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* Copyright (c) Siemens 2016 - 2026
* SPDX-License-Identifier: MIT
*/
import { isPlatformBrowser } from '@angular/common';
import {
AfterContentInit,
Component,
effect,
ElementRef,
input,
OnDestroy,
PLATFORM_ID,
viewChild,
inject
} from '@angular/core';
/**
* A declarative container component for displaying a chat interface with automatic scroll-to-bottom behavior.
*
* This component provides the layout and styling for a chat interface, managing scrolling behavior
* to keep the newest messages visible while respecting user scrolling actions. It automatically
* scrolls to the bottom when new content is added, unless the user has scrolled up to view older messages.
*
* Use via content projection:
* - Default content: Chat messages displayed in the scrollable messages container or a welcome screen (empty state).
* - `si-inline-notification` selector: Notification component displayed above the input area
* - `si-chat-input` or `[siChatContainerInput]` selector: Input controls for composing messages
*
* @see {@link SiChatInputComponent} for the chat input wrapper component
* @see {@link SiChatContainerInputDirective} for other input controls to slot in
* @see {@link SiAiMessageComponent} for AI messages to slot in
* @see {@link SiUserMessageComponent} for user messages (in AI chats) to slot in
* @see {@link SiChatMessageComponent} for the chat message wrapper component to slot in other messages
*
* @experimental
*/
@Component({
selector: 'si-chat-container',
templateUrl: './si-chat-container.component.html',
styleUrl: './si-chat-container.component.scss',
host: {
class: 'd-flex si-layout-inner flex-grow-1 flex-column h-100 w-100',
'[class]': 'colorVariant()'
}
})
export class SiChatContainerComponent implements AfterContentInit, OnDestroy {
private readonly messagesContainer = viewChild<ElementRef<HTMLDivElement>>('messagesContainer');
private readonly platformId = inject(PLATFORM_ID);
private isUserAtBottom = true;
private scrollTimeout: ReturnType<typeof setTimeout> | undefined;
private lastScrollTime = 0;
private pendingScroll = false;
private scrollDebounceMs = 7; // ~144fps
private resizeObserver: ResizeObserver | undefined;
private contentObserver: MutationObserver | undefined;
/**
* The color variant to apply to the container.
* @defaultValue 'base-0'
*/
readonly colorVariant = input<string>('base-0');
/**
* Disables automatic scrolling to the bottom when new content is added.
* @defaultValue false
*/
readonly noAutoScroll = input(false, {
transform: (value: boolean | string) => value === '' || value === true
});
constructor() {
effect(() => {
if (this.messagesContainer()) {
this.setupResizeObserver();
this.setupContentObserver();
}
});
}
ngAfterContentInit(): void {
this.scrollToBottomDuringStreaming();
}
ngOnDestroy(): void {
Iif (this.scrollTimeout) {
clearTimeout(this.scrollTimeout);
}
if (this.resizeObserver) {
this.resizeObserver.disconnect();
}
if (this.contentObserver) {
this.contentObserver.disconnect();
}
}
private scrollToBottomDuringStreaming(): void {
Iif (this.noAutoScroll() || !this.isUserAtBottom) {
return;
}
const container = this.messagesContainer();
Iif (!container) {
return;
}
const element = container.nativeElement;
element.scrollTop = element.scrollHeight;
}
private debouncedScrollToBottom(): void {
const now = Date.now();
const timeSinceLastScroll = now - this.lastScrollTime;
if (timeSinceLastScroll >= this.scrollDebounceMs) {
this.lastScrollTime = now;
this.scrollToBottomDuringStreaming();
this.pendingScroll = false;
} else {
this.pendingScroll = true;
}
Iif (this.scrollTimeout) {
clearTimeout(this.scrollTimeout);
}
this.scrollTimeout = setTimeout(() => {
Iif (this.pendingScroll) {
this.lastScrollTime = Date.now();
this.scrollToBottomDuringStreaming();
this.pendingScroll = false;
}
}, this.scrollDebounceMs);
}
private setupResizeObserver(): void {
Iif (!isPlatformBrowser(this.platformId)) {
return;
}
const container = this.messagesContainer();
Iif (!container || this.resizeObserver) {
return;
}
this.resizeObserver = new ResizeObserver(() => {
this.debouncedScrollToBottom();
});
this.resizeObserver.observe(container.nativeElement);
}
private setupContentObserver(): void {
Iif (!isPlatformBrowser(this.platformId)) {
return;
}
const container = this.messagesContainer();
Iif (!container || this.contentObserver) {
return;
}
this.contentObserver = new MutationObserver(() => {
this.debouncedScrollToBottom();
});
this.contentObserver.observe(container.nativeElement, {
childList: true,
subtree: true,
characterData: true
});
}
private checkIfUserAtBottom(): void {
const container = this.messagesContainer();
Iif (!container) {
return;
}
const element = container.nativeElement;
const threshold = 100;
this.isUserAtBottom =
element.scrollHeight - element.scrollTop - element.clientHeight < threshold;
}
protected onScroll(): void {
this.checkIfUserAtBottom();
}
/**
* Scrolls to the bottom of the messages container immediately.
* This method forces a scroll even if the user has scrolled up.
*/
public scrollToBottom(): void {
this.isUserAtBottom = true;
this.scrollToBottomDuringStreaming();
}
/**
* Scrolls to the top of the messages container immediately.
*/
public scrollToTop(): void {
const container = this.messagesContainer();
Iif (!container) {
return;
}
const element = container.nativeElement;
element.scrollTop = 0;
this.isUserAtBottom = false;
}
/**
* Focuses the messages container element.
*/
public focus(): void {
const container = this.messagesContainer();
container?.nativeElement.focus();
}
}
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