import 'dart:async';
import 'dart:convert';

import 'package:dio/dio.dart';
import 'package:flutter_riverpod/flutter_riverpod.dart';
import 'package:http/http.dart' as http;
import 'package:image_picker/image_picker.dart';

import '../../core/api/api_client.dart';
import '../../core/auth/auth_provider.dart';
import '../../core/auth/secure_storage.dart';
import '../../core/config/app_config.dart';
import '../../core/locale/language_provider.dart';

// ---------------------------------------------------------------------------
// Models
// ---------------------------------------------------------------------------

class RecognizedItem {
  final String name;
  double quantity;
  String unit;
  final String category;
  final double confidence;
  final String? mappingId;
  final int storageDays;

  RecognizedItem({
    required this.name,
    required this.quantity,
    required this.unit,
    required this.category,
    required this.confidence,
    this.mappingId,
    required this.storageDays,
  });

  factory RecognizedItem.fromJson(Map<String, dynamic> json) {
    return RecognizedItem(
      name: json['name'] as String? ?? '',
      quantity: (json['quantity'] as num?)?.toDouble() ?? 1.0,
      unit: json['unit'] as String? ?? 'pcs',
      category: json['category'] as String? ?? 'other',
      confidence: (json['confidence'] as num?)?.toDouble() ?? 0.0,
      mappingId: json['mapping_id'] as String?,
      storageDays: json['storage_days'] as int? ?? 7,
    );
  }
}

class UnrecognizedItem {
  final String rawText;
  final double? price;

  const UnrecognizedItem({required this.rawText, this.price});

  factory UnrecognizedItem.fromJson(Map<String, dynamic> json) {
    return UnrecognizedItem(
      rawText: json['raw_text'] as String? ?? '',
      price: (json['price'] as num?)?.toDouble(),
    );
  }
}

class ReceiptResult {
  final List<RecognizedItem> items;
  final List<UnrecognizedItem> unrecognized;

  const ReceiptResult({required this.items, required this.unrecognized});
}

/// A single dish recognition candidate with estimated nutrition for the portion in the photo.
class DishCandidate {
  final String? dishId;
  final String dishName;
  final int weightGrams;
  final double calories;
  final double proteinG;
  final double fatG;
  final double carbsG;
  final double confidence;

  const DishCandidate({
    this.dishId,
    required this.dishName,
    required this.weightGrams,
    required this.calories,
    required this.proteinG,
    required this.fatG,
    required this.carbsG,
    required this.confidence,
  });

  factory DishCandidate.fromJson(Map<String, dynamic> json) {
    return DishCandidate(
      dishId: json['dish_id'] as String?,
      dishName: json['dish_name'] as String? ?? '',
      weightGrams: json['weight_grams'] as int? ?? 0,
      calories: (json['calories'] as num?)?.toDouble() ?? 0,
      proteinG: (json['protein_g'] as num?)?.toDouble() ?? 0,
      fatG: (json['fat_g'] as num?)?.toDouble() ?? 0,
      carbsG: (json['carbs_g'] as num?)?.toDouble() ?? 0,
      confidence: (json['confidence'] as num?)?.toDouble() ?? 0,
    );
  }
}

/// Result of dish recognition: ordered list of candidates (best match first).
class DishResult {
  final List<DishCandidate> candidates;

  const DishResult({required this.candidates});

  /// The best matching candidate.
  DishCandidate get best => candidates.first;

  // Convenience getters delegating to the best candidate.
  String get dishName    => best.dishName;
  int    get weightGrams => best.weightGrams;
  double get calories    => best.calories;
  double get proteinG    => best.proteinG;
  double get fatG        => best.fatG;
  double get carbsG      => best.carbsG;
  double get confidence  => best.confidence;

  factory DishResult.fromJson(Map<String, dynamic> json) {
    // New format: {"candidates": [...]}
    if (json['candidates'] is List) {
      final candidatesList = (json['candidates'] as List<dynamic>)
          .map((element) => DishCandidate.fromJson(element as Map<String, dynamic>))
          .toList();
      return DishResult(candidates: candidatesList);
    }

    // Legacy flat format: {"dish_name": "...", "calories": ..., ...}
    if (json['dish_name'] != null) {
      return DishResult(candidates: [DishCandidate.fromJson(json)]);
    }

    return const DishResult(candidates: []);
  }
}

// ---------------------------------------------------------------------------
// Async job models
// ---------------------------------------------------------------------------

/// A lightweight summary of a dish recognition job (no image payload).
class DishJobSummary {
  final String id;
  final String status;
  final String? targetDate;
  final String? targetMealType;
  final DishResult? result;
  final String? error;
  final DateTime createdAt;

  const DishJobSummary({
    required this.id,
    required this.status,
    this.targetDate,
    this.targetMealType,
    this.result,
    this.error,
    required this.createdAt,
  });

  factory DishJobSummary.fromJson(Map<String, dynamic> json) {
    return DishJobSummary(
      id: json['id'] as String,
      status: json['status'] as String? ?? '',
      targetDate: json['target_date'] as String?,
      targetMealType: json['target_meal_type'] as String?,
      result: json['result'] != null
          ? DishResult.fromJson(json['result'] as Map<String, dynamic>)
          : null,
      error: json['error'] as String?,
      createdAt: DateTime.parse(json['created_at'] as String),
    );
  }
}

/// The 202 response from POST /ai/recognize-dish.
class DishJobCreated {
  final String jobId;
  final int queuePosition;
  final int estimatedSeconds;

  const DishJobCreated({
    required this.jobId,
    required this.queuePosition,
    required this.estimatedSeconds,
  });

  factory DishJobCreated.fromJson(Map<String, dynamic> json) {
    return DishJobCreated(
      jobId: json['job_id'] as String,
      queuePosition: json['queue_position'] as int? ?? 0,
      estimatedSeconds: json['estimated_seconds'] as int? ?? 0,
    );
  }
}

/// Events emitted by the SSE stream for a dish recognition job.
sealed class DishJobEvent {}

class DishJobQueued extends DishJobEvent {
  final int position;
  final int estimatedSeconds;
  DishJobQueued({required this.position, required this.estimatedSeconds});
}

class DishJobProcessing extends DishJobEvent {}

class DishJobDone extends DishJobEvent {
  final DishResult result;
  DishJobDone(this.result);
}

class DishJobFailed extends DishJobEvent {
  final String error;
  DishJobFailed(this.error);
}

// ---------------------------------------------------------------------------
// Service
// ---------------------------------------------------------------------------

class RecognitionService {
  const RecognitionService(
    this._client,
    this._storage,
    this._appConfig,
    this._languageGetter,
  );

  final ApiClient _client;
  final SecureStorageService _storage;
  final AppConfig _appConfig;
  final String Function() _languageGetter;

  /// Recognizes food items from a receipt photo.
  Future<ReceiptResult> recognizeReceipt(XFile image) async {
    final payload = await _buildImagePayload(image);
    final data = await _client.post('/ai/recognize-receipt', data: payload);
    return ReceiptResult(
      items: (data['items'] as List<dynamic>? ?? [])
          .map((element) => RecognizedItem.fromJson(element as Map<String, dynamic>))
          .toList(),
      unrecognized: (data['unrecognized'] as List<dynamic>? ?? [])
          .map((element) => UnrecognizedItem.fromJson(element as Map<String, dynamic>))
          .toList(),
    );
  }

  /// Recognizes food items from 1–3 product photos.
  Future<List<RecognizedItem>> recognizeProducts(List<XFile> images) async {
    final imageList = await Future.wait(images.map(_buildImagePayload));
    final data = await _client.post(
      '/ai/recognize-products',
      data: {'images': imageList},
    );
    return (data['items'] as List<dynamic>? ?? [])
        .map((element) => RecognizedItem.fromJson(element as Map<String, dynamic>))
        .toList();
  }

  /// Submits a dish image for async recognition.
  /// Returns a [DishJobCreated] with the job ID and queue position.
  Future<DishJobCreated> submitDishRecognition(
    XFile image, {
    String? targetDate,
    String? targetMealType,
  }) async {
    final imagePayload = await _buildImagePayload(image);
    final payload = <String, dynamic>{...imagePayload};
    if (targetDate != null) payload['target_date'] = targetDate;
    if (targetMealType != null) payload['target_meal_type'] = targetMealType;
    final data = await _client.post('/ai/recognize-dish', data: payload);
    return DishJobCreated.fromJson(data);
  }

  /// Returns today's recognition jobs that have not yet been linked to a diary entry.
  Future<List<DishJobSummary>> listTodayUnlinkedJobs() async {
    final data = await _client.getList('/ai/jobs');
    return data
        .map((element) =>
            DishJobSummary.fromJson(element as Map<String, dynamic>))
        .toList();
  }

  /// Returns all recognition jobs for the current user, newest first.
  Future<List<DishJobSummary>> listAllJobs() async {
    final data = await _client.getList('/ai/jobs/history');
    return data
        .map((element) =>
            DishJobSummary.fromJson(element as Map<String, dynamic>))
        .toList();
  }

  /// Opens an SSE stream for job [jobId] and emits [DishJobEvent]s until the
  /// job reaches a terminal state (done or failed) or the stream is cancelled.
  ///
  /// Uses [http.Client] instead of Dio because on Flutter Web Dio relies on
  /// XHR which does not support SSE streaming. [http.BrowserClient] reads the
  /// response via XHR onProgress events and delivers chunks before the
  /// connection is closed.
  Stream<DishJobEvent> streamJobEvents(String jobId) async* {
    final token = await _storage.getAccessToken();
    final language = _languageGetter();
    final uri = Uri.parse('${_appConfig.apiBaseUrl}/ai/jobs/$jobId/stream');

    final httpClient = http.Client();
    try {
      final request = http.Request('GET', uri)
        ..headers['Authorization'] = token != null ? 'Bearer $token' : ''
        ..headers['Accept'] = 'text/event-stream'
        ..headers['Accept-Language'] = language
        ..headers['Cache-Control'] = 'no-cache';

      final response = await httpClient.send(request).timeout(
        const Duration(seconds: 30),
      );

      final buffer = StringBuffer();
      String? currentEventName;

      await for (final chunk in response.stream.map(utf8.decode)) {
        buffer.write(chunk);
        final text = buffer.toString();

        // Process complete SSE messages (terminated by \n\n).
        int doubleNewlineIndex;
        var remaining = text;
        while ((doubleNewlineIndex = remaining.indexOf('\n\n')) != -1) {
          final message = remaining.substring(0, doubleNewlineIndex);
          remaining = remaining.substring(doubleNewlineIndex + 2);

          for (final line in message.split('\n')) {
            if (line.startsWith('event:')) {
              currentEventName = line.substring(6).trim();
            } else if (line.startsWith('data:')) {
              final dataPayload = line.substring(5).trim();
              final event = _parseSseEvent(currentEventName, dataPayload);
              if (event != null) {
                yield event;
                if (event is DishJobDone || event is DishJobFailed) return;
              }
              currentEventName = null;
            }
          }
        }

        buffer
          ..clear()
          ..write(remaining);
      }
    } finally {
      httpClient.close();
    }
  }

  DishJobEvent? _parseSseEvent(String? eventName, String dataPayload) {
    try {
      final json = jsonDecode(dataPayload) as Map<String, dynamic>;
      switch (eventName) {
        case 'queued':
          return DishJobQueued(
            position: json['position'] as int? ?? 0,
            estimatedSeconds: json['estimated_seconds'] as int? ?? 0,
          );
        case 'processing':
          return DishJobProcessing();
        case 'done':
          return DishJobDone(DishResult.fromJson(json));
        case 'failed':
          return DishJobFailed(json['error'] as String? ?? 'Recognition failed');
        default:
          return null;
      }
    } catch (_) {
      return null;
    }
  }

  Future<Map<String, String>> _buildImagePayload(XFile image) async {
    final bytes = await image.readAsBytes();
    final base64Data = base64Encode(bytes);
    // XFile.mimeType may be null on some platforms; fall back to path extension.
    final mimeType = image.mimeType ??
        (image.path.toLowerCase().endsWith('.png') ? 'image/png' : 'image/jpeg');
    return {'image_base64': base64Data, 'mime_type': mimeType};
  }
}

final recognitionServiceProvider = Provider<RecognitionService>((ref) {
  final config = ref.read(appConfigProvider);
  final storage = ref.read(secureStorageProvider);
  return RecognitionService(
    ref.read(apiClientProvider),
    storage,
    config,
    () => ref.read(languageProvider),
  );
});