<?php
$input_file = '../inputs/day14.txt';
if (file_exists($input_file)) {
	$input = file_get_contents($input_file);
	if ($input != null) {
		$instructions = array_map('trim', explode("\n", $input));
		print 'Part 1 answer: ' . solve_part_one($instructions) . "\n";
		print 'Part 2 answer: ' . solve_part_two($instructions) . "\n";
	}
}

function solve_part_one(array $instructions): int
{
	$parsed = parse_instructions($instructions);
	$mask = '';
	$mem = [];
	foreach ($parsed as $instruction) {
		if ($instruction[0] === 'mask')
			$mask = $instruction[1];
		else
			$mem[$instruction[1]] = apply_mask($mask, $instruction[2]);
	}

	return array_sum($mem);
}

function solve_part_two(array $instructions): int
{
	$parsed = parse_instructions($instructions);
	$mask = '';
	$mem = [];
	foreach ($parsed as $instruction) {
		if ($instruction[0] === 'mask')
			$mask = $instruction[1];
		else {
			foreach (apply_mask_two($mask, $instruction[1]) as $address)
				$mem[$address] = $instruction[2];
		}
	}

	return array_sum($mem);
}

function apply_mask_two(string $mask, int $num): array
{
	$addresses = [''];
	$bin = str_pad(decbin($num), 36, '0', STR_PAD_LEFT);
	for ($i = 0; $i < strlen($bin); $i++) {
		switch ($mask[$i]) {
			case '0':
				$addresses = array_map(fn ($addr) => $addr . $bin[$i], $addresses);
				break;
			case '1':
				$addresses = array_map(fn ($addr) => $addr . '1', $addresses);
				break;
			case 'X':
				$new_addresses = [];
				foreach ($addresses as $address) {
					$new_addresses[] = $address . '0';
					$new_addresses[] = $address . '1';
				}
				$addresses = $new_addresses;
				break;
		}
	}
	return array_map('bindec', $addresses);
}

function apply_mask(string $mask, int $num): int
{
	$bin = str_pad(decbin($num), 36, '0', STR_PAD_LEFT);
	for ($i = 0; $i < strlen($bin); $i++)
		if ($mask[$i] != 'X')
			$bin[$i] = $mask[$i];
	return bindec($bin);
}

function parse_instructions(array $instructions): array
{
	$parsed_instructions = [];
	foreach ($instructions as $instruction) {
		[$inst, $arg] = array_map('trim', explode(' = ', $instruction));
		if ($inst === 'mask')
			$parsed_instructions[] = [$inst, $arg];
		else
			$parsed_instructions[] = ['mem', substr($inst, 4, strlen($inst) - 5), $arg];
	}
	return $parsed_instructions;
}