Move diff callback to options

Change-Id: I0d0d763c7e03c7d37390a2a61bd34195e12f2ca6

Author: samtstern

firestore/src/main/java/com/firebase/ui/firestore/paging/FirestorePagingAdapter.java

@@ -8,7 +8,6 @@
 import android.arch.paging.PagedListAdapter;
 import android.support.annotation.NonNull;
 import android.support.annotation.Nullable;
-import android.support.v7.util.DiffUtil;
 import android.support.v7.widget.RecyclerView;
 
 import com.firebase.ui.firestore.SnapshotParser;
@@ -50,30 +49,8 @@ public void onChanged(@Nullable PagedList<DocumentSnapshot> snapshots) {
                 }
             };
 
-    public static class DiffCallback<T> extends DiffUtil.ItemCallback<DocumentSnapshot> {
-
-        private final SnapshotParser<T> mParser;
-
-        public DiffCallback(SnapshotParser<T> parser) {
-            mParser = parser;
-        }
-
-        @Override
-        public boolean areItemsTheSame(DocumentSnapshot oldItem, DocumentSnapshot newItem) {
-            return oldItem.getId().equals(newItem.getId());
-        }
-
-        @Override
-        public boolean areContentsTheSame(DocumentSnapshot oldItem, DocumentSnapshot newItem) {
-            T oldModel = mParser.parseSnapshot(oldItem);
-            T newModel = mParser.parseSnapshot(newItem);
-
-            return oldModel.equals(newModel);
-        }
-    }
-
     public FirestorePagingAdapter(@NonNull FirestorePagingOptions<T> options) {
-        super(new DiffCallback<>(options.getParser()));
+        super(options.getDiffCallback());
 
         mParser = options.getParser();
         mData = options.getData();

firestore/src/main/java/com/firebase/ui/firestore/paging/FirestorePagingOptions.java

@@ -5,9 +5,11 @@
 import android.arch.paging.PagedList;
 import android.support.annotation.NonNull;
 import android.support.annotation.Nullable;
+import android.support.v7.util.DiffUtil;
 
 import com.firebase.ui.firestore.ClassSnapshotParser;
 import com.firebase.ui.firestore.SnapshotParser;
+import com.google.firebase.firestore.DocumentSnapshot;
 import com.google.firebase.firestore.Query;
 
 /**
@@ -17,13 +19,16 @@ public class FirestorePagingOptions<T> {
 
     private final PagingData mData;
     private final SnapshotParser<T> mParser;
+    private final DiffUtil.ItemCallback<DocumentSnapshot> mDiffCallback;
     private final LifecycleOwner mOwner;
 
     private FirestorePagingOptions(@NonNull PagingData data,
                                    @NonNull SnapshotParser<T> parser,
+                                   @NonNull DiffUtil.ItemCallback<DocumentSnapshot> diffCallback,
                                    @Nullable LifecycleOwner owner) {
         mData = data;
         mParser = parser;
+        mDiffCallback = diffCallback;
         mOwner = owner;
     }
 
@@ -37,6 +42,11 @@ public SnapshotParser<T> getParser() {
         return mParser;
     }
 
+    @NonNull
+    public DiffUtil.ItemCallback<DocumentSnapshot> getDiffCallback() {
+        return mDiffCallback;
+    }
+
     @Nullable
     public LifecycleOwner getOwner() {
         return mOwner;
@@ -47,6 +57,7 @@ public static class Builder<T> {
         private PagingData mData;
         private SnapshotParser<T> mParser;
         private LifecycleOwner mOwner;
+        private DiffUtil.ItemCallback<DocumentSnapshot> mDiffCallback;
 
         @NonNull
         public Builder<T> setQuery(@NonNull Query query,
@@ -73,9 +84,23 @@ public Builder<T> setLifecycleOwner(@NonNull LifecycleOwner owner) {
             return this;
         }
 
+        @NonNull
+        public Builder<T> setDiffCallback(@NonNull DiffUtil.ItemCallback<DocumentSnapshot> diffCallback) {
+            mDiffCallback = diffCallback;
+            return this;
+        }
+
         @NonNull
         public FirestorePagingOptions<T> build() {
-            return new FirestorePagingOptions<>(mData, mParser, mOwner);
+            if (mData == null || mParser == null) {
+                throw new IllegalStateException("Must call setQuery() before calling build().");
+            }
+
+            if (mDiffCallback == null) {
+                mDiffCallback = new SnapshotDiffCallback<T>(mParser);
+            }
+
+            return new FirestorePagingOptions<>(mData, mParser, mDiffCallback, mOwner);
         }
 
     }

firestore/src/main/java/com/firebase/ui/firestore/paging/SnapshotDiffCallback.java

@@ -0,0 +1,33 @@
+package com.firebase.ui.firestore.paging;
+
+import android.support.annotation.RestrictTo;
+import android.support.v7.util.DiffUtil;
+
+import com.firebase.ui.firestore.SnapshotParser;
+import com.google.firebase.firestore.DocumentSnapshot;
+
+/**
+ * Default diff callback implementation for Firestore snapshots.
+ */
+@RestrictTo(RestrictTo.Scope.LIBRARY_GROUP)
+public class SnapshotDiffCallback<T> extends DiffUtil.ItemCallback<DocumentSnapshot> {
+
+    private final SnapshotParser<T> mParser;
+
+    public SnapshotDiffCallback(SnapshotParser<T> parser) {
+        mParser = parser;
+    }
+
+    @Override
+    public boolean areItemsTheSame(DocumentSnapshot oldItem, DocumentSnapshot newItem) {
+        return oldItem.getId().equals(newItem.getId());
+    }
+
+    @Override
+    public boolean areContentsTheSame(DocumentSnapshot oldItem, DocumentSnapshot newItem) {
+        T oldModel = mParser.parseSnapshot(oldItem);
+        T newModel = mParser.parseSnapshot(newItem);
+
+        return oldModel.equals(newModel);
+    }
+}