Refactor the response structure of Extension list API (#2244)

#### What type of PR is this?

/kind improvement
/kind api-change
/area core
/milestone 2.0

#### What this PR does / why we need it:

This PR is refactoring the response structure of Extension list API as follows:

```json
{
  "page": 0,
  "size": 0,
  "total": 1,
  "items": [
    {
      "spec": {
        "displayName": "Administrator",
        "email": "admin@halo.run",
        "password": "{bcrypt}$2a$10$/YveWyuf9vyYrHE3fiToI.bGBy5Hgs1eViRvKzU7Kl982la5NSwWO",
        "registeredAt": "2022-06-17T09:35:47.237625514Z",
        "twoFactorAuthEnabled": false,
        "disabled": false
      },
      "apiVersion": "v1alpha1",
      "kind": "User",
      "metadata": {
        "name": "admin",
        "annotations": {
          "user.halo.run/roles": "[\"super-role\"]",
          "rbac.authorization.halo.run/role-names": "[\"second-super-role\",\"super-role\"]"
        },
        "version": 3077,
        "creationTimestamp": "2022-06-17T09:35:47.367919552Z"
      }
    }
  ],
  "first": true,
  "last": true,
  "hasNext": false,
  "hasPrevious": false
}
```

Instead of items only.

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

Fixes #

#### Special notes for your reviewer:

Steps to test:

1. Start Halo server
2. Request <http://localhost:8090/swagger-ui.html> from browser and you might be redirected to login page
3. Login with your username and password
4. Try to request the list endpoints and see the result.

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

```release-note
None
```

src/main/java/run/halo/app/extension/DefaultExtensionClient.java

@@ -5,9 +5,6 @@ import java.util.Comparator;
 import java.util.List;
 import java.util.Optional;
 import java.util.function.Predicate;
-import org.springframework.data.domain.Page;
-import org.springframework.data.domain.PageRequest;
-import org.springframework.data.support.PageableExecutionUtils;
 import org.springframework.util.Assert;
 import run.halo.app.extension.store.ExtensionStoreClient;
 
@@ -53,14 +50,19 @@ public class DefaultExtensionClient implements ExtensionClient {
     }
 
     @Override
-    public <E extends Extension> Page<E> page(Class<E> type, Predicate<E> predicate,
+    public <E extends Extension> ListResult<E> list(Class<E> type, Predicate<E> predicate,
         Comparator<E> comparators, int page, int size) {
-        var pageable = PageRequest.of(page, size);
+        var extensions = list(type, predicate, comparators);
-        var all = list(type, predicate, comparators);
+        var extensionStream = extensions.stream();
-        var total = all.size();
+        if (page > 0) {
-        var content =
+            extensionStream = extensionStream.skip(((long) (page - 1)) * (long) size);
-            all.stream().limit(pageable.getPageSize()).skip(pageable.getOffset()).toList();
+        }
-        return PageableExecutionUtils.getPage(content, pageable, () -> total);
+        if (size > 0) {
+            extensionStream = extensionStream.limit(size);
+        }
+        var content = extensionStream.toList();
+
+        return new ListResult<>(page, size, extensions.size(), content);
     }
 
     @Override

src/main/java/run/halo/app/extension/ExtensionClient.java

@@ -4,7 +4,6 @@ import java.util.Comparator;
 import java.util.List;
 import java.util.Optional;
 import java.util.function.Predicate;
-import org.springframework.data.domain.Page;
 
 /**
  * ExtensionClient is an interface which contains some operations on Extension instead of
@@ -35,9 +34,9 @@ public interface ExtensionClient {
      * @param page is page number which starts from 0.
      * @param size is page size.
      * @param <E> is Extension type.
-     * @return a page of Extensions.
+     * @return a list of Extensions.
      */
-    <E extends Extension> Page<E> page(Class<E> type, Predicate<E> predicate,
+    <E extends Extension> ListResult<E> list(Class<E> type, Predicate<E> predicate,
         Comparator<E> comparator, int page, int size);
 
