Support lookup from layout-class to widget-class

Author: japhb

lib/Terminal/Widgets/WidgetRegistry.rakumod

@@ -13,10 +13,12 @@ my class RegistryEntry {
 my Lock:D $registry-lock .= new;  #= Lock controlling access to registry
 my        %registry;              #= Primary registry: moniker to RegistryEntry
 my        %layout-class;          #= Cache: builder-name to layout-class
+my        %widget-class{Any};     #= Cache: layout-class to widget-class
 
 
 #| Registry for Widget subclasses and matching Layout classes
 role Terminal::Widgets::WidgetRegistry {
+    #| Register a widget class and related details
     method register-widget(Str:D :$moniker!, Str:D :$builder-name!,
                            Any:U :$widget-class!, Any:U :$layout-class!) {
         my $entry = RegistryEntry.new(:$moniker, :$builder-name,
@@ -25,9 +27,13 @@ role Terminal::Widgets::WidgetRegistry {
         $registry-lock.protect: {
             %registry{$moniker}          = $entry;
             %layout-class{$builder-name} = $layout-class;
+            %widget-class{$layout-class} = $widget-class;
         }
     }
 
+
+    ### BASIC LOOKUPS
+
     method registry-entry(Str:D $moniker) {
         $registry-lock.protect: { %registry{$moniker} }
     }
@@ -36,6 +42,13 @@ role Terminal::Widgets::WidgetRegistry {
         $registry-lock.protect: { %layout-class{$builder-name} }
     }
 
+    method widget-for-layout($layout-class) {
+        $registry-lock.protect: { %widget-class{$layout-class} }
+    }
+
+
+    ### EXISTENCE CHECKS
+
     method widget-exists(Str:D $moniker) {
         $registry-lock.protect: { %registry{$moniker}:exists }
     }
@@ -44,6 +57,13 @@ role Terminal::Widgets::WidgetRegistry {
         $registry-lock.protect: { %layout-class{$builder-name}:exists }
     }
 
+    method layout-exists($layout-class) {
+        $registry-lock.protect: { %widget-class{$layout-class}:exists }
+    }
+
+
+    ### KNOWN TYPE ITERABLES
+
     method known-widgets() {
         $registry-lock.protect: { %registry.keys.sort }
     }
@@ -52,6 +72,17 @@ role Terminal::Widgets::WidgetRegistry {
         $registry-lock.protect: { %layout-class.keys.sort }
     }
 
+    method known-layout-classes() {
+        $registry-lock.protect: { %widget-class.keys }
+    }
+
+    method known-widget-classes() {
+        $registry-lock.protect: { %widget-class.values }
+    }
+
+
+    ### REGISTRY ENTRY ACCESSOR HELPERS
+
     method builder-name(Str:D $moniker) {
         my $entry = self.registry-entry($moniker);
         $entry ?? $entry.builder-name !! Nil