advent-of-code/2020/day4.php

<?php

use JetBrains\PhpStorm\Pure;

$input_file = '../inputs/day4.txt';
if (file_exists($input_file)) {
	$input = file_get_contents($input_file);
	if ($input != null) {
		$credentials = explode("\n", $input);
		print 'Part 1 answer: ' . solve_part_one($credentials) . "\n";
		print 'Part 2 answer: ' . solve_part_two($credentials) . "\n";
	}
}

#[Pure] function solve_part_one(array $credentials): int
{
	return count(get_valid_passports($credentials));
}

function solve_part_two(array $credentials): int
{
	return count(get_valid_passports_with_valid_fields($credentials));
}

function get_valid_passports_with_valid_fields(array $credentials): array
{
	function validate_year(string $value, int $min, int $max): bool
	{
		preg_match('/^(\d{4})$/', $value, $matches);
		[$match, $year] = $matches;
		if (($match && ($year >= $min && $year <= $max)))
			return true;
		else
			return false;
	}

	function validate_height(string $value): bool
	{
		if (preg_match('/^(\d.+?)(cm|in)$/', $value, $matches) > 0) {
			if (($matches[2] == 'cm' && $matches[1] >= 150 && $matches[1] <= 193) || ($matches[2] == 'in' && $matches[1] >= 59 && $matches[1] <= 76))
				return true;
		}

		return false;
	}

	$validate_hair_color = fn ($value) => preg_match('/^#([a-f0-9]{6})$/', $value);

	$validate_eye_color = fn ($value) => preg_match('/^(amb|blu|brn|gry|grn|hzl|oth)$/', $value);

	$validate_pid = fn ($value) => preg_match('/^0*(\d{9})$/', $value);

	$valid_passports = [];
	$passports = get_valid_passports($credentials);

	foreach ($passports as $passport) {
		$valid = true;
		foreach ($passport as $field => $value) {
			switch ($field) {
				case 'byr':
					if (!validate_year($value, 1920, 2002))
						$valid = false;
					break;
				case 'iyr':
					if (!validate_year($value, 2010, 2020))
						$valid = false;
					break;
				case 'eyr':
					if (!validate_year($value, 2020, 2030))
						$valid = false;
					break;
				case 'hgt':
					if (!validate_height($value))
						$valid = false;
					break;
				case 'hcl':
					if (!$validate_hair_color($value))
						$valid = false;
					break;
				case 'ecl':
					if (!$validate_eye_color($value))
						$valid = false;
					break;
				case 'pid':
					if (!$validate_pid($value))
						$valid = false;
					break;
			}
		}

		if ($valid)
			$valid_passports[] = $passport;
	}

	return $valid_passports;
}

#[Pure] function get_valid_passports(array $credentials): array
{
	$passports = parse_passports($credentials);
	$required_fields = ['byr', 'iyr', 'eyr', 'hgt', 'hcl', 'ecl', 'pid'];
	$valid_passports = [];

	foreach ($passports as $passport) {
		$valid = true;
		foreach ($required_fields as $required_field) {
			if (!array_key_exists($required_field, $passport))
				$valid = false;
		}

		if ($valid)
			$valid_passports[] = $passport;
	}

	return $valid_passports;
}

#[Pure] function parse_passports(array $credentials): array
{
	$passports = [];
	$current_credentials = [];
	for ($i = 0; $i < count($credentials); $i++) {
		$cred = trim($credentials[$i]);
		if ($cred == '') {
			$passports[] = parse_single_passport($current_credentials);
			$current_credentials = [];
		} else
			$current_credentials[] = $cred;
	}

	if (count($current_credentials) != 0)
		$passports[] = parse_single_passport($current_credentials);

	return $passports;
}

function parse_single_passport(array $fields): array
{
	$passport = [];

	foreach ($fields as $fieldlist) {
		$kvps = explode(' ', $fieldlist);
		foreach ($kvps as $kvp) {
			[$field, $value] = explode(':', $kvp);
			$passport[$field] = $value;
		}
	}

	return $passport;
}