/*
 * Call generic wms service for GoogleMaps v2
 * John Deck, UC Berkeley
 * Inspiration & Code from:
 *      Mike Williams http://www.econym.demon.co.uk/googlemaps2/ V2 Reference & custommap code
 *      Brian Flood http://www.spatialdatalogic.com/cs/blogs/brian_flood/archive/2005/07/11/39.aspx V1 WMS code
 *      Kyle Mulka http://blog.kylemulka.com/?p=287  V1 WMS code modifications
 *      http://search.cpan.org/src/RRWO/GPS-Lowrance-0.31/lib/Geo/Coordinates/MercatorMeters.pm
 * 		Modified by Chris Holmes, TOPP to work by default with GeoServer.
 *		Guilhem Vellut <guilhem.vellut@gmail.com> for more accurate Javascript Mercator Fxn
 *
 * Note this only works with gmaps v2.36 and above.  http://johndeck.blogspot.com
 * has scripts
 * that do the same for older gmaps versions - just change from 54004 to 41001.
 *
 * About:
 * This script provides an implementation of GTileLayer that works with WMS
 * services that provide epsg 41001 (Mercator).  This provides a reasonable
 * accuracy on overlays at most zoom levels.  It switches between Mercator
 * and Lat/Long at the myMercZoomLevel variable, defaulting to MERC_ZOOM_DEFAULT
 * of 5.  It also performs the calculation from a GPoint to the appropriate
 * BBOX to pass the WMS.  The overlays could be more accurate, and if you
 * figure out a way to make them so please contribute information back to
 * http://docs.codehaus.org/display/GEOSDOC/Google+Maps.  There is much
 * information at:
 * http://cfis.savagexi.com/articles/2006/05/03/google-maps-deconstructed
 *
 * Use:
 * This script is used by creating a new GTileLayer, setting the required
 * and any desired optional variables, and setting the functions here to
 * override the appropriate GTileLayer ones.
 *
 * At the very least you will need:
 * var myTileLayer= new GTileLayer(new GCopyrightCollection(""),1,17);
 *     myTileLayer.myBaseURL='http://yourserver.org/wms?'
 *     myTileLayer.myLayers='myLayerName';
 *     myTileLayer=CustomGetTileUrl
 *
 * After that you can override the format (myFormat), the level at
 * which the zoom switches (myMercZoomLevel), and the style (myStyles)
 * - be sure to put one style for each layer (both are separated by
 * commas).  You can also override the Opacity:
 *     myTileLayer.myOpacity=0.69
 *     myTileLayer.getOpacity=customOpacity
 *
 * Then you can overlay on google maps with something like:
 * var layer=[G_SATELLITE_MAP.getTileLayers()[0],tileCountry];
 * var custommap = new GMapType(layer, G_SATELLITE_MAP.getProjection(), "WMS");
 * var map = new GMap(document.getElementById("map"));
 *     map.addMapType(custommap);
 */

//var MAGIC_NUMBER=6356752.3142;
var WGS84_SEMI_MAJOR_AXIS = 6378137.0;
var WGS84_ECCENTRICITY = 0.0818191913108718138;

var DEG2RAD=0.0174532922519943;
var PI=3.14159267;

//Default image format, used if none is specified
var FORMAT_DEFAULT="image/png";

//hack to ensure img src url is always unique - incremented after in CustomGetGroundOverlay
//done so that overlays reload when user changes google map type, otherwise browser cache contains img & img.onload function doesn't get called
var imgRequestCount=0;

//Google Maps Zoom level at which we switch from Mercator to Lat/Long.
var MERC_ZOOM_DEFAULT = 999;

function dd2MercMetersLng(p_lng) {
	return WGS84_SEMI_MAJOR_AXIS * (p_lng*DEG2RAD);
}

function dd2MercMetersLat(p_lat) {
	var lat_rad = p_lat * DEG2RAD;
	return WGS84_SEMI_MAJOR_AXIS * Math.log(Math.tan((lat_rad + PI / 2) / 2) * Math.pow( ((1 - WGS84_ECCENTRICITY * Math.sin(lat_rad)) / (1 + WGS84_ECCENTRICITY * Math.sin(lat_rad))), (WGS84_ECCENTRICITY/2)));
}

