<?php

namespace App\Services;

use App\Core\Database;
use App\Core\Security;

/**
 * Universal Video Management & Streaming Service
 * Supports:
 * 1. Direct Server API Upload & HTTP 206 Partial Content Range Streaming
 * 2. Server-Side Automated FFmpeg HLS Transcoding (.m3u8 master playlist + .ts chunks)
 * 3. Bunny.net Stream Cloud Video CDN, TUS upload, and SHA256 DRM Token Signing
 */
class VideoService
{
    private static bool $schemaChecked = false;

    /**
     * Ensure database columns for dual storage exist in `lessons` table
     */
    public static function ensureSchema(): void
    {
        if (self::$schemaChecked) {
            return;
        }

        try {
            // Check if storage_type column exists
            $cols = Database::select("SHOW COLUMNS FROM lessons LIKE 'storage_type'");
            if (empty($cols)) {
                Database::query("ALTER TABLE lessons ADD COLUMN storage_type ENUM('bunny_stream', 'api_upload', 'external_url') NOT NULL DEFAULT 'bunny_stream' AFTER sequence_order");
            }

            $colsUuid = Database::select("SHOW COLUMNS FROM lessons LIKE 'video_uuid'");
            if (empty($colsUuid)) {
                Database::query("ALTER TABLE lessons ADD COLUMN video_uuid CHAR(36) NULL AFTER storage_type");
            }

            $colsCurriculumKey = Database::select("SHOW COLUMNS FROM lessons LIKE 'curriculum_key'");
            if (empty($colsCurriculumKey)) {
                Database::query("ALTER TABLE lessons ADD COLUMN curriculum_key VARCHAR(500) NULL AFTER title");
                Database::query("ALTER TABLE lessons ADD INDEX idx_lessons_curriculum_key (curriculum_key)");
            }

            $colsPath = Database::select("SHOW COLUMNS FROM lessons LIKE 'local_path'");
            if (empty($colsPath)) {
                Database::query("ALTER TABLE lessons ADD COLUMN local_path VARCHAR(500) NULL AFTER bunny_video_id");
            }

            $colsR2 = Database::select("SHOW COLUMNS FROM lessons LIKE 'r2_url'");
            if (empty($colsR2)) {
                Database::query("ALTER TABLE lessons ADD COLUMN r2_url VARCHAR(500) NULL AFTER local_path");
            }

            $colsHls = Database::select("SHOW COLUMNS FROM lessons LIKE 'hls_url'");
            if (empty($colsHls)) {
                Database::query("ALTER TABLE lessons ADD COLUMN hls_url VARCHAR(500) NULL AFTER local_path");
            }

            $colsThumb = Database::select("SHOW COLUMNS FROM lessons LIKE 'thumbnail_url'");
            if (empty($colsThumb)) {
                Database::query("ALTER TABLE lessons ADD COLUMN thumbnail_url VARCHAR(500) NULL AFTER hls_url");
            }

            $colsStatus = Database::select("SHOW COLUMNS FROM lessons LIKE 'encoding_status'");
            if (empty($colsStatus)) {
                Database::query("ALTER TABLE lessons ADD COLUMN encoding_status ENUM('pending', 'processing', 'ready', 'failed') NOT NULL DEFAULT 'ready' AFTER is_free_preview");
            }

            // Progress is used by the student player. Create only this additive
            // table at runtime so production does not need the destructive full schema.
            Database::query("CREATE TABLE IF NOT EXISTS lesson_progress (
                id BIGINT UNSIGNED NOT NULL AUTO_INCREMENT,
                student_id BIGINT UNSIGNED NOT NULL,
                lesson_id BIGINT UNSIGNED NOT NULL,
                position_seconds INT UNSIGNED NOT NULL DEFAULT 0,
                watched_seconds INT UNSIGNED NOT NULL DEFAULT 0,
                completion_percentage DECIMAL(5,2) NOT NULL DEFAULT 0.00,
                is_completed TINYINT(1) NOT NULL DEFAULT 0,
                last_seen_at TIMESTAMP NULL DEFAULT CURRENT_TIMESTAMP,
                completed_at TIMESTAMP NULL DEFAULT NULL,
                PRIMARY KEY (id),
                UNIQUE KEY idx_progress_student_lesson (student_id, lesson_id),
                KEY idx_progress_lesson (lesson_id),
                CONSTRAINT fk_progress_student FOREIGN KEY (student_id) REFERENCES students (id) ON DELETE CASCADE,
                CONSTRAINT fk_progress_lesson FOREIGN KEY (lesson_id) REFERENCES lessons (id) ON DELETE CASCADE
            ) ENGINE=InnoDB DEFAULT CHARSET=utf8mb4 COLLATE=utf8mb4_unicode_ci");

