// This file is part of Moodle - http://moodle.org/
//
// Moodle is free software: you can redistribute it and/or modify
// it under the terms of the GNU General Public License as published by
// the Free Software Foundation, either version 3 of the License, or
// (at your option) any later version.
//
// Moodle is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
// GNU General Public License for more details.
//
// You should have received a copy of the GNU General Public License
// along with Moodle.  If not, see <http://www.gnu.org/licenses/>.

/**
 * @module moodle-gradereport_grader-gradereporttable
 * @submodule floatingheaders
 */

/**
 * Provides floating headers to the grader report.
 *
 * See {{#crossLink "M.gradereport_grader.ReportTable"}}{{/crossLink}} for details.
 *
 * @namespace M.gradereport_grader
 * @class FloatingHeaders
 */

var HEIGHT = 'height',
    WIDTH = 'width',
    OFFSETWIDTH = 'offsetWidth',
    OFFSETHEIGHT = 'offsetHeight',
    LOGNS = 'moodle-core-grade-report-grader';

CSS.FLOATING = 'floating';

function FloatingHeaders() {}

FloatingHeaders.ATTRS = {
};

FloatingHeaders.prototype = {
    /**
     * The height of the page header if a fixed position, floating header
     * was found.
     *
     * @property pageHeaderHeight
     * @type Number
     * @default 0
     * @protected
     */
    pageHeaderHeight: 0,

    /**
     * A Node representing the container div.
     *
     * Positioning will be based on this element, which must have
     * the CSS rule 'position: relative'.
     *
     * @property container
     * @type Node
     * @protected
     */
    container: null,

    /**
     * A Node representing the header cell.
     *
     * @property headerCell
     * @type Node
     * @protected
     */
    headerCell: null,

    /**
     * A Node representing the header row.
     *
     * @property headerRow
     * @type Node
     * @protected
     */
    headerRow: null,

    /**
     * A Node representing the first cell which contains user name information.
     *
     * @property firstUserCell
     * @type Node
     * @protected
     */
    firstUserCell: null,

    /**
     * A Node representing the first cell which does not contain a user header.
     *
     * @property firstNonUserCell
     * @type Node
     * @protected
     */
    firstNonUserCell: null,

    /**
     * The position of the left of the first non-header cell in a row - the one after the email address.
     * This is used when processing the scroll event as an optimisation. It must be updated when
     * additional rows are loaded, or the window changes in some fashion.
     *
     * @property firstNonUserCellLeft
     * @type Number
     * @protected
     */
    firstNonUserCellLeft: 0,

    /**
     * The width of the first non-header cell in a row - the one after the email address.
     * This is used when processing the scroll event as an optimisation. It must be updated when
     * additional rows are loaded, or the window changes in some fashion.
     * This is only used for RTL calculations.
     *
     * @property firstNonUserCellWidth
     * @type Number
     * @protected
     */
    firstNonUserCellWidth: 0,

    /**
     * A Node representing the original table footer row.
     *
     * @property tableFooterRow
     * @type Node
     * @protected
     */
    tableFooterRow: null,

    /**
     * A Node representing the floating footer row in the grading table.
     *
     * @property footerRow
     * @type Node
     * @protected
     */
    footerRow: null,

    /**
     * A Node representing the floating grade item header.
     *
     * @property gradeItemHeadingContainer
     * @type Node
     * @protected
     */
    gradeItemHeadingContainer: null,

    /**
     * A Node representing the floating user header. This is the header with the Surname/First name
     * sorting.
     *
     * @property userColumnHeader
     * @type Node
     * @protected
     */
    userColumnHeader: null,

    /**
     * A Node representing the floating user column. This is the column containing all of the user
     * names.
     *
     * @property userColumn
     * @type Node
     * @protected
     */
    userColumn: null,

    /**
     * The position of the bottom of the first user cell.
     * This is used when processing the scroll event as an optimisation. It must be updated when
     * additional rows are loaded, or the window changes in some fashion.
     *
     * @property firstUserCellBottom
     * @type Number
     * @protected
     */
    firstUserCellBottom: 0,

    /**
     * The position of the left of the first user cell.
     * This is used when processing the scroll event as an optimisation. It must be updated when
     * additional rows are loaded, or the window changes in some fashion.
     *
     * @property firstUserCellLeft
     * @type Number
     * @protected
     */
    firstUserCellLeft: 0,

