[generator] retrieve socket:* OSM tags used by amenity:charging_station

Currently support the following socket types:
- type 1
- type 1 combo
- type 2 (wired or wo/ cable)
- type 2 combo
- chademo
- nacs

This commit also adds initial display of the socket types and power
the to Qt desktop app.

Signed-off-by: Séverin Lemaignan <severin@guakamole.org>

generator/osm2meta.hpp

@@ -9,6 +9,23 @@ struct MetadataTagProcessorImpl
 {
   MetadataTagProcessorImpl(FeatureBuilderParams & params) : m_params(params) {}
 
+  /** Parse OSM attributes for socket types and add them to m_chargeSockets.
+   *
+   * Examples of (k,v) pairs:
+   * ("socket:type2_combo", "2")
+   * ("socket:type2_combo:output", "150 kW")
+   * ("socket:chademo", "1")
+   * ("socket:chademo:output", "50") // assumes kW
+   */
+  void AggregateChargeSocket(std::string const & k, std::string const & v);
+
+  /** Output the list of all sockets for a given charging station in the format
+   * <type>|<nb>|[<power>];...
+   *
+   * For instance:
+   * "type2_combo|2|150;chademo|1|50;type2|2|"
+   */
+  std::string StringifyChargeSockets() const;
   std::string ValidateAndFormat_maxspeed(std::string const & v) const;
   static std::string ValidateAndFormat_stars(std::string const & v);
   std::string ValidateAndFormat_operator(std::string const & v) const;
@@ -45,6 +62,21 @@ struct MetadataTagProcessorImpl
   static std::string ValidateAndFormat_outdoor_seating(std::string v);
 
 protected:
+  // struct to store the representation of a charging station socket
+  struct ChargeSocketDescriptor
+  {
+    std::string type;       // https://wiki.openstreetmap.org/wiki/Key:socket:*
+                            // e.g. "type1"
+    std::string count;      // number of sockets or 'y' if OSM tag was set to 'yes'.
+			    // ("" if unknown)
+    std::string output_kW;  // optional power output, in kW ("" if unknown)
+  };
+  typedef std::vector<ChargeSocketDescriptor> ChargeSocketDescriptors;
+
+  // stores information about charge sockets in charging stations.
+  // Incrementally completed in AggregateChargeSocket
+  ChargeSocketDescriptors m_chargeSockets;
+
   FeatureBuilderParams & m_params;
 };