[REF] initial prototype of owl 2

src/reactivity.ts

@@ -0,0 +1,144 @@
+import { getCurrent } from "./component/component_node";
+
+export function useState<T>(state: T): T {
+  const node = getCurrent()!;
+  return observe(state, () => node.render());
+}
+
+type CB = () => void;
+const observers: WeakMap<any, PSet<CB>> = new WeakMap();
+
+/**
+ * PSet (for Prototypal Set) are sets that can lookup in their "parent sets", if
+ * any.
+ */
+
+class PSet<T> extends Set<T> {
+  parent?: PSet<T>;
+
+  static createChild<T>(parent: PSet<T>): PSet<T> {
+    const pset: PSet<T> = new PSet();
+    pset.parent = parent;
+    return pset;
+  }
+
+  has(key: T): boolean {
+    if (super.has(key)) {
+      return true;
+    }
+    return this.parent ? this.parent.has(key) : false;
+  }
+
+  *[Symbol.iterator](): Generator<T> {
+    let iterator = super[Symbol.iterator]();
+    for (let elem of iterator) {
+      yield elem;
+    }
+    if (this.parent) {
+      for (let elem of this.parent) {
+        yield elem;
+      }
+    }
+  }
+}
+
+// -----------------------------------------------------------------------------
+
+export function observe<T>(value: T, cb: CB): T {
+  if (isNotObservable(value)) {
+    return value;
+  }
+  if (observers.has(value)) {
+    const callbacks = observers.get(value)!;
+    callbacks.add(cb);
+    return value;
+  }
+  const callbacks: PSet<CB> = new PSet();
+  callbacks.add(cb);
+  return observeValue(value, callbacks);
+}
+
+export function unobserve<T>(value: T, cb: () => void) {
+  if (isNotObservable(value)) {
+    return;
+  }
+  if (observers.has(value)) {
+    const callbacks = observers.get(value)!;
+    callbacks.delete(cb);
+  }
+}
+
+function isNotObservable(value: any): boolean {
+  return (
+    value === null || typeof value !== "object" || value instanceof Date || value instanceof Promise
+  );
+}
+
+/**
+ * value should
+ * 1. be observable
+ * 2. not yet be observed
+ */
+function observeValue(value: any, callbacks: PSet<CB>): any {
+  const proxy = new Proxy(value as any, {
+    get(target: any, key: any): any {
+      const current = target[key];
+      if (isNotObservable(current)) {
+        return current;
+      }
+      if (observers.has(current)) {
+        // this is wrong ?
+        observers.get(current)!.parent = callbacks;
+        return current;
+      }
+      const subCallbacks = PSet.createChild(callbacks);
+      const subValue = observeValue(current, subCallbacks);
+      target[key] = subValue;
+      return subValue;
+    },
+    set(target: any, key: any, value: any): boolean {
+      // TODO: check if current !== target or proxy ??
+      const current = target[key];
+      if (current !== value) {
+        if (isNotObservable(value)) {
+          target[key] = value;
+        } else {
+          // TODO: test following scenario:
+          // 1. obj1 = observer({a:1}, somecb);
+          // 2. unobserve(obj1, somecb)
+          // 3. obj1.a = {b: 2};
+          // check that somecb was not called
+          // obj1.a.b = 3;
+          // check again that somecb was not called
+          if (observers.has(value)) {
+            const pset = observers.get(value)!;
+            pset.parent = callbacks;
+            target[key] = value;
+          } else {
+            const subCallbacks = PSet.createChild(callbacks);
+            target[key] = observeValue(value, subCallbacks);
+          }
+        }
+        notify(target);
+      }
+      return true;
+    },
+    deleteProperty(target: any, key: any) {
+      if (key in target) {
+        delete target[key];
+        notify(target);
+      }
+      return true;
+    },
+  });
+  observers.set(value, callbacks);
+  observers.set(proxy, callbacks);
+  return proxy;
+}
+
+function notify(value: any) {
+  const cbs = observers.get(value)!;
+  for (let cb of cbs) {
+    cb();
+  }
+}