var map;
var markers;
var popup;
var epsg4326 = new OpenLayers.Projection("EPSG:4326");

function createMap(divName, centre, zoom) {
  OpenLayers.Util.onImageLoadError = function() {
    this.src = "cycle_map_more_soon2.png";
  }

  map = new OpenLayers.Map(divName,
          { maxExtent: new OpenLayers.Bounds(-20037508,-20037508,20037508,20037508),
            numZoomLevels: 19,
            maxResolution: 156543,
            units: 'm',
            projection: "EPSG:900913",
            controls: [
              new OpenLayers.Control.LayerSwitcher({roundedCornerColor: "#575757"}),
              new OpenLayers.Control.Permalink('permalink'),
              new OpenLayers.Control.Permalink('editlink', 'http://www.openstreetmap.org/edit.html'),
              new OpenLayers.Control.Attribution(),
              new OpenLayers.Control.PanZoomBar(),
              new OpenLayers.Control.Navigation()
            ],
            displayProjection:  new OpenLayers.Projection("EPSG:4326") });

   var cycleattrib = '<b>OpenCycleMap.org - the <a href="http://www.openstreetmap.org">OpenStreetMap</a> Cycle Map</b><br />'
                   + '<a href="http://www.gravitystorm.co.uk/shine/cycle-info/">Key and More Info</a>'
                   + ' | <a href="http://www.gravitystorm.co.uk/shine/cycle-map-help">Help</a>'
                   + ' | <a href="http://shop.opencyclemap.org">Shop</a>'
                   + ' | <a href="http://www.gravitystorm.co.uk/shine/gps-recommendations">GPS</a><br />'
                   + 'Created by <a href="http://www.gravitystorm.co.uk">Andy Allan</a> and Dave Stubbs<br />'
                   + 'Hardware Sponsored by <a href="http://www.cloudmade.com">CloudMade</a> <br />'
                   ;
   var transportattrib = '<b>Gravitystorm Transport Map</b> - an experimental new style<br />More details coming soon!'
   var landscapeattrib = '<b>Gravitystorm Landscape Map</b> - an experimental new style<br />More details coming soon!'

   var cycle = new OpenLayers.Layer.OSM("OpenCycleMap",
                                        ["http://a.tile.opencyclemap.org/cycle/${z}/${x}/${y}.png",
                                         "http://b.tile.opencyclemap.org/cycle/${z}/${x}/${y}.png",
                                         "http://c.tile.opencyclemap.org/cycle/${z}/${x}/${y}.png"],
                                        { displayOutsideMaxExtent: true,
                                          attribution: cycleattrib, transitionEffect: 'resize'});
   map.addLayer(cycle);

   var transport = new OpenLayers.Layer.OSM("Transport",
                                         ["http://a.tile2.opencyclemap.org/transport/${z}/${x}/${y}.png",
                                         "http://b.tile2.opencyclemap.org/transport/${z}/${x}/${y}.png",
                                         "http://c.tile2.opencyclemap.org/transport/${z}/${x}/${y}.png"],
                                         { displayOutsideMaxExtent: true,
                                         attribution: transportattrib, transitionEffect: 'resize'});
   map.addLayer(transport);

   var landscape = new OpenLayers.Layer.OSM("Landscape",
                                         ["http://a.tile3.opencyclemap.org/landscape/${z}/${x}/${y}.png",
                                         "http://b.tile3.opencyclemap.org/landscape/${z}/${x}/${y}.png",
                                         "http://c.tile3.opencyclemap.org/landscape/${z}/${x}/${y}.png"],
                                         { displayOutsideMaxExtent: true,
                                         attribution: landscapeattrib, transitionEffect: 'resize'});
   map.addLayer(landscape);

   if (!map.getCenter()) map.setCenter(centre, zoom);
   map.events.register("moveend", map, updateLocation);
   map.events.register("changelayer", map, updateLocation);
   return map;
}

function mercatorToLonLat(merc) {
   var lon = (merc.lon / 20037508.34) * 180;
   var lat = (merc.lat / 20037508.34) * 180;

   lat = 180/Math.PI * (2 * Math.atan(Math.exp(lat * Math.PI / 180)) - Math.PI / 2);

   return new OpenLayers.LonLat(lon, lat);
}

function lonLatToMercator(ll) {
   var lon = ll.lon * 20037508.34 / 180;
   var lat = Math.log(Math.tan((90 + ll.lat) * Math.PI / 360)) / (Math.PI / 180);

   lat = lat * 20037508.34 / 180;

   return new OpenLayers.LonLat(lon, lat);
}

function scaleToZoom(scale) {
   return Math.log(360.0/(scale * 512.0)) / Math.log(2.0);
}

function updateLocation() {
    var lonlat = map.getCenter().clone().transform(map.getProjectionObject(), epsg4326);
    var zoom = map.getZoom();
    var layers = getMapLayers();
    var extents = map.getExtent().clone().transform(map.getProjectionObject(), epsg4326);
    var expiry = new Date();

    expiry.setYear(expiry.getFullYear() + 10); 
    document.cookie = "_osm_location=" + lonlat.lon + "|" + lonlat.lat + "|" + zoom + "|" + layers + "; expires=" + expiry.toGMTString();
  }

function getMapLayers() {
   var layerConfig = "";

   for (var layers = map.getLayersBy("isBaseLayer", true), i = 0; i < layers.length; i++) {
      layerConfig += layers[i] == map.baseLayer ? "B" : "0";
   }

   for (var layers = map.getLayersBy("isBaseLayer", false), i = 0; i < layers.length; i++) {
      layerConfig += layers[i].getVisibility() ? "T" : "F";
   }

   return layerConfig;
}

function setMapExtent(extent) {
   map.zoomToExtent(extent.clone().transform(epsg4326, map.getProjectionObject()));
}