/* Copyright (c) 2006-2008 MetaCarta, Inc., published under the Clear BSD
 * license.  See http://svn.openlayers.org/trunk/openlayers/license.txt for the
 * full text of the license. */
 
/**
 * @requires OpenLayers/Layer/Grid.js
 */
 
/**
 * Class: OpenLayers.Layer.MapServer
 * Instances of OpenLayers.Layer.MapServer are used to display
 * data from a MapServer CGI instance.
 *
 * Inherits from:
 *  - <OpenLayers.Layer.Grid>
 */
OpenLayers.Layer.MapServer = OpenLayers.Class(OpenLayers.Layer.Grid, {
 
    /**
     * Constant: DEFAULT_PARAMS
     * {Object} Hashtable of default parameter key/value pairs 
     */
    DEFAULT_PARAMS: {
        mode: "map",
        map_imagetype: "png"
    },
 
    /**
     * Constructor: OpenLayers.Layer.MapServer
     * Create a new MapServer layer object
     *
     * Parameters:
     * name - {String} A name for the layer
     * url - {String} Base url for the MapServer CGI
     *       (e.g. http://www2.dmsolutions.ca/cgi-bin/mapserv)
     * params - {Object} An object with key/value pairs representing the
     *          GetMap query string parameters and parameter values.
     * options - {Ojbect} Hashtable of extra options to tag onto the layer
     */
    initialize: function(name, url, params, options) {
        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
        );
 
        // unless explicitly set in options, if the layer is transparent, 
        // it will be an overlay
        if (options == null || options.isBaseLayer == null) {
            this.isBaseLayer = ((this.params.transparent != "true") && 
                                (this.params.transparent != true));
        }
    },
 
    /**
     * Method: clone
     * Create a clone of this layer
     *
     * Returns:
     * {<OpenLayers.Layer.MapServer>} An exact clone of this layer
     */
    clone: function (obj) {
        if (obj == null) {
            obj = new OpenLayers.Layer.MapServer(this.name,
                                           this.url,
                                           this.params,
                                           this.options);
        }
        //get all additions from superclasses
        obj = OpenLayers.Layer.Grid.prototype.clone.apply(this, [obj]);
 
        // copy/set any non-init, non-simple values here
 
        return obj;
    },
 
    /**
     * Method: addTile
     * Creates a tile, initializes it, and adds it to the layer div. 
     *
     * Parameters:
     * bounds - {<OpenLayers.Bounds>}
     * position - {<OpenLayers.Pixel>}
     * 
     * Returns:
     * {<OpenLayers.Tile.Image>} The added OpenLayers.Tile.Image
     */
    addTile:function(bounds,position) {
        return new OpenLayers.Tile.Image(this, position, bounds, 
                                         null, this.tileSize);
    },
    
    /**
     * Method: getURL
     * Return a query string for this layer
     *
     * Parameters:
     * bounds - {<OpenLayers.Bounds>} A bounds representing the bbox 
     *                                for the request
     *
     * 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);
        // Make a list, so that getFullRequestString uses literal "," 
        var extent = [bounds.left, bounds. bottom, bounds.right, bounds.top];
 
        var imageSize = this.getImageSize(); 
        
        // make lists, so that literal ','s are used 
        var url = this.getFullRequestString(
                     {mapext:   extent,
                      imgext:   extent,
                      map_size: [imageSize.w, imageSize.h],
                      imgx:     imageSize.w / 2,
                      imgy:     imageSize.h / 2,
                      imgxy:    [imageSize.w, imageSize.h]
                      });
        
        return url;
    },
    
    /** 
     * Method: getFullRequestString
     * combine the layer's url with its params and these newParams. 
     *   
     * Parameter:
     * newParams - {Object} New parameters that should be added to the 
     *                      request string.
     * altUrl - {String} (optional) Replace the URL in the full request  
     *                              string with the provided URL.
     * 
     * Returns: 
     * {String} A string with the layer's url and parameters embedded in it.
     */
    getFullRequestString:function(newParams, altUrl) {
        // use layer's url unless altUrl passed in
        var url = (altUrl == null) ? this.url : altUrl;
        
        // create a new params hashtable with all the layer params and the 
        // new params together. then convert to string
        var allParams = OpenLayers.Util.extend({}, this.params);
        allParams = OpenLayers.Util.extend(allParams, newParams);
        var paramsString = OpenLayers.Util.getParameterString(allParams);
        
        // if url is not a string, it should be an array of strings, 
        // in which case we will deterministically select one of them in 
        // order to evenly distribute requests to different urls.
        if (url instanceof Array) {
            url = this.selectUrl(paramsString, url);
        }   
        
        // ignore parameters that are already in the url search string
        var urlParams = OpenLayers.Util.upperCaseObject(
                            OpenLayers.Util.getParameters(url));
        for(var key in allParams) {
            if(key.toUpperCase() in urlParams) {
                delete allParams[key];
            }
        }
        paramsString = OpenLayers.Util.getParameterString(allParams);
        
        // requestString always starts with url
        var requestString = url;        
 
        // MapServer needs '+' seperating things like bounds/height/width.
        //   Since typically this is URL encoded, we use a slight hack: we
        //  depend on the list-like functionality of getParameterString to
        //  leave ',' only in the case of list items (since otherwise it is
        //  encoded) then do a regular expression replace on the , characters
        //  to '+'
        //
        paramsString = paramsString.replace(/,/g, "+");
        
        if (paramsString != "") {
            var lastServerChar = url.charAt(url.length - 1);
            if ((lastServerChar == "&") || (lastServerChar == "?")) {
                requestString += paramsString;
            } else {
                if (url.indexOf('?') == -1) {
                    //serverPath has no ? -- add one
                    requestString += '?' + paramsString;
                } else {
                    //serverPath contains ?, so must already have paramsString at the end
                    requestString += '&' + paramsString;
                }
            }
        }
        return requestString;
    },
 
    CLASS_NAME: "OpenLayers.Layer.MapServer"
});