chore: optimize and reorganize code for post and page service (#5498)

#### What type of PR is this?
/kind cleanup
/area core
/milestone 2.14.x

#### What this PR does / why we need it:
优化并重新整理文章和自定义页面 Service 的部分代码

#### Does this PR introduce a user-facing change?
```release-note
None
```

application/src/main/java/run/halo/app/content/ListedPost.java

@@ -5,6 +5,7 @@ import static io.swagger.v3.oas.annotations.media.Schema.RequiredMode.REQUIRED;
 import io.swagger.v3.oas.annotations.media.Schema;
 import java.util.List;
 import lombok.Data;
+import lombok.experimental.Accessors;
 import run.halo.app.core.extension.content.Category;
 import run.halo.app.core.extension.content.Post;
 import run.halo.app.core.extension.content.Tag;
@@ -17,6 +18,7 @@ import run.halo.app.core.extension.content.Tag;
  * @since 2.0.0
  */
 @Data
+@Accessors(chain = true)
 public class ListedPost {
 
     @Schema(requiredMode = REQUIRED)

application/src/main/java/run/halo/app/content/ListedSinglePage.java

@@ -5,6 +5,7 @@ import static io.swagger.v3.oas.annotations.media.Schema.RequiredMode.REQUIRED;
 import io.swagger.v3.oas.annotations.media.Schema;
 import java.util.List;
 import lombok.Data;
+import lombok.experimental.Accessors;
 import run.halo.app.core.extension.content.SinglePage;
 
 
@@ -15,6 +16,7 @@ import run.halo.app.core.extension.content.SinglePage;
  * @since 2.0.0
  */
 @Data
+@Accessors(chain = true)
 public class ListedSinglePage {
 
     @Schema(requiredMode = REQUIRED)

application/src/main/java/run/halo/app/content/impl/PostServiceImpl.java

@@ -94,48 +94,24 @@ public class PostServiceImpl extends AbstractContentService implements PostServi
 
     private Mono<ListedPost> getListedPost(Post post) {
         Assert.notNull(post, "The post must not be null.");
-        return Mono.just(post)
+        var listedPost = new ListedPost().setPost(post);
-            .map(p -> {
-                ListedPost listedPost = new ListedPost();
-                listedPost.setPost(p);
-                return listedPost;
-            })
-            .flatMap(lp -> fetchStats(post)
-                .doOnNext(lp::setStats)
-                .thenReturn(lp)
-            )
-            .flatMap(lp -> setTags(post.getSpec().getTags(), lp))
-            .flatMap(lp -> setCategories(post.getSpec().getCategories(), lp))
-            .flatMap(lp -> setContributors(post.getStatusOrDefault().getContributors(), lp))
-            .flatMap(lp -> setOwner(post.getSpec().getOwner(), lp));
-    }
 
-    private Mono<ListedPost> setTags(List<String> tagNames, ListedPost post) {
+        var statsMono = fetchStats(post)
-        return listTags(tagNames)
+            .doOnNext(listedPost::setStats);
+
+        var tagsMono = listTags(post.getSpec().getTags())
             .collectList()
-            .doOnNext(post::setTags)
+            .doOnNext(listedPost::setTags);
-            .map(tags -> post)
-            .switchIfEmpty(Mono.defer(() -> Mono.just(post)));
-    }
 
-    private Mono<ListedPost> setCategories(List<String> categoryNames, ListedPost post) {
+        var categoriesMono = listCategories(post.getSpec().getCategories())
-        return listCategories(categoryNames)
             .collectList()
-            .doOnNext(post::setCategories)
+            .doOnNext(listedPost::setCategories);
-            .map(categories -> post)
-            .switchIfEmpty(Mono.defer(() -> Mono.just(post)));
-    }
 
-    private Mono<ListedPost> setContributors(List<String> contributorNames, ListedPost post) {
+        var contributorsMono = listContributors(post.getStatusOrDefault().getContributors())
-        return listContributors(contributorNames)
             .collectList()
-            .doOnNext(post::setContributors)
+            .doOnNext(listedPost::setContributors);
-            .map(contributors -> post)
-            .switchIfEmpty(Mono.defer(() -> Mono.just(post)));
-    }
 
-    private Mono<ListedPost> setOwner(String ownerName, ListedPost post) {
+        var ownerMono = userService.getUserOrGhost(post.getSpec().getOwner())
-        return userService.getUserOrGhost(ownerName)
             .map(user -> {
                 Contributor contributor = new Contributor();
                 contributor.setName(user.getMetadata().getName());
@@ -143,8 +119,9 @@ public class PostServiceImpl extends AbstractContentService implements PostServi
                 contributor.setAvatar(user.getSpec().getAvatar());
                 return contributor;
             })
-            .doOnNext(post::setOwner)
+            .doOnNext(listedPost::setOwner);
-            .thenReturn(post);
+        return Mono.when(statsMono, tagsMono, categoriesMono, contributorsMono, ownerMono)
+            .thenReturn(listedPost);
     }
 
