session-ios/SignalServiceKit/src/Messages/OWSReadReceiptManager.m

//
//  Copyright (c) 2017 Open Whisper Systems. All rights reserved.
//

#import "OWSReadReceiptManager.h"
#import "OWSMessageSender.h"
#import "OWSReadReceipt.h"
#import "OWSReadReceiptsForLinkedDevicesMessage.h"
#import "OWSReadReceiptsForSenderMessage.h"
#import "OWSSignalServiceProtos.pb.h"
#import "TSContactThread.h"
#import "TSDatabaseView.h"
#import "TSIncomingMessage.h"
#import "TSStorageManager.h"
#import "TextSecureKitEnv.h"
#import "Threading.h"

NS_ASSUME_NONNULL_BEGIN

@interface TSRecipientReadReceipt : TSYapDatabaseObject

@property (nonatomic, readonly) uint64_t sentTimestamp;
// Map of "recipient id"-to-"read timestamp".
@property (nonatomic, readonly) NSDictionary<NSString *, NSNumber *> *recipientMap;

@end

#pragma mark -

@implementation TSRecipientReadReceipt

+ (NSString *)collection
{
    return @"TSRecipientReadReceipt2";
}

- (instancetype)initWithSentTimestamp:(uint64_t)sentTimestamp
{
    OWSAssert(sentTimestamp > 0);

    self = [super initWithUniqueId:[TSRecipientReadReceipt uniqueIdForSentTimestamp:sentTimestamp]];

    if (self) {
        _sentTimestamp = sentTimestamp;
        _recipientMap = [NSDictionary new];
    }

    return self;
}

+ (NSString *)uniqueIdForSentTimestamp:(uint64_t)timestamp
{
    return [NSString stringWithFormat:@"%llu", timestamp];
}

- (void)addRecipientId:(NSString *)recipientId timestamp:(uint64_t)timestamp
{
    NSMutableDictionary<NSString *, NSNumber *> *recipientMapCopy = [self.recipientMap mutableCopy];
    recipientMapCopy[recipientId] = @(timestamp);
    _recipientMap = [recipientMapCopy copy];
}

+ (void)addRecipientId:(NSString *)recipientId
         sentTimestamp:(uint64_t)sentTimestamp
         readTimestamp:(uint64_t)readTimestamp
           transaction:(YapDatabaseReadWriteTransaction *)transaction
{
    OWSAssert(transaction);

    TSRecipientReadReceipt *_Nullable recipientReadReceipt =
        [transaction objectForKey:[self uniqueIdForSentTimestamp:sentTimestamp] inCollection:[self collection]];
    if (!recipientReadReceipt) {
        recipientReadReceipt = [[TSRecipientReadReceipt alloc] initWithSentTimestamp:sentTimestamp];
    }
    [recipientReadReceipt addRecipientId:recipientId timestamp:readTimestamp];
    [recipientReadReceipt saveWithTransaction:transaction];
}

+ (nullable NSDictionary<NSString *, NSNumber *> *)recipientMapForSentTimestamp:(uint64_t)sentTimestamp
                                                                    transaction:
                                                                        (YapDatabaseReadWriteTransaction *)transaction
{
    OWSAssert(transaction);

    TSRecipientReadReceipt *_Nullable recipientReadReceipt =
        [transaction objectForKey:[self uniqueIdForSentTimestamp:sentTimestamp] inCollection:[self collection]];
    return recipientReadReceipt.recipientMap;
}

+ (void)removeRecipientIdsForTimestamp:(uint64_t)sentTimestamp
                           transaction:(YapDatabaseReadWriteTransaction *)transaction
{
    OWSAssert(transaction);

    [transaction removeObjectForKey:[self uniqueIdForSentTimestamp:sentTimestamp] inCollection:[self collection]];
}

@end

#pragma mark -

NSString *const OWSReadReceiptManagerCollection = @"OWSReadReceiptManagerCollection";
NSString *const OWSReadReceiptManagerAreReadReceiptsEnabled = @"areReadReceiptsEnabled";

@interface OWSReadReceiptManager ()

@property (nonatomic, readonly) OWSMessageSender *messageSender;

@property (nonatomic, readonly) YapDatabaseConnection *dbConnection;

// A map of "thread unique id"-to-"read receipt" for read receipts that
// we will send to our linked devices.
//
// Should only be accessed while synchronized on the OWSReadReceiptManager.
@property (nonatomic, readonly) NSMutableDictionary<NSString *, OWSReadReceipt *> *toLinkedDevicesReadReceiptMap;

