<?php
// Stopwatch.php
// Created: 2021-04-26
// Updated: 2022-02-16

namespace Index\Performance;

/**
 * Provides a means to measure elapsed time at a high resolution.
 */
class Stopwatch {
    private int|float $start = -1;
    private int|float $elapsed = 0;
    private int|float $frequency;

    public function __construct() {
        $this->frequency = PerformanceCounter::getFrequency();
    }

    public function start(): void {
        if($this->start < 0)
            $this->start = PerformanceCounter::getTicks();
    }

    public function stop(): void {
        if($this->start < 0)
            return;
        $this->elapsed += PerformanceCounter::getTicksSince($this->start);
        $this->start = -1;
    }

    /**
     * Checks whether the Stopwatch is currently running.
     *
     * @return bool true if the Stopwatch is running, false if not.
     */
    public function isRunning(): bool {
        return $this->start >= 0;
    }

    /**
     * Gets the number of ticks that have elapsed.
     *
     * @return int|float Number of ticks.
     */
    public function getElapsedTicks(): int|float {
        $elapsed = $this->elapsed;
        if($this->start >= 0)
            $elapsed += PerformanceCounter::getTicksSince($this->start);
        return $elapsed;
    }

    /**
     * Gets the number of elapsed milliseconds.
     *
     * @return float Number of elapsed milliseconds.
     */
    public function getElapsedTime(): float {
        return $this->getElapsedTicks() / $this->frequency;
    }

    /**
     * Creates a new Stopwatch instance and starts measuring time.
     *
     * @return Stopwatch Newly created running Stopwatch.
     */
    public static function startNew(): Stopwatch {
        $sw = new Stopwatch;
        $sw->start();
        return $sw;
    }
}