/*
 * 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>

@protocol FNode;
@class FIndexedNode;
@protocol FCompleteChildSource;
@class FChildChangeAccumulator;
@protocol FIndex;
@class FPath;

/**
* FNodeFilter is used to update nodes and complete children of nodes while applying queries on the fly and keeping
* track of any child changes. This class does not track value changes as value changes depend on more than just the
* node itself. Different kind of queries require different kind of implementations of this interface.
*/
@protocol FNodeFilter<NSObject>

/**
* Update a single complete child in the snap. If the child equals the old child in the snap, this is a no-op.
* The method expects an indexed snap.
*/
- (FIndexedNode *) updateChildIn:(FIndexedNode *)oldSnap
                     forChildKey:(NSString *)childKey
                        newChild:(id<FNode>)newChildSnap
                    affectedPath:(FPath *)affectedPath
                      fromSource:(id<FCompleteChildSource>)source
                     accumulator:(FChildChangeAccumulator *)optChangeAccumulator;

/**
* Update a node in full and output any resulting change from this complete update.
*/
- (FIndexedNode *) updateFullNode:(FIndexedNode *)oldSnap
                      withNewNode:(FIndexedNode *)newSnap
                      accumulator:(FChildChangeAccumulator *)optChangeAccumulator;

/**
* Update the priority of the root node
*/
- (FIndexedNode *) updatePriority:(id<FNode>)priority forNode:(FIndexedNode *)oldSnap;

/**
* Returns true if children might be filtered due to query critiera
*/
- (BOOL) filtersNodes;

/**
* Returns the index filter that this filter uses to get a NodeFilter that doesn't filter any children.
*/
@property (nonatomic, strong, readonly) id<FNodeFilter> indexedFilter;

/**
* Returns the index that this filter uses
*/
@property (nonatomic, strong, readonly) id<FIndex> index;

@end