// A map of "recipient id"-to-"timestamp list" for read receipts that
// we will send to senders.
//
// Should only be accessed while synchronized on the OWSReadReceiptManager.
@property (nonatomic, readonly) NSMutableDictionary<NSString *, NSMutableSet<NSNumber *> *> *toSenderReadReceiptMap;

// Should only be accessed while synchronized on the OWSReadReceiptManager.
@property (nonatomic) BOOL isProcessing;

@property (atomic) NSNumber *areReadReceiptsEnabledCached;

@end

#pragma mark -

@implementation OWSReadReceiptManager

+ (instancetype)sharedManager
{
    static OWSReadReceiptManager *sharedMyManager = nil;
    static dispatch_once_t onceToken;
    dispatch_once(&onceToken, ^{
        sharedMyManager = [[self alloc] initDefault];
    });
    return sharedMyManager;
}

- (instancetype)initDefault
{
    OWSMessageSender *messageSender = [TextSecureKitEnv sharedEnv].messageSender;
    TSStorageManager *storageManager = [TSStorageManager sharedManager];

    return [self initWithMessageSender:messageSender storageManager:storageManager];
}

- (instancetype)initWithMessageSender:(OWSMessageSender *)messageSender
                       storageManager:(TSStorageManager *)storageManager
{
    self = [super init];

    if (!self) {
        return self;
    }

    _messageSender = messageSender;
    _dbConnection = storageManager.newDatabaseConnection;

    _toLinkedDevicesReadReceiptMap = [NSMutableDictionary new];
    _toSenderReadReceiptMap = [NSMutableDictionary new];

    OWSSingletonAssert();

    [[NSNotificationCenter defaultCenter] addObserver:self
                                             selector:@selector(databaseViewRegistrationComplete)
                                                 name:kNSNotificationName_DatabaseViewRegistrationComplete
                                               object:nil];

    // Try to start processing.
    dispatch_async(dispatch_get_main_queue(), ^{
        [self scheduleProcessing];
    });

    return self;
}

- (void)dealloc
{
    [[NSNotificationCenter defaultCenter] removeObserver:self];
}

- (void)databaseViewRegistrationComplete
{
    [self scheduleProcessing];
}

// Schedules a processing pass, unless one is already scheduled.
- (void)scheduleProcessing
{
    DispatchMainThreadSafe(^{
        @synchronized(self)
        {
            if ([TSDatabaseView hasPendingViewRegistrations]) {
                DDLogInfo(
                    @"%@ Deferring read receipt processing due to pending database view registrations.", self.tag);
                return;
            }
            if (self.isProcessing) {
                return;
            }

            self.isProcessing = YES;

            // Process read receipts every N seconds.
            //
            // We want a value high enough to allow us to effectively deduplicate,
            // read receipts without being so high that we risk not sending read
            // receipts due to app exit.
            const CGFloat kProcessingFrequencySeconds = 3.f;
            dispatch_after(dispatch_time(DISPATCH_TIME_NOW, (int64_t)(kProcessingFrequencySeconds * NSEC_PER_SEC)),
                dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0),
                ^{
                    [self process];
                });
        }
    });
}

- (void)process
{
    @synchronized(self)
    {
        DDLogVerbose(@"%@ Processing read receipts.", self.tag);

        self.isProcessing = NO;

        NSArray<OWSReadReceipt *> *readReceiptsForLinkedDevices = [self.toLinkedDevicesReadReceiptMap allValues];
        [self.toLinkedDevicesReadReceiptMap removeAllObjects];
        if (readReceiptsForLinkedDevices.count > 0) {
            OWSReadReceiptsForLinkedDevicesMessage *message =
                [[OWSReadReceiptsForLinkedDevicesMessage alloc] initWithReadReceipts:readReceiptsForLinkedDevices];

            dispatch_async(dispatch_get_main_queue(), ^{
                [self.messageSender sendMessage:message
                    success:^{
                        DDLogInfo(@"%@ Successfully sent %zd read receipt to linked devices.",
                            self.tag,
                            readReceiptsForLinkedDevices.count);
                    }
                    failure:^(NSError *error) {
                        DDLogError(@"%@ Failed to send read receipt to linked devices with error: %@", self.tag, error);
                    }];
            });
        }