            self::$schemaChecked = true;
        } catch (\Throwable $e) {
            error_log("VideoService schema ensure note: " . $e->getMessage());
        }
    }

    /**
     * Detect FFmpeg path on server (Ubuntu, CentOS, macOS, CloudPanel)
     */
    public static function getFfmpegBinary(): ?string
    {
        $candidates = [
            '/usr/bin/ffmpeg',
            '/usr/local/bin/ffmpeg',
            '/opt/homebrew/bin/ffmpeg',
            'ffmpeg'
        ];

        foreach ($candidates as $bin) {
            $check = @shell_exec("which " . escapeshellarg($bin) . " 2>/dev/null");
            if (!empty($check) || (file_exists($bin) && is_executable($bin))) {
                return trim($check ?: $bin);
            }
        }
        return null;
    }

    // =========================================================================
    // METHOD 1: Direct Server API Upload & HTTP 206 Range Streaming
    // =========================================================================

    /**
     * Handles direct file upload from multipart request
     * 
     * @param array $file $_FILES['video']
     * @param int $courseId
     * @param string $title
     * @return array
     */
    public static function handleDirectUpload(array $file, int $courseId, string $title, bool $syncR2Immediately = false): array
    {
        self::ensureSchema();

        if (empty($file) || $file['error'] !== UPLOAD_ERR_OK) {
            $errorMsg = match ($file['error'] ?? -1) {
                UPLOAD_ERR_INI_SIZE   => 'حجم الفيديو يتجاوز الحد المسموح في إعدادات السيرفر (upload_max_filesize)',
                UPLOAD_ERR_FORM_SIZE  => 'حجم الفيديو يتجاوز الحد المسموح في النموذج',
                UPLOAD_ERR_PARTIAL    => 'تم رفع جزء من الملف فقط، يرجى إعادة المحاولة',
                UPLOAD_ERR_NO_FILE    => 'لم يتم تحديد أي ملف فيديو',
                default               => 'حدث خطأ أثناء استلام ملف الفيديو على السيرفر'
            };
            throw new \RuntimeException($errorMsg);
        }

        // Validate Extension & Mime
        $allowedMimes = ['video/mp4', 'video/webm', 'video/quicktime', 'video/x-matroska', 'video/ogg'];
        $finfo = finfo_open(FILEINFO_MIME_TYPE);
        $mime = finfo_file($finfo, $file['tmp_name']);
        finfo_close($finfo);

        $ext = strtolower(pathinfo($file['name'], PATHINFO_EXTENSION));
        $allowedExts = ['mp4', 'webm', 'mov', 'mkv', 'ogg'];

        if (!in_array($ext, $allowedExts) || !in_array($mime, $allowedMimes)) {
            throw new \InvalidArgumentException('نوع الملف غير مدعوم. الصيغ المدعومة هي: MP4, WebM, MOV, MKV.');
        }

        // Generate UUID & Target Directory
        $videoUuid = sprintf('%04x%04x-%04x-%04x-%04x-%04x%04x%04x',
            mt_rand(0, 0xffff), mt_rand(0, 0xffff),
            mt_rand(0, 0xffff),
            mt_rand(0, 0x0fff) | 0x4000,
            mt_rand(0, 0x3fff) | 0x8000,
            mt_rand(0, 0xffff), mt_rand(0, 0xffff), mt_rand(0, 0xffff)
        );

