Microsoft/fast-dna

import { expect } from "chai";
import { Updates } from "./update-queue.js";
import { PropertyChangeNotifier, SubscriberSet } from "./notifier.js";
import { ExecutionContext, Expression, Observable, observable, volatile } from "./observable.js";
import { Fake } from "../testing/fakes.js";

describe("The Observable", () => {
    class Model {
        @observable child = new ChildModel();
        @observable child2 = new ChildModel();
        @observable trigger = 0;
        @observable value = 10;

        childChangedCalled = false;

        childChanged() {
            this.childChangedCalled = true;
        }

        incrementTrigger() {
            this.trigger++;
        }

        decrementTrigger() {
            this.trigger--;
        }

        @volatile
        get ternaryConditional() {
            return this.trigger < 1 ? 42 : this.value;
        }

        get ifConditional() {
            Observable.trackVolatile();

            if (this.trigger < 1) {
                return 42;
            }

            return this.value;
        }

        @volatile
        get andCondition() {
            return this.trigger && this.value;
        }
    }

    class ChildModel {
        @observable value = "value";
    }

    class DerivedModel extends Model {
        @observable derivedChild = new ChildModel();

        child2ChangedCalled = false;

        child2Changed() {
            this.child2ChangedCalled = true;
        }
    }

    context("facade", () => {
        it("can get a notifier for an object", () => {
            const instance = new Model();
            const notifier = Observable.getNotifier(instance);

            expect(notifier).to.instanceOf(PropertyChangeNotifier);
        });

        it("gets the same notifier for the same object", () => {
            const instance = new Model();
            const notifier = Observable.getNotifier(instance);
            const notifier2 = Observable.getNotifier(instance);

            expect(notifier).to.equal(notifier2);
        });

        it("gets different notifiers for different objects", () => {
            const notifier = Observable.getNotifier(new Model());
            const notifier2 = Observable.getNotifier(new Model());

            expect(notifier).to.not.equal(notifier2);
        });

        it("can notify a change on an object", () => {
            const instance = new Model();
            const notifier = Observable.getNotifier(instance);
            let wasNotified = false;

            notifier.subscribe(
                {
                    handleChange() {
                        wasNotified = true;
                    },
                },
                "child"
            );

            expect(wasNotified).to.be.false;
            Observable.notify(instance, "child");
            expect(wasNotified).to.be.true;
        });

        it("can define a property on an object", () => {
            const obj = {} as any;
            expect("value" in obj).to.be.false;

            Observable.defineProperty(obj, "value");
            expect("value" in obj).to.be.true;
        });

        it("can list all accessors for an object", () => {
            const accessors = Observable.getAccessors(new Model());

            expect(accessors.length).to.equal(4);
            expect(accessors[0].name).to.equal("child");
            expect(accessors[1].name).to.equal("child2");
        });

        it("can list accessors for an object, including the prototype chain", () => {
            const accessors = Observable.getAccessors(new DerivedModel());

            expect(accessors.length).to.equal(5);
            expect(accessors[0].name).to.equal("child");
            expect(accessors[1].name).to.equal("child2");
            expect(accessors[4].name).to.equal("derivedChild");
        });

        it("can create a binding observer", () => {
            const binding = (x: Model) => x.child;
            const observer = Observable.binding(binding);

            expect(observer).to.be.instanceOf(SubscriberSet);
        });
    });

    context("BindingObserver", () => {
        it("notifies on changes in a simple binding", async () => {
            const binding = (x: Model) => x.child;
            let wasNotified = false;
            const observer = Observable.binding(binding, {
                handleChange() {
                    wasNotified = true;
                },
            });

            const model = new Model();
            let value = observer.observe(model, Fake.executionContext());
            expect(value).to.equal(model.child);

            expect(wasNotified).to.be.false;
            model.child = new ChildModel();

            await Updates.next();

            expect(wasNotified).to.be.true;

            value = observer.observe(model, Fake.executionContext());
            expect(value).to.equal(model.child);
        });

