Add footer with current Update Level

src/main/java/io/jenkins/plugins/evergreen/EvergreenUpdateLevelPageDecorator.java

@@ -0,0 +1,48 @@
+package io.jenkins.plugins.evergreen;
+
+import com.google.common.annotations.VisibleForTesting;
+import hudson.Extension;
+import hudson.model.PageDecorator;
+import net.sf.json.JSONException;
+import net.sf.json.JSONObject;
+import net.sf.json.groovy.JsonSlurper;
+
+import java.io.File;
+import java.io.IOException;
+import java.util.logging.Logger;
+
+
+@Extension
+public class EvergreenUpdateLevelPageDecorator extends PageDecorator {
+
+    private static final Logger LOGGER = Logger.getLogger(EvergreenUpdateLevelPageDecorator.class.getName());
+    private File manifest;
+
+    @VisibleForTesting
+    EvergreenUpdateLevelPageDecorator(File manifestFilePath) {
+        this.manifest = manifestFilePath;
+    }
+
+    public EvergreenUpdateLevelPageDecorator() {
+        final String evergreenData = System.getenv("EVERGREEN_DATA");
+        manifest = new File(evergreenData, "updates.json");
+    }
+
+    public String getUpdateLevel() {
+        String updateLevel = "N/A";
+
+        if (manifest.exists()) {
+            try {
+                final JSONObject parsedJson = (JSONObject) new JsonSlurper().parse(manifest);
+                updateLevel = "" + ((JSONObject) parsedJson.get("meta")).get("level");
+            } catch (IOException e) {
+                updateLevel = "Unable to parse: " + e.getMessage();
+            } catch (JSONException e) {
+                updateLevel = "Corrupted manifest: " + e.getMessage();
+            }
+        } else {
+            LOGGER.warning("No Evergreen manifest found!");
+        }
+        return updateLevel;
+    }
+}

src/main/resources/io/jenkins/plugins/evergreen/EvergreenUpdateLevelPageDecorator/footer.jelly

@@ -0,0 +1,4 @@
+<?jelly escape-by-default='true'?>
+<j:jelly xmlns:j="jelly:core">
+  <span class="updateLevel"><a href="https://evergreen.jenkins.io/">Evergreen <em><acronym title="Update Level">UL</acronym>-<j:out value="${it.getUpdateLevel()}"/></em></a></span>
+</j:jelly>

src/test/java/io/jenkins/plugins/evergreen/EvergreenUpdateLevelPageDecoratorTest.java

@@ -0,0 +1,17 @@
+package io.jenkins.plugins.evergreen;
+
+import org.junit.Test;
+
+import java.io.File;
+
+import static org.assertj.core.api.Assertions.assertThat;
+
+public class EvergreenUpdateLevelPageDecoratorTest {
+    @Test
+    public void getUpdateLevel() {
+
+        final File manifestFile = new File(getClass().getResource("manifest.json").getPath());
+        assertThat(manifestFile).exists();
+        assertThat(new EvergreenUpdateLevelPageDecorator(manifestFile).getUpdateLevel()).isEqualTo("2");
+    }
+}