/**
 * Panoramic JavaScript Image Viewer (PanoJS) 1.0.2
 *
 * Generates a draggable and zoomable viewer for images that would
 * be otherwise too large for a browser window.  Examples would include
 * maps or high resolution document scans.
 *
 * Images must be precut into tiles, such as by the accompanying tilemaker.py
 * python library.
 *
 * <div class="viewer">
 *   <div class="well"><!-- --></div>
 *   <div class="surface"><!-- --></div>
 *   <div class="controls">
 *     <a href="#" class="zoomIn">+</a>
 *     <a href="#" class="zoomOut">-</a>
 *   </div>
 * </div>
 *
 * The "well" node is where generated IMG elements are appended. It
 * should have the CSS rule "overflow: hidden", to occlude image tiles
 * that have scrolled out of view.
 *
 * The "surface" node is the transparent mouse-responsive layer of the
 * image viewer, and should match the well in size.
 *
 * var viewerBean = new PanoJS(element, 'tiles', 256, 3, 1);
 *
 * To disable the image toolbar in IE, be sure to add the following:
 * <meta http-equiv="imagetoolbar" content="no" />
 *
 * Copyright (c) 2005 Michal Migurski <mike-gsv@teczno.com>
 *                    Dan Allen <dan.allen@mojavelinux.com>
 *
 * Redistribution and use in source form, with or without modification,
 * are permitted provided that the following conditions are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. The name of the author may not be used to endorse or promote products
 *    derived from this software without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 *
 * @author Michal Migurski <mike-gsv@teczno.com>
 * @author Dan Allen <dan.allen@mojavelinux.com>
 *
 * NOTE: if artifacts are appearing, then positions include half-pixels
 * TODO: additional jsdoc and package jsmin
 * TODO: Tile could be an object
 */
function PanoJS(viewer, options) {

    // listeners that are notified on a move (pan) event
    this.viewerMovedListeners = [];
    // listeners that are notified on a zoom event
    this.viewerZoomedListeners = [];

    if (typeof viewer == 'string') {
        this.viewer = document.getElementById(viewer);
    }
    else {
        this.viewer = viewer;
    }

    if (typeof options == 'undefined') {
        options = {};
    }

    this.tileUrlProvider = new PanoJS.TileUrlProvider(options.tileBaseUri, options.image);

    this.tileSize = (options.tileSize ? options.tileSize : PanoJS.TILE_SIZE);

    // assign and do some validation on the zoom levels to ensure sanity
    this.zoomLevel = (typeof options.initialZoom == 'undefined' ? -1 : parseInt(options.initialZoom));
    this.maxZoomLevel = (typeof options.maxZoom == 'undefined' ? 0 : Math.abs(parseInt(options.maxZoom)));
    if (this.zoomLevel > this.maxZoomLevel) {
        this.zoomLevel = this.maxZoomLevel;
    }

    this.imgsize = { 'x' : 0, 'y' : 0 };
    this.imgsize.x = (typeof options.imageWidth == 'undefined' ? -1 : parseInt(options.imageWidth));
    this.imgsize.y = (typeof options.imageHeight == 'undefined' ? -1 : parseInt(options.imageHeight));

    this.initialized = false;
    this.surface = null;
    this.well = null;
    this.width = 0;
    this.height = 0;
    this.top = 0;
    this.left = 0;
    this.x = 0;
    this.y = 0;
    this.border = -1;
    this.mark = { 'x' : 0, 'y' : 0 };
    this.pressed = false;
    this.tiles = [];
    this.cache = {};
    var blankTile = options.blankTile ? options.blankTile : PanoJS.BLANK_TILE_IMAGE;
    var loadingTile = options.loadingTile ? options.loadingTile : PanoJS.LOADING_TILE_IMAGE;
    this.cache['blank'] = new Image();
    this.cache['blank'].src = blankTile;
    if (blankTile != loadingTile) {
        this.cache['loading'] = new Image();
        this.cache['loading'].src = loadingTile;
    }
    else {
        this.cache['loading'] = this.cache['blank'];
    }

    // employed to throttle the number of redraws that
    // happen while the mouse is moving
    this.moveCount = 0;
    this.slideMonitor = 0;
    this.slideAcceleration = 0;

    // add to viewer registry
    PanoJS.VIEWERS[PanoJS.VIEWERS.length] = this;
}

// project specific variables
PanoJS.PROJECT_NAME = 'PanoJS';
PanoJS.PROJECT_VERSION = '1.0.0';
PanoJS.REVISION_FLAG = '';

