Locked changes to a chat while an answer is being written (#1058)

app/MindWork AI Studio/Chat/ChatBlockActions.cs

@@ -0,0 +1,105 @@
+using System.Diagnostics.CodeAnalysis;
+
+namespace AIStudio.Chat;
+
+/// <summary>
+/// Changes the messages of a chat on behalf of the user, but never while an answer is being written for it.
+/// </summary>
+/// <remarks>
+/// While an answer is being written, the AI job holds the very same thread as the chat: it writes into
+/// the answer, and it stores the whole conversation every few seconds. A message the user removed in
+/// the meantime does not come back, but the job goes on writing an answer nobody sees, and the chat
+/// stays locked until that answer is complete. Removing the answer and sending another message would
+/// leave two answers being written for one chat. Changing older messages is no better: the job stores
+/// the conversation on another thread and could read it in the middle of the change.<br/><br/>
+///
+/// That is why every message is locked while an answer is being written, not only the answer itself.
+/// Stopping the answer unlocks the chat right away.
+/// </remarks>
+/// <param name="isAnswerBeingWritten">Whether an answer is being written for the chat with the given ID right now.</param>
+public sealed class ChatBlockActions(Func<Guid, bool> isAnswerBeingWritten)
+{
+    /// <summary>
+    /// Whether the user may change the messages of the given chat right now.
+    /// </summary>
+    /// <param name="chat">The chat, or null when there is none yet.</param>
+    /// <returns>True when there is a chat and no answer is being written for it.</returns>
+    public bool AreAllowed([NotNullWhen(true)] ChatThread? chat) => chat is not null && !isAnswerBeingWritten(chat.ChatId);
+
+    /// <summary>
+    /// Removes a message, together with the hidden prompt an answer was written for.
+    /// </summary>
+    /// <param name="chat">The chat.</param>
+    /// <param name="content">The content of the message to remove.</param>
+    /// <returns>True when the message was removed.</returns>
+    public bool TryRemove([NotNullWhen(true)] ChatThread? chat, IContent content)
+    {
+        if (!this.AreAllowed(chat) || !Holds(chat, content))
+            return false;
+
+        chat.Remove(content);
+        return true;
+    }
+
+    /// <summary>
+    /// Removes an answer so that it can be written anew for the same question.
+    /// </summary>
+    /// <param name="chat">The chat.</param>
+    /// <param name="answer">The content of the answer to remove.</param>
+    /// <returns>True when the answer was removed.</returns>
+    public bool TryRemoveForRegenerate([NotNullWhen(true)] ChatThread? chat, IContent answer)
+    {
+        if (!this.AreAllowed(chat) || !Holds(chat, answer))
+            return false;
+
+        chat.Remove(answer, removeForRegenerate: true);
+        return true;
+    }
+
+    /// <summary>
+    /// Rolls the chat back, so that the given answer becomes its last message.
+    /// </summary>
+    /// <remarks>
+    /// What the rollback removes and what it keeps is documented at ChatThread.RollBackTo.
+    /// </remarks>
+    /// <param name="chat">The chat.</param>
+    /// <param name="answer">The content of the answer to keep as the last message.</param>
+    /// <returns>True when later messages were removed.</returns>
+    public bool TryRollBack([NotNullWhen(true)] ChatThread? chat, IContent answer) => this.AreAllowed(chat) && chat.RollBackTo(answer);
+
+    /// <summary>
+    /// Makes the last question the draft again, and removes the answer to it.
+    /// </summary>
+    /// <param name="chat">The chat.</param>
+    /// <param name="question">The content of the question to edit.</param>
+    /// <returns>True when the question became the draft.</returns>
+    public bool TryEditLastUserBlock([NotNullWhen(true)] ChatThread? chat, IContent question)
+    {
+        if (!this.AreAllowed(chat) || question is not ContentText || !Holds(chat, question))
+            return false;
+
+        var lastContent = chat.Blocks.Last().Content;
+        chat.RemoveForEditing(question);
+        if (lastContent is not null)
+            chat.Remove(lastContent);
+
+        return true;
+    }
+
+    /// <summary>
+    /// Makes a question without an answer the draft again.
+    /// </summary>
+    /// <param name="chat">The chat.</param>
+    /// <param name="question">The content of the question to edit.</param>
+    /// <returns>True when the question became the draft.</returns>
+    public bool TryEditLastBlock([NotNullWhen(true)] ChatThread? chat, IContent question)
+    {
+        if (!this.AreAllowed(chat) || question is not ContentText || !Holds(chat, question))
+            return false;
+
+        chat.RemoveForEditing(question);
+        return true;
+    }
+
+    private static bool Holds(ChatThread chat, IContent content) => chat.Blocks.Any(block => block.Content == content);
+}