     /**

src/main/java/run/halo/app/extension/ExtensionRouterFunctionFactory.java

@@ -8,6 +8,8 @@ import io.swagger.v3.oas.annotations.enums.ParameterIn;
 import java.net.URI;
 import java.time.Instant;
 import java.util.Objects;
+import net.bytebuddy.ByteBuddy;
+import net.bytebuddy.description.type.TypeDescription;
 import org.springdoc.webflux.core.fn.SpringdocRouteBuilder;
 import org.springframework.http.MediaType;
 import org.springframework.lang.NonNull;
@@ -67,10 +69,9 @@ public class ExtensionRouterFunctionFactory {
                     .parameter(parameterBuilder().in(ParameterIn.QUERY)
                         .name("sort")
                         .description("Sort by some fields. Like metadata.name,desc"))
-
                     .response(responseBuilder().responseCode("200")
                         .description("Response " + scheme.plural())
-                        .implementationArray(scheme.type())))
+                        .implementation(generateListResultClass())))
             .POST(createHandler.pathPattern(), createHandler,
                 builder -> builder.operationId("Create" + gvk)
                     .description("Create " + gvk)
@@ -194,12 +195,18 @@ public class ExtensionRouterFunctionFactory {
         @Override
         @NonNull
         public Mono<ServerResponse> handle(@NonNull ServerRequest request) {
+            int page = request.queryParam("page")
+                .filter(StringUtils::hasLength)
+                .map(Integer::parseUnsignedInt).orElse(0);
+            int size = request.queryParam("size")
+                .filter(StringUtils::hasLength)
+                .map(Integer::parseUnsignedInt).orElse(0);
             // TODO Resolve predicate and comparator from request
-            var extensions = client.list(scheme.type(), null, null);
+            var listResult = client.list(scheme.type(), null, null, page, size);
             return ServerResponse
                 .ok()
                 .contentType(MediaType.APPLICATION_JSON)
-                .bodyValue(extensions);
+                .bodyValue(listResult);
         }
 
         @Override
@@ -315,4 +322,16 @@ public class ExtensionRouterFunctionFactory {
         }
 
     }
+
+    private Class<?> generateListResultClass() {
+        var generic =
+            TypeDescription.Generic.Builder.parameterizedType(ListResult.class, scheme.type())
+                .build();
+        return new ByteBuddy()
+            .subclass(generic)
+            .name(scheme.groupVersionKind().kind() + "List")
+            .make()
+            .load(this.getClass().getClassLoader())
+            .getLoaded();
+    }
 }

src/main/java/run/halo/app/extension/ListResult.java

@@ -0,0 +1,87 @@
+package run.halo.app.extension;
+
+import com.fasterxml.jackson.annotation.JsonIgnore;
+import com.fasterxml.jackson.annotation.JsonProperty;
+import io.swagger.v3.oas.annotations.media.Schema;
+import java.util.Collections;
+import java.util.Iterator;
+import java.util.List;
+import lombok.Data;
+import org.springframework.data.util.Streamable;
+import org.springframework.util.Assert;
+
+@Data
+public class ListResult<T> implements Streamable<T> {
+
+    @Schema(description = "Page number, starts from 1. If not set or equal to 0, it means no "
+        + "pagination.", required = true)
+    private final int page;
+
+    @Schema(description = "Size of each page. If not set or equal to 0, it means no pagination.",
+        required = true)
+    private final int size;
+
+    @Schema(description = "Total elements.", required = true)
+    private final long total;
+
+    @Schema(description = "A chunk of items.", required = true)
+    private final List<T> items;
+
+    public ListResult(int page, int size, long total, List<T> items) {
+        Assert.isTrue(total >= 0, "Total elements must be greater than or equal to 0");
+        if (page < 0) {
+            page = 0;
+        }
+        if (size < 0) {
+            size = 0;
+        }
+        if (items == null) {
+            items = Collections.emptyList();
+        }
+        this.page = page;
+        this.size = size;
+        this.total = total;
+        this.items = items;
+    }
+
+    public ListResult(List<T> items) {
+        this(0, 0, items.size(), items);
+    }
+
+    @Schema(description = "Indicates whether current page is the first page.", required = true)
+    public boolean isFirst() {
+        return !hasPrevious();
+    }
+
+    @Schema(description = "Indicates whether current page is the last page.", required = true)
+    public boolean isLast() {
+        return !hasNext();
+    }
+
+    @Schema(description = "Indicates whether current page has previous page.", required = true)
+    @JsonProperty("hasNext")
+    public boolean hasNext() {
+        if (page <= 0) {
+            return false;
+        }
+        var totalPages = size == 0 ? 1 : (int) Math.ceil((double) total / (double) size);
+        return page < totalPages;
+    }
+
+    @Schema(description = "Indicates whether current page has previous page.", required = true)
+    @JsonProperty("hasPrevious")
+    public boolean hasPrevious() {
+        return page > 1;
+    }
+
+    @Override
+    public Iterator<T> iterator() {
+        return items.iterator();
+    }
+
+    @Override
+    @JsonIgnore
+    public boolean isEmpty() {
+        return Streamable.super.isEmpty();
+    }
+}

