/**
 * animate.js
 * June 2006
 *
 * A time-based controller for manipulating and tweaning CSS properties. The
 * input parameters are discussed in detail below. At the very least, you need
 * to provide a 'target' object, a 'duration', an 'end_value' and either a
 * 'property' to set or a 'handler' function.
 *
 *   target         HTML element object: the thing to be manipulated
 *                  (required)
 *
 *   property       Text: the attribute that will be manipulated over time
 *                  (either 'property' or 'handler' must be included)
 *
 *   handler        Function: takes the config object as an input
 *                  (either 'property' or 'handler' must be included)
 *
 *   iterator       Function: executes on each iteration before a value is set
 *                  (optional, takes the config object as an input)
 *
 *   start_value    Float: the starting value of the animated property
 *                  (required)
 *
 *   end_value      Float: the ending value of the animated property
 *                  (required)
 *
 *   duration       Integer: the duration of the animation in milliseconds.
 *                  (required)
 *
 *   motion         Function: a means for tweaning between start and end
 *                  (optional, defaults to tween.linear -- see below)
 *
 *   framerate      Integer: the number of frames/second to animate on
 *                  (optional, defaults to 15)
 *
 * A few of Robert Penner's Flash tweening functions have been adapted for use
 * with the animate function. The following can be passed as the 'motion'
 * parameter within animate()'s 'config' object.
 *
 *   tween.linear
 *   tween.quad_[in|out|both] (notation refers to three functions)
 *   tween.cubic_[in|out|both]
 *   tween.quart_[in|out|both]
 *   tween.quint_[in|out|both]
 *   tween.sine_[in|out|both]
 *   tween.expo_[in|out|both]
 *   tween.circ_[in|out|both]
 *   tween.bounce_[in|out|both]
 *   tween.back_[in|out|both]
 *   tween.elastic_[in|out|both]
 *
 */

function animate(config) {
    
    if (!config.framerate) {
        config.framerate = 15;
    }
    
    if (!config.motion) {
        config.motion = tween.linear;
    }
    
    var period = Math.round(1000 / config.framerate);
    
    if (!window.animate_members) {
        window.animate_members = new Array();
    }
    
    window.animate_members.push(config);
    config.id = window.animate_members.length - 1;
    
    var interval_script = 'animate_iteration(' + config.id + ')';
    config.interval = setInterval(interval_script, period);
}

function animate_iteration(id) {
    
    var member = window.animate_members[id];
    var now = new Date();
    var time = now.getTime();
    
    if (!member.is_setup) {
        member.start_time = time;
        animate_setup(member);
    }
    
    if (member.iterator && typeof(member.iterator) == 'function') {
        member.iterator(member);
    }
    
    if (time >= member.end_time) {
        
        member.value = member.end_value;
        animate_value(member);
        
        if (typeof(member.callback) == 'function') {
            member.callback(member);
        }
        
        clearInterval(member.interval);
        
    } else {
        
        member.value = member.motion(time - member.start_time,
                                     member.start_value,
                                     member.end_value - member.start_value,
                                     member.duration);
        animate_value(member);
    }
}

function animate_setup(member) {
    
    if (typeof(member.duration) == 'undefined') {
        duration = 0;
    }
    if (typeof(member.prefix) == 'undefined') {
        member.prefix = '';
    }
    if (typeof(member.postfix) == 'undefined') {
        member.postfix = '';
    }
    
    member.start_value = parseFloat(member.start_value);
    member.end_value = parseFloat(member.end_value);
    member.end_time = member.start_time + member.duration;
    member.value = member.start_value;
    member.is_setup = true;
}

function animate_value(member) {
    if (typeof(member.handler) == 'function') {
        member.handler(member);
    } else if (typeof(member.property) != 'undefined') {
        var value = member.prefix + member.value + member.postfix;
        var target = member.target;
        var prop_ladder = member.property.split('.');
        for (var i = 0; i < prop_ladder.length - 1; i++) {
            var prop = prop_ladder.shift();
            target = target[prop];
        }
        var prop = prop_ladder.shift();
        target[prop] = value;
    }
}

function log(msg) {
    setTimeout('throw("'+ msg +'");', 0); 
}

/*
 * The following was adapted from Robert Penner's Easing Equations, which
 * were originally written for Flash.
 *
 * Available at http://www.robertpenner.com/easing/
 *
 * Easing Equations (c) 2003 Robert Penner, all rights reserved.
 * This work is subject to the terms in http://www.robertpenner.com/easing_terms_of_use.html.
 */

var tween = new Object;

