list_active_sons api call implementation

libraries/wallet/include/graphene/wallet/wallet.hpp

@@ -1363,6 +1363,13 @@ class wallet_api
        */
       map<string, son_id_type> list_sons(const string& lowerbound, uint32_t limit);
 
+      /** Lists active at the moment SONs.
+       * This returns a list of all account names that own active SON, and the associated SON id,
+       * sorted by name.
+       * @returns a list of active SONs mapping SON names to SON ids
+       */
+      map<string, son_id_type> list_active_sons();
+
       /** Creates a witness object owned by the given account.
        *
        * An account can have at most one witness object.

libraries/wallet/wallet.cpp

@@ -1932,6 +1932,32 @@ public:
       return sign_transaction( tx, broadcast );
    } FC_CAPTURE_AND_RETHROW( (owner_account)(broadcast) ) }
 
+   map<string, son_id_type> list_active_sons()
+   { try {
+           global_property_object gpo = get_global_properties();
+           std::vector<fc::optional<son_object>> son_objects =
+                   _remote_db->get_sons(gpo.active_sons);
+           vector<account_id_type> owners;
+           owners.resize(son_objects.size());
+           std::transform(son_objects.begin(), son_objects.end(), owners.begin(),
+                          [](const fc::optional<son_object>& obj) {
+                                if(!obj)
+                                    FC_THROW("Invalid active SONs list in global properties.");
+                                return obj->son_account;
+                          });
+           vector<fc::optional<account_object>> accs = _remote_db->get_accounts(owners);
+           map<string, son_id_type> result;
+           std::transform(accs.begin(), accs.end(), gpo.active_sons.begin(),
+                          std::inserter(result, result.end()),
+                          [](fc::optional<account_object>& acct,
+                          son_id_type& sid) {
+                               if(!acct)
+                                   FC_THROW("Invalid active SONs list in global properties.");
+                               return std::make_pair<string, son_id_type>(string(acct->name), std::move(sid));
+                           });
+           return result;
+   } FC_CAPTURE_AND_RETHROW() }
+
    signed_transaction create_witness(string owner_account,
                                      string url,
                                      bool broadcast /* = false */)
@@ -4303,6 +4329,11 @@ map<string, son_id_type> wallet_api::list_sons(const string& lowerbound, uint32_
    return my->_remote_db->lookup_son_accounts(lowerbound, limit);
 }
 
+map<string, son_id_type> wallet_api::list_active_sons()
+{
+    return my->list_active_sons();
+}
+
 signed_transaction wallet_api::create_witness(string owner_account,
                                               string url,
                                               bool broadcast /* = false */)