refactor: introduce ActivePageTimer to help to do partial page refresh (#38372)

Before, the logic is already there for "pull merge box".

After, the logic is extracted into a general class ActivePageTimer and
will help more pages (including #38329)

web_src/js/features/common-fetch-action.ts

@@ -1,6 +1,6 @@
 import {GET, request} from '../modules/fetch.ts';
 import {hideToastsAll, showErrorToast} from '../modules/toast.ts';
-import {addDelegatedEventListener, createElementFromHTML} from '../utils/dom.ts';
+import {activePageTimerRefresh, addDelegatedEventListener, createElementFromHTML} from '../utils/dom.ts';
 import {errorMessage, errorName} from '../modules/errors.ts';
 import {confirmModal, createConfirmModal} from './comp/ConfirmModal.ts';
 import {ignoreAreYouSure} from '../vendor/jquery.are-you-sure.ts';
@@ -330,17 +330,10 @@ function initFetchActionTriggerEvery(el: HTMLElement, trigger: string) {
 
   const num = parseInt(match[1], 10), unit = match[2];
   const intervalMs = unit === 's' ? num * 1000 : num;
-  const fn = async () => {
-    try {
-      await performFetchActionTrigger(el, 'every');
-    } finally {
-      // only continue if the element is still in the document
-      if (document.contains(el)) {
-        setTimeout(fn, intervalMs);
-      }
-    }
-  };
-  setTimeout(fn, intervalMs);
+  activePageTimerRefresh({
+    interval: () => document.contains(el) ? intervalMs : 0, // only continue if the element is still in the document
+    async callback() { await performFetchActionTrigger(el, 'every') },
+  });
 }
 
 function initFetchActionTrigger(el: HTMLElement) {

web_src/js/features/repo-issue-pull.ts

@@ -1,7 +1,7 @@
 import {createApp} from 'vue';
 import {GET} from '../modules/fetch.ts';
 import {fomanticQuery} from '../modules/fomantic/base.ts';
-import {createElementFromHTML} from '../utils/dom.ts';
+import {createElementFromHTML, activePageTimerRefresh} from '../utils/dom.ts';
 import {registerGlobalEventFunc} from '../modules/observer.ts';
 
 export function initRepoPullRequestUpdate(el: HTMLElement) {
@@ -35,46 +35,22 @@ async function initRepoPullRequestMergeForm(box: HTMLElement) {
   view.mount(el); // TODO: can unmount when reloaded?
 }
 
+function initRepoPullMergeBoxRefresh(el: Element) {
+  activePageTimerRefresh({
+    once: true, // on successful refresh, the data-global-init will re-initialize the element
+    interval: () => Number(el.getAttribute('data-pull-merge-box-reloading-interval')),
+    async callback() {
+      const pullLink = el.getAttribute('data-pull-link')!;
+      const resp = await GET(`${pullLink}/merge_box`);
+      if (!resp.ok) return;
+      const newEl = createElementFromHTML(await resp.text());
+      el.replaceWith(newEl); // don't morph, do full replacement to make sure data-global-init and Vue components are re-initialized
+    },
+  });
+}
+
 export function initRepoPullMergeBox(el: HTMLElement) {
   registerGlobalEventFunc('click', 'onCommitStatusChecksToggle', onCommitStatusChecksToggle);
   initRepoPullRequestMergeForm(el);
-
-  const reloadingIntervalValue = el.getAttribute('data-pull-merge-box-reloading-interval');
-  if (!reloadingIntervalValue) return;
-
-  const reloadingInterval = parseInt(reloadingIntervalValue);
-  const pullLink = el.getAttribute('data-pull-link');
-  let timerId: number | null;
-
-  let reloadMergeBox: () => Promise<void>;
-  const stopReloading = () => {
-    if (!timerId) return;
-    clearTimeout(timerId);
-    timerId = null;
-  };
-  const startReloading = () => {
-    if (timerId) return;
-    setTimeout(reloadMergeBox, reloadingInterval);
-  };
-  const onVisibilityChange = () => {
-    if (document.hidden) {
-      stopReloading();
-    } else {
-      startReloading();
-    }
-  };
-  reloadMergeBox = async () => {
-    const resp = await GET(`${pullLink}/merge_box`);
-    stopReloading();
-    if (!resp.ok) {
-      startReloading();
-      return;
-    }
-    document.removeEventListener('visibilitychange', onVisibilityChange);
-    const newElem = createElementFromHTML(await resp.text());
-    el.replaceWith(newElem);
-  };
-
-  document.addEventListener('visibilitychange', onVisibilityChange);
-  startReloading();
+  initRepoPullMergeBoxRefresh(el);
 }

web_src/js/utils/dom.ts

@@ -339,3 +339,75 @@ let elemIdCounter = 0;
 export function generateElemId(prefix: string = ''): string {
   return `${prefix}${elemIdCounter++}`;
 }
+
+export type ActivePageTimerOptions = {
+  once?: boolean;
+  interval: () => number; // if it returns 0, the timer is stopped
+  callback: () => Promise<void>;
+};
+
+export class ActivePageTimer {
+  private readonly opts: ActivePageTimerOptions;
+  private readonly onVisibilityChange: () => void;
+
+  private sysTimerId?: number;
+  private startTime?: number;
+
+  constructor(opts: ActivePageTimerOptions) {
+    this.opts = opts;
+    this.onVisibilityChange = () => {
+      if (!this.startTime) return;
+      const interval = this.opts.interval();
+      if (document.hidden) {
+        this.clearSysTimer();
+      } else if (interval) {
+        this.startSysTimer(interval);
+      }
+    };
+  }
+
+  private async handler() {
+    this.clear();
+    await this.opts.callback();
+    if (!this.opts.once) this.start();
+  }
+
+  start() {
+    const interval = this.opts.interval();
+    if (!interval) return;
+    if (this.sysTimerId) return;
+    if (!this.startTime) {
+      this.startTime = Date.now();
+      document.addEventListener('visibilitychange', this.onVisibilityChange);
+    }
+    if (!document.hidden) this.startSysTimer(interval);
+  }
+
+  private startSysTimer(interval: number) {
+    const remaining = interval - (Date.now() - this.startTime!);
+    if (remaining <= 0) {
+      this.handler();
+    } else {
+      this.sysTimerId = window.setTimeout(() => this.handler(), remaining);
+    }
+  }
+
+  private clearSysTimer() {
+    if (!this.sysTimerId) return;
+    window.clearTimeout(this.sysTimerId);
+    this.sysTimerId = undefined;
+  }
+
+  clear() {
+    if (!this.startTime) return;
+    this.startTime = undefined;
+    this.clearSysTimer();
+    document.removeEventListener('visibilitychange', this.onVisibilityChange);
+  }
+}
+
+export function activePageTimerRefresh(opts: ActivePageTimerOptions): ActivePageTimer {
+  const timer = new ActivePageTimer(opts);
+  timer.start();
+  return timer;
+}