import Foundation
#if os(macOS)
    import PostboxMac
    import SwiftSignalKitMac
#else
    import Postbox
    import SwiftSignalKit
#endif

public struct PendingMessageStatus: Equatable {
    public let progress: Float
    
    public static func ==(lhs: PendingMessageStatus, rhs: PendingMessageStatus) -> Bool {
        return lhs.progress.isEqual(to: rhs.progress)
    }
}

private final class PendingMessageContext {
    var disposable: MetaDisposable?
    var status: PendingMessageStatus?
    var statusSubscribers = Bag<(PendingMessageStatus?) -> Void>()
}

private final class PeerPendingMessagesSummaryContext {
    var messageDeliveredSubscribers = Bag<(Void) -> Void>()
}

private enum PendingMessageResult {
    case progress(Float)
}

private final class PendingMessageRequestDependencyTag: NetworkRequestDependencyTag {
    let messageId: MessageId
    
    init(messageId: MessageId) {
        self.messageId = messageId
    }
    
    func shouldDependOn(other: NetworkRequestDependencyTag) -> Bool {
        if let other = other as? PendingMessageRequestDependencyTag, self.messageId.peerId == other.messageId.peerId && self.messageId.namespace == other.messageId.namespace {
            return self.messageId.id > other.messageId.id
        }
        return false
    }
}

public final class PendingMessageManager {
    private let network: Network
    private let postbox: Postbox
    private let stateManager: StateManager
    
    private let queue = Queue()
    
    private var messageContexts: [MessageId: PendingMessageContext] = [:]
    private var pendingMessageIds = Set<MessageId>()
    private let beginSendingMessagesDisposables = DisposableSet()
    
    private var peerSummaryContexts: [PeerId: PeerPendingMessagesSummaryContext] = [:]
    
    init(network: Network, postbox: Postbox, stateManager: StateManager) {
        self.network = network
        self.postbox = postbox
        self.stateManager = stateManager
    }
    
    deinit {
        self.beginSendingMessagesDisposables.dispose()
    }
    
    func updatePendingMessageIds(_ messageIds: Set<MessageId>) {
        self.queue.async {
            let addedMessageIds = messageIds.subtracting(self.pendingMessageIds)
            let removedMessageIds = self.pendingMessageIds.subtracting(messageIds)
            
            for id in removedMessageIds {
                if let context = self.messageContexts[id] {
                    context.disposable?.dispose()
                    context.disposable = nil
                    if context.statusSubscribers.isEmpty {
                        self.messageContexts.removeValue(forKey: id)
                    }
                }
            }
            
            if !addedMessageIds.isEmpty {
                self.beginSendingMessages(Array(addedMessageIds).sorted())
            }
            
            self.pendingMessageIds = messageIds
        }
    }
    
    public func pendingMessageStatus(_ id: MessageId) -> Signal<PendingMessageStatus?, NoError> {
        return Signal { subscriber in
            let disposable = MetaDisposable()
            
            self.queue.async {
                let messageContext: PendingMessageContext
                if let current = self.messageContexts[id] {
                    messageContext = current
                } else {
                    messageContext = PendingMessageContext()
                    messageContext.disposable = MetaDisposable()
                    self.messageContexts[id] = messageContext
                }
                
                let index = messageContext.statusSubscribers.add({ status in
                    subscriber.putNext(status)
                })
                
                subscriber.putNext(messageContext.status)
                
                disposable.set(ActionDisposable {
                    self.queue.async {
                        if let current = self.messageContexts[id] {
                            current.statusSubscribers.remove(index)
                            if current.statusSubscribers.isEmpty && current.disposable == nil {
                                self.messageContexts.removeValue(forKey: id)
                            }
                        }
                    }
                })
            }
            
            return disposable
        }
    }
    
    private func beginSendingMessages(_ ids: [MessageId]) {
        assert(self.queue.isCurrent())
        
        for id in ids {
            let messageContext: PendingMessageContext
            if let current = self.messageContexts[id] {
                messageContext = current
            } else {
                messageContext = PendingMessageContext()
                messageContext.disposable = MetaDisposable()
                self.messageContexts[id] = messageContext
            }
            