        $storageBase = dirname(__DIR__, 2) . '/storage/videos/' . $courseId;
        if (!is_dir($storageBase)) {
            mkdir($storageBase, 0755, true);
        }

        $targetFileName = $videoUuid . '.' . $ext;
        $targetPath = $storageBase . '/' . $targetFileName;

        $moved = is_uploaded_file($file['tmp_name'])
            ? move_uploaded_file($file['tmp_name'], $targetPath)
            : @rename($file['tmp_name'], $targetPath);
        if (!$moved && is_file($file['tmp_name'])) {
            $moved = @copy($file['tmp_name'], $targetPath);
            if ($moved) @unlink($file['tmp_name']);
        }
        if (!$moved) {
            throw new \RuntimeException('فشل حفظ ملف الفيديو على السيرفر، يرجى فحص أذونات المجلد.');
        }

        $relativePath = 'storage/videos/' . $courseId . '/' . $targetFileName;
        $fileSize = filesize($targetPath);

        // Attempt automated Server-Side HLS Transcoding
        $hlsResult = self::transcodeToHls($targetPath, $courseId, $videoUuid);

        // Automated sync to Cloudflare R2
        $r2Config = self::getR2Config();
        $r2VideoUrl = null;
        if ($syncR2Immediately && !empty($r2Config['access_key']) && !empty($r2Config['secret_key']) && !empty($r2Config['bucket'])) {
            $r2Key = "videos/{$courseId}/{$targetFileName}";
            $r2VideoUrl = self::uploadToR2($targetPath, $r2Key, $mime);

            // The player must receive a complete HLS package, not only the source MP4.
            if (!empty($hlsResult['hls_url'])) {
                $hlsDir = dirname(__DIR__, 2) . '/storage/hls/' . $courseId . '/' . $videoUuid;
                $r2HlsPlaylist = self::uploadHlsDirectoryToR2($hlsDir, $courseId, $videoUuid);
                if ($r2HlsPlaylist) {
                    $hlsResult['hls_url'] = $r2HlsPlaylist;
                }
            }

            $thumbnailPath = dirname(__DIR__, 2) . '/storage/hls/' . $courseId . '/' . $videoUuid . '/thumbnail.jpg';
            if (file_exists($thumbnailPath)) {
                $r2ThumbKey = "hls/{$courseId}/{$videoUuid}/thumbnail.jpg";
                $r2ThumbUrl = self::uploadToR2($thumbnailPath, $r2ThumbKey, 'image/jpeg');
                if ($r2ThumbUrl) {
                    $hlsResult['thumbnail_url'] = $r2ThumbUrl;
                }
            }
        }

        return [
            'video_uuid'      => $videoUuid,
            'local_path'      => $relativePath,
            'target_path'     => $targetPath,
            'target_file_name'=> $targetFileName,
            'r2_url'          => $r2VideoUrl,
            'hls_url'         => $hlsResult['hls_url'] ?? null,
            'thumbnail_url'   => $hlsResult['thumbnail_url'] ?? null,
            'duration'        => $hlsResult['duration_seconds'] ?? 0,
            'file_size'       => $fileSize,
            'mime_type'       => $mime,
            'extension'       => $ext,
            'storage_type'    => 'api_upload',
            'encoding_status' => $syncR2Immediately ? 'ready' : 'processing',
            'stream_url'      => '/api/videos/stream/' . $videoUuid
        ];
    }

    /**
     * Background Pipeline: Asynchronously sync local video & HLS chunks to Cloudflare R2
     */
    public static function syncLessonToR2(int $lessonId, int $courseId, string $targetPath, string $targetFileName, string $videoUuid, string $mime): array
    {
        $r2Config = self::getR2Config();
        if (empty($r2Config['access_key']) || empty($r2Config['secret_key']) || empty($r2Config['bucket'])) {
            return ['r2_url' => null, 'hls_url' => null];
        }

        $r2Key = "videos/{$courseId}/{$targetFileName}";
        $r2VideoUrl = self::uploadToR2($targetPath, $r2Key, $mime);

