import Foundation
import SwiftSignalKit
import Postbox
import TelegramApi
import MtProtoKit
import SyncCore

public struct MessageStats: Equatable {
    public let views: Int
    public let forwards: Int
    public let interactionsGraph: StatsGraph
    public let detailedInteractionsGraph: StatsGraph?
    
    init(views: Int, forwards: Int, interactionsGraph: StatsGraph, detailedInteractionsGraph: StatsGraph?) {
        self.views = views
        self.forwards = forwards
        self.interactionsGraph = interactionsGraph
        self.detailedInteractionsGraph = detailedInteractionsGraph
    }
    
    public static func == (lhs: MessageStats, rhs: MessageStats) -> Bool {
        if lhs.views != rhs.views {
            return false
        }
        if lhs.forwards != rhs.forwards {
            return false
        }
        if lhs.interactionsGraph != rhs.interactionsGraph {
            return false
        }
        if lhs.detailedInteractionsGraph != rhs.detailedInteractionsGraph {
            return false
        }
        return true
    }
    
    public func withUpdatedInteractionsGraph(_ interactionsGraph: StatsGraph) -> MessageStats {
        return MessageStats(views: self.views, forwards: self.forwards, interactionsGraph: interactionsGraph, detailedInteractionsGraph: self.detailedInteractionsGraph)
    }
}

public struct MessageStatsContextState: Equatable {
    public var stats: MessageStats?
}

private func requestMessageStats(postbox: Postbox, network: Network, datacenterId: Int32, messageId: MessageId, dark: Bool = false) -> Signal<MessageStats?, NoError> {
    return postbox.transaction { transaction -> (Peer, Message)? in
        if let peer = transaction.getPeer(messageId.peerId), let message = transaction.getMessage(messageId) {
            return (peer, message)
        } else {
            return nil
        }
    } |> mapToSignal { peerAndMessage -> Signal<MessageStats?, NoError> in
        guard let (peer, message) = peerAndMessage, let inputChannel = apiInputChannel(peer) else {
            return .never()
        }
        
        var flags: Int32 = 0
        if dark {
            flags |= (1 << 1)
        }
        
        let request = Api.functions.stats.getMessageStats(flags: flags, channel: inputChannel, msgId: messageId.id)
        let signal: Signal<Api.stats.MessageStats, MTRpcError>
        if network.datacenterId != datacenterId {
            signal = network.download(datacenterId: Int(datacenterId), isMedia: false, tag: nil)
            |> castError(MTRpcError.self)
            |> mapToSignal { worker in
                return worker.request(request)
            }
        } else {
            signal = network.request(request)
        }
        
        var views: Int = 0
        var forwards: Int = 0
        for attribute in message.attributes {
            if let viewsAttribute = attribute as? ViewCountMessageAttribute {
                views = viewsAttribute.count
            } else if let forwardsAttribute = attribute as? ForwardCountMessageAttribute {
                forwards = forwardsAttribute.count
            }
        }
        
        return signal
        |> mapToSignal { result -> Signal<MessageStats?, MTRpcError> in
            if case let .messageStats(apiViewsGraph) = result {
                let interactionsGraph = StatsGraph(apiStatsGraph: apiViewsGraph)
                let timestamp = Int32(CFAbsoluteTimeGetCurrent() + NSTimeIntervalSince1970)
                if case let .Loaded(tokenValue, _) = interactionsGraph, let token = tokenValue, Int64(message.timestamp + 60 * 60 * 24 * 2) > Int64(timestamp) {
                    return requestGraph(network: network, datacenterId: datacenterId, token: token, x: 1601596800000)
                    |> castError(MTRpcError.self)
                    |> map { detailedGraph -> MessageStats? in
                        return MessageStats(views: views, forwards: forwards, interactionsGraph: interactionsGraph, detailedInteractionsGraph: detailedGraph)
                    }
                } else {
                    return .single(MessageStats(views: views, forwards: forwards, interactionsGraph: interactionsGraph, detailedInteractionsGraph: nil))
                }
            } else {
                return .single(nil)
            }
        }
        |> retryRequest
    }
}

private final class MessageStatsContextImpl {
    private let postbox: Postbox
    private let network: Network
    private let datacenterId: Int32
    private let messageId: MessageId
    
    private var _state: MessageStatsContextState {
        didSet {
            if self._state != oldValue {
                self._statePromise.set(.single(self._state))
            }
        }
    }
    private let _statePromise = Promise<MessageStatsContextState>()
    var state: Signal<MessageStatsContextState, NoError> {
        return self._statePromise.get()
    }
    
    private let disposable = MetaDisposable()
    private let disposables = DisposableDict<String>()
    
    init(postbox: Postbox, network: Network, datacenterId: Int32, messageId: MessageId) {
        assert(Queue.mainQueue().isCurrent())
        
        self.postbox = postbox
        self.network = network
        self.datacenterId = datacenterId
        self.messageId = messageId
        self._state = MessageStatsContextState(stats: nil)
        self._statePromise.set(.single(self._state))
        
        self.load()
    }
    
    deinit {
        assert(Queue.mainQueue().isCurrent())
        self.disposable.dispose()
        self.disposables.dispose()
    }
    
    private func load() {
        assert(Queue.mainQueue().isCurrent())
        
        self.disposable.set((requestMessageStats(postbox: self.postbox, network: self.network, datacenterId: self.datacenterId, messageId: self.messageId)
        |> deliverOnMainQueue).start(next: { [weak self] stats in
            if let strongSelf = self {
                strongSelf._state = MessageStatsContextState(stats: stats)
                strongSelf._statePromise.set(.single(strongSelf._state))
            }
        }))
    }
    
    func loadDetailedGraph(_ graph: StatsGraph, x: Int64) -> Signal<StatsGraph?, NoError> {
        if let token = graph.token {
            return requestGraph(network: self.network, datacenterId: self.datacenterId, token: token, x: x)
        } else {
            return .single(nil)
        }
    }
}

public final class MessageStatsContext {
    private let impl: QueueLocalObject<MessageStatsContextImpl>
    
    public var state: Signal<MessageStatsContextState, NoError> {
        return Signal { subscriber in
            let disposable = MetaDisposable()
            self.impl.with { impl in
                disposable.set(impl.state.start(next: { value in
                    subscriber.putNext(value)
                }))
            }
            return disposable
        }
    }
    
    public init(postbox: Postbox, network: Network, datacenterId: Int32, messageId: MessageId) {
        self.impl = QueueLocalObject(queue: Queue.mainQueue(), generate: {
            return MessageStatsContextImpl(postbox: postbox, network: network, datacenterId: datacenterId, messageId: messageId)
        })
    }
        
    public func loadDetailedGraph(_ graph: StatsGraph, x: Int64) -> Signal<StatsGraph?, NoError> {
        return Signal { subscriber in
            let disposable = MetaDisposable()
            self.impl.with { impl in
                disposable.set(impl.loadDetailedGraph(graph, x: x).start(next: { value in
                    subscriber.putNext(value)
                    subscriber.putCompletion()
                }))
            }
            return disposable
        }
    }
}