        NSArray<OWSReadReceipt *> *readReceiptsToSend = [self.toLinkedDevicesReadReceiptMap allValues];
        [self.toLinkedDevicesReadReceiptMap removeAllObjects];
        if (self.toSenderReadReceiptMap.count > 0) {
            for (NSString *recipientId in self.toSenderReadReceiptMap) {
                NSSet<NSNumber *> *timestamps = self.toSenderReadReceiptMap[recipientId];
                OWSAssert(timestamps.count > 0);

                TSThread *thread = [TSContactThread getOrCreateThreadWithContactId:recipientId];
                OWSReadReceiptsForSenderMessage *message =
                    [[OWSReadReceiptsForSenderMessage alloc] initWithThread:thread
                                                          messageTimestamps:timestamps.allObjects];

                dispatch_async(dispatch_get_main_queue(), ^{
                    [self.messageSender sendMessage:message
                        success:^{
                            DDLogInfo(@"%@ Successfully sent %zd read receipts to sender.",
                                self.tag,
                                readReceiptsToSend.count);
                        }
                        failure:^(NSError *error) {
                            DDLogError(@"%@ Failed to send read receipts to sender with error: %@", self.tag, error);
                        }];
                });
            }
            [self.toSenderReadReceiptMap removeAllObjects];
        }
    }
}

#pragma mark - Mark as Read Locally

- (void)markAsReadLocallyBeforeTimestamp:(uint64_t)timestamp thread:(TSThread *)thread
{
    OWSAssert(thread);

    dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0), ^{
        [self.dbConnection readWriteWithBlock:^(YapDatabaseReadWriteTransaction *transaction) {
            NSMutableArray<id<OWSReadTracking>> *interactions = [NSMutableArray new];

            [[TSDatabaseView unseenDatabaseViewExtension:transaction]
                enumerateRowsInGroup:thread.uniqueId
                          usingBlock:^(NSString *collection,
                              NSString *key,
                              id object,
                              id metadata,
                              NSUInteger index,
                              BOOL *stop) {

                              if (![object conformsToProtocol:@protocol(OWSReadTracking)]) {
                                  OWSFail(
                                      @"Expected to conform to OWSReadTracking: object with class: %@ collection: %@ "
                                      @"key: %@",
                                      [object class],
                                      collection,
                                      key);
                                  return;
                              }
                              id<OWSReadTracking> possiblyRead = (id<OWSReadTracking>)object;

                              if (possiblyRead.timestampForSorting > timestamp) {
                                  *stop = YES;
                                  return;
                              }

                              OWSAssert(!possiblyRead.read);
                              if (!possiblyRead.read) {
                                  [interactions addObject:possiblyRead];
                              }
                          }];

            if (interactions.count < 1) {
                return;
            }
            DDLogError(@"Marking %zd messages as read.", interactions.count);
            for (id<OWSReadTracking> possiblyRead in interactions) {
                [possiblyRead markAsReadWithTransaction:transaction sendReadReceipt:YES updateExpiration:YES];
            }
        }];
    });
}

- (void)messageWasReadLocally:(TSIncomingMessage *)message
{
    dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0), ^{
        @synchronized(self)
        {
            NSString *threadUniqueId = message.uniqueThreadId;
            OWSAssert(threadUniqueId.length > 0);

            NSString *messageAuthorId = message.messageAuthorId;
            OWSAssert(messageAuthorId.length > 0);

            OWSReadReceipt *newReadReceipt =
                [[OWSReadReceipt alloc] initWithSenderId:messageAuthorId timestamp:message.timestamp];

            OWSReadReceipt *_Nullable oldReadReceipt = self.toLinkedDevicesReadReceiptMap[threadUniqueId];
            if (oldReadReceipt && oldReadReceipt.timestamp > newReadReceipt.timestamp) {
                // If there's an existing read receipt for the same thread with
                // a newer timestamp, discard the new read receipt.
                DDLogVerbose(@"%@ Ignoring redundant read receipt for linked devices.", self.tag);
            } else {
                DDLogVerbose(@"%@ Enqueuing read receipt for linked devices.", self.tag);
                self.toLinkedDevicesReadReceiptMap[threadUniqueId] = newReadReceipt;
            }

            if ([self areReadReceiptsEnabled]) {
                DDLogVerbose(@"%@ Enqueuing read receipt for sender.", self.tag);
                NSMutableSet<NSNumber *> *_Nullable timestamps = self.toSenderReadReceiptMap[messageAuthorId];
                if (!timestamps) {
                    timestamps = [NSMutableSet new];
                    self.toSenderReadReceiptMap[messageAuthorId] = timestamps;
                }
                [timestamps addObject:@(message.timestamp)];
            }

