import 'dart:convert';
import 'dart:io';
import 'dart:typed_data';
import 'package:crypto/crypto.dart';
import 'package:dio/dio.dart';
import 'package:path/path.dart' as path;
import 'package:path_provider/path_provider.dart';
import '../../core/logger.dart';
import '../../core/exceptions/blossom_exception.dart';
import '../local/local_storage_service.dart';
import '../media/media_service_interface.dart';
import '../nostr/models/nostr_event.dart';
import '../nostr/models/nostr_keypair.dart';
import 'models/blossom_upload_response.dart';

/// Service for interacting with Blossom Media Server API.
///
/// Blossom uses Nostr authentication (kind 24242 authorization events).
/// See: https://github.com/hzrd149/blossom
class BlossomService implements MediaServiceInterface {
  /// HTTP client for API requests.
  final Dio _dio;

  /// Blossom API base URL.
  final String _baseUrl;

  /// Nostr keypair for authentication.
  NostrKeyPair? _nostrKeyPair;

  /// Cache directory for storing fetched images.
  Directory? _imageCacheDirectory;

  /// Creates a [BlossomService] instance.
  ///
  /// [baseUrl] - Blossom server base URL (e.g., 'https://blossom.example.com').
  /// [localStorage] - Local storage service for caching metadata.
  /// [dio] - Optional Dio instance for dependency injection (useful for testing).
  BlossomService({
    required String baseUrl,
    required LocalStorageService localStorage,
    Dio? dio,
  })  : _baseUrl = baseUrl,
        _dio = dio ?? Dio() {
    _dio.options.baseUrl = baseUrl;
  }

  /// Sets the Nostr keypair for authentication.
  void setNostrKeyPair(NostrKeyPair keypair) {
    _nostrKeyPair = keypair;
    Logger.info('BlossomService: Nostr keypair set (pubkey: ${keypair.publicKey.substring(0, 16)}...)');
  }

  /// Creates an authorization event (kind 24242) for Blossom authentication.
  /// 
  /// [blobHash] - The SHA256 hash of the blob being uploaded.
  /// [filename] - The filename of the file being uploaded (optional).
  /// [expirationSeconds] - Expiration time in seconds from now (default: 300 = 5 minutes).
  NostrEvent _createAuthorizationEvent(String blobHash, {String? filename, int expirationSeconds = 300}) {
    if (_nostrKeyPair == null) {
      Logger.error('Cannot create Blossom authorization event: Nostr keypair not set');
      throw BlossomException('Nostr keypair not set. Call setNostrKeyPair() first.');
    }

    Logger.debug('Creating Blossom authorization event with pubkey: ${_nostrKeyPair!.publicKey.substring(0, 16)}...');
    Logger.debug('Blossom authorization blob hash: $blobHash');

    final createdAt = DateTime.now().millisecondsSinceEpoch ~/ 1000;
    final expiration = createdAt + expirationSeconds;

    // Create authorization event (kind 24242) with required tags per Blossom spec
    // Based on iris.to implementation, Blossom expects:
    // - content: filename (or empty string)
    // - tags: ["t", "upload"], ["x", blobHash], ["expiration", timestamp]
    final event = NostrEvent.create(
      content: filename ?? '', // Filename or empty string
      kind: 24242,
      privateKey: _nostrKeyPair!.privateKey,
      tags: [
        ['t', 'upload'], // Type tag
        ['x', blobHash], // Blob hash tag
        ['expiration', expiration.toString()], // Expiration timestamp
      ],
    );
    
    // Verify the signature before using it
    final isValid = event.verifySignature();
    if (!isValid) {
      Logger.error('Blossom authorization event signature verification FAILED!');
      throw BlossomException('Failed to create valid authorization event: signature verification failed');
    }
    
    Logger.debug('Blossom authorization event created: id=${event.id.substring(0, 16)}..., kind=${event.kind}, sig=${event.sig.substring(0, 16)}...');
    Logger.debug('Blossom authorization event signature verified: $isValid');
    Logger.debug('Blossom authorization event tags: ${event.tags}');
    
    return event;
  }

  /// Gets the Content-Type header value based on file extension.
  String _getContentType(String filename) {
    final extension = filename.split('.').last.toLowerCase();
    switch (extension) {
      case 'jpg':
      case 'jpeg':
        return 'image/jpeg';
      case 'png':
        return 'image/png';
      case 'webp':
        return 'image/webp';
      case 'gif':
        return 'image/gif';
      default:
        return 'image/jpeg'; // Default fallback
    }
  }

