/*! Scroller 2.0.6
 * ©2011-2022 SpryMedia Ltd - datatables.net/license
 */

/**
 * @summary     Scroller
 * @description Virtual rendering for DataTables
 * @version     2.0.6
 * @author      SpryMedia Ltd (www.sprymedia.co.uk)
 * @contact     www.sprymedia.co.uk/contact
 * @copyright   SpryMedia Ltd.
 *
 * This source file is free software, available under the following license:
 *   MIT license - http://datatables.net/license/mit
 *
 * This source file 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 license files for details.
 *
 * For details please refer to: http://www.datatables.net
 */

(function(factory) {
    if (typeof define === 'function' && define.amd) {
        // AMD
        define(['jquery', 'datatables.net'], function($) {
            return factory($, window, document);
        });
    } else if (typeof exports === 'object') {
        // CommonJS
        module.exports = function(root, $) {
            if (!root) {
                root = window;
            }

            if (!$ || !$.fn.dataTable) {
                $ = require('datatables.net')(root, $).$;
            }

            return factory($, root, root.document);
        };
    } else {
        // Browser
        factory(jQuery, window, document);
    }
}(function($, window, document, undefined) {
    'use strict';
    var DataTable = $.fn.dataTable;


    /**
     * Scroller is a virtual rendering plug-in for DataTables which allows large
     * datasets to be drawn on screen every quickly. What the virtual rendering means
     * is that only the visible portion of the table (and a bit to either side to make
     * the scrolling smooth) is drawn, while the scrolling container gives the
     * visual impression that the whole table is visible. This is done by making use
     * of the pagination abilities of DataTables and moving the table around in the
     * scrolling container DataTables adds to the page. The scrolling container is
     * forced to the height it would be for the full table display using an extra
     * element.
     *
     * Note that rows in the table MUST all be the same height. Information in a cell
     * which expands on to multiple lines will cause some odd behaviour in the scrolling.
     *
     * Scroller is initialised by simply including the letter 'S' in the sDom for the
     * table you want to have this feature enabled on. Note that the 'S' must come
     * AFTER the 't' parameter in `dom`.
     *
     * Key features include:
     *   <ul class="limit_length">
     *     <li>Speed! The aim of Scroller for DataTables is to make rendering large data sets fast</li>
     *     <li>Full compatibility with deferred rendering in DataTables for maximum speed</li>
     *     <li>Display millions of rows</li>
     *     <li>Integration with state saving in DataTables (scrolling position is saved)</li>
     *     <li>Easy to use</li>
     *   </ul>
     *
     *  @class
     *  @constructor
     *  @global
     *  @param {object} dt DataTables settings object or API instance
     *  @param {object} [opts={}] Configuration object for Scroller. Options 
     *    are defined by {@link Scroller.defaults}
     *
     *  @requires jQuery 1.7+
     *  @requires DataTables 1.10.0+
     *
     *  @example
     *    $(document).ready(function() {
     *        $('#example').DataTable( {
     *            "scrollY": "200px",
     *            "ajax": "media/dataset/large.txt",
     *            "scroller": true,
     *            "deferRender": true
     *        } );
     *    } );
     */
    var Scroller = function(dt, opts) {
        /* Sanity check - you just know it will happen */
        if (!(this instanceof Scroller)) {
            alert("Scroller warning: Scroller must be initialised with the 'new' keyword.");
            return;
        }

        if (opts === undefined) {
            opts = {};
        }

        var dtApi = $.fn.dataTable.Api(dt);

        /**
         * Settings object which contains customisable information for the Scroller instance
         * @namespace
         * @private
         * @extends Scroller.defaults
         */
        this.s = {
            /**
             * DataTables settings object
             *  @type     object
             *  @default  Passed in as first parameter to constructor
             */
            dt: dtApi.settings()[0],

            /**
             * DataTables API instance
             *  @type     DataTable.Api
             */
            dtApi: dtApi,

            /**
             * Pixel location of the top of the drawn table in the viewport
             *  @type     int
             *  @default  0
             */
            tableTop: 0,

            /**
             * Pixel location of the bottom of the drawn table in the viewport
             *  @type     int
             *  @default  0
             */
            tableBottom: 0,

            /**
             * Pixel location of the boundary for when the next data set should be loaded and drawn
             * when scrolling up the way.
             *  @type     int
             *  @default  0
             *  @private
             */
            redrawTop: 0,

            /**
             * Pixel location of the boundary for when the next data set should be loaded and drawn
             * when scrolling down the way. Note that this is actually calculated as the offset from
             * the top.
             *  @type     int
             *  @default  0
             *  @private
             */
            redrawBottom: 0,

            /**
             * Auto row height or not indicator
             *  @type     bool
             *  @default  0
             */
            autoHeight: true,

            /**
             * Number of rows calculated as visible in the visible viewport
             *  @type     int
             *  @default  0
             */
            viewportRows: 0,