// CSS definition settings
PanoJS.SURFACE_STYLE_CLASS = 'surface';
PanoJS.WELL_STYLE_CLASS = 'well';
PanoJS.CONTROLS_STYLE_CLASS = 'controls'
PanoJS.TILE_STYLE_CLASS = 'tile';

// language settings
PanoJS.MSG_BEYOND_MIN_ZOOM = 'Cannot zoom out past the current level.';
PanoJS.MSG_BEYOND_MAX_ZOOM = 'Cannot zoom in beyond the current level.';

// defaults if not provided as constructor options
PanoJS.TILE_BASE_URI = 'tiles';
PanoJS.TILE_PREFIX = 'tile-';
PanoJS.TILE_EXTENSION = 'jpg';
PanoJS.TILE_SIZE = 256;
PanoJS.BLANK_TILE_IMAGE = 'blank.gif';
PanoJS.LOADING_TILE_IMAGE = 'blank.gif';
PanoJS.INITIAL_PAN = { 'x' : .5, 'y' : .5 };
PanoJS.USE_LOADER_IMAGE = true;
PanoJS.USE_SLIDE = true;
PanoJS.USE_KEYBOARD = true;

// performance tuning variables
PanoJS.MOVE_THROTTLE = 3;
PanoJS.SLIDE_DELAY = 40;
PanoJS.SLIDE_ACCELERATION_FACTOR = 5;

// the following are calculated settings
PanoJS.DOM_ONLOAD = (navigator.userAgent.indexOf('KHTML') >= 0 ? false : true);
PanoJS.GRAB_MOUSE_CURSOR = (navigator.userAgent.search(/KHTML|Opera/i) >= 0 ? 'pointer' : (document.attachEvent ? 'url(grab.cur)' : '-moz-grab'));
PanoJS.GRABBING_MOUSE_CURSOR = (navigator.userAgent.search(/KHTML|Opera/i) >= 0 ? 'move' : (document.attachEvent ? 'url(grabbing.cur)' : '-moz-grabbing'));

// registry of all known viewers
PanoJS.VIEWERS = [];

// utility functions
PanoJS.isInstance = function(object, clazz) {
    // FIXME: can this just be replaced with instanceof operator? It has been reported that __proto__ is specific to Netscape
    while (object != null) {
        if (object == clazz.prototype) {
            return true;
        }

        object = object.__proto__;
    }

    return false;
}

PanoJS.prototype = {

    /**
     * Resize the viewer to fit snug inside the browser window (or frame),
     * spacing it from the edges by the specified border.
     *
     * This method should be called prior to init()
     * FIXME: option to hide viewer to prevent scrollbar interference
     */
    fitToWindow : function(border) {
        if (typeof border != 'number' || border < 0) {
            border = 0;
        }

        this.border = border;
        var calcWidth = 0;
        var calcHeight = 0;
        if (window.innerWidth) {
            calcWidth = window.innerWidth;
            calcHeight = window.innerHeight;
        }
        else {
            calcWidth = (document.compatMode == 'CSS1Compat' ? document.documentElement.clientWidth : document.body.clientWidth);
            calcHeight = (document.compatMode == 'CSS1Compat' ? document.documentElement.clientHeight : document.body.clientHeight);
        }

        calcWidth = Math.max(calcWidth - 2 * border, 0);
        calcHeight = Math.max(calcHeight - 2 * border, 0);
        if (calcWidth % 2) {
            calcWidth--;
        }

        if (calcHeight % 2) {
            calcHeight--;
        }

        this.width = calcWidth;
        this.height = calcHeight;
        this.viewer.style.width = this.width + 'px';
        this.viewer.style.height = this.height + 'px';
        this.viewer.style.top = border + 'px';
        this.viewer.style.left = border + 'px';
    },

    init : function() {
        if (document.attachEvent) {
            document.body.ondragstart = function() { return false; }
        }

        if (this.width == 0 && this.height == 0) {
            this.width = this.viewer.offsetWidth;
            this.height = this.viewer.offsetHeight;
        }

        var fullSize = this.tileSize;
        // explicit set of zoom level
        if (this.zoomLevel >= 0 && this.zoomLevel <= this.maxZoomLevel) {
            fullSize = this.tileSize * Math.pow(2, this.zoomLevel);
        }
        // calculate the zoom level based on what fits best in window
        else {
            this.zoomLevel = -1;
            fullSize = this.tileSize / 2;
            do {
                this.zoomLevel += 1;
                fullSize *= 2;
            } while (fullSize < Math.max(this.width, this.height));
            // take into account picture smaller than window size
            if (this.zoomLevel > this.maxZoomLevel) {
                var diff = this.zoomLevel - this.maxZoomLevel;
                this.zoomLevel = this.maxZoomLevel;
                fullSize /= Math.pow(2, diff);
            }
        }

//fixme fullsize not used anymore?