    /**
     * The width of the first user cell.
     * This is used when processing the scroll event as an optimisation. It must be updated when
     * additional rows are loaded, or the window changes in some fashion.
     * This is only used for RTL calculations.
     *
     * @property firstUserCellWidth
     * @type Number
     * @protected
     */
    firstUserCellWidth: 0,

    /**
     * The width of the dock if it is visible.
     *
     * @property dockWidth
     * @type Number
     * @protected
     */
    dockWidth: 0,

    /**
     * The position of the top of the final user cell.
     * This is used when processing the scroll event as an optimisation. It must be updated when
     * additional rows are loaded, or the window changes in some fashion.
     *
     * @property lastUserCellTop
     * @type Number
     * @protected
     */
    lastUserCellTop: 0,

    /**
     * A list of Nodes representing the generic floating rows.
     *
     * @property floatingHeaderRow
     * @type Node{}
     * @protected
     */
    floatingHeaderRow: null,

    /**
     * Array of EventHandles.
     *
     * @type EventHandle[]
     * @property _eventHandles
     * @protected
     */
    _eventHandles: [],

    /**
     * The last value of the bodyMargin style. We need to recompute positions if it is changed.
     *
     * @property lastBodyMargin
     * @type Number
     * @protected
     */
    lastBodyMargin: 0,

    /**
     * Setup the grader report table.
     *
     * @method setupFloatingHeaders
     * @chainable
     */
    setupFloatingHeaders: function() {
        // Grab references to commonly used Nodes.
        this.firstUserCell = Y.one(SELECTORS.USERCELL);
        this.container = Y.one(SELECTORS.GRADEPARENT);
        this.firstNonUserCell = Y.one(SELECTORS.GRADECELL);

        if (!this.firstUserCell) {
            // No need for floating elements, there are no users.
            return this;
        }

        if (M.cfg.behatsiterunning) {
            // If the behat site is running we don't want floating elements.
            return;
        }

        // Generate floating elements.
        this._setupFloatingUserColumn();
        this._setupFloatingUserHeader();
        this._setupFloatingAssignmentHeaders();
        this._setupFloatingAssignmentFooter();

        // Setup generic floating left-aligned headers.
        this.floatingHeaderRow = {};

        // The 'Controls' row (shown in editing mode when certain options are set).
        this._setupFloatingLeftHeaders('.controls .controls');

        // The 'Range' row (shown in editing mode when certain options are set).
        this._setupFloatingLeftHeaders('.range .range');

        // The 'Overall Average' field.
        this._setupFloatingLeftHeaders(SELECTORS.FOOTERTITLE);

        // Additional setup for the footertitle.
        this._setupFloatingAssignmentFooterTitle();

        // Calculate the positions of edge cells. These are used for positioning of the floating headers.
        // This must be called after the floating headers are setup, but before the scroll event handler is invoked.
        this._calculateCellPositions();

        // Setup the floating element initial positions by simulating scroll.
        this._handleScrollEvent();

        // Setup the event handlers.
        this._setupEventHandlers();

        // Listen for a resize event globally - other parts of the code not in this YUI wrapper may make changes to the
        // fields which result in size changes.
        Y.Global.on('moodle-gradereport_grader:resized', this._handleResizeEvent, this);

        return this;
    },

    /**
     * Calculate the positions of some cells. These values are used heavily
     * in scroll event handling.
     *
     * @method _calculateCellPositions
     * @protected
     */
    _calculateCellPositions: function() {
        // The header row shows the grade item headers and is floated to the top of the window.
        this.headerRowTop = this.headerRow.getY();

        // The footer row shows the grade averages and will be floated to the page bottom.
        if (this.tableFooterRow) {
            this.footerRowPosition = this.tableFooterRow.getY();
        }

        // Add the width of the dock if it is visible.
        this.dockWidth = 0;
        var dock = Y.one('.has_dock #dock');
        if (dock) {
            this.dockWidth = dock.get(OFFSETWIDTH);
        }

        var userCellList = Y.all(SELECTORS.USERCELL);

        // The left of the user cells matches the left of the headerRow.
        this.firstUserCellLeft = this.firstUserCell.getX();
        this.firstUserCellWidth = this.firstUserCell.get(OFFSETWIDTH);

