Signal-iOS/SignalServiceKit/src/Network/MessageSenderJobQueue.swift

//
//  Copyright (c) 2020 Open Whisper Systems. All rights reserved.
//

import Foundation

/// Durably enqueues a message for sending.
///
/// The queue's operations (`MessageSenderOperation`) uses `MessageSender` to send a message.
///
/// ## Retry behavior
///
/// Like all JobQueue's, MessageSenderJobQueue implements retry handling for operation errors.
///
/// `MessageSender` also includes it's own retry logic necessary to encapsulate business logic around
/// a user changing their Registration ID, or adding/removing devices. That is, it is sometimes *normal*
/// for MessageSender to have to resend to a recipient multiple times before it is accepted, and doesn't
/// represent a "failure" from the application standpoint.
///
/// So we have an inner non-durable retry (MessageSender) and an outer durable retry (MessageSenderJobQueue).
///
/// Both respect the `error.isRetryable` convention to be sure we don't keep retrying in some situations
/// (e.g. rate limiting)
public class MessageSenderJobQueue: NSObject, JobQueue {

    @objc
    public override init() {
        super.init()

        AppReadiness.runNowOrWhenAppDidBecomeReadyPolite {
            self.setup()
        }
    }

    // MARK: 

    @objc(addMessage:transaction:)
    public func add(message: OutgoingMessagePreparer, transaction: SDSAnyWriteTransaction) {
        self.add(message: message, removeMessageAfterSending: false, transaction: transaction)
    }

    @objc(addMediaMessage:dataSource:contentType:sourceFilename:caption:albumMessageId:isTemporaryAttachment:)
    public func add(mediaMessage: TSOutgoingMessage, dataSource: DataSource, contentType: String, sourceFilename: String?, caption: String?, albumMessageId: String?, isTemporaryAttachment: Bool) {
        let attachmentInfo = OutgoingAttachmentInfo(dataSource: dataSource, contentType: contentType, sourceFilename: sourceFilename, caption: caption, albumMessageId: albumMessageId)
        let message = OutgoingMessagePreparer(mediaMessage, unsavedAttachmentInfos: [attachmentInfo])
        add(message: message, isTemporaryAttachment: isTemporaryAttachment)
    }

    @objc(addMessage:isTemporaryAttachment:)
    public func add(message: OutgoingMessagePreparer, isTemporaryAttachment: Bool) {
        databaseStorage.asyncWrite { transaction in
            self.add(message: message,
                     removeMessageAfterSending: isTemporaryAttachment,
                     transaction: transaction)

        }
    }

    private func add(message: OutgoingMessagePreparer, removeMessageAfterSending: Bool, transaction: SDSAnyWriteTransaction) {
        assert(AppReadiness.isAppReady() || CurrentAppContext().isRunningTests)
        do {
            let messageRecord = try message.prepareMessage(transaction: transaction)
            let jobRecord = try SSKMessageSenderJobRecord(message: messageRecord, removeMessageAfterSending: removeMessageAfterSending, label: self.jobRecordLabel, transaction: transaction)
            self.add(jobRecord: jobRecord, transaction: transaction)
        } catch {
            message.unpreparedMessage.update(sendingError: error, transaction: transaction)
        }
    }

    // MARK: JobQueue

    public typealias DurableOperationType = MessageSenderOperation
    @objc
    public static let jobRecordLabel: String = "MessageSender"
    public static let maxRetries: UInt = 30
    public let requiresInternet: Bool = true
    public var runningOperations = AtomicArray<MessageSenderOperation>()

    public var jobRecordLabel: String {
        return type(of: self).jobRecordLabel
    }

    @objc
    public func setup() {
        defaultSetup()
    }

    public var isSetup = AtomicBool(false)

    public func didMarkAsReady(oldJobRecord: SSKMessageSenderJobRecord, transaction: SDSAnyWriteTransaction) {
        if let messageId = oldJobRecord.messageId, let message = TSOutgoingMessage.anyFetch(uniqueId: messageId, transaction: transaction) as? TSOutgoingMessage {
            message.updateAllUnsentRecipientsAsSending(transaction: transaction)
        }
    }

    public func buildOperation(jobRecord: SSKMessageSenderJobRecord, transaction: SDSAnyReadTransaction) throws -> MessageSenderOperation {
        let message: TSOutgoingMessage
        if let invisibleMessage = jobRecord.invisibleMessage {
            message = invisibleMessage
        } else if let messageId = jobRecord.messageId, let fetchedMessage = TSOutgoingMessage.anyFetch(uniqueId: messageId, transaction: transaction) as? TSOutgoingMessage {
            message = fetchedMessage
        } else {
            assert(jobRecord.messageId != nil)
            throw JobError.obsolete(description: "message no longer exists")
        }

        let operation = MessageSenderOperation(message: message, jobRecord: jobRecord)