        $hlsDir = dirname(__DIR__, 2) . '/storage/hls/' . $courseId . '/' . $videoUuid;
        $r2HlsPlaylist = self::uploadHlsDirectoryToR2($hlsDir, $courseId, $videoUuid);

        $thumbnailPath = dirname(__DIR__, 2) . '/storage/hls/' . $courseId . '/' . $videoUuid . '/thumbnail.jpg';
        $r2ThumbUrl = null;
        if (file_exists($thumbnailPath)) {
            $r2ThumbKey = "hls/{$courseId}/{$videoUuid}/thumbnail.jpg";
            $r2ThumbUrl = self::uploadToR2($thumbnailPath, $r2ThumbKey, 'image/jpeg');
        }

        $updates = [];
        $params = [];
        if ($r2VideoUrl) {
            $updates[] = 'r2_url = ?';
            $params[] = $r2VideoUrl;
        }
        if ($r2HlsPlaylist) {
            $updates[] = 'hls_url = ?';
            $params[] = $r2HlsPlaylist;
        }
        if ($r2ThumbUrl) {
            $updates[] = 'thumbnail_url = ?';
            $params[] = $r2ThumbUrl;
        }
        if (!empty($updates)) {
            $params[] = $lessonId;
            Database::query('UPDATE lessons SET ' . implode(', ', $updates) . ' WHERE id = ?', $params);
        }

        return [
            'r2_url'        => $r2VideoUrl,
            'hls_url'       => $r2HlsPlaylist,
            'thumbnail_url' => $r2ThumbUrl,
        ];
    }

    /**
     * Transcode MP4 to HLS Chunks (.m3u8 and .ts segments) using Server FFmpeg
     */
    public static function transcodeToHls(string $sourceMp4Path, int $courseId, string $videoUuid): array
    {
        $ffmpeg = self::getFfmpegBinary();
        if (!$ffmpeg || !file_exists($sourceMp4Path)) {
            return [
                'hls_url'          => null,
                'thumbnail_url'    => null,
                'duration_seconds' => 0
            ];
        }

        $hlsOutputDir = dirname(__DIR__, 2) . '/storage/hls/' . $courseId . '/' . $videoUuid;
        if (!is_dir($hlsOutputDir)) {
            mkdir($hlsOutputDir, 0755, true);
        }

        $playlistPath = $hlsOutputDir . '/index.m3u8';
        $segmentPattern = $hlsOutputDir . '/segment_%03d.ts';
        $thumbnailPath = $hlsOutputDir . '/thumbnail.jpg';

        // Measure real video duration from input file
        $durationSeconds = 10;
        $probeCmd = "{$ffmpeg} -i " . escapeshellarg($sourceMp4Path) . " 2>&1";
        $probeOutput = @shell_exec($probeCmd);
        if ($probeOutput && preg_match('/Duration:\s*(\d{2}):(\d{2}):(\d{2})/i', $probeOutput, $m)) {
            $durationSeconds = ($m[1] * 3600) + ($m[2] * 60) + (int)$m[3];
        }
        if ($durationSeconds <= 0) {
            $durationSeconds = 10;
        }

        // 1. Generate Thumbnail Screenshot at 1 second (or 00:00:01)
        $thumbTime = ($durationSeconds > 2) ? '00:00:02' : '00:00:01';
        $thumbCmd = "{$ffmpeg} -ss {$thumbTime} -i " . escapeshellarg($sourceMp4Path) . " -vframes 1 -q:v 2 " . escapeshellarg($thumbnailPath) . " -y 2>/dev/null";
        @shell_exec($thumbCmd);

        // 2. Generate HLS Segments & Playlist (6-second chunks for fast start)
        // Try ultra-fast stream copy first (takes 2-4s instead of 4 minutes of CPU encoding)
        $hlsFastCmd = "{$ffmpeg} -i " . escapeshellarg($sourceMp4Path) . " -c copy -hls_time 6 -hls_list_size 0 -hls_segment_filename " . escapeshellarg($segmentPattern) . " " . escapeshellarg($playlistPath) . " -y 2>/dev/null";
        @shell_exec($hlsFastCmd);

