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

#define SYSERROR "ERR"
#define SYSERRORLEN 3
#define IOERROR "IOERR"
#define IOERRORLEN 5
#define NOTAFILE "NAF"
#define ENDOFILE "EOF"
#define SENDOFILE " EOF"

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

static int flip, quiet, debug, cycles = 0x200000;
static Rule rules[0x1000], *rules_ = rules;
static char dict[0x8000], *dict_ = dict;
static char bank_a[0xF0000], *src_ = bank_a;
static char bank_b[0xF0000], *dst_ = bank_b;
static char *regs[0x100], stack[0x10], *stack_ = stack;

/** rosin */
FILE* outstream_;
FILE* instream_;
int instream_subproc = 0;

static void close_instream() {
  if (instream_ != stdin) {
    if (instream_subproc) {
      if (debug) fprintf(stderr, "Closing input process\n");
      pclose(instream_);
      instream_subproc = 0;
    } else {
      if (debug) fprintf(stderr, "Closing previous instream\n");
      fclose(instream_);
    }
  }
}

static void
set_outstream(char *path) {
  if (debug) fprintf(stderr, "Opening path '%s'\n", path);

  if (outstream_ != stdout && outstream_ != stderr) {
    if (debug) fprintf(stderr, "Closing previous outstream\n");
    fclose(outstream_);
  }
  if (strcmp(path, "<stdout>") == 0) {
    if (debug) fprintf(stderr, "set outstream to stdout\n");
    outstream_ = stdout;
  } else if (strcmp(path, "<stderr>") == 0) {
    if (debug) fprintf(stderr, "set outstream to stderr\n");
    outstream_ = stderr;
  } else {
    if (debug) fprintf(stderr, "Opening outstream_: %s\n", path);
    outstream_ = fopen(path, "w");
  }
}

static int
set_instream(char *path) {
  close_instream();
  if (debug) fprintf(stderr, "Opening instream_: %s\n", path);
  if(!(instream_ = fopen(path, "r"))){
    if (debug) fprintf(stderr, "Failed to open file for reading, defaulting to <stdin>: %s\n", path);
    instream_ = stdin;
    return 1;
  }
}
static int 
subprocess_instream(char *cmd)
{
  if (debug) fprintf(stderr, "[ :: cmd: '%s' :: ]\n", cmd);

  close_instream();
  instream_ = popen(cmd, "r");
  if(!instream_) {
    if (debug) fprintf(stderr, "Failed to run command \"%s\" for reading, defaulting to <stdin>\n", cmd);
    instream_ = stdin;
    return 1;
  }
  instream_subproc = 1;

}

#define spacer(c) (c <= ' ' || c == '(' || c == ')')
#define chex(c) (0xf & (c - (c <= '9' ? '0' : 0x57)))

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

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 int
sint(char *s)
{
	char c = *s, *cap = walk(s);
	int r = 0, n = 1;
	if(c == '#') {
		s++;
		while((c = *s) && s++ < cap) r = (r << 4) | chex(c);
		return r;
	}
	if(c == '-') { n = -1, s++; }
	while((c = *s) && s++ < cap) r = r * 10 + c - '0';
	return r * n;
}

static void
device_write(char *s)
{
	char **reg = regs + '0';
	/* phase: ALU */
	if(*reg) {
		int hex = **reg == '#', 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, hex ? "#%x" : "%d", acc);
		return;
	} else {
		/* phase: string */
		char *cap = walk(s);
		if(*s == '(') s++, --cap; // idiom for getting inside of parens
		while(s < cap) {
			char c = *s++, hb, lb;
      if (debug) fprintf(stderr, "printing char: '%c'\n", c);
			if(c == '\\') {
				switch(*s++) {
				case 't': putc(0x09, outstream_); break;
				case 'n': putc(0x0a, outstream_); break;
				case 's': putc(0x20, outstream_); break;
				case '#': hb = *s++, lb = *s++, putc((chex(hb) << 4) | chex(lb), outstream_); break;
				}
			} else
				putc(c, outstream_);
		}
	}
}

