feat: models for chat api

example/lib/main.dart

@@ -3,6 +3,7 @@ import 'dart:developer';
 import 'dart:io';
 
 import 'package:openai_client/openai_client.dart';
+import 'package:openai_client/src/model/openai_chat/chat_message.dart';
 
 Future<void> main() async {
   // Load app credentials from environment variables or file.
@@ -34,6 +35,18 @@ Future<void> main() async {
   // Print the completion.
   log(completion.toString());
 
+  // Create a chat.
+  final chat = await client.chat
+      .create(
+          model: 'gpt-3.5-turbo',
+          message: const ChatMessage(
+            role: 'user',
+            content: 'How do you think is Batman dealing with Robin recently?',
+          ))
+      .data;
+  // Print the chat.
+  log(chat.toString());
+
   // Create an edit.
   final edit = await client.edits
       .create(

lib/src/chat.dart

@@ -0,0 +1,85 @@
+import 'package:http/http.dart' as http;
+import 'package:openai_client/src/client.dart';
+import 'package:openai_client/src/logger/logger.dart';
+import 'package:openai_client/src/model/openai_chat/openai_chat.dart';
+import 'package:openai_client/src/network/network.dart';
+
+/// Given a chat conversation, the model will return a chat completion response.
+///
+/// For more detail see the [OpenAI API documentation](https://beta.openai.com/docs/api-reference/chat).
+class OpenAIChat {
+  /// Creates a new instance which belongs to [client].
+  OpenAIChat(this.client) : baseUrl = client.baseUrl.resolve(apiChat);
+
+  /// The parent [OpenAIClient].
+  final OpenAIClient client;
+
+  /// The base url for all endpoints for [Chat].
+  ///
+  /// See more at [Chat](https://beta.openai.com/docs/api-reference/chat).
+  final Uri baseUrl;
+
+  /// Creates a completion for the chat message.
+  ///
+  /// A deeper explanation of the parameters can be
+  /// found in the [OpenAI API documentation](https://beta.openai.com/docs/api-reference/chat/create).
+  Request<Chat> create({
+    required String model,
+    required ChatMessage message,
+    double? temperature = 1.0,
+    double? topP = 1.0,
+    int? n = 1,
+    bool stream = false,
+    String? stop,
+    int? maxTokens,
+    int? presencePenalty = 0,
+    int? frequencyPenalty = 0,
+    Map<String, dynamic>? logitBias,
+    String? user,
+  }) {
+    Logger(
+      title: 'Chat',
+      description: 'Fetching is started...',
+      level: Level.debug,
+      isActive: client.enableLogging,
+    );
+
+    if (temperature != null) {
+      assert(
+        temperature > 0 && temperature <= 2,
+        'Temperature must be between 0 and 2',
+      );
+    }
+
+    final jsonBody = <String, dynamic>{
+      'model': model,
+      'message': message.toJson(),
+      'temperature': temperature,
+      'top_p': topP,
+      'n': n,
+      'stream': stream,
+      if (stop != null) 'stop': stop,
+      if (maxTokens != null) 'max_tokens': maxTokens,
+      'presence_penalty': presencePenalty,
+      'frequency_penalty': frequencyPenalty,
+      if (logitBias != null) 'logit_bias': logitBias,
+      if (user != null) 'user': user,
+    };
+
+    final req = Request(
+      client: client,
+      httpRequest: http.Request('POST', baseUrl),
+      bodyDeserializer: (body) => Chat.fromMap(body as Map<String, dynamic>),
+      jsonBody: jsonBody,
+    );
+
+    Logger(
+      title: 'Chat',
+      description: 'Returning the request...',
+      level: Level.info,
+      isActive: client.enableLogging,
+    );
+
+    return req;
+  }
+}

lib/src/client.dart

@@ -1,4 +1,5 @@
 import 'package:http/http.dart' as http;
+import 'package:openai_client/src/chat.dart';
 import 'package:openai_client/src/completions.dart';
 import 'package:openai_client/src/configuration.dart';
 import 'package:openai_client/src/edits.dart';
@@ -54,6 +55,9 @@ class OpenAIClient {
   /// Provides access to resources related to [Completions].
   OpenAICompletions get completions => OpenAICompletions(this);
 
+  /// Provides access to resources related to [Completions].
+  OpenAIChat get chat => OpenAIChat(this);
+
   /// Provides access to resources related to [Edits].
   OpenAIEdits get edits => OpenAIEdits(this);
 

