mensa_slow_clock.php

<?php
	
	class SlowClockCalculator {
		
		private $target_hour   = 0;
		private $target_minute = 0;
		private $slow = 0;
		private $difference = 0;
		private $result = 0;
		
		public function __construct($target, $slow, $difference = 0) {
			list($this->target_hour, $this->target_minute) = explode(':', $target);
			$this->slow = $slow;
			$this->difference = $difference;
		}
		
		private function getHour($i) {
			return floor($i / 60);
		}
		
		private function getMinutes($i) {
			return $i % 60;
		}
		
		private function targetIsMet($i) {
			return $this->getHour($i) == $this->target_hour && $this->getMinutes($i) == $this->target_minute;
		}
		
		public function calculate() {
			$a = 0; $b = 0;
			for ($hour = 0; $hour < 24; $hour++) {
				for ($minute = 0; $minute < 60; $minute++) {
					if ($this->targetIsMet($b)) { return $this->result = $a + $this->difference; }
					$a++; $b++;
					if ($minute == 0) { $b -= $this->slow; }
				}
			}
		}
		
		public function getResult() {
			return sprintf("%'02u:%'02u", $this->getHour($this->result), $this->getMinutes($this->result));
		}
		
	}
	
	class SlowClockCalculatorTest extends PHPUnit_Framework_TestCase {
		
		public static function data() {
			return array (
				array ('0:00',  '0', '0',  '00:00'),
				array ('00:00', '0', '0',  '00:00'),
				array ('19:57', '3', '90', '22:30'),
				array ('19:57', '3', '80', '22:20'),
				array ('19:50', '3', '80', '22:13'),
			);
		}
		
		/**
		 * @dataProvider data
		 */
		public function testCalculate($target, $slow, $difference, $result) {
			$c = new SlowClockCalculator($target, $slow, $difference);
			$c->calculate();
			$this->assertEquals($result, $c->getResult());
		}
		
	}