Add theme asset cache

- Use asset cache in Liquid head/foot tags
- Set 30-day cache header for theme assets

src/MyWebLog.Data/Data.fs

@@ -737,12 +737,26 @@ module Theme =
 /// Functions to manipulate theme assets
 module ThemeAsset =
     
+    open RethinkDb.Driver.Ast
+    
+    /// Match the ID by its prefix (the theme ID)
+    let private matchById themeId =
+        let keyPrefix = $"^{ThemeId.toString themeId}/"
+        fun (row : ReqlExpr) -> row["id"].Match keyPrefix :> obj
+    
+    /// List all theme assets (excludes data)
+    let all =
+        rethink<ThemeAsset list> {
+            withTable Table.ThemeAsset
+            without [ "data" ]
+            result; withRetryDefault
+        }
+    
     /// Delete all assets for a theme
     let deleteByTheme themeId =
-        let keyPrefix = $"^{ThemeId.toString themeId}/"
         rethink {
             withTable Table.ThemeAsset
-            filter (fun row -> row["id"].Match keyPrefix :> obj)
+            filter (matchById themeId)
             delete
             write; withRetryDefault; ignoreResult
         }
@@ -755,7 +769,16 @@ module ThemeAsset =
             resultOption; withRetryOptionDefault
         }
     
-    /// Save a theme assed
+    /// List all assets for a theme (data excluded)
+    let findByThemeId (themeId : ThemeId) =
+        rethink<ThemeAsset list> {
+            withTable Table.ThemeAsset
+            filter (matchById themeId)
+            without [ "data" ]
+            result; withRetryDefault
+        }
+    
+    /// Save a theme asset
     let save (asset : ThemeAsset) =
         rethink {
             withTable Table.ThemeAsset

src/MyWebLog/Caches.fs

@@ -131,3 +131,27 @@ module TemplateCache =
         |> List.ofSeq
         |> List.iter (fun key -> match _cache.TryRemove key with _, _ -> ())
 
+
+/// A cache of asset names by themes
+module ThemeAssetCache =
+    
+    /// A list of asset names for each theme
+    let private _cache = ConcurrentDictionary<ThemeId, string list> ()
+    
+    /// Retrieve the assets for the given theme ID
+    let get themeId = _cache[themeId]
+    
+    /// Refresh the list of assets for the given theme
+    let refreshTheme themeId conn = backgroundTask {
+        let! assets = Data.ThemeAsset.findByThemeId themeId conn
+        _cache[themeId] <- assets |> List.map (fun a -> match a.id with ThemeAssetId (_, path) -> path)
+    }
+    
+    /// Fill the theme asset cache
+    let fill conn = backgroundTask {
+        let! assets = Data.ThemeAsset.all conn
+        for asset in assets do
+            let (ThemeAssetId (themeId, path)) = asset.id
+            if not (_cache.ContainsKey themeId) then _cache[themeId] <- []
+            _cache[themeId] <- path :: _cache[themeId]
+    }

src/MyWebLog/DotLiquidBespoke.fs

@@ -14,7 +14,7 @@ let webLog (ctx : Context) =
 
 /// Does an asset exist for the current theme?
 let assetExists fileName (webLog : WebLog) =
-    File.Exists (Path.Combine ("wwwroot", "themes", webLog.themePath, fileName))
+    ThemeAssetCache.get (ThemeId webLog.themePath) |> List.exists (fun it -> it = fileName)
 
 /// Obtain the link from known types
 let permalink (ctx : Context) (item : obj) (linkFunc : WebLog -> Permalink -> string) =

src/MyWebLog/Handlers/Admin.fs

@@ -444,9 +444,11 @@ let updateTheme : HttpHandler = fun next ctx -> task {
         let themeName = themeFile.FileName.Split(".").[0].ToLowerInvariant().Replace (" ", "-")
         // TODO: add restriction for admin theme based on role
         if Regex.IsMatch (themeName, """^[a-z0-9\-]+$""") then
+            let conn   = ctx.Conn
             use stream = new MemoryStream ()
             do! themeFile.CopyToAsync stream
-            do! loadThemeFromZip themeName stream true ctx.Conn
+            do! loadThemeFromZip themeName stream true conn
+            do! ThemeAssetCache.refreshTheme (ThemeId themeName) conn
             do! addMessage ctx { UserMessage.success with message = "Theme updated successfully" }
             return! redirectToGet (WebLog.relativeUrl ctx.WebLog (Permalink "admin/dashboard")) next ctx
         else

src/MyWebLog/Handlers/Routes.fs

@@ -126,6 +126,10 @@ module Asset =
                 let headers = ResponseHeaders ctx.Response.Headers
                 headers.LastModified <- Some (DateTimeOffset asset.updatedOn) |> Option.toNullable
                 headers.ContentType  <- MediaTypeHeaderValue mimeType
+                headers.CacheControl <-
+                    let hdr = CacheControlHeaderValue()
+                    hdr.MaxAge <- Some (TimeSpan.FromDays 30) |> Option.toNullable
+                    hdr
                 return! setBody asset.data next ctx
         | None -> return! Error.notFound next ctx
     }

src/MyWebLog/Program.fs

@@ -63,6 +63,7 @@ let main args =
             let! conn = rethinkCfg.CreateConnectionAsync ()
             do! Data.Startup.ensureDb rethinkCfg (loggerFac.CreateLogger (nameof Data.Startup)) conn
             do! WebLogCache.fill conn
+            do! ThemeAssetCache.fill conn
             return conn
         } |> Async.AwaitTask |> Async.RunSynchronously
     let _ = builder.Services.AddSingleton<IConnection> conn