1 files changed, 107 insertions, 0 deletions
diff --git a/Firebase/Database/Core/FRangeMerge.m b/Firebase/Database/Core/FRangeMerge.m
new file mode 100644
index 0000000..8bc67bf
--- /dev/null
+++ b/Firebase/Database/Core/FRangeMerge.m
@@ -0,0 +1,107 @@
+/*
+ * 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 "FRangeMerge.h"
+
+#import "FEmptyNode.h"
+
+@interface FRangeMerge ()
+
+@property (nonatomic, strong) FPath *optExclusiveStart;
+@property (nonatomic, strong) FPath *optInclusiveEnd;
+@property (nonatomic, strong) id<FNode> updates;
+
+@end
+
+@implementation FRangeMerge
+
+- (instancetype)initWithStart:(FPath *)start end:(FPath *)end updates:(id<FNode>)updates {
+    self = [super init];
+    if (self != nil) {
+        self->_optExclusiveStart = start;
+        self->_optInclusiveEnd = end;
+        self->_updates = updates;
+    }
+    return self;
+}
+
+- (id<FNode>)applyToNode:(id<FNode>)node {
+    return [self updateRangeInNode:[FPath empty] node:node updates:self.updates];
+}
+
+- (id<FNode>)updateRangeInNode:(FPath *)currentPath node:(id<FNode>)node updates:(id<FNode>)updates {
+    NSComparisonResult startComparison = (self.optExclusiveStart == nil) ? NSOrderedDescending : [currentPath compare:self.optExclusiveStart];
+    NSComparisonResult endComparison = (self.optInclusiveEnd == nil) ? NSOrderedAscending : [currentPath compare:self.optInclusiveEnd];
+    BOOL startInNode = self.optExclusiveStart != nil && [currentPath contains:self.optExclusiveStart];
+    BOOL endInNode = self.optInclusiveEnd != nil && [currentPath contains:self.optInclusiveEnd];
+    if (startComparison == NSOrderedDescending && endComparison == NSOrderedAscending && !endInNode) {
+        // child is completly contained
+        return updates;
+    } else if (startComparison == NSOrderedDescending && endInNode && [updates isLeafNode]) {
+        return updates;
+    } else if (startComparison == NSOrderedDescending && endComparison == NSOrderedSame) {
+        NSAssert(endInNode, @"End not in node");
+        NSAssert(![updates isLeafNode], @"Found leaf node update, this case should have been handled above.");
+        if ([node isLeafNode]) {
+            // Update node was not a leaf node, so we can delete it
+            return [FEmptyNode emptyNode];
+        } else {
+            // Unaffected by range, ignore
+            return node;
+        }
+    } else if (startInNode || endInNode) {
+        // There is a partial update we need to do, so collect all relevant children
+        NSMutableSet *allChildren = [NSMutableSet set];
+        [node enumerateChildrenUsingBlock:^(NSString *key, id<FNode> node, BOOL *stop) {
+            [allChildren addObject:key];
+        }];
+        [updates enumerateChildrenUsingBlock:^(NSString *key, id<FNode> node, BOOL *stop) {
+            [allChildren addObject:key];
+        }];
+
+        __block id<FNode> newNode = node;
+        void (^action)(id, BOOL *) = ^void(NSString *key, BOOL *stop) {
+            id<FNode> currentChild = [node getImmediateChild:key];
+            id<FNode> updatedChild = [self updateRangeInNode:[currentPath childFromString:key]
+                                                        node:currentChild
+                                                     updates:[updates getImmediateChild:key]];
+            // Only need to update if the node changed
+            if (updatedChild != currentChild) {
+                newNode = [newNode updateImmediateChild:key withNewChild:updatedChild];
+            }
+        };
+
+        [allChildren enumerateObjectsUsingBlock:action];
+
+        // Add priority last, so the node is not empty when applying
+        if (!updates.getPriority.isEmpty || !node.getPriority.isEmpty) {
+            BOOL stop = NO;
+            action(@".priority", &stop);
+        }
+        return newNode;
+    } else {
+        // Unaffected by this range
+        NSAssert(endComparison == NSOrderedDescending || startComparison <= NSOrderedSame, @"Invalid range for update");
+        return node;
+    }
+}
+
+- (NSString *)description {
+    return [NSString stringWithFormat:@"RangeMerge (optExclusiveStart = %@, optExclusiveEng = %@, updates = %@)",
+            self.optExclusiveStart, self.optInclusiveEnd, self.updates];
+}
+
+@end