Add ability to read resource state events for Issues

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

@@ -85,6 +85,7 @@ public String getApiNamespace() {
     private RepositoryApi repositoryApi;
     private RepositoryFileApi repositoryFileApi;
     private ResourceLabelEventsApi resourceLabelEventsApi;
+    private ResourceStateEventsApi resourceStateEventsApi;
     private RunnersApi runnersApi;
     private SearchApi searchApi;
     private ServicesApi servicesApi;
@@ -1488,6 +1489,25 @@ public ResourceLabelEventsApi getResourceLabelEventsApi() {
         return (resourceLabelEventsApi);
     }
 
+    /**
+     * Gets the ResourceStateEventsApi instance owned by this GitLabApi instance. The ResourceStateEventsApi
+     * is used to perform all Resource State Events related API calls.
+     *
+     * @return the ResourceStateEventsApi instance owned by this GitLabApi instance
+     */
+    public ResourceStateEventsApi getResourceStateEventsApi() {
+
+        if (resourceStateEventsApi == null) {
+            synchronized (this) {
+                if (resourceStateEventsApi == null) {
+                    resourceStateEventsApi = new ResourceStateEventsApi(this);
+                }
+            }
+        }
+
+        return (resourceStateEventsApi);
+    }
+
     /**
      * Gets the RunnersApi instance owned by this GitLabApi instance. The RunnersApi is used
      * to perform all Runner related API calls.

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

@@ -0,0 +1,65 @@
+package org.gitlab4j.api;
+
+import org.gitlab4j.api.models.IssueEvent;
+import org.gitlab4j.api.models.LabelEvent;
+
+import javax.ws.rs.core.Response;
+import java.util.List;
+import java.util.Optional;
+import java.util.stream.Stream;
+
+
+/**
+ * This class provides an entry point to all the GitLab Resource state events API
+ * @see <a href="https://docs.gitlab.com/ce/api/resource_state_events.html">Resource state events API at GitLab</a>
+ */
+public class ResourceStateEventsApi extends AbstractApi {
+
+    public ResourceStateEventsApi(GitLabApi gitLabApi) {
+        super(gitLabApi);
+    }
+
+    /**
+     * Gets a list of all state events for a single issue.
+     *
+     * <pre><code>GitLab Endpoint: GET /projects/:id/issues/:issue_iid/resource_state_events</code></pre>
+     *
+     * @param projectIdOrPath id, path of the project, or a Project instance holding the project ID or path
+     * @param issueIid the IID of the issue
+     * @return a List of IssueEvent for the specified issue
+     * @throws GitLabApiException if any exception occurs
+     */
+    public List<IssueEvent> getIssueStateEvents(Object projectIdOrPath, Integer issueIid) throws GitLabApiException {
+        return (getIssueStateEvents(projectIdOrPath, issueIid, getDefaultPerPage()).all());
+    }
+
+    /**
+     * Gets a Pager of all state events for a single issue.
+     *
+     * <pre><code>GitLab Endpoint: GET /projects/:id/issues/:issue_iid/resource_state_events</code></pre>
+     *
+     * @param projectIdOrPath id, path of the project, or a Project instance holding the project ID or path
+     * @param issueIid the IID of the issue
+     * @param itemsPerPage the number of LabelEvent instances that will be fetched per page
+     * @return the Pager of IssueEvent instances for the specified issue IID
+     * @throws GitLabApiException if any exception occurs
+     */
+    public Pager<IssueEvent> getIssueStateEvents(Object projectIdOrPath, Integer issueIid, int itemsPerPage) throws GitLabApiException {
+        return (new Pager<IssueEvent>(this, IssueEvent.class, itemsPerPage, null,
+            "projects", getProjectIdOrPath(projectIdOrPath), "issues", issueIid, "resource_state_events"));
+    }
+
+    /**
+     * Gets a Stream of all state events for a single issue.
+     *
+     * <pre><code>GitLab Endpoint: GET /projects/:id/issues/:issue_iid/resource_state_events</code></pre>
+     *
+     * @param projectIdOrPath id, path of the project, or a Project instance holding the project ID or path
+     * @param issueIid the IID of the issue
+     * @return a Stream of IssueEvent for the specified issue
+     * @throws GitLabApiException if any exception occurs
+     */
+    public Stream<IssueEvent> getIssueStateEventsStream(Object projectIdOrPath, Integer issueIid) throws GitLabApiException {
+        return (getIssueStateEvents(projectIdOrPath, issueIid, getDefaultPerPage()).stream());
+    }
+}