        // The left of the user cells matches the left of the footer title.
        this.firstNonUserCellLeft = this.firstNonUserCell.getX();
        this.firstNonUserCellWidth = this.firstNonUserCell.get(OFFSETWIDTH);

        if (userCellList.size() > 1) {
            // Use the top of the second cell for the bottom of the first cell.
            // This is used when scrolling to fix the footer to the top edge of the window.
            var firstUserCell = userCellList.item(1);
            this.firstUserCellBottom = firstUserCell.getY() + parseInt(firstUserCell.getComputedStyle(HEIGHT), 10);

            // Use the top of the penultimate cell when scrolling the header.
            // The header is the same size as the cells.
            this.lastUserCellTop = userCellList.item(userCellList.size() - 2).getY();
        } else {
            var firstItem = userCellList.item(0);
            // We can't use the top of the second row as there is only one row.
            this.lastUserCellTop = firstItem.getY();

            if (this.tableFooterRow) {
                // The footer is present so we can use that.
                this.firstUserCellBottom = this.footerRowPosition + parseInt(this.tableFooterRow.getComputedStyle(HEIGHT), 10);
            } else {
                // No other clues - calculate the top instead.
                this.firstUserCellBottom = firstItem.getY() + firstItem.get('offsetHeight');
            }
        }

        // Check whether a header is present and whether it is floating.
        var header = Y.one('header');
        this.pageHeaderHeight = 0;
        if (header) {
            if (header.getComputedStyle('position') === 'fixed') {
                this.pageHeaderHeight = header.get(OFFSETHEIGHT);
            } else {
                var navbar = Y.one('.navbar');

                if (navbar && navbar.getComputedStyle('position') === 'fixed') {
                    // If the navbar exists and isn't fixed, we need to offset the page header to accommodate for it.
                    this.pageHeaderHeight = navbar.get(OFFSETHEIGHT);
                }
            }
        }
    },

    /**
     * Get the relative XY of the node.
     *
     * @method _getRelativeXY
     * @protected
     * @param {Node} node The node to get the position of.
     * @return {Array} Containing X and Y.
     */
    _getRelativeXY: function(node) {
        return this._getRelativeXYFromXY(node.getX(), node.getY());
    },

    /**
     * Get the relative positioning from coordinates.
     *
     * This gives the position according to the parent of the table, which must
     * be set as position: relative.
     *
     * @method _getRelativeXYFromXY
     * @protected
     * @param {Number} x X position.
     * @param {Number} y Y position.
     * @return {Array} Containing X and Y.
     */
    _getRelativeXYFromXY: function(x, y) {
        var parentXY = this.container.getXY();
        return [x - parentXY[0], y - parentXY[1]];
    },

    /**
     * Get the relative positioning of an elements from coordinates.
     *
     * @method _getRelativeXFromX
     * @protected
     * @param {Number} pos X position.
     * @return {Number} relative X position.
     */
    _getRelativeXFromX: function(pos) {
        return this._getRelativeXYFromXY(pos, 0)[0];
    },

    /**
     * Get the relative positioning of an elements from coordinates.
     *
     * @method _getRelativeYFromY
     * @protected
     * @param {Number} pos Y position.
     * @return {Number} relative Y position.
     */
    _getRelativeYFromY: function(pos) {
        return this._getRelativeXYFromXY(0, pos)[1];
    },

    /**
     * Return the size of the horizontal scrollbar.
     *
     * @method _getScrollBarHeight
     * @protected
     * @return {Number} Height of the scrollbar.
     */
    _getScrollBarHeight: function() {
        if (Y.UA.ie && Y.UA.ie >= 10) {
            // IE has transparent scrollbars, which sometimes disappear... it's better to ignore them.
            return 0;
        } else if (Y.config.doc.body.scrollWidth > Y.config.doc.body.clientWidth) {
            // The document can be horizontally scrolled.
            return Y.DOM.getScrollbarWidth();
        }
        return 0;
    },