            /**
             * setTimeout reference for state saving, used when state saving is enabled in the DataTable
             * and when the user scrolls the viewport in order to stop the cookie set taking too much
             * CPU!
             *  @type     int
             *  @default  0
             */
            stateTO: null,

            stateSaveThrottle: function() {},

            /**
             * setTimeout reference for the redraw, used when server-side processing is enabled in the
             * DataTables in order to prevent DoSing the server
             *  @type     int
             *  @default  null
             */
            drawTO: null,

            heights: {
                jump: null,
                page: null,
                virtual: null,
                scroll: null,

                /**
                 * Height of rows in the table
                 *  @type     int
                 *  @default  0
                 */
                row: null,

                /**
                 * Pixel height of the viewport
                 *  @type     int
                 *  @default  0
                 */
                viewport: null,
                labelHeight: 0,
                xbar: 0
            },

            topRowFloat: 0,
            scrollDrawDiff: null,
            loaderVisible: false,
            forceReposition: false,
            baseRowTop: 0,
            baseScrollTop: 0,
            mousedown: false,
            lastScrollTop: 0
        };

        // @todo The defaults should extend a `c` property and the internal settings
        // only held in the `s` property. At the moment they are mixed
        this.s = $.extend(this.s, Scroller.oDefaults, opts);

        // Workaround for row height being read from height object (see above comment)
        this.s.heights.row = this.s.rowHeight;

        /**
         * DOM elements used by the class instance
         * @private
         * @namespace
         *
         */
        this.dom = {
            "force": document.createElement('div'),
            "label": $('<div class="dts_label">0</div>'),
            "scroller": null,
            "table": null,
            "loader": null
        };

        // Attach the instance to the DataTables instance so it can be accessed in
        // future. Don't initialise Scroller twice on the same table
        if (this.s.dt.oScroller) {
            return;
        }

        this.s.dt.oScroller = this;

        /* Let's do it */
        this.construct();
    };



    $.extend(Scroller.prototype, {
        /* * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * *
         * Public methods - to be exposed via the DataTables API
         */

        /**
         * Calculate and store information about how many rows are to be displayed
         * in the scrolling viewport, based on current dimensions in the browser's
         * rendering. This can be particularly useful if the table is initially
         * drawn in a hidden element - for example in a tab.
         *  @param {bool} [redraw=true] Redraw the table automatically after the recalculation, with
         *    the new dimensions forming the basis for the draw.
         *  @returns {void}
         */
        measure: function(redraw) {
            if (this.s.autoHeight) {
                this._calcRowHeight();
            }

            var heights = this.s.heights;

            if (heights.row) {
                heights.viewport = this._parseHeight($(this.dom.scroller).css('max-height'));

                this.s.viewportRows = parseInt(heights.viewport / heights.row, 10) + 1;
                this.s.dt._iDisplayLength = this.s.viewportRows * this.s.displayBuffer;
            }

            var label = this.dom.label.outerHeight();

            heights.xbar = this.dom.scroller.offsetHeight - this.dom.scroller.clientHeight;
            heights.labelHeight = label;

            if (redraw === undefined || redraw) {
                this.s.dt.oInstance.fnDraw(false);
            }
        },

        /**
         * Get information about current displayed record range. This corresponds to
         * the information usually displayed in the "Info" block of the table.
         *
         * @returns {object} info as an object:
         *  {
         *      start: {int}, // the 0-indexed record at the top of the viewport
         *      end:   {int}, // the 0-indexed record at the bottom of the viewport
         *  }
         */
        pageInfo: function() {
            var
                dt = this.s.dt,
                iScrollTop = this.dom.scroller.scrollTop,
                iTotal = dt.fnRecordsDisplay(),
                iPossibleEnd = Math.ceil(this.pixelsToRow(iScrollTop + this.s.heights.viewport, false, this.s.ani));

            return {
                start: Math.floor(this.pixelsToRow(iScrollTop, false, this.s.ani)),
                end: iTotal < iPossibleEnd ? iTotal - 1 : iPossibleEnd - 1
            };
        },

        /**
         * Calculate the row number that will be found at the given pixel position
         * (y-scroll).
         *
         * Please note that when the height of the full table exceeds 1 million
         * pixels, Scroller switches into a non-linear mode for the scrollbar to fit
         * all of the records into a finite area, but this function returns a linear
         * value (relative to the last non-linear positioning).
         *  @param {int} pixels Offset from top to calculate the row number of
         *  @param {int} [intParse=true] If an integer value should be returned
         *  @param {int} [virtual=false] Perform the calculations in the virtual domain
         *  @returns {int} Row index
         */
        pixelsToRow: function(pixels, intParse, virtual) {
            var diff = pixels - this.s.baseScrollTop;
            var row = virtual ?
                (this._domain('physicalToVirtual', this.s.baseScrollTop) + diff) / this.s.heights.row :
                (diff / this.s.heights.row) + this.s.baseRowTop;

            return intParse || intParse === undefined ?
                parseInt(row, 10) :
                row;
        },

