#!/usr/local/bin/php
<?php

class OperationOrder {
    private $equations;

    public function __construct() {
        $in = file(__DIR__.'/input.txt');
        $this->equations = array_map('trim', $in);
    }

    public function part1() : int
    {
        $result = 0;
        foreach ($this->equations as $eq) {
            $result += $this->evaluate($eq);
        }
        return $result;
    }

    public function evaluate($eq) : int
    {
        return intval(preg_replace_callback_array(
            [
                '/^(.*)\(([\d *+]+)\)(.*)$/' => function($match) {
                    return $this->evaluate($match[1].$this->evaluate($match[2]).$match[3]);
                },
                '/^(.*) \+ ([\d]+)$/' => function ($match) {
                    return $this->evaluate($match[1]) + $match[2];
                },
                '/^(.*) \* ([\d]+)$/' => function ($match) {
                    return $this->evaluate($match[1]) * $match[2];
                },
            ],
            $eq
        ));
    }

    public function part2() : int
    {
        $result = 0;
        foreach ($this->equations as $eq) {
            $result += $this->evaluate2($eq);
        }
        return $result;
    }

    public function evaluate2($eq) : int
    {
        return intval(preg_replace_callback_array(
            [
                '/^(.*)\(([\d *+]+)\)(.*)$/' => function($match) {
                    return $this->evaluate2($match[1].$this->evaluate2($match[2]).$match[3]);
                },
                '/^(.* )?([\d]+) \+ ([\d]+)(.*)$/' => function ($match) {
                    return $this->evaluate2($match[1].$match[2] + $match[3].$match[4]);
                },
                '/^([\d *]+) \* ([\d]+)$/' => function ($match) {
                    return $this->evaluate2($match[1]) * $match[2];
                },
            ],
            $eq
        ));
    }
}

$oo = new OperationOrder();
$part1 = $oo->part1();
echo("Part 1: $part1\n");
$part2 = $oo->part2();
echo("Part 2: $part2\n");