  /// Uploads an image file to Blossom.
  ///
  /// [imageFile] - The image file to upload.
  ///
  /// Returns [BlossomUploadResponse] containing the blob hash and URL.
  ///
  /// Throws [BlossomException] if upload fails.
  Future<BlossomUploadResponse> uploadImageToBlossom(File imageFile) async {
    if (_nostrKeyPair == null) {
      Logger.error('Blossom upload failed: Nostr keypair not set');
      throw BlossomException('Nostr keypair not set. Call setNostrKeyPair() first.');
    }
    
    Logger.debug('Blossom upload: Nostr keypair is set (pubkey: ${_nostrKeyPair!.publicKey.substring(0, 16)}...)');

    try {
      if (!await imageFile.exists()) {
        throw BlossomException('Image file does not exist: ${imageFile.path}');
      }

      // Read file bytes and calculate SHA256 hash
      final fileBytes = await imageFile.readAsBytes();
      final hash = sha256.convert(fileBytes);
      final blobHash = hash.toString();
      
      // Get filename for the authorization event
      final filename = imageFile.path.split('/').last;
      
      // Determine content type based on file extension
      final contentType = _getContentType(filename);

      // Create authorization event with blob hash and filename
      final authEvent = _createAuthorizationEvent(blobHash, filename: filename);
      
      // Log authorization event for debugging
      Logger.debug('Blossom authorization event: ${authEvent.toJson()}');
      Logger.debug('Blossom authorization event ID: ${authEvent.id}');
      Logger.debug('Blossom authorization event pubkey: ${authEvent.pubkey}');
      Logger.debug('Blossom authorization event kind: ${authEvent.kind}');
      Logger.debug('Blossom authorization event sig: ${authEvent.sig.substring(0, 16)}...');

      // Encode authorization event as JSON object (not array) with snake_case field names
      // Based on iris.to implementation, Blossom expects:
      // - JSON object format: {"created_at": ..., "content": ..., "tags": ..., "kind": ..., "pubkey": ..., "id": ..., "sig": ...}
      // - Authorization header: "Nostr " + base64-encoded JSON object
      final authEventJson = {
        'created_at': authEvent.createdAt,
        'content': authEvent.content,
        'tags': authEvent.tags,
        'kind': authEvent.kind,
        'pubkey': authEvent.pubkey,
        'id': authEvent.id,
        'sig': authEvent.sig,
      };
      final authJsonString = jsonEncode(authEventJson);
      final authBase64 = base64Encode(utf8.encode(authJsonString));
      
      Logger.debug('Blossom Authorization header (JSON object): $authJsonString');
      Logger.debug('Blossom Authorization header (Base64): $authBase64');
      
      // Try different authorization header formats in order
      // Based on iris.to, Blossom expects "Nostr " + base64-encoded JSON object
      final formats = [
        ('Nostr Base64', 'Nostr $authBase64'), // Try this first (matches iris.to)
        ('Raw JSON', authJsonString),
        ('Base64', authBase64),
      ];
      
      DioException? lastException;
      for (final (formatName, authHeader) in formats) {
        Logger.debug('Blossom trying authorization format: $formatName');
        try {
          // Send raw file bytes (not multipart form data) as per iris.to implementation
          // iris.to sends: PUT /upload with Content-Type: image/jpeg and raw binary data
          final response = await _dio.put(
            '/upload',
            data: fileBytes, // Raw binary data
            options: Options(
              headers: {
                'Authorization': authHeader,
                'Content-Type': contentType, // e.g., 'image/jpeg', 'image/png', 'image/webp'
              },
            ),
          );
          
          // Success!
          Logger.info('Blossom upload succeeded with format: $formatName');
          
          if (response.statusCode != 200 && response.statusCode != 201) {
            throw BlossomException(
              'Upload failed: ${response.statusMessage}',
              response.statusCode,
            );
          }

          // Parse response (blob descriptor per BUD-02)
          final responseData = response.data as Map<String, dynamic>;
          final uploadResponse = BlossomUploadResponse.fromJson(responseData);
          