        /**
         * Calculate the pixel position from the top of the scrolling container for
         * a given row
         *  @param {int} iRow Row number to calculate the position of
         *  @returns {int} Pixels
         */
        rowToPixels: function(rowIdx, intParse, virtual) {
            var pixels;
            var diff = rowIdx - this.s.baseRowTop;

            if (virtual) {
                pixels = this._domain('virtualToPhysical', this.s.baseScrollTop);
                pixels += diff * this.s.heights.row;
            } else {
                pixels = this.s.baseScrollTop;
                pixels += diff * this.s.heights.row;
            }

            return intParse || intParse === undefined ?
                parseInt(pixels, 10) :
                pixels;
        },


        /**
         * Calculate the row number that will be found at the given pixel position (y-scroll)
         *  @param {int} row Row index to scroll to
         *  @param {bool} [animate=true] Animate the transition or not
         *  @returns {void}
         */
        scrollToRow: function(row, animate) {
            var that = this;
            var ani = false;
            var px = this.rowToPixels(row);

            // We need to know if the table will redraw or not before doing the
            // scroll. If it will not redraw, then we need to use the currently
            // displayed table, and scroll with the physical pixels. Otherwise, we
            // need to calculate the table's new position from the virtual
            // transform.
            var preRows = ((this.s.displayBuffer - 1) / 2) * this.s.viewportRows;
            var drawRow = row - preRows;
            if (drawRow < 0) {
                drawRow = 0;
            }

            if ((px > this.s.redrawBottom || px < this.s.redrawTop) && this.s.dt._iDisplayStart !== drawRow) {
                ani = true;
                px = this._domain('virtualToPhysical', row * this.s.heights.row);

                // If we need records outside the current draw region, but the new
                // scrolling position is inside that (due to the non-linear nature
                // for larger numbers of records), we need to force position update.
                if (this.s.redrawTop < px && px < this.s.redrawBottom) {
                    this.s.forceReposition = true;
                    animate = false;
                }
            }

            if (animate === undefined || animate) {
                this.s.ani = ani;
                $(this.dom.scroller).animate({
                    "scrollTop": px
                }, function() {
                    // This needs to happen after the animation has completed and
                    // the final scroll event fired
                    setTimeout(function() {
                        that.s.ani = false;
                    }, 250);
                });
            } else {
                $(this.dom.scroller).scrollTop(px);
            }
        },


        /* * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * *
         * Constructor
         */

        /**
         * Initialisation for Scroller
         *  @returns {void}
         *  @private
         */
        construct: function() {
            var that = this;
            var dt = this.s.dtApi;

            /* Sanity check */
            if (!this.s.dt.oFeatures.bPaginate) {
                this.s.dt.oApi._fnLog(this.s.dt, 0, 'Pagination must be enabled for Scroller');
                return;
            }

            /* Insert a div element that we can use to force the DT scrolling container to
             * the height that would be required if the whole table was being displayed
             */
            this.dom.force.style.position = "relative";
            this.dom.force.style.top = "0px";
            this.dom.force.style.left = "0px";
            this.dom.force.style.width = "1px";

            this.dom.scroller = $('div.' + this.s.dt.oClasses.sScrollBody, this.s.dt.nTableWrapper)[0];
            this.dom.scroller.appendChild(this.dom.force);
            this.dom.scroller.style.position = "relative";

            this.dom.table = $('>table', this.dom.scroller)[0];
            this.dom.table.style.position = "absolute";
            this.dom.table.style.top = "0px";
            this.dom.table.style.left = "0px";

            // Add class to 'announce' that we are a Scroller table
            $(dt.table().container()).addClass('dts DTS');

            // Add a 'loading' indicator
            if (this.s.loadingIndicator) {
                this.dom.loader = $('<div class="dataTables_processing dts_loading">' + this.s.dt.oLanguage.sLoadingRecords + '</div>')
                    .css('display', 'none');

                $(this.dom.scroller.parentNode)
                    .css('position', 'relative')
                    .append(this.dom.loader);
            }

            this.dom.label.appendTo(this.dom.scroller);

            /* Initial size calculations */
            if (this.s.heights.row && this.s.heights.row != 'auto') {
                this.s.autoHeight = false;
            }

            // Scrolling callback to see if a page change is needed
            this.s.ingnoreScroll = true;
            $(this.dom.scroller).on('scroll.dt-scroller', function(e) {
                that._scroll.call(that);
            });

            // In iOS we catch the touchstart event in case the user tries to scroll
            // while the display is already scrolling
            $(this.dom.scroller).on('touchstart.dt-scroller', function() {
                that._scroll.call(that);
            });

            $(this.dom.scroller)
                .on('mousedown.dt-scroller', function() {
                    that.s.mousedown = true;
                })
                .on('mouseup.dt-scroller', function() {
                    that.s.labelVisible = false;
                    that.s.mousedown = false;
                    that.dom.label.css('display', 'none');
                });

            // On resize, update the information element, since the number of rows shown might change
            $(window).on('resize.dt-scroller', function() {
                that.measure(false);
                that._info();
            });