     private Flux<Tag> listTags(List<String> tagNames) {
@@ -184,15 +161,11 @@ public class PostServiceImpl extends AbstractContentService implements PostServi
     public Mono<Post> draftPost(PostRequest postRequest) {
         return Mono.defer(
                 () -> {
-                    Post post = postRequest.post();
+                    var post = postRequest.post();
                     return getContextUsername()
-                        .map(username -> {
+                        .doOnNext(username -> post.getSpec().setOwner(username))
-                            post.getSpec().setOwner(username);
+                        .thenReturn(post);
-                            return post;
+                })
-                        })
-                        .defaultIfEmpty(post);
-                }
-            )
             .flatMap(client::create)
             .flatMap(post -> {
                 if (postRequest.content() == null) {
@@ -292,22 +265,19 @@ public class PostServiceImpl extends AbstractContentService implements PostServi
 
     @Override
     public Mono<Post> publish(Post post) {
-        return Mono.just(post)
+        var spec = post.getSpec();
-            .doOnNext(p -> {
+        spec.setPublish(true);
-                var spec = post.getSpec();
+        if (spec.getHeadSnapshot() == null) {
-                spec.setPublish(true);
+            spec.setHeadSnapshot(spec.getBaseSnapshot());
-                if (spec.getHeadSnapshot() == null) {
+        }
-                    spec.setHeadSnapshot(spec.getBaseSnapshot());
+        spec.setReleaseSnapshot(spec.getHeadSnapshot());
-                }
+        return client.update(post);
-                spec.setReleaseSnapshot(spec.getHeadSnapshot());
-            }).flatMap(client::update);
     }
 
     @Override
     public Mono<Post> unpublish(Post post) {
-        return Mono.just(post)
+        post.getSpec().setPublish(false);
-            .doOnNext(p -> p.getSpec().setPublish(false))
+        return client.update(post);
-            .flatMap(client::update);
     }
 
     @Override

application/src/main/java/run/halo/app/content/impl/SinglePageServiceImpl.java

@@ -95,11 +95,8 @@ public class SinglePageServiceImpl extends AbstractContentService implements Sin
                 () -> {
                     SinglePage page = pageRequest.page();
                     return getContextUsername()
-                        .map(username -> {
+                        .doOnNext(username -> page.getSpec().setOwner(username))
-                            page.getSpec().setOwner(username);
+                        .thenReturn(page);
-                            return page;
-                        })
-                        .defaultIfEmpty(page);
                 }
             )
             .flatMap(client::create)
@@ -170,32 +167,17 @@ public class SinglePageServiceImpl extends AbstractContentService implements Sin
 
     private Mono<ListedSinglePage> getListedSinglePage(SinglePage singlePage) {
         Assert.notNull(singlePage, "The singlePage must not be null.");
-        return Mono.just(singlePage)
+        var listedSinglePage = new ListedSinglePage()
-            .map(sp -> {
+            .setPage(singlePage);
-                ListedSinglePage listedSinglePage = new ListedSinglePage();
-                listedSinglePage.setPage(singlePage);
-                return listedSinglePage;
-            })
-            .flatMap(sp -> fetchStats(singlePage)
-                .doOnNext(sp::setStats)
-                .thenReturn(sp)
-            )
-            .flatMap(lsp ->
-                setContributors(singlePage.getStatusOrDefault().getContributors(), lsp))
-            .flatMap(lsp -> setOwner(singlePage.getSpec().getOwner(), lsp));
-    }
 
-    private Mono<ListedSinglePage> setContributors(List<String> usernames,
+        var statsMono = fetchStats(singlePage)
-        ListedSinglePage singlePage) {
+            .doOnNext(listedSinglePage::setStats);
-        return listContributors(usernames)
+
+        var contributorsMono = listContributors(singlePage.getStatusOrDefault().getContributors())
             .collectList()
-            .doOnNext(singlePage::setContributors)
+            .doOnNext(listedSinglePage::setContributors);
-            .map(contributors -> singlePage)
-            .defaultIfEmpty(singlePage);
-    }
 
-    private Mono<ListedSinglePage> setOwner(String ownerName, ListedSinglePage page) {
+        var ownerMono = userService.getUserOrGhost(singlePage.getSpec().getOwner())
-        return userService.getUserOrGhost(ownerName)
             .map(user -> {
                 Contributor contributor = new Contributor();
                 contributor.setName(user.getMetadata().getName());
@@ -203,8 +185,9 @@ public class SinglePageServiceImpl extends AbstractContentService implements Sin
                 contributor.setAvatar(user.getSpec().getAvatar());
                 return contributor;
             })
-            .doOnNext(page::setOwner)
+            .doOnNext(listedSinglePage::setOwner);
-            .thenReturn(page);
+        return Mono.when(statsMono, contributorsMono, ownerMono)
+            .thenReturn(listedSinglePage);
     }
 
     Mono<Stats> fetchStats(SinglePage singlePage) {