refactor: rewrite OpenAI integration

- use `OpenAI` and `Azure.AI.OpenAI`
- use `developer` role instead of `system` for OpenAI's `o1` series models
- use streaming response
- re-design `AIAssistant`

Signed-off-by: leo <longshuang@msn.cn>

src/Models/OpenAI.cs

@@ -1,81 +1,13 @@
 using System;
-using System.Collections.Generic;
-using System.Net.Http;
-using System.Text;
-using System.Text.Json;
-using System.Text.Json.Serialization;
+using System.ClientModel;
 using System.Threading;
-
+using Azure.AI.OpenAI;
 using CommunityToolkit.Mvvm.ComponentModel;
+using OpenAI;
+using OpenAI.Chat;
 
 namespace SourceGit.Models
 {
-    public class OpenAIChatMessage
-    {
-        [JsonPropertyName("role")]
-        public string Role
-        {
-            get;
-            set;
-        }
-
-        [JsonPropertyName("content")]
-        public string Content
-        {
-            get;
-            set;
-        }
-    }
-
-    public class OpenAIChatChoice
-    {
-        [JsonPropertyName("index")]
-        public int Index
-        {
-            get;
-            set;
-        }
-
-        [JsonPropertyName("message")]
-        public OpenAIChatMessage Message
-        {
-            get;
-            set;
-        }
-    }
-
-    public class OpenAIChatResponse
-    {
-        [JsonPropertyName("choices")]
-        public List<OpenAIChatChoice> Choices
-        {
-            get;
-            set;
-        } = [];
-    }
-
-    public class OpenAIChatRequest
-    {
-        [JsonPropertyName("model")]
-        public string Model
-        {
-            get;
-            set;
-        }
-
-        [JsonPropertyName("messages")]
-        public List<OpenAIChatMessage> Messages
-        {
-            get;
-            set;
-        } = [];
-
-        public void AddMessage(string role, string content)
-        {
-            Messages.Add(new OpenAIChatMessage { Role = role, Content = content });
-        }
-    }
-
     public class OpenAIService : ObservableObject
     {
         public string Name
@@ -147,48 +79,48 @@ namespace SourceGit.Models
                 """;
         }
 
-        public OpenAIChatResponse Chat(string prompt, string question, CancellationToken cancellation)
+        public void Chat(string prompt, string question, CancellationToken cancellation, Action<string> onUpdate)
         {
-            var chat = new OpenAIChatRequest() { Model = Model };
-            chat.AddMessage("user", prompt);
-            chat.AddMessage("user", question);
-
-            var client = new HttpClient() { Timeout = TimeSpan.FromSeconds(60) };
-            if (!string.IsNullOrEmpty(ApiKey))
+            Uri server = new(Server);
+            ApiKeyCredential key = new(ApiKey);
+            ChatClient client = null;
+            if (Server.Contains("openai.azure.com/", StringComparison.Ordinal))
             {
-                if (Server.Contains("openai.azure.com/", StringComparison.Ordinal))
-                    client.DefaultRequestHeaders.Add("api-key", ApiKey);
-                else
-                    client.DefaultRequestHeaders.Add("Authorization", $"Bearer {ApiKey}");
+                var azure = new AzureOpenAIClient(server, key);
+                client = azure.GetChatClient(Model);
+            }
+            else
+            {
+                var openai = new OpenAIClient(key, new() { Endpoint = server });
+                client = openai.GetChatClient(Model);
             }
 
-            var req = new StringContent(JsonSerializer.Serialize(chat, JsonCodeGen.Default.OpenAIChatRequest), Encoding.UTF8, "application/json");
             try
             {
-                var task = client.PostAsync(Server, req, cancellation);
-                task.Wait(cancellation);
+                var updates = client.CompleteChatStreaming([
+                    ShouldUseDeveloperPrompt() ? new DeveloperChatMessage(prompt) : new SystemChatMessage(prompt),
+                    new UserChatMessage(question),
+                ], null, cancellation);
 
-                var rsp = task.Result;
-                var reader = rsp.Content.ReadAsStringAsync(cancellation);
-                reader.Wait(cancellation);
-
-                var body = reader.Result;
-                if (!rsp.IsSuccessStatusCode)
+                foreach (var update in updates)
                 {
-                    throw new Exception($"AI service returns error code {rsp.StatusCode}. Body: {body ?? string.Empty}");
+                    if (update.ContentUpdate.Count > 0)
+                        onUpdate.Invoke(update.ContentUpdate[0].Text);
                 }
-
-                return JsonSerializer.Deserialize(reader.Result, JsonCodeGen.Default.OpenAIChatResponse);
             }
             catch
             {
-                if (cancellation.IsCancellationRequested)
-                    return null;
-
-                throw;
+                if (!cancellation.IsCancellationRequested)
+                    throw;
             }
         }
 
+        private bool ShouldUseDeveloperPrompt()
+        {
+            return _model.Equals("o1", StringComparison.Ordinal) ||
+                _model.Equals("o1-mini", StringComparison.Ordinal);
+        }
+
         private string _name;
         private string _server;
         private string _apiKey;