import PromiseKit
import SessionSnodeKit

extension OpenGroupAPI {
    public final class Poller {
        private let server: String
        private var timer: Timer? = nil
        private var hasStarted = false
        private var isPolling = false

        // MARK: - Settings
        
        internal static let maxInactivityPeriod: Double = (14 * 24 * 60 * 60)
        private static let pollInterval: TimeInterval = 4
        
        // MARK: - Lifecycle
        
        public init(for server: String) {
            self.server = server
        }

        @objc public func startIfNeeded() {
            guard !hasStarted else { return }
            
            DispatchQueue.main.async { [weak self] in // Timers don't do well on background queues
                self?.hasStarted = true
                self?.timer = Timer.scheduledTimer(withTimeInterval: Poller.pollInterval, repeats: true) { _ in
                    DispatchQueue.global().async {
                        self?.poll().retainUntilComplete()
                    }
                }
                DispatchQueue.global().async {
                    self?.poll().retainUntilComplete()
                }
            }
        }

        @objc public func stop() {
            timer?.invalidate()
            hasStarted = false
        }

        // MARK: - Polling
        
        @discardableResult
        public func poll() -> Promise<Void> {
            return poll(isBackgroundPoll: false)
        }

        @discardableResult
        public func poll(isBackgroundPoll: Bool) -> Promise<Void> {
            guard !self.isPolling else { return Promise.value(()) }
            
            self.isPolling = true
            let (promise, seal) = Promise<Void>.pending()
            promise.retainUntilComplete()
            
            OpenGroupAPI.poll(server)
                .done(on: OpenGroupAPI.workQueue) { [weak self] response in
                    self?.isPolling = false
                    self?.handlePollResponse(response, isBackgroundPoll: isBackgroundPoll)
                    seal.fulfill(())
                }
                .catch(on: OpenGroupAPI.workQueue) { [weak self] error in
                    SNLog("Open group polling failed due to error: \(error).")
                    self?.isPolling = false
                    seal.fulfill(()) // The promise is just used to keep track of when we're done
                }
    //        OpenGroupAPI.compactPoll(server)
    //        OpenGroupAPI.legacyCompactPoll(server)
    //            .done(on: OpenGroupAPI.workQueue) { [weak self] response in
    //                guard let self = self else { return }
    //                self.isPolling = false
    //                response.results.forEach { self.handleCompactPollBody($0, isBackgroundPoll: isBackgroundPoll) }
    //                seal.fulfill(())
    //            }
    //            .catch(on: OpenGroupAPI.workQueue) { error in
    //                SNLog("Open group polling failed due to error: \(error).")
    //                self.isPolling = false
    //                seal.fulfill(()) // The promise is just used to keep track of when we're done
    //            }
            
            return promise
        }
        
        private func handlePollResponse(_ response: [OpenGroupAPI.Endpoint: (info: OnionRequestResponseInfoType, data: Codable?)], isBackgroundPoll: Bool) {
            response.forEach { endpoint, endpointResponse in
                switch endpoint {
                    case .capabilities:
                        guard let responseData: BatchSubResponse<Capabilities> = endpointResponse.data as? BatchSubResponse<Capabilities>, let responseBody: Capabilities = responseData.body else {
                            SNLog("Open group polling failed due to invalid data.")
                            return
                        }
                        
                        OpenGroupManager.handleCapabilities(
                            responseBody,
                            on: server
                        )
                        
                    case .roomMessagesRecent(let roomToken), .roomMessagesBefore(let roomToken, _), .roomMessagesSince(let roomToken, _):
                        guard let responseData: BatchSubResponse<[Message]> = endpointResponse.data as? BatchSubResponse<[Message]>, let responseBody: [Message] = responseData.body else {
                            SNLog("Open group polling failed due to invalid data.")
                            return
                        }
                        
                        OpenGroupManager.handleMessages(
                            responseBody,
                            for: roomToken,
                            on: server,
                            isBackgroundPoll: isBackgroundPoll
                        )
                        
                    case .roomPollInfo(let roomToken, _):
                        guard let responseData: BatchSubResponse<RoomPollInfo> = endpointResponse.data as? BatchSubResponse<RoomPollInfo>, let responseBody: RoomPollInfo = responseData.body else {
                            SNLog("Open group polling failed due to invalid data.")
                            return
                        }
                        
                        OpenGroupManager.handlePollInfo(
                            responseBody,
                            publicKey: nil,
                            for: roomToken,
                            on: server
                        )
                        
                    case .inbox, .inboxSince:
                        guard let responseData: BatchSubResponse<[DirectMessage]?> = endpointResponse.data as? BatchSubResponse<[DirectMessage]?>, let responseBody: [DirectMessage]? = responseData.body else {
                            SNLog("Open group polling failed due to invalid data.")
                            return
                        }
                        
                        OpenGroupManager.handleInbox(
                            (responseBody ?? []),
                            on: server,
                            isBackgroundPoll: isBackgroundPoll
                        )
                        
                    default: break // No custom handling needed
                }
            }
        }
        
        // MARK: - Legacy Handling

        private func handleCompactPollBody(_ body: OpenGroupAPI.LegacyCompactPollResponse.Result, isBackgroundPoll: Bool) {
            let storage = SNMessagingKitConfiguration.shared.storage
            // - Messages
            // Sorting the messages by server ID before importing them fixes an issue where messages that quote older messages can't find those older messages
            let openGroupID = "\(server).\(body.room)"
            let messages = (body.messages ?? []).sorted { ($0.serverID ?? 0) < ($1.serverID ?? 0) }
            
            storage.write { transaction in
                messages.forEach { message in
                    guard let data = Data(base64Encoded: message.base64EncodedData) else {
                        return SNLog("Ignoring open group message with invalid encoding.")
                    }
                    let envelope = SNProtoEnvelope.builder(type: .sessionMessage, timestamp: message.sentTimestamp)
                    envelope.setContent(data)
                    envelope.setSource(message.sender!) // Safe because messages with a nil sender are filtered out
                    do {
                        let data = try envelope.buildSerializedData()
                        let (message, proto) = try MessageReceiver.parse(data, openGroupMessageServerID: UInt64(message.serverID!), isRetry: false, using: transaction)
                        try MessageReceiver.handle(message, associatedWithProto: proto, openGroupID: openGroupID, isBackgroundPoll: isBackgroundPoll, using: transaction)
                    } catch {
                        SNLog("Couldn't receive open group message due to error: \(error).")
                    }
                }
            }
            
            // - Moderators
            if var x = OpenGroupAPI.moderators[server] {
                x[body.room] = Set(body.moderators ?? [])
                OpenGroupAPI.moderators[server] = x
            }
            else {
                OpenGroupAPI.moderators[server] = [ body.room : Set(body.moderators ?? []) ]
            }
            
            // - Deletions
            let deletedMessageServerIDs = Set((body.deletions ?? []).map { UInt64($0.deletedMessageID) })
            storage.write { transaction in
                let transaction = transaction as! YapDatabaseReadWriteTransaction
                guard let threadID = storage.getThreadID(for: openGroupID),
                    let thread = TSGroupThread.fetch(uniqueId: threadID, transaction: transaction) else { return }
                var messagesToRemove: [TSMessage] = []
                
                thread.enumerateInteractions(with: transaction) { interaction, stop in
                    guard let message = interaction as? TSMessage, deletedMessageServerIDs.contains(message.openGroupServerMessageID) else { return }
                    messagesToRemove.append(message)
                }
                
                messagesToRemove.forEach { $0.remove(with: transaction) }
            }
        }
    }
}