static char *
subprocess_import(char *cmd, char *ptr)
{
  if (debug) fprintf(stderr, "[ :: cmd: '%s' :: ]\n", cmd);
  FILE *subprocess;
  int pr = 0;
  if((subprocess = popen(cmd, "r"))) {
		unsigned char c, last = 0;
		while(fread(&c, 1, 1, subprocess)) {
			c = c <= 0x20 ? 0x20 : c;
			if(c == '(') pr++;
			if(c == ')') pr--;
			if(c == ' ' && last == '(') continue;
			if(c == ')' && last == ' ') ptr--;
			if(c == ' ' && last == ' ') ptr--;
			if(c == '(' && last != '?' && !spacer(last)) *ptr++ = ' ';
			if(last == ')' && !spacer(c)) *ptr++ = ' ';
			*ptr++ = last = c;
		}
		while(*(--ptr) <= ' ') *ptr = 0;
		int exitcode = pclose(subprocess);
    if (debug) fprintf(stderr, "[ :: cmd closed with exit code: '%d' :: ]\n", exitcode);
		if(pr) fprintf(stderr, "Modal program imbalanced.\n");
		return ptr + 1;
  }

  return copy(SYSERROR, ptr, SYSERRORLEN);
}

static char *
file_import(char *path, char *ptr)
{
  if (debug) fprintf(stderr, "[ :: file path: '%s' :: ]\n", path);
	FILE *f;
	int pr = 0;
	if((f = fopen(path, "r"))) {
		unsigned char c, last = 0;
		while(fread(&c, 1, 1, f)) {
			c = c <= 0x20 ? 0x20 : c;
			if(c == '(') pr++;
			if(c == ')') pr--;
			if(c == ' ' && last == '(') continue;
			if(c == ')' && last == ' ') ptr--;
			if(c == ' ' && last == ' ') ptr--;
			if(c == '(' && last != '?' && !spacer(last)) *ptr++ = ' ';
			if(last == ')' && !spacer(c)) *ptr++ = ' ';
			*ptr++ = last = c;
		}
		while(*(--ptr) <= ' ') *ptr = 0;
		fclose(f);
		if(pr) fprintf(stderr, "Modal program imbalanced.\n");
		return ptr + 1;
	}
	return copy(NOTAFILE, ptr, 3);
}

static void
write_reg(char r, char *reg)
{
	switch(r) {
	case ':': device_write(reg); break;
	case '~': {
    // this does not do anything to normalize input
    // it just socks it in like it's a line of text in a modal file
    // which makes sense . . .
    // we basically just trust that expressions are sanitized
		unsigned char c;
		char *origin = dst_;
		while(fread(&c, 1, 1, instream_) && c >= ' ') *dst_++ = c;
		if(feof(instream_) && origin == dst_) {
      dst_ = copy(ENDOFILE, dst_, 3);
    }
    // we handle this in apply_rule now
    // this was causing an issue when ttrying to rewrite and getting empty input
		//if(origin == dst_) dst_--; // catches empty input, prevents accumulating space
		break;
	}
  case '>': { /* op: set outstream to file*/
    char filepath[0x80] = {0};
		copy(reg, filepath, walk(reg) - reg);
    set_outstream(filepath);
    break;
  }
  case '<': { /* op: set instream to file */
    char filepath[0x80] = {0};
		copy(reg, filepath, walk(reg) - reg);
    set_instream(filepath);
    break;
  }
  case '_': { /* op: import file */
		char filepath[0x80] = {0};
		copy(reg, filepath, walk(reg) - reg);
		dst_ = file_import(filepath, dst_);
		break;
	}
  case '!': { /* op: subprocess */
    char cmd[0xFF] = {0};
    int len = walk(reg) - reg;
    int o = 0;
    if (*reg == '(' && reg[len - 1] == ')') { 
      o++; len -= 2;
    }

    copy(reg + o, cmd, len);
    if (len <= 0) {
      if (debug) fprintf(stderr, "[ :: bad command: '%s' :: ]\n", cmd);
      copy(SYSERROR, dst_, SYSERRORLEN);
    }
    else{
      dst_ = subprocess_import(cmd, dst_);
    }
    break;
  }
  case '|': { /* op: attach subprocess to input */
    char cmd[0xFF] = {0};
    int len = walk(reg) - reg;
    int o = 0;
    if (*reg == '(' && reg[len - 1] == ')') { 
      o++; len -= 2;
    }

