OZG-7615 add documentation link

src/main/java/de/ozgcloud/admin/DocumentationProperties.java

+package de.ozgcloud.admin;
+
+import org.springframework.boot.context.properties.ConfigurationProperties;
+import org.springframework.context.annotation.Configuration;
+
+import lombok.Getter;
+import lombok.Setter;
+
+@Setter
+@Getter
+@Configuration
+@ConfigurationProperties(prefix = DocumentationProperties.DOCUMENTATION_PROPERTIES_PREFIX)
+public class DocumentationProperties {
+
+	static final String DOCUMENTATION_PROPERTIES_PREFIX = "ozgcloud.user-assistance.documentation";
+
+	private String url;
+
+}

src/main/java/de/ozgcloud/admin/RootModelAssembler.java

@@ -23,8 +23,7 @@
  */
 package de.ozgcloud.admin;
 
-import java.util.ArrayList;
-import java.util.List;
+import java.util.Objects;
 
 import org.springframework.boot.autoconfigure.data.rest.RepositoryRestProperties;
 import org.springframework.hateoas.EntityModel;
@@ -40,24 +39,19 @@ import lombok.RequiredArgsConstructor;
 @RequiredArgsConstructor
 public class RootModelAssembler implements RepresentationModelAssembler<Root, EntityModel<Root>> {
 	static final String REL_CONFIGURATION = "configuration";
+	static final String REL_DOCUMENTATIONS = "documentations";
 
 	private final RepositoryRestProperties restProperties;
 	private final CurrentUserService currentUserService;
+	private final DocumentationProperties documentationProperties;
 
 	@Override
 	public EntityModel<Root> toModel(Root root) {
-		List<Link> links = buildRootModelLinks();
-		return EntityModel.of(root, links);
-	}
-
-	List<Link> buildRootModelLinks() {
-		List<Link> links = new ArrayList<>();
-		var rootLinkBuilder = WebMvcLinkBuilder.linkTo(RootController.class);
-		links.add(rootLinkBuilder.withSelfRel());
-		if (currentUserService.hasConfigurationPermission()) {
-			links.add(buildConfigLink());
-		}
-		return links;
+		var rootModel = EntityModel.of(root);
+		rootModel.add(WebMvcLinkBuilder.linkTo(RootController.class).withSelfRel());
+		rootModel.addIf(currentUserService.hasConfigurationPermission(), this::buildConfigLink);
+		rootModel.addIf(Objects.nonNull(documentationProperties.getUrl()), () -> Link.of(documentationProperties.getUrl(), REL_DOCUMENTATIONS));
+		return rootModel;
 	}
 
 	private Link buildConfigLink() {

src/test/java/de/ozgcloud/admin/RootModelAssemblerTest.java

@@ -27,8 +27,6 @@ import static de.ozgcloud.admin.RootModelAssembler.*;
 import static org.assertj.core.api.Assertions.*;
 import static org.mockito.Mockito.*;
 
-import java.util.List;
-
 import org.junit.jupiter.api.BeforeEach;
 import org.junit.jupiter.api.DisplayName;
 import org.junit.jupiter.api.Nested;
@@ -37,8 +35,11 @@ import org.mockito.InjectMocks;
 import org.mockito.Mock;
 import org.mockito.Spy;
 import org.springframework.boot.autoconfigure.data.rest.RepositoryRestProperties;
+import org.springframework.hateoas.IanaLinkRelations;
 import org.springframework.hateoas.Link;
 
+import com.thedeanda.lorem.LoremIpsum;
+
 import de.ozgcloud.admin.common.user.CurrentUserService;
 
 class RootModelAssemblerTest {
@@ -53,42 +54,35 @@ class RootModelAssemblerTest {
 	private RepositoryRestProperties restProperties;
 	@Mock
 	private CurrentUserService currentUserService;
+	@Mock
+	private DocumentationProperties documentationProperties;
 
 	@DisplayName("Entity Model")
 	@Nested
-	class TestEntityModel {
+	class TestToModel {
 
