Reassign child cats when deleting parent cat (#27)

- Create common page/post edit field template (#25)
- Fix relative URL adjustment throughout
- Fix upload name sanitization regex
- Create modules within Admin handler module
- Enable/disable podcast episode fields on page load
- Fix upload destination casing in templates
- Tweak default theme to show no posts found on index template
- Update Bootstrap to 5.1.3 in default theme

src/MyWebLog.Data/Interfaces.fs

@@ -5,6 +5,16 @@ open System.Threading.Tasks
 open MyWebLog
 open MyWebLog.ViewModels
 
+/// The result of a category deletion attempt
+type CategoryDeleteResult =
+    /// The category was deleted successfully
+    | CategoryDeleted
+    /// The category was deleted successfully, and its children were reassigned to its parent
+    | ReassignedChildCategories
+    /// The category was not found, so no effort was made to delete it
+    | CategoryNotFound
+
+
 /// Data functions to support manipulating categories
 type ICategoryData =
     
@@ -18,7 +28,7 @@ type ICategoryData =
     abstract member CountTopLevel : WebLogId -> Task<int>
     
     /// Delete a category (also removes it from posts)
-    abstract member Delete : CategoryId -> WebLogId -> Task<bool>
+    abstract member Delete : CategoryId -> WebLogId -> Task<CategoryDeleteResult>
     
     /// Find all categories for a web log, sorted alphabetically and grouped by hierarchy
     abstract member FindAllForView : WebLogId -> Task<DisplayCategory[]>

src/MyWebLog.Data/RethinkDbData.fs

@@ -274,7 +274,21 @@ type RethinkDbData (conn : Net.IConnection, config : DataConfig, log : ILogger<R
                 
                 member this.Delete catId webLogId = backgroundTask {
                     match! this.FindById catId webLogId with
-                    | Some _ ->
+                    | Some cat ->
+                        // Reassign any children to the category's parent category
+                        let! children = rethink<int> {
+                            withTable Table.Category
+                            filter (nameof Category.empty.ParentId) catId
+                            count
+                            result; withRetryDefault conn
+                        }
+                        if children > 0 then
+                            do! rethink {
+                                withTable Table.Category
+                                filter (nameof Category.empty.ParentId) catId
+                                update [ nameof Category.empty.ParentId, cat.ParentId :> obj ]
+                                write; withRetryDefault; ignoreResult conn
+                            }
                         // Delete the category off all posts where it is assigned
                         do! rethink {
                             withTable Table.Post
@@ -291,8 +305,8 @@ type RethinkDbData (conn : Net.IConnection, config : DataConfig, log : ILogger<R
                             delete
                             write; withRetryDefault; ignoreResult conn
                         }
-                        return true
-                    | None -> return false
+                        return if children = 0 then CategoryDeleted else ReassignedChildCategories
+                    | None -> return CategoryNotFound
                 }
                 
                 member _.Restore cats = backgroundTask {

src/MyWebLog.Data/SQLite/SQLiteCategoryData.fs

@@ -122,13 +122,23 @@ type SQLiteCategoryData (conn : SqliteConnection) =
     /// Delete a category
     let delete catId webLogId = backgroundTask {
         match! findById catId webLogId with
-        | Some _ ->
+        | Some cat ->
             use cmd = conn.CreateCommand ()
+            // Reassign any children to the category's parent category
+            cmd.CommandText <- "SELECT COUNT(id) FROM category WHERE parent_id = @parentId"
+            cmd.Parameters.AddWithValue ("@parentId", CategoryId.toString catId) |> ignore
+            let! children = count cmd
+            if children > 0 then
+                cmd.CommandText <- "UPDATE category SET parent_id = @newParentId WHERE parent_id = @parentId"
+                cmd.Parameters.AddWithValue ("@newParentId", maybe (cat.ParentId |> Option.map CategoryId.toString))
+                |> ignore
+                do! write cmd
             // Delete the category off all posts where it is assigned
             cmd.CommandText <- """
                 DELETE FROM post_category
                  WHERE category_id = @id
                    AND post_id IN (SELECT id FROM post WHERE web_log_id = @webLogId)"""
+            cmd.Parameters.Clear ()
             let catIdParameter = cmd.Parameters.AddWithValue ("@id", CategoryId.toString catId)
             cmd.Parameters.AddWithValue ("@webLogId", WebLogId.toString webLogId) |> ignore
             do! write cmd
@@ -137,8 +147,8 @@ type SQLiteCategoryData (conn : SqliteConnection) =
             cmd.Parameters.Clear ()
             cmd.Parameters.Add catIdParameter |> ignore
             do! write cmd
-            return true
-        | None -> return false
+            return if children = 0 then CategoryDeleted else ReassignedChildCategories
+        | None -> return CategoryNotFound
     }
     
     /// Restore categories from a backup