feat: add push pipe

Author: nartc

libs/angular-three/src/index.ts

@@ -11,3 +11,4 @@ export * from './lib/utils/is';
 export * from './lib/loader';
 export * from './lib/di/ref';
 export * from './lib/di/destroy';
+export * from './lib/pipes/push';

libs/angular-three/src/lib/pipes/push.ts

@@ -0,0 +1,57 @@
+import { ChangeDetectorRef, inject, OnDestroy, Pipe, PipeTransform } from '@angular/core';
+import { isObservable, ObservableInput, Subscription } from 'rxjs';
+
+function isPromise(value: unknown): value is Promise<unknown> {
+    return (
+        (value instanceof Promise || Object.prototype.toString.call(value) === '[object Promise]') &&
+        typeof (value as Promise<unknown>)['then'] === 'function'
+    );
+}
+
+@Pipe({ name: 'ngtPush', pure: false, standalone: true })
+export class NgtPush<T> implements PipeTransform, OnDestroy {
+    private readonly cdr = inject(ChangeDetectorRef);
+    private readonly parentCdr = inject(ChangeDetectorRef, { skipSelf: true, optional: true });
+
+    private sub?: Subscription;
+    private obj?: ObservableInput<T>;
+    private latestValue?: T;
+
+    transform(value: ObservableInput<T>, defaultValue: T = null!): T {
+        if (this.obj === value) {
+            return this.latestValue as T;
+        }
+        this.obj = value;
+        this.latestValue = defaultValue;
+
+        if (this.sub) {
+            this.sub.unsubscribe();
+        }
+
+        if (isObservable(this.obj)) {
+            this.sub = this.obj.subscribe(this.updateValue.bind(this));
+        } else if (isPromise(this.obj)) {
+            (this.obj as Promise<T>).then(this.updateValue.bind(this));
+        } else {
+            throw new Error(`[NGT] Invalid value passed to ngtPush pipe`);
+        }
+
+        return this.latestValue as T;
+    }
+
+    updateValue(val: T) {
+        this.latestValue = val;
+        this.cdr.detectChanges();
+        if (this.parentCdr) {
+            this.parentCdr.detectChanges();
+        }
+    }
+
+    ngOnDestroy() {
+        if (this.sub) {
+            this.sub.unsubscribe();
+        }
+        this.latestValue = undefined;
+        this.obj = undefined;
+    }
+}