          Logger.info('Image uploaded to Blossom: ${uploadResponse.hash}');
          return uploadResponse;
        } on DioException catch (e) {
          lastException = e;
          if (e.response?.statusCode == 401) {
            Logger.debug('Blossom format "$formatName" failed with 401, trying next format...');
            continue; // Try next format
          } else {
            // Non-401 error - log it but continue trying other formats
            // This could be a network error, parsing error, etc.
            Logger.warning('Blossom format "$formatName" failed with non-401 error: ${e.message} (status: ${e.response?.statusCode}), trying next format...');
            continue; // Try next format anyway
          }
        } catch (e) {
          // Non-DioException - this is unexpected, log and continue
          Logger.warning('Blossom format "$formatName" failed with unexpected error: $e, trying next format...');
          continue;
        }
      }
      
      // All formats failed with 401
      if (lastException != null) {
        Logger.error('Blossom upload DioException: ${lastException.message}');
        Logger.error('Blossom upload status code: ${lastException.response?.statusCode}');
        Logger.error('Blossom upload response data: ${lastException.response?.data}');
        Logger.error('Blossom 401 Unauthorized - All authorization formats failed');
        Logger.error('Blossom keypair status: ${_nostrKeyPair != null ? "SET" : "NOT SET"}');
        if (_nostrKeyPair != null) {
          Logger.error('Blossom keypair pubkey: ${_nostrKeyPair!.publicKey}');
        }
        Logger.error('Tried formats: Raw JSON, Base64, Nostr Base64');
        Logger.error('Possible causes:');
        Logger.error('1. Server-side authentication configuration issue');
        Logger.error('2. Blob hash mismatch or incorrect format');
        Logger.error('3. Expiration timestamp issue');
        Logger.error('4. Server expects different event structure');
        throw BlossomException(
          'Upload failed: ${lastException.message ?? 'Unknown error'}',
          lastException.response?.statusCode,
        );
      }
      throw BlossomException('Upload failed: All authorization formats failed');
    } on DioException catch (e) {
      Logger.error('Blossom upload DioException: ${e.message}');
      Logger.error('Blossom upload status code: ${e.response?.statusCode}');
      Logger.error('Blossom upload response data: ${e.response?.data}');
      throw BlossomException(
        'Upload failed: ${e.message ?? 'Unknown error'}',
        e.response?.statusCode,
      );
    } catch (e) {
      Logger.error('Blossom upload exception: $e');
      throw BlossomException('Upload failed: $e');
    }
  }

  /// Uploads an image file (implements MediaServiceInterface).
  @override
  Future<Map<String, dynamic>> uploadImage(File imageFile) async {
    final response = await uploadImageToBlossom(imageFile);
    return {
      'hash': response.hash,
      'id': response.hash, // For compatibility
      'url': response.url,
    };
  }

  /// Uploads a video file (implements MediaServiceInterface).
  @override
  Future<Map<String, dynamic>> uploadVideo(File videoFile) async {
    if (_nostrKeyPair == null) {
      Logger.error('Blossom upload failed: Nostr keypair not set');
      throw BlossomException('Nostr keypair not set. Call setNostrKeyPair() first.');
    }
    
    Logger.debug('Blossom video upload: Nostr keypair is set (pubkey: ${_nostrKeyPair!.publicKey.substring(0, 16)}...)');

    try {
      if (!await videoFile.exists()) {
        throw BlossomException('Video file does not exist: ${videoFile.path}');
      }

      // Read file bytes and calculate SHA256 hash
      final fileBytes = await videoFile.readAsBytes();
      final hash = sha256.convert(fileBytes);
      final blobHash = hash.toString();
      
      // Get filename for the authorization event
      final filename = videoFile.path.split('/').last;
      
      // Determine content type for video (MP4)
      final contentType = 'video/mp4';

      // Create authorization event with blob hash and filename
      final authEvent = _createAuthorizationEvent(blobHash, filename: filename);
      
      // Encode authorization event as JSON object
      final authEventJson = {
        'created_at': authEvent.createdAt,
        'content': authEvent.content,
        'tags': authEvent.tags,
        'kind': authEvent.kind,
        'pubkey': authEvent.pubkey,
        'id': authEvent.id,
        'sig': authEvent.sig,
      };
      final authJsonString = jsonEncode(authEventJson);
      final authBase64 = base64Encode(utf8.encode(authJsonString));
      
      // Try different authorization header formats
      final formats = [
        ('Nostr Base64', 'Nostr $authBase64'),
        ('Raw JSON', authJsonString),
        ('Base64', authBase64),
      ];
      