src/main/java/org/gitlab4j/api/models/IssueEvent.java

@@ -0,0 +1,93 @@
+package org.gitlab4j.api.models;
+
+import com.fasterxml.jackson.annotation.JsonCreator;
+import com.fasterxml.jackson.annotation.JsonValue;
+import org.gitlab4j.api.utils.JacksonJson;
+import org.gitlab4j.api.utils.JacksonJsonEnumHelper;
+
+public class IssueEvent {
+    /** Enum to use for specifying the state events resource type. */
+    public enum ResourceType {
+
+	ISSUE;
+
+	private static JacksonJsonEnumHelper<ResourceType> enumHelper = new JacksonJsonEnumHelper<>(ResourceType.class,
+	        true, true);
+
+	@JsonCreator
+	public static ResourceType forValue(String value) {
+	    return enumHelper.forValue(value);
+	}
+
+	@JsonValue
+	public String toValue() {
+	    return (enumHelper.toString(this));
+	}
+
+	@Override
+	public String toString() {
+	    return (enumHelper.toString(this));
+	}
+    }
+
+    private int id;
+    private User user;
+    private String createdAt;
+    private ResourceType resourceType;
+    private int resourceId;
+    private String state;
+
+    public int getId() {
+	return id;
+    }
+
+    public void setId(int id) {
+	this.id = id;
+    }
+
+    public User getUser() {
+	return user;
+    }
+
+    public void setUser(User user) {
+	this.user = user;
+    }
+
+    public String getCreatedAt() {
+	return createdAt;
+    }
+
+    public void setCreatedAt(String createdAt) {
+	this.createdAt = createdAt;
+    }
+
+    public ResourceType getResourceType() {
+	return resourceType;
+    }
+
+    public void setResourceType(ResourceType resourceType) {
+	this.resourceType = resourceType;
+    }
+
+    public int getResourceId() {
+	return resourceId;
+    }
+
+    public void setResourceId(int resourceId) {
+	this.resourceId = resourceId;
+    }
+
+    public String getState() {
+        return state;
+    }
+
+    public void setState(String state) {
+        this.state = state;
+    }
+
+
+    @Override
+    public String toString() {
+        return (JacksonJson.toJsonString(this));
+    }
+}

src/test/java/org/gitlab4j/api/TestIssuesApi.java

@@ -101,7 +101,7 @@ public static void teardown() throws GitLabApiException {
         deleteAllTestIssues();
     }
 
-    private static void deleteAllTestIssues() {
+    public static void deleteAllTestIssues() {
 
         if (gitLabApi != null) {
             try {

src/test/java/org/gitlab4j/api/TestResourceStateEventsApi.java

@@ -0,0 +1,76 @@
+package org.gitlab4j.api;
+
+import org.gitlab4j.api.models.Issue;
+import org.gitlab4j.api.models.IssueEvent;
+import org.gitlab4j.api.models.Project;
+import org.junit.AfterClass;
+import org.junit.BeforeClass;
+import org.junit.Test;
+import org.junit.experimental.categories.Category;
+
+import java.util.List;
+
+import static org.gitlab4j.api.TestIssuesApi.deleteAllTestIssues;
+import static org.junit.Assert.*;
+
+@Category(IntegrationTest.class)
+public class TestResourceStateEventsApi extends AbstractIntegrationTest {
+
+    private static GitLabApi gitLabApi;
+    private static Project testProject;
+
+    private static final String ISSUE_TITLE = "Test Issue Title";
+    private static final String ISSUE_DESCRIPTION = "This is a really nice description, not.";
+
+    public TestResourceStateEventsApi() {
+        super();
+    }
+
+    @BeforeClass
+    public static void setup() {
+        gitLabApi = baseTestSetup();
+        testProject = getTestProject();
+    }
+
+    @AfterClass
+    public static void teardown() {
+        deleteAllTestIssues();
+    }
+
+    @Test
+    public void testGetCloseReopenIssueEvents() throws GitLabApiException {
+        Integer projectId = testProject.getId();
+        Issue issue = gitLabApi.getIssuesApi().createIssue(projectId, ISSUE_TITLE, ISSUE_DESCRIPTION);
+
+        Issue closedIssue = gitLabApi.getIssuesApi().closeIssue(projectId, issue.getIid());
+        assertEquals(closedIssue.getState(), Constants.IssueState.CLOSED);
+
+        List<IssueEvent> issueEvents = gitLabApi.getResourceStateEventsApi().getIssueStateEvents(projectId, issue.getIid());
+        assertNotNull(issueEvents);
+        assertEquals(1, issueEvents.size());
+
+        assertEquals(1, issueEvents.stream()
+            .filter(issueEvent -> issueEvent.getState().equals(Constants.IssueState.CLOSED.toValue()))
+            .count());
+
+        Issue reopenedIssue = gitLabApi.getIssuesApi()
+            .updateIssue(projectId,
+                issue.getIid(),
+                null, null, null, null, null, null,
+                Constants.StateEvent.REOPEN,
+                null, null);
+        assertEquals(Constants.IssueState.OPENED.toValue(), reopenedIssue.getState().toValue());
+
+        issueEvents = gitLabApi.getResourceStateEventsApi().getIssueStateEvents(projectId, issue.getIid());
+        assertNotNull(issueEvents);
+        assertEquals(2, issueEvents.size());
+
+        assertEquals(1, issueEvents.stream()
+            .filter(issueEvent -> issueEvent.getState().equals(Constants.IssueState.CLOSED.toValue()))
+            .count());
+        assertEquals(1, issueEvents.stream()
+            .filter(issueEvent -> issueEvent.getState().equals(Constants.IssueState.REOPENED.toValue()))
+            .count());
+    }
+
+}