lazy streams with pagersplitter (#295)

Author: mariuszs

src/main/java/org/gitlab4j/api/Pager.java

@@ -7,6 +7,7 @@
 import java.util.List;
 import java.util.NoSuchElementException;
 import java.util.stream.Stream;
+import java.util.stream.StreamSupport;
 
 import javax.ws.rs.core.MultivaluedMap;
 import javax.ws.rs.core.Response;
@@ -333,4 +334,12 @@ public Stream<T> stream() throws GitLabApiException {
 
     	return (streamBuilder.build());
     }
+
+    public Stream<T> lazyStream() {
+        // Make sure that current page is 0, this will ensure the whole list is streamed
+        // regardless of what page the instance is currently on.
+        currentPage = 0;
+
+        return StreamSupport.stream(new PagerSpliterator<T>(this), false);
+    }
 }

src/main/java/org/gitlab4j/api/PagerSpliterator.java

@@ -0,0 +1,47 @@
+package org.gitlab4j.api;
+
+import java.util.Iterator;
+import java.util.Spliterator;
+import java.util.function.Consumer;
+
+class PagerSpliterator<T> implements Spliterator<T> {
+
+	private Pager<T> pager;
+
+	private Iterator<T> elements;
+
+	PagerSpliterator(Pager<T> pager) {
+		this.pager = pager;
+		if (pager.hasNext()) {
+			elements = this.pager.next().iterator();
+		}
+	}
+
+	@Override
+	public boolean tryAdvance(Consumer<? super T> action) {
+		if (elements.hasNext()) {
+			action.accept(elements.next());
+			return true;
+		} else if (pager.hasNext()) {
+			elements = pager.next().iterator();
+			action.accept(elements.next());
+			return true;
+		}
+		return false;
+	}
+
+	@Override
+	public Spliterator<T> trySplit() {
+		return null;
+	}
+
+	@Override
+	public long estimateSize() {
+		return pager.getTotalItems();
+	}
+
+	@Override
+	public int characteristics() {
+		return 0;
+	}
+}

src/main/java/org/gitlab4j/api/ProjectApi.java

@@ -818,15 +818,15 @@ public Project createProject(Project project, String importUrl) throws GitLabApi
         if (isApiVersion(ApiVersion.V3)) {
             boolean isPublic = (project.getPublic() != null ? project.getPublic() : project.getVisibility() == Visibility.PUBLIC);
             formData.withParam("public", isPublic);
-            
+
             if (project.getTagList() != null && !project.getTagList().isEmpty()) {
                 throw new IllegalArgumentException("GitLab API v3 does not support tag lists when creating projects");
             }
         } else {
             Visibility visibility = (project.getVisibility() != null ? project.getVisibility() :
                 project.getPublic() == Boolean.TRUE ? Visibility.PUBLIC : null);
             formData.withParam("visibility", visibility);
-            
+
             if (project.getTagList() != null && !project.getTagList().isEmpty()) {
                 formData.withParam("tag_list", String.join(",", project.getTagList()));
             }
@@ -1057,15 +1057,15 @@ public Project updateProject(Project project) throws GitLabApiException {
             formData.withParam("visibility_level", project.getVisibilityLevel());
             boolean isPublic = (project.getPublic() != null ? project.getPublic() : project.getVisibility() == Visibility.PUBLIC);
             formData.withParam("public", isPublic);
-            
+
             if (project.getTagList() != null && !project.getTagList().isEmpty()) {
                 throw new IllegalArgumentException("GitLab API v3 does not support tag lists when updating projects");
             }
         } else {
             Visibility visibility = (project.getVisibility() != null ? project.getVisibility() :
                 project.getPublic() == Boolean.TRUE ? Visibility.PUBLIC : null);
             formData.withParam("visibility", visibility);
-            
+
             if (project.getTagList() != null && !project.getTagList().isEmpty()) {
                 formData.withParam("tag_list", String.join(",", project.getTagList()));
             }
@@ -1090,7 +1090,7 @@ public void deleteProject(Object projectIdOrPath) throws GitLabApiException {
 
     /**
      * Forks a project into the user namespace of the authenticated user or the one provided.
-     * The forking operation for a project is asynchronous and is completed in a background job. 
+     * The forking operation for a project is asynchronous and is completed in a background job.
      * The request will return immediately.
      *
      * <pre><code>POST /projects/:id/fork</code></pre>
@@ -1109,7 +1109,7 @@ public Project forkProject(Object projectIdOrPath, String namespace) throws GitL
 
     /**
      * Forks a project into the user namespace of the authenticated user or the one provided.
-     * The forking operation for a project is asynchronous and is completed in a background job. 
+     * The forking operation for a project is asynchronous and is completed in a background job.
      * The request will return immediately.
      *
      * <pre><code>POST /projects/:id/fork</code></pre>
@@ -1130,7 +1130,7 @@ public Project forkProject(Object projectIdOrPath, Integer namespaceId) throws G
      * Create a forked from/to relation between existing projects.
      *
      * <pre><code>POST /projects/:id/fork/:forkFromId</code></pre>
-     * 
+     *
      *
      * @param projectIdOrPath projectIdOrPath the project in the form of an Integer(ID), String(path), or Project instance
      * @param forkedFromId the ID of the project that was forked from
@@ -1455,7 +1455,7 @@ public List<ProjectUser> getProjectUsers(Object projectIdOrPath, String search)
     }
 
     /**
-     * Get a Pager of project users matching the specified search string. This Pager includes 
+     * Get a Pager of project users matching the specified search string. This Pager includes
      * all project members and all users assigned to project parent groups.
      *
      * <pre><code>GET /projects/:id/users</code></pre>
@@ -1644,7 +1644,7 @@ public Optional<ProjectHook> getOptionalHook(Object projectIdOrPath, Integer hoo
      * @return the added ProjectHook instance
      * @throws GitLabApiException if any exception occurs
      */
-    public ProjectHook addHook(String projectName, String url, ProjectHook enabledHooks, boolean enableSslVerification, String secretToken) 
+    public ProjectHook addHook(String projectName, String url, ProjectHook enabledHooks, boolean enableSslVerification, String secretToken)
             throws GitLabApiException {
 
         if (projectName == null) {
@@ -2266,9 +2266,9 @@ public void deletePushRules(Object projectIdOrPath) throws GitLabApiException {
 
     /**
      * Get a list of projects that were forked from the specified project.
-     * 
+     *
      * <pre><code>GET /projects/:id/forks</code></pre>
-     * 
+     *
      * @param projectIdOrPath projectIdOrPath the project in the form of an Integer(ID), String(path), or Project instance, required
      * @return a List of forked projects
      * @throws GitLabApiException if any exception occurs
@@ -2382,7 +2382,7 @@ public Project transferProject(Object projectIdOrPath, String namespace) throws
     }
 
     /**
-     * Uploads and sets the project avatar for the specified project. 
+     * Uploads and sets the project avatar for the specified project.
      *
      * <pre><code>PUT /projects/:id/uploads</code></pre>
      *