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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>
#include <set>
#import "Firestore/Source/Core/FSTTypes.h"
#include "Firestore/core/src/firebase/firestore/model/document_key.h"
@class FSTDocumentReference;
@protocol FSTGarbageCollector;
NS_ASSUME_NONNULL_BEGIN
/**
* A pseudo-collection that maintains references to documents. FSTGarbageSource collections
* notify the FSTGarbageCollector when references to documents change through the
* -addPotentialGarbageKey: message.
*/
@protocol FSTGarbageSource
/**
* The garbage collector to which this collection should send -addPotentialGarbageKey: messages.
*/
@property(nonatomic, weak, readwrite, nullable) id<FSTGarbageCollector> garbageCollector;
/**
* Checks to see if there are any references to a document with the given key. This can be used by
* garbage collectors to double-check if a key exists in this collection when it was released
* elsewhere.
*/
- (BOOL)containsKey:(const firebase::firestore::model::DocumentKey&)key;
@end
/**
* Tracks different kinds of references to a document, for all the different ways the client
* needs to retain a document.
*
* Usually the local store this means tracking of three different types of references to a
* document:
* 1. RemoteTarget reference identified by a target ID.
* 2. LocalView reference identified also by a target ID.
* 3. Local mutation reference identified by a batch ID.
*
* The idea is that we want to keep a document around at least as long as any remote target or
* local (latency compensated) view is referencing it, or there's an outstanding local mutation to
* that document.
*/
@protocol FSTGarbageCollector
/**
* A property that describes whether or not the collector wants to eagerly collect keys.
*
* TODO(b/33384523) Delegate deleting released queries to the GC.
* This flag is a temporary workaround for dealing with a persistent query cache. The collector
* really should have an API for releasing queries that does the right thing for its policy.
*/
@property(nonatomic, assign, readonly, getter=isEager) BOOL eager;
/** Adds a garbage source to the collector. */
- (void)addGarbageSource:(id<FSTGarbageSource>)garbageSource;
/** Removes a garbage source from the collector. */
- (void)removeGarbageSource:(id<FSTGarbageSource>)garbageSource;
/**
* Notifies the garbage collector that a document with the given key may have become garbage.
*
* This is useful in both when a document has definitely been released (for example when removed
* from a garbage source) but also when a document has been updated. Documents should be marked in
* this way because the client accepts updates for documents even after the document no longer
* matches any active targets. This behavior allows the client to avoid re-showing an old document
* in the next latency-compensated view.
*/
- (void)addPotentialGarbageKey:(const firebase::firestore::model::DocumentKey&)key;
/** Returns the contents of the garbage bin and clears it. */
- (std::set<firebase::firestore::model::DocumentKey>)collectGarbage;
@end
NS_ASSUME_NONNULL_END
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