1 files changed, 80 insertions, 0 deletions
diff --git a/Firestore/Source/Core/FSTSnapshotVersion.mm b/Firestore/Source/Core/FSTSnapshotVersion.mm
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+++ b/Firestore/Source/Core/FSTSnapshotVersion.mm
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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 "Firestore/Source/Core/FSTSnapshotVersion.h"
+
+#import "Firestore/Source/Core/FSTTimestamp.h"
+
+NS_ASSUME_NONNULL_BEGIN
+
+@implementation FSTSnapshotVersion
+
++ (instancetype)noVersion {
+  static FSTSnapshotVersion *min;
+  static dispatch_once_t onceToken;
+  dispatch_once(&onceToken, ^{
+    FSTTimestamp *timestamp = [[FSTTimestamp alloc] initWithSeconds:0 nanos:0];
+    min = [FSTSnapshotVersion versionWithTimestamp:timestamp];
+  });
+  return min;
+}
+
++ (instancetype)versionWithTimestamp:(FSTTimestamp *)timestamp {
+  return [[FSTSnapshotVersion alloc] initWithTimestamp:timestamp];
+}
+
+- (instancetype)initWithTimestamp:(FSTTimestamp *)timestamp {
+  self = [super init];
+  if (self) {
+    _timestamp = timestamp;
+  }
+  return self;
+}
+
+#pragma mark - NSObject methods
+
+- (BOOL)isEqual:(id)object {
+  if (self == object) {
+    return YES;
+  }
+  if (![object isKindOfClass:[FSTSnapshotVersion class]]) {
+    return NO;
+  }
+  return [self.timestamp isEqual:((FSTSnapshotVersion *)object).timestamp];
+}
+
+- (NSUInteger)hash {
+  return self.timestamp.hash;
+}
+
+- (NSString *)description {
+  return [NSString stringWithFormat:@"<FSTSnapshotVersion: %@>", self.timestamp];
+}
+
+- (id)copyWithZone:(NSZone *_Nullable)zone {
+  // Implements NSCopying without actually copying because timestamps are immutable.
+  return self;
+}
+
+#pragma mark - Public methods
+
+- (NSComparisonResult)compare:(FSTSnapshotVersion *)other {
+  return [self.timestamp compare:other.timestamp];
+}
+
+@end
+
+NS_ASSUME_NONNULL_END