            [self scheduleProcessing];
        }
    });
}

#pragma mark - Read Receipts From Recipient

- (void)processReadReceiptsFromRecipient:(OWSSignalServiceProtosReceiptMessage *)receiptMessage
                                envelope:(OWSSignalServiceProtosEnvelope *)envelope
{
    OWSAssert(receiptMessage);
    OWSAssert(envelope);
    OWSAssert(receiptMessage.type == OWSSignalServiceProtosReceiptMessageTypeRead);

    if (![self areReadReceiptsEnabled]) {
        DDLogInfo(@"%@ Ignoring incoming receipt message as read receipts are disabled.", self.tag);
        return;
    }

    NSString *recipientId = envelope.source;
    OWSAssert(recipientId.length > 0);

    PBArray *sentTimestamps = receiptMessage.timestamp;
    UInt64 readTimestamp = envelope.timestamp;

    dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0), ^{
        [self.dbConnection readWriteWithBlock:^(YapDatabaseReadWriteTransaction *transaction) {
            for (int i = 0; i < sentTimestamps.count; i++) {
                UInt64 sentTimestamp = [sentTimestamps uint64AtIndex:i];

                NSArray<TSOutgoingMessage *> *messages
                    = (NSArray<TSOutgoingMessage *> *)[TSInteraction interactionsWithTimestamp:sentTimestamp
                                                                                       ofClass:[TSOutgoingMessage class]
                                                                               withTransaction:transaction];
                OWSAssert(messages.count <= 1);
                if (messages.count > 0) {
                    // TODO: We might also need to "mark as read by recipient" any older messages
                    // from us in that thread.  Or maybe this state should hang on the thread?
                    for (TSOutgoingMessage *message in messages) {
                        [message updateWithReadRecipientId:recipientId
                                             readTimestamp:readTimestamp
                                               transaction:transaction];
                    }
                } else {
                    // Persist the read receipts so that we can apply them to outgoing messages
                    // that we learn about later through sync messages.
                    [TSRecipientReadReceipt addRecipientId:recipientId
                                             sentTimestamp:sentTimestamp
                                             readTimestamp:readTimestamp
                                               transaction:transaction];
                }
            }
        }];
    });
}

- (void)updateOutgoingMessageFromLinkedDevice:(TSOutgoingMessage *)message
                                  transaction:(YapDatabaseReadWriteTransaction *)transaction
{
    OWSAssert(message);
    OWSAssert(transaction);

    uint64_t sentTimestamp = message.timestamp;
    NSDictionary<NSString *, NSNumber *> *recipientMap =
        [TSRecipientReadReceipt recipientMapForSentTimestamp:sentTimestamp transaction:transaction];
    if (!recipientMap) {
        return;
    }
    OWSAssert(recipientMap.count > 0);
    for (NSString *recipientId in recipientMap) {
        NSNumber *nsReadTimestamp = recipientMap[recipientId];
        uint64_t readTimestamp = [nsReadTimestamp unsignedLongLongValue];

        [message updateWithReadRecipientId:recipientId readTimestamp:readTimestamp transaction:transaction];
    }
    [TSRecipientReadReceipt removeRecipientIdsForTimestamp:message.timestamp transaction:transaction];
}

#pragma mark - Settings

- (void)prepareCachedValues
{
    [self areReadReceiptsEnabled];
}

- (BOOL)areReadReceiptsEnabled
{
    // We don't need to worry about races around this cached value.
    if (!self.areReadReceiptsEnabledCached) {
        // Default to NO.
        self.areReadReceiptsEnabledCached = @([self.dbConnection boolForKey:OWSReadReceiptManagerAreReadReceiptsEnabled
                                                               inCollection:OWSReadReceiptManagerCollection]);
    }

    return [self.areReadReceiptsEnabledCached boolValue];
}

- (void)setAreReadReceiptsEnabled:(BOOL)value
{
    DDLogInfo(@"%@ areReadReceiptsEnabled: %d.", self.tag, value);

    [self.dbConnection setBool:value
                        forKey:OWSReadReceiptManagerAreReadReceiptsEnabled
                  inCollection:OWSReadReceiptManagerCollection];
    self.areReadReceiptsEnabledCached = @(value);
}

#pragma mark - Logging

+ (NSString *)tag
{
    return [NSString stringWithFormat:@"[%@]", self.class];
}

- (NSString *)tag
{
    return self.class.tag;
}

@end

NS_ASSUME_NONNULL_END