        // calculate the center
        this.x = 0;
        this.y = 0;
        var inv = Math.max(this.imgsize.x,this.imgsize.y)  /
                  (this.tileSize * Math.pow(2, this.zoomLevel));
        if(this.imgsize.x){
            var xx = (this.imgsize.x / inv)*0.5;
            this.x = Math.floor(xx - this.width * 0.5) * -1;
        }
        if(this.imgsize.y){
            var yy = (this.imgsize.y / inv)*0.5;
            this.y = Math.floor(yy - this.height * 0.5) * -1;
        }


        // offset of viewer in the window
        for (var node = this.viewer; node; node = node.offsetParent) {
            this.top += node.offsetTop;
            this.left += node.offsetLeft;
        }

        for (var child = this.viewer.firstChild; child; child = child.nextSibling) {
            if (child.className == PanoJS.SURFACE_STYLE_CLASS) {
                this.surface = child;
                child.backingBean = this;
            }
            else if (child.className == PanoJS.WELL_STYLE_CLASS) {
                this.well = child;
                child.backingBean = this;
                // empty well
                child.innerHTML = '';
            }
            else if (child.className == PanoJS.CONTROLS_STYLE_CLASS) {
                child.style.display = '';
                for (var control = child.firstChild; control; control = control.nextSibling) {
                    if (control.className) {
                        control.onclick = PanoJS[control.className + 'Handler'];
                    }
                }
            }
        }

        this.viewer.backingBean = this;
        this.surface.style.cursor = PanoJS.GRAB_MOUSE_CURSOR;
        this.prepareTiles();
        this.initialized = true;
    },

    prepareTiles : function() {
        var rows = Math.ceil(this.height / this.tileSize) + 1;
        var cols = Math.ceil(this.width / this.tileSize) + 1;

        for (var c = 0; c < cols; c++) {
            var tileCol = [];

            for (var r = 0; r < rows; r++) {
                /**
                 * element is the DOM element associated with this tile
                 * posx/posy are the pixel offsets of the tile
                 * xIndex/yIndex are the index numbers of the tile segment
                 * qx/qy represents the quadrant location of the tile
                 */
                var tile = {
                    'element' : null,
                    'posx' : 0,
                    'posy' : 0,
                    'xIndex' : c,
                    'yIndex' : r,
                    'qx' : c,
                    'qy' : r
                };

                tileCol.push(tile);
            }

            this.tiles.push(tileCol);
        }

        this.surface.onmousedown = PanoJS.mousePressedHandler;
        this.surface.onmouseup = this.surface.onmouseout = PanoJS.mouseReleasedHandler;
        this.surface.ondblclick = PanoJS.doubleClickHandler;
        if (PanoJS.USE_KEYBOARD) {
            window.onkeypress = PanoJS.keyboardMoveHandler;
            window.onkeydown = PanoJS.keyboardZoomHandler;
        }

        this.positionTiles();
    },

    /**
     * Position the tiles based on the x, y coordinates of the
     * viewer, taking into account the motion offsets, which
     * are calculated by a motion event handler.
     */
    positionTiles : function(motion, reset) {
        // default to no motion, just setup tiles
        if (typeof motion == 'undefined') {
            motion = { 'x' : 0, 'y' : 0 };
        }

        for (var c = 0; c < this.tiles.length; c++) {
            for (var r = 0; r < this.tiles[c].length; r++) {
                var tile = this.tiles[c][r];

                tile.posx = (tile.xIndex * this.tileSize) + this.x + motion.x;
                tile.posy = (tile.yIndex * this.tileSize) + this.y + motion.y;

                var visible = true;

                if (tile.posx > this.width) {
                    // tile moved out of view to the right
                    // consider the tile coming into view from the left
                    do {
                        tile.xIndex -= this.tiles.length;
                        tile.posx = (tile.xIndex * this.tileSize) + this.x + motion.x;
                    } while (tile.posx > this.width);

                    if (tile.posx + this.tileSize < 0) {
                        visible = false;
                    }

