import Foundation
import Postbox
import TelegramCore
import SwiftSignalKit

private enum CurrentCall {
    case none
    case incomingRinging(CallSessionRingingState)
    case ongoing(CallSession, OngoingCallContext)
    
    var internalId: CallSessionInternalId? {
        switch self {
            case .none:
                return nil
            case let .incomingRinging(ringingState):
                return ringingState.id
            case let .ongoing(session, _):
                return session.id
        }
    }
}

public enum RequestCallResult {
    case requested
    case alreadyInProgress(PeerId)
}

public final class PresentationCallManager {
    private let postbox: Postbox
    private let audioSession: ManagedAudioSession
    private let callSessionManager: CallSessionManager
    private let callKitIntegration: CallKitIntegration?
    
    private var currentCall: PresentationCall?
    private let removeCurrentCallDisposable = MetaDisposable()
    
    private var ringingStatesDisposable: Disposable?
    
    private let hasActiveCallsPromise = ValuePromise<Bool>(false, ignoreRepeated: true)
    public var hasActiveCalls: Signal<Bool, NoError> {
        return self.hasActiveCallsPromise.get()
    }
    
    private let currentCallPromise = Promise<PresentationCall?>(nil)
    public var currentCallSignal: Signal<PresentationCall?, NoError> {
        return self.currentCallPromise.get()
    }
    
    private let startCallDisposable = MetaDisposable()
    
    public init(postbox: Postbox, audioSession: ManagedAudioSession, callSessionManager: CallSessionManager) {
        self.postbox = postbox
        self.audioSession = audioSession
        self.callSessionManager = callSessionManager
        
        var startCallImpl: ((UUID, String) -> Signal<Bool, NoError>)?
        var answerCallImpl: ((UUID) -> Void)?
        var endCallImpl: ((UUID) -> Signal<Bool, NoError>)?
        var audioSessionActivationChangedImpl: ((Bool) -> Void)?
        
        self.callKitIntegration = CallKitIntegration(startCall: { uuid, handle in
            if let startCallImpl = startCallImpl {
                return startCallImpl(uuid, handle)
            } else {
                return .single(false)
            }
        }, answerCall: { uuid in
            answerCallImpl?(uuid)
        }, endCall: { uuid in
            if let endCallImpl = endCallImpl {
                return endCallImpl(uuid)
            } else {
                return .single(false)
            }
        }, audioSessionActivationChanged: { value in
            audioSessionActivationChangedImpl?(value)
        })
        
        self.ringingStatesDisposable = (callSessionManager.ringingStates() |> mapToSignal { ringingStates -> Signal<[(Peer, CallSessionRingingState)], NoError> in
                if ringingStates.isEmpty {
                    return .single([])
                } else {
                    return postbox.modify { modifier -> [(Peer, CallSessionRingingState)] in
                        var result: [(Peer, CallSessionRingingState)] = []
                        for state in ringingStates {
                            if let peer = modifier.getPeer(state.peerId) {
                                result.append((peer, state))
                            }
                        }
                        return result
                    }
                }
            }
            |> deliverOnMainQueue).start(next: { [weak self] ringingStates in
                self?.ringingStatesUpdated(ringingStates)
            })
        
        startCallImpl = { [weak self] uuid, handle in
            if let strongSelf = self, let userId = Int32(handle) {
                return strongSelf.startCall(peerId: PeerId(namespace: Namespaces.Peer.CloudUser, id: userId), internalId: uuid)
                    |> take(1)
                    |> map { _ -> Bool in
                        return true
                    }
            } else {
                return .single(false)
            }
        }
        
        answerCallImpl = { [weak self] uuid in
            if let strongSelf = self {
                strongSelf.currentCall?.answer()
            }
        }
        
        endCallImpl = { [weak self] uuid in
            if let strongSelf = self, let currentCall = strongSelf.currentCall {
                return currentCall.hangUp()
            } else {
                return .single(false)
            }
        }
        
        audioSessionActivationChangedImpl = { [weak self] value in
            if value {
                self?.audioSession.callKitActivatedAudioSession()
            } else {
                self?.audioSession.callKitDeactivatedAudioSession()
            }
        }
    }
    
    deinit {
        self.ringingStatesDisposable?.dispose()
        self.removeCurrentCallDisposable.dispose()
        self.startCallDisposable.dispose()
    }
    
    private func ringingStatesUpdated(_ ringingStates: [(Peer, CallSessionRingingState)]) {
        if let firstState = ringingStates.first {
            if self.currentCall == nil {
                let call = PresentationCall(audioSession: self.audioSession, callSessionManager: self.callSessionManager, callKitIntegration: self.callKitIntegration, internalId: firstState.1.id, peerId: firstState.1.peerId, isOutgoing: false, peer: firstState.0)
                self.currentCall = call
                self.currentCallPromise.set(.single(call))
                self.hasActiveCallsPromise.set(true)
                self.removeCurrentCallDisposable.set((call.canBeRemoved
                    |> deliverOnMainQueue).start(next: { [weak self, weak call] value in
                        if value, let strongSelf = self, let call = call {
                            if strongSelf.currentCall === call {
                                strongSelf.currentCall = nil
                                strongSelf.currentCallPromise.set(.single(nil))
                                strongSelf.hasActiveCallsPromise.set(false)
                            }
                        }
                    }))
            }
        }
    }
    
    public func requestCall(peerId: PeerId, endCurrentIfAny: Bool) -> RequestCallResult {
        if let call = self.currentCall, !endCurrentIfAny {
            return .alreadyInProgress(call.peerId)
        }
        if let _ = self.callKitIntegration {
            startCallDisposable.set((postbox.loadedPeerWithId(peerId)
                |> take(1)
                |> deliverOnMainQueue).start(next: { [weak self] peer in
                    if let strongSelf = self {
                        strongSelf.callKitIntegration?.startCall(peerId: peerId, displayTitle: peer.displayTitle)
                    }
                }))
        } else {
            let _ = self.startCall(peerId: peerId).start()
        }
        return .requested
    }
    
    private func startCall(peerId: PeerId, internalId: CallSessionInternalId = CallSessionInternalId()) -> Signal<Bool, NoError> {
        return (self.callSessionManager.request(peerId: peerId, internalId: internalId) |> deliverOnMainQueue |> beforeNext { [weak self] internalId in
            if let strongSelf = self {
                if let currentCall = strongSelf.currentCall {
                    currentCall.rejectBusy()
                }
                let call = PresentationCall(audioSession: strongSelf.audioSession, callSessionManager: strongSelf.callSessionManager, callKitIntegration: strongSelf.callKitIntegration, internalId: internalId, peerId: peerId, isOutgoing: true, peer: nil)
                strongSelf.currentCall = call
                strongSelf.currentCallPromise.set(.single(call))
                strongSelf.hasActiveCallsPromise.set(true)
                strongSelf.removeCurrentCallDisposable.set((call.canBeRemoved
                    |> deliverOnMainQueue).start(next: { [weak call] value in
                        if value, let strongSelf = self, let call = call {
                            if strongSelf.currentCall === call {
                                strongSelf.currentCall = nil
                                strongSelf.currentCallPromise.set(.single(nil))
                                strongSelf.hasActiveCallsPromise.set(false)
                            }
                        }
                    }))

            }
        }) |> mapToSignal { _ -> Signal<Bool, NoError> in return .single(true) }
    }
}