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31dd200 | 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 | import { AUTO_SCROLL_AT_BOTTOM_THRESHOLD, AUTO_SCROLL_INTERVAL } from '$lib/constants/auto-scroll';
export interface AutoScrollOptions {
/** Whether auto-scroll is disabled globally (e.g., from settings) */
disabled?: boolean;
}
/**
* Creates an auto-scroll controller for a scrollable container.
*
* Features:
* - Auto-scrolls to bottom during streaming/loading
* - Stops auto-scroll when user manually scrolls up
* - Resumes auto-scroll when user scrolls back to bottom
*/
export class AutoScrollController {
private _autoScrollEnabled = $state(true);
private _userScrolledUp = $state(false);
private _lastScrollTop = $state(0);
private _scrollInterval: ReturnType<typeof setInterval> | undefined;
private _scrollTimeout: ReturnType<typeof setTimeout> | undefined;
private _container: HTMLElement | undefined;
private _disabled: boolean;
constructor(options: AutoScrollOptions = {}) {
this._disabled = options.disabled ?? false;
}
get autoScrollEnabled(): boolean {
return this._autoScrollEnabled;
}
get userScrolledUp(): boolean {
return this._userScrolledUp;
}
/**
* Binds the controller to a scrollable container element.
*/
setContainer(container: HTMLElement | undefined): void {
this._container = container;
}
/**
* Updates the disabled state.
*/
setDisabled(disabled: boolean): void {
this._disabled = disabled;
if (disabled) {
this._autoScrollEnabled = false;
this.stopInterval();
}
}
/**
* Handles scroll events to detect user scroll direction and toggle auto-scroll.
*/
handleScroll(): void {
if (this._disabled || !this._container) return;
const { scrollTop, scrollHeight, clientHeight } = this._container;
const distanceFromBottom = scrollHeight - scrollTop - clientHeight;
const isAtBottom = distanceFromBottom < AUTO_SCROLL_AT_BOTTOM_THRESHOLD;
if (scrollTop < this._lastScrollTop && !isAtBottom) {
this._userScrolledUp = true;
this._autoScrollEnabled = false;
} else if (isAtBottom && this._userScrolledUp) {
this._userScrolledUp = false;
this._autoScrollEnabled = true;
}
if (this._scrollTimeout) {
clearTimeout(this._scrollTimeout);
}
this._scrollTimeout = setTimeout(() => {
if (isAtBottom) {
this._userScrolledUp = false;
this._autoScrollEnabled = true;
}
}, AUTO_SCROLL_INTERVAL);
this._lastScrollTop = scrollTop;
}
/**
* Scrolls the container to the bottom.
*/
scrollToBottom(behavior: ScrollBehavior = 'smooth'): void {
if (this._disabled || !this._container) return;
this._container.scrollTo({
top: this._container.scrollHeight,
behavior
});
}
/**
* Enables auto-scroll (e.g., when user sends a message).
*/
enable(): void {
if (this._disabled) return;
this._userScrolledUp = false;
this._autoScrollEnabled = true;
}
/**
* Starts the auto-scroll interval for continuous scrolling during streaming.
*/
startInterval(): void {
if (this._disabled || this._scrollInterval) return;
this._scrollInterval = setInterval(() => {
this.scrollToBottom();
}, AUTO_SCROLL_INTERVAL);
}
/**
* Stops the auto-scroll interval.
*/
stopInterval(): void {
if (this._scrollInterval) {
clearInterval(this._scrollInterval);
this._scrollInterval = undefined;
}
}
/**
* Updates the auto-scroll interval based on streaming state.
* Call this in a $effect to automatically manage the interval.
*/
updateInterval(isStreaming: boolean): void {
if (this._disabled) {
this.stopInterval();
return;
}
if (isStreaming && this._autoScrollEnabled) {
if (!this._scrollInterval) {
this.startInterval();
}
} else {
this.stopInterval();
}
}
/**
* Cleans up resources. Call this in onDestroy or when the component unmounts.
*/
destroy(): void {
this.stopInterval();
if (this._scrollTimeout) {
clearTimeout(this._scrollTimeout);
this._scrollTimeout = undefined;
}
}
}
/**
* Creates a new AutoScrollController instance.
*/
export function createAutoScrollController(options: AutoScrollOptions = {}): AutoScrollController {
return new AutoScrollController(options);
}
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