app/MindWork AI Studio/Chat/ContentBlockComponent.razor

@@ -55,31 +55,31 @@
                 @if (this.IsSecondToLastBlock && this.Role is ChatRole.USER && this.EditLastUserBlockFunc is not null)
                 {
                     <MudTooltip Text="@T("Edit")" Placement="Placement.Bottom">
-                        <MudIconButton Icon="@Icons.Material.Filled.Edit" Color="Color.Default" OnClick="@this.EditLastUserBlock"/>
+                        <MudIconButton Icon="@Icons.Material.Filled.Edit" Color="Color.Default" Disabled="@(!this.BlockActionsEnabled())" OnClick="@this.EditLastUserBlock"/>
                     </MudTooltip>
                 }
                 @if (this.IsLastContentBlock && this.Role is ChatRole.USER && this.EditLastBlockFunc is not null)
                 {
                     <MudTooltip Text="@T("Edit")" Placement="Placement.Bottom">
-                        <MudIconButton Icon="@Icons.Material.Filled.Edit" Color="Color.Default" OnClick="@this.EditLastBlock"/>
+                        <MudIconButton Icon="@Icons.Material.Filled.Edit" Color="Color.Default" Disabled="@(!this.BlockActionsEnabled())" OnClick="@this.EditLastBlock"/>
                     </MudTooltip>
                 }
                 @if (this.IsLastContentBlock && this.Role is ChatRole.AI && this.RegenerateFunc is not null)
                 {
                     <MudTooltip Text="@T("Regenerate")" Placement="Placement.Bottom">
-                        <MudIconButton Icon="@Icons.Material.Filled.Recycling" Color="Color.Default" Disabled="@(!this.RegenerateEnabled())" OnClick="@this.RegenerateBlock"/>
+                        <MudIconButton Icon="@Icons.Material.Filled.Recycling" Color="Color.Default" Disabled="@(!this.BlockActionsEnabled() || !this.RegenerateEnabled())" OnClick="@this.RegenerateBlock"/>
                     </MudTooltip>
                 }
                 @if (!this.IsLastContentBlock && this.Role is ChatRole.AI && this.RollbackFunc is not null)
                 {
                     <MudTooltip Text="@T("Roll back to this response")" Placement="Placement.Bottom">
-                        <MudIconButton Icon="@Icons.Material.Filled.Restore" Color="Color.Default" Disabled="@(!this.RollbackEnabled())" OnClick="@this.RollbackBlock"/>
+                        <MudIconButton Icon="@Icons.Material.Filled.Restore" Color="Color.Default" Disabled="@(!this.BlockActionsEnabled())" OnClick="@this.RollbackBlock"/>
                     </MudTooltip>
                 }
                 @if (this.RemoveBlockFunc is not null)
                 {
                     <MudTooltip Text="@T("Removes this block")" Placement="Placement.Bottom">
-                        <MudIconButton Icon="@Icons.Material.Filled.Delete" Color="Color.Error" OnClick="@this.RemoveBlock"/>
+                        <MudIconButton Icon="@Icons.Material.Filled.Delete" Color="Color.Error" Disabled="@(!this.BlockActionsEnabled())" OnClick="@this.RemoveBlock"/>
                     </MudTooltip>
                 }
 

app/MindWork AI Studio/Chat/ContentBlockComponent.razor.cs

@@ -89,8 +89,15 @@ public partial class ContentBlockComponent : MSGComponentBase
     [Parameter]
     public Func<bool> RegenerateEnabled { get; set; } = () => false;
 
+    /// <summary>
+    /// Whether the user may change the messages of the chat right now, i.e., remove, edit, regenerate, or roll back.
+    /// </summary>
+    /// <remarks>
+    /// The chat answers false while an answer is being written for it, since every change to a message
+    /// would collide with the answer. Whoever passes none of these actions needs no answer here.
+    /// </remarks>
     [Parameter]
-    public Func<bool> RollbackEnabled { get; set; } = () => false;
+    public Func<bool> BlockActionsEnabled { get; set; } = () => false;
 
     /// <summary>
     /// What the export offers, used both as the label of the export button and as the title of
@@ -321,6 +328,7 @@ public partial class ContentBlockComponent : MSGComponentBase
         hash.Add(this.HideContent);
         hash.Add(this.SettingsManager.IsDarkMode);
         hash.Add(this.RegenerateEnabled());
+        hash.Add(this.BlockActionsEnabled());
         hash.Add(this.Content.InitialRemoteWait);
         hash.Add(this.Content.IsStreaming);
         hash.Add(this.Content.FileAttachments.Count);
@@ -733,7 +741,7 @@ public partial class ContentBlockComponent : MSGComponentBase
     
     private async Task RemoveBlock()
     {
-        if (this.RemoveBlockFunc is null)
+        if (this.RemoveBlockFunc is null || !this.BlockActionsEnabled())
             return;
         
         var remove = await this.DialogService.ShowMessageBox(
@@ -793,7 +801,7 @@ public partial class ContentBlockComponent : MSGComponentBase
     
     private async Task RegenerateBlock()
     {
-        if (this.RegenerateFunc is null)
+        if (this.RegenerateFunc is null || !this.BlockActionsEnabled())
             return;
         
         if(this.Role is not ChatRole.AI)
@@ -811,7 +819,7 @@ public partial class ContentBlockComponent : MSGComponentBase
 
     private async Task RollbackBlock()
     {
-        if (this.RollbackFunc is null || this.Role is not ChatRole.AI || !this.RollbackEnabled())
+        if (this.RollbackFunc is null || this.Role is not ChatRole.AI || !this.BlockActionsEnabled())
             return;
 
         var rollback = await this.DialogService.ShowMessageBox(
@@ -826,7 +834,7 @@ public partial class ContentBlockComponent : MSGComponentBase
     
     private async Task EditLastBlock()
     {
-        if (this.EditLastBlockFunc is null)
+        if (this.EditLastBlockFunc is null || !this.BlockActionsEnabled())
             return;
         
         if(this.Role is not ChatRole.USER)
@@ -837,7 +845,7 @@ public partial class ContentBlockComponent : MSGComponentBase
     
     private async Task EditLastUserBlock()
     {
-        if (this.EditLastUserBlockFunc is null)
+        if (this.EditLastUserBlockFunc is null || !this.BlockActionsEnabled())
             return;
         
         if(this.Role is not ChatRole.USER)