Profiler

<?php

namespace Meta\Library\Development;

use Meta\Common\Collections\Collection;

/**
 * Class Timer
 *
 * Inspired by javscripts console.time/console.timeEnd
 *
 * Timer::start('foobar') - sets a label and stashes the microtime(true)
 * Timer::stop('foobar') - sets a stop label and returns the time in microseconds
 *
 * Note: successive calls to stop will overrite previous labels and return the time
 *
 * So you can do
 *
 * Timer::start('foobar')
 *
 * sleep(1)
 *
 * Time::stop('foobar') - time from start at this point
 *
 * sleep(1);
 *
 * Time::stop('foobar') - time from start at *this* point
 *
 * @package Meta\Library\Development
 */
class ProfileTimer
{

    /**
     * Timer constructor.
     */
    public function __construct()
    {
        $this->startTimes = new Collection();
        $this->stopTimes = new Collection();
    }

    /**
     * @var ProfileTimer $instance
     */
    protected static $instance;

    /**
     * @var Collection of start times, $label => microtime(true)
     */
    private $startTimes;

    /**
     * @var Collection $stopTimes - array of $label => microtime(true)
     */
    private $stopTimes;

    /**
     * Set start time for label
     *
     * @param string $label
     *
     * @return ProfileTimer
     */
    public static function start($label)
    {
        self::init();

        // Set a start time label with current microtime
        self::$instance->startTimes->set($label, microtime(true));

        return self::$instance;
    }

    /**
     * Set a stop time for a label
     *
     * @param string $label
     *
     * @return string|null
     */
    public static function stop($label)
    {
        self::init();

        self::$instance->stopTimes->set($label, microtime(true));

        if (self::$instance->startTimes->has($label)) {
            $startTime = self::$instance->startTimes->get($label);
            $stopTime = self::$instance->stopTimes->get($label);

            return ($stopTime - $startTime) * 1000 .'ms';
        }

        return null;
    }

    /**
     * Initialise the instance property with an instance of Timer
     *
     * Will only initialise once so can be safely called multiple times
     *
     * @return ProfileTimer
     */
    private static function init()
    {
        if (!self::$instance) {
            self::$instance = new self();
        }

        return self::$instance;
    }

    /**
     * Return an array consisting of labels and times in milliseconds.
     *
     * Only complete pairs will be returned (where we have both a start/stop label)
     *
     * In the case where multiple stops where used it will return the difference of the *last* stop
     *
     * @return array
     */
    public static function allMetrics()
    {
        self::init();

        $results = [];
        foreach (self::$instance->startTimes as $key => $value) {
            $startTime = self::$instance->startTimes->get($key, false);
            $stopTime = self::$instance->stopTimes->get($key, false);

            if ($startTime !== false && $stopTime !== false) {
                $startTime = self::$instance->startTimes->get($key);
                $stopTime = self::$instance->stopTimes->get($key);

                $results[$key] = ($stopTime - $startTime) * 1000;
            }
        }

        return $results;
    }

}