From 04bd571d8bc69f00a527cea11baf589a64944cc9 Mon Sep 17 00:00:00 2001
From: Drew Koszewnik <dkoszewnik@netflix.com>
Date: Tue, 4 Apr 2017 15:09:15 -0700
Subject: [PATCH] HollowProducer: expose the prior ReadState

---
 .../netflix/hollow/api/producer/HollowProducer.java  | 12 +++++-------
 .../netflix/hollow/api/producer/WriteStateImpl.java  | 10 +++++++++-
 2 files changed, 14 insertions(+), 8 deletions(-)

diff --git a/hollow/src/main/java/com/netflix/hollow/api/producer/HollowProducer.java b/hollow/src/main/java/com/netflix/hollow/api/producer/HollowProducer.java
index 2659817416..be597666a3 100644
--- a/hollow/src/main/java/com/netflix/hollow/api/producer/HollowProducer.java
+++ b/hollow/src/main/java/com/netflix/hollow/api/producer/HollowProducer.java
@@ -26,9 +26,10 @@
 import com.netflix.hollow.api.client.HollowBlobRetriever;
 import com.netflix.hollow.api.client.HollowClient;
 import com.netflix.hollow.api.consumer.HollowConsumer;
+import com.netflix.hollow.api.consumer.HollowConsumer.ReadState;
 import com.netflix.hollow.api.producer.HollowProducerListener.ProducerStatus;
-import com.netflix.hollow.api.producer.HollowProducerListener.RestoreStatus;
 import com.netflix.hollow.api.producer.HollowProducerListener.PublishStatus;
+import com.netflix.hollow.api.producer.HollowProducerListener.RestoreStatus;
 import com.netflix.hollow.core.read.engine.HollowBlobHeaderReader;
 import com.netflix.hollow.core.read.engine.HollowBlobReader;
 import com.netflix.hollow.core.read.engine.HollowReadStateEngine;
@@ -38,7 +39,6 @@
 import com.netflix.hollow.core.write.HollowWriteStateEngine;
 import com.netflix.hollow.core.write.objectmapper.HollowObjectMapper;
 import com.netflix.hollow.tools.checksum.HollowChecksum;
-
 import java.io.BufferedInputStream;
 import java.io.BufferedOutputStream;
 import java.io.File;
@@ -61,10 +61,6 @@ public class HollowProducer {
         public void validate(HollowConsumer.ReadState readState) {}
     };
 
-    public static WriteState newWriteState(long version, HollowObjectMapper objectMapper) {
-        return new WriteStateImpl(version, objectMapper);
-    }
-
     private final Publisher publisher;
     private final Validator validator;
     private final Announcer announcer;
@@ -148,7 +144,7 @@ public void runCycle(Populator task) {
             // 1a. Prepare the write state
             writeEngine.prepareForNextCycle();
             HollowObjectMapper objectMapper = this.objectMapper;
-            WriteState writeState = newWriteState(toVersion, objectMapper);
+            WriteState writeState = new WriteStateImpl(toVersion, objectMapper, readStates.current());
 
             // 2. Populate the state
             ProducerStatus.Builder populateStatus = listeners.firePopulateStart(toVersion);
@@ -383,6 +379,8 @@ public static interface WriteState {
         HollowObjectMapper getObjectMapper();
 
         HollowWriteStateEngine getStateEngine();
+        
+        ReadState getPriorState();
 
         long getVersion();
     }
diff --git a/hollow/src/main/java/com/netflix/hollow/api/producer/WriteStateImpl.java b/hollow/src/main/java/com/netflix/hollow/api/producer/WriteStateImpl.java
index fdeb5ce9a7..f734d213ce 100644
--- a/hollow/src/main/java/com/netflix/hollow/api/producer/WriteStateImpl.java
+++ b/hollow/src/main/java/com/netflix/hollow/api/producer/WriteStateImpl.java
@@ -17,6 +17,7 @@
  */
 package com.netflix.hollow.api.producer;
 
+import com.netflix.hollow.api.consumer.HollowConsumer.ReadState;
 import com.netflix.hollow.core.write.HollowWriteStateEngine;
 import com.netflix.hollow.core.write.objectmapper.HollowObjectMapper;
 
@@ -28,10 +29,12 @@
 final class WriteStateImpl implements HollowProducer.WriteState {
     private final long version;
     private final HollowObjectMapper objectMapper;
+    private final ReadState priorReadState;
 
-    protected WriteStateImpl(long version, HollowObjectMapper objectMapper) {
+    protected WriteStateImpl(long version, HollowObjectMapper objectMapper, ReadState priorReadState) {
         this.version = version;
         this.objectMapper = objectMapper;
+        this.priorReadState = priorReadState;
     }
 
     @Override
@@ -53,4 +56,9 @@ public HollowWriteStateEngine getStateEngine() {
     public long getVersion() {
         return version;
     }
+
+    @Override
+    public ReadState getPriorState() {
+        return priorReadState;
+    }
 }