    /**
     * Setup the main event listeners.
     * These deal with things like window events.
     *
     * @method _setupEventHandlers
     * @protected
     */
    _setupEventHandlers: function() {
        this._eventHandles.push(
            // Listen for window scrolls, resizes, and rotation events.
            Y.one(Y.config.win).on('scroll', this._handleScrollEvent, this),
            Y.one(Y.config.win).on('resize', this._handleResizeEvent, this),
            Y.one(Y.config.win).on('orientationchange', this._handleResizeEvent, this),
            Y.Global.on('dock:shown', this._handleResizeEvent, this),
            Y.Global.on('dock:hidden', this._handleResizeEvent, this)
        );
    },

    /**
     * Create and setup the floating column of user names.
     *
     * @method _setupFloatingUserColumn
     * @protected
     */
    _setupFloatingUserColumn: function() {
        // Grab all cells in the user names column.
        var userColumn = Y.all(SELECTORS.USERCELL),

        // Create a floating table.
            floatingUserColumn = Y.Node.create('<div aria-hidden="true" role="presentation" class="floater sideonly"></div>'),

        // Get the XY for the floating element.
            coordinates = this._getRelativeXY(this.firstUserCell);

        // Generate the new fields.
        userColumn.each(function(node) {
            var height = node.getComputedStyle(HEIGHT);
            // Nasty hack to account for Internet Explorer
            if (Y.UA.ie !== 0) {
                var allHeight = node.get('offsetHeight');
                var marginHeight = parseInt(node.getComputedStyle('marginTop'), 10) +
                    parseInt(node.getComputedStyle('marginBottom'), 10);
                var paddingHeight = parseInt(node.getComputedStyle('paddingTop'), 10) +
                    parseInt(node.getComputedStyle('paddingBottom'), 10);
                var borderHeight = parseInt(node.getComputedStyle('borderTopWidth'), 10) +
                    parseInt(node.getComputedStyle('borderBottomWidth'), 10);
                height = allHeight - marginHeight - paddingHeight - borderHeight;
            }
            // Create and configure the new container.
            var containerNode = Y.Node.create('<div></div>');
            containerNode.set('innerHTML', node.get('innerHTML'))
                    .setAttribute('class', node.getAttribute('class'))
                    .setAttribute('data-uid', node.ancestor('tr').getData('uid'))
                    .setStyles({
                        height: height,
                        width:  node.getComputedStyle(WIDTH)
                    });

            // Add the new nodes to our floating table.
            floatingUserColumn.appendChild(containerNode);
        }, this);

        // Style the floating user container.
        floatingUserColumn.setStyles({
            left:       coordinates[0] + 'px',
            position:   'absolute',
            top:        coordinates[1] + 'px'
        });

        // Append to the grader region.
        this.graderRegion.append(floatingUserColumn);

        // Store a reference to this for later - we use it in the event handlers.
        this.userColumn = floatingUserColumn;
    },

    /**
     * Create and setup the floating username header cell.
     *
     * @method _setupFloatingUserHeader
     * @protected
     */
    _setupFloatingUserHeader: function() {
        // We make various references to the header cells. Store it for later.
        this.headerRow = Y.one(SELECTORS.HEADERROW);
        this.headerCell = Y.one(SELECTORS.STUDENTHEADER);

        // Create the floating row and cell.
        var floatingUserHeaderRow = Y.Node.create('<div aria-hidden="true" role="presentation" ' +
                                                   'class="floater sideonly heading"></div>'),
            floatingUserHeaderCell = Y.Node.create('<div></div>'),
            nodepos = this._getRelativeXY(this.headerCell)[0],
            coordinates = this._getRelativeXY(this.headerRow),
            gradeHeadersOffset = coordinates[0];

        // Append the content and style to the floating cell.
        floatingUserHeaderCell
            .set('innerHTML', this.headerCell.getHTML())
            .setAttribute('class', this.headerCell.getAttribute('class'))
            .setStyles({
                // The header is larger than the user cells, so we take the user cell.
                width:      this.firstUserCell.getComputedStyle(WIDTH),
                left:       (nodepos - gradeHeadersOffset) + 'px'
            });

        // Style the floating row.
        floatingUserHeaderRow
            .setStyles({
                left:       coordinates[0] + 'px',
                position:   'absolute',
                top:        coordinates[1] + 'px'
            });

        // Append the cell to the row, and finally to the region.
        floatingUserHeaderRow.append(floatingUserHeaderCell);
        this.graderRegion.append(floatingUserHeaderRow);

