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

#include "common.h"
#include "error.h"
#include "logic.h"
#include "gate.h"


int parse_input(char *);
int parse_module(char *);
int parse_expr(char *);

struct tok_lookup {
	char *str;
	int (*handler)(char*);
};

struct op_lookup {
	char *str;
	enum BINARY (*handler)(enum BINARY, enum BINARY);
};

static struct op_lookup uop_handlers[] = {
	{.str = "not",   .handler = logic_nand},
};

static struct op_lookup bop_handlers[] = {
	{.str = "and",   .handler = logic_and},
	{.str = "or",    .handler = logic_or},
	{.str = "nand",  .handler = logic_nand},
	{.str = "nor",   .handler = logic_nor},
	{.str = "xor",   .handler = logic_xor}
};

static struct tok_lookup tok_handlers[] = {
	{.str = "input",   .handler = parse_input},
	{.str = "module", .handler = parse_module},
	{.str = "expr",   .handler = parse_expr}
};

int
rtrim(char *string) {
	char *old_end = string + strlen(string);
	char *w = NULL;

	string[strcspn(string, "\r\n")] = '\0';

	/* find first member of right whitespace */
	for (w = old_end; w >= string; w--) {
		if (strchr("\t ", *w) == NULL) {
			break;
		}
		*w = '\0';
	}

	return old_end - w;
}

char *
eat_whitespace(char *string) {
	while (*string && isspace(*string)) {
		string++;
	}
	return string;
}

char *
get_token_special(char *string, char **rest, char *delims) {
	size_t tok_len = 0;
	char *ret = NULL;
	string = eat_whitespace(string);
	tok_len = strcspn(string, delims);
	if (tok_len == 0) {
		emit_error("unexpected end of string");
		return NULL;
	}
	if (NULL == (ret = strndup(string, tok_len))) {
		emit_error("get_token: ");
		perror("strndup");
		return NULL;
	}
	*rest = string + tok_len;
	return ret;
}

char *
get_token(char *string, char **rest) {
	return get_token_special(string, rest, " \t");
}

int
expect(const char *expect, char *actual) {
	int min_len = 0;

	min_len = MIN(strlen(expect), strlen(actual));

	if (strncmp(expect, actual, min_len) != 0) {
		emit_error("Expected '%s' at start of '%s'\n", expect, actual);
		return 1;
	}
	return 0;
}

int parse_uop(char *str, char *name, enum BINARY (*handler)(enum BINARY, enum BINARY)) {
	char *source_name = NULL;
	char *next = NULL;

	if (NULL == (source_name = get_token(str, &next))) {
		return 1;
	}

	/* FIXME allow input from other gates, not just inputs */
	struct gate *in = gate_get_input_by_name(source_name);
	free(source_name);

	return gate_add(name, handler, in, in);


}

int parse_bop(char *str, char *name, enum BINARY (*handler)(enum BINARY, enum BINARY)) {
	char *source_name1 = NULL;
	char *source_name2 = NULL;
	char *next = NULL;
	struct gate *in1 = NULL;
	struct gate *in2 = NULL;

	if (NULL == (source_name1 = get_token(str, &next))) {
		return 1;
	}

	if (NULL == (source_name2 = get_token(next, &next))) {
		free(source_name1);
		return 1;
	}

	if (*next != '\0') {
		emit_error("superfluous text \"%s\"\n", next);
		free(source_name1);
		free(source_name2);
		return 1;
	}

	/* FIXME allow input from other gates, not just inputs */
	in1 = gate_get_input_by_name(source_name1);
	in2 = gate_get_input_by_name(source_name2);

	free(source_name1);
	free(source_name2);

	if (in1 == NULL || in2 == NULL) {
		emit_error("Undeclared identifier in source(s) for expression '%s'\n",
		           name);
		return 1;
	}

	return gate_add(name, handler, in1, in2);
}

int
parse_op(char *str, char *name) {
	char *tok = NULL;
	char *next = NULL;
	int match = 0;
	size_t i = 0;

	if (NULL == (tok = get_token(str, &next))) {
		return 1;
	}

	match = 0;
	for (i = 0; i < sizeof(bop_handlers)/sizeof(bop_handlers[0]); i++) {
		if (strcmp(bop_handlers[i].str, tok) == 0) {
			match = 1;
			if (parse_bop(next, name, bop_handlers[i].handler)) {
				free(tok);
				return 1;
			}
		}
	}
	for (i = 0; i < sizeof(uop_handlers)/sizeof(uop_handlers[0]); i++) {
		if (strcmp(uop_handlers[i].str, tok) == 0) {
			match = 1;
			if (parse_uop(next, name, uop_handlers[i].handler)) {
				free(tok);
				return 1;
			}
		}
	}
	if (match == 0) {
		emit_error("Invalid operator \"%s\"\n", tok);
		free(tok);
		return 1;
	}
	free(tok);
	return 0;
}

int
parse_expr(char *str) {
	const char *expr_sep = ": ";
	char *ident = NULL;
	char *next = NULL;
	char *op = NULL;

	if (NULL == (ident = get_token_special(str, &next, ": \t"))) {
		return 1;
	}

	if (expect(expr_sep, next)) {
		free(ident);
		return 1;
	}

	op = next + strlen(expr_sep);

	return parse_op(op, ident);
}

int
parse_input(char *str) {
	char *ident = NULL;
	char *next = NULL;
	int ret = 0;

	if (NULL == (ident = get_token(str, &next))) {
		return 1;
	}

	if (strlen(ident) == 0) {
		emit_error("input label must not be empty");
		free(ident);
		return 1;
	}

	if (*next != '\0') {
		emit_error("superfluous text after \"%s\" identifier: \"%s\"\n",
		           ident, next);
		free(ident);
		return 1;
	}

	emit_info("Add input '%s'\n", ident);
	ret = gate_input_add(ident);
	free(ident);
	return ret;
}

int
parse_module(char *str) {
	char *mod_name = NULL;
	char *next = NULL;
	if (NULL == (mod_name = get_token(str, &next))) {
		return 1;
	}

	if (*next != '\0') {
		emit_error("superfluous text following module name");
		free(mod_name);
		return 1;
	}

	printf("FIXME module name is \"%s\" but modules are not implemented\n", mod_name);
	free(mod_name);
	return 0;
}

int
parse_line(char *line) {
	size_t i = 0;
	char *next = NULL;
	char *tok = NULL;
	int match = 0;

	rtrim(line);

	if (   strlen(line) == 0
	    || (strlen(line) == 1 && isspace(line[0]))) {
		return 0;
	}

	if (NULL == (tok = get_token(line, &next))) {
		return 1;
	}

	match = 0;
	for (i = 0; i < sizeof(tok_handlers)/sizeof(tok_handlers[0]); i++) {
		if (strcmp(tok_handlers[i].str, tok) == 0) {
			match = 1;
			if ((tok_handlers[i].handler)(next)) {
				free(tok);
				return 1;
			}
		}
	}

	free(tok);

	if (match == 0) {
		emit_error("invalid token \"%s\"", tok);
		return 1;
	}
	return 0;
}