CAUSEWAY-4001: [Wicket Viewer] Bootstrap Theme Picker not supported when Default Theme is selected

viewers/wicket/ui/src/main/java/module-info.java

@@ -143,7 +143,7 @@
     requires spring.beans;
     requires spring.context;
     requires spring.core;
-    requires wicket.bootstrap.core;
+    requires transitive wicket.bootstrap.core;
     requires wicket.bootstrap.extensions;
     requires wicket.bootstrap.themes;
     requires de.agilecoders.wicket.webjars;

viewers/wicket/ui/src/main/java/org/apache/causeway/viewer/wicket/ui/CausewayModuleViewerWicketUi.java

@@ -18,27 +18,83 @@
  */
 package org.apache.causeway.viewer.wicket.ui;
 
+import java.util.List;
+
+import org.apache.wicket.markup.head.CssHeaderItem;
+import org.apache.wicket.markup.head.HeaderItem;
+import org.apache.wicket.markup.head.IHeaderResponse;
+
+import org.springframework.context.annotation.Bean;
 import org.springframework.context.annotation.Configuration;
 import org.springframework.context.annotation.Import;
 
 import org.apache.causeway.viewer.commons.services.CausewayModuleViewerCommonsServices;
 import org.apache.causeway.viewer.wicket.model.CausewayModuleViewerWicketModel;
 import org.apache.causeway.viewer.wicket.ui.app.logout.LogoutHandlerWkt;
-import org.apache.causeway.viewer.wicket.ui.components.widgets.themepicker.CausewayWicketThemeSupportDefault;
+import org.apache.causeway.viewer.wicket.ui.components.widgets.themepicker.CausewayWicketThemeSupport;
+
+import de.agilecoders.wicket.core.Bootstrap;
+import de.agilecoders.wicket.core.settings.ITheme;
+import de.agilecoders.wicket.core.settings.NoopThemeProvider;
+import de.agilecoders.wicket.core.settings.ThemeProvider;
+import de.agilecoders.wicket.themes.markup.html.bootswatch.BootswatchTheme;
+import de.agilecoders.wicket.themes.markup.html.bootswatch.BootswatchThemeProvider;
 
 /**
  * @since 1.x {@index}
  */
-@Configuration
+@Configuration(proxyBeanMethods = false)
 @Import({
         // Modules
         CausewayModuleViewerCommonsServices.class,
         CausewayModuleViewerWicketModel.class,
 
         // @Service's
-        CausewayWicketThemeSupportDefault.class,
+        CausewayWicketThemeSupport.class,
         LogoutHandlerWkt.class,
 })
 public class CausewayModuleViewerWicketUi {
 
+    @Bean
+    ThemeProvider bootstrapDefaultThemeProvider() {
+        return new BootstrapDefaultThemeProvider();
+    }
+
+    @Bean
+    ThemeProvider bootswatchThemeProvider() {
+        return new BootswatchThemeProvider(BootswatchTheme.Flatly);
+    }
+
+    /**
+     * Default Bootstrap Theme
+     *
+     * @see NoopThemeProvider
+     */
+    private static class BootstrapDefaultThemeProvider implements ThemeProvider {
+        private final ITheme theme = new BootstrapDefaultTheme();
+        @Override public ITheme byName(final String name) {
+            return theme;
+        }
+        @Override public List<ITheme> available() {
+            return List.of(theme);
+        }
+        @Override public ITheme defaultTheme() {
+            return theme;
+        }
+        private static final class BootstrapDefaultTheme implements ITheme {
+            @Override public String name() {
+                return "Default";
+            }
+            @Override public List<HeaderItem> getDependencies() {
+                return List.of();
+            }
+            @Override public void renderHead(final IHeaderResponse response) {
+                response.render(CssHeaderItem.forReference(Bootstrap.getSettings().getCssResourceReference()));
+            }
+            @Override public Iterable<String> getCdnUrls() {
+                return List.of();
+            }
+        }
+    }
+
 }

viewers/wicket/ui/src/main/java/org/apache/causeway/viewer/wicket/ui/components/widgets/themepicker/CausewayWicketThemeSupport.java

@@ -18,18 +18,147 @@
  */
 package org.apache.causeway.viewer.wicket.ui.components.widgets.themepicker;
 
+import java.util.HashSet;
+import java.util.LinkedHashMap;
 import java.util.List;
+import java.util.Map;
+import java.util.Optional;
+import java.util.stream.Collectors;
 