      DioException? lastException;
      for (final (formatName, authHeader) in formats) {
        try {
          final response = await _dio.put(
            '/upload',
            data: fileBytes,
            options: Options(
              headers: {
                'Authorization': authHeader,
                'Content-Type': contentType,
              },
            ),
          );
          
          if (response.statusCode != 200 && response.statusCode != 201) {
            throw BlossomException(
              'Upload failed: ${response.statusMessage}',
              response.statusCode,
            );
          }

          final responseData = response.data as Map<String, dynamic>;
          final uploadResponse = BlossomUploadResponse.fromJson(responseData);
          
          Logger.info('Video uploaded to Blossom: ${uploadResponse.hash}');
          return {
            'hash': uploadResponse.hash,
            'id': uploadResponse.hash,
            'url': uploadResponse.url,
          };
        } on DioException catch (e) {
          lastException = e;
          if (e.response?.statusCode == 401) {
            Logger.debug('Blossom format "$formatName" failed with 401, trying next format...');
            continue;
          }
          // Non-401 error, rethrow
          rethrow;
        }
      }
      
      if (lastException != null) {
        throw BlossomException(
          'Video upload failed: ${lastException.message ?? 'Unknown error'}',
          lastException.response?.statusCode,
        );
      }
      throw BlossomException('Video upload failed: All authorization formats failed');
    } on DioException catch (e) {
      Logger.error('Blossom video upload DioException: ${e.message}');
      throw BlossomException(
        'Video upload failed: ${e.message ?? 'Unknown error'}',
        e.response?.statusCode,
      );
    } catch (e) {
      Logger.error('Blossom video upload error: $e');
      throw BlossomException('Video upload failed: $e');
    }
  }

  /// Fetches image bytes for a blob by hash with local caching.
  ///
  /// [blobHash] - The SHA256 hash of the blob (or full URL).
  /// [isThumbnail] - Whether to fetch thumbnail (true) or original image (false). Default: true.
  ///
  /// Returns the image bytes as Uint8List.
  ///
  /// Throws [BlossomException] if fetch fails.
  Future<Uint8List> fetchImageBytes(String blobHash, {bool isThumbnail = true}) async {
    await _ensureImageCacheDirectory();

    // Check cache first
    final cacheFilePath = _getCacheFilePath(blobHash, isThumbnail);
    if (cacheFilePath.isNotEmpty) {
      final cacheFile = File(cacheFilePath);
      if (await cacheFile.exists()) {
        try {
          final cachedBytes = await cacheFile.readAsBytes();
          Logger.debug('Loaded image from cache: $blobHash');
          return Uint8List.fromList(cachedBytes);
        } catch (e) {
          Logger.warning('Failed to read cached image, fetching fresh: $e');
        }
      }
    }

    // Cache miss - fetch from Blossom
    try {
      // If blobHash is a full URL, use it directly
      String imageUrl;
      if (blobHash.startsWith('http://') || blobHash.startsWith('https://')) {
        imageUrl = blobHash;
      } else {
        // Construct URL: GET /<sha256> per BUD-01
        imageUrl = '$_baseUrl/$blobHash';
      }

      final response = await _dio.get<List<int>>(
        imageUrl,
        options: Options(
          responseType: ResponseType.bytes,
        ),
      );

      if (response.statusCode != 200) {
        throw BlossomException(
          'Failed to fetch image: ${response.statusMessage}',
          response.statusCode,
        );
      }

      final imageBytes = Uint8List.fromList(response.data ?? []);

      // Cache the fetched image
      if (cacheFilePath.isNotEmpty && imageBytes.isNotEmpty) {
        try {
          // Ensure cache directory exists before writing
          await _ensureImageCacheDirectory();
          final cacheFile = File(cacheFilePath);
          await cacheFile.writeAsBytes(imageBytes);
          Logger.debug('Cached image: $blobHash');
        } catch (e) {
          Logger.warning('Failed to cache image (non-fatal): $e');
        }
      }

      return imageBytes;
    } on DioException catch (e) {
      throw BlossomException(
        'Failed to fetch image: ${e.message ?? 'Unknown error'}',
        e.response?.statusCode,
      );
    }
  }

