/* Copyright (c) 2006-2012 by OpenLayers Contributors (see authors.txt for 
 * full list of contributors). Published under the 2-clause BSD license.
 * See license.txt in the OpenLayers distribution or repository for the
 * full text of the license. */


/**
 * @requires OpenLayers/Layer/Grid.js
 */

/**
 * Class: OpenLayers.Layer.WorldWind
 * 
 * Inherits from:
 *  - <OpenLayers.Layer.Grid>
 */
OpenLayers.Layer.WorldWind = OpenLayers.Class(OpenLayers.Layer.Grid, {
    
    DEFAULT_PARAMS: {
    },

    /**
     * APIProperty: isBaseLayer
     * {Boolean} WorldWind layer is a base layer by default.
     */
    isBaseLayer: true,

    /** 
     * APIProperty: lzd
     * {Float} LevelZeroTileSizeDegrees
     */
    lzd: null,

    /**
     * APIProperty: zoomLevels
     * {Integer} Number of zoom levels.
     */
    zoomLevels: null,
    
    /**
     * Constructor: OpenLayers.Layer.WorldWind
     * 
     * Parameters:
     * name - {String} Name of Layer
     * url - {String} Base URL  
     * lzd - {Float} Level zero tile size degrees 
     * zoomLevels - {Integer} number of zoom levels
     * params - {Object} additional parameters
     * options - {Object} additional options
     */
    initialize: function(name, url, lzd, zoomLevels, params, options) {
        this.lzd = lzd;
        this.zoomLevels = zoomLevels;
        var newArguments = [];
        newArguments.push(name, url, params, options);
        OpenLayers.Layer.Grid.prototype.initialize.apply(this, newArguments);
        this.params = OpenLayers.Util.applyDefaults(
            this.params, this.DEFAULT_PARAMS
        );
    },

    /**
     * Method: getZoom
     * Convert map zoom to WW zoom.
     */
    getZoom: function () {
        var zoom = this.map.getZoom();
        var extent = this.map.getMaxExtent();
        zoom = zoom - Math.log(this.maxResolution / (this.lzd/512))/Math.log(2);
        return zoom;
    },

    /**
     * Method: getURL
     *
     * Parameters:
     * bounds - {<OpenLayers.Bounds>} 
     *
     * Returns:
     * {String} A string with the layer's url and parameters and also the 
     *           passed-in bounds and appropriate tile size specified as 
     *           parameters
     */
    getURL: function (bounds) {
        bounds = this.adjustBounds(bounds);
        var zoom = this.getZoom();
        var extent = this.map.getMaxExtent();
        var deg = this.lzd/Math.pow(2,this.getZoom());
        var x = Math.floor((bounds.left - extent.left)/deg);
        var y = Math.floor((bounds.bottom - extent.bottom)/deg);
        if (this.map.getResolution() <= (this.lzd/512)
            && this.getZoom() <= this.zoomLevels) {
            return this.getFullRequestString(
              { L: zoom, 
                X: x,
                Y: y
              });
        } else {
            return OpenLayers.Util.getImageLocation("blank.gif");
        }

    },

    CLASS_NAME: "OpenLayers.Layer.WorldWind"
});