                } else {
                    // tile may have moved out of view from the left
                    // if so, consider the tile coming into view from the right
                    while (tile.posx < -this.tileSize) {
                        tile.xIndex += this.tiles.length;
                        tile.posx = (tile.xIndex * this.tileSize) + this.x + motion.x;
                    }

                    if (tile.posx > this.width) {
                        visible = false;
                    }
                }

                if (tile.posy > this.height) {
                    // tile moved out of view to the bottom
                    // consider the tile coming into view from the top
                    do {
                        tile.yIndex -= this.tiles[c].length;
                        tile.posy = (tile.yIndex * this.tileSize) + this.y + motion.y;
                    } while (tile.posy > this.height);

                    if (tile.posy + this.tileSize < 0) {
                        visible = false;
                    }

                } else {
                    // tile may have moved out of view to the top
                    // if so, consider the tile coming into view from the bottom
                    while (tile.posy < -this.tileSize) {
                        tile.yIndex += this.tiles[c].length;
                        tile.posy = (tile.yIndex * this.tileSize) + this.y + motion.y;
                    }

                    if (tile.posy > this.height) {
                        visible = false;
                    }
                }

                // initialize the image object for this quadrant
                if (!this.initialized) {
                    this.assignTileImage(tile, true);
                    tile.element.style.top = tile.posy + 'px';
                    tile.element.style.left = tile.posx + 'px';
                }

                // display the image if visible
                if (visible) {
                    this.assignTileImage(tile);
                }

                // seems to need this no matter what
                tile.element.style.top = tile.posy + 'px';
                tile.element.style.left = tile.posx + 'px';
            }
        }

        // reset the x, y coordinates of the viewer according to motion
        if (reset) {
            this.x += motion.x;
            this.y += motion.y;
        }
    },

    /**
     * Determine the source image of the specified tile based
     * on the zoom level and position of the tile.  If forceBlankImage
     * is specified, the source should be automatically set to the
     * null tile image.  This method will also setup an onload
     * routine, delaying the appearance of the tile until it is fully
     * loaded, if configured to do so.
     */
    assignTileImage : function(tile, forceBlankImage) {
        var tileImgId, src;
        var useBlankImage = (forceBlankImage ? true : false);

        // check if image has been scrolled too far in any particular direction
        // and if so, use the null tile image
        if (!useBlankImage) {
            var left = tile.xIndex < 0;
            var high = tile.yIndex < 0;
            var right = tile.xIndex >= Math.pow(2, this.zoomLevel);
            var low = tile.yIndex >= Math.pow(2, this.zoomLevel);
            if (high || left || low || right) {
                useBlankImage = true;
            }
        }

        if (useBlankImage) {
            tileImgId = 'blank:' + tile.qx + ':' + tile.qy;
            src = this.cache['blank'].src;
        }
        else {
            tileImgId = src = this.tileUrlProvider.assembleUrl(tile.xIndex, tile.yIndex, this.zoomLevel);
        }

        // only remove tile if identity is changing
        if (tile.element != null &&
            tile.element.parentNode != null &&
            tile.element.relativeSrc != src) {
            this.well.removeChild(tile.element);
        }

        var tileImg = this.cache[tileImgId];
        // create cache if not exist
        if (tileImg == null) {
            tileImg = this.cache[tileImgId] = this.createPrototype(src);
        }

        if (useBlankImage || !PanoJS.USE_LOADER_IMAGE || tileImg.complete || (tileImg.image && tileImg.image.complete)) {
            tileImg.onload = function() {};
            if (tileImg.image) {
                tileImg.image.onload = function() {};
            }

            if (tileImg.parentNode == null) {
                tile.element = this.well.appendChild(tileImg);
            }
        }
        else {
            var loadingImgId = 'loading:' + tile.qx + ':' + tile.qy;
            var loadingImg = this.cache[loadingImgId];
            if (loadingImg == null) {
                loadingImg = this.cache[loadingImgId] = this.createPrototype(this.cache['loading'].src);
            }

            loadingImg.targetSrc = tileImgId;

