define(["dom", "browser", "layoutManager"], function (dom, browser, layoutManager) {
    "use strict";

    /**
     * Scroll time in ms.
     */
    var ScrollTime = 270;

    /**
     * Epsilon for comparing values.
     */
    var Epsilon = 1e-6;

    // FIXME: Need to scroll to top of page to fully show the top menu. This can be solved by some marker of top most elements or their containers
    var _minimumScrollY = 0;
    /**
     * Returns minimum vertical scroll.
     * Scroll less than that value will be zeroed.
     *
     * @return {number} minimum vertical scroll
     */
    function minimumScrollY() {
        if (_minimumScrollY === 0) {
            var topMenu = document.querySelector(".headerTop");
            if (topMenu) {
                _minimumScrollY = topMenu.clientHeight;
            }
        }
        return _minimumScrollY;
    }

    var supportsSmoothScroll = "scrollBehavior" in document.documentElement.style;

    var supportsScrollToOptions = false;
    try {
        var elem = document.createElement("div");

        var opts = Object.defineProperty({}, "behavior", {
            get: function () {
                supportsScrollToOptions = true;
            }
        });

        elem.scrollTo(opts);
    } catch(e) {}

    /**
     * Returns value clamped by range [min, max].
     *
     * @param {number} value clamped value
     * @param {number} min begining of range
     * @param {number} max ending of range
     * @return {number} clamped value
     */
    function clamp(value, min, max) {
        return value <= min ? min : value >= max ? max : value;
    }

    /**
     * Returns the required delta to fit range 1 into range 2.
     * In case of range 1 is bigger than range 2 returns delta to fit most out of range part.
     *
     * @param {number} begin1 begining of range 1
     * @param {number} end1 ending of range 1
     * @param {number} begin2 begining of range 2
     * @param {number} end2 ending of range 2
     * @return {number} delta: <0 move range1 to the left, >0 - to the right
     */
    function fitRange(begin1, end1, begin2, end2) {
        var delta1 = begin1 - begin2;
        var delta2 = end2 - end1;
        if (delta1 < 0 && delta1 < delta2) {
            return -delta1;
        } else if (delta2 < 0) {
            return delta2;
        }
        return 0;
    };

    /**
     * Ease value.
     *
     * @param {number} t value in range [0, 1]
     * @return {number} eased value in range [0, 1]
     */
    function ease(t) {
        return t*(2 - t); // easeOutQuad === ease-out
    }

    /**
     * Document scroll wrapper helps to unify scrolling and fix issues of some browsers.
     *
     * webOS 2 Browser: scrolls documentElement (and window), but body has a scroll size
     *
     * webOS 3 Browser: scrolls body (and window)
     *
     * webOS 4 Native: scrolls body (and window); has a document.scrollingElement
     *
     * Tizen 4 Browser/Native: scrolls body (and window); has a document.scrollingElement
     *
     * Tizen 5 Browser/Native: scrolls documentElement (and window); has a document.scrollingElement
     */
    function DocumentScroller() {
    }

    DocumentScroller.prototype = {
        get scrollLeft() {
            return window.pageXOffset;
        },
        set scrollLeft(val) {
            window.scroll(val, window.pageYOffset);
        },

        get scrollTop() {
            return window.pageYOffset;
        },
        set scrollTop(val) {
            window.scroll(window.pageXOffset, val);
        },

        get scrollWidth() {
            return Math.max(document.documentElement.scrollWidth, document.body.scrollWidth);
        },

        get scrollHeight() {
            return Math.max(document.documentElement.scrollHeight, document.body.scrollHeight);
        },

        get clientWidth() {
            return Math.min(document.documentElement.clientWidth, document.body.clientWidth);
        },

        get clientHeight() {
            return Math.min(document.documentElement.clientHeight, document.body.clientHeight);
        },

        getBoundingClientRect: function() {
            // Make valid viewport coordinates: documentElement.getBoundingClientRect returns rect of entire document relative to viewport
            return {
                left: 0,
                top: 0,
                width: this.clientWidth,
                height: this.clientHeight
            };
        },

        scrollTo: function() {
            window.scrollTo.apply(window, arguments);
        }
    };

    var documentScroller = new DocumentScroller();

    /**
     * Returns parent element that can be scrolled. If no such, returns documentElement.
     *
     * @param {HTMLElement} element element for which parent is being searched
     * @param {boolean} vertical search for vertical scrollable parent
     */
    function getScrollableParent(element, vertical) {
        if (element) {
            var parent = element.parentElement;

            while (parent) {
                if ((!vertical && parent.scrollWidth > parent.clientWidth && parent.classList.contains("scrollX")) ||
                    (vertical && parent.scrollHeight > parent.clientHeight) && parent.classList.contains("scrollY")) {
                    return parent;
                }

                parent = parent.parentElement;
            }
        }

        return documentScroller;
    }

    /**
     * @typedef {Object} ScrollerData
     * @property {number} scrollPos current scroll position
     * @property {number} scrollSize scroll size
     * @property {number} clientSize client size
     */

