#include "parse.h"
#include "Token.h"
#include "Scope.h"
#include <stdio.h>
#include <stdlib.h>

static void *unexpected(const Token *tok, int n);
static const Token *expression(const Token *tok);
static const Token *keyword_fn(const Token *tok);
static const Token *keyword_var(Scope *scope, const Token *tok);
static const Token *keyword_const(Scope *scope, const Token *tok);

int parse(const Token *tok)
{
	Scope *scope = scope_create(NULL);
	if (scope == NULL)
		return 1;
	while (tok != NULL && tok->type != TOK_NONE) {
		switch (tok->type) {
		case TOK_KW_FN:
			tok = keyword_fn(tok);
			break;
		case TOK_KW_VAR:
			tok = keyword_var(scope, tok);
			break;
		case TOK_KW_CONST:
			tok = keyword_const(scope, tok);
			break;
		default:
			unexpected(tok, -1);
			return free(scope), 1;
		}
		if (tok == NULL)
			return free(scope), 1;
	}
	return free(scope), 0;
}

/* write unexpected token error to stderr before returning NULL,
 * `n` is used to mark the error in code */
static void *unexpected(const Token *tok, int n)
{
	fprintf(stderr, "[%d] unexpected %s %s%s%sat %u:%u\n",
		n, token_type_str(tok->type),
		(tok->s != NULL) ? "(" : "",
		(tok->s != NULL) ? tok->s : "",
		(tok->s != NULL) ? ") " : "",
		tok->line, tok->column);
	return NULL;
}

/* any chain of instructions that results in a value */
static const Token *expression(const Token *tok)
{
	if (tok->type == TOK_INTEGER)
		return tok + 1;
	if (tok->type == TOK_STRING)
		return tok + 1;
	if (tok->type == TOK_WORD)
		return tok + 1;
	return unexpected(tok, 20);
}

static const Token *keyword_fn(const Token *tok)
{
	tok += 1;
	if (tok->type != TOK_WORD)
		return unexpected(tok, 0);
	const Token *name = tok;
	tok += 1;
	(void)name;
	if (tok->type != TOK_PAREN_OPEN)
		return unexpected(tok, 1);
	tok += 1;
	size_t args = 0;
	while (tok->type == TOK_WORD) {
		tok += 1;
		args += 1;
		if (tok->type == TOK_COMMA)
			tok += 1;
	}
	if (tok->type != TOK_PAREN_CLOS)
		return unexpected(tok, 2);
	printf("%zu args\n", args);
	return tok + 1;
}

/* mutable variable declaration */
static const Token *keyword_var(Scope *scope, const Token *tok)
{
	tok += 1;
	if (tok->type != TOK_WORD)
		return unexpected(tok, 10);
	const Token *name = tok;
	(void)name;
	tok += 1;
	/* no initialization */
	if (tok->type == TOK_SEMICOLON) {
		if (scope_insert(scope, name->s, 0))
			return NULL;
		return tok + 1;
	}
	if (tok->type != TOK_ASSIGN)
		return unexpected(tok, 11);
	tok = expression(tok + 1);
	if (tok == NULL)
		return NULL;
	if (tok->type != TOK_SEMICOLON)
		return unexpected(tok, 12);
	if (scope_insert(scope, name->s, 0))
		return NULL;
	return tok + 1;
}

/* constant variable declaration */
static const Token *keyword_const(Scope *scope, const Token *tok)
{
	tok += 1;
	if (tok->type != TOK_WORD)
		return unexpected(tok, 10);
	const Token *name = tok;
	(void)name;
	tok += 1;
	if (tok->type != TOK_ASSIGN)
		return unexpected(tok, 11);
	tok = expression(tok + 1);
	if (tok == NULL)
		return NULL;
	if (tok->type != TOK_SEMICOLON)
		return unexpected(tok, 12);
	if (scope_insert(scope, name->s, 0))
		return NULL;
	return tok + 1;
}