/* Aplwc - A Programming Language With Constraints
 *
 * Copyright (C) 2026 Peter Mikkelsen <petermikkelsen10@gmail.com>
 *
 * This file is part of aplwc.
 *
 * Aplwc is free software: you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation, either version 3 of the License, or
 * (at your option) any later version.
 *
 * Aplwc is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with aplwc.  If not, see <https://www.gnu.org/licenses/>.
 */

#include <stdio.h>
#include <string.h>
#include <aplwc.h>
#include "aplwc_internal.h"

static enum aplwc_token_tag peek(struct aplwc_eval_context *);
static struct aplwc_token *match(struct aplwc_eval_context *, enum aplwc_token_tag);
static void emit(struct aplwc_eval_context *, enum aplwc_ast_tag, struct aplwc_ast **);
static char *token_text(struct aplwc_eval_context *, struct aplwc_token *);
static void parse_syscmd(struct aplwc_eval_context *, struct aplwc_ast **);

void
aplwc_parse(struct aplwc_eval_context *context)
{
	context->token_offset = 0;

	if(peek(context) == APLWC_TOKEN_SYSCMD)
		parse_syscmd(context, &context->ast);

	if(context->ast == NULL)
		emit(context, APLWC_AST_ERROR, &context->ast);
}

static enum aplwc_token_tag
peek(struct aplwc_eval_context *context)
{
	enum aplwc_token_tag tag = -1;
	
	if(context->token_offset < context->n_tokens)
		tag = context->tokens[context->token_offset]->tag;
	return tag;
}

static struct aplwc_token *
match(struct aplwc_eval_context *context, enum aplwc_token_tag tag)
{
	struct aplwc_token *tok = NULL;
	
	if(peek(context) == tag)
		tok = context->tokens[context->token_offset++];
	return tok;
}

static void
emit(struct aplwc_eval_context *context, enum aplwc_ast_tag tag, struct aplwc_ast **ast)
{
	if((*ast) != NULL)
		aplwc_free_ast(context->aplwc, *ast);
	
	*ast = context->aplwc->alloc(sizeof(**ast));
	memset(*ast, 0, sizeof(**ast));
	(*ast)->tag = tag;
}

static char *
token_text(struct aplwc_eval_context *context, struct aplwc_token *tok)
{
	size_t len = tok->offset_end - tok->offset_start + 1;
	char *text = context->aplwc->alloc(len + 1);
	memcpy(text, context->text + tok->offset_start, len);
	text[len] = 0;
	return text;
}

static void
parse_syscmd(struct aplwc_eval_context *context, struct aplwc_ast **ast)
{
	struct aplwc_token *tok = match(context, APLWC_TOKEN_SYSCMD);

	char *name = token_text(context, tok);
	struct aplwc_syscmd *syscmd = aplwc_lookup_syscmd(context->aplwc, name+1);
	context->aplwc->free(name);
	
	if(syscmd){
		emit(context, APLWC_AST_SYSCMD, ast);
		(*ast)->data.syscmd.syscmd = syscmd;
		(*ast)->data.syscmd.args = aplwc_strdup(context->aplwc, "");
	}else
		emit(context, APLWC_AST_ERROR, ast);
}