fix: list as tree in category finder (#2537)

#### What type of PR is this?
/kind bug
/area core
/milestone 2.0

#### What this PR does / why we need it:
修复分类树查询
#### Which issue(s) this PR fixes:

Fixes #2532
#### Special notes for your reviewer:
how to test it?
1. 新建分类并，并拖动构建一个树形
2. 在主题端通过 `categoryFinder.listAsTree()` 查看结果是否正确

/cc @halo-dev/sig-halo 
#### Does this PR introduce a user-facing change?

```release-note
修复分类树状数据查询
```

src/main/java/run/halo/app/theme/finders/impl/CategoryFinderImpl.java

@@ -3,14 +3,13 @@ package run.halo.app.theme.finders.impl;
 import java.time.Instant;
 import java.util.Collection;
 import java.util.Comparator;
-import java.util.HashMap;
 import java.util.List;
 import java.util.Map;
 import java.util.Objects;
 import java.util.function.Function;
 import java.util.stream.Collectors;
+import lombok.extern.slf4j.Slf4j;
 import org.apache.commons.lang3.ObjectUtils;
-import org.springframework.util.CollectionUtils;
 import run.halo.app.core.extension.Category;
 import run.halo.app.extension.ListResult;
 import run.halo.app.extension.ReactiveExtensionClient;
@@ -25,6 +24,7 @@ import run.halo.app.theme.finders.vo.CategoryVo;
  * @author guqing
  * @since 2.0.0
  */
+@Slf4j
 @Finder("categoryFinder")
 public class CategoryFinderImpl implements CategoryFinder {
     private final ReactiveExtensionClient client;
@@ -75,40 +75,55 @@ public class CategoryFinderImpl implements CategoryFinder {
     @Override
     public List<CategoryTreeVo> listAsTree() {
         List<CategoryVo> categoryVos = listAll();
-        Map<String, CategoryVo> nameIdentityMap = categoryVos.stream()
+        Map<String, CategoryTreeVo> nameIdentityMap = categoryVos.stream()
+            .map(CategoryTreeVo::from)
             .collect(Collectors.toMap(categoryVo -> categoryVo.getMetadata().getName(),
                 Function.identity()));
 
-        Map<String, CategoryTreeVo> treeVoMap = new HashMap<>();
-        // populate parentName
-        categoryVos.forEach(categoryVo -> {
-            final String parentName = categoryVo.getMetadata().getName();
-            treeVoMap.putIfAbsent(parentName, CategoryTreeVo.from(categoryVo));
-            List<String> children = categoryVo.getSpec().getChildren();
-            if (CollectionUtils.isEmpty(children)) {
-                return;
+        nameIdentityMap.forEach((name, value) -> {
+            List<String> children = value.getSpec().getChildren();
+            if (children != null) {
+                for (String child : children) {
+                    CategoryTreeVo childNode = nameIdentityMap.get(child);
+                    childNode.setParentName(name);
+                }
             }
-            children.forEach(childrenName -> {
-                CategoryVo childrenVo = nameIdentityMap.get(childrenName);
-                CategoryTreeVo treeVo = CategoryTreeVo.from(childrenVo);
-                treeVo.setParentName(parentName);
-                treeVoMap.putIfAbsent(treeVo.getMetadata().getName(), treeVo);
-            });
         });
-        nameIdentityMap.clear();
-        return listToTree(treeVoMap.values());
+        return listToTree(nameIdentityMap.values());
     }
 
     static List<CategoryTreeVo> listToTree(Collection<CategoryTreeVo> list) {
-        Map<String, List<CategoryTreeVo>> nameIdentityMap = list.stream()
-            .filter(item -> item.getParentName() != null)
+        Map<String, List<CategoryTreeVo>> parentNameIdentityMap = list.stream()
+            .filter(categoryTreeVo -> categoryTreeVo.getParentName() != null)
             .collect(Collectors.groupingBy(CategoryTreeVo::getParentName));
-        list.forEach(node -> node.setChildren(nameIdentityMap.get(node.getMetadata().getName())));
+
+        list.forEach(node -> {
+            // sort children
+            List<CategoryTreeVo> children =
+                parentNameIdentityMap.getOrDefault(node.getMetadata().getName(), List.of())
+                    .stream()
+                    .sorted(defaultTreeNodeComparator())
+                    .toList();
+            node.setChildren(children);
+        });
         return list.stream()
             .filter(v -> v.getParentName() == null)
+            .sorted(defaultTreeNodeComparator())
             .collect(Collectors.toList());
     }
 
