/**
 * animate.js
 * September 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]
 *
 */

var animate = {
    
    init: function(config) {
    
        if (!config.framerate) {
            config.framerate = 15;
        }
        
        if (!config.motion) {
            config.motion = this.tween.linear;
        }
        
        var period = Math.round(1000 / config.framerate);
        
        config.interval = setInterval(function() {
            animate.animate_iteration(config);
        }, period);
    },

    animate_iteration: function(member) {
    
        var now = new Date();
        var time = now.getTime();
        
        if (!member.is_setup) {
            member.start_time = time;
            this.animate_setup(member);
        }
        
        if (member.iterator && typeof(member.iterator) == 'function') {
            member.iterator(member);
        }
        
        if (time >= member.end_time) {
            
            member.value = member.end_value;
            this.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);
            this.animate_value(member);
        }
    },

    animate_setup: function(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;
    },

    animate_value: function(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;
        }
    },
    
    /*
     * 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.
     */

    tween: {
        
        // simple linear tweening - no easing
        // t: current time, b: beginning value, c: change in value, d: duration
        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
        quad_in: function (t, b, c, d) {
            return c*(t/=d)*t + b;
        },
        
        // quadratic easing out - decelerating to zero velocity
        quad_out: function (t, b, c, d) {
            return -c *(t/=d)*(t-2) + b;
        },
        
        // quadratic easing in/out - acceleration until halfway, then deceleration
        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
        cubic_in: function (t, b, c, d) {
            return c*(t/=d)*t*t + b;
        },
        
        // cubic easing out - decelerating to zero velocity
        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
        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
        quart_in: function (t, b, c, d) {
            return c*(t/=d)*t*t*t + b;
        },
        
        // quartic easing out - decelerating to zero velocity
        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
        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
        quint_in: function (t, b, c, d) {
            return c*(t/=d)*t*t*t*t + b;
        },
        
        // quintic easing out - decelerating to zero velocity
        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
        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
        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
        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
        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
        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
        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
        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
        circ_in: function (t, b, c, d) {
            return -c * (Math.sqrt(1 - (t/=d)*t) - 1) + b;
        },
        
        // circular easing out - decelerating to zero velocity
        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
        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;
        },
        
        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;
            }
        },
        
        bounce_in: function (t, b, c, d) {
            return c - tween.bounce_out(d-t, 0, c, d) + b;
        },
        
        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;
        },
        
        
        back_in: function (t, b, c, d, s) {
            if (s == undefined) s = 1.70158;
            return c*(t/=d)*t*((s+1)*t - s) + b;
        },
        
        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;
        },
        
        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;
        },
        
        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;
        },
        
        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);
        },
        
        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;
        }
     }
};