CustomGetTileUrl = function(a, b, c) {
    if (this.myMercZoomLevel == undefined) {
        this.myMercZoomLevel = MERC_ZOOM_DEFAULT;
    }

    if (this.myFormat == undefined) {
        this.myFormat = FORMAT_DEFAULT;
    }

    if (typeof (window['this.myStyles']) == "undefined") this.myStyles = "";
    var lULP = new GPoint(a.x * 256, (a.y + 1) * 256);
    var lLRP = new GPoint((a.x + 1) * 256, a.y * 256);
    var lUL = G_NORMAL_MAP.getProjection().fromPixelToLatLng(lULP, b, c);
    var lLR = G_NORMAL_MAP.getProjection().fromPixelToLatLng(lLRP, b, c);

    // switch between Mercator and DD if merczoomlevel is set
    // NOTE -it is now safe to use Mercator exclusively for all zoom levels (if your WMS supports it)
    // so you can just use the two lines of code below the IF (& delete the ELSE)

    //alert(dd2MercMetersLng(lUL.x)+","+dd2MercMetersLat(lUL.y)+","+dd2MercMetersLng(lLR.x)+","+dd2MercMetersLat(lLR.y))

    if (this.myMercZoomLevel != 0 && map.getZoom() < this.myMercZoomLevel) {
        var lBbox = dd2MercMetersLng(lUL.x) + "," + dd2MercMetersLat(lUL.y) + "," + dd2MercMetersLng(lLR.x) + "," + dd2MercMetersLat(lLR.y);
        //Change for GeoServer - 41001 is mercator and installed by default.
        var lSRS = "EPSG:54004";
    } else {
        var lBbox = lUL.x + "," + lUL.y + "," + lLR.x + "," + lLR.y;
        var lSRS = "EPSG:54004";
    }
    var lURL = this.myBaseURL;
    lURL += "&REQUEST=GetMap";
    lURL += "&SERVICE=WMS";
    lURL += "&VERSION=1.1.1";
    lURL += "&LAYERS=" + this.myLayers;
    lURL += "&STYLES=" + this.myStyles;
    lURL += "&FORMAT=" + this.myFormat;
    //lURL+="&BGCOLOR=0xFFFFFF";
    //lURL+="&TRANSPARENT=TRUE";
    lURL += "&SRS=" + lSRS;
    lURL += "&BBOX=" + lBbox;
    lURL += "&WIDTH=256";
    lURL += "&HEIGHT=256";
    lURL += "&reaspect=false";

    
    return lURL;
}

//opacity is a value 0 (solid) – 255 (transparent) 
function CustomGetGroundOverlay(bounds, gutterPixel, opacity, mapUrl, layers) {
	if (this.myMercZoomLevel == undefined) {
	this.myMercZoomLevel = MERC_ZOOM_DEFAULT;
	}

	if (this.myFormat == undefined) {
	  this.myFormat = FORMAT_DEFAULT;
	}

	if (typeof(window['this.myStyles'])=="undefined") this.myStyles=""; 

	var lBbox=bounds.getSouthWest().lng() + "," + bounds.getSouthWest().lat() + ","+ bounds.getNorthEast().lng() + "," + bounds.getNorthEast().lat()
	var lSRS="EPSG:4326";

	var lURL='';//mapTransparencyURL;

	//lURL += 'wmsurl='+mapUrl;
	lURL = mapUrl;

	//Add filter to the WMS URL
	//if record ID specified, pass ID(s) so record is highlighted (in yellow) on map
	//used on singleResult page & list from multiresults
//	if ((strUIDFilter !='') && (mapUrl==mapDataLayerURL))
//	{
//		lURL+='&ID='+strUIDFilter;
//	} 
	lURL+="&REQUEST=GetMap";
	lURL+="&SERVICE=WMS";
	lURL+="&VERSION=1.1.1";
	lURL+="&LAYERS="+layers;
	lURL+="&STYLES="+this.myStyles;
	lURL+="&FORMAT=image/png";
	//lURL+="&BGCOLOR=0xFFFFFF";
	//lURL+="&TRANSPARENT=TRUE";
	lURL+="&SRS="+lSRS;
	lURL+="&BBOX="+lBbox;
	lURL+="&WIDTH=" + (pageMapWidth + 2 * gutterPixel); 
	lURL+="&HEIGHT=" + (pageMapHeight + 2 * gutterPixel);
	lURL+="&reaspect=false";
	lURL+="&opacity="+opacity;
	lURL+="&unique="+imgRequestCount;  //ensure unique url
	imgRequestCount+=1;

	//can't urlencode mapdata request - messes up strUIDFilter CSV
	//	return mapTransparencyURL + urlEncode(lURL + '&opacity='+opacity);
	//alert(lURL);
	return  lURL 
}

function customOpacity() { return this.myOpacity; }