        // Store a reference to this for later - we use it in the event handlers.
        this.userColumnHeader = floatingUserHeaderRow;
    },

    /**
     * Create and setup the floating grade item header row.
     *
     * @method _setupFloatingAssignmentHeaders
     * @protected
     */
    _setupFloatingAssignmentHeaders: function() {
        this.headerRow = Y.one('#user-grades tr.heading');

        var gradeHeaders = Y.all('#user-grades tr.heading .cell');

        // Generate a floating headers
        var floatingGradeHeaders = Y.Node.create('<div aria-hidden="true" role="presentation" class="floater heading"></div>');

        var coordinates = this._getRelativeXY(this.headerRow);

        var floatingGradeHeadersWidth = 0;
        var floatingGradeHeadersHeight = 0;
        var gradeHeadersOffset = coordinates[0];

        gradeHeaders.each(function(node) {
            var nodepos = this._getRelativeXY(node)[0];

            var newnode = Y.Node.create('<div></div>');
            newnode.append(node.getHTML())
                .setAttribute('class', node.getAttribute('class'))
                .setData('itemid', node.getData('itemid'))
                .setStyles({
                    height:     node.getComputedStyle(HEIGHT),
                    left:       (nodepos - gradeHeadersOffset) + 'px',
                    position:   'absolute',
                    width:      node.getComputedStyle(WIDTH)
                });

            // Sum up total widths - these are used in the container styles.
            // Use the offsetHeight and Width here as this contains the
            // padding, margin, and borders.
            floatingGradeHeadersWidth += parseInt(node.get(OFFSETWIDTH), 10);
            floatingGradeHeadersHeight = node.get(OFFSETHEIGHT);

            // Append to our floating table.
            floatingGradeHeaders.appendChild(newnode);
        }, this);

        // Position header table.
        floatingGradeHeaders.setStyles({
            height:     floatingGradeHeadersHeight + 'px',
            left:       coordinates[0] + 'px',
            position:   'absolute',
            top:        coordinates[1] + 'px',
            width:      floatingGradeHeadersWidth + 'px'
        });

        // Insert in place before the grader headers.
        this.userColumnHeader.insert(floatingGradeHeaders, 'before');

        // Store a reference to this for later - we use it in the event handlers.
        this.gradeItemHeadingContainer = floatingGradeHeaders;
    },

    /**
     * Create and setup the floating header row of grade item titles.
     *
     * @method _setupFloatingAssignmentFooter
     * @protected
     */
    _setupFloatingAssignmentFooter: function() {
        this.tableFooterRow = Y.one('#user-grades .avg');
        if (!this.tableFooterRow) {
            Y.log('Averages footer not found - unable to float it.', 'warn', LOGNS);
            return;
        }

        // Generate the sticky footer row.
        var footerCells = this.tableFooterRow.all('.cell');

        // Create a container.
        var floatingGraderFooter = Y.Node.create('<div aria-hidden="true" role="presentation" class="floater avg"></div>');
        var footerWidth = 0;
        var coordinates = this._getRelativeXY(this.tableFooterRow);
        var footerRowOffset = coordinates[0];
        var floatingGraderFooterHeight = 0;

        // Copy cell content.
        footerCells.each(function(node) {
            var newnode = Y.Node.create('<div></div>');
            var nodepos = this._getRelativeXY(node)[0];
            newnode.set('innerHTML', node.getHTML())
                .setAttribute('class', node.getAttribute('class'))
                .setStyles({
                    height:     node.getComputedStyle(HEIGHT),
                    left:       (nodepos - footerRowOffset) + 'px',
                    position:   'absolute',
                    width:      node.getComputedStyle(WIDTH)
                });

            floatingGraderFooter.append(newnode);
            floatingGraderFooterHeight = node.get(OFFSETHEIGHT);
            footerWidth += parseInt(node.get(OFFSETWIDTH), 10);
        }, this);

        // Position the row.
        floatingGraderFooter.setStyles({
            position:   'absolute',
            left:       coordinates[0] + 'px',
            bottom:     '1px',
            height:     floatingGraderFooterHeight + 'px',
            width:      footerWidth + 'px'
        });