            var well = this.well;
            tile.element = well.appendChild(loadingImg);
            tileImg.onload = function() {
                // make sure our destination is still present
                if (loadingImg.parentNode && loadingImg.targetSrc == tileImgId) {
                    tileImg.style.top = loadingImg.style.top;
                    tileImg.style.left = loadingImg.style.left;
                    well.replaceChild(tileImg, loadingImg);
                    tile.element = tileImg;
                }

                tileImg.onload = function() {};
                return false;
            }

            // konqueror only recognizes the onload event on an Image
            // javascript object, so we must handle that case here
            if (!PanoJS.DOM_ONLOAD) {
                tileImg.image = new Image();
                tileImg.image.onload = tileImg.onload;
                tileImg.image.src = tileImg.src;
            }
        }
    },

    createPrototype : function(src) {
        var img = document.createElement('img');
        img.src = src;
        img.relativeSrc = src;
        img.className = PanoJS.TILE_STYLE_CLASS;
        img.style.width = this.tileSize + 'px';
        img.style.height = this.tileSize + 'px';
        return img;
    },

    addViewerMovedListener : function(listener) {
        this.viewerMovedListeners.push(listener);
    },

    addViewerZoomedListener : function(listener) {
        this.viewerZoomedListeners.push(listener);
    },

    /**
     * Notify listeners of a zoom event on the viewer.
     */
    notifyViewerZoomed : function() {
        var percentage = (100/(this.maxZoomLevel + 1)) * (this.zoomLevel + 1);
        for (var i = 0; i < this.viewerZoomedListeners.length; i++) {
            this.viewerZoomedListeners[i].viewerZoomed(
                new PanoJS.ZoomEvent(this.x, this.y, this.zoomLevel, percentage)
            );
        }
    },

    /**
     * Notify listeners of a move event on the viewer.
     */
    notifyViewerMoved : function(coords) {
        if (typeof coords == 'undefined') {
            coords = { 'x' : 0, 'y' : 0 };
        }

        for (var i = 0; i < this.viewerMovedListeners.length; i++) {
            this.viewerMovedListeners[i].viewerMoved(
                new PanoJS.MoveEvent(
                    this.x + (coords.x - this.mark.x),
                    this.y + (coords.y - this.mark.y)
                )
            );
        }
    },

    zoom : function(direction) {
        // ensure we are not zooming out of range
        if (this.zoomLevel + direction < 0) {
            if (PanoJS.MSG_BEYOND_MIN_ZOOM) {
                alert(PanoJS.MSG_BEYOND_MIN_ZOOM);
            }
            return;
        }
        else if (this.zoomLevel + direction > this.maxZoomLevel) {
            if (PanoJS.MSG_BEYOND_MAX_ZOOM) {
                alert(PanoJS.MSG_BEYOND_MAX_ZOOM);
            }
            return;
        }

        this.blank();

        var coords = { 'x' : Math.floor(this.width / 2), 'y' : Math.floor(this.height / 2) };

        var before = {
            'x' : (coords.x - this.x),
            'y' : (coords.y - this.y)
        };

        var after = {
            'x' : Math.floor(before.x * Math.pow(2, direction)),
            'y' : Math.floor(before.y * Math.pow(2, direction))
        };

        this.x = coords.x - after.x;
        this.y = coords.y - after.y;
        this.zoomLevel += direction;
        this.positionTiles();

        this.notifyViewerZoomed();
    },

    /**
     * Clear all the tiles from the well for a complete reinitialization of the
     * viewer. At this point the viewer is not considered to be initialized.
     */
    clear : function() {
        this.blank();
        this.initialized = false;
        this.tiles = [];
    },

    /**
     * Remove all tiles from the well, which effectively "hides"
     * them for a repaint.
     */
    blank : function() {
        for (imgId in this.cache) {
            var img = this.cache[imgId];
            img.onload = function() {};
            if (img.image) {
                img.image.onload = function() {};
            }

            if (img.parentNode != null) {
                this.well.removeChild(img);
            }
        }
    },

    /**
     * Method specifically for handling a mouse move event.  A direct
     * movement of the viewer can be achieved by calling positionTiles() directly.
     */
    moveViewer : function(coords) {
        this.positionTiles({ 'x' : (coords.x - this.mark.x), 'y' : (coords.y - this.mark.y) });
        this.notifyViewerMoved(coords);
    },