    /**
     * Returns scroll data for specified orientation.
     *
     * @param {HTMLElement} scroller scroller
     * @param {boolean} vertical vertical scroll data
     * @return {ScrollerData} scroll data
     */
    function getScrollerData(scroller, vertical) {
        var data = {};

        if (!vertical) {
            data.scrollPos = scroller.scrollLeft;
            data.scrollSize = scroller.scrollWidth;
            data.clientSize = scroller.clientWidth;
        } else {
            data.scrollPos = scroller.scrollTop;
            data.scrollSize = scroller.scrollHeight;
            data.clientSize = scroller.clientHeight;
        }

        return data;
    }

    /**
     * Returns position of child of scroller for specified orientation.
     *
     * @param {HTMLElement} scroller scroller
     * @param {HTMLElement} element child of scroller
     * @param {boolean} vertical vertical scroll
     * @return {number} child position
     */
    function getScrollerChildPos(scroller, element, vertical) {
        var elementRect = element.getBoundingClientRect();
        var scrollerRect = scroller.getBoundingClientRect();

        if (!vertical) {
            return scroller.scrollLeft + elementRect.left - scrollerRect.left;
        } else {
            return scroller.scrollTop + elementRect.top - scrollerRect.top;
        }
    }

    /**
     * Returns scroll position for element.
     *
     * @param {ScrollerData} scrollerData scroller data
     * @param {number} elementPos child element position
     * @param {number} elementSize child element size
     * @param {boolean} centered scroll to center
     * @return {number} scroll position
     */
    function calcScroll(scrollerData, elementPos, elementSize, centered) {
        var maxScroll = scrollerData.scrollSize - scrollerData.clientSize;

        var scroll;

        if (centered) {
            scroll = elementPos + (elementSize - scrollerData.clientSize) / 2;
        } else {
            var delta = fitRange(elementPos, elementPos + elementSize - 1, scrollerData.scrollPos, scrollerData.scrollPos + scrollerData.clientSize - 1);
            scroll = scrollerData.scrollPos - delta;
        }

        return clamp(Math.round(scroll), 0, maxScroll);
    }

    /**
     * Calls scrollTo function in proper way.
     *
     * @param {HTMLElement} scroller scroller
     * @param {ScrollToOptions} options scroll options
     */
    function scrollToHelper(scroller, options) {
        if ("scrollTo" in scroller) {
            if (!supportsScrollToOptions) {
                var scrollX = (options.left !== undefined ? options.left : scroller.scrollLeft);
                var scrollY = (options.top !== undefined ? options.top : scroller.scrollTop);
                scroller.scrollTo(scrollX, scrollY);
            } else {
                scroller.scrollTo(options);
            }
        } else if ("scrollLeft" in scroller) {
            if (options.left !== undefined) {
                scroller.scrollLeft = options.left;
            }
            if (options.top !== undefined) {
                scroller.scrollTop = options.top;
            }
        }
    }

    /**
     * Performs built-in scroll.
     *
     * @param {HTMLElement} xScroller horizontal scroller
     * @param {number} scrollX horizontal coordinate
     * @param {HTMLElement} yScroller vertical scroller
     * @param {number} scrollY vertical coordinate
     * @param {boolean} smooth smooth scrolling
     */
    function builtinScroll(xScroller, scrollX, yScroller, scrollY, smooth) {
        var scrollBehavior = smooth ? "smooth" : "instant";

        if (xScroller !== yScroller) {
            scrollToHelper(xScroller, {left: scrollX, behavior: scrollBehavior});
            scrollToHelper(yScroller, {top: scrollY, behavior: scrollBehavior});
        } else {
            scrollToHelper(xScroller, {left: scrollX, top: scrollY, behavior: scrollBehavior});
        }
    }

    var scrollTimer;

    /**
     * Resets scroll timer to stop scrolling.
     */
    function resetScrollTimer() {
        cancelAnimationFrame(scrollTimer);
        scrollTimer = undefined;
    }

