feat: add RSS feed for subscribing to post lists by tag slug

app/src/main/java/run/halo/feed/provider/TagPostRssProvider.java

@@ -0,0 +1,71 @@
+package run.halo.feed.provider;
+
+import org.springframework.lang.NonNull;
+import org.springframework.stereotype.Component;
+import org.springframework.web.reactive.function.server.ServerRequest;
+import reactor.core.publisher.Flux;
+import reactor.core.publisher.Mono;
+import run.halo.app.content.PostContentService;
+import run.halo.app.extension.ListResult;
+import run.halo.app.extension.ReactiveExtensionClient;
+import run.halo.app.infra.ExternalLinkProcessor;
+import run.halo.app.infra.ExternalUrlSupplier;
+import run.halo.app.infra.SystemInfoGetter;
+import run.halo.app.plugin.ReactiveSettingFetcher;
+import run.halo.feed.BasicProp;
+import run.halo.feed.RSS2;
+import run.halo.feed.RssRouteItem;
+import run.halo.feed.service.PostService;
+
+@Component
+public class TagPostRssProvider extends AbstractPostRssProvider implements RssRouteItem {
+
+    public TagPostRssProvider(PostService postService, ReactiveExtensionClient client,
+        ExternalLinkProcessor externalLinkProcessor, ReactiveSettingFetcher settingFetcher,
+        PostContentService postContentService, ExternalUrlSupplier externalUrlSupplier,
+        SystemInfoGetter systemInfoGetter) {
+        super(postService, client, externalLinkProcessor, settingFetcher, postContentService,
+            externalUrlSupplier, systemInfoGetter);
+    }
+
+    @Override
+    public Mono<String> pathPattern() {
+        return BasicProp.getBasicProp(settingFetcher)
+            .filter(BasicProp::isEnableCategories)
+            .map(prop -> "/tags/{slug}.xml");
+    }
+
+    @Override
+    @NonNull
+    public String displayName() {
+        return "标签文章订阅";
+    }
+
+    @Override
+    public String description() {
+        return "按标签订阅站点文章";
+    }
+
+    public Mono<RSS2> handler(ServerRequest request) {
+        var slug = request.pathVariable("slug");
+        return super.handler(request)
+            .flatMap(rss2 -> postService.getTagBySlug(slug)
+                .doOnNext(tag -> {
+                    var displayName = tag.getSpec().getDisplayName();
+                    var permalink = tag.getStatusOrDefault().getPermalink();
+                    rss2.setTitle("标签：" + displayName + " - " + rss2.getTitle());
+                    rss2.setLink(externalLinkProcessor.processLink(permalink));
+                })
+                .thenReturn(rss2)
+            );
+    }
+
+    @Override
+    protected Flux<PostWithContent> listPosts(ServerRequest request) {
+        var tagSlug = request.pathVariable("slug");
+        return listPostsByFunc(basicProp ->
+            postService.listPostByTagSlug(basicProp.getOutputNum(), tagSlug)
+                .flatMapIterable(ListResult::getItems)
+        );
+    }
+}

app/src/main/java/run/halo/feed/service/PostService.java

@@ -3,14 +3,19 @@
 import reactor.core.publisher.Mono;
 import run.halo.app.core.extension.content.Category;
 import run.halo.app.core.extension.content.Post;
+import run.halo.app.core.extension.content.Tag;
 import run.halo.app.extension.ListResult;
 
 public interface PostService {
     Mono<ListResult<Post>> listPosts(int size);
 
     Mono<ListResult<Post>> listPostByCategorySlug(int size, String categorySlug);
 
+    Mono<ListResult<Post>> listPostByTagSlug(int size, String tagSlug);
+
     Mono<ListResult<Post>> listPostByAuthor(int size, String author);
 
     Mono<Category> getCategoryBySlug(String categorySlug);
+
+    Mono<Tag> getTagBySlug(String slug);
 }

app/src/main/java/run/halo/feed/service/PostServiceImpl.java

@@ -11,6 +11,7 @@
 import reactor.core.publisher.Mono;
 import run.halo.app.core.extension.content.Category;
 import run.halo.app.core.extension.content.Post;
+import run.halo.app.core.extension.content.Tag;
 import run.halo.app.extension.ListOptions;
 import run.halo.app.extension.ListResult;
 import run.halo.app.extension.PageRequestImpl;
@@ -39,6 +40,17 @@ public Mono<ListResult<Post>> listPostByCategorySlug(int size, String categorySl
             });
     }
 
+    @Override
+    public Mono<ListResult<Post>> listPostByTagSlug(int size, String slug) {
+        return getTagBySlug(slug)
+            .flatMap(tag -> {
+                var tagName = tag.getMetadata().getName();
+                return client.listBy(Post.class,
+                    buildPostListOptions(in("spec.tags", tagName)),
+                    PageRequestImpl.ofSize(size).withSort(defaultSort()));
+            });
+    }
+
     @Override
     public Mono<ListResult<Post>> listPostByAuthor(int size, String author) {
         return client.listBy(Post.class, buildPostListOptions(in("spec.owner", author)),
@@ -55,6 +67,16 @@ public Mono<Category> getCategoryBySlug(String categorySlug) {
             .flatMap(listResult -> Mono.justOrEmpty(ListResult.first(listResult)));
     }
 
+    @Override
+    public Mono<Tag> getTagBySlug(String slug) {
+        return client.listBy(Tag.class, ListOptions.builder()
+                    .fieldQuery(equal("spec.slug", slug))
+                    .build(),
+                PageRequestImpl.ofSize(1)
+            )
+            .flatMap(listResult -> Mono.justOrEmpty(ListResult.first(listResult)));
+    }
+
     ListOptions buildPostListOptions() {
         return buildPostListOptions(null);
     }

app/src/main/resources/extensions/ext-definition.yaml

@@ -21,6 +21,16 @@ spec:
 ---
 apiVersion: plugin.halo.run/v1alpha1
 kind: ExtensionDefinition
+metadata:
+  name: feed-tag-post-rss-item
+spec:
+  className: run.halo.feed.provider.TagPostRssProvider
+  extensionPointName: feed-rss-route-item
+  displayName: "标签文章订阅"
+  description: "用于生成按照标签订阅文章列表的 RSS 订阅源"
+---
+apiVersion: plugin.halo.run/v1alpha1
+kind: ExtensionDefinition
 metadata:
   name: feed-author-post-rss-item
 spec: