import 'dart:async';
import 'dart:convert';
import 'package:http/http.dart' as http;

/// OpenAI API client for Dart
class OpenAI {
  final String apiKey;
  final String baseUrl;
  final http.Client _client;

  OpenAI({
    required this.apiKey,
    this.baseUrl = 'https://api.openai.com/v1',
    http.Client? client,
  }) : _client = client ?? http.Client();

  /// Access to chat completions API
  ChatCompletions get chat => ChatCompletions(this);

  /// Access to embeddings API
  Embeddings get embeddings => Embeddings(this);

  void dispose() {
    _client.close();
  }
}

/// Chat completions API
class ChatCompletions {
  final OpenAI _openai;

  ChatCompletions(this._openai);

  /// Access to completions endpoint
  Completions get completions => Completions(_openai);
}

/// Completions endpoint
class Completions {
  final OpenAI _openai;

  Completions(this._openai);

  /// Create a chat completion
  ///
  /// If [stream] is true, returns a Stream of ChatCompletionChunk
  /// If [stream] is false, returns a single ChatCompletion
  Future<dynamic> create({
    required String model,
    required List<dynamic> messages,
    bool stream = false,
    StreamOptions? streamOptions,
    double? temperature,
    double? topP,
    int? n,
    List<String>? stop,
    int? maxTokens,
    double? presencePenalty,
    double? frequencyPenalty,
    Map<String, dynamic>? logitBias,
    String? user,
  }) async {
    final body = {
      'model': model,
      'messages': messages,
      'stream': stream,
      if (streamOptions != null) 'stream_options': streamOptions.toJson(),
      if (temperature != null) 'temperature': temperature,
      if (topP != null) 'top_p': topP,
      if (n != null) 'n': n,
      if (stop != null) 'stop': stop,
      if (maxTokens != null) 'max_tokens': maxTokens,
      if (presencePenalty != null) 'presence_penalty': presencePenalty,
      if (frequencyPenalty != null) 'frequency_penalty': frequencyPenalty,
      if (logitBias != null) 'logit_bias': logitBias,
      if (user != null) 'user': user,
    };

    if (stream) {
      return _streamCompletion(body);
    } else {
      return _createCompletion(body);
    }
  }

  Future<ChatCompletion> _createCompletion(Map<String, dynamic> body) async {
    final response = await _openai._client.post(
      Uri.parse('${_openai.baseUrl}/chat/completions'),
      headers: {
        'Content-Type': 'application/json',
        'Authorization': 'Bearer ${_openai.apiKey}',
      },
      body: jsonEncode(body),
    );

    if (response.statusCode != 200) {
      throw OpenAIException(
        statusCode: response.statusCode,
        message: response.body,
      );
    }

    return ChatCompletion.fromJson(jsonDecode(response.body));
  }

  Stream<ChatCompletionChunk> _streamCompletion(
      Map<String, dynamic> body) async* {
    final request = http.Request(
      'POST',
      Uri.parse('${_openai.baseUrl}/chat/completions'),
    );

    request.headers.addAll({
      'Content-Type': 'application/json',
      'Authorization': 'Bearer ${_openai.apiKey}',
    });

    request.body = jsonEncode(body);

    final streamedResponse = await _openai._client.send(request);

    if (streamedResponse.statusCode != 200) {
      final body = await streamedResponse.stream.bytesToString();
      throw OpenAIException(
        statusCode: streamedResponse.statusCode,
        message: body,
      );
    }

    final stream = streamedResponse.stream
        .transform(utf8.decoder)
        .transform(const LineSplitter());

    await for (final line in stream) {
      if (line.isEmpty) continue;
      if (line.startsWith(':')) continue; // Skip comments
      if (!line.startsWith('data: ')) continue;

      final data = line.substring(6); // Remove 'data: ' prefix

      if (data == '[DONE]') {
        break;
      }

      try {
        final json = jsonDecode(data);
        yield ChatCompletionChunk.fromJson(json);
      } catch (e) {
        // Skip malformed chunks
        continue;
      }
    }
  }
}

/// Chat message
class ChatMessage {
  final String role;
  final String content;

  ChatMessage({
    required this.role,
    required this.content,
  });

  Map<String, dynamic> toJson() => {
        'role': role,
        'content': content,
      };

  factory ChatMessage.fromJson(Map<String, dynamic> json) => ChatMessage(
        role: json['role'],
        content: json['content'],
      );

  factory ChatMessage.system(String content) =>
      ChatMessage(role: 'system', content: content);

  factory ChatMessage.user(String content) =>
      ChatMessage(role: 'user', content: content);

  factory ChatMessage.assistant(String content) =>
      ChatMessage(role: 'assistant', content: content);
}

/// Stream options
class StreamOptions {
  final bool includeUsage;

  StreamOptions({this.includeUsage = false});

  Map<String, dynamic> toJson() => {
        'include_usage': includeUsage,
      };
}

/// Chat completion response (non-streaming)
class ChatCompletion {
  final String id;
  final String object;
  final int created;
  final String model;
  final List<Choice> choices;
  final Usage? usage;

