Merge pull request #32 from N4rm0/initial-index-yaml-for-hosted

Create initial index.yaml file for hosted repository

verified index.yml is created when requested by add repos to helm client config. e.g.
```
helm repo add helm-proxy http://localhost:8081/repository/helm-proxy/
helm repo add helm-hosted http://localhost:8081/repository/helm-hosted/
```
both work fine (no 404 errors), and afterwards, an empty `index.yml` exists for both proxy and hosted repos.

Also verified using helm client to install a chart triggers a fetch of a fully populated 'index.yml' from the remote, and the helm client install succeeds.

Nicely done @N4rm0 ! Thanks for the contribution!

(Not sure if this fixes #20, as that one might be a 'sub-directory' issue)

Fixes #23, #26

src/main/java/org/sonatype/repository/helm/internal/createindex/CreateIndexFacetImpl.java

@@ -23,6 +23,7 @@
 import org.sonatype.nexus.common.stateguard.Guarded;
 import org.sonatype.nexus.repository.FacetSupport;
 import org.sonatype.nexus.repository.Repository;
+import org.sonatype.nexus.repository.manager.RepositoryCreatedEvent;
 import org.sonatype.nexus.repository.storage.Asset;
 import org.sonatype.nexus.repository.storage.AssetCreatedEvent;
 import org.sonatype.nexus.repository.storage.AssetDeletedEvent;
@@ -107,6 +108,15 @@ public void on(final AssetUpdatedEvent updated) {
     maybeInvalidateIndex(updated);
   }
 
+  @Subscribe
+  @Guarded(by = STARTED)
+  @AllowConcurrentEvents
+  public void on(RepositoryCreatedEvent createdEvent) {
+    // at repository creation time, create index.yaml with empty entries
+    log.debug("Initializing index.yaml for hosted repository {}", getRepository().getName());
+    invalidateIndex();
+  }
+
   private void maybeInvalidateIndex(final AssetEvent event) {
      if(matchesRepository(event) && isEventRelevant(event)) {
        invalidateIndex();

src/main/java/org/sonatype/repository/helm/internal/createindex/CreateIndexServiceImpl.java

@@ -85,14 +85,9 @@ public TempBlob buildIndexYaml(final Repository repository) {
       parseAssetIntoChartEntry(index, asset);
     }
 
-    if (index.getEntries().size() == 0) {
-      return null;
-    }
-    else {
-      index.setApiVersion(API_VERSION);
-      index.setGenerated(new DateTime());
-      return indexYamlBuilder.build(index, storageFacet);
-    }
+    index.setApiVersion(API_VERSION);
+    index.setGenerated(new DateTime());
+    return indexYamlBuilder.build(index, storageFacet);
   }
 
   private void parseAssetIntoChartEntry(final ChartIndex index, final Asset asset) {

src/test/java/org/sonatype/repository/helm/internal/createindex/CreateIndexServiceImplTest.java

@@ -121,15 +121,16 @@ public void testBuildIndexYaml() throws Exception {
   }
 
   @Test
-  public void testIndexYamlNotBuiltWhenNoAssets() throws Exception {
+  public void testIndexYamlBuiltEvenWhenNoAssets() throws Exception {
     when(assets.iterator()).thenReturn(assetIterator);
     when(assetIterator.next()).thenReturn(asset);
     when(asset.componentId()).thenReturn(null);
     when(helmDataAccess.browseComponentAssets(storageTx, bucket)).thenReturn(assets);
+    when(indexYamlBuilder.build(anyObject(), anyObject())).thenReturn(tempBlob);
 
     TempBlob result = underTest.buildIndexYaml(repository);
 
-    assertThat(result, is(nullValue()));
+    assertThat(result, is(notNullValue()));
   }
 
   private void initializeSystemUnderTest() {