/*

Important:

This is sample code demonstrating API, technology or techniques in development.

Although this sample code has been reviewed for technical accuracy, it is not 

final. Apple is supplying this information to help you plan for the adoption of 

the technologies and programming interfaces described herein. This information 

is subject to change, and software implemented based on this sample code should 

be tested with final operating system software and final documentation. Newer 

versions of this sample code may be provided with future seeds of the API or 

technology. For information about updates to this and other developer 

documentation, view the New & Updated sidebars in subsequent documentation seeds.

*/

/*

File: Leaves.js

Abstract: Defines JavaScript functionality for the WithCSSExtensions sample.

          Creates all the leaves but do not animate them. Determines which

          spin animation should be applied to each leaf.

Version: 1.0

Disclaimer: IMPORTANT:  This Apple software is supplied to you by

Apple Inc. ("Apple") in consideration of your agreement to the

following terms, and your use, installation, modification or

redistribution of this Apple software constitutes acceptance of these

terms.  If you do not agree with these terms, please do not use,

install, modify or redistribute this Apple software.

In consideration of your agreement to abide by the following terms, and

subject to these terms, Apple grants you a personal, non-exclusive

license, under Apple's copyrights in this original Apple software (the

"Apple Software"), to use, reproduce, modify and redistribute the Apple

Software, with or without modifications, in source and/or binary forms;

provided that if you redistribute the Apple Software in its entirety and

without modifications, you must retain this notice and the following

text and disclaimers in all such redistributions of the Apple Software.

Neither the name, trademarks, service marks or logos of Apple Inc.

may be used to endorse or promote products derived from the Apple

Software without specific prior written permission from Apple.  Except

as expressly stated in this notice, no other rights or licenses, express

or implied, are granted by Apple herein, including but not limited to

any patent rights that may be infringed by your derivative works or by

other works in which the Apple Software may be incorporated.

The Apple Software is provided by Apple on an "AS IS" basis.  APPLE

MAKES NO WARRANTIES, EXPRESS OR IMPLIED, INCLUDING WITHOUT LIMITATION

THE IMPLIED WARRANTIES OF NON-INFRINGEMENT, MERCHANTABILITY AND FITNESS

FOR A PARTICULAR PURPOSE, REGARDING THE APPLE SOFTWARE OR ITS USE AND

OPERATION ALONE OR IN COMBINATION WITH YOUR PRODUCTS.

IN NO EVENT SHALL APPLE BE LIABLE FOR ANY SPECIAL, INDIRECT, INCIDENTAL

OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF

SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS

INTERRUPTION) ARISING IN ANY WAY OUT OF THE USE, REPRODUCTION,

MODIFICATION AND/OR DISTRIBUTION OF THE APPLE SOFTWARE, HOWEVER CAUSED

AND WHETHER UNDER THEORY OF CONTRACT, TORT (INCLUDING NEGLIGENCE),

STRICT LIABILITY OR OTHERWISE, EVEN IF APPLE HAS BEEN ADVISED OF THE

POSSIBILITY OF SUCH DAMAGE.

Copyright (C) 2008 Apple Inc. All Rights Reserved.

*/

/* Define the number of leaves to be used in the animation */

const NUMBER_OF_LEAVES = 30;

/* 

    Called when the "Falling Leaves" page is completely loaded.

*/

function init()

{

    /* Get a reference to the element that will contain the leaves */

    var container = document.getElementById('leafContainer');

    /* Fill the empty container with new leaves */

    for (var i = 0; i < NUMBER_OF_LEAVES; i++) 

    {

        container.appendChild(createALeaf());

    }

}

/*

    Receives the lowest and highest values of a range and

    returns a random integer that falls within that range.

*/

function randomInteger(low, high)

{

    return low + Math.floor(Math.random() * (high - low));

}

/*

   Receives the lowest and highest values of a range and

   returns a random float that falls within that range.

*/

function randomFloat(low, high)

{

    return low + Math.random() * (high - low);

}

/*

    Receives a number and returns its CSS pixel value.

*/

function pixelValue(value)

{

    return value + 'px';

}

/*

    Returns a duration value for the falling animation.

*/

function durationValue(value)

{

    return value + 's';

}

/*

    Uses an img element to create each leaf. "Leaves.css" implements two spin 

    animations for the leaves: clockwiseSpin and counterclockwiseSpinAndFlip. This

    function determines which of these spin animations should be applied to each leaf.

*/

function createALeaf()

{

    /* Start by creating a wrapper div, and an empty img element */

    var leafDiv = document.createElement('div');

    var image = document.createElement('img');

    /* Randomly choose a leaf image and assign it to the newly created element */

    image.src = 'images/leaf' + randomInteger(1, 5) + '.png';

    /* Position the leaf at a random location within the screen */

    leafDiv.style.top = pixelValue(randomInteger(-150, -50));

    leafDiv.style.left = pixelValue(randomInteger(0, 500));

    /* Randomly choose a spin animation */

    var spinAnimationName = (Math.random() < 0.5) ? 'clockwiseSpin' : 'counterclockwiseSpinAndFlip';

    /* Set the -webkit-animation-name property with these values */

    leafDiv.style.webkitAnimationName = 'fade, drop';

    image.style.webkitAnimationName = spinAnimationName;

    /* Figure out a random duration for the fade and drop animations */

    var fadeAndDropDuration = durationValue(randomFloat(5, 11));

    /* Figure out another random duration for the spin animation */

    var spinDuration = durationValue(randomFloat(4, 8));

    /* Set the -webkit-animation-duration property with these values */

    leafDiv.style.webkitAnimationDuration = fadeAndDropDuration + ', ' + fadeAndDropDuration;

    image.style.webkitAnimationDuration = spinDuration;

    /* Add the created image to the div */

    leafDiv.appendChild(image);

    /* Return this div so it can be added to the document */

    return leafDiv;

}

/* Calls the init function when the "Falling Leaves" page is full loaded */

window.addEventListener('load', init, false);