import Postbox
import SwiftSignalKit
import TelegramApi

public final class MessageReadStats {
    public let peers: [EnginePeer]

    public init(peers: [EnginePeer]) {
        self.peers = peers
    }
}

func _internal_messageReadStats(account: Account, id: MessageId) -> Signal<MessageReadStats?, NoError> {
    return account.postbox.transaction { transaction -> Api.InputPeer? in
        return transaction.getPeer(id.peerId).flatMap(apiInputPeer)
    }
    |> mapToSignal { inputPeer -> Signal<MessageReadStats?, NoError> in
        guard let inputPeer = inputPeer else {
            return .single(nil)
        }
        if id.namespace != Namespaces.Message.Cloud {
            return .single(nil)
        }

        return account.network.request(Api.functions.messages.getMessageReadParticipants(peer: inputPeer, msgId: id.id))
        |> map(Optional.init)
        |> `catch` { _ -> Signal<[Int64]?, NoError> in
            return .single(nil)
        }
        |> mapToSignal { result -> Signal<MessageReadStats?, NoError> in
            guard let result = result else {
                return .single(nil)
            }
            return account.postbox.transaction { transaction -> (peerIds: [PeerId], missingPeerIds: [PeerId]) in
                var peerIds: [PeerId] = []
                var missingPeerIds: [PeerId] = []

                let authorId = transaction.getMessage(id)?.author?.id

                for id in result {
                    let peerId = PeerId(namespace: Namespaces.Peer.CloudUser, id: PeerId.Id._internalFromInt64Value(id))
                    if peerId == account.peerId {
                        continue
                    }
                    if peerId == authorId {
                        continue
                    }
                    peerIds.append(peerId)
                    if transaction.getPeer(peerId) == nil {
                        missingPeerIds.append(peerId)
                    }
                }

                return (peerIds: peerIds, missingPeerIds: missingPeerIds)
            }
            |> mapToSignal { peerIds, missingPeerIds -> Signal<MessageReadStats?, NoError> in
                if missingPeerIds.isEmpty || id.peerId.namespace != Namespaces.Peer.CloudChannel {
                    return account.postbox.transaction { transaction -> MessageReadStats? in
                        return MessageReadStats(peers: peerIds.compactMap { peerId -> EnginePeer? in
                            return transaction.getPeer(peerId).flatMap(EnginePeer.init)
                        })
                    }
                } else {
                    return _internal_channelMembers(postbox: account.postbox, network: account.network, accountPeerId: account.peerId, peerId: id.peerId, category: .recent(.all), offset: 0, limit: 50, hash: 0)
                    |> mapToSignal { _ -> Signal<MessageReadStats?, NoError> in
                        return account.postbox.transaction { transaction -> MessageReadStats? in
                            return MessageReadStats(peers: peerIds.compactMap { peerId -> EnginePeer? in
                                return transaction.getPeer(peerId).flatMap(EnginePeer.init)
                            })
                        }
                    }
                }
            }
        }
    }
}