    /**
     * Make the specified coords the new center of the image placement.
     * This method is typically triggered as the result of a double-click
     * event.  The calculation considers the distance between the center
     * of the viewable area and the specified (viewer-relative) coordinates.
     * If absolute is specified, treat the point as relative to the entire
     * image, rather than only the viewable portion.
     */
    recenter : function(coords, absolute) {
        if (absolute) {
            coords.x += this.x;
            coords.y += this.y;
        }

        var motion = {
            'x' : Math.floor((this.width / 2) - coords.x),
            'y' : Math.floor((this.height / 2) - coords.y)
        };

        if (motion.x == 0 && motion.y == 0) {
            return;
        }

        if (PanoJS.USE_SLIDE) {
            var target = motion;
            var x, y;
            // handle special case of vertical movement
            if (target.x == 0) {
                x = 0;
                y = this.slideAcceleration;
            }
            else {
                var slope = Math.abs(target.y / target.x);
                x = Math.round(Math.pow(Math.pow(this.slideAcceleration, 2) / (1 + Math.pow(slope, 2)), .5));
                y = Math.round(slope * x);
            }

            motion = {
                'x' : Math.min(x, Math.abs(target.x)) * (target.x < 0 ? -1 : 1),
                'y' : Math.min(y, Math.abs(target.y)) * (target.y < 0 ? -1 : 1)
            }
        }

        this.positionTiles(motion, true);
        this.notifyViewerMoved();

        if (!PanoJS.USE_SLIDE) {
            return;
        }

        var newcoords = {
            'x' : coords.x + motion.x,
            'y' : coords.y + motion.y
        };

        var self = this;
        // TODO: use an exponential growth rather than linear (should also depend on how far we are going)
        // FIXME: this could be optimized by calling positionTiles directly perhaps
        this.slideAcceleration += PanoJS.SLIDE_ACCELERATION_FACTOR;
        this.slideMonitor = setTimeout(function() { self.recenter(newcoords); }, PanoJS.SLIDE_DELAY );
    },

    resize : function() {
        // IE fires a premature resize event
        if (!this.initialized) {
            return;
        }

        var newWidth = this.viewer.offsetWidth;
        var newHeight = this.viewer.offsetHeight;

        this.viewer.style.display = 'none';
        this.clear();

        var before = {
            'x' : Math.floor(this.width / 2),
            'y' : Math.floor(this.height / 2)
        };

        if (this.border >= 0) {
            this.fitToWindow(this.border);
        }
        else {
            this.width = newWidth;
            this.height = newHeight;
        }

        this.prepareTiles();

        var after = {
            'x' : Math.floor(this.width / 2),
            'y' : Math.floor(this.height / 2)
        };

        if (this.border >= 0) {
            this.x += (after.x - before.x);
            this.y += (after.y - before.y);
        }
        this.positionTiles();
        this.viewer.style.display = '';
        this.initialized = true;
        this.notifyViewerMoved();
    },

    /**
     * Resolve the coordinates from this mouse event by subtracting the
     * offset of the viewer in the browser window (or frame).  This does
     * take into account the scroll offset of the page.
     */
    resolveCoordinates : function(e) {
        return {
            'x' : (e.pageX || (e.clientX + (document.documentElement.scrollLeft || document.body.scrollLeft))) - this.left,
            'y' : (e.pageY || (e.clientY + (document.documentElement.scrollTop || document.body.scrollTop))) - this.top
        }
    },

    press : function(coords) {
        this.activate(true);
        this.mark = coords;
    },

    release : function(coords) {
        this.activate(false);
        var motion = {
            'x' : (coords.x - this.mark.x),
            'y' : (coords.y - this.mark.y)
        };

        this.x += motion.x;
        this.y += motion.y;
        this.mark = { 'x' : 0, 'y' : 0 };
    },

    /**
     * Activate the viewer into motion depending on whether the mouse is pressed or
     * not pressed.  This method localizes the changes that must be made to the
     * layers.
     */
    activate : function(pressed) {
        this.pressed = pressed;
        this.surface.style.cursor = (pressed ? PanoJS.GRABBING_MOUSE_CURSOR : PanoJS.GRAB_MOUSE_CURSOR);
        this.surface.onmousemove = (pressed ? PanoJS.mouseMovedHandler : function() {});
    },

    /**
     * Check whether the specified point exceeds the boundaries of
     * the viewer's primary image.
     */
    pointExceedsBoundaries : function(coords) {
        return (coords.x < this.x ||
            coords.y < this.y ||
            coords.x > (this.tileSize * Math.pow(2, this.zoomLevel) + this.x) ||
            coords.y > (this.tileSize * Math.pow(2, this.zoomLevel) + this.y));
    },

