feat: allow theme preview for theme admins when preview is disabled (#7277)

#### What type of PR is this?
/kind feature
/area core
/milestone 2.20.x

#### What this PR does / why we need it:
支持禁用主题预览功能，但拥有主题管理权限的用户不受此功能影响

#### Which issue(s) this PR fixes:

Fixes #7204

#### Does this PR introduce a user-facing change?

```release-note
支持禁用主题预览功能，但拥有主题管理权限的用户不受此功能影响
```

api/src/main/java/run/halo/app/infra/SystemSetting.java

@@ -32,6 +32,7 @@ public class SystemSetting {
     public static class ThemeRouteRules {
         public static final String GROUP = "routeRules";
 
+        private boolean disableThemePreview;
         private String categories;
         private String archives;
         private String post;

application/src/main/java/run/halo/app/security/authorization/AuthorityUtils.java

@@ -28,6 +28,8 @@ public enum AuthorityUtils {
 
     public static final String POST_CONTRIBUTOR_ROLE_NAME = "role-template-post-contributor";
 
+    public static final String THEME_MANAGEMENT_ROLE_NAME = "role-template-manage-themes";
+
     /**
      * Converts an array of GrantedAuthority objects to a role set.
      *

application/src/main/java/run/halo/app/theme/ThemeResolver.java

@@ -1,14 +1,25 @@
 package run.halo.app.theme;
 
+import static run.halo.app.security.authorization.AuthorityUtils.authoritiesToRoles;
+
+import java.util.Collection;
+import java.util.Set;
 import lombok.AllArgsConstructor;
+import lombok.Builder;
 import org.apache.commons.lang3.StringUtils;
+import org.springframework.security.core.context.ReactiveSecurityContextHolder;
+import org.springframework.security.core.context.SecurityContext;
 import org.springframework.stereotype.Component;
 import org.springframework.util.Assert;
 import org.springframework.web.server.ServerWebExchange;
 import reactor.core.publisher.Mono;
+import run.halo.app.core.user.service.RoleService;
+import run.halo.app.infra.AnonymousUserConst;
 import run.halo.app.infra.SystemConfigurableEnvironmentFetcher;
 import run.halo.app.infra.SystemSetting.Theme;
+import run.halo.app.infra.SystemSetting.ThemeRouteRules;
 import run.halo.app.infra.ThemeRootGetter;
+import run.halo.app.security.authorization.AuthorityUtils;
 
 /**
  * @author johnniang
@@ -21,6 +32,7 @@ public class ThemeResolver {
     private final SystemConfigurableEnvironmentFetcher environmentFetcher;
 
     private final ThemeRootGetter themeRoot;
+    private final RoleService roleService;
 
     public Mono<ThemeContext> getThemeContext(String themeName) {
         Assert.hasText(themeName, "Theme name cannot be empty");
@@ -39,17 +51,17 @@ public class ThemeResolver {
 
     public Mono<ThemeContext> getTheme(ServerWebExchange exchange) {
         return fetchThemeFromExchange(exchange)
-            .switchIfEmpty(Mono.defer(() -> environmentFetcher.fetch(Theme.GROUP, Theme.class)
-                .map(Theme::getActive)
-                .switchIfEmpty(
-                    Mono.error(() -> new IllegalArgumentException("No theme activated")))
-                .map(activatedTheme -> {
+            .switchIfEmpty(Mono.defer(() -> fetchActivationState()
+                .map(themeState -> {
+                    var activatedTheme = themeState.activatedTheme();
                     var builder = ThemeContext.builder();
                     var themeName = exchange.getRequest().getQueryParams()
                         .getFirst(ThemeContext.THEME_PREVIEW_PARAM_NAME);
-                    if (StringUtils.isBlank(themeName)) {
+
+                    if (StringUtils.isBlank(themeName) || !themeState.supportsPreviewTheme()) {
                         themeName = activatedTheme;
                     }
+
                     boolean active = StringUtils.equals(activatedTheme, themeName);
                     var path = themeRoot.get().resolve(themeName);
                     return builder.name(themeName)
@@ -70,4 +82,44 @@ public class ThemeResolver {
             .cast(ThemeContext.class);
     }
 
+    private Mono<ThemeActivationState> fetchActivationState() {
+        var builder = ThemeActivationState.builder();
+
+        var activatedMono = environmentFetcher.fetch(Theme.GROUP, Theme.class)
+            .map(Theme::getActive)
+            .switchIfEmpty(Mono.error(() -> new IllegalArgumentException("No theme activated")))
+            .doOnNext(builder::activatedTheme);
+
+        var preivewDisabledMono = environmentFetcher.fetch(ThemeRouteRules.GROUP,
+                ThemeRouteRules.class)
+            .map(ThemeRouteRules::isDisableThemePreview)
+            .defaultIfEmpty(false)
+            .doOnNext(builder::previewDisabled);
+
+        var themeManageMono = ReactiveSecurityContextHolder.getContext()
+            .map(SecurityContext::getAuthentication)
+            .filter(au -> !AnonymousUserConst.isAnonymousUser(au.getName()))
+            .flatMap(au -> supportsPreviewTheme(authoritiesToRoles(au.getAuthorities())))
+            .doOnNext(builder::hasThemeManagementRole);
+
+        return Mono.when(activatedMono, preivewDisabledMono, themeManageMono)
+            .then(Mono.fromSupplier(builder::build));
+    }
+
+    private Mono<Boolean> supportsPreviewTheme(Collection<String> authorities) {
+        return roleService.contains(authorities, Set.of(AuthorityUtils.THEME_MANAGEMENT_ROLE_NAME))
+            .defaultIfEmpty(false);
+    }
+
+    @Builder
+    record ThemeActivationState(String activatedTheme, boolean previewDisabled,
+                                boolean hasThemeManagementRole) {
+
+        private boolean supportsPreviewTheme() {
+            if (hasThemeManagementRole) {
+                return true;
+            }
+            return !previewDisabled;
+        }
+    }
 }

application/src/main/resources/extensions/system-setting.yaml

@@ -142,6 +142,11 @@ spec:
     - group: routeRules
       label: 主题路由设置
       formSchema:
+        - $formkit: checkbox
+          label: "关闭主题预览"
+          value: false
+          name: disableThemePreview
+          help: "关闭后，未包含主题管理权限的用户将无法通过参数预览未激活的主题"
         - $formkit: text
           label: "分类页路由前缀"
           value: "categories"