-		private final List<Link> links = List.of(Link.of(RootController.PATH));
-
-		@BeforeEach
-		void beforeEach() {
-			doReturn(links).when(modelAssembler).buildRootModelLinks();
-		}
+		private final Root root = RootTestFactory.create();
 
 		@Test
-		void shouldHaveRoot() {
-			var givenRoot = RootTestFactory.create();
-
-			var resultRoot = modelAssembler.toModel(givenRoot).getContent();
+		void shouldHaveRootContent() {
+			var resultRoot = modelAssembler.toModel(root).getContent();
 
-			assertThat(resultRoot).isEqualTo(givenRoot);
+			assertThat(resultRoot).isEqualTo(root);
 		}
 
 		@Test
-		void shouldHaveLinks() {
-			var modelLinks = modelAssembler.toModel(RootTestFactory.create()).getLinks();
+		void shouldHaveSelfLink() {
+			var model = modelAssembler.toModel(root);
 
-			assertThat(modelLinks).containsAll(links);
-		}
+			assertThat(model.getLink(IanaLinkRelations.SELF)).get().extracting(Link::getHref).isEqualTo(RootController.PATH);
 		}
 
-	@DisplayName("Root Model Links")
 		@Nested
-	class TestBuildRootModelLinks {
+		class TestConfigurationLink {
 
 			@Test
-		void shouldCheckConfigurationPermission() {
-			modelAssembler.buildRootModelLinks();
+			void shouldCallHasConfigurationPermission() {
+				modelAssembler.toModel(root);
 
 				verify(currentUserService).hasConfigurationPermission();
 			}
@@ -104,16 +98,14 @@ class RootModelAssemblerTest {
 
 				@Test
 				void shouldHaveHrefToConfiguration() {
-				var links = modelAssembler.buildRootModelLinks();
+					var model = modelAssembler.toModel(root);
 
-				assertThat(links).containsExactly(
-						Link.of(RootController.PATH),
-						Link.of(BASE_PATH, REL_CONFIGURATION));
+					assertThat(model.getLink(REL_CONFIGURATION)).get().extracting(Link::getHref).isEqualTo(BASE_PATH);
 				}
 			}
 
 			@Nested
-		class TestOnNotHasConfigurationPermission {
+			class TestOnHasNotConfigurationPermission {
 
 				@BeforeEach
 				void hasNotConfigurationPermission() {
@@ -121,14 +113,57 @@ class RootModelAssemblerTest {
 				}
 
 				@Test
-			void shouldHaveOnlySelfLink() {
-				var links = modelAssembler.buildRootModelLinks();
+				void shouldNotHaveConfigurationLink() {
+					var model = modelAssembler.toModel(root);
 
-				assertThat(links).containsExactly(
-						Link.of(RootController.PATH));
+					assertThat(model.getLink(REL_CONFIGURATION)).isEmpty();
+				}
 			}
 		}
 
+		@Nested
+		class TestDocumentationLink {
+
+			@Test
+			void shouldGetDocumentationUrl() {
+				modelAssembler.toModel(root);
+
+				verify(documentationProperties).getUrl();
 			}
 
+			@Nested
+			class TestOnDocumentationUrlGiven {
+
+				private final String documentationUrl = LoremIpsum.getInstance().getUrl();
+
+				@BeforeEach
+				void mock() {
+					when(documentationProperties.getUrl()).thenReturn(documentationUrl);
+				}
+
+				@Test
+				void shouldHaveDocumentationLink() {
+					var model = modelAssembler.toModel(root);
+
+					assertThat(model.getLink(REL_DOCUMENTATIONS)).get().extracting(Link::getHref).isEqualTo(documentationUrl);
+				}
+			}
+
+			@Nested
+			class TestOnDocumentationUrlNotGiven {
+
+				@BeforeEach
+				void mock() {
+					when(documentationProperties.getUrl()).thenReturn(null);
+				}
+
+				@Test
+				void shouldNotHaveDocumentationLink() {
+					var model = modelAssembler.toModel(root);
+
+					assertThat(model.getLink(REL_DOCUMENTATIONS)).isEmpty();
+				}
+			}
+		}
+	}
 }
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