            let status = PendingMessageStatus(progress: 0.0)
            if status != messageContext.status {
                messageContext.status = status
                for subscriber in messageContext.statusSubscribers.copyItems() {
                    subscriber(status)
                }
            }
        }
        
        let disposable = MetaDisposable()
        let messages = self.postbox.messagesAtIds(ids)
            |> deliverOn(self.queue)
            |> afterDisposed { [weak self, weak disposable] in
                if let strongSelf = self, let strongDisposable = disposable {
                    strongSelf.beginSendingMessagesDisposables.remove(strongDisposable)
                }
            }
        self.beginSendingMessagesDisposables.add(disposable)
        disposable.set(messages.start(next: { [weak self] messages in
            if let strongSelf = self {
                assert(strongSelf.queue.isCurrent())
                
                for message in messages {
                    guard let peer = message.peers[message.id.peerId], let messageContext = strongSelf.messageContexts[message.id] else {
                        continue
                    }
                    
                    let uploadedContent = uploadedMessageContent(network: strongSelf.network, postbox: strongSelf.postbox, message: message)
                    
                    let sendMessage = uploadedContent
                        |> mapToSignal { contentResult -> Signal<PendingMessageResult, NoError> in
                            if let strongSelf = self {
                                switch contentResult {
                                    case let .progress(progress):
                                        return .single(.progress(progress))
                                    case let .content(message, content):
                                        return strongSelf.sendMessageContent(network: strongSelf.network, postbox: strongSelf.postbox, stateManager: strongSelf.stateManager, message: message, content: content)
                                            |> map { next -> PendingMessageResult in
                                                return .progress(1.0)
                                            }
                                }
                            } else {
                                return .complete()
                            }
                    }
                    
                    messageContext.disposable?.set((sendMessage |> deliverOn(strongSelf.queue) |> afterDisposed {
                        if let strongSelf = self {
                            assert(strongSelf.queue.isCurrent())
                            if let current = strongSelf.messageContexts[message.id] {
                                current.disposable = nil
                                for subscriber in current.statusSubscribers.copyItems() {
                                    subscriber(nil)
                                }
                                if current.statusSubscribers.isEmpty {
                                    strongSelf.messageContexts.removeValue(forKey: message.id)
                                }
                            }
                        }
                    }).start(next: { next in
                        if let strongSelf = self {
                            assert(strongSelf.queue.isCurrent())
                            
                            switch next {
                                case let .progress(progress):
                                    if let current = strongSelf.messageContexts[message.id] {
                                        let status = PendingMessageStatus(progress: progress)
                                        current.status = status
                                        for subscriber in current.statusSubscribers.copyItems() {
                                            subscriber(status)
                                        }
                                    }
                            }
                        }
                    }))
                }
            }
        }))
    }
    
    private func sendMessageContent(network: Network, postbox: Postbox, stateManager: StateManager, message: Message, content: PendingMessageUploadedContent) -> Signal<Void, NoError> {
        return postbox.modify { [weak self] modifier -> Signal<Void, NoError> in
            if let peer = modifier.getPeer(message.id.peerId), let inputPeer = apiInputPeer(peer) {
                var uniqueId: Int64 = 0
                var forwardSourceInfoAttribute: ForwardSourceInfoAttribute?
                var replyMessageId: Int32?
                
                for attribute in message.attributes {
                    if let replyAttribute = attribute as? ReplyMessageAttribute {
                        replyMessageId = replyAttribute.messageId.id
                    } else if let outgoingInfo = attribute as? OutgoingMessageInfoAttribute {
                        uniqueId = outgoingInfo.uniqueId
                    } else if let forwardSourceInfo = attribute as? ForwardSourceInfoAttribute {
                        forwardSourceInfoAttribute = forwardSourceInfo
                    }
                }
                
                var flags: Int32 = 0
                if let replyMessageId = replyMessageId {
                    flags |= Int32(1 << 0)
                }
                
                let dependencyTag = PendingMessageRequestDependencyTag(messageId: message.id)
                
