/*
    Disclaimer

    While we make every effort to ensure that this code is fit for its intended purpose, we
    make no guarantees as to its functionality. CoreTrek AS will accept no
    responsibility for the loss of data or any other damage or financial loss caused by use
    of this code.


    Copyright

    This programming code is copyright of CoreTrek AS. Permission to run this code is given to
    approved users of CoreTrek's publishing system CorePublish.

    This source code may not be copied, modified or otherwise repurposed for use by a third
    party without the written permission of CoreTrek AS.

    Contact webmaster@coretrek.com for information.

    
    CoreFader
  
    Fades out a div, copies content from another div and
    fades back in. Supports IE 6 and 7, Firefox 1.5+,
    Mozilla and Opera 9+
 
    Example use:
    fader = new Fader('destination',100,10);
    fader.fadeTo('source1');

    @arg elementId string html element id of the master div
    @arg interval int time in milliseconds between each fade step (recommended 50-100).
    @arg fadeStepPercent int percent opacity change in each step.
 
 */

function Fader(elementId, interval, fadeStepPercent) {
    this._object = document.getElementById(elementId);
    if(this._object == null) {
        return;
    }
    
    if(interval == null || interval <= 0 || interval > 10000) {
        alert('Illegal interval  [+0 - 10000].');
        return;
    }
    
    if(fadeStepPercent == null || fadeStepPercent < 1 || fadeStepPercent > 990) {
        alert('Illegal fadeStepPercent [1 - 99]%');
        return;
    }
    
    this._toObject = null;
    this._startOpacity = 100;
    this._endOpacity = 0;
    this._fadeOut = true;
    this._currentOpacity = null;
    this._intervalId = null;
    this._interval = interval;
    this._speed = fadeStepPercent/100;
    this._doFade = null;
    
    // Set doFade delegate
    this.setDoFadeFunction();
}

/**
 * This is the function used to start the fade process.
 * Set what hidden div (display:none) to copy content from.
 */
Fader.prototype.fadeTo = function(to) {
    this._toObject = document.getElementById(to);
    if(this._object == null || this._toObject == null) {
        return;
    }
    
    this._fadeOut = true;
    
    var objRef = this;
    this._intervalId = setInterval(function () { objRef.doFadeTick(); },this._interval);
}

Fader.prototype.fadeOut = function() {
    this._fadeOut = true;
    var objRef = this;
    this._intervalId = setInterval(function () { objRef.doFadeTick(); },this._interval);
}

Fader.prototype.fadeIn = function() {
    this._fadeOut = false;
    var objRef = this;
    this._intervalId = setInterval(function () { objRef.doFadeTick(); },this._interval);
}

// ============= START: Private functions

// Use this function to set a custom setOpacity functio
// to support more browers.
Fader.prototype.setDoFadeFunction = function() {
    switch(navigator.appName) {
        
        case 'Opera': 
        case 'Netscape':
            this._currentOpacity = 1;
            this._object.style.filter = this._currentOpacity;
            this._doSetOpacity = this.setOpacityMoz;
            break;
        
        default:   
            this._currentOpacity = 1;
            this._object.style.filter = this._currentOpacity;
            this._object.style.filter = "alpha(Opacity="+(this._currentOpacity*100)+")";
            this._doSetOpacity = this.setOpacityMSIE;
            break;            
    }
}

Fader.prototype.doFadeTick = function() {
    if(this._fadeOut) {
        if(this._currentOpacity > 0) {
            opacity = (Number(this._currentOpacity)-this._speed)*100;
            opacity = Math.round(opacity)/100;
            this._doSetOpacity(this._object, opacity);
        } else {
            if(this._toObject != null) {
                this._object.innerHTML = this._toObject.innerHTML;        
                this._fadeOut = false;
            } else {
                clearInterval(this._intervalId);
            }
        }
    } else {
        if(this._currentOpacity < 1) {
            opacity = (Number(this._currentOpacity)+this._speed)*100;
            opacity = Math.round(opacity)/100;
            this._doSetOpacity(this._object, opacity);
        } else {
            // end fade process when finished faded back in
            clearInterval(this._intervalId);
        }
    }
}

Fader.prototype.setOpacityMSIE = function(object, opacity) {    
    object.filters.alpha.opacity = (opacity*100);
    this._currentOpacity = opacity;
}

Fader.prototype.setOpacityMoz = function(object, opacity) {
    object.style.opacity = opacity;
    this._currentOpacity = opacity;
}
// ============= START: Private functions
// END: Fader