+ if zoom >= 1 && zoom <= 16 &&
+ endtime > starttime && endtime - starttime <= 24.hours
+ mask = (1 << zoom) - 1
+
+ tiles = Node.where(:timestamp => starttime..endtime).group("maptile_for_point(latitude, longitude, #{zoom})").count
+
+ doc = OSM::API.new.get_xml_doc
+ changes = XML::Node.new "changes"
+ changes["starttime"] = starttime.xmlschema
+ changes["endtime"] = endtime.xmlschema
+
+ tiles.each do |tile, count|
+ x = (tile.to_i >> zoom) & mask
+ y = tile.to_i & mask
+
+ t = XML::Node.new "tile"
+ t["x"] = x.to_s
+ t["y"] = y.to_s
+ t["z"] = zoom.to_s
+ t["changes"] = count.to_s
+
+ changes << t
+ end
+
+ doc.root << changes
+
+ render :xml => doc.to_s
+ else
+ render :plain => "Requested zoom is invalid, or the supplied start is after the end time, or the start duration is more than 24 hours", :status => :bad_request
+ end
+ end
+
+ # External apps that use the api are able to query the api to find out some
+ # parameters of the API. It currently returns:
+ # * minimum and maximum API versions that can be used.
+ # * maximum area that can be requested in a bbox request in square degrees
+ # * number of tracepoints that are returned in each tracepoints page
+ def capabilities
+ @database_status = database_status
+ @api_status = api_status
+ @gpx_status = gpx_status
+ end