Hack ChatGPTService to support GitHub copilot chat

Author: intitni

Tool/Sources/OpenAIService/APIs/BuiltinExtensionChatCompletionsService.swift

@@ -0,0 +1,106 @@
+import AsyncAlgorithms
+import BuiltinExtension
+import ChatBasic
+import Foundation
+import XcodeInspector
+
+#warning("This is a temporary implementation for proof of concept.")
+
+actor BuiltinExtensionChatCompletionsService {
+    typealias RequestBody = ChatCompletionsRequestBody
+
+    enum CustomError: Swift.Error, LocalizedError {
+        case chatServiceNotFound
+
+        var errorDescription: String? {
+            switch self {
+            case .chatServiceNotFound:
+                return "Chat service not found."
+            }
+        }
+    }
+
+    var extensionManager: BuiltinExtensionManager { .shared }
+
+    let extensionIdentifier: String
+    let requestBody: RequestBody
+
+    init(extensionIdentifier: String, requestBody: RequestBody) {
+        self.extensionIdentifier = extensionIdentifier
+        self.requestBody = requestBody
+    }
+}
+
+extension BuiltinExtensionChatCompletionsService: ChatCompletionsAPI {
+    func callAsFunction() async throws -> ChatCompletionResponseBody {
+        fatalError()
+    }
+}
+
+extension BuiltinExtensionChatCompletionsService: ChatCompletionsStreamAPI {
+    func callAsFunction(
+    ) async throws -> AsyncThrowingStream<ChatCompletionsStreamDataChunk, Error> {
+        let service = try getChatService()
+        let (message, history) = extractMessageAndHistory(from: requestBody)
+        guard let workspaceURL = XcodeInspector.shared.realtimeActiveWorkspaceURL,
+              let projectURL = XcodeInspector.shared.realtimeActiveProjectURL
+        else { throw CancellationError() }
+        let stream = await service.sendMessage(
+            message,
+            history: history,
+            references: [],
+            workspace: .init(
+                workspaceURL: workspaceURL,
+                projectURL: projectURL
+            )
+        )
+
+        return stream.map { text in
+            ChatCompletionsStreamDataChunk(
+                id: nil,
+                object: nil,
+                model: nil,
+                message: .init(
+                    role: .assistant,
+                    content: text,
+                    toolCalls: nil
+                ),
+                finishReason: nil
+            )
+        }.toStream()
+    }
+}
+
+extension BuiltinExtensionChatCompletionsService {
+    func getChatService() throws -> any BuiltinExtensionChatServiceType {
+        guard let ext = extensionManager.extensions
+            .first(where: { $0.extensionIdentifier == extensionIdentifier }),
+            let service = ext.chatService as? BuiltinExtensionChatServiceType
+        else {
+            throw CustomError.chatServiceNotFound
+        }
+        return service
+    }
+}
+
+extension BuiltinExtensionChatCompletionsService {
+    func extractMessageAndHistory(
+        from request: RequestBody
+    ) -> (message: String, history: [ChatMessage]) {
+        let messages = request.messages
+
+        if let lastIndexNotUserMessage = messages.lastIndex(where: { $0.role != .user }) {
+            let message = messages[(lastIndexNotUserMessage + 1)...]
+                .map { $0.content }
+                .joined(separator: "\n\n")
+            let history = Array(messages[0...lastIndexNotUserMessage])
+            return (message, history.map {
+                .init(id: UUID().uuidString, role: $0.role.asChatMessageRole, content: $0.content)
+            })
+        } else { // everything is user message
+            let message = messages.map { $0.content }.joined(separator: "\n\n")
+            return (message, [])
+        }
+    }
+}
+

Tool/Sources/OpenAIService/ChatGPTService.swift

@@ -90,13 +90,21 @@ public class ChatGPTService: ChatGPTServiceType {
     var runningTask: Task<Void, Never>?
     var buildCompletionStreamAPI: ChatCompletionsStreamAPIBuilder = {
         apiKey, model, endpoint, requestBody, prompt in
+
+        if model.id == "com.github.copilot" {
+            return BuiltinExtensionChatCompletionsService(
+                extensionIdentifier: model.id,
+                requestBody: requestBody
+            )
+        }
+
         switch model.format {
         case .googleAI:
             return GoogleAIChatCompletionsService(
                 apiKey: apiKey,
                 model: model,
                 requestBody: requestBody,
-                prompt: prompt, 
+                prompt: prompt,
                 baseURL: endpoint.absoluteString
             )
         case .openAI, .openAICompatible, .azureOpenAI:
@@ -125,6 +133,14 @@ public class ChatGPTService: ChatGPTServiceType {
 
     var buildCompletionAPI: ChatCompletionsAPIBuilder = {
         apiKey, model, endpoint, requestBody, prompt in
+
+        if model.id == "com.github.copilot" {
+            return BuiltinExtensionChatCompletionsService(
+                extensionIdentifier: model.id,
+                requestBody: requestBody
+            )
+        }
+
         switch model.format {
         case .googleAI:
             return GoogleAIChatCompletionsService(

Tool/Sources/OpenAIService/Configuration/UserPreferenceChatGPTConfiguration.swift

@@ -16,12 +16,18 @@ public struct UserPreferenceChatGPTConfiguration: ChatGPTConfiguration {
 
         if let chatModelKey {
             let id = UserDefaults.shared.value(for: chatModelKey)
+            if id == "com.github.copilot" {
+                return .init(id: id, name: "GitHub Copilot", format: .openAI, info: .init())
+            }
             if let model = models.first(where: { $0.id == id }) {
                 return model
             }
         }
 
         let id = UserDefaults.shared.value(for: \.defaultChatFeatureChatModelId)
+        if id == "com.github.copilot" {
+            return .init(id: id, name: "GitHub Copilot", format: .openAI, info: .init())
+        }
         return models.first { $0.id == id }
             ?? models.first
     }