Use guava immutable collection

scm-webapp/src/main/java/sonia/scm/api/rest/resources/LinkBuilder.java

@@ -1,29 +1,43 @@
 package sonia.scm.api.rest.resources;
 
+import com.google.common.collect.ImmutableList;
+
 import javax.ws.rs.core.UriBuilder;
 import javax.ws.rs.core.UriInfo;
 import java.net.URI;
-import java.util.ArrayList;
 import java.util.Arrays;
-import java.util.Collections;
-import java.util.List;
 
+/**
+ * This class is used to create links for JAX-RS resources. Create a new instance specifying all resource classes used
+ * to process the request. Than for each of these classes call <code>builder.method(...).parameters(...)</code> for each
+ * of these classes consecutively. The builder itself is immutable, so that each instance is reusable and you get a new
+ * builder for each method.
+ *
+ * <pre>
+ * LinkBuilder builder = new LinkBuilder(uriInfo, MainResource.class, SubResource.class);
+ * Link link = builder
+ *     .method("sub")
+ *     .parameters("param")
+ *     .method("x")
+ *     .parameters("param_1", "param_2")
+ *     .create();
+ * </pre>
+ */
 class LinkBuilder {
   private final UriInfo uriInfo;
   private final Class[] classes;
-  private final List<Call> calls;
+  private final ImmutableList<Call> calls;
 
   LinkBuilder(UriInfo uriInfo, Class... classes) {
-    this(uriInfo, classes, Collections.emptyList());
+    this(uriInfo, classes, ImmutableList.of());
   }
 
-  private LinkBuilder(UriInfo uriInfo, Class[] classes, List<Call> calls) {
+  private LinkBuilder(UriInfo uriInfo, Class[] classes, ImmutableList<Call> calls) {
     this.uriInfo = uriInfo;
     this.classes = classes;
     this.calls = calls;
   }
 
-
   public Parameters method(String method) {
     if (calls.size() >= classes.length) {
       throw new IllegalStateException("no more classes for methods");
@@ -31,6 +45,44 @@ class LinkBuilder {
     return new Parameters(method);
   }
 
+  public Link create() {
+    if (calls.size() < classes.length) {
+      throw new IllegalStateException("not enough methods for all classes");
+    }
+
+    URI baseUri = uriInfo.getBaseUri();
+    URI relativeUri = createRelativeUri();
+    URI absoluteUri = baseUri.resolve(relativeUri);
+    return new Link(absoluteUri);
+  }
+
+  private LinkBuilder add(String method, String[] parameters) {
+    return new LinkBuilder(uriInfo, classes, appendNewCall(method, parameters));
+  }
+
+  private ImmutableList<Call> appendNewCall(String method, String[] parameters) {
+    return ImmutableList.<Call> builder().addAll(calls).add(createNewCall(method, parameters)).build();
+  }
+
+  private Call createNewCall(String method, String[] parameters) {
+    return new Call(LinkBuilder.this.classes[calls.size()], method, parameters);
+  }
+
+  private URI createRelativeUri() {
+    UriBuilder uriBuilder = userUriBuilder();
+    calls.forEach(call -> uriBuilder.path(call.clazz, call.method));
+    String[] concatenatedParameters = calls
+      .stream()
+      .map(call -> call.parameters)
+      .flatMap(Arrays::stream)
+      .toArray(String[]::new);
+    return uriBuilder.build((Object[]) concatenatedParameters);
+  }
+
+  private UriBuilder userUriBuilder() {
+    return UriBuilder.fromResource(classes[0]);
+  }
+
   class Parameters {
 
     private final String method;
@@ -44,41 +96,10 @@ class LinkBuilder {
     }
   }
 
-  private LinkBuilder add(String method, String[] parameters) {
-    List<Call> newCalls = new ArrayList<>(this.calls);
-    newCalls.add(new Call(LinkBuilder.this.classes[calls.size()], method, parameters));
-    return new LinkBuilder(uriInfo, classes, newCalls);
-  }
-
-  public Link create() {
-    if (calls.size() < classes.length) {
-      throw new IllegalStateException("not enough methods for all classes");
-    }
-
-    URI baseUri = uriInfo.getBaseUri();
-    URI relativeUri = createRelativeUri();
-    URI absoluteUri = baseUri.resolve(relativeUri);
-    return new Link(absoluteUri);
-  }
-
-  private URI createRelativeUri() {
-    UriBuilder uriBuilder = userUriBuilder();
-    calls.forEach(call -> uriBuilder.path(call.clazz, call.method));
-    String[] concatenatedParameters = calls
-      .stream()
-      .map(call -> call.parameters)
-      .flatMap(Arrays::stream)
-      .toArray(String[]::new);
-    return uriBuilder.build(concatenatedParameters);
-  }
-
-  private UriBuilder userUriBuilder() {
-    return UriBuilder.fromResource(classes[0]);
-  }
-
   private static class Call {
     private final Class clazz;
     private final String method;
+
     private final String[] parameters;
 
     private Call(Class clazz, String method, String[] parameters) {