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diff --git a/Firestore/Source/Core/FSTView.h b/Firestore/Source/Core/FSTView.h
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+/*
+ * Copyright 2017 Google
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#import <Foundation/Foundation.h>
+
+#import "FSTDocumentDictionary.h"
+#import "FSTDocumentKeySet.h"
+
+@class FSTDocumentKey;
+@class FSTDocumentSet;
+@class FSTDocumentViewChangeSet;
+@class FSTMaybeDocument;
+@class FSTQuery;
+@class FSTTargetChange;
+@class FSTViewSnapshot;
+
+NS_ASSUME_NONNULL_BEGIN
+
+#pragma mark - FSTViewDocumentChanges
+
+/** The result of applying a set of doc changes to a view. */
+@interface FSTViewDocumentChanges : NSObject
+
+- (instancetype)init NS_UNAVAILABLE;
+
+/** The new set of docs that should be in the view. */
+@property(nonatomic, strong, readonly) FSTDocumentSet *documentSet;
+
+/** The diff of this these docs with the previous set of docs. */
+@property(nonatomic, strong, readonly) FSTDocumentViewChangeSet *changeSet;
+
+/**
+ * Whether the set of documents passed in was not sufficient to calculate the new state of the view
+ * and there needs to be another pass based on the local cache.
+ */
+@property(nonatomic, assign, readonly) BOOL needsRefill;
+
+@property(nonatomic, strong, readonly) FSTDocumentKeySet *mutatedKeys;
+
+@end
+
+#pragma mark - FSTLimboDocumentChange
+
+typedef NS_ENUM(NSInteger, FSTLimboDocumentChangeType) {
+  FSTLimboDocumentChangeTypeAdded = 0,
+  FSTLimboDocumentChangeTypeRemoved,
+};
+
+// A change to a particular document wrt to whether it is in "limbo".
+@interface FSTLimboDocumentChange : NSObject
+
++ (instancetype)changeWithType:(FSTLimboDocumentChangeType)type key:(FSTDocumentKey *)key;
+
+- (id)init __attribute__((unavailable("Use a static constructor method.")));
+
+@property(nonatomic, assign, readonly) FSTLimboDocumentChangeType type;
+@property(nonatomic, strong, readonly) FSTDocumentKey *key;
+@end
+
+#pragma mark - FSTViewChange
+
+// A set of changes to a view.
+@interface FSTViewChange : NSObject
+
+- (id)init __attribute__((unavailable("Use a static constructor method.")));
+
+@property(nonatomic, strong, readonly, nullable) FSTViewSnapshot *snapshot;
+@property(nonatomic, strong, readonly) NSArray<FSTLimboDocumentChange *> *limboChanges;
+@end
+
+#pragma mark - FSTView
+
+/**
+ * View is responsible for computing the final merged truth of what docs are in a query. It gets
+ * notified of local and remote changes to docs, and applies the query filters and limits to
+ * determine the most correct possible results.
+ */
+@interface FSTView : NSObject
+
+- (instancetype)init NS_UNAVAILABLE;
+
+- (instancetype)initWithQuery:(FSTQuery *)query
+              remoteDocuments:(FSTDocumentKeySet *)remoteDocuments NS_DESIGNATED_INITIALIZER;
+
+/**
+ * Iterates over a set of doc changes, applies the query limit, and computes what the new results
+ * should be, what the changes were, and whether we may need to go back to the local cache for
+ * more results. Does not make any changes to the view.
+ *
+ * @param docChanges The doc changes to apply to this view.
+ * @return a new set of docs, changes, and refill flag.
+ */
+- (FSTViewDocumentChanges *)computeChangesWithDocuments:(FSTMaybeDocumentDictionary *)docChanges;
+
+/**
+ * Iterates over a set of doc changes, applies the query limit, and computes what the new results
+ * should be, what the changes were, and whether we may need to go back to the local cache for
+ * more results. Does not make any changes to the view.
+ *
+ * @param docChanges The doc changes to apply to this view.
+ * @param previousChanges If this is being called with a refill, then start with this set of docs
+ *     and changes instead of the current view.
+ * @return a new set of docs, changes, and refill flag.
+ */
+- (FSTViewDocumentChanges *)computeChangesWithDocuments:(FSTMaybeDocumentDictionary *)docChanges
+                                        previousChanges:
+                                            (nullable FSTViewDocumentChanges *)previousChanges;
+
+/**
+ * Updates the view with the given ViewDocumentChanges.
+ *
+ * @param docChanges The set of changes to make to the view's docs.
+ * @return A new FSTViewChange with the given docs, changes, and sync state.
+ */
+- (FSTViewChange *)applyChangesToDocuments:(FSTViewDocumentChanges *)docChanges;
+
+/**
+ * Updates the view with the given FSTViewDocumentChanges and updates limbo docs and sync state from
+ * the given (optional) target change.
+ *
+ * @param docChanges The set of changes to make to the view's docs.
+ * @param targetChange A target change to apply for computing limbo docs and sync state.
+ * @return A new FSTViewChange with the given docs, changes, and sync state.
+ */
+- (FSTViewChange *)applyChangesToDocuments:(FSTViewDocumentChanges *)docChanges
+                              targetChange:(nullable FSTTargetChange *)targetChange;
+
+@end
+
+NS_ASSUME_NONNULL_END