                let sendMessageRequest: Signal<Api.Updates, NoError>
                switch content {
                case let .text(text):
                    sendMessageRequest = network.request(Api.functions.messages.sendMessage(flags: flags, peer: inputPeer, replyToMsgId: replyMessageId, message: message.text, randomId: uniqueId, replyMarkup: nil, entities: nil), tag: dependencyTag)
                        |> mapError { _ -> NoError in
                            return NoError()
                        }
                case let .media(inputMedia):
                    sendMessageRequest = network.request(Api.functions.messages.sendMedia(flags: 0, peer: inputPeer, replyToMsgId: replyMessageId, media: inputMedia, randomId: uniqueId, replyMarkup: nil), tag: dependencyTag)
                        |> mapError { _ -> NoError in
                            return NoError()
                        }
                case let .forward(sourceInfo):
                    if let forwardSourceInfoAttribute = forwardSourceInfoAttribute, let sourcePeer = modifier.getPeer(forwardSourceInfoAttribute.messageId.peerId), let sourceInputPeer = apiInputPeer(sourcePeer) {
                        sendMessageRequest = network.request(Api.functions.messages.forwardMessages(flags: 0, fromPeer: sourceInputPeer, id: [sourceInfo.messageId.id], randomId: [uniqueId], toPeer: inputPeer), tag: dependencyTag)
                            |> mapError { _ -> NoError in
                                return NoError()
                            }
                    } else {
                        sendMessageRequest = .fail(NoError())
                    }
                }
                
                return sendMessageRequest
                    |> mapToSignal { result -> Signal<Void, NoError> in
                        if let strongSelf = self {
                            return strongSelf.applySentMessage(postbox: postbox, stateManager: stateManager, message: message, result: result)
                        } else {
                            return .never()
                        }
                    }
                    |> `catch` { _ -> Signal<Void, NoError> in
                        let modify = postbox.modify { modifier -> Void in
                            modifier.updateMessage(message.id, update: { currentMessage in
                                var storeForwardInfo: StoreMessageForwardInfo?
                                if let forwardInfo = currentMessage.forwardInfo {
                                    storeForwardInfo = StoreMessageForwardInfo(authorId: forwardInfo.author.id, sourceId: forwardInfo.source?.id, sourceMessageId: forwardInfo.sourceMessageId, date: forwardInfo.date)
                                }
                                return StoreMessage(id: message.id, timestamp: currentMessage.timestamp, flags: [.Failed], tags: currentMessage.tags, forwardInfo: storeForwardInfo, authorId: currentMessage.author?.id, text: currentMessage.text, attributes: currentMessage.attributes, media: currentMessage.media)
                            })
                        }
                        
                        return modify
                }
            } else {
                return .complete()
            }
        } |> switchToLatest
    }
    
    private func applySentMessage(postbox: Postbox, stateManager: StateManager, message: Message, result: Api.Updates) -> Signal<Void, NoError> {
        let messageId = result.rawMessageIds.first
        let apiMessage = result.messages.first
        
        return applyUpdateMessage(postbox: postbox, stateManager: stateManager, message: message, result: result) |> afterDisposed { [weak self] in
            if let strongSelf = self {
                strongSelf.queue.async {
                    if let context = strongSelf.peerSummaryContexts[message.id.peerId] {
                        for subscriber in context.messageDeliveredSubscribers.copyItems() {
                            subscriber(Void())
                        }
                    }
                }
            }
        }
    }
    
    public func deliveredMessageEvents(peerId: PeerId) -> Signal<Bool, NoError> {
        return Signal { subscriber in
            let disposable = MetaDisposable()
            
            self.queue.async {
                let summaryContext: PeerPendingMessagesSummaryContext
                if let current = self.peerSummaryContexts[peerId] {
                    summaryContext = current
                } else {
                    summaryContext = PeerPendingMessagesSummaryContext()
                    self.peerSummaryContexts[peerId] = summaryContext
                }
                
                let index = summaryContext.messageDeliveredSubscribers.add({ _ in
                    subscriber.putNext(true)
                })
                
                disposable.set(ActionDisposable {
                    self.queue.async {
                        if let current = self.peerSummaryContexts[peerId] {
                            current.messageDeliveredSubscribers.remove(index)
                            if current.messageDeliveredSubscribers.isEmpty {
                                self.peerSummaryContexts.removeValue(forKey: peerId)
                            }
                        }
                    }
                })
            }
            
            return disposable
        }
    }
}