  /// Gets the full image URL for a blob hash.
  ///
  /// [blobHash] - The SHA256 hash of the blob (or full URL).
  ///
  /// Returns the full URL to the blob.
  String getImageUrl(String blobHash) {
    // If it's already a full URL, return it
    if (blobHash.startsWith('http://') || blobHash.startsWith('https://')) {
      return blobHash;
    }
    // GET /<sha256> per BUD-01
    return '$_baseUrl/$blobHash';
  }

  /// Gets the base URL for Blossom API.
  String get baseUrl => _baseUrl;

  /// Initializes the image cache directory.
  Future<void> _ensureImageCacheDirectory() async {
    if (_imageCacheDirectory != null) return;

    try {
      final appDir = await getApplicationDocumentsDirectory();
      _imageCacheDirectory = Directory(path.join(appDir.path, 'blossom_image_cache'));
      
      if (!await _imageCacheDirectory!.exists()) {
        await _imageCacheDirectory!.create(recursive: true);
      }
    } catch (e) {
      Logger.warning('Failed to initialize image cache directory: $e');
    }
  }

  /// Gets the cache file path for an image.
  /// 
  /// Extracts the blob hash from URLs if needed and sanitizes it for use as a filename.
  String _getCacheFilePath(String blobHashOrUrl, bool isThumbnail) {
    if (_imageCacheDirectory == null) return '';
    
    // Extract blob hash from URL if it's a full URL
    String blobHash = blobHashOrUrl;
    if (blobHashOrUrl.startsWith('http://') || blobHashOrUrl.startsWith('https://')) {
      // Extract hash from URL like: https://media.based21.com/08e301596aef7a232dcec85c4725f49ff88864f26a3c572f1fa6d1aedaecaf7e.webp
      final uri = Uri.parse(blobHashOrUrl);
      final pathSegments = uri.pathSegments;
      if (pathSegments.isNotEmpty) {
        // Get the last segment (the hash with extension)
        final lastSegment = pathSegments.last;
        // Remove extension if present (e.g., .webp)
        blobHash = lastSegment.split('.').first;
      } else {
        // Fallback: use a sanitized version of the URL
        blobHash = blobHashOrUrl
            .replaceAll(RegExp(r'[^a-zA-Z0-9]'), '_')
            .substring(0, blobHashOrUrl.length > 64 ? 64 : blobHashOrUrl.length);
      }
    }
    
    // Sanitize blob hash to ensure it's safe for use as a filename
    // Blob hashes are hex strings (64 chars), so they should be safe, but let's be defensive
    final sanitizedHash = blobHash.replaceAll(RegExp(r'[^a-zA-Z0-9]'), '_');
    final cacheKey = '${sanitizedHash}_${isThumbnail ? 'thumb' : 'full'}';
    return path.join(_imageCacheDirectory!.path, cacheKey);
  }

  /// Clears the cache for a specific image URL or blob hash.
  @override
  Future<void> clearImageCache(String imageUrlOrBlobHash) async {
    // Extract blob hash from URL if it's a full URL
    String blobHash = imageUrlOrBlobHash;
    if (imageUrlOrBlobHash.startsWith('http://') || imageUrlOrBlobHash.startsWith('https://')) {
      // Extract hash from URL like: https://media.based21.com/08e301596aef7a232dcec85c4725f49ff88864f26a3c572f1fa6d1aedaecaf7e.webp
      final uri = Uri.parse(imageUrlOrBlobHash);
      final pathSegments = uri.pathSegments;
      if (pathSegments.isNotEmpty) {
        // Get the last segment (the hash with extension)
        final lastSegment = pathSegments.last;
        // Remove extension if present
        blobHash = lastSegment.split('.').first;
      }
    }

    // Clear both thumbnail and full image cache
    final thumbCachePath = _getCacheFilePath(blobHash, true);
    final fullCachePath = _getCacheFilePath(blobHash, false);

    try {
      if (thumbCachePath.isNotEmpty) {
        final thumbFile = File(thumbCachePath);
        if (await thumbFile.exists()) {
          await thumbFile.delete();
          Logger.debug('Cleared thumbnail cache: $blobHash');
        }
      }
      if (fullCachePath.isNotEmpty) {
        final fullFile = File(fullCachePath);
        if (await fullFile.exists()) {
          await fullFile.delete();
          Logger.debug('Cleared full image cache: $blobHash');
        }
      }
    } catch (e) {
      Logger.warning('Failed to clear image cache for $blobHash: $e');
      // Don't throw - cache clearing is best effort
    }
  }
}