        it("notifies on changes in a sub-property binding", async () => {
            const binding = (x: Model) => x.child.value;
            let wasNotified = false;
            const observer = Observable.binding(binding, {
                handleChange() {
                    wasNotified = true;
                },
            });

            const model = new Model();
            let value = observer.observe(model, Fake.executionContext());
            expect(value).to.equal(model.child.value);

            expect(wasNotified).to.be.false;
            model.child.value = "something completely different";

            await Updates.next();

            expect(wasNotified).to.be.true;

            value = observer.observe(model, Fake.executionContext());
            expect(value).to.equal(model.child.value);
        });
        it("notifies on changes in a sub-property binding after disconnecting before notification has been processed", async () => {
            const binding = (x: Model) => x.child.value;
            let called = false;
            const observer = Observable.binding(binding, {
                handleChange() {
                    called = true;
                },
            });

            const model = new Model();
            let value = observer.observe(model, Fake.executionContext());
            expect(value).to.equal(model.child.value);

            expect(called).to.be.false;
            model.child.value = "something completely different";
            observer.dispose();

            await Updates.next();

            expect(called).to.be.false;

            value = observer.observe(model, Fake.executionContext());
            expect(value).to.equal(model.child.value);

            model.child.value = "another completely different thing";

            await Updates.next();

            expect(called).to.be.true;
        });

        it("notifies on changes in a multi-property binding", async () => {
            const binding = (x: Model) => x.child.value + x.child2.value;

            let wasNotified = false;
            const observer = Observable.binding(binding, {
                handleChange() {
                    wasNotified = true;
                },
            });

            const model = new Model();
            let value = observer.observe(model, Fake.executionContext());
            expect(value).to.equal(model.child.value + model.child2.value);

            // change child.value
            expect(wasNotified).to.be.false;
            model.child.value = "something completely different";

            await Updates.next();

            expect(wasNotified).to.be.true;

            value = observer.observe(model, Fake.executionContext());
            expect(value).to.equal(model.child.value + model.child2.value);

            // change child2.value
            wasNotified = false;
            model.child2.value = "another thing";

            await Updates.next();

            expect(wasNotified).to.be.true;

            value = observer.observe(model, Fake.executionContext());
            expect(value).to.equal(model.child.value + model.child2.value);

            // change child
            wasNotified = false;
            model.child = new ChildModel();

            await Updates.next();

            expect(wasNotified).to.be.true;

            value = observer.observe(model, Fake.executionContext());
            expect(value).to.equal(model.child.value + model.child2.value);

            // change child 2
            wasNotified = false;
            model.child2 = new ChildModel();

            await Updates.next();

            expect(wasNotified).to.be.true;

            value = observer.observe(model, Fake.executionContext());
            expect(value).to.equal(model.child.value + model.child2.value);
        });

        it("notifies on changes in a ternary expression", async () => {
            const binding = (x: Model) => (x.trigger < 1 ? 42 : x.value);

            let wasNotified = false;
            const observer = Observable.binding(binding, {
                handleChange() {
                    wasNotified = true;
                },
            });

            const model = new Model();
            let value = observer.observe(model, Fake.executionContext());
            expect(value).to.equal(binding(model));

            expect(wasNotified).to.be.false;
            model.incrementTrigger();

            await Updates.next();

            expect(wasNotified).to.be.true;

            value = observer.observe(model, Fake.executionContext());
            expect(value).to.equal(binding(model));

            wasNotified = false;
            model.value = 20;

            await Updates.next();

            expect(wasNotified).to.be.true;

            value = observer.observe(model, Fake.executionContext());
            expect(value).to.equal(binding(model));
        });

        it("notifies on changes in a computed ternary expression", async () => {
            const binding = (x: Model) => x.ternaryConditional;

            let wasNotified = false;
            const observer = Observable.binding(binding, {
                handleChange() {
                    wasNotified = true;
                },
            });

            const model = new Model();
            let value = observer.observe(model, Fake.executionContext());
            expect(value).to.equal(binding(model));

            expect(wasNotified).to.be.false;
            model.incrementTrigger();

            await Updates.next();

            expect(wasNotified).to.be.true;

            value = observer.observe(model, Fake.executionContext());
            expect(value).to.equal(binding(model));

            wasNotified = false;
            model.value = 20;

            await Updates.next();

            expect(wasNotified).to.be.true;

            value = observer.observe(model, Fake.executionContext());
            expect(value).to.equal(binding(model));
        });

        it("notifies on changes in an if expression", async () => {
            const binding = (x: Model) => {
                if (x.trigger < 1) {
                    return 42;
                }

                return x.value;
            };

            let wasNotified = false;
            const observer = Observable.binding(binding, {
                handleChange() {
                    wasNotified = true;
                },
            });

            const model = new Model();
            let value = observer.observe(model, Fake.executionContext());
            expect(value).to.equal(binding(model));

            expect(wasNotified).to.be.false;
            model.incrementTrigger();

            await Updates.next();

            expect(wasNotified).to.be.true;

            value = observer.observe(model, Fake.executionContext());
            expect(value).to.equal(binding(model));

            wasNotified = false;
            model.value = 20;

            await Updates.next();

            expect(wasNotified).to.be.true;

            value = observer.observe(model, Fake.executionContext());
            expect(value).to.equal(binding(model));
        });

        it("notifies on changes in a computed if expression", async () => {
            const binding = (x: Model) => x.ifConditional;

            let wasNotified = false;
            const observer = Observable.binding(binding, {
                handleChange() {
                    wasNotified = true;
                },
            });

            const model = new Model();
            let value = observer.observe(model, Fake.executionContext());
            expect(value).to.equal(binding(model));

            expect(wasNotified).to.be.false;
            model.incrementTrigger();

            await Updates.next();

            expect(wasNotified).to.be.true;

            value = observer.observe(model, Fake.executionContext());
            expect(value).to.equal(binding(model));

            wasNotified = false;
            model.value = 20;

            await Updates.next();

            expect(wasNotified).to.be.true;

            value = observer.observe(model, Fake.executionContext());
            expect(value).to.equal(binding(model));
        });

        it("notifies on changes in an && expression", async () => {
            const binding = (x: Model) => x.trigger && x.value;

            let wasNotified = false;
            const observer = Observable.binding(binding, {
                handleChange() {
                    wasNotified = true;
                },
            });

            const model = new Model();
            let value = observer.observe(model, Fake.executionContext());
            expect(value).to.equal(binding(model));

            expect(wasNotified).to.be.false;
            model.incrementTrigger();

            await Updates.next();

            expect(wasNotified).to.be.true;

            value = observer.observe(model, Fake.executionContext());
            expect(value).to.equal(binding(model));

            wasNotified = false;
            model.value = 20;

            await Updates.next();

            expect(wasNotified).to.be.true;

            value = observer.observe(model, Fake.executionContext());
            expect(value).to.equal(binding(model));
        });

        it("notifies on changes in a computed && expression", async () => {
            const binding = (x: Model) => x.trigger && x.value;

            let wasNotified = false;
            const observer = Observable.binding(binding, {
                handleChange() {
                    wasNotified = true;
                },
            });

            const model = new Model();
            let value = observer.observe(model, Fake.executionContext());
            expect(value).to.equal(binding(model));

            expect(wasNotified).to.be.false;
            model.incrementTrigger();

            await Updates.next();

            expect(wasNotified).to.be.true;

            value = observer.observe(model, Fake.executionContext());
            expect(value).to.equal(binding(model));

            wasNotified = false;
            model.value = 20;

            await Updates.next();

            expect(wasNotified).to.be.true;

            value = observer.observe(model, Fake.executionContext());
            expect(value).to.equal(binding(model));
        });

        it("notifies on changes in an || expression", async () => {
            const binding = (x: Model) => x.trigger || x.value;

            let wasNotified = false;
            const observer = Observable.binding(binding, {
                handleChange() {
                    wasNotified = true;
                },
            });

            const model = new Model();
            model.incrementTrigger();

