added new api to simplify the process of appending links to json responses

scm-core/src/test/java/sonia/scm/api/v2/resources/LinkAppenderMapperTest.java

@@ -0,0 +1,74 @@
+package sonia.scm.api.v2.resources;
+
+import org.junit.jupiter.api.BeforeEach;
+import org.junit.jupiter.api.Test;
+import org.junit.jupiter.api.extension.ExtendWith;
+import org.mockito.Mock;
+import org.mockito.junit.jupiter.MockitoExtension;
+
+import java.util.Optional;
+
+import static org.mockito.Mockito.verify;
+
+@ExtendWith(MockitoExtension.class)
+class LinkAppenderMapperTest {
+
+  @Mock
+  private LinkAppender appender;
+
+  private LinkEnricherRegistry registry;
+  private LinkAppenderMapper mapper;
+
+  @BeforeEach
+  void beforeEach() {
+    registry = new LinkEnricherRegistry();
+    mapper = new LinkAppenderMapper();
+    mapper.setRegistry(registry);
+  }
+
+  @Test
+  void shouldAppendSimpleLink() {
+    registry.register(String.class, (ctx, appender) -> appender.appendOne("42", "https://hitchhiker.com"));
+
+    mapper.appendLinks(appender, "hello");
+
+    verify(appender).appendOne("42", "https://hitchhiker.com");
+  }
+
+  @Test
+  void shouldCallMultipleEnrichers() {
+    registry.register(String.class, (ctx, appender) -> appender.appendOne("42", "https://hitchhiker.com"));
+    registry.register(String.class, (ctx, appender) -> appender.appendOne("21", "https://scm.hitchhiker.com"));
+
+    mapper.appendLinks(appender, "hello");
+
+    verify(appender).appendOne("42", "https://hitchhiker.com");
+    verify(appender).appendOne("21", "https://scm.hitchhiker.com");
+  }
+
+  @Test
+  void shouldAppendLinkByUsingSourceFromContext() {
+    registry.register(String.class, (ctx, appender) -> {
+      Optional<String> rel = ctx.oneByType(String.class);
+      appender.appendOne(rel.get(), "https://hitchhiker.com");
+    });
+
+    mapper.appendLinks(appender, "42");
+
+    verify(appender).appendOne("42", "https://hitchhiker.com");
+  }
+
+  @Test
+  void shouldAppendLinkByUsingMultipleContextEntries() {
+    registry.register(Integer.class, (ctx, appender) -> {
+      Optional<Integer> rel = ctx.oneByType(Integer.class);
+      Optional<String> href = ctx.oneByType(String.class);
+      appender.appendOne(String.valueOf(rel.get()), href.get());
+    });
+
+    mapper.appendLinks(appender, Integer.valueOf(42), "https://hitchhiker.com");
+
+    verify(appender).appendOne("42", "https://hitchhiker.com");
+  }
+
+}

scm-core/src/test/java/sonia/scm/api/v2/resources/LinkEnricherContextTest.java

@@ -0,0 +1,44 @@
+package sonia.scm.api.v2.resources;
+
+import static org.assertj.core.api.Assertions.assertThat;
+import static org.junit.jupiter.api.Assertions.assertThrows;
+
+import org.junit.jupiter.api.Test;
+
+import java.util.NoSuchElementException;
+
+class LinkEnricherContextTest {
+
+  @Test
+  void shouldCreateContextFromSingleObject() {
+    LinkEnricherContext context = LinkEnricherContext.of("hello");
+    assertThat(context.oneByType(String.class)).contains("hello");
+  }
+
+  @Test
+  void shouldCreateContextFromMultipleObjects() {
+    LinkEnricherContext context = LinkEnricherContext.of("hello", Integer.valueOf(42), Long.valueOf(21L));
+    assertThat(context.oneByType(String.class)).contains("hello");
+    assertThat(context.oneByType(Integer.class)).contains(42);
+    assertThat(context.oneByType(Long.class)).contains(21L);
+  }
+
+  @Test
+  void shouldReturnEmptyOptionalForUnknownTypes() {
+    LinkEnricherContext context = LinkEnricherContext.of();
+    assertThat(context.oneByType(String.class)).isNotPresent();
+  }
+
+  @Test
+  void shouldReturnRequiredObject() {
+    LinkEnricherContext context = LinkEnricherContext.of("hello");
+    assertThat(context.oneRequireByType(String.class)).isEqualTo("hello");
+  }
+
+  @Test
+  void shouldThrowAnNoSuchElementExceptionForUnknownTypes() {
+    LinkEnricherContext context = LinkEnricherContext.of();
+    assertThrows(NoSuchElementException.class, () -> context.oneRequireByType(String.class));
+  }
+
+}

scm-core/src/test/java/sonia/scm/api/v2/resources/LinkEnricherRegistryTest.java

@@ -0,0 +1,60 @@
+package sonia.scm.api.v2.resources;
+
+import org.junit.jupiter.api.BeforeEach;
+import org.junit.jupiter.api.Test;
+
+import static org.assertj.core.api.Assertions.assertThat;
+
+class LinkEnricherRegistryTest {
+
+  private LinkEnricherRegistry registry;
+
+  @BeforeEach
+  void setUpObjectUnderTest() {
+    registry = new LinkEnricherRegistry();
+  }
+
+  @Test
+  void shouldRegisterTheEnricher() {
+    SampleLinkEnricher enricher = new SampleLinkEnricher();
+    registry.register(String.class, enricher);
+
+    Iterable<LinkEnricher> enrichers = registry.allByType(String.class);
+    assertThat(enrichers).containsOnly(enricher);
+  }
+
+  @Test
+  void shouldRegisterMultipleEnrichers() {
+    SampleLinkEnricher one = new SampleLinkEnricher();
+    registry.register(String.class, one);
+
+    SampleLinkEnricher two = new SampleLinkEnricher();
+    registry.register(String.class, two);
+
+    Iterable<LinkEnricher> enrichers = registry.allByType(String.class);
+    assertThat(enrichers).containsOnly(one, two);
+  }
+
+  @Test
+  void shouldRegisterEnrichersForDifferentTypes() {
+    SampleLinkEnricher one = new SampleLinkEnricher();
+    registry.register(String.class, one);
+
+    SampleLinkEnricher two = new SampleLinkEnricher();
+    registry.register(Integer.class, two);
+
+    Iterable<LinkEnricher> enrichers = registry.allByType(String.class);
+    assertThat(enrichers).containsOnly(one);
+
+    enrichers = registry.allByType(Integer.class);
+    assertThat(enrichers).containsOnly(two);
+  }
+
+  private static class SampleLinkEnricher implements LinkEnricher {
+    @Override
+    public void enrich(LinkEnricherContext context, LinkAppender appender) {
+
+    }
+  }
+
+}