Add basic merge feature to MasterView

tailbone/views/master.py

@@ -55,6 +55,7 @@ class MasterView(View):
     viewable = True
     editable = True
     deletable = True
+    mergeable = False
 
     listing = False
     creating = False
@@ -394,6 +395,70 @@ class MasterView(View):
             'instance_title': instance_title,
             'form': form})
 
+    def get_merge_fields(self):
+        if hasattr(self, 'merge_fields'):
+            return self.merge_fields
+
+    def get_merge_coalesce_fields(self):
+        if hasattr(self, 'merge_coalesce_fields'):
+            return self.merge_coalesce_fields
+        return []
+
+    def merge(self):
+        """
+        Preview and execute a merge of two records.
+        """
+        object_to_remove = object_to_keep = None
+        if self.request.method == 'POST':
+            uuids = self.request.POST.get('uuids', '').split(',')
+            if len(uuids) == 2:
+                object_to_remove = self.Session.query(self.get_model_class()).get(uuids[0])
+                object_to_keep = self.Session.query(self.get_model_class()).get(uuids[1])
+
+                if object_to_remove and object_to_keep and self.request.POST.get('commit-merge') == 'yes':
+                    msg = unicode(object_to_remove)
+                    try:
+                        self.validate_merge(object_to_remove, object_to_keep)
+                    except Exception as error:
+                        self.request.session.flash("Requested merge cannot proceed (maybe swap keep/remove and try again?): {}".format(error), 'error')
+                    else:
+                        self.merge_objects(object_to_remove, object_to_keep)
+                        self.request.session.flash("{} has been merged into {}".format(msg, object_to_keep))
+                        return self.redirect(self.get_action_url('view', object_to_keep))
+
+        if not object_to_remove or not object_to_keep or object_to_remove is object_to_keep:
+            return self.redirect(self.get_index_url())
+
+        remove = self.get_merge_data(object_to_remove)
+        keep = self.get_merge_data(object_to_keep)
+        return self.render_to_response('merge', {'object_to_remove': object_to_remove,
+                                                 'object_to_keep': object_to_keep,
+                                                 'view_url': lambda obj: self.get_action_url('view', obj),
+                                                 'merge_fields': self.get_merge_fields(),
+                                                 'remove_data': remove,
+                                                 'keep_data': keep,
+                                                 'resulting_data': self.get_merge_resulting_data(remove, keep)})
+
+    def validate_merge(self, removing, keeping):
+        """
+        If applicable, your view should override this in order to confirm that
+        the requested merge is valid, in your context.  If it is not - for *any
+        reason* - you should raise an exception; the type does not matter.
+        """
+
+    def get_merge_data(self, obj):
+        raise NotImplementedError("please implement `{}.get_merge_data()`".format(self.__class__.__name__))
+
+    def get_merge_resulting_data(self, remove, keep):
+        result = dict(keep)
+        for field in self.get_merge_coalesce_fields():
+            if remove[field] and not keep[field]:
+                result[field] = remove[field]
+        return result
+
+    def merge_objects(self, removing, keeping):
+        raise NotImplementedError("please implement `{}.merge_objects()`".format(self.__class__.__name__))
+
     ##############################
     # Core Stuff
     ##############################
@@ -635,7 +700,8 @@ class MasterView(View):
             'default_sortkey': getattr(self, 'default_sortkey', None),
             'sortdir': getattr(self, 'sortdir', 'asc'),
             'pageable': self.pageable,
-            'checkboxes': self.checkboxes,
+            'checkboxes': self.checkboxes or (
+                self.mergeable and self.request.has_perm('{}.merge'.format(self.get_permission_prefix()))),
             'checked': self.checked,
             'row_attrs': self.get_row_attrs,
             'cell_attrs': self.get_cell_attrs,
@@ -662,8 +728,12 @@ class MasterView(View):
         defined; it depends on the type of data the grid deals with.
         """
         if callable(self.row_attrs):
-            return self.row_attrs(row, i)
-        return self.row_attrs
+            attrs = self.row_attrs(row, i)
+        else:
+            attrs = dict(self.row_attrs)
+        if self.mergeable:
+            attrs['data-uuid'] = row.uuid
+        return attrs
 
     def get_cell_attrs(self, row, column):
         """
@@ -1142,6 +1212,14 @@ class MasterView(View):
             config.add_tailbone_permission(permission_prefix, '{0}.create'.format(permission_prefix),
                                            "Create new {0}".format(model_title))
 
+        # merge
+        if cls.mergeable:
+            config.add_route('{}.merge'.format(route_prefix), '{}/merge'.format(url_prefix))
+            config.add_view(cls, attr='merge', route_name='{}.merge'.format(route_prefix),
+                            permission='{}.merge'.format(permission_prefix))
+            config.add_tailbone_permission(permission_prefix, '{}.merge'.format(permission_prefix),
+                                           "Merge 2 {}".format(model_title_plural))
+
         # view
         if cls.viewable:
             config.add_tailbone_permission(permission_prefix, '{}.view'.format(permission_prefix),