Upload / delete themes (#20)

- Moved themes to section of installation admin page (will also implement #23 there)

src/MyWebLog.Data/Interfaces.fs

@@ -170,6 +170,12 @@ type IThemeData =
     /// Retrieve all themes (except "admin") (excluding the text of templates)
     abstract member All : unit -> Task<Theme list>
     
+    /// Delete a theme
+    abstract member Delete : ThemeId -> Task<bool>
+    
+    /// Determine if a theme exists
+    abstract member Exists : ThemeId -> Task<bool>
+    
     /// Find a theme by its ID
     abstract member FindById : ThemeId -> Task<Theme option>
     

src/MyWebLog.Data/RethinkDbData.fs

@@ -180,6 +180,14 @@ type RethinkDbData (conn : Net.IConnection, config : DataConfig, log : ILogger<R
     /// The batch size for restoration methods
     let restoreBatchSize = 100
     
+    /// Delete assets for the given theme ID
+    let deleteAssetsByTheme themeId = rethink {
+        withTable Table.ThemeAsset
+        filter (matchAssetByThemeId themeId)
+        delete
+        write; withRetryDefault; ignoreResult conn
+    }
+
     /// The connection for this instance
     member _.Conn = conn
     
@@ -720,6 +728,16 @@ type RethinkDbData (conn : Net.IConnection, config : DataConfig, log : ILogger<R
                     result; withRetryDefault conn
                 }
                 
+                member _.Exists themeId = backgroundTask {
+                    let! count = rethink<int> {
+                        withTable Table.Theme
+                        filter (nameof Theme.empty.Id) themeId
+                        count
+                        result; withRetryDefault conn
+                    }
+                    return count > 0
+                }
+                
                 member _.FindById themeId = rethink<Theme> {
                     withTable Table.Theme
                     get themeId
@@ -733,6 +751,20 @@ type RethinkDbData (conn : Net.IConnection, config : DataConfig, log : ILogger<R
                     resultOption; withRetryOptionDefault conn
                 }
                 
+                member this.Delete themeId = backgroundTask {
+                    match! this.FindByIdWithoutText themeId with
+                    | Some _ ->
+                        do! deleteAssetsByTheme themeId
+                        do! rethink {
+                            withTable Table.Theme
+                            get themeId
+                            delete
+                            write; withRetryDefault; ignoreResult conn
+                        }
+                        return true
+                    | None -> return false
+                }
+                
                 member _.Save theme = rethink {
                     withTable Table.Theme
                     get theme.Id
@@ -750,12 +782,7 @@ type RethinkDbData (conn : Net.IConnection, config : DataConfig, log : ILogger<R
                     result; withRetryDefault conn
                 }
                 
-                member _.DeleteByTheme themeId = rethink {
-                    withTable Table.ThemeAsset
-                    filter (matchAssetByThemeId themeId)
-                    delete
-                    write; withRetryDefault; ignoreResult conn
-                }
+                member _.DeleteByTheme themeId = deleteAssetsByTheme themeId
                 
                 member _.FindById assetId = rethink<ThemeAsset> {
                     withTable Table.ThemeAsset

src/MyWebLog.Data/SQLite/SQLiteThemeData.fs

@@ -26,6 +26,15 @@ type SQLiteThemeData (conn : SqliteConnection) =
                 { t with Templates = templates |> List.filter (fun tt -> fst tt = t.Id) |> List.map snd })
     }
     
+    /// Does a given theme exist?
+    let exists themeId = backgroundTask {
+        use cmd = conn.CreateCommand ()
+        cmd.CommandText <- "SELECT COUNT(id) FROM theme WHERE id = @id"
+        cmd.Parameters.AddWithValue ("@id", ThemeId.toString themeId) |> ignore
+        let! count = count cmd
+        return count > 0
+    }
+    
     /// Find a theme by its ID
     let findById themeId = backgroundTask {
         use cmd = conn.CreateCommand ()
@@ -53,6 +62,21 @@ type SQLiteThemeData (conn : SqliteConnection) =
         | None -> return None
     }
     
+    /// Delete a theme by its ID
+    let delete themeId = backgroundTask {
+        match! findByIdWithoutText themeId with
+        | Some _ ->
+            use cmd = conn.CreateCommand ()
+            cmd.CommandText <- """
+                DELETE FROM theme_asset    WHERE theme_id = @id;
+                DELETE FROM theme_template WHERE theme_id = @id;
+                DELETE FROM theme          WHERE id       = @id"""
+            cmd.Parameters.AddWithValue ("@id", ThemeId.toString themeId) |> ignore
+            do! write cmd
+            return true
+        | None -> return false
+    }
+    
     /// Save a theme
     let save (theme : Theme) = backgroundTask {
         use cmd = conn.CreateCommand ()
@@ -112,6 +136,8 @@ type SQLiteThemeData (conn : SqliteConnection) =
     
     interface IThemeData with
         member _.All () = all ()
+        member _.Delete themeId = delete themeId
+        member _.Exists themeId = exists themeId
         member _.FindById themeId = findById themeId
         member _.FindByIdWithoutText themeId = findByIdWithoutText themeId
         member _.Save theme = save theme