import * as TKUnit from "../../../TKUnit";
import { Observable, EventData } from "tns-core-modules/data/observable";
import { addWeakEventListener, removeWeakEventListener } from "tns-core-modules/ui/core/weak-event-listener";
import { forceGC } from "../../helper";

class Target {
    public counter: number = 0;
    public onEvent(data: EventData) {
        this.counter++;
    }
}

export function test_addWeakEventListener_throwsWhenCalledwitnInvalid_source() {
    TKUnit.assertThrows(() => {
        addWeakEventListener(undefined, "eventName", emptyHandler, {});
    });
}

export function test_addWeakEventListener_throwsWhenCalledwitnInvalid_target() {
    TKUnit.assertThrows(() => {
        addWeakEventListener(new Observable(), "eventName", emptyHandler, undefined);
    });
}

export function test_addWeakEventListener_throwsWhenCalledwitnInvalid_handler() {
    TKUnit.assertThrows(() => {
        addWeakEventListener(new Observable(), "eventName", undefined, {});
    });
}

export function test_addWeakEventListener_throwsWhenCalledwitnInvalid_name() {
    TKUnit.assertThrows(() => {
        addWeakEventListener(new Observable(), undefined, emptyHandler, {});
    });
}

export function test_addWeakEventListener_listensForEvent() {
    const source = new Observable();
    const target = new Target();

    addWeakEventListener(
        source,
        Observable.propertyChangeEvent,
        target.onEvent,
        target);

    source.set("testProp", "some value");

    TKUnit.assertEqual(target.counter, 1, "Handler not called.");
}

export function test_addWeakEventListener_listensForEven_multipleTargetst() {
    const source = new Observable();
    const target1 = new Target();
    const target2 = new Target();

    addWeakEventListener(source, Observable.propertyChangeEvent, target1.onEvent, target1);
    addWeakEventListener(source, Observable.propertyChangeEvent, target2.onEvent, target2);

    source.set("testProp", "some value");

    TKUnit.assertEqual(target1.counter, 1, "Handler not called.");
    TKUnit.assertEqual(target2.counter, 1, "Handler not called.");
}

export function test_removeWeakEventListener_StopsListeningForEvent() {
    const source = new Observable();
    const target = new Target();

    addWeakEventListener(source, Observable.propertyChangeEvent, target.onEvent, target);
    removeWeakEventListener(source, Observable.propertyChangeEvent, target.onEvent, target)

    source.set("testProp", "some value");
    TKUnit.assertEqual(target.counter, 0, "Handler should not be called.");
}

export function test_handlerIsCalled_WithTargetAsThis() {
    const source = new Observable();
    const target = new Object();
    let callbackCalled = false;
    const handler = function (args: EventData) {
        TKUnit.assertEqual(this, target, "this should be the target");
        callbackCalled = true;
    }

    addWeakEventListener(source, Observable.propertyChangeEvent, handler, target);

    source.set("testProp", "some value");
    TKUnit.assert(callbackCalled, "Handler not called.");
}

function getSourceAsWeakRef(): WeakRef<Observable> {
    return new WeakRef(new Observable());
}

function getTargetAsWeakRef(): WeakRef<Target> {
    return new WeakRef(new Target());
}

export function test_listenerDoesNotRetainTarget(done) {
    const sourceRef = getSourceAsWeakRef();
    const targetRef = getTargetAsWeakRef();

    addWeakEventListener(sourceRef.get(), Observable.propertyChangeEvent, emptyHandler, targetRef.get());
    forceGC();
    
    try {
        TKUnit.assert(!targetRef.get(), "Target should be released after GC");
        done(null);
    }
    catch (e) {
        done(e);
    }
}

export function test_listenerDoesNotRetainSource(done) {
    const sourceRef = getSourceAsWeakRef();
    const targetRef = getTargetAsWeakRef();

    addWeakEventListener(sourceRef.get(), Observable.propertyChangeEvent, targetRef.get().onEvent, targetRef.get());
    forceGC();

    try {
        TKUnit.assert(!sourceRef.get(), "Source should be released after GC");
        done(null);
    }
    catch (e) {
        done(e);
    }
}

export function test_handlerIsDetached_WhenAllListenersAreRemoved() {
    const source = new Observable();

    const target1 = new Target();
    const target2 = new Target();

    addWeakEventListener(source, Observable.propertyChangeEvent, target1.onEvent, target1);
    addWeakEventListener(source, Observable.propertyChangeEvent, target2.onEvent, target2);

    removeWeakEventListener(source, Observable.propertyChangeEvent, target1.onEvent, target1)
    removeWeakEventListener(source, Observable.propertyChangeEvent, target2.onEvent, target2)

    TKUnit.assert(!source.hasListeners(Observable.propertyChangeEvent), "All events should be detached");
}

export function test_autoDetachingOfDeadReferences(done) {
    const source = new Observable();

    for (let i = 0; i < 100; i++) {
        addListenerWithSource(source);
    }

    try {
        const target = new Target();

        addWeakEventListener(source, Observable.propertyChangeEvent, emptyHandler, target);
        removeWeakEventListener(source, Observable.propertyChangeEvent, emptyHandler, target);

        forceGC();

        const testPass = (<any>source)._observers[Observable.propertyChangeEvent] ? (<any>source)._observers[Observable.propertyChangeEvent].length <= 1 : true;
        TKUnit.assert(testPass, "All events should be detached");
        done(null);
    }
    catch (e) {
        done(e);
    }
}

function addListenerWithSource(source: Observable) {
    const target = new Target();
    addWeakEventListener(source, Observable.propertyChangeEvent, target.onEvent, target);
}

function emptyHandler(data: EventData) {
    // Do nothing.
}
