; i < depth; i++) *dst_++ = ')';
		return;
	}
	default: {
		dst_ = copy(reg, dst_, walk(reg) - reg);
		return;
	}
	}
}

static int
write_tail(char *s)
{
	while((*dst_++ = *s++))
		;
	*dst_ = 0;
	if((flip = !flip))
		src_ = bank_b, dst_ = bank_a;
	else
		src_ = bank_a, dst_ = bank_b;
	return 1;
}

static int
apply_rule(Rule *r, char *s)
{
	unsigned char rid;
	char c, *a = r->a, *b = r->b, *origin = dst_, *reg;
	/* phase: clean regs */
	while(stack_ != stack) regs[(int)*(--stack_)] = 0;
	/* phase: match rule */
	while((c = *a++)) {
		if(c == '?') {
			char *pcap = walk(s);
			rid = *a++;
			if((reg = regs[rid])) { /* reg cmp */
				char *rcap = walk(reg), *pp = s;
				while(reg < rcap || pp < pcap)
					if(*reg++ != *pp++) return 0;
			} else /* reg set */
				regs[rid] = s, *stack_++ = rid;
			s = pcap;
		} else if(c != *s++)
			return 0;
	}
	c = *s;
	if(!spacer(c)) return 0;
	/* phase: write rule */
	if(b != NULL) {
		while((c = *b++))
			if(c == '?' && (rid = *b) && (reg = regs[rid]))
				write_reg(rid, reg), b++;
			else
				*dst_++ = c;
	}
	if(dst_ == origin) {
		while(*s == ' ') s++;
		if(*s == ')' && *(dst_ - 1) == ' ') dst_--;
	}
	if(!quiet) fprintf(stderr, "%02d %s\n", r->id, src_), ++r->refs;
	return write_tail(s);
}

static char *
parse_frag(char **side, char *s)
{
	char c, *cap;
	while((c = *s) && c == ' ') s++;
	if(c == ')' || c == '<' || c == '>' || (c == '(' && s[1] == ')'))
		*side = NULL;
	else {
		cap = walk(s), *side = dict_;
		if(c == '(')
			dict_ = copy(s + 1, dict_, cap - s - 2);
		else
			dict_ = copy(s, dict_, cap - s);
		s = cap, *dict_++ = 0;
	}
	return s;
}

static Rule *
find_rule(char *s, char *cap)
{
	Rule *r = rules;
	if(*s == '(') s++, cap--;
	while(r < rules_) {
		char *ss = s, *a = r->a;
		if(a)
			while(*ss++ == *a++)
				if(!*a && ss == cap) return r;
		r++;
	}
	return NULL;
}

static int
rewrite(void)
{
	char c, last = 0, *cap, *s = src_;
	while(*s == ' ') s++;
	while((c = *s)) {
		if(c == '(' || spacer(last)) {
			Rule *r = NULL;
			/* phase: undefine */
			if(c == '>' && s[1] == '<') {
				s += 2;
				while(*s == ' ') s++;
				cap = walk(s), r = find_rule(s, cap);
				if(r != NULL) {
					if(!quiet) fprintf(stderr, ">< (%s) (%s)\n", r->a, r->b);
					r->a = 0;
				}
				while(*cap == ' ') cap++;
				return write_tail(cap);
			}
			/* phase: define */
			if(c == '<' && s[1] == '>') {
				r = rules_, r->id = rules_ - rules;
				s = parse_frag(&r->b, parse_frag(&r->a, s + 2));
				if(r->a != NULL) {
					if(!quiet) fprintf(stderr, "<> (%s) (%s)\n", r->a, r->b);
					rules_++;
				}
				while(*s == ' ') s++;
				return write_tail(s);
			}
			/* phase: lambda */
			if(c == '?' && s[1] == '(') {
				char *d = dict_;
				cap = walk(s + 1);
				r = rules_, r->id = -1;
				parse_frag(&r->b, parse_frag(&r->a, s + 2));
				s = cap;
				while(*s == ' ') s++;
				if(r->a == NULL || !apply_rule(r, s)) write_tail(s);
				dict_ = d;
				return 1;
			}
			/* phase: match */
			for(r = rules; r < rules_; r++)
				if(r->a != NULL && apply_rule(r, s)) return 1;
		}
		*dst_++ = last = c, s++;
	}
	*dst_++ = 0;
	return 0;
}

int
main(int argc, char **argv)
{
	int i, rw = 0;
	if(argc < 2)
		return !printf("usage: modal [-vqn] source.modal\n");
	for(i = 1; i < argc && *argv[i] == '-'; i++) {
		switch(argv[i][1]) {
		case 'v': /* version */ return !printf("Modal Interpreter, 10 May 2024.\n");
		case 'q': /* quiet */ quiet = 1; break;
		case 'p': /* debug */ debug = 1; break;
		case 'a': /* access */ access = 1; break;
		case 'n': /* infinite */ cycles = 0xffffffff; break;
		}
	}
	file_import(argv[i], src_);
	while(rewrite() && ++rw)
		if(!cycles--) return !fprintf(stderr, "Modal rewrites exceeded.\n");
	if(!quiet) {
		while(rules_-- > rules)
			if(rules_->a && !rules_->refs)
				fprintf(stderr, "-- Unused rule: %d <> (%s) (%s)\n", rules_->id, rules_->a, rules_->b);
		if(rw)
			fprintf(stderr, ".. %s\nCompleted in %d rewrites.\n", src_, rw);
	}
	return 0;
}