#ifndef DataFormats_Common_OneToOneGeneric_h
#define DataFormats_Common_OneToOneGeneric_h

#include "DataFormats/Common/interface/AssociationMapHelpers.h"
#include "DataFormats/Common/interface/MapRefViewTrait.h"

#include <map>

namespace edm {
  template <typename CKey,
            typename CVal,
            typename index = unsigned int,
            typename KeyRefProd = typename helper::MapRefViewTrait<CKey>::refprod_type,
            typename ValRefProd = typename helper::MapRefViewTrait<CVal>::refprod_type,
            typename KeyRef = typename helper::MapRefViewTrait<CKey>::ref_type,
            typename ValRef = typename helper::MapRefViewTrait<CVal>::ref_type>
  class OneToOneGeneric {
    /// reference to "key" collection
    typedef KeyRefProd keyrefprod_type;
    /// reference to "value" collection
    typedef ValRefProd valrefprod_type;
    /// internal map associated data
    typedef index map_assoc;

  public:
    /// values reference collection type
    typedef ValRef val_type;
    /// insert key type
    typedef KeyRef key_type;
    /// insert val type
    typedef ValRef data_type;
    /// index type
    typedef index index_type;
    /// map type
    typedef std::map<index_type, map_assoc> map_type;
    /// reference set type
    typedef helpers::KeyVal<keyrefprod_type, valrefprod_type> ref_type;
    /// transient map type
    typedef std::map<typename CKey::value_type const*, typename CVal::value_type const*> transient_map_type;
    /// transient key vector
    typedef std::vector<typename CKey::value_type const*> transient_key_vector;
    /// transient val vector
    typedef std::vector<typename CVal::value_type const*> transient_val_vector;
    /// insert in the map
    static void insert(ref_type& ref, map_type& m, key_type const& k, data_type const& v) {
      if (k.isNull() || v.isNull()) {
        Exception::throwThis(errors::InvalidReference, "can't insert null references in AssociationMap");
      }
      if (ref.key.isNull()) {
        if (k.isTransient() || v.isTransient()) {
          Exception::throwThis(errors::InvalidReference,
                               "can't insert transient references in uninitialized AssociationMap");
        }
        //another thread might change the value of productGetter()
        auto getter = ref.key.productGetter();
        if (getter == nullptr) {
          Exception::throwThis(errors::LogicError,
                               "Can't insert into AssociationMap unless it was properly initialized.\n"
                               "The most common fix for this is to add arguments to the call to the\n"
                               "AssociationMap constructor that are valid Handle's to the containers.\n"
                               "If you don't have valid handles or either template parameter to the\n"
                               "AssociationMap is a View, then see the comments in AssociationMap.h.\n"
                               "(note this was a new requirement added in the 7_5_X release series)\n");
        }
        ref.key = KeyRefProd(k.id(), getter);
        ref.val = ValRefProd(v.id(), ref.val.productGetter());
      }
      helpers::checkRef(ref.key, k);
      helpers::checkRef(ref.val, v);
      index_type ik = index_type(k.key()), iv = index_type(v.key());
      m[ik] = iv;
    }
    /// return values collection
    static val_type val(ref_type const& ref, map_assoc iv) { return val_type(ref.val, iv); }
    /// size of data_type
    static typename map_type::size_type size(map_assoc const&) { return 1; }
    /// sort
    static void sort(map_type&) {}
    /// fill transient map
    static transient_map_type transientMap(ref_type const& ref, map_type const& map) {
      transient_map_type m;
      if (!map.empty()) {
        CKey const& ckey = *ref.key;
        CVal const& cval = *ref.val;
        for (typename map_type::const_iterator i = map.begin(); i != map.end(); ++i) {
          typename CKey::value_type const* k = &ckey[i->first];
          typename CVal::value_type const* v = &cval[i->second];
          m.insert(std::make_pair(k, v));
        }
      }
      return m;
    }
    /// fill transient key vector
    static transient_key_vector transientKeyVector(ref_type const& ref, map_type const& map) {
      transient_key_vector m;
      if (!map.empty()) {
        CKey const& ckey = *ref.key;
        for (typename map_type::const_iterator i = map.begin(); i != map.end(); ++i)
          m.push_back(&ckey[i->first]);
      }
      return m;
    }
    /// fill transient val vector
    static transient_val_vector transientValVector(ref_type const& ref, map_type const& map) {
      transient_val_vector m;
      if (!map.empty()) {
        CVal const& cval = *ref.val;
        for (typename map_type::const_iterator i = map.begin(); i != map.end(); ++i) {
          m.push_back(&cval[i->second]);
        }
      }
      return m;
    }
  };
}  // namespace edm

#endif