        // Append to the grader region.
        this.graderRegion.append(floatingGraderFooter);

        this.footerRow = floatingGraderFooter;
    },

    /**
     * Create and setup the floating footer title cell.
     *
     * @method _setupFloatingAssignmentFooterTitle
     * @protected
     */
    _setupFloatingAssignmentFooterTitle: function() {
        var floatingFooterRow = this.floatingHeaderRow[SELECTORS.FOOTERTITLE];
        if (floatingFooterRow) {
            // Style the floating row.
            floatingFooterRow
                .setStyles({
                    bottom:     '1px'
                });
        }
    },

    /**
     * Create and setup the floating left headers.
     *
     * @method _setupFloatingLeftHeaders
     * @protected
     */
    _setupFloatingLeftHeaders: function(headerSelector) {
        // We make various references to the origin cell. Store it for later.
        var origin = Y.one(headerSelector);

        if (!origin) {
            return;
        }

        // Create the floating row and cell.
        var floatingRow = Y.Node.create('<div aria-hidden="true" role="presentation" class="floater sideonly"></div>'),
            floatingCell = Y.Node.create('<div></div>'),
            coordinates = this._getRelativeXY(origin),
            width = this.firstUserCell.getComputedStyle(WIDTH),
            height = origin.get(OFFSETHEIGHT);

        // Append the content and style to the floating cell.
        floatingCell
            .set('innerHTML', origin.getHTML())
            .setAttribute('class', origin.getAttribute('class'))
            .setStyles({
                // The header is larger than the user cells, so we take the user cell.
                width:      width
            });

        // Style the floating row.
        floatingRow
            .setStyles({
                position:   'absolute',
                top:        coordinates[1] + 'px',
                left:       coordinates[0] + 'px',
                height:     height + 'px'
            })
            // Add all classes from the parent to the row
            .addClass(origin.get('parentNode').get('className'));

        // Append the cell to the row, and finally to the region.
        floatingRow.append(floatingCell);
        this.graderRegion.append(floatingRow);

        // Store a reference to this for later - we use it in the event handlers.
        this.floatingHeaderRow[headerSelector] = floatingRow;
    },

    /**
     * Process a Scroll Event on the window.
     *
     * @method _handleScrollEvent
     * @protected
     */
    _handleScrollEvent: function() {
        // Performance is important in this function as it is called frequently and in quick succesion.
        // To prevent layout thrashing when the DOM is repeatedly updated and queried, updated and queried,
        // updates must be batched.

        // Next do all the calculations.
        var gradeItemHeadingContainerStyles = {},
            userColumnHeaderStyles = {},
            userColumnStyles = {},
            footerStyles = {},
            coord = 0,
            floatingUserTriggerPoint = 0,       // The X position at which the floating should start.
            floatingUserRelativePoint = 0,      // The point to use when calculating the new position.
            headerFloats = false,
            userFloats = false,
            footerFloats = false,
            leftTitleFloats = false,
            floatingHeaderStyles = {},
            floatingFooterTitleStyles = {},
            floatingFooterTitleRow = false,
            bodyMargin = 0;

        if (window.right_to_left()) {
            bodyMargin = parseInt(Y.one(Y.config.doc.body).getComputedStyle('marginRight'), 10);
        } else {
            bodyMargin = parseInt(Y.one(Y.config.doc.body).getComputedStyle('marginLeft'), 10);
        }

        if (bodyMargin != this.lastBodyMargin) {
            // Recalculate the position of the edge cells for scroll positioning.
            this._calculateCellPositions();
        }

        // Header position.
        gradeItemHeadingContainerStyles.left = this._getRelativeXFromX(this.headerRow.getX());
        if (Y.config.win.pageYOffset + this.pageHeaderHeight > this.headerRowTop) {
            headerFloats = true;
            if (Y.config.win.pageYOffset + this.pageHeaderHeight < this.lastUserCellTop) {
                coord = this._getRelativeYFromY(Y.config.win.pageYOffset + this.pageHeaderHeight);
                gradeItemHeadingContainerStyles.top = coord + 'px';
                userColumnHeaderStyles.top = coord + 'px';
            } else {
                coord = this._getRelativeYFromY(this.lastUserCellTop);
                gradeItemHeadingContainerStyles.top = coord + 'px';
                userColumnHeaderStyles.top = coord + 'px';
            }
        } else {
            headerFloats = false;
            coord = this._getRelativeYFromY(this.headerRowTop);
            gradeItemHeadingContainerStyles.top = coord + 'px';
            userColumnHeaderStyles.top = coord + 'px';
        }

