1 files changed, 112 insertions, 0 deletions
diff --git a/web_src/js/modules/observer.ts b/web_src/js/modules/observer.ts
new file mode 100644
index 0000000000..3305c2f29d
--- /dev/null
+++ b/web_src/js/modules/observer.ts
@@ -0,0 +1,112 @@
+import {isDocumentFragmentOrElementNode} from '../utils/dom.ts';
+import type {Promisable} from 'type-fest';
+import type {InitPerformanceTracer} from './init.ts';
+
+let globalSelectorObserverInited = false;
+
+type SelectorHandler = {selector: string, handler: (el: HTMLElement) => void};
+const selectorHandlers: SelectorHandler[] = [];
+
+type GlobalEventFunc<T extends HTMLElement, E extends Event> = (el: T, e: E) => Promisable<void>;
+const globalEventFuncs: Record<string, GlobalEventFunc<HTMLElement, Event>> = {};
+
+type GlobalInitFunc<T extends HTMLElement> = (el: T) => Promisable<void>;
+const globalInitFuncs: Record<string, GlobalInitFunc<HTMLElement>> = {};
+
+// It handles the global events for all `<div data-global-click="onSomeElemClick"></div>` elements.
+export function registerGlobalEventFunc<T extends HTMLElement, E extends Event>(event: string, name: string, func: GlobalEventFunc<T, E>) {
+  globalEventFuncs[`${event}:${name}`] = func as GlobalEventFunc<HTMLElement, Event>;
+}
+
+// It handles the global init functions by a selector, for example:
+// > registerGlobalSelectorObserver('.ui.dropdown:not(.custom)', (el) => { initDropdown(el, ...) });
+// ATTENTION: For most cases, it's recommended to use registerGlobalInitFunc instead,
+// Because this selector-based approach is less efficient and less maintainable.
+// But if there are already a lot of elements on many pages, this selector-based approach is more convenient for exiting code.
+export function registerGlobalSelectorFunc(selector: string, handler: (el: HTMLElement) => void) {
+  selectorHandlers.push({selector, handler});
+  // Then initAddedElementObserver will call this handler for all existing elements after all handlers are added.
+  // This approach makes the init stage only need to do one "querySelectorAll".
+  if (!globalSelectorObserverInited) return;
+  for (const el of document.querySelectorAll<HTMLElement>(selector)) {
+    handler(el);
+  }
+}
+
+// It handles the global init functions for all `<div data-global-int="initSomeElem"></div>` elements.
+export function registerGlobalInitFunc<T extends HTMLElement>(name: string, handler: GlobalInitFunc<T>) {
+  globalInitFuncs[name] = handler as GlobalInitFunc<HTMLElement>;
+  // The "global init" functions are managed internally and called by callGlobalInitFunc
+  // They must be ready before initGlobalSelectorObserver is called.
+  if (globalSelectorObserverInited) throw new Error('registerGlobalInitFunc() must be called before initGlobalSelectorObserver()');
+}
+
+function callGlobalInitFunc(el: HTMLElement) {
+  const initFunc = el.getAttribute('data-global-init');
+  const func = globalInitFuncs[initFunc];
+  if (!func) throw new Error(`Global init function "${initFunc}" not found`);
+
+  // when an element node is removed and added again, it should not be re-initialized again.
+  type GiteaGlobalInitElement = Partial<HTMLElement> & {_giteaGlobalInited: boolean};
+  if ((el as GiteaGlobalInitElement)._giteaGlobalInited) return;
+  (el as GiteaGlobalInitElement)._giteaGlobalInited = true;
+
+  func(el);
+}
+
+function attachGlobalEvents() {
+  // add global "[data-global-click]" event handler
+  document.addEventListener('click', (e) => {
+    const elem = (e.target as HTMLElement).closest<HTMLElement>('[data-global-click]');
+    if (!elem) return;
+    const funcName = elem.getAttribute('data-global-click');
+    const func = globalEventFuncs[`click:${funcName}`];
+    if (!func) throw new Error(`Global event function "click:${funcName}" not found`);
+    func(elem, e);
+  });
+}
+
+export function initGlobalSelectorObserver(perfTracer?: InitPerformanceTracer): void {
+  if (globalSelectorObserverInited) throw new Error('initGlobalSelectorObserver() already called');
+  globalSelectorObserverInited = true;
+
+  attachGlobalEvents();
+
+  selectorHandlers.push({selector: '[data-global-init]', handler: callGlobalInitFunc});
+  const observer = new MutationObserver((mutationList) => {
+    const len = mutationList.length;
+    for (let i = 0; i < len; i++) {
+      const mutation = mutationList[i];
+      const len = mutation.addedNodes.length;
+      for (let i = 0; i < len; i++) {
+        const addedNode = mutation.addedNodes[i] as HTMLElement;
+        if (!isDocumentFragmentOrElementNode(addedNode)) continue;
+
+        for (const {selector, handler} of selectorHandlers) {
+          if (addedNode.matches(selector)) {
+            handler(addedNode);
+          }
+          for (const el of addedNode.querySelectorAll<HTMLElement>(selector)) {
+            handler(el);
+          }
+        }
+      }
+    }
+  });
+  if (perfTracer) {
+    for (const {selector, handler} of selectorHandlers) {
+      perfTracer.recordCall(`initGlobalSelectorObserver ${selector}`, () => {
+        for (const el of document.querySelectorAll<HTMLElement>(selector)) {
+          handler(el);
+        }
+      });
+    }
+  } else {
+    for (const {selector, handler} of selectorHandlers) {
+      for (const el of document.querySelectorAll<HTMLElement>(selector)) {
+        handler(el);
+      }
+    }
+  }
+  observer.observe(document, {subtree: true, childList: true});
+}