<?php

function usage() {
    print("Usage: php dice.php <roll_string> [print_flag]\n");
}

function roll($sides, $num, $print) {
    $sum = 0;
    if ($print) {
        if ($num == 1) {
            print("Rolling 1 $sides-sided die.\n");
        }
        else {
            print("Rolling $num $sides-sided dice.\n");
        }
    }
    for ($count = 0; $count < $num; $count++) {
        $sum += mt_rand(1, $sides);
    }
    if ($print) {
        print("Result: $sum\n-------\n");
    }
    return $sum;
}

function roll_string($string, $print) {
    $clause = '((\d)+(d(\d+))?)';
    $join = '(\s*[\+-]\s*)';
    $first_clause = "^$join?$clause";
    $match = "$first_clause($join$clause)*$";
    if (!preg_match("/$match/", $string)) {
        print("Malformed string.\n");
        return FALSE;
    }
    $total = 0;
    while (preg_match("/$first_clause/", $string, $matches)) {
        if (count($matches) == 6) {
            $clause_val = roll($matches[5], $matches[3], $print);
        }
        else {
            $clause_val = $matches[3];
        }
        if (preg_match('/\s*-\s*/', $matches[1])) {
            $clause_val *= -1;
        }
        $total += $clause_val;
        $string = preg_replace("/$first_clause/", '', $string);
    }
    return $total;
}

$print = 1;
if (count($argv) == 3) {
    $print = $argv[2];
}
elseif (count($argv) != 2) {
    usage();
    return;
}

$total = roll_string($argv[1], $print);
if ($total !== FALSE) {
    print("Total: $total\n");
}