<?php
$input_file = '../inputs/day7.txt';
if (file_exists($input_file)) {
	$input = file_get_contents($input_file);
	if ($input != null) {
		$bag_rules = explode("\n", $input);
		print 'Part 1 answer: ' . solve_part_one($bag_rules) . "\n";
		print 'Part 2 answer: ' . solve_part_two($bag_rules) . "\n";
	}
}

function solve_part_one(array $bag_rules): int
{
	return count(get_parent_colors(parse_bag_rules($bag_rules), 'shiny gold'));
}

function solve_part_two(array $bag_rules): int
{
	return get_content_count(parse_bag_rules($bag_rules), 'shiny gold') - 1;
}

function get_content_count(array $rules, string $color): int
{
	$ret = 0;

	foreach ($rules[$color] as $content_color => $count)
		$ret += $count * get_content_count($rules, $content_color);

	return $ret + 1;
}

function get_parent_colors(array $rules, string $color): array
{
	$ret = [];

	foreach ($rules as $parent_color => $content)
		if (array_key_exists($color, $content))
			$ret = array_merge($ret, [$parent_color], get_parent_colors($rules, $parent_color));

	return array_unique($ret);
}

function parse_bag_rules(array $bag_rules): array
{
	$ret = [];

	foreach ($bag_rules as $rule) {
		if (preg_match('/^(([a-z ]+) bags?) contain ([0-9a-z, ]+ bags?)+\.$/', trim($rule), $matches)) {
			[,, $color, $content] = $matches;
			if ($content === 'no other bags')
				$ret[$color] = [];
			elseif (preg_match_all('/((\d+) ([a-z ]+) bags?)+?,?/', trim($content), $content_matches, PREG_SET_ORDER)) {
				$parsed_content = [];
				foreach ($content_matches as $content_match) {
					[,, $content_qty, $content_color] = $content_match;
					$parsed_content[$content_color] = $content_qty;
				}
				$ret[$color] = $parsed_content;
			}
		}
	}

	return $ret;
}