    /**
     * Performs animated scroll.
     *
     * @param {HTMLElement} xScroller horizontal scroller
     * @param {number} scrollX horizontal coordinate
     * @param {HTMLElement} yScroller vertical scroller
     * @param {number} scrollY vertical coordinate
     */
    function animateScroll(xScroller, scrollX, yScroller, scrollY) {

        var ox = xScroller.scrollLeft;
        var oy = yScroller.scrollTop;
        var dx = scrollX - ox;
        var dy = scrollY - oy;

        if (Math.abs(dx) < Epsilon && Math.abs(dy) < Epsilon) {
            return;
        }

        var start;

        function scrollAnim(currentTimestamp) {

            start = start || currentTimestamp;

            var k = Math.min(1, (currentTimestamp - start) / ScrollTime);

            if (k === 1) {
                resetScrollTimer();
                xScroller.scrollLeft = scrollX;
                yScroller.scrollTop = scrollY;
                return;
            }

            k = ease(k);

            var x = ox + dx*k;
            var y = oy + dy*k;

            builtinScroll(xScroller, x, yScroller, y, false);

            scrollTimer = requestAnimationFrame(scrollAnim);
        };

        scrollTimer = requestAnimationFrame(scrollAnim);
    }

    /**
     * Performs scroll.
     *
     * @param {HTMLElement} xScroller horizontal scroller
     * @param {number} scrollX horizontal coordinate
     * @param {HTMLElement} yScroller vertical scroller
     * @param {number} scrollY vertical coordinate
     * @param {boolean} smooth smooth scrolling
     */
    function doScroll(xScroller, scrollX, yScroller, scrollY, smooth) {

        resetScrollTimer();

        if (smooth && useAnimatedScroll()) {
            animateScroll(xScroller, scrollX, yScroller, scrollY);
        } else {
            builtinScroll(xScroller, scrollX, yScroller, scrollY, smooth);
        }
    }

    /**
     * Returns true if smooth scroll must be used.
     */
    function useSmoothScroll() {

        if (browser.tizen) {
            return true;
        }

        return false;
    };

    /**
     * Returns true if animated implementation of smooth scroll must be used.
     */
    function useAnimatedScroll() {
        // Add block to force using (or not) of animated implementation

        return !supportsSmoothScroll;
    };

    /**
     * Returns true if scroll manager is enabled.
     */
    var isEnabled = function() {

        if (!layoutManager.tv) {
            return false;
        }

        if (browser.tizen) {
            return true;
        }

        if (browser.web0s) {
            return true;
        }

        return false;
    };

    /**
     * Scrolls the document to a given position.
     *
     * @param {number} scrollX horizontal coordinate
     * @param {number} scrollY vertical coordinate
     * @param {boolean} [smooth=false] smooth scrolling
     */
    var scrollTo = function(scrollX, scrollY, smooth) {

        smooth = !!smooth;

        // Scroller is document itself by default
        var scroller = getScrollableParent(null, false);

        var xScrollerData = getScrollerData(scroller, false);
        var yScrollerData = getScrollerData(scroller, true);

        scrollX = clamp(Math.round(scrollX), 0, xScrollerData.scrollSize - xScrollerData.clientSize);
        scrollY = clamp(Math.round(scrollY), 0, yScrollerData.scrollSize - yScrollerData.clientSize);

        doScroll(scroller, scrollX, scroller, scrollY, smooth);
    }

    /**
     * Scrolls the document to a given element.
     *
     * @param {HTMLElement} element target element of scroll task
     * @param {boolean} [smooth=false] smooth scrolling
     */
    var scrollToElement = function(element, smooth) {

        smooth = !!smooth;

        var scrollCenterX = true;
        var scrollCenterY = true;

        var offsetParent = element.offsetParent;

        // In Firefox offsetParent.offsetParent is BODY
        var isFixed = offsetParent && (!offsetParent.offsetParent || window.getComputedStyle(offsetParent).position === "fixed");

        // Scroll fixed elements to nearest edge (or do not scroll at all)
        if (isFixed) {
            scrollCenterX = scrollCenterY = false;
        }

        var xScroller = getScrollableParent(element, false);
        var yScroller = getScrollableParent(element, true);

        var elementRect = element.getBoundingClientRect();

        var xScrollerData = getScrollerData(xScroller, false);
        var yScrollerData = getScrollerData(yScroller, true);

        var xPos = getScrollerChildPos(xScroller, element, false);
        var yPos = getScrollerChildPos(yScroller, element, true);

        var scrollX = calcScroll(xScrollerData, xPos, elementRect.width, scrollCenterX);
        var scrollY = calcScroll(yScrollerData, yPos, elementRect.height, scrollCenterY);

        // HACK: Scroll to top for top menu because it is hidden
        // FIXME: Need a marker to scroll top/bottom
        if (isFixed && elementRect.bottom < 0) {
            scrollY = 0;
        }

        // HACK: Ensure we are at the top
        // FIXME: Need a marker to scroll top/bottom
        if (scrollY < minimumScrollY()) {
            scrollY = 0;
        }

        doScroll(xScroller, scrollX, yScroller, scrollY, smooth);
    }

    if (isEnabled()) {
        dom.addEventListener(window, "focusin", function(e) {
            setTimeout(function() {
                scrollToElement(e.target, useSmoothScroll());
            }, 0);
        }, {capture: true});
    }

    return {
        isEnabled: isEnabled,
        scrollTo: scrollTo,
        scrollToElement: scrollToElement
    };
});