Add rewindable() support to stream

Author: Burak Serdar

crud/src/main/java/com/redhat/lightblue/crud/DocumentStream.java

@@ -31,6 +31,16 @@ public interface DocumentStream<T> extends Iterator<T>{
      */
     void close();
 
+    /**
+     * returns true if rewind works
+     */
+    default boolean canRewind() { return false; }
+
+    /**
+     * returns a new stream that starts the same resultset from the beginning. Only works if canRewind() is true
+     */
+    default DocumentStream<T> rewind() { throw new UnsupportedOperationException(); }
+
     public static <S,D> DocumentStream<D> map(final DocumentStream<S> source,final Function<S,D> map) {
         return new DocumentStream<D>() {
             @Override

crud/src/main/java/com/redhat/lightblue/crud/ListDocumentStream.java

@@ -33,11 +33,14 @@ public ListDocumentStream(List<T> list) {
         this.documents=list;
     }
 
-    /**
-     * Return the underlying list
-     */
-    public List<T> getDocuments() {
-        return documents;
+    @Override
+    public boolean canRewind() {
+        return true;
+    }
+
+    @Override
+    public DocumentStream<T> rewind() {
+        return new ListDocumentStream<T>(documents);
     }
 
     @Override

crud/src/main/java/com/redhat/lightblue/hooks/HookManager.java

@@ -33,7 +33,6 @@
 import com.redhat.lightblue.crud.CrudConstants;
 import com.redhat.lightblue.crud.DocCtx;
 import com.redhat.lightblue.crud.DocumentStream;
-import com.redhat.lightblue.crud.ListDocumentStream;
 import com.redhat.lightblue.eval.Projector;
 import com.redhat.lightblue.mediator.OperationContext;
 import com.redhat.lightblue.metadata.EntityMetadata;
@@ -228,7 +227,7 @@ private void queueHooks(CRUDOperationContext ctx, boolean mediatorHooks) {
         LOGGER.debug("Hooks are resolved: {}", hooks);
         if (!hooks.isEmpty()) {
             DocumentStream<DocCtx> documents=ctx.getDocumentStream();
-            if(documents instanceof ListDocumentStream) {
+            if(documents.canRewind()) {
                 // If this is the case, then we have access to all the documents, and
                 // we can call hooks at once
 
@@ -242,7 +241,8 @@ private void queueHooks(CRUDOperationContext ctx, boolean mediatorHooks) {
                 // list where each element gives a hook, and all the
                 // documents that will be passed to that hook.
                 List<DocHooks> docHooksList = new ArrayList<>();
-                for (DocCtx doc:((ListDocumentStream<DocCtx>)documents).getDocuments()) {
+                for (DocumentStream<DocCtx> stream=documents.rewind();stream.hasNext();) {
+                    DocCtx doc=stream.next();
                     if(!doc.hasErrors()) {
                         if (doc.getCRUDOperationPerformed() != null) {
                             Map<Hook, CRUDHook> hooksList = null;