<?php

namespace App\Gui;

/** Sizes, durations and XAPI dates as XenCenter writes them. */
final class Units
{
    /** seconds added to UTC to show local times (0: UTC; set from the system when it is known) */
    public static int $tzOffset = 0;

    /** The time zone of this computer (TZ, /etc/timezone, /etc/localtime), so that dates show in local time: once at start. */
    public static function useLocalTime(): void
    {
        $zone = (string)getenv('TZ');
        if ($zone === '' && is_readable('/etc/timezone')) {
            $zone = trim((string)file_get_contents('/etc/timezone'));
        }
        if ($zone === '' && is_link('/etc/localtime') && preg_match('#zoneinfo/(.+)$#', (string)readlink('/etc/localtime'), $m)) {
            $zone = $m[1];
        }
        if ($zone !== '' && in_array(ltrim($zone, ':'), timezone_identifiers_list(), true)) {
            date_default_timezone_set(ltrim($zone, ':'));
        }
        self::$tzOffset = (int)date('Z');
    }

    public static function bytes(float $bytes, int $decimals = 1): string
    {
        $units = ['B', 'KB', 'MB', 'GB', 'TB', 'PB'];
        $i = 0;
        while (abs($bytes) >= 1024 && $i < count($units) - 1) {
            $bytes /= 1024;
            $i++;
        }
        return ($i === 0 ? (string)round($bytes) : number_format($bytes, $bytes >= 100 ? 0 : $decimals, '.', '')) . ' ' . $units[$i];
    }

    /** "20261110T12:34:56Z" (XAPI) -> seconds since 1970, 0 for none */
    public static function time(string $xapi): int
    {
        if ($xapi === '' || str_starts_with($xapi, '1970')) {
            return 0;
        }
        $t = strtotime(str_replace('T', ' ', rtrim($xapi, 'Z')) . ' UTC');
        return $t === false ? 0 : $t;
    }

    /** A time of the logs: the same form for events and alerts, in the computer's time zone. */
    public static function stamp(int $time): string
    {
        return $time <= 0 ? '' : date('M j, Y H:i:s', $time);
    }

    public static function date(string $xapi): string
    {
        $t = self::time($xapi);
        return $t === 0 ? 'Never' : date('M j, Y H:i:s', $t);
    }

    public static function duration(int $seconds): string
    {
        if ($seconds <= 0) {
            return '';
        }
        $days = intdiv($seconds, 86400);
        $hours = intdiv($seconds % 86400, 3600);
        $minutes = intdiv($seconds % 3600, 60);
        $out = [];
        if ($days > 0) {
            $out[] = $days . ($days === 1 ? ' day' : ' days');
        }
        if ($hours > 0) {
            $out[] = $hours . ($hours === 1 ? ' hour' : ' hours');
        }
        if ($days === 0) {
            $out[] = $minutes . ($minutes === 1 ? ' minute' : ' minutes');
        }
        return implode(' ', $out);
    }

    /** "2.4 GHz" from cpu_info speed "2394.454" (MHz) */
    public static function mhz(string $speed): string
    {
        $mhz = (float)$speed;
        return $mhz >= 1000 ? number_format($mhz / 1000, 2) . ' GHz' : round($mhz) . ' MHz';
    }
}