/*

File: Fader.js

Abstract: JavaScript logic for one-off and transitional fades of DOM elements 

    Retasked to use the AppleAnimator class; simpler codebase

Version: 2.0

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*/ 

/*

 *************************************************

 * Fader object fades a single element in or out *

 *************************************************

 */

/*

 * Fader constructor.  Parameters:

 * - element: The element to fade in or out

 * - callback: A function that will be called when a fade is complete

 * - fadeTime: How long (in ms) the fade should take (see setFadeTime())

 */

function Fader (element, callback, fadeTime, minOpacity, maxOpacity) {

    this.element = element;

    this.onFinished = callback;

    // Initialize for a fade-in; these values will be reset by the fadeIn/fadeOut functions

    this.fadingIn;

    this.now = 0.0;

    this.from = 0.0;

    this.to = 1.0;

    this.minOpacity = minOpacity ? minOpacity : 0;

    this.maxOpacity = maxOpacity ? maxOpacity : 1;

    this.setFadeTime(fadeTime);

    var self = this;

    this.nextFrame = function (animation, now, first, done) {

        self.element.style.opacity = now;

    }

}

/* 

 * Prototype method declarations; call these methods as 

 * nameOfFaderInstance.methodName();

 */

Fader.prototype.fadeOut = function () {

    if (this.fadingIn == false) {

        return;

    }

    var from = this.maxOpacity;

    if (this.element.style.opacity) {

        from = parseInt(this.element.style.opacity);

    }

    this.fadeTo(from, this.minOpacity);

    this.fadingIn = false;

}

Fader.prototype.fadeIn = function () {

    if (this.fadingIn == true) {

        return;

    }

    var from = this.minOpacity;

    if (this.element.style.opacity) {

        from = parseInt(this.element.style.opacity);

    }

    this.fadeTo(from, this.maxOpacity);

    this.fadingIn = true;

}

Fader.prototype.fadeTo = function (newFrom, newTo) {

    if (this.fadeAnimator) {

        this.fadeAnimator.stop();

        delete this.fadeAnimator;

    }

    this.fadeAnimator = new AppleAnimator(this.fadeTime, 13, newFrom, newTo, this.nextFrame);

    this.fadeAnimator.oncomplete = this.onFinished;

    this.fadeAnimator.start();

}

/*

 * Setter function for fade duration (floored at 250ms)

 */

Fader.prototype.setFadeTime  = function (fadeTime) {

    this.fadeTime = fadeTime > 250 ? fadeTime : 250;

}

// End Fader object definition

/*

 **********************************************************************

 * TransitionFader object fades between 2 of x number of DOM elements *

 **********************************************************************

 */

/*

 * TransitionFader constructor.  Parameters:

 * - elements: Should be an array; use Fader object to fade a single element in/out

 * - fadeTime: How long (in ms) the fades should take

 * - inDelay: Pause (in ms) between transition fades (see setFadeDelay())

 *

 * As with Fader, all the methods should be called through an instance variable

 */

function TransitionFader (elements, fadeTime, inDelay) {

    // Create two fader objects: incoming and outgoing

    // Set prepNextFade as a callback for one of the faders, so we can cycle

    // through the elements array as a fade completes

    var self = this;

    // Manages which two elements to transition between

    this.prepNextFade = function() {

        if (self.outFader.element) {

            self.outFader.element.style.opacity = 0;

        }

        // Select a new element to be faded in.

        self.currentIndex = (self.currentIndex + 1) % self.elements.length;

        self.outFader = new Fader(self.inFader.element, null, self.inFader.fadeTime);

        self.inFader = new Fader(self.elements[self.currentIndex], self.prepNextFade, self.inFader.fadeTime);

        // Queue up the next transition using the delay property

        window.setTimeout(function() { self.fade(); }, self.delay);

    }   

    this.inFader = new Fader(elements[0], this.prepNextFade, fadeTime);

    this.outFader = new Fader(null, null, fadeTime);

    // All the elements we wish to transition between

    // We do two at a time (one in / one out), but we can move through 

    // an array of any size (see prepNextFade()).

    this.elements = elements;

    this.currentIndex = 0;

    this.setFadeDelay(inDelay);

}

TransitionFader.prototype.start = function () {

    this.inFader.fadeIn();

}

/*

 * Do the fades

 *

 * We check the paused flag in case the delayed call from prepNextFade was

 * already in place before paused was set to true: if so, we postpone the fade

 * and set the interrupted flag (see resume())

 */

TransitionFader.prototype.fade = function () {

    if (this.paused) {

        this.interrupted = true;

        return;

    }

    this.inFader.fadeIn();

    this.outFader.fadeOut();

}

TransitionFader.prototype.getFadeTime = function () {

    return this.inFader.fadeTime;

}

TransitionFader.prototype.setFadeTime = function (newFadeTime) {

    this.inFader.setFadeTime(newFadeTime);

    this.outFader.setFadeTime(newFadeTime);

}

/*

 * Setter for the delay between fades (floored at 500ms)

 */

TransitionFader.prototype.setFadeDelay = function (inDelay) {

    this.delay = inDelay > 500 ? inDelay : 500;

}

/*

 *  Set the paused flag, so the transition timer stops the next time it is hit

 */

TransitionFader.prototype.pause = function () {

    this.paused = true;

}

/*

 * If we are in the middle of a fade, setting paused to false will allow

 * the timers to continue as usual; iff a fade was postponed, we need to 

 * explicitly kick things off again

 */

TransitionFader.prototype.resume = function () {

    this.paused = false;

    if (this.interrupted) {

        this.interrupted = false;

        this.fade();

    }

}