<?php

namespace App\Rules;

use Closure;
use Illuminate\Contracts\Validation\ValidationRule;
use Illuminate\Http\UploadedFile;

class ValidAudioMagicBytes implements ValidationRule
{
    // Signatures checked at byte offset 0
    private const SIGNATURES = [
        [0xFF, 0xFB],             // MP3 MPEG-1 Layer 3
        [0xFF, 0xF3],             // MP3 MPEG-2 Layer 3
        [0xFF, 0xF2],             // MP3 MPEG-2.5 Layer 3
        [0xFF, 0xF1],             // AAC ADTS MPEG-4
        [0xFF, 0xF9],             // AAC ADTS MPEG-2
        [0x49, 0x44, 0x33],       // MP3 with ID3v2 tag
        [0x52, 0x49, 0x46, 0x46], // WAV (RIFF header)
        [0x4F, 0x67, 0x67, 0x53], // OGG (OggS)
        [0x66, 0x4C, 0x61, 0x43], // FLAC (fLaC)
        [0x1A, 0x45, 0xDF, 0xA3], // WebM / MKV
    ];

    // MP4/M4A: ISO Base Media file — 'ftyp' box starts at byte offset 4
    private const MP4_SIGNATURE = [0x66, 0x74, 0x79, 0x70]; // 'ftyp'
    private const MP4_OFFSET    = 4;

    public function validate(string $attribute, mixed $value, Closure $fail): void
    {
        if (! ($value instanceof UploadedFile) || ! $value->isValid()) {
            $fail('Fail audio tidak sah.');
            return;
        }

        $handle = @fopen($value->getRealPath(), 'rb');
        if ($handle === false) {
            $fail('Fail audio tidak dapat dibaca.');
            return;
        }

        $header = fread($handle, 12);
        fclose($handle);

        if (strlen($header) < 4) {
            $fail('Fail audio terlalu kecil atau rosak.');
            return;
        }

        $bytes = array_values(unpack('C*', $header));

        foreach (self::SIGNATURES as $sig) {
            if ($this->matchesAt($bytes, $sig, 0)) {
                return;
            }
        }

        // Check MP4/M4A: need at least 8 bytes
        if (count($bytes) >= self::MP4_OFFSET + count(self::MP4_SIGNATURE)) {
            if ($this->matchesAt($bytes, self::MP4_SIGNATURE, self::MP4_OFFSET)) {
                return;
            }
        }

        $fail('Format fail audio tidak sah. Kandungan fail tidak menepati format audio yang dibenarkan.');
    }

    private function matchesAt(array $bytes, array $signature, int $offset): bool
    {
        foreach ($signature as $i => $expected) {
            if (($bytes[$offset + $i] ?? -1) !== $expected) {
                return false;
            }
        }
        return true;
    }
}