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<?php

    namespace Donut;


    class Period
    {
        /** @var int|NULL  in minutes */
        private $interval;


        /**
         * @param  int|NULL
         */
        public function __construct($interval = NULL)
        {
            $this->interval = $interval;
        }


        /**
         * @return  int|NULL
         */
        public function getInterval()
        {
            return $this->interval;
        }


        /**
         * @param  string
         * @return static
         */
        public static function every($interval)
        {
            $interval = explode(' ', $interval);
            $minutes = 0;

            foreach ($interval as $part) {
                $num = substr($part, 0, -1);
                $unit = substr($part, -1);

                if ($unit === 'h') {
                    $num *= 60;

                } elseif ($unit === 'm') { // nothing
                    // nothing

                } else {
                    $num = $part;
                }

                $minutes += $num;
            }

            $period = new static($minutes);
            return $period;
        }
    }