        // Fallback to transcoding only if stream copy failed to produce playlist
        if (!file_exists($playlistPath)) {
            $hlsCmd = "{$ffmpeg} -i " . escapeshellarg($sourceMp4Path) . " -codec:v libx264 -crf 23 -preset veryfast -codec:a aac -b:a 128k -hls_time 6 -hls_list_size 0 -hls_segment_filename " . escapeshellarg($segmentPattern) . " " . escapeshellarg($playlistPath) . " -y 2>/dev/null";
            @shell_exec($hlsCmd);
        }

        $hlsUrl = '/api/videos/hls/' . $videoUuid . '/index.m3u8';
        $thumbUrl = '/api/videos/hls/' . $videoUuid . '/thumbnail.jpg';

        return [
            'hls_url'          => file_exists($playlistPath) ? $hlsUrl : null,
            'thumbnail_url'    => file_exists($thumbnailPath) ? $thumbUrl : null,
            'duration_seconds' => $durationSeconds
        ];
    }

    /**
     * Stream HLS Playlist (.m3u8), Video Segment (.ts), or Thumbnail (.jpg)
     */
    public static function streamHlsFile(string $videoUuid, string $filename): void
    {
        self::ensureSchema();

        $lesson = Database::selectOne("SELECT * FROM lessons WHERE video_uuid = ? LIMIT 1", [$videoUuid]);
        if (!$lesson) {
            http_response_code(404);
            header('Content-Type: application/json; charset=utf-8');
            echo json_encode(['status' => 'error', 'message' => 'ملف البث غير موجود']);
            exit;
        }

        $courseId = (int)$lesson['course_id'];
        $cleanFilename = basename($filename);
        $filePath = dirname(__DIR__, 2) . "/storage/hls/{$courseId}/{$videoUuid}/{$cleanFilename}";

        if (!file_exists($filePath)) {
            http_response_code(404);
            header('Content-Type: application/json; charset=utf-8');
            echo json_encode(['status' => 'error', 'message' => 'المقطع المطلوب مفقود']);
            exit;
        }

        $ext = strtolower(pathinfo($cleanFilename, PATHINFO_EXTENSION));
        $mime = match ($ext) {
            'm3u8'  => 'application/vnd.apple.mpegurl',
            'ts'    => 'video/MP2T',
            'jpg', 'jpeg' => 'image/jpeg',
            'key'   => 'application/octet-stream',
            default => 'application/octet-stream'
        };

        if (ob_get_length()) {
            ob_clean();
        }

        header('Content-Type: ' . $mime);
        header('Cache-Control: public, max-age=86400');
        header('Access-Control-Allow-Origin: *');
        header('Content-Length: ' . filesize($filePath));
        readfile($filePath);
        exit;
    }

    /**
     * Stream Local Video file supporting HTTP 206 Partial Content (Range requests)
     */
    public static function streamLocalVideo(string $videoUuid): void
    {
        self::ensureSchema();

        $lesson = Database::selectOne("SELECT * FROM lessons WHERE video_uuid = ? LIMIT 1", [$videoUuid]);
        if (!$lesson || empty($lesson['local_path'])) {
            http_response_code(404);
            header('Content-Type: application/json; charset=utf-8');
            echo json_encode(['status' => 'error', 'message' => 'ملف الفيديو غير موجود']);
            exit;
        }

        $fullPath = dirname(__DIR__, 2) . '/' . ltrim($lesson['local_path'], '/');
        if (!file_exists($fullPath)) {
            http_response_code(404);
            header('Content-Type: application/json; charset=utf-8');
            echo json_encode(['status' => 'error', 'message' => 'الملف المحفوظ مفقود على القرص']);
            exit;
        }

        $fileSize = filesize($fullPath);
        $fp = @fopen($fullPath, 'rb');
        if (!$fp) {
            http_response_code(500);
            echo json_encode(['status' => 'error', 'message' => 'تعذر فتح ملف الفيديو']);
            exit;
        }

        $mime = 'video/mp4';
        $ext = strtolower(pathinfo($fullPath, PATHINFO_EXTENSION));
        if ($ext === 'webm') $mime = 'video/webm';
        if ($ext === 'mov') $mime = 'video/quicktime';
        if ($ext === 'mkv') $mime = 'video/x-matroska';