            // Add a state saving parameter to the DT state saving so we can restore the exact
            // position of the scrolling.
            var initialStateSave = true;
            var loadedState = dt.state.loaded();

            dt.on('stateSaveParams.scroller', function(e, settings, data) {
                if (initialStateSave && loadedState) {
                    data.scroller = loadedState.scroller;
                    initialStateSave = false;
                    that.s.lastScrollTop = data.scroller.scrollTop;
                } else {
                    // Need to used the saved position on init
                    data.scroller = {
                        topRow: that.s.topRowFloat,
                        baseScrollTop: that.s.baseScrollTop,
                        baseRowTop: that.s.baseRowTop,
                        scrollTop: that.s.lastScrollTop
                    };
                }
            });

            dt.on('stateLoadParams.scroller', function(e, settings, data) {
                if (data.scroller !== undefined) {
                    that.scrollToRow(data.scroller.topRow);
                }
            });

            if (loadedState && loadedState.scroller) {
                this.s.topRowFloat = loadedState.scroller.topRow;
                this.s.baseScrollTop = loadedState.scroller.baseScrollTop;
                this.s.baseRowTop = loadedState.scroller.baseRowTop;
            }

            this.measure(false);

            that.s.stateSaveThrottle = that.s.dt.oApi._fnThrottle(function() {
                that.s.dtApi.state.save();
            }, 500);

            dt.on('init.scroller', function() {
                that.measure(false);

                // Setting to `jump` will instruct _draw to calculate the scroll top
                // position
                that.s.scrollType = 'jump';
                that._draw();

                // Update the scroller when the DataTable is redrawn
                dt.on('draw.scroller', function() {
                    that._draw();
                });
            });

            // Set height before the draw happens, allowing everything else to update
            // on draw complete without worry for roder.
            dt.on('preDraw.dt.scroller', function() {
                that._scrollForce();
            });

            // Destructor
            dt.on('destroy.scroller', function() {
                $(window).off('resize.dt-scroller');
                $(that.dom.scroller).off('.dt-scroller');
                $(that.s.dt.nTable).off('.scroller');

                $(that.s.dt.nTableWrapper).removeClass('DTS');
                $('div.DTS_Loading', that.dom.scroller.parentNode).remove();

                that.dom.table.style.position = "";
                that.dom.table.style.top = "";
                that.dom.table.style.left = "";
            });
        },


        /* * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * *
         * Private methods
         */

        /**
         * Automatic calculation of table row height. This is just a little tricky here as using
         * initialisation DataTables has tale the table out of the document, so we need to create
         * a new table and insert it into the document, calculate the row height and then whip the
         * table out.
         *  @returns {void}
         *  @private
         */
        _calcRowHeight: function() {
            var dt = this.s.dt;
            var origTable = dt.nTable;
            var nTable = origTable.cloneNode(false);
            var tbody = $('<tbody/>').appendTo(nTable);
            var container = $(
                '<div class="' + dt.oClasses.sWrapper + ' DTS">' +
                '<div class="' + dt.oClasses.sScrollWrapper + '">' +
                '<div class="' + dt.oClasses.sScrollBody + '"></div>' +
                '</div>' +
                '</div>'
            );

            // Want 3 rows in the sizing table so :first-child and :last-child
            // CSS styles don't come into play - take the size of the middle row
            $('tbody tr:lt(4)', origTable).clone().appendTo(tbody);
            var rowsCount = $('tr', tbody).length;

            if (rowsCount === 1) {
                tbody.prepend('<tr><td>&#160;</td></tr>');
                tbody.append('<tr><td>&#160;</td></tr>');
            } else {
                for (; rowsCount < 3; rowsCount++) {
                    tbody.append('<tr><td>&#160;</td></tr>');
                }
            }

            $('div.' + dt.oClasses.sScrollBody, container).append(nTable);

            // If initialised using `dom`, use the holding element as the insert point
            var insertEl = this.s.dt.nHolding || origTable.parentNode;

            if (!$(insertEl).is(':visible')) {
                insertEl = 'body';
            }

            // Remove form element links as they might select over others (particularly radio and checkboxes)
            container.find("input").removeAttr("name");

            container.appendTo(insertEl);
            this.s.heights.row = $('tr', tbody).eq(1).outerHeight();

            container.remove();
        },

        /**
         * Draw callback function which is fired when the DataTable is redrawn. The main function of
         * this method is to position the drawn table correctly the scrolling container for the rows
         * that is displays as a result of the scrolling position.
         *  @returns {void}
         *  @private
         */
        _draw: function() {
            var
                that = this,
                heights = this.s.heights,
                iScrollTop = this.dom.scroller.scrollTop,
                iTableHeight = $(this.s.dt.nTable).height(),
                displayStart = this.s.dt._iDisplayStart,
                displayLen = this.s.dt._iDisplayLength,
                displayEnd = this.s.dt.fnRecordsDisplay();

            // Disable the scroll event listener while we are updating the DOM
            this.s.skip = true;

            // If paging is reset
            if ((this.s.dt.bSorted || this.s.dt.bFiltered) && displayStart === 0 && !this.s.dt._drawHold) {
                this.s.topRowFloat = 0;
            }

            iScrollTop = this.s.scrollType === 'jump' ?
                this._domain('virtualToPhysical', this.s.topRowFloat * heights.row) :
                iScrollTop;