  ChatCompletion({
    required this.id,
    required this.object,
    required this.created,
    required this.model,
    required this.choices,
    this.usage,
  });

  factory ChatCompletion.fromJson(Map<String, dynamic> json) => ChatCompletion(
        id: json['id'],
        object: json['object'],
        created: json['created'],
        model: json['model'],
        choices: (json['choices'] as List)
            .map((c) => Choice.fromJson(c))
            .toList(),
        usage: json['usage'] != null ? Usage.fromJson(json['usage']) : null,
      );
}

/// Chat completion chunk (streaming)
class ChatCompletionChunk {
  final String id;
  final String object;
  final int created;
  final String model;
  final List<ChunkChoice> choices;
  final Usage? usage;

  ChatCompletionChunk({
    required this.id,
    required this.object,
    required this.created,
    required this.model,
    required this.choices,
    this.usage,
  });

  factory ChatCompletionChunk.fromJson(Map<String, dynamic> json) =>
      ChatCompletionChunk(
        id: json['id'],
        object: json['object'],
        created: json['created'],
        model: json['model'],
        choices: (json['choices'] as List)
            .map((c) => ChunkChoice.fromJson(c))
            .toList(),
        usage: json['usage'] != null ? Usage.fromJson(json['usage']) : null,
      );
}

/// Choice in non-streaming response
class Choice {
  final int index;
  final ChatMessage message;
  final String? finishReason;

  Choice({
    required this.index,
    required this.message,
    this.finishReason,
  });

  factory Choice.fromJson(Map<String, dynamic> json) => Choice(
        index: json['index'],
        message: ChatMessage.fromJson(json['message']),
        finishReason: json['finish_reason'],
      );
}

/// Choice in streaming response
class ChunkChoice {
  final int index;
  final Delta? delta;
  final String? finishReason;

  ChunkChoice({
    required this.index,
    this.delta,
    this.finishReason,
  });

  factory ChunkChoice.fromJson(Map<String, dynamic> json) => ChunkChoice(
        index: json['index'],
        delta: json['delta'] != null ? Delta.fromJson(json['delta']) : null,
        finishReason: json['finish_reason'],
      );
}

/// Delta content in streaming chunks
class Delta {
  final String? role;
  final String? content;

  Delta({
    this.role,
    this.content,
  });

  factory Delta.fromJson(Map<String, dynamic> json) => Delta(
        role: json['role'],
        content: json['content'],
      );
}

/// Token usage information
class Usage {
  final int? promptTokens;
  final int? completionTokens;
  final int? totalTokens;

  Usage({
    this.promptTokens,
    this.completionTokens,
    this.totalTokens,
  });

  factory Usage.fromJson(Map<String, dynamic> json) => Usage(
        promptTokens: json['prompt_tokens'],
        completionTokens: json['completion_tokens'],
        totalTokens: json['total_tokens'],
      );

  Map<String, dynamic> toJson() => {
        if (promptTokens != null) 'prompt_tokens': promptTokens,
        if (completionTokens != null) 'completion_tokens': completionTokens,
        if (totalTokens != null) 'total_tokens': totalTokens,
      };
}

/// OpenAI API exception
class OpenAIException implements Exception {
  final int statusCode;
  final String message;

  OpenAIException({
    required this.statusCode,
    required this.message,
  });

  @override
  String toString() => 'OpenAIException($statusCode): $message';
}

/// Embeddings API
class Embeddings {
  final OpenAI _openai;

  Embeddings(this._openai);

  /// Create embeddings for input text
  Future<EmbeddingResponse> create({
    required String model,
    required dynamic input, // String or List<String>
    String? user,
    String? encodingFormat, // 'float' or 'base64'
    int? dimensions,
  }) async {
    final body = {
      'model': model,
      'input': input,
      if (user != null) 'user': user,
      if (encodingFormat != null) 'encoding_format': encodingFormat,
      if (dimensions != null) 'dimensions': dimensions,
    };

    final response = await _openai._client.post(
      Uri.parse('${_openai.baseUrl}/embeddings'),
      headers: {
        'Content-Type': 'application/json',
        'Authorization': 'Bearer ${_openai.apiKey}',
      },
      body: jsonEncode(body),
    );

    if (response.statusCode != 200) {
      throw OpenAIException(
        statusCode: response.statusCode,
        message: response.body,
      );
    }

    return EmbeddingResponse.fromJson(jsonDecode(response.body));
  }
}

/// Embedding response
class EmbeddingResponse {
  final String object;
  final List<Embedding> data;
  final String model;
  final Usage? usage;

  EmbeddingResponse({
    required this.object,
    required this.data,
    required this.model,
    this.usage,
  });

  factory EmbeddingResponse.fromJson(Map<String, dynamic> json) =>
      EmbeddingResponse(
        object: json['object'],
        data: (json['data'] as List).map((e) => Embedding.fromJson(e)).toList(),
        model: json['model'],
        usage: json['usage'] != null ? Usage.fromJson(json['usage']) : null,
      );
}

/// Individual embedding
class Embedding {
  final String object;
  final int index;
  final List<double> embedding;

  Embedding({
    required this.object,
    required this.index,
    required this.embedding,
  });

  factory Embedding.fromJson(Map<String, dynamic> json) => Embedding(
    object: json['object'],
    index: json['index'],
    embedding: (json['embedding'] as List).map<double>((e) => (e as num).toDouble()).toList(),
  );

}