    copy(reg + o, cmd, len);
    if (len <= 0) {
      if (debug) fprintf(stderr, "[ :: bad command: '%s' :: ]\n", cmd);
      copy(SYSERROR, dst_, 3);
    }
    else{
      if(subprocess_instream(cmd) != 0) copy(IOERROR, dst_, IOERRORLEN);
    }
    break;
    break;
  }
	case '^': { /* op: join */
		char c, *cap = walk(reg);
		if(*reg == '(') reg++, --cap;
		while(reg < cap && (c = *reg++))
			if(!spacer(c)) *dst_++ = c;
		break;
	}
	case '.': { /* op: unwrap */
		char *cap = walk(reg);
		if(*reg == '(') reg++, --cap;
		dst_ = copy(reg, dst_, cap - reg);
		break;
	}
	case '*': { /* op: explode */
		int i, depth = 0;
		char c, *cap = walk(reg);
		if(*reg == '(' && reg[1] != ')') { /* tuple */
			reg++;
			while(reg < cap - 1) {
				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_++ = ')';
		break;
	}
	default: dst_ = copy(reg, dst_, walk(reg) - reg);
	}
}

static int
write_tail(char *s, Rule *r)
{
	while((*dst_++ = *s++))
		;
	*dst_ = 0;
	if((flip = !flip))
		src_ = bank_b, dst_ = bank_a;
	else
		src_ = bank_a, dst_ = bank_b;
	if(r && !quiet) fprintf(stderr, "%02d %s\n", r->id, src_), ++r->refs;
	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 */
	while((c = *b++))
    // we could be a little more smart here and catch precisely the situation
    // where dst_ has advanced by only 1 and is a space (empty rewrite)
		if(c == '?' && (rid = *b) && (reg = regs[rid])) {
			write_reg(rid, reg), b++;
      if (*(dst_ - 1) <= ' ') {
        if (debug) fprintf(stderr, "reg ID: : |%c|\n", rid);
        if (debug) fprintf(stderr, "reg |%s|\n", reg);
        if (debug) fprintf(stderr, "[:: NB: dst is a space char: %c::]\n", *(dst_ - 1));
        dst_--;
      }
    }
		else
			*dst_++ = c;
  // alternatively, that might be something this down here is meant to catch
	if(dst_ == origin) {
		while(*s == ' ') s++;
		if(*s == ')' && *(dst_ - 1) == ' ') dst_--;
	}
	return write_tail(s, r);
}

static char *
parse_frag(char **side, char *s)
{
	char c, *cap;
	while((c = *s) && c == ' ') s++;
	if(c == ')' || (c == '<' && s[1] == '>') || (c == '>' && s[1] == '<'))
		*side = dict_, *dict_++ = 0;
	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;
		while(*ss++ == *a++)
			if(!*a && ss == cap) return r;
		r++;
	}
	return NULL;
}

static void
remove_rule(Rule *r)
{
	if(r < rules_ - 1) {
		char *memsrc = (r + 1)->a;
		int distance = (r + 1)->a - r->a;
		copy(memsrc, r->a, dict_ - memsrc);
		while(r < rules_ - 1) {
			Rule *next = r + 1;
			r->id = next->id, r->refs = next->refs;
			r->a = next->a - distance;
			r->b = next->b - distance;
			r++;
		}
	}
	rules_--;
}

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

int
main(int argc, char **argv)
{
  outstream_ = stdout;
  instream_ = stdin;
	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, 23 Dec 2024.\n");
		case 'q': /* quiet */ quiet = 1; break;
		case 'p': /* debug */ debug = 1; break;
		case 'n': /* infinite */ cycles = 0xffffffff; break;
		}
	}
  if (debug == 1) fprintf(stderr, "Debug mode is active\n");
	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);
	}
  fflush(outstream_);
  if (outstream_ != stdout) fclose(outstream_);
  if (instream_ != stdin) close_instream();
	return 0;
}