lib/src/model/openai_chat/chat.dart

@@ -0,0 +1,89 @@
+import 'dart:convert';
+
+import 'package:equatable/equatable.dart';
+import 'package:openai_client/src/model/openai_chat/chat_choice.dart';
+import 'package:openai_client/src/model/shared_models/shared_models.dart';
+
+/// The chat class.
+class Chat extends Equatable {
+  /// Instance of [Chat].
+  const Chat({
+    required this.id,
+    required this.object,
+    required this.created,
+    required this.choices,
+    required this.usage,
+  });
+
+  /// `dart:convert`
+  ///
+  /// Parses the string and returns the resulting Json object as [OpenAiChat].
+  factory Chat.fromJson(String data) {
+    return Chat.fromMap(json.decode(data) as Map<String, dynamic>);
+  }
+
+  /// `dart:convert`
+  ///
+  /// Parses the string and returns the resulting Json object as [Chat].
+  factory Chat.fromMap(Map<String, dynamic> data) => Chat(
+        id: data['id'] as String,
+        object: data['object'] as String,
+        created: data['created'] as int,
+        choices: (data['choices'] as List<dynamic>)
+            .map((e) => ChatChoice.fromMap(e as Map<String, dynamic>))
+            .toList(),
+        usage: Usage.fromMap(data['usage'] as Map<String, dynamic>),
+      );
+
+  /// The chat id.
+  final String id;
+
+  /// The chat object.
+  final String object;
+
+  /// The chat created.
+  final int created;
+
+  /// The chat choices.
+  final List<ChatChoice> choices;
+
+  /// The chat usage.
+  final Usage usage;
+
+  /// Mappping from [Map] to [Chat].
+  Map<String, dynamic> toMap() => {
+        'id': id,
+        'object': object,
+        'created': created,
+        'choices': choices.map((e) => e.toMap()).toList(),
+        'usage': usage.toMap(),
+      };
+
+  /// `dart:convert`
+  ///
+  /// Converts [OpenAiChat] to a JSON string.
+  String toJson() => json.encode(toMap());
+
+  /// Copy with extension.
+  Chat copyWith({
+    String? id,
+    String? object,
+    int? created,
+    List<ChatChoice>? choices,
+    Usage? usage,
+  }) {
+    return Chat(
+      id: id ?? this.id,
+      object: object ?? this.object,
+      created: created ?? this.created,
+      choices: choices ?? this.choices,
+      usage: usage ?? this.usage,
+    );
+  }
+
+  @override
+  bool get stringify => true;
+
+  @override
+  List<Object?> get props => [id, object, created, choices, usage];
+}

lib/src/model/openai_chat/chat_choice.dart

@@ -0,0 +1,71 @@
+import 'dart:convert';
+
+import 'package:equatable/equatable.dart';
+
+import 'package:openai_client/src/model/openai_chat/chat_message.dart';
+
+/// The chat choice class.
+class ChatChoice extends Equatable {
+  /// Instance of [ChatChoice].
+  const ChatChoice({
+    required this.index,
+    required this.message,
+    required this.finishReason,
+  });
+
+  /// `dart:convert`
+  ///
+  /// Parses the string and returns the resulting Json object as [Choice].
+  factory ChatChoice.fromJson(String data) {
+    return ChatChoice.fromMap(json.decode(data) as Map<String, dynamic>);
+  }
+
+  /// `dart:convert`
+  ///
+  /// Parses the string and returns the resulting Json object as [ChatChoice].
+  factory ChatChoice.fromMap(Map<String, dynamic> data) => ChatChoice(
+        index: data['index'] as int,
+        message: ChatMessage.fromMap(data['message'] as Map<String, dynamic>),
+        finishReason: data['finish_reason'] as String,
+      );
+
+  /// The index of the choice.
+  final int index;
+
+  /// The message.
+  final ChatMessage message;
+
+  /// The finish reason.
+  final String finishReason;
+
+  /// Mappping from [Map] to [ChatChoice].
+  Map<String, dynamic> toMap() => {
+        'index': index,
+        'message': message.toMap(),
+        'finish_reason': finishReason,
+      };
+
+  /// `dart:convert`
+  ///
+  /// Converts [Choice] to a JSON string.
+  String toJson() => json.encode(toMap());
+
+  /// Copy with extension.
+  ChatChoice copyWith({
+    int? index,
+    ChatMessage? message,
+    String? finishReason,
+  }) {
+    return ChatChoice(
+      index: index ?? this.index,
+      message: message ?? this.message,
+      finishReason: finishReason ?? this.finishReason,
+    );
+  }
+
+  @override
+  bool get stringify => true;
+
+  @override
+  List<Object?> get props => [index, message, finishReason];
+}

lib/src/model/openai_chat/chat_message.dart

@@ -0,0 +1,61 @@
+import 'dart:convert';
+
+import 'package:equatable/equatable.dart';
+
+/// The message class.
+class ChatMessage extends Equatable {
+  /// Instance of [Message].
+  const ChatMessage({
+    required this.role,
+    required this.content,
+  });
+
+  /// `dart:convert`
+  ///
+  /// Parses the string and returns the resulting Json object as [Message].
+  factory ChatMessage.fromJson(String data) {
+    return ChatMessage.fromMap(json.decode(data) as Map<String, dynamic>);
+  }
+
+  /// `dart:convert`
+  ///
+  /// Parses the string and returns the resulting Json object as [Message].
+  factory ChatMessage.fromMap(Map<String, dynamic> data) => ChatMessage(
+        role: data['role'] as String,
+        content: data['content'] as String,
+      );
+
+  /// The message role.
+  final String role;
+
+  /// The message content.
+  final String content;
+
+  /// Mappping from [Map] to [Message].
+  Map<String, dynamic> toMap() => {
+        'role': role,
+        'content': content,
+      };
+
+  /// `dart:convert`
+  ///
+  /// Converts [Message] to a JSON string.
+  String toJson() => json.encode(toMap());
+
+  /// Copy with extension.
+  ChatMessage copyWith({
+    String? role,
+    String? content,
+  }) {
+    return ChatMessage(
+      role: role ?? this.role,
+      content: content ?? this.content,
+    );
+  }
+
+  @override
+  bool get stringify => true;
+
+  @override
+  List<Object?> get props => [role, content];
+}

lib/src/model/openai_chat/openai_chat.dart

@@ -0,0 +1,3 @@
+export 'chat.dart';
+export 'chat_choice.dart';
+export 'chat_message.dart';

lib/src/network/endpoints.dart

@@ -10,6 +10,9 @@ const apiModels = 'models';
 /// The base url for all endpoints for [Completions].
 const apiCompletions = 'completions';
 
+/// The base url for all endpoints for [Chat].
+const apiChat = 'chat/completions';
+
 /// The base url for all endpoints for [Edits].
 const apiEdits = 'edits';