+import jakarta.inject.Inject;
+import jakarta.inject.Named;
+
+import org.apache.wicket.Component;
+import org.apache.wicket.util.string.Strings;
+
+import org.springframework.stereotype.Service;
+
+import org.apache.causeway.applib.services.registry.ServiceRegistry;
+import org.apache.causeway.commons.internal.base._NullSafe;
+import org.apache.causeway.core.config.CausewayConfiguration;
+
+import lombok.extern.slf4j.Slf4j;
+
+import de.agilecoders.wicket.core.Bootstrap;
+import de.agilecoders.wicket.core.settings.ITheme;
+import de.agilecoders.wicket.core.settings.NoopThemeProvider;
 import de.agilecoders.wicket.core.settings.ThemeProvider;
 
 /**
  * @since 2.0
  */
-public interface CausewayWicketThemeSupport {
+@Service
+@Named("causeway.viewer.wicket.CausewayWicketThemeSupport")
+@Slf4j
+public record CausewayWicketThemeSupport(
+        ITheme defaultTheme,
+        Map<String, ITheme> themeByNameLower,
+        Map<String, ThemeProvider> providerByThemeNameLower) {
+
+    @Inject
+    public CausewayWicketThemeSupport(final CausewayConfiguration configuration, final ServiceRegistry serviceRegistry) {
+        this(Args.create(configuration, serviceRegistry));
+    }
+
+    private CausewayWicketThemeSupport(final Args args) {
+        this(args.defaultTheme, args.themeByNameLower, args.providerByThemeNameLower);
+    }
+
+    public ITheme byName(final String name) {
+        if (!Strings.isEmpty(name)) {
+            var theme = themeByNameLower.get(name.toLowerCase());
+            if(theme!=null)
+                return theme;
+        }
+
+        log.warn("'{}' theme not found amoung enabled {}, "
+                + "falling back to '{}'",
+                name,
+                available().stream().map(ITheme::name).collect(Collectors.joining(", ")),
+                defaultTheme.name());
+
+        return defaultTheme;
+    }
+
+    public List<ITheme> available() {
+        return themeByNameLower.values()
+            .stream()
+            .toList();
+    }
+
+    public List<String> availableNames() {
+        return available()
+                .stream()
+                .map(ITheme::name)
+                .toList();
+    }
+
+    public ThemeProvider compositeThemeProvider() {
+        return new ThemeProvider() {
+            @Override public ITheme defaultTheme() {
+                return defaultTheme;
+            }
+            @Override public ITheme byName(final String name) {
+                return CausewayWicketThemeSupport.this.byName(name);
+            }
+            @Override public List<ITheme> available() {
+                return CausewayWicketThemeSupport.this.available();
+            }
+        };
+    }
+
+    /**
+     * Required in order for ThemeProvider specific resources to be made available.
+     *
+     * <p> set during {@link Component#beforeRender()}, un-set during {@link Component#afterRender()}
+     *
+     * @see #unsetCustomThemeProvider()
+     */
+    public void setCustomThemeProvider(final ITheme theme) {
+        Optional.ofNullable(providerByThemeNameLower.get(theme.name().toLowerCase()))
+            .ifPresent(Bootstrap.getSettings()::setThemeProvider);
+    }
+
+    public void unsetCustomThemeProvider() {
+        Bootstrap.getSettings().setThemeProvider(compositeThemeProvider());
+    }
+
+    // -- HELPER
+
+    /**
+     * Can be refactored/removed once we have flexible constructor bodies in Java.
+     */
+    private record Args(
+            ITheme defaultTheme,
+            Map<String, ITheme> themeByNameLower,
+            Map<String, ThemeProvider> providerByThemeNameLower) {
+
+        static Args create(
+                final CausewayConfiguration configuration,
+                final ServiceRegistry serviceRegistry) {
+
+            var enabledThemeNamesLowercase = _NullSafe.stream(configuration.viewer().wicket().themes().enabled())
+                    .map(String::toLowerCase)
+                    .collect(Collectors.toCollection(HashSet::new));
+
+            var providerByThemeNameLower = new LinkedHashMap<String, ThemeProvider>();
+            var themeByNameLower = new LinkedHashMap<String, ITheme>();
+            serviceRegistry.select(ThemeProvider.class)
+                .forEach(provider->{
+                    _NullSafe.stream(provider.available())
+                        .filter(theme->enabledThemeNamesLowercase.contains(theme.name().toLowerCase()))
+                        .forEach(theme->{
+                            var themeKey = theme.name().toLowerCase();
+                            themeByNameLower.put(themeKey, theme);
+                            providerByThemeNameLower.put(themeKey, provider);
+                        });
+                });
 
-    // -- INTERFACE
+            var defaultTheme = Optional.ofNullable(themeByNameLower.get(configuration.viewer().wicket().themes().initial()))
+                .orElseGet(()->new NoopThemeProvider().defaultTheme());
 
-    ThemeProvider getThemeProvider();
-    List<String> getEnabledThemeNames();
+            return new Args(defaultTheme, themeByNameLower, providerByThemeNameLower);
+        }
+    }
 
 }