            // Store positional information so positional calculations can be based
            // upon the current table draw position
            this.s.baseScrollTop = iScrollTop;
            this.s.baseRowTop = this.s.topRowFloat;

            // Position the table in the virtual scroller
            var tableTop = iScrollTop - ((this.s.topRowFloat - displayStart) * heights.row);
            if (displayStart === 0) {
                tableTop = 0;
            } else if (displayStart + displayLen >= displayEnd) {
                tableTop = heights.scroll - iTableHeight;
            }

            this.dom.table.style.top = tableTop + 'px';

            /* Cache some information for the scroller */
            this.s.tableTop = tableTop;
            this.s.tableBottom = iTableHeight + this.s.tableTop;

            // Calculate the boundaries for where a redraw will be triggered by the
            // scroll event listener
            var boundaryPx = (iScrollTop - this.s.tableTop) * this.s.boundaryScale;
            this.s.redrawTop = iScrollTop - boundaryPx;
            this.s.redrawBottom = iScrollTop + boundaryPx > heights.scroll - heights.viewport - heights.row ?
                heights.scroll - heights.viewport - heights.row :
                iScrollTop + boundaryPx;

            this.s.skip = false;

            if (that.s.ingnoreScroll) {
                // Restore the scrolling position that was saved by DataTable's state
                // saving Note that this is done on the second draw when data is Ajax
                // sourced, and the first draw when DOM soured
                if (this.s.dt.oFeatures.bStateSave && this.s.dt.oLoadedState !== null &&
                    typeof this.s.dt.oLoadedState.scroller != 'undefined') {
                    // A quirk of DataTables is that the draw callback will occur on an
                    // empty set if Ajax sourced, but not if server-side processing.
                    var ajaxSourced = (this.s.dt.sAjaxSource || that.s.dt.ajax) && !this.s.dt.oFeatures.bServerSide ?
                        true :
                        false;

                    if ((ajaxSourced && this.s.dt.iDraw >= 2) ||
                        (!ajaxSourced && this.s.dt.iDraw >= 1)) {
                        setTimeout(function() {
                            $(that.dom.scroller).scrollTop(that.s.dt.oLoadedState.scroller.scrollTop);

                            // In order to prevent layout thrashing we need another
                            // small delay
                            setTimeout(function() {
                                that.s.ingnoreScroll = false;
                            }, 0);
                        }, 0);
                    }
                } else {
                    that.s.ingnoreScroll = false;
                }
            }


            // Because of the order of the DT callbacks, the info update will
            // take precedence over the one we want here. So a 'thread' break is
            // needed.  Only add the thread break if bInfo is set
            if (this.s.dt.oFeatures.bInfo) {
                setTimeout(function() {
                    that._info.call(that);
                }, 0);
            }

            $(this.s.dt.nTable).triggerHandler('position.dts.dt', tableTop);

            // Hide the loading indicator
            if (this.dom.loader && this.s.loaderVisible) {
                this.dom.loader.css('display', 'none');
                this.s.loaderVisible = false;
            }
        },

        /**
         * Convert from one domain to another. The physical domain is the actual
         * pixel count on the screen, while the virtual is if we had browsers which
         * had scrolling containers of infinite height (i.e. the absolute value)
         *
         *  @param {string} dir Domain transform direction, `virtualToPhysical` or
         *    `physicalToVirtual` 
         *  @returns {number} Calculated transform
         *  @private
         */
        _domain: function(dir, val) {
            var heights = this.s.heights;
            var diff;
            var magic = 10000; // the point at which the non-linear calculations start to happen

            // If the virtual and physical height match, then we use a linear
            // transform between the two, allowing the scrollbar to be linear
            if (heights.virtual === heights.scroll) {
                return val;
            }

            // In the first 10k pixels and the last 10k pixels, we want the scrolling
            // to be linear. After that it can be non-linear. It would be unusual for
            // anyone to mouse wheel through that much.
            if (val < magic) {
                return val;
            } else if (dir === 'virtualToPhysical' && val >= heights.virtual - magic) {
                diff = heights.virtual - val;
                return heights.scroll - diff;
            } else if (dir === 'physicalToVirtual' && val >= heights.scroll - magic) {
                diff = heights.scroll - val;
                return heights.virtual - diff;
            }

            // Otherwise, we want a non-linear scrollbar to take account of the
            // redrawing regions at the start and end of the table, otherwise these
            // can stutter badly - on large tables 30px (for example) scroll might
            // be hundreds of rows, so the table would be redrawing every few px at
            // the start and end. Use a simple linear eq. to stop this, effectively
            // causing a kink in the scrolling ratio. It does mean the scrollbar is
            // non-linear, but with such massive data sets, the scrollbar is going
            // to be a best guess anyway
            var m = (heights.virtual - magic - magic) / (heights.scroll - magic - magic);
            var c = magic - (m * magic);

            return dir === 'virtualToPhysical' ?
                (val - c) / m :
                (m * val) + c;
        },