        $start = 0;
        $end = $fileSize - 1;

        if (ob_get_length()) {
            ob_clean();
        }

        header('Content-Type: ' . $mime);
        header('Accept-Ranges: bytes');
        header('Cache-Control: public, max-age=3600');
        header('X-Content-Type-Options: nosniff');
        header('Access-Control-Allow-Origin: *');

        if (isset($_SERVER['HTTP_RANGE'])) {
            $range = $_SERVER['HTTP_RANGE'];
            if (preg_match('/bytes=\h*(\d+)-(\d*)[\D.*]?/i', $range, $matches)) {
                $start = (int)$matches[1];
                if (!empty($matches[2])) {
                    $end = (int)$matches[2];
                }
            }

            if ($start > $end || $start >= $fileSize) {
                http_response_code(416);
                header("Content-Range: bytes */{$fileSize}");
                fclose($fp);
                exit;
            }

            http_response_code(206);
            header("Content-Range: bytes {$start}-{$end}/{$fileSize}");
            $length = ($end - $start) + 1;
            header("Content-Length: {$length}");
        } else {
            http_response_code(200);
            header("Content-Length: {$fileSize}");
        }

        fseek($fp, $start);
        $bufferSize = 1024 * 128; // 128KB chunk stream
        while (!feof($fp) && ($pos = ftell($fp)) <= $end) {
            if ($pos + $bufferSize > $end) {
                $bufferSize = $end - $pos + 1;
            }
            if ($bufferSize <= 0) break;
            echo fread($fp, $bufferSize);
            flush();
        }

        fclose($fp);
        exit;
    }

    // =========================================================================
    // METHOD 2: Bunny.net Stream Cloud Video CDN & Token DRM
    // =========================================================================

    private static function getBunnyConfig(): array
    {
        return [
            'library_id'     => getenv('BUNNY_STREAM_LIBRARY_ID') ?: '',
            'api_key'        => getenv('BUNNY_STREAM_API_KEY') ?: '',
            'token_key'      => getenv('BUNNY_STREAM_TOKEN_KEY') ?: getenv('JWT_SECRET') ?: '',
            'pull_zone_host' => getenv('BUNNY_STREAM_HOST') ?: '',
            'embed_host'     => 'iframe.mediadelivery.net'
        ];
    }

    public static function createBunnyVideo(string $title, ?string $collectionId = null): array
    {
        $config = self::getBunnyConfig();
        if (empty($config['api_key'])) {
            throw new \RuntimeException('Bunny Stream غير مهيأ: أضف مفاتيح الوصول قبل إنشاء فيديو سحابي.');
            /*
            $mockGuid = sprintf('%04x%04x-%04x-%04x-%04x-%04x%04x%04x',
                mt_rand(0, 0xffff), mt_rand(0, 0xffff),
                mt_rand(0, 0xffff),
                mt_rand(0, 0x0fff) | 0x4000,
                mt_rand(0, 0x3fff) | 0x8000,
                mt_rand(0, 0xffff), mt_rand(0, 0xffff), mt_rand(0, 0xffff)
            );
            return [
                'video_id'     => $mockGuid,
                'library_id'   => $config['library_id'],
                'title'        => $title,
                'status'       => 'created',
                'is_mock'      => true,
                'direct_embed' => "https://{$config['embed_host']}/embed/{$config['library_id']}/{$mockGuid}",
                'hls_playlist' => "https://{$config['pull_zone_host']}/{$mockGuid}/playlist.m3u8"
            ];
            */
        }

        $url = "https://video.bunnycdn.com/library/{$config['library_id']}/videos";
        $data = ['title' => $title];
        if ($collectionId) {
            $data['collectionId'] = $collectionId;
        }

        $ch = curl_init($url);
        curl_setopt_array($ch, [
            CURLOPT_POST           => true,
            CURLOPT_POSTFIELDS     => json_encode($data),
            CURLOPT_HTTPHEADER     => [
                'AccessKey: ' . $config['api_key'],
                'Content-Type: application/json',
                'Accept: application/json'
            ],
            CURLOPT_RETURNTRANSFER => true,
            CURLOPT_TIMEOUT        => 15
        ]);