        // User column position.

        if (window.right_to_left()) {
            floatingUserTriggerPoint = Y.config.win.innerWidth + Y.config.win.pageXOffset - this.dockWidth;
            floatingUserRelativePoint = floatingUserTriggerPoint - this.firstUserCellWidth - bodyMargin;
            userFloats = floatingUserTriggerPoint < (this.firstUserCellLeft + this.firstUserCellWidth + bodyMargin);
            leftTitleFloats = (floatingUserTriggerPoint - this.firstNonUserCellWidth) <
                              (this.firstNonUserCellLeft + this.firstUserCellWidth);
        } else {
            floatingUserRelativePoint = Y.config.win.pageXOffset + bodyMargin;
            floatingUserTriggerPoint = floatingUserRelativePoint + this.dockWidth + bodyMargin;
            userFloats = floatingUserTriggerPoint > this.firstUserCellLeft + bodyMargin;
            leftTitleFloats = floatingUserTriggerPoint > (this.firstNonUserCellLeft - this.firstUserCellWidth);
        }

        if (userFloats) {
            coord = this._getRelativeXFromX(floatingUserRelativePoint);
            userColumnStyles.left = coord + 'px';
            userColumnHeaderStyles.left = coord + 'px';
        } else {
            coord = this._getRelativeXFromX(this.firstUserCellLeft);
            userColumnStyles.left = coord + 'px';
            userColumnHeaderStyles.left = coord + 'px';
        }

        // Update the miscellaneous left-only floats.
        Y.Object.each(this.floatingHeaderRow, function(origin, key) {
            floatingHeaderStyles[key] = {
                left: userColumnStyles.left
            };
        }, this);

        // Update footer.
        if (this.footerRow) {
            footerStyles.left = this._getRelativeXFromX(this.headerRow.getX());

            // Determine whether the footer should now be shown as sticky.
            var pageHeight = Y.config.win.innerHeight,
                pageOffset = Y.config.win.pageYOffset,
                bottomScrollPosition = pageHeight - this._getScrollBarHeight() + pageOffset,
                footerRowHeight = parseInt(this.footerRow.getComputedStyle(HEIGHT), 10),
                footerBottomPosition = footerRowHeight + this.footerRowPosition;

            floatingFooterTitleStyles = floatingHeaderStyles[SELECTORS.FOOTERTITLE];
            floatingFooterTitleRow = this.floatingHeaderRow[SELECTORS.FOOTERTITLE];
            if (bottomScrollPosition < footerBottomPosition && bottomScrollPosition > this.firstUserCellBottom) {
                // We have not scrolled below the footer, nor above the first row.
                footerStyles.bottom = Math.ceil(footerBottomPosition - bottomScrollPosition) + 'px';
                footerFloats = true;
            } else {
                // The footer should not float any more.
                footerStyles.bottom = '1px';
                footerFloats = false;
            }
            if (floatingFooterTitleStyles) {
                floatingFooterTitleStyles.bottom = footerStyles.bottom;
                floatingFooterTitleStyles.top = null;
            }
            floatingHeaderStyles[SELECTORS.FOOTERTITLE] = floatingFooterTitleStyles;
        }

        // Apply the styles and mark elements as floating, or not.
        if (this.gradeItemHeadingContainer) {
            this.gradeItemHeadingContainer.setStyles(gradeItemHeadingContainerStyles);
            if (headerFloats) {
                this.gradeItemHeadingContainer.addClass(CSS.FLOATING);
            } else {
                this.gradeItemHeadingContainer.removeClass(CSS.FLOATING);
            }
        }
        if (this.userColumnHeader) {
            this.userColumnHeader.setStyles(userColumnHeaderStyles);
            if (userFloats) {
                this.userColumnHeader.addClass(CSS.FLOATING);
            } else {
                this.userColumnHeader.removeClass(CSS.FLOATING);
            }
        }
        if (this.userColumn) {
            this.userColumn.setStyles(userColumnStyles);
            if (userFloats) {
                this.userColumn.addClass(CSS.FLOATING);
            } else {
                this.userColumn.removeClass(CSS.FLOATING);
            }
        }
        if (this.footerRow) {
            this.footerRow.setStyles(footerStyles);
            if (footerFloats) {
                this.footerRow.addClass(CSS.FLOATING);
            } else {
                this.footerRow.removeClass(CSS.FLOATING);
            }
        }

