366 lines
9 KiB
TypeScript
366 lines
9 KiB
TypeScript
class InfiniteScroller {
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readonly getIDFromOffset: (ID: string, offset: number) => Promise<string | undefined>;
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readonly getHTMLFromID: (ID: string) => Promise<HTMLElement>;
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readonly destroyFromID: (ID: string) => Promise<boolean>;
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readonly reachesBottom: () => void;
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private readonly minDist = 2000;
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private readonly fillDist = 3000;
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private readonly maxDist = 6000;
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HTMLElements: [HTMLElement, string][] = [];
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div: HTMLDivElement | null = null;
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timeout: ReturnType<typeof setTimeout> | null = null;
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beenloaded = false;
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scrollBottom = 0;
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scrollTop = 0;
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needsupdate = true;
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averageheight = 60;
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watchtime = false;
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changePromise: Promise<boolean> | undefined;
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scollDiv!: {scrollTop: number; scrollHeight: number; clientHeight: number};
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resetVars() {
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this.scrollTop = 0;
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this.scrollBottom = 0;
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this.averageheight = 60;
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this.watchtime = false;
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this.needsupdate = true;
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this.beenloaded = false;
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this.changePromise = undefined;
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if (this.timeout) {
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clearTimeout(this.timeout);
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this.timeout = null;
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}
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for (const thing of this.HTMLElements) {
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this.destroyFromID(thing[1]);
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}
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this.HTMLElements = [];
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}
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constructor(
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getIDFromOffset: InfiniteScroller["getIDFromOffset"],
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getHTMLFromID: InfiniteScroller["getHTMLFromID"],
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destroyFromID: InfiniteScroller["destroyFromID"],
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reachesBottom: InfiniteScroller["reachesBottom"] = () => {},
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) {
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this.getIDFromOffset = getIDFromOffset;
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this.getHTMLFromID = getHTMLFromID;
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this.destroyFromID = destroyFromID;
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this.reachesBottom = reachesBottom;
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}
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async getDiv(initialId: string): Promise<HTMLDivElement> {
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if (this.div) {
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throw new Error("Div already exists, exiting.");
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}
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this.resetVars();
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const scroll = document.createElement("div");
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scroll.classList.add("scroller");
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this.div = scroll;
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this.div.addEventListener("scroll", () => {
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this.checkscroll();
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if (this.scrollBottom < 5) {
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this.scrollBottom = 5;
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}
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if (this.timeout === null) {
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this.timeout = setTimeout(this.updatestuff.bind(this), 300);
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}
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this.watchForChange();
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});
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let oldheight = 0;
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new ResizeObserver(() => {
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this.checkscroll();
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const func = this.snapBottom();
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this.updatestuff();
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const change = oldheight - scroll.offsetHeight;
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if (change > 0 && this.div) {
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this.div.scrollTop += change;
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}
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oldheight = scroll.offsetHeight;
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this.watchForChange();
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func();
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}).observe(scroll);
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new ResizeObserver(this.watchForChange.bind(this)).observe(scroll);
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await this.firstElement(initialId);
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this.updatestuff();
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await this.watchForChange().then(() => {
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this.updatestuff();
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this.beenloaded = true;
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});
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return scroll;
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}
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checkscroll(): void {
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if (this.beenloaded && this.div && !document.body.contains(this.div)) {
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console.warn("not in document");
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this.div = null;
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}
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}
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async updatestuff(): Promise<void> {
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this.timeout = null;
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if (!this.div) return;
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this.scrollBottom = this.div.scrollHeight - this.div.scrollTop - this.div.clientHeight;
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this.averageheight = this.div.scrollHeight / this.HTMLElements.length;
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if (this.averageheight < 10) {
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this.averageheight = 60;
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}
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this.scrollTop = this.div.scrollTop;
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if (!this.scrollBottom && !(await this.watchForChange())) {
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this.reachesBottom();
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}
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if (!this.scrollTop) {
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await this.watchForChange();
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}
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this.needsupdate = false;
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}
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async firstElement(id: string): Promise<void> {
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if (!this.div) return;
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const html = await this.getHTMLFromID(id);
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this.div.appendChild(html);
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this.HTMLElements.push([html, id]);
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}
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async addedBottom(): Promise<void> {
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await this.updatestuff();
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const func = this.snapBottom();
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if (this.changePromise) {
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while (this.changePromise) {
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await new Promise((res) => setTimeout(res, 30));
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}
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} else {
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await this.watchForChange();
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}
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func();
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}
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snapBottom(): () => void {
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const scrollBottom = this.scrollBottom;
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return () => {
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if (this.div && scrollBottom < 4) {
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this.div.scrollTop = this.div.scrollHeight;
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}
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};
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}
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private async watchForTop(already = false, fragment = new DocumentFragment()): Promise<boolean> {
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if (!this.div) return false;
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try {
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let again = false;
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if (this.scrollTop < (already ? this.fillDist : this.minDist)) {
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let nextid: string | undefined;
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const firstelm = this.HTMLElements.at(0);
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if (firstelm) {
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const previd = firstelm[1];
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nextid = await this.getIDFromOffset(previd, 1);
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}
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if (nextid) {
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const html = await this.getHTMLFromID(nextid);
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if (!html) {
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this.destroyFromID(nextid);
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return false;
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}
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again = true;
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fragment.prepend(html);
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this.HTMLElements.unshift([html, nextid]);
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this.scrollTop += this.averageheight;
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}
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}
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if (this.scrollTop > this.maxDist) {
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const html = this.HTMLElements.shift();
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if (html) {
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again = true;
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await this.destroyFromID(html[1]);