        $response = curl_exec($ch);
        $httpCode = curl_getinfo($ch, CURLINFO_HTTP_CODE);
        curl_close($ch);

        $json = json_decode($response, true);
        if ($httpCode >= 200 && $httpCode < 300 && !empty($json['guid'])) {
            $guid = $json['guid'];
            return [
                'video_id'     => $guid,
                'library_id'   => $config['library_id'],
                'title'        => $json['title'] ?? $title,
                'status'       => 'created',
                'direct_embed' => "https://{$config['embed_host']}/embed/{$config['library_id']}/{$guid}",
                'hls_playlist' => "https://{$config['pull_zone_host']}/{$guid}/playlist.m3u8"
            ];
        }

        throw new \RuntimeException("Bunny Stream API Error ({$httpCode}): " . ($json['message'] ?? $response));
    }

    public static function uploadBunnyVideo(string $videoId, string $filePath): bool
    {
        $config = self::getBunnyConfig();
        if (empty($config['api_key']) || !file_exists($filePath)) {
            return false;
        }

        $url = "https://video.bunnycdn.com/library/{$config['library_id']}/videos/{$videoId}";
        $fp = fopen($filePath, 'r');
        $fileSize = filesize($filePath);

        $ch = curl_init($url);
        curl_setopt_array($ch, [
            CURLOPT_PUT            => true,
            CURLOPT_INFILE         => $fp,
            CURLOPT_INFILESIZE     => $fileSize,
            CURLOPT_HTTPHEADER     => [
                'AccessKey: ' . $config['api_key'],
                'Content-Type: application/octet-stream'
            ],
            CURLOPT_RETURNTRANSFER => true,
            CURLOPT_TIMEOUT        => 600
        ]);

        $response = curl_exec($ch);
        $httpCode = curl_getinfo($ch, CURLINFO_HTTP_CODE);
        fclose($fp);
        curl_close($ch);

        return ($httpCode >= 200 && $httpCode < 300);
    }

    public static function generateBunnySignedPlayback(string $videoId, int $expiresInSeconds = 7200): array
    {
        $config = self::getBunnyConfig();
        $libraryId = $config['library_id'];
        $tokenKey  = $config['token_key'];
        $expires   = time() + $expiresInSeconds;

        $hashable = $tokenKey . $videoId . $expires;
        $token = hash('sha256', $hashable);

        $embedUrl = "https://{$config['embed_host']}/embed/{$libraryId}/{$videoId}?token={$token}&expires={$expires}";
        $hlsUrl   = "https://{$config['pull_zone_host']}/{$videoId}/playlist.m3u8?token={$token}&expires={$expires}";
        $thumbUrl = "https://{$config['pull_zone_host']}/{$videoId}/thumbnail.jpg?token={$token}&expires={$expires}";

        return [
            'video_id'    => $videoId,
            'library_id'  => $libraryId,
            'embed_url'   => $embedUrl,
            'hls_url'     => $hlsUrl,
            'thumb_url'   => $thumbUrl,
            'token'       => $token,
            'expires_at'  => $expires
        ];
    }

    // ==========================================
    // Cloudflare R2 Object Storage & CDN Engine
    // ==========================================
    public static function getR2Config(): array
    {
        return [
            'account_id' => getenv('CLOUDFLARE_R2_ACCOUNT_ID') ?: '',
            'access_key' => getenv('CLOUDFLARE_R2_ACCESS_KEY') ?: '',
            'secret_key' => getenv('CLOUDFLARE_R2_SECRET_KEY') ?: '',
            'endpoint'   => getenv('CLOUDFLARE_R2_ENDPOINT')   ?: '',
            'bucket'     => getenv('CLOUDFLARE_R2_BUCKET')     ?: '',
            'public_url' => getenv('CLOUDFLARE_R2_PUBLIC_URL') ?: ''
        ];
    }

