feat: implement message regeneration functionality in ChatProvider

Sources/Agent/chat/openaiChat.swift

@@ -219,6 +219,13 @@ public struct OpenAIUserMessage: Hashable, Codable, Sendable {
         self.content = try container.decode(String.self, forKey: .content)
         self.createdAt = try container.decodeIfPresent(Date.self, forKey: .createdAt) ?? Date()
     }
+
+    public func encode(to encoder: Encoder) throws {
+        var container = encoder.container(keyedBy: CodingKeys.self)
+        try container.encode(role, forKey: .role)
+        try container.encode(content, forKey: .content)
+        // Exclude id and createdAt - not part of OpenAI API spec
+    }
 }
 
 public struct OpenAIAssistantMessage: Hashable, Codable, Sendable {
@@ -295,6 +302,14 @@ public struct OpenAIAssistantMessage: Hashable, Codable, Sendable {
             reasoningDetails: reasoningDetails
         )
     }
+
+    public func encode(to encoder: Encoder) throws {
+        var container = encoder.container(keyedBy: CodingKeys.self)
+        try container.encode(role, forKey: .role)
+        try container.encodeIfPresent(content, forKey: .content)
+        try container.encodeIfPresent(toolCalls, forKey: .toolCalls)
+        // Exclude id, audio, reasoning, reasoningDetails - not part of request spec
+    }
 }
 
 public struct OpenAISystemMessage: Hashable, Codable, Sendable {
@@ -319,6 +334,13 @@ public struct OpenAISystemMessage: Hashable, Codable, Sendable {
         self.role = try container.decodeIfPresent(OpenAIRole.self, forKey: .role) ?? .system
         self.content = try container.decode(String.self, forKey: .content)
     }
+
+    public func encode(to encoder: Encoder) throws {
+        var container = encoder.container(keyedBy: CodingKeys.self)
+        try container.encode(role, forKey: .role)
+        try container.encode(content, forKey: .content)
+        // Exclude id - not part of OpenAI API spec
+    }
 }
 
 public struct OpenAIToolMessage: Hashable, Codable, Sendable {
@@ -351,6 +373,15 @@ public struct OpenAIToolMessage: Hashable, Codable, Sendable {
         self.toolCallId = try container.decode(String.self, forKey: .toolCallId)
         self.name = try container.decodeIfPresent(String.self, forKey: .name)
     }
+
+    public func encode(to encoder: Encoder) throws {
+        var container = encoder.container(keyedBy: CodingKeys.self)
+        try container.encode(role, forKey: .role)
+        try container.encode(content, forKey: .content)
+        try container.encode(toolCallId, forKey: .toolCallId)
+        try container.encodeIfPresent(name, forKey: .name)
+        // Exclude id - not part of OpenAI API spec
+    }
 }
 
 public enum OpenAIMessage: Hashable, Codable, Sendable {

Sources/AgentLayout/ChatProvider.swift

@@ -158,7 +158,7 @@ public class ChatProvider: ChatProviderProtocol {
         encoder.outputFormatting = .prettyPrinted
         let resultString: String
         if let data = try? encoder.encode(AnyEncodable(result)),
-           let jsonString = String(data: data, encoding: .utf8)
+            let jsonString = String(data: data, encoding: .utf8)
         {
             resultString = jsonString
         } else {
@@ -171,8 +171,8 @@ public class ChatProvider: ChatProviderProtocol {
             if let chat = self.chat {
                 for message in chat.messages.reversed() {
                     if case .openai(let openAIMsg) = message,
-                       case .assistant(let assistant) = openAIMsg,
-                       let toolCalls = assistant.toolCalls
+                        case .assistant(let assistant) = openAIMsg,
+                        let toolCalls = assistant.toolCalls
                     {
                         if let toolCall = toolCalls.first(where: { $0.id == id }) {
                             toolName = toolCall.function?.name
@@ -341,7 +341,8 @@ public class ChatProvider: ChatProviderProtocol {
 
     public func send(_ message: String) {
         guard generationTask == nil else { return }
-        guard var chat = chat, let currentSource = currentSource, let currentModel = currentModel else { return }
+        guard var chat = chat, let currentSource = currentSource, let currentModel = currentModel
+        else { return }
 
         let userMsg = Message.openai(.user(.init(content: message)))
         chat.messages.append(userMsg)
@@ -353,14 +354,19 @@ public class ChatProvider: ChatProviderProtocol {
             self?.scrollToBottom?()
         }
 
-        let source = currentSource
-        let model = currentModel
+        startGeneration(source: currentSource, model: currentModel, userMessage: message)
+    }
 
+    /// Internal method to start generation without adding a user message.
+    /// Used by both `send` and `regenerate`.
+    private func startGeneration(source: Source, model: Model, userMessage: String? = nil) {
         generationTask = Task { [weak self] in
             guard let self = self else { return }
             self.status = .loading
 
-            try? await self.sendMessage(message: message)
+            if let message = userMessage {
+                try? await self.sendMessage(message: message)
+            }
 
             do {
                 var messagesToSend = self.chat?.messages ?? []
@@ -493,7 +499,9 @@ public class ChatProvider: ChatProviderProtocol {
         guard generationTask == nil else { return }
         guard let chat = chat else { return }
         guard let index = chat.messages.firstIndex(where: { $0.id == messageId }) else { return }
+        guard let currentSource = currentSource, let currentModel = currentModel else { return }
 
+        // Find the user message content before the target message
         var userMessageContent: String? = nil
         for i in stride(from: index - 1, through: 0, by: -1) {
             if case .openai(let openAIMsg) = chat.messages[i],
@@ -504,11 +512,14 @@ public class ChatProvider: ChatProviderProtocol {
             }
         }
 
-        guard let content = userMessageContent else { return }
+        guard userMessageContent != nil else { return }
 
+        // Remove the target message and all subsequent messages
         self.chat?.messages.removeSubrange(index...)
         notifyMessageChange()
-        send(content)
+
+        // Start generation without adding a new user message
+        startGeneration(source: currentSource, model: currentModel)
     }
 
     public func cancel() {
@@ -624,4 +635,13 @@ public class ChatProvider: ChatProviderProtocol {
     public func updateSystemPrompt(_ newSystemPrompt: String?) {
         self.systemPrompt = newSystemPrompt
     }
+
+    /**
+        Regenerates the conversation starting at the given message.
+        This will remove all messages after the given message and regenerate the conversation from the given message.
+        - Parameter message: The message to start regenerating from.
+    */
+    public func regenerate(startsAt message: Message) async throws {
+
+    }
 }