// Copyright © 2022 Rangeproof Pty Ltd. All rights reserved. import Foundation import GRDB import SessionUtilitiesKit import SessionSnodeKit /// We can rely on the unique constraints within the `Interaction` table to prevent duplicate `VisibleMessage` /// values from being processed, but some control messages don’t have an associated interaction - this table provides /// a de-duping mechanism for those messages /// /// **Note:** It’s entirely possible for there to be a false-positive with this record where multiple users sent the same /// type of control message at the same time - this is very unlikely to occur though since unique to the millisecond level public struct ControlMessageProcessRecord: Codable, FetchableRecord, PersistableRecord, TableRecord, ColumnExpressible { public static var databaseTableName: String { "controlMessageProcessRecord" } /// For notifications and migrated timestamps default to '15' days (which is the timeout for messages on the /// server at the time of writing) public static let defaultExpirationSeconds: TimeInterval = (15 * 24 * 60 * 60) public typealias Columns = CodingKeys public enum CodingKeys: String, CodingKey, ColumnExpression { case threadId case timestampMs case variant case serverExpirationTimestamp } public enum Variant: Int, Codable, CaseIterable, DatabaseValueConvertible { /// **Note:** This value should only be used for entries created from the initial migration, when inserting /// new records it will check if there is an existing legacy record and if so it will attempt to create a "legacy" /// version of the new record to try and trip the unique constraint case legacyEntry = 0 case readReceipt = 1 case typingIndicator = 2 case closedGroupControlMessage = 3 case dataExtractionNotification = 4 case expirationTimerUpdate = 5 case configurationMessage = 6 case unsendRequest = 7 case messageRequestResponse = 8 case call = 9 } /// The id for the thread the control message is associated to /// /// **Note:** For user-specific control message (eg. `ConfigurationMessage`) this value will be the /// users public key public let threadId: String /// The type of control message /// /// **Note:** It would be nice to include this in the unique constraint to reduce the likelihood of false positives /// but this can result in control messages getting re-handled because the variant is unknown in the migration public let variant: Variant /// The timestamp of the control message public let timestampMs: Int64 /// The timestamp for when this message will expire on the server (will be used for garbage collection) public let serverExpirationTimestamp: TimeInterval? // MARK: - Initialization public init?( threadId: String, message: Message, serverExpirationTimestamp: TimeInterval? ) { // All `VisibleMessage` values will have an associated `Interaction` so just let // the unique constraints on that table prevent duplicate messages if message is VisibleMessage { return nil } // Allow duplicates for UnsendRequest messages, if a user received an UnsendRequest // as a push notification the it wouldn't include a serverHash and, as a result, // wouldn't get deleted from the server - since the logic only runs if we find a // matching message the safest option is to allow duplicate handling to avoid an // edge-case where a message doesn't get deleted if message is UnsendRequest { return nil } // Allow duplicates for all call messages, the double checking will be done on // message handling to make sure the messages are for the same ongoing call if message is CallMessage { return nil } // Allow '.new' and 'encryptionKeyPair' closed group control message duplicates to avoid // the following situation: // • The app performed a background poll or received a push notification // • This method was invoked and the received message timestamps table was updated // • Processing wasn't finished // • The user doesn't see the new closed group if case .new = (message as? ClosedGroupControlMessage)?.kind { return nil } if case .encryptionKeyPair = (message as? ClosedGroupControlMessage)?.kind { return nil } // For all other cases we want to prevent duplicate handling of the message (this // can happen in a number of situations, primarily with sync messages though hence // why we don't include the 'serverHash' as part of this record self.threadId = threadId self.variant = { switch message { case is ReadReceipt: return .readReceipt case is TypingIndicator: return .typingIndicator case is ClosedGroupControlMessage: return .closedGroupControlMessage case is DataExtractionNotification: return .dataExtractionNotification case is ExpirationTimerUpdate: return .expirationTimerUpdate case is ConfigurationMessage: return .configurationMessage case is UnsendRequest: return .unsendRequest case is MessageRequestResponse: return .messageRequestResponse case is CallMessage: return .call default: preconditionFailure("[ControlMessageProcessRecord] Unsupported message type") } }() self.timestampMs = Int64(message.sentTimestamp ?? 0) // Default to `0` if not set self.serverExpirationTimestamp = serverExpirationTimestamp } // MARK: - Custom Database Interaction public func willInsert(_ db: Database) throws { // If this isn't a legacy entry then check if there is a single entry and, if so, // try to create a "legacy entry" version of this record to see if a unique constraint // conflict occurs if !threadId.isEmpty && variant != .legacyEntry { let legacyEntry: ControlMessageProcessRecord? = try? ControlMessageProcessRecord .filter(Columns.threadId == "") .filter(Columns.variant == Variant.legacyEntry) .fetchOne(db) if legacyEntry != nil { try ControlMessageProcessRecord( threadId: "", variant: .legacyEntry, timestampMs: timestampMs, serverExpirationTimestamp: (legacyEntry?.serverExpirationTimestamp ?? 0) ).insert(db) } } } } // MARK: - Migration Extensions internal extension ControlMessageProcessRecord { init?( threadId: String, variant: Interaction.Variant, timestampMs: Int64 ) { switch variant { case .standardOutgoing, .standardIncoming, .standardIncomingDeleted, .infoClosedGroupCreated: return nil case .infoClosedGroupUpdated, .infoClosedGroupCurrentUserLeft: self.variant = .closedGroupControlMessage case .infoDisappearingMessagesUpdate: self.variant = .expirationTimerUpdate case .infoScreenshotNotification, .infoMediaSavedNotification: self.variant = .dataExtractionNotification case .infoMessageRequestAccepted: self.variant = .messageRequestResponse case .infoCall: self.variant = .call } self.threadId = threadId self.timestampMs = timestampMs self.serverExpirationTimestamp = ( (TimeInterval(SnodeAPI.currentOffsetTimestampMs()) / 1000) + ControlMessageProcessRecord.defaultExpirationSeconds ) } /// This method should only be used for records created during migration from the legacy /// `receivedMessageTimestamps` collection which doesn't include thread or variant info /// /// In order to get around this but maintain the unique constraints on everything we create entries for each timestamp /// for every thread and every timestamp (while this is wildly inefficient there is a garbage collection process which will /// clean out these excessive entries after `defaultExpirationSeconds`) static func generateLegacyProcessRecords(_ db: Database, receivedMessageTimestamps: [Int64]) throws { let defaultExpirationTimestamp: TimeInterval = ( (TimeInterval(SnodeAPI.currentOffsetTimestampMs()) / 1000) + ControlMessageProcessRecord.defaultExpirationSeconds ) try receivedMessageTimestamps.forEach { timestampMs in try ControlMessageProcessRecord( threadId: "", variant: .legacyEntry, timestampMs: timestampMs, serverExpirationTimestamp: defaultExpirationTimestamp ).insert(db) } } /// This method should only be called from either the `generateLegacyProcessRecords` method above or /// within the 'insert' method to maintain the unique constraint fileprivate init( threadId: String, variant: Variant, timestampMs: Int64, serverExpirationTimestamp: TimeInterval ) { self.threadId = threadId self.variant = variant self.timestampMs = timestampMs self.serverExpirationTimestamp = serverExpirationTimestamp } }