/*
 * Copyright (c) Camden Dixie O'Brien
 * SPDX-License-Identifier: AGPL-3.0-only
 */

#include "parser.h"

#include <stdbool.h>
#include <stdlib.h>

#define SEQUENCE_START_CAPACITY 8

static bool is_special(char c)
{
	switch (c) {
	case '|':
	case '.':
		return true;
	default:
		return false;
	}
}

static int parse_literal(const char *input, int rem, char *out)
{
	if (rem > 0 && !is_special(input[0])) {
		*out = input[0];
		return 1;
	} else {
		return -1;
	}
}

static int parse_term(const char *input, int rem, term_t *out)
{
	int result, used = 0;

	if (used < rem && '.' == input[0]) {
		out->type = TERM_TYPE_WILDCARD;
		++used;
	} else {
		result = parse_literal(input + used, rem - used, &out->literal);
		if (result < 0)
			return -1;
		out->type = TERM_TYPE_LITERAL;
		used += result;
	}

	out->quantifier = QUANTIFIER_NONE;

	return used;
}

static int parse_sequence(const char *input, int rem, sequence_t *out)
{
	int result, used = 0;

	out->len = 0;
	out->capacity = SEQUENCE_START_CAPACITY;
	out->contents = calloc(out->capacity, sizeof(term_t));
	if (NULL == out->contents)
		return -1;

	while (used < rem) {
		if (out->len >= out->capacity) {
			out->capacity *= 2;
			out->contents
			    = realloc(out->contents, out->capacity * sizeof(term_t));
			if (NULL == out->contents)
				return -1;
		}

		result
		    = parse_term(input + used, rem - used, &out->contents[out->len]);
		if (result < 0)
			break;
		++out->len;
		used += result;
	}

	return out->len > 0 ? used : -1;
}

int parse_regex(const char *input, int rem, regex_t *out)
{
	int result, used = 0;

	result = parse_sequence(input + used, rem - used, &out->sequence);
	if (result < 0)
		return -1;
	used += result;

	if (used < rem) {
		if (input[used] != '|')
			return -1;
		++used;

		out->alternative = calloc(1, sizeof(regex_t));
		if (NULL == out->alternative)
			return -1;
		result = parse_regex(input + used, rem - used, out->alternative);
		if (result < 0)
			return -1;
		used += result;
	}

	return used;
}