defineSuite([
        'Widgets/PerformanceWatchdog/PerformanceWatchdogViewModel',
        'Core/defined',
        'Core/getTimestamp',
        'Scene/FrameRateMonitor',
        'Specs/createScene'
    ], function(
        PerformanceWatchdogViewModel,
        defined,
        getTimestamp,
        FrameRateMonitor,
        createScene) {
    'use strict';

    var scene;
    beforeAll(function() {
        scene = createScene();
    });

    afterAll(function() {
        scene.destroyForSpecs();
    });

    var viewModel;
    afterEach(function() {
        if (defined(viewModel)) {
            viewModel.destroy();
            viewModel = undefined;
        }

        FrameRateMonitor.fromScene(scene).destroy();
    });

    function spinWait(milliseconds) {
        /*eslint-disable no-empty*/
        var endTime = getTimestamp() + milliseconds;
        while (getTimestamp() < endTime) {
        }
        /*eslint-enable no-empty*/
    }

    it('throws when constructed without a scene', function() {
        expect(function() {
            viewModel = new PerformanceWatchdogViewModel();
        }).toThrowDeveloperError();

        expect(function() {
            viewModel = new PerformanceWatchdogViewModel({});
        }).toThrowDeveloperError();
    });

    it('can be constructed with just a scene', function() {
        viewModel = new PerformanceWatchdogViewModel({
            scene : scene
        });

        expect(viewModel.lowFrameRateMessage).toBeDefined();
        expect(viewModel.lowFrameRateMessageDismissed).toBe(false);
        expect(viewModel.showingLowFrameRateMessage).toBe(false);
        expect(viewModel.scene).toBe(scene);
    });

    it('honors parameters to the constructor', function() {
        var options = {
            scene : scene,
            lowFrameRateMessage : 'why so slow?'
        };

        viewModel = new PerformanceWatchdogViewModel(options);

        expect(viewModel.lowFrameRateMessage).toBe('why so slow?');
        expect(viewModel.scene).toBe(scene);
    });

    it('shows a message on low frame rate', function() {
        var monitor = FrameRateMonitor.fromScene(scene);
        monitor.quietPeriod = 0.001;
        monitor.warmupPeriod = 0.001;
        monitor.samplingWindow = 0.001;
        monitor.minimumFrameRateDuringWarmup = 1000;
        monitor.minimumFrameRateAfterWarmup = 1000;

        viewModel = new PerformanceWatchdogViewModel({
            scene : scene
        });

        expect(viewModel.showingLowFrameRateMessage).toBe(false);

        // Rendering once starts the quiet period
        scene.render();

        // Wait until we're well past the end of the quiet period.
        spinWait(2);

        // Rendering again records our first sample.
        scene.render();

        // Wait well over a millisecond, which is the maximum frame time allowed by this instance.
        spinWait(2);

        // Record our second sample.  The watchdog should notice that our frame rate is too low.
        scene.render();
        expect(viewModel.showingLowFrameRateMessage).toBe(true);
    });

    it('does not report a low frame rate during the queit period', function() {
        var monitor = FrameRateMonitor.fromScene(scene);
        monitor.quietPeriod = 1.0;
        monitor.warmupPeriod = 0.001;
        monitor.samplingWindow = 0.001;
        monitor.minimumFrameRateDuringWarmup = 1000;
        monitor.minimumFrameRateAfterWarmup = 1000;

        viewModel = new PerformanceWatchdogViewModel({
            scene : scene
        });

        // Rendering once starts the quiet period
        scene.render();

        // Wait well over a millisecond, which is the maximum frame time allowed by this instance.
        spinWait(2);

        // Render again.  Even though our frame rate is too low, the watchdog shouldn't bark because we're in the quiet period.
        scene.render();
        expect(viewModel.showingLowFrameRateMessage).toBe(false);
    });

    it('the low frame rate message goes away after the warmup period if the frame rate returns to nominal', function() {
        var monitor = FrameRateMonitor.fromScene(scene);
        monitor.quietPeriod = 0.001;
        monitor.warmupPeriod = 0.001;
        monitor.samplingWindow = 0.001;
        monitor.minimumFrameRateDuringWarmup = 10;
        monitor.minimumFrameRateAfterWarmup = 10;

        viewModel = new PerformanceWatchdogViewModel({
            scene : scene
        });

        expect(viewModel.showingLowFrameRateMessage).toBe(false);

        // Rendering once starts the quiet period
        scene.render();

        // Wait until we're well past the end of the quiet period.
        spinWait(2);

        // Rendering again records our first sample.
        scene.render();

        // Wait 120 millseconds, which is over the maximum frame time allowed by this instance.
        spinWait(120);

        // Record our second sample.  The watchdog should notice that our frame rate is too low.
        scene.render();
        expect(viewModel.showingLowFrameRateMessage).toBe(true);

        // Render as fast as possible for a samplingWindow, quietPeriod, and warmupPeriod.
        var endTime = getTimestamp() + 50;
        while (getTimestamp() < endTime) {
            scene.render();
        }

        // The low frame rate message should have gone away.
        expect(viewModel.showingLowFrameRateMessage).toBe(false);
    });

    it('does not show the low frame rate message again once it is dismissed', function() {
        var monitor = FrameRateMonitor.fromScene(scene);
        monitor.quietPeriod = 0.001;
        monitor.warmupPeriod = 0.001;
        monitor.samplingWindow = 0.001;
        monitor.minimumFrameRateDuringWarmup = 1000;
        monitor.minimumFrameRateAfterWarmup = 1000;

        viewModel = new PerformanceWatchdogViewModel({
            scene : scene
        });

        expect(viewModel.showingLowFrameRateMessage).toBe(false);

        // Rendering once starts the quiet period
        scene.render();

        // Wait until we're well past the end of the quiet period.
        spinWait(2);

        // Rendering again records our first sample.
        scene.render();

        // Wait well over a millisecond, which is the maximum frame time allowed by this instance.
        spinWait(2);

        // Record our second sample.  The watchdog should notice that our frame rate is too low.
        scene.render();
        expect(viewModel.showingLowFrameRateMessage).toBe(true);

        viewModel.dismissMessage();

        // Render several slow frames.  The message should not re-appear.
        scene.render();
        spinWait(2);
        scene.render();
        expect(viewModel.showingLowFrameRateMessage).toBe(false);
    });
}, 'WebGL');