Study: Add copy method to prepare scenario comparison.

src/Model/Study.py

@@ -44,7 +44,10 @@ class Study(SQLModel):
         River,
     ]
 
-    def __init__(self, filename=None, init_new=True):
+    def __init__(self, filename=None, init_new=True, copy=False):
+        if copy:
+            return
+
         # Metadata
         self.creation_date = datetime.now()
         self.last_modification_date = datetime.now()
@@ -476,31 +479,8 @@ class Study(SQLModel):
         return new
 
     def reload_from_scenario(self, scenario):
-        if scenario in self._river_scenario_cache:
+        river = self.load_scenario(scenario)
-            self._river = self._river_scenario_cache[scenario]
+        self._river = river
-            self.status.scenario = scenario
-        else:
-            def sql_exec(sql):
-                return self.execute(
-                    sql, fetch_one=False, commit=True
-                )
-
-            self.status.scenario = scenario
-            data = {
-                "status": self.status,
-                "loaded_pid": set(),
-                "scenario": scenario
-            }
-
-            # Reload river data
-            river = River._db_load(
-                sql_exec, data=data
-            )
-            data["study"] = self
-            river._db_load_results(sql_exec, data=data)
-
-            self._river_scenario_cache[scenario] = river
-            self._river = river
 
         if reduce(
                 lambda a, s: a or (s.parent is scenario),
@@ -511,6 +491,80 @@ class Study(SQLModel):
         else:
             self.status.set_as_editable()
 
+    def load_scenario(self, scenario):
+        if scenario in self._river_scenario_cache:
+            return self._river_scenario_cache[scenario]
+
+        def sql_exec(sql):
+            return self.execute(
+                sql, fetch_one=False, commit=True
+            )
+
+        old_scenario = self.status.scenario
+        self.status.scenario = scenario
+
+        data = {
+            "status": self.status,
+            "loaded_pid": set(),
+            "scenario": scenario
+        }
+
+        # Load river data
+        river = River._db_load(
+            sql_exec, data=data
+        )
+        data["study"] = self
+        river._db_load_results(sql_exec, data=data)
+
+        self._river_scenario_cache[scenario] = river
+        self.status.scenario = old_scenario
+
+        return river
+
+    def copy_from_scenario(self, scenario):
+        new = self._copy()
+
+        new._river = self.load_scenario(scenario)
+
+        def set_status(obj):
+            obj._status = new.status
+
+        new.river._data_traversal(
+            modifier=lambda obj, data: set_status(obj),
+        )
+
+        return new
+
+    def _copy(self):
+        """
+        This method make a copy of current study. This copy is like an
+        empty shell, it's not fully functional. Study object use
+        SQLite connection to file, this copy as no valid connection.
+
+        /!\ Please use this copy as read only object!
+        """
+        new = Study(copy=True)
+
+        new._filename = ""
+        new.creation_date = self.creation_date
+        new.last_modification_date = self.last_modification_date
+        new.last_save_date = self.last_save_date
+
+        new._name = self._name
+        new.description = self.description
+
+        new._time_system = self._time_system
+        new._date = self._date
+
+        new.status = StudyStatus()
+        new.scenarios = self.scenarios
+        new.status.scenario = self.status.scenario
+
+        new._river = self._river
+        new._river_scenario_cache = self._river_scenario_cache
+
+        return new
+
     def duplicate_current_scenario(self):
         source = self.status.scenario_id
         new = self.scenarios.new(