        /**
         * Update any information elements that are controlled by the DataTable based on the scrolling
         * viewport and what rows are visible in it. This function basically acts in the same way as
         * _fnUpdateInfo in DataTables, and effectively replaces that function.
         *  @returns {void}
         *  @private
         */
        _info: function() {
            if (!this.s.dt.oFeatures.bInfo) {
                return;
            }

            var
                dt = this.s.dt,
                language = dt.oLanguage,
                iScrollTop = this.dom.scroller.scrollTop,
                iStart = Math.floor(this.pixelsToRow(iScrollTop, false, this.s.ani) + 1),
                iMax = dt.fnRecordsTotal(),
                iTotal = dt.fnRecordsDisplay(),
                iPossibleEnd = Math.ceil(this.pixelsToRow(iScrollTop + this.s.heights.viewport, false, this.s.ani)),
                iEnd = iTotal < iPossibleEnd ? iTotal : iPossibleEnd,
                sStart = dt.fnFormatNumber(iStart),
                sEnd = dt.fnFormatNumber(iEnd),
                sMax = dt.fnFormatNumber(iMax),
                sTotal = dt.fnFormatNumber(iTotal),
                sOut;

            if (dt.fnRecordsDisplay() === 0 &&
                dt.fnRecordsDisplay() == dt.fnRecordsTotal()) {
                /* Empty record set */
                sOut = language.sInfoEmpty + language.sInfoPostFix;
            } else if (dt.fnRecordsDisplay() === 0) {
                /* Empty record set after filtering */
                sOut = language.sInfoEmpty + ' ' +
                    language.sInfoFiltered.replace('_MAX_', sMax) +
                    language.sInfoPostFix;
            } else if (dt.fnRecordsDisplay() == dt.fnRecordsTotal()) {
                /* Normal record set */
                sOut = language.sInfo.
                replace('_START_', sStart).
                replace('_END_', sEnd).
                replace('_MAX_', sMax).
                replace('_TOTAL_', sTotal) +
                    language.sInfoPostFix;
            } else {
                /* Record set after filtering */
                sOut = language.sInfo.
                replace('_START_', sStart).
                replace('_END_', sEnd).
                replace('_MAX_', sMax).
                replace('_TOTAL_', sTotal) + ' ' +
                    language.sInfoFiltered.replace(
                        '_MAX_',
                        dt.fnFormatNumber(dt.fnRecordsTotal())
                    ) +
                    language.sInfoPostFix;
            }

            var callback = language.fnInfoCallback;
            if (callback) {
                sOut = callback.call(dt.oInstance,
                    dt, iStart, iEnd, iMax, iTotal, sOut
                );
            }

            var n = dt.aanFeatures.i;
            if (typeof n != 'undefined') {
                for (var i = 0, iLen = n.length; i < iLen; i++) {
                    $(n[i]).html(sOut);
                }
            }

            // DT doesn't actually (yet) trigger this event, but it will in future
            $(dt.nTable).triggerHandler('info.dt');
        },

        /**
         * Parse CSS height property string as number
         *
         * An attempt is made to parse the string as a number. Currently supported units are 'px',
         * 'vh', and 'rem'. 'em' is partially supported; it works as long as the parent element's
         * font size matches the body element. Zero is returned for unrecognized strings.
         *  @param {string} cssHeight CSS height property string
         *  @returns {number} height
         *  @private
         */
        _parseHeight: function(cssHeight) {
            var height;
            var matches = /^([+-]?(?:\d+(?:\.\d+)?|\.\d+))(px|em|rem|vh)$/.exec(cssHeight);

            if (matches === null) {
                return 0;
            }

            var value = parseFloat(matches[1]);
            var unit = matches[2];

            if (unit === 'px') {
                height = value;
            } else if (unit === 'vh') {
                height = (value / 100) * $(window).height();
            } else if (unit === 'rem') {
                height = value * parseFloat($(':root').css('font-size'));
            } else if (unit === 'em') {
                height = value * parseFloat($('body').css('font-size'));
            }

            return height ?
                height :
                0;
        },

        /**
         * Scrolling function - fired whenever the scrolling position is changed.
         * This method needs to use the stored values to see if the table should be
         * redrawn as we are moving towards the end of the information that is
         * currently drawn or not. If needed, then it will redraw the table based on
         * the new position.
         *  @returns {void}
         *  @private
         */
        _scroll: function() {
            var
                that = this,
                heights = this.s.heights,
                iScrollTop = this.dom.scroller.scrollTop,
                iTopRow;

            if (this.s.skip) {
                return;
            }

            if (this.s.ingnoreScroll) {
                return;
            }

            if (iScrollTop === this.s.lastScrollTop) {
                return;
            }

            /* If the table has been sorted or filtered, then we use the redraw that
             * DataTables as done, rather than performing our own
             */
            if (this.s.dt.bFiltered || this.s.dt.bSorted) {
                this.s.lastScrollTop = 0;
                return;
            }

            /* Update the table's information display for what is now in the viewport */
            this._info();

