templates: move theme resolving logic into ThemeValues

this way users of the API can't forget to do it, this was intended from
the start but I forgot to adjust the prototype.

templates/middleware.go

@@ -44,20 +44,42 @@ func cookieDecode(value string) (theme string, overwrite_dj, overwrite_holiday b
 }
 
 type ThemeValues struct {
-	holiday util.TypedValue[radio.ThemeName]
-	dj      util.TypedValue[radio.ThemeName]
+	resolver func(string) string
+	holiday  util.TypedValue[radio.ThemeName]
+	dj       util.TypedValue[radio.ThemeName]
 }
 
-func NewThemeValues() *ThemeValues {
-	return &ThemeValues{}
+func NewThemeValues(resolver func(string) string) *ThemeValues {
+	if resolver == nil {
+		resolver = func(s string) string { return s }
+	}
+
+	return &ThemeValues{
+		resolver: resolver,
+	}
+}
+
+func (tv *ThemeValues) resolve(theme radio.ThemeName) radio.ThemeName {
+	if theme == "" {
+		return theme
+	}
+	// resolve the theme that was passed in
+	resolved := tv.resolver(theme)
+	if resolved != theme {
+		// if input and output are not the same it means the theme didn't exist
+		// and we shouldn't use it, so just unset it
+		return ""
+	}
+
+	return resolved
 }
 
 func (tv *ThemeValues) StoreHoliday(theme radio.ThemeName) {
-	tv.holiday.Store(theme)
+	tv.holiday.Store(tv.resolve(theme))
 }
 
 func (tv *ThemeValues) StoreDJ(theme radio.ThemeName) {
-	tv.dj.Store(theme)
+	tv.dj.Store(tv.resolve(theme))
 }
 
 // ThemeCtx adds a theme entry into the context of the request, that is acquirable by

templates/middleware_test.go

@@ -87,7 +87,7 @@ func BenchmarkCookieEncode(b *testing.B) {
 
 func BenchmarkDecideTheme(b *testing.B) {
 	fn := func(holiday, user radio.ThemeName) func(radio.ThemeName) radio.ThemeName {
-		tv := NewThemeValues()
+		tv := NewThemeValues(nil)
 		tv.StoreHoliday(holiday)
 		tv.StoreDJ(user)
 		return tv.decide

website/main.go

@@ -73,9 +73,6 @@ func Execute(ctx context.Context, cfg config.Config) error {
 	// status RPC value
 	statusValue := util.StreamValue(ctx, cfg.Manager.CurrentStatus)
 
-	// template value, for deciding what theme to use
-	themeValues := templates.NewThemeValues()
-
 	// templates
 	// construct our stateful template functions, it uses the latest values from the manager
 	templateFuncs := templates.NewStatefulFunctions(statusValue)
@@ -89,6 +86,8 @@ func Execute(ctx context.Context, cfg config.Config) error {
 	}
 	executor := siteTemplates.Executor()
 
+	// template value, for deciding what theme to use
+	themeValues := templates.NewThemeValues(siteTemplates.ResolveThemeName)
 	// user RPC value
 	_ = util.StreamValue(ctx, cfg.Manager.CurrentUser, func(ctx context.Context, u *radio.User) {
 		// if either no user, or no theme set, unset the DJ theme
@@ -97,16 +96,7 @@ func Execute(ctx context.Context, cfg config.Config) error {
 			return
 		}
 
-		// check if the theme configured by the DJ actually exists
-		resolved := siteTemplates.ResolveThemeName(u.DJ.Theme)
-		if resolved != u.DJ.Theme {
-			// if input and output are not the same it means the theme didn't exist
-			// and we shouldn't use it, so just unset it
-			themeValues.StoreDJ("")
-			return
-		}
-
-		themeValues.StoreDJ(resolved)
+		themeValues.StoreDJ(u.DJ.Theme)
 	})
 
 	// daypass generation