1 files changed, 102 insertions, 0 deletions
diff --git a/Firestore/third_party/Immutable/FSTLLRBEmptyNode.m b/Firestore/third_party/Immutable/FSTLLRBEmptyNode.m
new file mode 100644
index 0000000..ec49c2c
--- /dev/null
+++ b/Firestore/third_party/Immutable/FSTLLRBEmptyNode.m
@@ -0,0 +1,102 @@
+#import "FSTLLRBEmptyNode.h"
+
+#import "FSTLLRBValueNode.h"
+
+NS_ASSUME_NONNULL_BEGIN
+
+@implementation FSTLLRBEmptyNode
+
+- (NSString *)description {
+  return @"[empty node]";
+}
+
++ (instancetype)emptyNode {
+  static dispatch_once_t pred = 0;
+  __strong static id _sharedObject = nil;
+  dispatch_once(&pred, ^{
+    _sharedObject = [[self alloc] init];  // or some other init method
+  });
+  return _sharedObject;
+}
+
+- (nullable id)key {
+  return nil;
+}
+
+- (nullable id)value {
+  return nil;
+}
+
+- (FSTLLRBColor)color {
+  return FSTLLRBColorUnspecified;
+}
+
+- (nullable id<FSTLLRBNode>)left {
+  return nil;
+}
+
+- (nullable id<FSTLLRBNode>)right {
+  return nil;
+}
+
+- (instancetype)copyWith:(id _Nullable)aKey
+               withValue:(id _Nullable)aValue
+               withColor:(FSTLLRBColor)aColor
+                withLeft:(id<FSTLLRBNode> _Nullable)aLeft
+               withRight:(id<FSTLLRBNode> _Nullable)aRight {
+  // This class is a singleton anyway, so this is more efficient than calling the constructor again.
+  return self;
+}
+
+- (id<FSTLLRBNode>)insertKey:(id)aKey forValue:(id)aValue withComparator:(NSComparator)aComparator {
+  FSTLLRBValueNode *result = [[FSTLLRBValueNode alloc] initWithKey:aKey
+                                                         withValue:aValue
+                                                         withColor:FSTLLRBColorUnspecified
+                                                          withLeft:nil
+                                                         withRight:nil];
+  return result;
+}
+
+- (id<FSTLLRBNode>)remove:(id)key withComparator:(NSComparator)aComparator {
+  return self;
+}
+
+- (NSUInteger)count {
+  return 0;
+}
+
+- (BOOL)isEmpty {
+  return YES;
+}
+
+- (BOOL)inorderTraversal:(BOOL (^)(id key, id value))action {
+  return NO;
+}
+
+- (BOOL)reverseTraversal:(BOOL (^)(id key, id value))action {
+  return NO;
+}
+
+- (id<FSTLLRBNode>)min {
+  return self;
+}
+
+- (nullable id)minKey {
+  return nil;
+}
+
+- (nullable id)maxKey {
+  return nil;
+}
+
+- (BOOL)isRed {
+  return NO;
+}
+
+- (int)check {
+  return 0;
+}
+
+@end
+
+NS_ASSUME_NONNULL_END