    // QUESTION: where is the best place for this method to be invoked?
    resetSlideMotion : function() {
        // QUESTION: should this be > 0 ?
        if (this.slideMonitor != 0) {
            clearTimeout(this.slideMonitor);
            this.slideMonitor = 0;
        }

        this.slideAcceleration = 0;
    }
};

PanoJS.TileUrlProvider = function(baseUri, image) {
    this.baseUri = baseUri;
    this.image   = image;
}

PanoJS.TileUrlProvider.prototype = {
    assembleUrl: function(xIndex, yIndex, zoom) {
        return this.baseUri + '?tile=' +
               zoom + '-' + xIndex + '-' + yIndex +
               '&image=' + encodeURIComponent(this.image);
    }
}

PanoJS.mousePressedHandler = function(e) {
    e = e ? e : window.event;
    // only grab on left-click
    if (e.button < 2) {
        var self = this.backingBean;
        var coords = self.resolveCoordinates(e);
        if (self.pointExceedsBoundaries(coords)) {
            e.cancelBubble = true;
        }
        else {
            self.press(coords);
        }
    }

    // NOTE: MANDATORY! must return false so event does not propagate to well!
    return false;
};

PanoJS.mouseReleasedHandler = function(e) {
    e = e ? e : window.event;
    var self = this.backingBean;
    if (self.pressed) {
        // OPTION: could decide to move viewer only on release, right here
        self.release(self.resolveCoordinates(e));
    }
};

PanoJS.mouseMovedHandler = function(e) {
    e = e ? e : window.event;
    var self = this.backingBean;
    self.moveCount++;
    if (self.moveCount % PanoJS.MOVE_THROTTLE == 0) {
        self.moveViewer(self.resolveCoordinates(e));
    }
};

PanoJS.zoomInHandler = function(e) {
    e = e ? e : window.event;
    var self = this.parentNode.parentNode.backingBean;
    self.zoom(1);
    return false;
};

PanoJS.zoomOutHandler = function(e) {
    e = e ? e : window.event;
    var self = this.parentNode.parentNode.backingBean;
    self.zoom(-1);
    return false;
};

PanoJS.doubleClickHandler = function(e) {
    e = e ? e : window.event;
    var self = this.backingBean;
    coords = self.resolveCoordinates(e);
    if (!self.pointExceedsBoundaries(coords)) {
        self.resetSlideMotion();
        self.recenter(coords);
    }
};

PanoJS.keyboardMoveHandler = function(e) {
    e = e ? e : window.event;
    for (var i = 0; i < PanoJS.VIEWERS.length; i++) {
        var viewer = PanoJS.VIEWERS[i];
        if (e.keyCode == 38)
                viewer.positionTiles({'x': 0,'y': -PanoJS.MOVE_THROTTLE}, true);
        if (e.keyCode == 39)
                viewer.positionTiles({'x': -PanoJS.MOVE_THROTTLE,'y': 0}, true);
        if (e.keyCode == 40)
                viewer.positionTiles({'x': 0,'y': PanoJS.MOVE_THROTTLE}, true);
        if (e.keyCode == 37)
                viewer.positionTiles({'x': PanoJS.MOVE_THROTTLE,'y': 0}, true);
    }
}

PanoJS.keyboardZoomHandler = function(e) {
    e = e ? e : window.event;
    for (var i = 0; i < PanoJS.VIEWERS.length; i++) {
        var viewer = PanoJS.VIEWERS[i];
        if (e.keyCode == 109)
                viewer.zoom(-1);
        if (e.keyCode == 107)
                viewer.zoom(1);
    }
}

PanoJS.MoveEvent = function(x, y) {
    this.x = x;
    this.y = y;
};

PanoJS.ZoomEvent = function(x, y, level, percentage) {
    this.x = x;
    this.y = y;
    this.percentage = percentage;
    this.level = level;
};

addInitEvent(function(){
    var panos = getElementsByClass('panoview_plugin',document,'div');
    for(var i=0; i<panos.length; i++){
        var pano = panos[i];
        var opts = getElementsByClass('options',pano,'div')[0];
        var conf;
        eval('conf ='+opts.innerHTML); //JSON

        var viewerBean = new PanoJS(pano, conf);
        viewerBean.init();
    }
});