            /* We don't want to state save on every scroll event - that's heavy
             * handed, so use a timeout to update the state saving only when the
             * scrolling has finished
             */
            clearTimeout(this.s.stateTO);
            this.s.stateTO = setTimeout(function() {
                that.s.dtApi.state.save();
            }, 250);

            this.s.scrollType = Math.abs(iScrollTop - this.s.lastScrollTop) > heights.viewport ?
                'jump' :
                'cont';

            this.s.topRowFloat = this.s.scrollType === 'cont' ?
                this.pixelsToRow(iScrollTop, false, false) :
                this._domain('physicalToVirtual', iScrollTop) / heights.row;

            if (this.s.topRowFloat < 0) {
                this.s.topRowFloat = 0;
            }

            /* Check if the scroll point is outside the trigger boundary which would required
             * a DataTables redraw
             */
            if (this.s.forceReposition || iScrollTop < this.s.redrawTop || iScrollTop > this.s.redrawBottom) {
                var preRows = Math.ceil(((this.s.displayBuffer - 1) / 2) * this.s.viewportRows);

                iTopRow = parseInt(this.s.topRowFloat, 10) - preRows;
                this.s.forceReposition = false;

                if (iTopRow <= 0) {
                    /* At the start of the table */
                    iTopRow = 0;
                } else if (iTopRow + this.s.dt._iDisplayLength > this.s.dt.fnRecordsDisplay()) {
                    /* At the end of the table */
                    iTopRow = this.s.dt.fnRecordsDisplay() - this.s.dt._iDisplayLength;
                    if (iTopRow < 0) {
                        iTopRow = 0;
                    }
                } else if (iTopRow % 2 !== 0) {
                    // For the row-striping classes (odd/even) we want only to start
                    // on evens otherwise the stripes will change between draws and
                    // look rubbish
                    iTopRow++;
                }

                // Store calcuated value, in case the following condition is not met, but so
                // that the draw function will still use it.
                this.s.targetTop = iTopRow;

                if (iTopRow != this.s.dt._iDisplayStart) {
                    /* Cache the new table position for quick lookups */
                    this.s.tableTop = $(this.s.dt.nTable).offset().top;
                    this.s.tableBottom = $(this.s.dt.nTable).height() + this.s.tableTop;

                    var draw = function() {
                        that.s.dt._iDisplayStart = that.s.targetTop;
                        that.s.dt.oApi._fnDraw(that.s.dt);
                    };

                    /* Do the DataTables redraw based on the calculated start point - note that when
                     * using server-side processing we introduce a small delay to not DoS the server...
                     */
                    if (this.s.dt.oFeatures.bServerSide) {
                        this.s.forceReposition = true;

                        clearTimeout(this.s.drawTO);
                        this.s.drawTO = setTimeout(draw, this.s.serverWait);
                    } else {
                        draw();
                    }

                    if (this.dom.loader && !this.s.loaderVisible) {
                        this.dom.loader.css('display', 'block');
                        this.s.loaderVisible = true;
                    }
                }
            } else {
                this.s.topRowFloat = this.pixelsToRow(iScrollTop, false, true);
            }

            this.s.lastScrollTop = iScrollTop;
            this.s.stateSaveThrottle();

            if (this.s.scrollType === 'jump' && this.s.mousedown) {
                this.s.labelVisible = true;
            }
            if (this.s.labelVisible) {
                var labelFactor = (heights.viewport - heights.labelHeight - heights.xbar) / heights.scroll;

                this.dom.label
                    .html(this.s.dt.fnFormatNumber(parseInt(this.s.topRowFloat, 10) + 1))
                    .css('top', iScrollTop + (iScrollTop * labelFactor))
                    .css('right', 10 - this.dom.scroller.scrollLeft)
                    .css('display', 'block');
            }
        },

        /**
         * Force the scrolling container to have height beyond that of just the
         * table that has been drawn so the user can scroll the whole data set.
         *
         * Note that if the calculated required scrolling height exceeds a maximum
         * value (1 million pixels - hard-coded) the forcing element will be set
         * only to that maximum value and virtual / physical domain transforms will
         * be used to allow Scroller to display tables of any number of records.
         *  @returns {void}
         *  @private
         */
        _scrollForce: function() {
            var heights = this.s.heights;
            var max = 1000000;

            heights.virtual = heights.row * this.s.dt.fnRecordsDisplay();
            heights.scroll = heights.virtual;

            if (heights.scroll > max) {
                heights.scroll = max;
            }

            // Minimum height so there is always a row visible (the 'no rows found'
            // if reduced to zero filtering)
            this.dom.force.style.height = heights.scroll > this.s.heights.row ?
                heights.scroll + 'px' :
                this.s.heights.row + 'px';
        }
    });



    /* * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * *
     * Statics
     * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * */


    /**
     * Scroller default settings for initialisation
     *  @namespace
     *  @name Scroller.defaults
     *  @static
     */
    Scroller.defaults = {
        /**
         * Scroller uses the boundary scaling factor to decide when to redraw the table - which it
         * typically does before you reach the end of the currently loaded data set (in order to
         * allow the data to look continuous to a user scrolling through the data). If given as 0
         * then the table will be redrawn whenever the viewport is scrolled, while 1 would not
         * redraw the table until the currently loaded data has all been shown. You will want
         * something in the middle - the default factor of 0.5 is usually suitable.
         *  @type     float
         *  @default  0.5
         *  @static
         */
        boundaryScale: 0.5,

        /**
         * The display buffer is what Scroller uses to calculate how many rows it should pre-fetch
         * for scrolling. Scroller automatically adjusts DataTables' display length to pre-fetch
         * rows that will be shown in "near scrolling" (i.e. just beyond the current display area).
         * The value is based upon the number of rows that can be displayed in the viewport (i.e.
         * a value of 1), and will apply the display range to records before before and after the
         * current viewport - i.e. a factor of 3 will allow Scroller to pre-fetch 1 viewport's worth
         * of rows before the current viewport, the current viewport's rows and 1 viewport's worth
         * of rows after the current viewport. Adjusting this value can be useful for ensuring
         * smooth scrolling based on your data set.
         *  @type     int
         *  @default  7
         *  @static
         */
        displayBuffer: 9,

        /**
         * Show (or not) the loading element in the background of the table. Note that you should
         * include the dataTables.scroller.css file for this to be displayed correctly.
         *  @type     boolean
         *  @default  false
         *  @static
         */
        loadingIndicator: false,

        /**
         * Scroller will attempt to automatically calculate the height of rows for it's internal
         * calculations. However the height that is used can be overridden using this parameter.
         *  @type     int|string
         *  @default  auto
         *  @static
         */
        rowHeight: "auto",

        /**
         * When using server-side processing, Scroller will wait a small amount of time to allow
         * the scrolling to finish before requesting more data from the server. This prevents
         * you from DoSing your own server! The wait time can be configured by this parameter.
         *  @type     int
         *  @default  200
         *  @static
         */
        serverWait: 200
    };

    Scroller.oDefaults = Scroller.defaults;



    /* * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * *
     * Constants
     * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * */

    /**
     * Scroller version
     *  @type      String
     *  @default   See code
     *  @name      Scroller.version
     *  @static
     */
    Scroller.version = "2.0.6";



    /* * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * *
     * Initialisation
     * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * */

    // Attach a listener to the document which listens for DataTables initialisation
    // events so we can automatically initialise
    $(document).on('preInit.dt.dtscroller', function(e, settings) {
        if (e.namespace !== 'dt') {
            return;
        }

        var init = settings.oInit.scroller;
        var defaults = DataTable.defaults.scroller;

        if (init || defaults) {
            var opts = $.extend({}, init, defaults);

            if (init !== false) {
                new Scroller(settings, opts);
            }
        }
    });


    // Attach Scroller to DataTables so it can be accessed as an 'extra'
    $.fn.dataTable.Scroller = Scroller;
    $.fn.DataTable.Scroller = Scroller;


    // DataTables 1.10 API method aliases
    let api = $.fn.dataTable.Api;

    Api.register('scroller()', function() {
        return this;
    });

    // Undocumented and deprecated - is it actually useful at all?
    Api.register('scroller().rowToPixels()', function(rowIdx, intParse, virtual) {
        var ctx = this.context;

        if (ctx.length && ctx[0].oScroller) {
            return ctx[0].oScroller.rowToPixels(rowIdx, intParse, virtual);
        }
        // undefined
    });

    // Undocumented and deprecated - is it actually useful at all?
    Api.register('scroller().pixelsToRow()', function(pixels, intParse, virtual) {
        var ctx = this.context;

        if (ctx.length && ctx[0].oScroller) {
            return ctx[0].oScroller.pixelsToRow(pixels, intParse, virtual);
        }
        // undefined
    });

    // `scroller().scrollToRow()` is undocumented and deprecated. Use `scroller.toPosition()
    Api.register(['scroller().scrollToRow()', 'scroller.toPosition()'], function(idx, ani) {
        this.iterator('table', function(ctx) {
            if (ctx.oScroller) {
                ctx.oScroller.scrollToRow(idx, ani);
            }
        });

        return this;
    });

    Api.register('row().scrollTo()', function(ani) {
        var that = this;

        this.iterator('row', function(ctx, rowIdx) {
            if (ctx.oScroller) {
                var displayIdx = that
                    .rows({ order: 'applied', search: 'applied' })
                    .indexes()
                    .indexOf(rowIdx);

                ctx.oScroller.scrollToRow(displayIdx, ani);
            }
        });

        return this;
    });

    Api.register('scroller.measure()', function(redraw) {
        this.iterator('table', function(ctx) {
            if (ctx.oScroller) {
                ctx.oScroller.measure(redraw);
            }
        });

        return this;
    });

    Api.register('scroller.page()', function() {
        var ctx = this.context;

        if (ctx.length && ctx[0].oScroller) {
            return ctx[0].oScroller.pageInfo();
        }
        // undefined
    });

    return Scroller;
}));