    /**
     * Upload any file (video, segment, pdf, thumbnail) to Cloudflare R2 with AWS SigV4
     */
    public static function uploadToR2(string $localFilePath, string $r2Key, string $contentType = 'application/octet-stream'): ?string
    {
        if (!file_exists($localFilePath)) {
            return null;
        }

        $config = self::getR2Config();
        $bucket = $config['bucket'];
        $host = "{$bucket}.{$config['account_id']}.r2.cloudflarestorage.com";
        $endpoint = "https://{$host}/" . ltrim($r2Key, '/');

        $payload = file_get_contents($localFilePath);
        $payloadHash = hash('sha256', $payload);

        $date = gmdate('Ymd\THis\Z');
        $shortDate = gmdate('Ymd');
        $region = 'auto';
        $service = 's3';

        // AWS SigV4 Canonical Headers
        $canonicalHeaders = "host:{$host}\nx-amz-content-sha256:{$payloadHash}\nx-amz-date:{$date}\n";
        $signedHeaders = 'host;x-amz-content-sha256;x-amz-date';

        $canonicalRequest = "PUT\n/" . ltrim($r2Key, '/') . "\n\n{$canonicalHeaders}\n{$signedHeaders}\n{$payloadHash}";
        $stringToSign = "AWS4-HMAC-SHA256\n{$date}\n{$shortDate}/{$region}/{$service}/aws4_request\n" . hash('sha256', $canonicalRequest);

        // Calculate Signing Key
        $kSecret = 'AWS4' . $config['secret_key'];
        $kDate = hash_hmac('sha256', $shortDate, $kSecret, true);
        $kRegion = hash_hmac('sha256', $region, $kDate, true);
        $kService = hash_hmac('sha256', $service, $kRegion, true);
        $kSigning = hash_hmac('sha256', 'aws4_request', $kService, true);
        $signature = hash_hmac('sha256', $stringToSign, $kSigning);

        $authHeader = "AWS4-HMAC-SHA256 Credential={$config['access_key']}/{$shortDate}/{$region}/{$service}/aws4_request, SignedHeaders={$signedHeaders}, Signature={$signature}";

        $ch = curl_init($endpoint);
        curl_setopt_array($ch, [
            CURLOPT_CUSTOMREQUEST  => 'PUT',
            CURLOPT_POSTFIELDS     => $payload,
            CURLOPT_HTTPHEADER     => [
                "Host: {$host}",
                "x-amz-date: {$date}",
                "x-amz-content-sha256: {$payloadHash}",
                "Authorization: {$authHeader}",
                "Content-Type: {$contentType}",
                "Content-Length: " . strlen($payload)
            ],
            CURLOPT_RETURNTRANSFER => true,
            CURLOPT_TIMEOUT        => 300
        ]);

        $response = curl_exec($ch);
        $httpCode = curl_getinfo($ch, CURLINFO_HTTP_CODE);
        curl_close($ch);

        if ($httpCode >= 200 && $httpCode < 300 && !empty($config['public_url'])) {
            return rtrim($config['public_url'], '/') . '/' . ltrim($r2Key, '/');
        }

        return null;
    }

    /** Upload a complete HLS directory and return the public playlist URL. */
    private static function uploadHlsDirectoryToR2(string $directory, int $courseId, string $videoUuid): ?string
    {
        if (!is_dir($directory)) return null;

        $playlistUrl = null;
        foreach (glob($directory . '/*') ?: [] as $filePath) {
            if (!is_file($filePath)) continue;
            $extension = strtolower(pathinfo($filePath, PATHINFO_EXTENSION));
            $contentType = match ($extension) {
                'm3u8' => 'application/vnd.apple.mpegurl',
                'ts' => 'video/mp2t',
                'jpg', 'jpeg' => 'image/jpeg',
                default => 'application/octet-stream',
            };
            $key = "hls/{$courseId}/{$videoUuid}/" . basename($filePath);
            $url = self::uploadToR2($filePath, $key, $contentType);
            if ($extension === 'm3u8' && $url) $playlistUrl = $url;
        }

        return $playlistUrl;
    }
}