+    static Comparator<CategoryTreeVo> defaultTreeNodeComparator() {
+        Function<CategoryTreeVo, Integer> priority =
+            category -> Objects.requireNonNullElse(category.getSpec().getPriority(), 0);
+        Function<CategoryTreeVo, Instant> creationTimestamp =
+            category -> category.getMetadata().getCreationTimestamp();
+        Function<CategoryTreeVo, String> name =
+            category -> category.getMetadata().getName();
+        return Comparator.comparing(priority)
+            .thenComparing(creationTimestamp)
+            .thenComparing(name);
+    }
+
     static Comparator<Category> defaultComparator() {
         Function<Category, Integer> priority =
             category -> Objects.requireNonNullElse(category.getSpec().getPriority(), 0);

src/main/java/run/halo/app/theme/finders/vo/CategoryTreeVo.java

@@ -1,6 +1,7 @@
 package run.halo.app.theme.finders.vo;
 
 import java.util.List;
+import java.util.Objects;
 import lombok.Builder;
 import lombok.Data;
 import lombok.EqualsAndHashCode;
@@ -19,7 +20,7 @@ import run.halo.app.extension.MetadataOperator;
 @Builder
 @ToString
 @EqualsAndHashCode
-public class CategoryTreeVo {
+public class CategoryTreeVo implements VisualizableTreeNode<CategoryTreeVo> {
 
     private MetadataOperator metadata;
 
@@ -46,7 +47,12 @@ public class CategoryTreeVo {
             .spec(category.getSpec())
             .status(category.getStatus())
             .children(List.of())
-            .postCount(category.getPostCount())
+            .postCount(Objects.requireNonNullElse(category.getPostCount(), 0))
             .build();
     }
+
+    @Override
+    public String nodeText() {
+        return String.format("%s (%s)", getSpec().getDisplayName(), getPostCount());
+    }
 }

src/test/java/run/halo/app/theme/finders/impl/CategoryFinderImplTest.java

@@ -6,9 +6,11 @@ import static org.mockito.ArgumentMatchers.anyInt;
 import static org.mockito.ArgumentMatchers.eq;
 import static org.mockito.Mockito.when;
 
+import com.fasterxml.jackson.core.type.TypeReference;
 import java.time.Instant;
 import java.util.List;
 import java.util.Map;
+import java.util.Objects;
 import org.json.JSONException;
 import org.junit.jupiter.api.BeforeEach;
 import org.junit.jupiter.api.Test;
@@ -99,6 +101,28 @@ class CategoryFinderImplTest {
         assertThat(treeVos).hasSize(1);
     }
 
+    /**
+     * Test for {@link CategoryFinderImpl#listAsTree()}.
+     *
+     * @see <a href="https://github.com/halo-dev/halo/issues/2532">Fix #2532</a>
+     */
+    @Test
+    void listAsTreeMore() {
+        when(client.list(eq(Category.class), eq(null), any()))
+            .thenReturn(Flux.fromIterable(moreCategories()));
+        List<CategoryTreeVo> treeVos = categoryFinder.listAsTree();
+        String s = visualizeTree(treeVos);
+        assertThat(s).isEqualTo("""
+            全部 (5)
+            ├── FIT2CLOUD (2)
+            │   ├── DataEase (0)
+            │   ├── Halo (2)
+            │   ├── MeterSphere (0)
+            │   └── JumpServer (0)
+            └── 默认分类 (3)
+              """);
+    }
+
     private List<Category> categoriesForTree() {
         /*
          *  D
@@ -144,6 +168,30 @@ class CategoryFinderImplTest {
         return List.of(d, e, a, b, c, g, f, h);
     }
 
