/* 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 <stdlib.h>
#include <string.h>
#include <aplwc.h>
#include "aplwc_internal.h"

struct completion_state {
	const struct aplwc *aplwc;
	int num;
	const char *word;
	const int wordlen;
};

static char **generate(struct aplwc *, const char *, char *(*)(struct completion_state *));
static char *completions_syscmd(struct completion_state *);

char **
aplwc_autocomplete(struct aplwc *aplwc, const char *line, int start, int end)
{
	int len = end-start;
	char *word = malloc(sizeof(char) * len+1);
	char **completions = NULL;
	
	memcpy(word, line+start, len);
	word[len] = 0;

	struct aplwc_eval_context *context = aplwc_new_eval_context(aplwc);
	aplwc_scan_line(context, line);
	struct aplwc_token *tok = NULL;
	for(size_t i = 0; (i < context->n_tokens) && (tok == NULL); i++)
		if(((size_t)start >= context->tokens[i]->offset_start) && ((size_t)end <= context->tokens[i]->offset_end + 1))
			tok = context->tokens[i];

	if(tok)
		switch(tok->tag) {
		case APLWC_TOKEN_SYSCMD:
			completions = generate(aplwc, word, completions_syscmd);
			break;
		default:
			break;
		}
	free(word);

	aplwc_free_eval_context(context);
	return completions;
}

static char **
generate(struct aplwc *aplwc, const char *word, char *(*fn)(struct completion_state *))
{
	char **completions = NULL;
	struct completion_state state = {
		.aplwc = aplwc,
		.num = 0,
		.word = word,
		.wordlen = strlen(word),
	};

	char *c;
	int index = 0;
	while((c = fn(&state))){
		index++;
		completions = realloc(completions, sizeof(*completions) * (index + 1));
		completions[index-1] = c;
		completions[index] = NULL;
	}

	return completions;
}

static char *
completions_syscmd(struct completion_state *state)
{
	struct aplwc_syscmd *syscmd;

	while((syscmd = state->aplwc->syscmds[state->num++])){
		const char *name = syscmd->name;
		if(strncmp(name, state->word+1, state->wordlen-1) == 0){
			int len = strlen(name);
			char *result = malloc(sizeof(char) * (len + 2));
			result[0] = ')';
			memcpy(result+1, name, sizeof(char) * (len+1));
			return result;
		}
	}

	return NULL;
}