Make it possible to patch ParticleID meta information when patching c…

…ollections (#193)

* Avoid unnecessary copies of strings and vectors

* Remove unused variable

* Fix some trailing whitespaces

* Fix docstring

* Improve readability with structured bindings

* Use std::tie to get rid of unnecessary temporary

* Get rid of unnecessary branch

* Keep track of ParticleID metadata while scanning

* Make PIDMeta public to satisfy ROOT

* Patch ParticleID meta data on request

* Set the PID meta data after all collections have been converted

* Make things work with c++17

* Add patching grammar to docstring

src/cpp/include/UTIL/CheckCollections.h

@@ -9,7 +9,8 @@
 
 namespace UTIL {
 
-
+class PIDHandler;
+
 /** Utility class for checking and patching events with respect to collections that are not present 
  *  in every event of a set of files. 
  *  
@@ -55,26 +56,69 @@ namespace UTIL {
     Vector getConsistentCollections() const ;
 
     /** Add a collection with (name,type) that should be added to events in patchEvent().
+     *
+     * Depending on the contents of name and type one of the following things
+     * will happen:
+     *
+     * - if type is an LCIO type an empty collection of the given type will be
+         put into the event using the passed name
+     * - if type is `LCRelation[<from-type>,<to-type>]` an LCRelation collection
+     *   will be created setting the <from-type> and <to-type> as FromType and
+     *   ToType collection parameters.
+     * - if type contains a '|' the whole (name, type) pair will be considered
+     *   to be ParticleID meta information and the name will be used as a PID
+     *   algorithm name and the type information will be parsed as
+     *   <reco-coll-name>|[<param-name>,<param-names...>], I.e. a ParticleID
+     *   algorithm of name will be attached to the ReconstructedParticle
+     *   collection with name <reco-coll-name>. Additionally any parameter names
+     *   that are in the comma-separated list after the '|' will be set via the
+     *   PIDHandler for this ParticleID algorithm
      */
-    void addPatchCollection(const std::string name, std::string type){
-      _patchCols.push_back( {name, type} ) ;
-    }
+    void addPatchCollection(std::string name, std::string type);
 
-    /** Add a all collections as Vector(name,type), e.g. retrieved from getMissingCollections()  that should be added to events in patchEvent().
+    /** Add all collections as Vector(name,type), e.g. retrieved from getMissingCollections()  that should be added to events in patchEvent().
      */
-    void addPatchCollections(Vector cols){
-      for(const auto& p : cols)
-	_patchCols.push_back( p ) ;
-    }
+    void addPatchCollections(Vector cols);
 
     /** Add and empty collection to the event for any collection that is in patchCollections and not in the Event  
      */
     void patchCollections(EVENT::LCEvent* evt ) const ;
-
+
+    /// Metadata for ParticleIDs that are handled via the PIDHandler. Necessary
+    /// for consistency with EDM4hep, where ParticleID no longer lives in
+    /// ReconstructedParticle and where the direction of the relation has been
+    /// reversed.
+    struct PIDMeta {
+      // c++17 doesn't yet have aggregate initialization in vectors, so we
+      // need this constructor
+      PIDMeta(const std::string &n, const std::vector<std::string> &parN,
+              uint32_t c = 0)
+          : name(n), paramNames(parN), count(c) {}
+
+      // Since we have one non-default constructor we need to default the rest
+      // explicitly
+      constexpr PIDMeta() = default;
+      PIDMeta(const PIDMeta &) = default;
+      PIDMeta &operator=(const PIDMeta &) = default;
+      PIDMeta(PIDMeta &&) = default;
+      PIDMeta &operator=(PIDMeta &&) = default;
+      ~PIDMeta() = default;
+
+      std::string name{};                    ///< algorithm name
+      std::vector<std::string> paramNames{}; ///< parameter names
+      uint32_t count{};                      ///< How often this was found
+    };
+
   private:
+
+    void insertParticleIDMetas(const UTIL::PIDHandler& pidHandler, const std::string& recoName);
+
     unsigned _nEvents =0 ;
     std::unordered_map< std::string, std::pair< std::string, unsigned > > _map{} ;
-    Vector _patchCols {} ;
+    /// Map from ReconstructedParticle collection names to attached ParticleID
+    /// meta information
+    std::unordered_map<std::string, std::vector<PIDMeta>> _particleIDMetas{};
+    Vector _patchCols{};
 
   }; // class