src/test/java/run/halo/app/extension/DefaultExtensionClientTest.java

@@ -29,8 +29,6 @@ import org.junit.jupiter.api.extension.ExtendWith;
 import org.mockito.InjectMocks;
 import org.mockito.Mock;
 import org.mockito.junit.jupiter.MockitoExtension;
-import org.springframework.data.domain.PageImpl;
-import org.springframework.data.domain.PageRequest;
 import run.halo.app.extension.exception.SchemeNotFoundException;
 import run.halo.app.extension.store.ExtensionStore;
 import run.halo.app.extension.store.ExtensionStoreClient;
@@ -114,7 +112,7 @@ class DefaultExtensionClientTest {
         assertThrows(SchemeNotFoundException.class,
             () -> client.list(UnRegisteredExtension.class, null, null));
         assertThrows(SchemeNotFoundException.class,
-            () -> client.page(UnRegisteredExtension.class, null, null, 0, 10));
+            () -> client.list(UnRegisteredExtension.class, null, null, 0, 10));
         assertThrows(SchemeNotFoundException.class,
             () -> client.fetch(UnRegisteredExtension.class, "fake"));
         assertThrows(SchemeNotFoundException.class, () ->
@@ -192,23 +190,27 @@ class DefaultExtensionClientTest {
                 createExtensionStore("fake-03")));
 
         // without filter and sorter.
-        var fakes = client.page(FakeExtension.class, null, null, 0, 10);
+        var fakes = client.list(FakeExtension.class, null, null, 1, 10);
-        assertEquals(new PageImpl<>(List.of(fake1, fake2, fake3), PageRequest.of(0, 10), 3), fakes);
+        assertEquals(new ListResult<>(1, 10, 3, List.of(fake1, fake2, fake3)), fakes);
 
         // out of page range
-        fakes = client.page(FakeExtension.class, null, null, 100, 10);
+        fakes = client.list(FakeExtension.class, null, null, 100, 10);
-        assertEquals(new PageImpl<>(emptyList(), PageRequest.of(100, 10), 3), fakes);
+        assertEquals(new ListResult<>(100, 10, 3, emptyList()), fakes);
 
         // with filter only
         fakes =
-            client.page(FakeExtension.class, fake -> "fake-03".equals(fake.getMetadata().getName()),
+            client.list(FakeExtension.class, fake -> "fake-03".equals(fake.getMetadata().getName()),
-                null, 0, 10);
+                null, 1, 10);
-        assertEquals(new PageImpl<>(List.of(fake3), PageRequest.of(0, 10), 1), fakes);
+        assertEquals(new ListResult<>(1, 10, 1, List.of(fake3)), fakes);
 
         // with sorter only
-        fakes = client.page(FakeExtension.class, null,
+        fakes = client.list(FakeExtension.class, null,
-            reverseOrder(comparing(fake -> fake.getMetadata().getName())), 0, 10);
+            reverseOrder(comparing(fake -> fake.getMetadata().getName())), 1, 10);
-        assertEquals(new PageImpl<>(List.of(fake3, fake2, fake1), PageRequest.of(0, 10), 3), fakes);
+        assertEquals(new ListResult<>(1, 10, 3, List.of(fake3, fake2, fake1)), fakes);
+
+        // without page
+        fakes = client.list(FakeExtension.class, null, null, 0, 0);
+        assertEquals(new ListResult<>(0, 0, 3, List.of(fake1, fake2, fake3)), fakes);
     }
 
     @Test

src/test/java/run/halo/app/extension/ExtensionListHandlerTest.java

@@ -3,7 +3,8 @@ package run.halo.app.extension;
 import static org.junit.jupiter.api.Assertions.assertEquals;
 import static org.junit.jupiter.api.Assertions.assertTrue;
 import static org.mockito.ArgumentMatchers.any;
-import static org.mockito.ArgumentMatchers.eq;
+import static org.mockito.ArgumentMatchers.anyInt;
+import static org.mockito.ArgumentMatchers.same;
 import static org.mockito.Mockito.when;
 
 import java.util.List;
@@ -38,7 +39,10 @@ class ExtensionListHandlerTest {
         var listHandler = new ExtensionListHandler(scheme, client);
         var serverRequest = MockServerRequest.builder().build();
         final var fake = new FakeExtension();
-        when(client.list(eq(FakeExtension.class), any(), any())).thenReturn(List.of(fake));
+        // when(client.list(same(FakeExtension.class), any(), any())).thenReturn(List.of(fake));
+        var fakeListResult = new ListResult<>(0, 0, 1, List.of(fake));
+        when(client.list(same(FakeExtension.class), any(), any(), anyInt(), anyInt()))
+            .thenReturn(fakeListResult);
 
         var responseMono = listHandler.handle(serverRequest);
 
@@ -47,7 +51,7 @@ class ExtensionListHandlerTest {
                 assertEquals(HttpStatus.OK, response.statusCode());
                 assertEquals(MediaType.APPLICATION_JSON, response.headers().getContentType());
                 assertTrue(response instanceof EntityResponse<?>);
-                assertEquals(List.of(fake), ((EntityResponse<?>) response).entity());
+                assertEquals(fakeListResult, ((EntityResponse<?>) response).entity());
             })
             .verifyComplete();
     }