<?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. 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");
            }

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

            $colsHls = Database::select("SHOW COLUMNS FROM lessons LIKE 'hls_url'");
            if (empty($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");
            }

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

    // =========================================================================
    // 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): 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;

        if (!move_uploaded_file($file['tmp_name'], $targetPath)) {
            throw new \RuntimeException('فشل حفظ ملف الفيديو على السيرفر، يرجى فحص أذونات المجلد.');
        }

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

        return [
            'video_uuid'      => $videoUuid,
            'local_path'      => $relativePath,
            'file_size'       => $fileSize,
            'mime_type'       => $mime,
            'extension'       => $ext,
            'storage_type'    => 'api_upload',
            'encoding_status' => 'ready',
            'stream_url'      => '/api/videos/stream/' . $videoUuid
        ];
    }

    /**
     * Stream Local Video file supporting HTTP 206 Partial Content (Range requests)
     * Allows seamless scrubbing/seeking in browser without loading full video
     */
    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;

        // Clean previous buffers
        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');

        // Check if Range header is requested by video player
        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
    // =========================================================================

    /**
     * Get Bunny Stream API Credentials from Environment
     */
    private static function getBunnyConfig(): array
    {
        return [
            'library_id'     => getenv('BUNNY_STREAM_LIBRARY_ID') ?: '285491',
            'api_key'        => getenv('BUNNY_STREAM_API_KEY') ?: '',
            'token_key'      => getenv('BUNNY_STREAM_TOKEN_KEY') ?: getenv('JWT_SECRET') ?: 'SaqelSecureBunnyToken2026',
            'pull_zone_host' => getenv('BUNNY_STREAM_HOST') ?: 'vz-saqel.b-cdn.net',
            'embed_host'     => 'iframe.mediadelivery.net'
        ];
    }

    /**
     * Create a new Video placeholder in Bunny Stream Library
     * POST https://video.bunnycdn.com/library/{libraryId}/videos
     */
    public static function createBunnyVideo(string $title, ?string $collectionId = null): array
    {
        $config = self::getBunnyConfig();
        if (empty($config['api_key'])) {
            // Mock response if API key is not yet set in production .env
            $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));
    }

    /**
     * Upload binary video to an existing Bunny Video ID
     * PUT https://video.bunnycdn.com/library/{libraryId}/videos/{videoId}
     */
    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 // 10 minutes for large videos
        ]);

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

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

    /**
     * Generate Signed DRM Playback URL using Bunny Token Authentication (SHA256 HMAC)
     * Protects video from hotlinking, unauthorized sharing, and downloading
     * 
     * @param string $videoId Bunny Video GUID
     * @param int $expiresInSeconds Token validity window (default: 2 hours)
     * @return array
     */
    public static function generateBunnySignedPlayback(string $videoId, int $expiresInSeconds = 7200): array
    {
        $config = self::getBunnyConfig();
        $libraryId = $config['library_id'];
        $tokenKey  = $config['token_key'];
        $expires   = time() + $expiresInSeconds;

        // Bunny Stream Token Hash Formula:
        // token = SHA256(securityToken + videoId + expirationTime)
        $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
        ];
    }
}