refactor: replace focusedIndex with activeChildId

- Replace focusedIndex integer with activeChildId string in messages schema
- Add migration to convert existing data and drop focused_index column
- Add  hooks for providers.updatedAt and messageParts.lastUpdatedAt
- Add file size column to files table
- Update message navigation to use child ID-based lookup
- Simplify delete logic by removing focusedIndex math
- Fix file delete endpoint filename ([id[ -> [id])

app/composables/useChat.ts

@@ -40,7 +40,10 @@ export const useChat = async (topicId: MaybeRef<string>, connect = true) => {
 
     let sse: EventSource | undefined;
 
-    const textDeltaBuffer: Map<string, Map<string, string>> = new Map();
+    const textDeltaBuffer: Map<string, Map<string, {
+        content: string;
+        lastUpdatedAt: string;
+    }>> = new Map();
     let flushTimeout: ReturnType<typeof setTimeout> | undefined;
     let flushCbs: Set<() => void> = new Set();
 
@@ -54,7 +57,8 @@ export const useChat = async (topicId: MaybeRef<string>, connect = true) => {
             for (const [partId, content] of parts) {
                 const part = msg.parts?.find(p => p.id === partId);
                 if (part) {
-                    part.content += content;
+                    part.content += content.content;
+                    part.lastUpdatedAt = new Date(content.lastUpdatedAt);
                 }
             }
         }
@@ -132,8 +136,8 @@ export const useChat = async (topicId: MaybeRef<string>, connect = true) => {
                     textDeltaBuffer.set(payload.messageId, new Map());
                 }
                 const messageBuffer = textDeltaBuffer.get(payload.messageId)!;
-                const existing = messageBuffer.get(payload.partId) || '';
-                messageBuffer.set(payload.partId, existing + payload.content);
+                const existing = messageBuffer.get(payload.partId)?.content || '';
+                messageBuffer.set(payload.partId, { content: existing + payload.content, lastUpdatedAt: payload.lastUpdatedAt });
 
                 scheduleFlush();
                 break;
@@ -145,6 +149,7 @@ export const useChat = async (topicId: MaybeRef<string>, connect = true) => {
                 if (part) {
                     nextFlush(() => {
                         part.content = payload.content;
+                        part.lastUpdatedAt = payload.lastUpdatedAt;
                         part.finished = true;
                     });
                 }
@@ -328,7 +333,7 @@ export const useChat = async (topicId: MaybeRef<string>, connect = true) => {
                             generation: null,
                             parentMessageId: null,
                             generationId: null,
-                            focusedIndex: null,
+                            activeChildId: null,
                             deleted: null,
                             createdAt: new Date(),
                             updatedAt: new Date(),
@@ -457,11 +462,46 @@ export const useChat = async (topicId: MaybeRef<string>, connect = true) => {
         );
     }
 
+    const deleteMessagesFocusedDescendant = async (messageId: string): Promise<Result<void, Error>> => {
+        if (!data.value) return Err(new Error('No data'));
+
+        const msg = data.value.messages.find(m => m.id === messageId);
+        if (!msg) return Err(new Error('Message not found'));
+
+        const previousMessages = data.value!.messages;
+
+        const res = await $fetch(`/api/messages/${messageId}`, {
+            method: 'DELETE',
+            onRequest() {
+                if (!msg.activeChildId && (msg.parentMessageId === null || msg.parentMessageId === undefined)) {
+                    msg.deleted = true;
+                    return;
+                }
+
+                const parent = data.value!.messages.find(m => m.id === msg.parentMessageId);
+                data.value!.messages = data.value!.messages.filter(m => m.id !== msg.id);
+                if (parent?.deleted) {
+                    data.value!.messages = data.value!.messages.filter(m => m.id !== parent.id);
+                }
+            },
+            onResponseError() {
+                data.value!.messages = previousMessages;
+            },
+        });
+
+        if (!res.ok) {
+            return Err(new Error('Failed to delete message'));
+        }
+
+        return Ok(undefined);
+    }
+
     return {
         topic,
         sendMessage,
         startGeneration,
         regenerateMessage,
-        patchMessageLocally
+        patchMessageLocally,
+        deleteMessagesFocusedDescendant
     };
 }