        // And apply the styles to the generic left headers.
        Y.Object.each(floatingHeaderStyles, function(styles, key) {
            if (this.floatingHeaderRow[key]) {
                this.floatingHeaderRow[key].setStyles(styles);
            }
        }, this);


        Y.Object.each(this.floatingHeaderRow, function(value, key) {
            if (this.floatingHeaderRow[key]) {
                if (leftTitleFloats) {
                    this.floatingHeaderRow[key].addClass(CSS.FLOATING);
                } else {
                    this.floatingHeaderRow[key].removeClass(CSS.FLOATING);
                }
            }
        }, this);

        // The footer title has a more specific float setting.
        if (floatingFooterTitleRow) {
            if (leftTitleFloats) {
                floatingFooterTitleRow.addClass(CSS.FLOATING);
            } else {
                floatingFooterTitleRow.removeClass(CSS.FLOATING);
            }
        }

    },

    /**
     * Process a size change Event on the window.
     *
     * @method _handleResizeEvent
     * @protected
     */
    _handleResizeEvent: function() {
        // Recalculate the position of the edge cells for scroll positioning.
        this._calculateCellPositions();

        // Simulate a scroll.
        this._handleScrollEvent();

        // Resize user cells.
        var userWidth = this.firstUserCell.getComputedStyle(WIDTH);
        var userCells = Y.all(SELECTORS.USERCELL);
        this.userColumnHeader.one('.cell').setStyle('width', userWidth);
        this.userColumn.all('.cell').each(function(cell, idx) {
            var height = userCells.item(idx).getComputedStyle(HEIGHT);
            // Nasty hack to account for Internet Explorer
            if (Y.UA.ie !== 0) {
                var node = userCells.item(idx);
                var allHeight = node.getDOMNode ?
                    node.getDOMNode().getBoundingClientRect().height :
                    node.get('offsetHeight');
                var marginHeight = parseInt(node.getComputedStyle('marginTop'), 10) +
                    parseInt(node.getComputedStyle('marginBottom'), 10);
                var paddingHeight = parseInt(node.getComputedStyle('paddingTop'), 10) +
                    parseInt(node.getComputedStyle('paddingBottom'), 10);
                var borderHeight = parseInt(node.getComputedStyle('borderTopWidth'), 10) +
                    parseInt(node.getComputedStyle('borderBottomWidth'), 10);
                height = allHeight - marginHeight - paddingHeight - borderHeight;
            }
            cell.setStyles({
                width: userWidth,
                height: height
            });
        }, this);

        // Resize headers & footers.
        // This is an expensive operation, not expected to happen often.
        var headers = this.gradeItemHeadingContainer.all('.cell');
        var resizedcells = Y.all(SELECTORS.HEADERCELLS);

        var headeroffsetleft = this.headerRow.getX();
        var newcontainerwidth = 0;
        resizedcells.each(function(cell, idx) {
            var headercell = headers.item(idx);

            newcontainerwidth += cell.get(OFFSETWIDTH);
            var styles = {
                width: cell.getComputedStyle(WIDTH),
                left: cell.getX() - headeroffsetleft + 'px'
            };
            headercell.setStyles(styles);
        });

        if (this.footerRow) {
            var footers = this.footerRow.all('.cell');
            if (footers.size() !== 0) {
                var resizedavgcells = Y.all(SELECTORS.FOOTERCELLS);

                resizedavgcells.each(function(cell, idx) {
                    var footercell = footers.item(idx);
                    var styles = {
                        width: cell.getComputedStyle(WIDTH),
                        left: cell.getX() - headeroffsetleft + 'px'
                    };
                    footercell.setStyles(styles);
                });
            }
        }

        // Resize the title areas too.
        Y.Object.each(this.floatingHeaderRow, function(row) {
            row.one('div').setStyle('width', userWidth);
        }, this);

        this.gradeItemHeadingContainer.setStyle('width', newcontainerwidth);
    }

};

Y.Base.mix(Y.M.gradereport_grader.ReportTable, [FloatingHeaders]);