        // Media messages run on their own queue to not block future non-media sends,
        // but should not start sending until all previous operations have executed.
        // We can guarantee this by adding another operation to the send queue that
        // we depend upon.
        //
        // For example, if you send text messages A, B and then media message C
        // message C should never send before A and B. However, if you send text
        // messages A, B, then media message C, followed by text message D, D cannot
        // send before A and B, but CAN send before C.
        if jobRecord.isMediaMessage, let sendQueue = senderQueues[message.uniqueThreadId] {
            let orderMaintainingOperation = Operation()
            orderMaintainingOperation.queuePriority = MessageSender.queuePriority(for: message)
            sendQueue.addOperation(orderMaintainingOperation)
            operation.addDependency(orderMaintainingOperation)
        }

        return operation
    }

    var senderQueues: [String: OperationQueue] = [:]
    var mediaSenderQueues: [String: OperationQueue] = [:]
    let defaultQueue: OperationQueue = {
        let operationQueue = OperationQueue()
        operationQueue.name = "DefaultSendingQueue"
        operationQueue.maxConcurrentOperationCount = 1

        return operationQueue
    }()

    // We use a per-thread serial OperationQueue to ensure messages are delivered to the
    // service in the order the user sent them.
    public func operationQueue(jobRecord: SSKMessageSenderJobRecord) -> OperationQueue {
        guard let threadId = jobRecord.threadId else {
            return defaultQueue
        }

        if jobRecord.isMediaMessage {
            guard let existingQueue = mediaSenderQueues[threadId] else {
                let operationQueue = OperationQueue()
                operationQueue.name = "MediaSendingQueue:\(threadId)"
                operationQueue.maxConcurrentOperationCount = 1

                mediaSenderQueues[threadId] = operationQueue

                return operationQueue
            }

            return existingQueue
        } else {
            guard let existingQueue = senderQueues[threadId] else {
                let operationQueue = OperationQueue()
                operationQueue.name = "SendingQueue:\(threadId)"
                operationQueue.maxConcurrentOperationCount = 1

                senderQueues[threadId] = operationQueue

                return operationQueue
            }

            return existingQueue
        }
    }

    @objc
    public static func enumerateEnqueuedInteractions(transaction: SDSAnyReadTransaction, block: @escaping (TSInteraction, UnsafeMutablePointer<ObjCBool>) -> Void) {

        let finder = AnyJobRecordFinder<SSKMessageSenderJobRecord>()
        finder.enumerateJobRecords(label: self.jobRecordLabel, transaction: transaction) { job, stop in
            if let interaction = job.invisibleMessage {
                block(interaction, stop)
                return
            }
            guard let messageId = job.messageId else {
                return
            }
            guard let interaction = TSInteraction.anyFetch(uniqueId: messageId, transaction: transaction) else {
                // Interaction may have been deleted.
                Logger.warn("Missing interaction")
                return
            }
            block(interaction, stop)
        }
    }
}

public class MessageSenderOperation: OWSOperation, DurableOperation {

    // MARK: DurableOperation

    public let jobRecord: SSKMessageSenderJobRecord

    weak public var durableOperationDelegate: MessageSenderJobQueue?

    public var operation: OWSOperation {
        return self
    }

    // MARK: Init

    let message: TSOutgoingMessage

    init(message: TSOutgoingMessage, jobRecord: SSKMessageSenderJobRecord) {
        self.message = message
        self.jobRecord = jobRecord

        super.init()

        self.queuePriority = MessageSender.queuePriority(for: message)
    }

    // MARK: Dependencies

    var messageSender: MessageSender {
        return SSKEnvironment.shared.messageSender
    }

    var databaseStorage: SDSDatabaseStorage {
        return SDSDatabaseStorage.shared
    }

    // MARK: OWSOperation

    override public func run() {
        self.messageSender.sendMessage(message.asPreparer,
                                       success: reportSuccess,
                                       failure: reportError(withUndefinedRetry:))
    }

    override public func didSucceed() {
        databaseStorage.write { transaction in
            self.durableOperationDelegate?.durableOperationDidSucceed(self, transaction: transaction)
            if self.jobRecord.removeMessageAfterSending {
                self.message.anyRemove(transaction: transaction)
                self.message.removeTemporaryAttachments(with: transaction)
            }
        }
    }

    override public func didReportError(_ error: Error) {
        Logger.debug("remainingRetries: \(self.remainingRetries)")

        databaseStorage.write { transaction in
            self.durableOperationDelegate?.durableOperation(self, didReportError: error, transaction: transaction)
        }
    }

    override public func retryInterval() -> TimeInterval {
        // Arbitrary backoff factor...
        // With backOffFactor of 1.9
        // try  1 delay:  0.00s
        // try  2 delay:  0.19s
        // ...
        // try  5 delay:  1.30s
        // ...
        // try 11 delay: 61.31s
        let backoffFactor = 1.9
        let maxBackoff = 15 * kMinuteInterval

        let seconds = 0.1 * min(maxBackoff, pow(backoffFactor, Double(self.jobRecord.failureCount)))
        return seconds
    }

    override public func didFail(error: Error) {
        databaseStorage.write { transaction in
            self.durableOperationDelegate?.durableOperation(self, didFailWithError: error, transaction: transaction)

            self.message.update(sendingError: error, transaction: transaction)

            if self.jobRecord.removeMessageAfterSending {
                self.message.anyRemove(transaction: transaction)
            }
        }
    }
}