+    /**
+     * Visualize a tree.
+     */
+    String visualizeTree(List<CategoryTreeVo> categoryTreeVos) {
+        Category.CategorySpec categorySpec = new Category.CategorySpec();
+        categorySpec.setSlug("/");
+        categorySpec.setDisplayName("全部");
+        Integer postCount = categoryTreeVos.stream()
+            .map(CategoryTreeVo::getPostCount)
+            .filter(Objects::nonNull)
+            .reduce(Integer::sum)
+            .orElse(0);
+        CategoryTreeVo root = CategoryTreeVo.builder()
+            .spec(categorySpec)
+            .postCount(postCount)
+            .children(categoryTreeVos)
+            .metadata(new Metadata())
+            .build();
+        StringBuilder stringBuilder = new StringBuilder();
+        root.print(stringBuilder, "", "");
+        return stringBuilder.toString();
+    }
+
+
     private List<Category> categories() {
         Category category2 = JsonUtils.deepCopy(category());
         category2.getMetadata().setName("c2");
@@ -176,4 +224,176 @@ class CategoryFinderImplTest {
         category.setSpec(categorySpec);
         return category;
     }
+
+    private List<Category> moreCategories() {
+        String s = """
+            [
+               {
+                  "spec":{
+                     "displayName":"默认分类",
+                     "slug":"default",
+                     "description":"这是你的默认分类，如不需要，删除即可。",
+                     "cover":"",
+                     "template":"",
+                     "priority":1,
+                     "children":[
+                     ]
+                  },
+                  "status":{
+                     "permalink":"/categories/default",
+                     "postCount":3,
+                     "visiblePostCount":3
+                  },
+                  "apiVersion":"content.halo.run/v1alpha1",
+                  "kind":"Category",
+                  "metadata":{
+                     "name":"76514a40-6ef1-4ed9-b58a-e26945bde3ca",
+                     "version":16,
+                     "creationTimestamp":"2022-10-08T06:17:47.589181Z"
+                  }
+               },
+               {
+                  "spec":{
+                     "displayName":"MeterSphere",
+                     "slug":"metersphere",
+                     "description":"",
+                     "cover":"",
+                     "template":"",
+                     "priority":2,
+                     "children":[
+                     ]
+                  },
+                  "status":{
+                     "permalink":"/categories/metersphere",
+                     "postCount":0,
+                     "visiblePostCount":0
+                  },
+                  "apiVersion":"content.halo.run/v1alpha1",
+                  "kind":"Category",
+                  "metadata":{
+                     "finalizers":[
+                        "category-protection"
+                     ],
+                     "name":"acf09686-d5a7-4227-ba8c-3aeff063f12f",
+                     "version":13,
+                     "creationTimestamp":"2022-10-08T06:32:36.650974Z"
+                  }
+               },
+               {
+                  "spec":{
+                     "displayName":"DataEase",
+                     "slug":"dataease",
+                     "description":"",
+                     "cover":"",
+                     "template":"",
+                     "priority":0,
+                     "children":[
+                     ]
+                  },
+                  "status":{
+                     "permalink":"/categories/dataease",
+                     "postCount":0,
+                     "visiblePostCount":0
+                  },
+                  "apiVersion":"content.halo.run/v1alpha1",
+                  "kind":"Category",
+                  "metadata":{
+                     "finalizers":[
+                        "category-protection"
+                     ],
+                     "name":"bd95f914-22fc-4de5-afcc-a9ffba2f6401",
+                     "version":13,
+                     "creationTimestamp":"2022-10-08T06:32:53.353838Z"
+                  }
+               },
+               {
+                  "spec":{
+                     "displayName":"FIT2CLOUD",
+                     "slug":"fit2cloud",
+                     "description":"",
+                     "cover":"",
+                     "template":"",
+                     "priority":0,
+                     "children":[
+                        "bd95f914-22fc-4de5-afcc-a9ffba2f6401",
+                        "e1150fd9-4512-453c-9186-f8de9c156c3d",
+                        "acf09686-d5a7-4227-ba8c-3aeff063f12f",
+                        "ed064d5e-2b6f-4123-8114-78d0c6f2c4e2"
+                     ]
+                  },
+                  "status":{
+                     "permalink":"/categories/fit2cloud",
+                     "postCount":2,
+                     "visiblePostCount":2
+                  },
+                  "apiVersion":"content.halo.run/v1alpha1",
+                  "kind":"Category",
+                  "metadata":{
+                     "finalizers":[
+                        "category-protection"
+                     ],
+                     "name":"c25c17ae-4a7b-43c5-a424-76950b9622cd",
+                     "version":14,
+                     "creationTimestamp":"2022-10-08T06:32:27.802025Z"
+                  }
+               },
+               {
+                  "spec":{
+                     "displayName":"Halo",
+                     "slug":"halo",
+                     "description":"",
+                     "cover":"",
+                     "template":"",
+                     "priority":1,
+                     "children":[
+                     ]
+                  },
+                  "status":{
+                     "permalink":"/categories/halo",
+                     "postCount":2,
+                     "visiblePostCount":2
+                  },
+                  "apiVersion":"content.halo.run/v1alpha1",
+                  "kind":"Category",
+                  "metadata":{
+                     "finalizers":[
+                        "category-protection"
+                     ],
+                     "name":"e1150fd9-4512-453c-9186-f8de9c156c3d",
+                     "version":15,
+                     "creationTimestamp":"2022-10-08T06:32:42.991788Z"
+                  }
+               },
+               {
+                  "spec":{
+                     "displayName":"JumpServer",
+                     "slug":"jumpserver",
+                     "description":"",
+                     "cover":"",
+                     "template":"",
+                     "priority":3,
+                     "children":[
+                     ]
+                  },
+                  "status":{
+                     "permalink":"/categories/jumpserver",
+                     "postCount":0,
+                     "visiblePostCount":0
+                  },
+                  "apiVersion":"content.halo.run/v1alpha1",
+                  "kind":"Category",
+                  "metadata":{
+                     "finalizers":[
+                        "category-protection"
+                     ],
+                     "name":"ed064d5e-2b6f-4123-8114-78d0c6f2c4e2",
+                     "version":13,
+                     "creationTimestamp":"2022-10-08T06:33:00.557435Z"
+                  }
+               }
+            ]
+            """;
+        return JsonUtils.jsonToObject(s, new TypeReference<>() {
+        });
+    }
 }