            let value = observer.observe(model, Fake.executionContext());
            expect(value).to.equal(binding(model));

            expect(wasNotified).to.be.false;
            model.decrementTrigger();

            await Updates.next();

            expect(wasNotified).to.be.true;

            value = observer.observe(model, Fake.executionContext());
            expect(value).to.equal(binding(model));

            wasNotified = false;
            model.value = 20;

            await Updates.next();

            expect(wasNotified).to.be.true;

            value = observer.observe(model, Fake.executionContext());
            expect(value).to.equal(binding(model));
        });

        it("notifies on changes in a switch/case expression", async () => {
            const binding = (x: Model) => {
                switch (x.trigger) {
                    case 0:
                        return 42;
                    default:
                        return x.value;
                }
            };

            let wasNotified = false;
            const observer = Observable.binding(binding, {
                handleChange() {
                    wasNotified = true;
                },
            });

            const model = new Model();
            let value = observer.observe(model, Fake.executionContext());
            expect(value).to.equal(binding(model));

            expect(wasNotified).to.be.false;
            model.incrementTrigger();

            await Updates.next();

            expect(wasNotified).to.be.true;

            value = observer.observe(model, Fake.executionContext());
            expect(value).to.equal(binding(model));

            wasNotified = false;
            model.value = 20;

            await Updates.next();

            expect(wasNotified).to.be.true;

            value = observer.observe(model, Fake.executionContext());
            expect(value).to.equal(binding(model));
        });

        it("does not notify if disconnected", async () => {
            let wasCalled = false;
            const binding = (x: Model) => x.value;
            const observer = Observable.binding(binding, {
                handleChange() {
                    wasCalled = true;
                },
            });

            const model = new Model();

            const value = observer.observe(model, Fake.executionContext());
            expect(value).to.equal(model.value);
            expect(wasCalled).to.equal(false);

            model.value++;
            observer.dispose();

            await Updates.next();

            expect(wasCalled).to.equal(false);
        });


        it("allows inspection of subscription records of used observables after observation", () => {
            const observed = [{}, {}, {}].map(( x: any, i ) => {
                Observable.defineProperty(x, "value");
                x.value = i
                return x;
            });

            function binding() {
                return observed[0].value + observed[1].value + observed[2].value
            }

            const bindingObserver = Observable.binding(binding);
            bindingObserver.observe({}, Fake.executionContext());

            let i = 0;
            for (const record of bindingObserver.records()) {
                expect(record.propertySource).to.equal(observed[i]);
                i++;
            }
        });
    });

    context("DefaultObservableAccessor", () => {
        it("calls its own change callback", () => {
            const model = new Model();
            model.child = new ChildModel();
            expect(model.childChangedCalled).to.be.true;
        });

        it("calls a derived change callback", () => {
            const model = new DerivedModel();
            model.child2 = new ChildModel();
            expect(model.child2ChangedCalled).to.be.true;
        });
    });

    context("isVolatileBinding", () => {
        it("should return true when expression uses ternary operator", () => {
            const expression = (a) => a !== undefined ? a : undefined;

            expect(Observable.isVolatileBinding(expression)).to.equal(true)
        });
        it("should return true when expression uses 'if' condition", () => {
            const expression = (a) => { if (a !== undefined) { return a }};

            expect(Observable.isVolatileBinding(expression)).to.equal(true)
        });
        it("should return true when expression uses '&&' operator", () => {
            const expression = (a) => { a && true};

            expect(Observable.isVolatileBinding(expression)).to.equal(true)
        });
        it("should return true when expression uses '||' operator", () => {
            const expression = (a) => { a || true};

            expect(Observable.isVolatileBinding(expression)).to.equal(true)
        });
        it("should return true when when expression uses JavaScript optional chaining", () => {
            // Avoid TS Compiling Optional property syntax away into ternary
            // by using Function constructor
            const expression = Function("(a) => a?.b") as Expression;

            expect(Observable.isVolatileBinding(expression)).to.equal(true)
        })
    })
});