Fix (beta): convert chat component to signal-backed (#13152)

src-ui/src/app/components/chat/chat/chat.component.ts

@@ -1,4 +1,11 @@
-import { Component, ElementRef, inject, OnInit, ViewChild } from '@angular/core'
+import {
+  Component,
+  ElementRef,
+  inject,
+  OnInit,
+  signal,
+  ViewChild,
+} from '@angular/core'
 import { FormsModule, ReactiveFormsModule } from '@angular/forms'
 import { NavigationEnd, Router, RouterModule } from '@angular/router'
 import { NgbDropdownModule } from '@ng-bootstrap/ng-bootstrap'
@@ -23,10 +30,10 @@ import {
   styleUrl: './chat.component.scss',
 })
 export class ChatComponent implements OnInit {
-  public messages: ChatMessage[] = []
-  public loading = false
-  public input: string = ''
-  public documentId!: number
+  readonly messages = signal<ChatMessage[]>([])
+  readonly loading = signal(false)
+  readonly input = signal('')
+  readonly documentId = signal<number>(undefined)
 
   private chatService: ChatService = inject(ChatService)
   private router: Router = inject(Router)
@@ -38,7 +45,7 @@ export class ChatComponent implements OnInit {
   private typewriterActive = false
 
   public get placeholder(): string {
-    return this.documentId
+    return this.documentId()
       ? $localize`Ask a question about this document...`
       : $localize`Ask a question about a document...`
   }
@@ -57,14 +64,14 @@ export class ChatComponent implements OnInit {
 
   private updateDocumentId(url: string): void {
     const docIdRe = url.match(/^\/documents\/(\d+)/)
-    this.documentId = docIdRe ? +docIdRe[1] : undefined
+    this.documentId.set(docIdRe ? +docIdRe[1] : undefined)
   }
 
   sendMessage(): void {
-    if (!this.input.trim()) return
+    if (!this.input().trim()) return
 
-    const userMessage: ChatMessage = { role: 'user', content: this.input }
-    this.messages.push(userMessage)
+    const userMessage: ChatMessage = { role: 'user', content: this.input() }
+    this.messages.update((messages) => [...messages, userMessage])
     this.scrollToBottom()
 
     const assistantMessage: ChatMessage = {
@@ -72,12 +79,12 @@ export class ChatComponent implements OnInit {
       content: '',
       isStreaming: true,
     }
-    this.messages.push(assistantMessage)
-    this.loading = true
+    this.messages.update((messages) => [...messages, assistantMessage])
+    this.loading.set(true)
 
     let lastVisibleContent = ''
 
-    this.chatService.streamChat(this.documentId, this.input).subscribe({
+    this.chatService.streamChat(this.documentId(), this.input()).subscribe({
       next: (chunk) => {
         const nextResponse = parseChatResponse(chunk)
 
@@ -93,26 +100,30 @@ export class ChatComponent implements OnInit {
         }
 
         assistantMessage.references = nextResponse.references
+        this.notifyMessagesChanged()
       },
       error: () => {
         assistantMessage.content += '\n\n⚠️ Error receiving response.'
         assistantMessage.isStreaming = false
-        this.loading = false
+        this.notifyMessagesChanged()
+        this.loading.set(false)
       },
       complete: () => {
         assistantMessage.isStreaming = false
-        this.loading = false
+        this.notifyMessagesChanged()
+        this.loading.set(false)
         this.scrollToBottom()
       },
     })
 
-    this.input = ''
+    this.input.set('')
   }
 
   private resetTypewriter(message: ChatMessage, content: string): void {
     this.typewriterBuffer = []
     this.typewriterActive = false
     message.content = content
+    this.notifyMessagesChanged()
     this.scrollToBottom()
   }
 
@@ -135,11 +146,16 @@ export class ChatComponent implements OnInit {
 
     const nextChar = this.typewriterBuffer.shift()
     message.content += nextChar
+    this.notifyMessagesChanged()
     this.scrollToBottom()
 
     setTimeout(() => this.playTypewriter(message), 10) // 10ms per character
   }
 
+  private notifyMessagesChanged(): void {
+    this.messages.update((messages) => [...messages])
+  }
+
   private scrollToBottom(): void {
     setTimeout(() => {
       this.scrollAnchor?.nativeElement?.scrollIntoView({ behavior: 'smooth' })