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this.scrollTop -= this.averageheight;
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}
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}
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if (again) {
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await this.watchForTop(true, fragment);
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}
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return again;
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} finally {
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if (!already) {
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if (this.div.scrollTop === 0) {
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this.scrollTop = 1;
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this.div.scrollTop = 10;
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}
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this.div.prepend(fragment, fragment);
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}
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}
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}
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async watchForBottom(already = false, fragment = new DocumentFragment()): Promise<boolean> {
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let func: Function | undefined;
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if (!already) func = this.snapBottom();
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if (!this.div) return false;
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try {
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let again = false;
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const scrollBottom = this.scrollBottom;
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if (scrollBottom < (already ? this.fillDist : this.minDist)) {
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let nextid: string | undefined;
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const lastelm = this.HTMLElements.at(-1);
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if (lastelm) {
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const previd = lastelm[1];
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nextid = await this.getIDFromOffset(previd, -1);
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}
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if (nextid) {
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again = true;
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const html = await this.getHTMLFromID(nextid);
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fragment.appendChild(html);
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this.HTMLElements.push([html, nextid]);
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this.scrollBottom += this.averageheight;
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}
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}
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if (scrollBottom > this.maxDist) {
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const html = this.HTMLElements.pop();
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if (html) {
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await this.destroyFromID(html[1]);
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this.scrollBottom -= this.averageheight;
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again = true;
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}
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}
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if (again) {
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await this.watchForBottom(true, fragment);
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}
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return again;
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} finally {
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if (!already) {
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this.div.append(fragment);
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if (func) {
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func();
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}
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}
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}
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}
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async watchForChange(stop = false): Promise<boolean> {
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if (stop == true) {
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let prom = this.changePromise;
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while (this.changePromise) {
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prom = this.changePromise;
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await this.changePromise;
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if (prom === this.changePromise) {
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this.changePromise = undefined;
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break;
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}
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}
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}
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if (this.changePromise) {
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this.watchtime = true;
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return await this.changePromise;
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} else {
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this.watchtime = false;
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}
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this.changePromise = new Promise<boolean>(async (res) => {
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//debugger;
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try {
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if (!this.div) {
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res(false);
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}
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const out = (await Promise.allSettled([this.watchForTop(), this.watchForBottom()])) as {
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value: boolean;
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}[];
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const changed = out[0].value || out[1].value;
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if (this.timeout === null && changed) {
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this.timeout = setTimeout(this.updatestuff.bind(this), 300);
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}
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res(Boolean(changed));
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} catch (e) {
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console.error(e);
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res(false);
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} finally {
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if (stop === true) {
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this.changePromise = undefined;
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return;
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}
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setTimeout(() => {
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this.changePromise = undefined;
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if (this.watchtime) {
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this.watchForChange();
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}
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}, 300);
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}
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});
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return await this.changePromise;
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}
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async focus(id: string, flash = true, sec = false): Promise<void> {
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let element: HTMLElement | undefined;
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for (const thing of this.HTMLElements) {
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if (thing[1] === id) {
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element = thing[0];
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}
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}
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if (sec && element) {
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if (flash) {
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element.scrollIntoView({
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behavior: "smooth",
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inline: "center",
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block: "center",
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});
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await new Promise((resolve) => {
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setTimeout(resolve, 1000);
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});
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element.classList.remove("jumped");
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await new Promise((resolve) => {
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setTimeout(resolve, 100);
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});
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element.classList.add("jumped");
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} else {
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element.scrollIntoView({
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block: "center",
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});
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}
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} else if (!sec) {
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this.resetVars();
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//TODO may be a redundant loop, not 100% sure :P
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for (const thing of this.HTMLElements) {
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await this.destroyFromID(thing[1]);
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}
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this.HTMLElements = [];
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await this.firstElement(id);
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this.updatestuff();
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await this.watchForChange(true);
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this.changePromise = new Promise<boolean>((resolve) => {
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setTimeout(() => {
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this.changePromise = undefined;
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resolve(true);
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}, 1000);
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});
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await this.focus(id, !element, true);
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} else {
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console.warn("elm not exist");
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}
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}
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async delete(): Promise<void> {
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if (this.div) {
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this.div.remove();
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this.div = null;
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}
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this.resetVars();
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try {
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for (const thing of this.HTMLElements) {
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await this.destroyFromID(thing[1]);
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}
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} catch (e) {
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console.error(e);
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}
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this.HTMLElements = [];
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if (this.timeout) {
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clearTimeout(this.timeout);
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}
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}
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}
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export {InfiniteScroller};
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