// simple linear tweening - no easing
// t: current time, b: beginning value, c: change in value, d: duration
tween.linear = function (t, b, c, d) {
    return c * t / d + b;
}

 ///////////// QUADRATIC EASING: t^2 ///////////////////

// quadratic easing in - accelerating from zero velocity
// t: current time, b: beginning value, c: change in value, d: duration
// t and d can be in frames or seconds/milliseconds
tween.quad_in = function (t, b, c, d) {
    return c*(t/=d)*t + b;
}

// quadratic easing out - decelerating to zero velocity
tween.quad_out = function (t, b, c, d) {
    return -c *(t/=d)*(t-2) + b;
}

// quadratic easing in/out - acceleration until halfway, then deceleration
tween.quad_both = function (t, b, c, d) {
    if ((t/=d/2) < 1) return c/2*t*t + b;
    return -c/2 * ((--t)*(t-2) - 1) + b;
}


 ///////////// CUBIC EASING: t^3 ///////////////////////

// cubic easing in - accelerating from zero velocity
// t: current time, b: beginning value, c: change in value, d: duration
// t and d can be frames or seconds/milliseconds
tween.cubic_in = function (t, b, c, d) {
    return c*(t/=d)*t*t + b;
}

// cubic easing out - decelerating to zero velocity
tween.cubic_out = function (t, b, c, d) {
    return c*((t=t/d-1)*t*t + 1) + b;
}

// cubic easing in/out - acceleration until halfway, then deceleration
tween.cubic_both = function (t, b, c, d) {
    if ((t/=d/2) < 1) return c/2*t*t*t + b;
    return c/2*((t-=2)*t*t + 2) + b;
}


 ///////////// QUARTIC EASING: t^4 /////////////////////

// quartic easing in - accelerating from zero velocity
// t: current time, b: beginning value, c: change in value, d: duration
// t and d can be frames or seconds/milliseconds
tween.quart_in = function (t, b, c, d) {
    return c*(t/=d)*t*t*t + b;
}

// quartic easing out - decelerating to zero velocity
tween.quart_out = function (t, b, c, d) {
    return -c * ((t=t/d-1)*t*t*t - 1) + b;
}

// quartic easing in/out - acceleration until halfway, then deceleration
tween.quart_both = function (t, b, c, d) {
    if ((t/=d/2) < 1) return c/2*t*t*t*t + b;
    return -c/2 * ((t-=2)*t*t*t - 2) + b;
}


 ///////////// QUINTIC EASING: t^5  ////////////////////

// quintic easing in - accelerating from zero velocity
// t: current time, b: beginning value, c: change in value, d: duration
// t and d can be frames or seconds/milliseconds
tween.quint_in = function (t, b, c, d) {
    return c*(t/=d)*t*t*t*t + b;
}

// quintic easing out - decelerating to zero velocity
tween.quint_out = function (t, b, c, d) {
    return c*((t=t/d-1)*t*t*t*t + 1) + b;
}

// quintic easing in/out - acceleration until halfway, then deceleration
tween.quint_both = function (t, b, c, d) {
    if ((t/=d/2) < 1) return c/2*t*t*t*t*t + b;
    return c/2*((t-=2)*t*t*t*t + 2) + b;
}



 ///////////// SINUSOIDAL EASING: sin(t) ///////////////

// sinusoidal easing in - accelerating from zero velocity
// t: current time, b: beginning value, c: change in position, d: duration
tween.sine_in = function (t, b, c, d) {
    return -c * Math.cos(t/d * (Math.PI/2)) + c + b;
}

// sinusoidal easing out - decelerating to zero velocity
tween.sine_out = function (t, b, c, d) {
    return c * Math.sin(t/d * (Math.PI/2)) + b;
}

// sinusoidal easing in/out - accelerating until halfway, then decelerating
tween.sine_both = function (t, b, c, d) {
    return -c/2 * (Math.cos(Math.PI*t/d) - 1) + b;
}


 ///////////// EXPONENTIAL EASING: 2^t /////////////////

// exponential easing in - accelerating from zero velocity
// t: current time, b: beginning value, c: change in position, d: duration
tween.expo_in = function (t, b, c, d) {
    return (t==0) ? b : c * Math.pow(2, 10 * (t/d - 1)) + b;
}

