<?php
// ByteFormat.php
// Created: 2023-07-05
// Updated: 2023-07-05

namespace Index;

final class ByteFormat {
    /**
     * Whether the default behaviour for the format function is decimal (power of 10) or not (power of 2).
     *
     * @var bool
     */
    public const DECIMAL_DEFAULT = true;

    private const SYMBOLS = ['', 'K', 'M', 'G', 'T', 'P', 'E', 'Z', 'Y', 'R', 'Q'];
    private const DIV_DECIMAL = 1000;
    private const DIV_BINARY = 1024;

    /**
     * Formats a raw amount of bytes as a human readable string.
     *
     * @param int $bytes Number of bytes.
     * @param bool $decimal Whether format as a power of 10 (e.g. MB) or a power of 2 (e.g. MiB).
     * @return string Formatted byte string.
     */
    public static function format(int $bytes, bool $decimal = self::DECIMAL_DEFAULT): string {
        // this whole thing will be fun if i ever decide to do localisation
        if($bytes === 0)
            return 'Zero Bytes';

        $negative = $bytes < 0;
        $bytes = abs($bytes);

        $power = $decimal ? self::DIV_DECIMAL : self::DIV_BINARY;
        $exp = floor(log($bytes) / log($power));

        $number = $bytes / pow($power, $exp);
        $symbol = self::SYMBOLS[$exp];

        $string = '';
        if($negative)
            $string .= '-';

        if($bytes < $power)
            $string .= $number;
        else if($number < 10)
            $string .= sprintf('%.2f', $number);
        else
            $string .= sprintf('%.1f', $number);

        $string .= ' ' . $symbol;
        if($symbol === '') {
            $string .= 'Byte';
            if($number > 1)
                $string .= 's';
        } else {
            if(!$decimal)
                $string .= 'i';
            $string .= 'B';
        }

        return $string;
    }

    /**
     * Formats a raw amount of bytes as a human readable string in the power of 10 (e.g. MB).
     *
     * @param int $bytes Number of bytes.
     * @return string Formatted byte string.
     */
    public static function formatDecimal(int $bytes): string {
        return self::format($bytes, true);
    }

    /**
     * Formats a raw amount of bytes as a human readable string in the power of 2 (e.g. MiB).
     *
     * @param int $bytes Number of bytes.
     * @return string Formatted byte string.
     */
    public static function formatBinary(int $bytes): string {
        return self::format($bytes, false);
    }
}