/*!
 * Elevator.js
 *
 * MIT licensed
 * Copyright (C) 2015 Tim Holman, http://tholman.com
 */

/*********************************************
 * Elevator.js
 *********************************************/

var Elevator = function (options) {

    'use strict';

    // Elements
    var body = null;

    // Scroll vars
    var animation = null;
    var duration = null; // ms
    var customDuration = false;
    var startTime = null;
    var startPosition = null;
    var endPosition = 0;
    var elevating = false;

    var mainAudio;
    var endAudio;
    var mainAudioPath;
    var endAudioPath;
    var preloadAudio;
    var loopAudio;

    var that = this;

    /**
     * Utils
     */

    // Thanks Mr Penner - http://robertpenner.com/easing/
    function easeInOutQuad(t, b, c, d) {
        t /= d / 2;
        if (t < 1) return c / 2 * t * t + b;
        t--;
        return -c / 2 * (t * (t - 2) - 1) + b;
    }

    function extendParameters(options, defaults) {
        for (var option in defaults) {
            var t = options[option] === undefined && typeof option !== "function";
            if (t) {
                options[option] = defaults[option];
            }
        }
        return options;
    }

    function getVerticalOffset(element) {
        var verticalOffset = 0;
        while (element) {
            verticalOffset += element.offsetTop || 0;
            element = element.offsetParent;
        }
        return verticalOffset;
    }

    function getScrollTop() {
        return window.pageYOffset || document.documentElement.scrollTop || body.scrollTop || 0;
    }

    function playAudio(audio) {
        var playPromise = audio.play();
        if (playPromise && playPromise.catch) {
            playPromise.catch(() => 0);
        }
    }

    /**
     * Main
     */

    // Time is passed through requestAnimationFrame, what a world!
    function animateLoop(time) {
        if (!startTime) {
            startTime = time;
        }

        var timeSoFar = time - startTime;
        var easedPosition = easeInOutQuad(timeSoFar, startPosition, endPosition - startPosition, duration);

        window.scrollTo(0, easedPosition);

        if (timeSoFar < duration) {
            animation = requestAnimationFrame(animateLoop);
        } else {
            animationFinished();
        }
    }

//            ELEVATE!
//              /
//         ____
//       .'    '=====<0
//       |======|
//       |======|
//       [IIIIII[\--()
//       |_______|
//       C O O O D
//      C O  O  O D
//     C  O  O  O  D
//     C__O__O__O__D
//    [_____________]
    this.elevate = function () {
        if (elevating) {
            return;
        }

        elevating = true;
        startPosition = getScrollTop();

        // No custom duration set, so we travel at pixels per millisecond. (0.75px per ms)
        if (!customDuration) {
            duration = (startPosition * 1.5);
        }

        requestAnimationFrame(animateLoop);

        loadAudio();

        // Start music!
        if (mainAudio) {
            playAudio(mainAudio);
        }
    };

    function browserMeetsRequirements() {
        return window.requestAnimationFrame && window.Audio && window.addEventListener;
    }

    function resetPositions() {
        startTime = null;
        startPosition = null;
        elevating = false;
    }

    function animationFinished() {

        resetPositions();

        // Stop music!
        if (mainAudio) {
            mainAudio.pause();
            mainAudio.currentTime = 0;
        }

        if (endAudio) {
            playAudio(endAudio);
        }
    }

    function onWindowBlur() {

        // If animating, go straight to the top. And play no more music.
        if (elevating) {
            cancelAnimationFrame(animation);
            resetPositions();

            if (mainAudio) {
                mainAudio.pause();
                mainAudio.currentTime = 0;
            }

            window.scrollTo(0, endPosition);
        }
    }

    function handleElevate(event) {
        if (event && event.type === 'touchend')
            event.preventDefault();
        that.elevate();
    }

    function bindElevateToElement(element) {
        if (element.addEventListener) {
            element.addEventListener('click', handleElevate, false);
            element.addEventListener('touchend', handleElevate, false);
        } else {
            // Older browsers
            element.attachEvent('onclick', function () {
                document.documentElement.scrollTop = endPosition;
                document.body.scrollTop = endPosition;
                window.scroll(0, endPosition);
            });
        }
    }

    function loadAudio() {
        if (!mainAudio && mainAudioPath) {
            mainAudio = new Audio(mainAudioPath);
            mainAudio.setAttribute('preload', preloadAudio);
            mainAudio.setAttribute('loop', loopAudio);
        }

        if (!endAudio && endAudioPath) {
            endAudio = new Audio(endAudioPath);
            endAudio.setAttribute('preload', 'auto');
        }
    }

    function init(_options) {
        // Bind to element click event, if need be.
        body = document.body;

        var defaults = {
            duration: undefined,
            mainAudio: false,
            endAudio: false,
            preloadAudio: 'none',
            loopAudio: true,
        };

        _options = extendParameters(_options, defaults);

        if (_options.elements) {
            for (var i = 0; i < _options.elements.length; i++) {
                bindElevateToElement(_options.elements[i]);
            }
        } else if (_options.element) {
            bindElevateToElement(_options.element);
        }

        // Take the stairs instead
        if (!browserMeetsRequirements()) {
            return;
        }

        if (_options.duration) {
            customDuration = true;
            duration = _options.duration;
        }

        if (_options.targetElement) {
            endPosition = getVerticalOffset(_options.targetElement);
        }

        window.addEventListener('blur', onWindowBlur, false);

        mainAudioPath = _options.mainAudio;
        endAudioPath = _options.endAudio;
        preloadAudio = _options.preloadAudio;
        loopAudio = _options.loopAudio;
    }

    init(options);
};