// exponential easing out - decelerating to zero velocity
tween.expo_out = function (t, b, c, d) {
    return (t==d) ? b+c : c * (-Math.pow(2, -10 * t/d) + 1) + b;
}

// exponential easing in/out - accelerating until halfway, then decelerating
tween.expo_both = function (t, b, c, d) {
    if (t==0) return b;
    if (t==d) return b+c;
    if ((t/=d/2) < 1) return c/2 * Math.pow(2, 10 * (t - 1)) + b;
    return c/2 * (-Math.pow(2, -10 * --t) + 2) + b;
}


 /////////// CIRCULAR EASING: sqrt(1-t^2) //////////////

// circular easing in - accelerating from zero velocity
// t: current time, b: beginning value, c: change in position, d: duration
tween.circ_in = function (t, b, c, d) {
    return -c * (Math.sqrt(1 - (t/=d)*t) - 1) + b;
}

// circular easing out - decelerating to zero velocity
tween.circ_out = function (t, b, c, d) {
    return c * Math.sqrt(1 - (t=t/d-1)*t) + b;
}

// circular easing in/out - acceleration until halfway, then deceleration
tween.circ_both = function (t, b, c, d) {
    if ((t/=d/2) < 1) return -c/2 * (Math.sqrt(1 - t*t) - 1) + b;
    return c/2 * (Math.sqrt(1 - (t-=2)*t) + 1) + b;
}

tween.bounce_out = function (t, b, c, d) {
    if ((t/=d) < (1/2.75)) {
        return c*(7.5625*t*t) + b;
    } else if (t < (2/2.75)) {
        return c*(7.5625*(t-=(1.5/2.75))*t + .75) + b;
    } else if (t < (2.5/2.75)) {
        return c*(7.5625*(t-=(2.25/2.75))*t + .9375) + b;
    } else {
        return c*(7.5625*(t-=(2.625/2.75))*t + .984375) + b;
    }
}

tween.bounce_in = function (t, b, c, d) {
    return c - tween.bounce_out(d-t, 0, c, d) + b;
}

tween.bounce_both = function (t, b, c, d) {
    if (t < d/2) return tween.bounce_in(t*2, 0, c, d) * .5 + b;
    else return tween.bounce_out(t*2-d, 0, c, d) * .5 + c*.5 + b;
}


tween.back_in = function (t, b, c, d, s) {
    if (s == undefined) s = 1.70158;
    return c*(t/=d)*t*((s+1)*t - s) + b;
}

tween.back_out = function (t, b, c, d, s) {
    if (s == undefined) s = 1.70158;
    return c*((t=t/d-1)*t*((s+1)*t + s) + 1) + b;
}

tween.back_both = function (t, b, c, d, s) {
    if (s == undefined) s = 1.70158; 
    if ((t/=d/2) < 1) return c/2*(t*t*(((s*=(1.525))+1)*t - s)) + b;
    return c/2*((t-=2)*t*(((s*=(1.525))+1)*t + s) + 2) + b;
}

tween.elastic_in = function (t, b, c, d, a, p) {
    if (t==0) return b;  if ((t/=d)==1) return b+c;  if (!p) p=d*.3;
    if (!a || a < Math.abs(c)) { a=c; var s=p/4; }
    else var s = p/(2*Math.PI) * Math.asin (c/a);
    return -(a*Math.pow(2,10*(t-=1)) * Math.sin( (t*d-s)*(2*Math.PI)/p )) + b;
}

tween.elastic_out = function (t, b, c, d, a, p) {
    if (t==0) return b;  if ((t/=d)==1) return b+c;  if (!p) p=d*.3;
    if (!a || a < Math.abs(c)) { a=c; var s=p/4; }
    else var s = p/(2*Math.PI) * Math.asin (c/a);
    return (a*Math.pow(2,-10*t) * Math.sin( (t*d-s)*(2*Math.PI)/p ) + c + b);
}

tween.elastic_both = function (t, b, c, d, a, p) {
    if (t==0) return b;  if ((t/=d/2)==2) return b+c;  if (!p) p=d*(.3*1.5);
    if (!a || a < Math.abs(c)) { a=c; var s=p/4; }
    else var s = p/(2*Math.PI) * Math.asin (c/a);
    if (t < 1) return -.5*(a*Math.pow(2,10*(t-=1)) * Math.sin( (t*d-s)*(2*Math.PI)/p )) + b;
    return a*Math.pow(2,-10*(t-=1)) * Math.sin( (t*d-s)*(2*Math.PI)/p )*.5 + c + b;
}