//
//  Copyright (c) 2020 Open Whisper Systems. All rights reserved.
//

import UIKit
import CallKit
import SignalServiceKit

/**
 * Requests actions from CallKit
 *
 * @Discussion:
 *   Based on SpeakerboxCallManager, from the Apple CallKit Example app. Though, it's responsibilities are mostly 
 *   mirrored (and delegated from) CallKitCallUIAdaptee.
 *   TODO: Would it simplify things to merge this into CallKitCallUIAdaptee?
 */
final class CallKitCallManager: NSObject {

    let callController = CXCallController()
    let showNamesOnCallScreen: Bool

    @objc
    static let kAnonymousCallHandlePrefix = "Signal:"

    required init(showNamesOnCallScreen: Bool) {
        AssertIsOnMainThread()

        self.showNamesOnCallScreen = showNamesOnCallScreen
        super.init()

        // We cannot assert singleton here, because this class gets rebuilt when the user changes relevant call settings
    }

    // MARK: Actions

    func startCall(_ call: SignalCall) {
        let handle: CXHandle

        if showNamesOnCallScreen {
            let type: CXHandle.HandleType
            let value: String
            if let phoneNumber = call.individualCall.remoteAddress.phoneNumber {
                type = .phoneNumber
                value = phoneNumber
            } else {
                type = .generic
                value = call.individualCall.remoteAddress.stringForDisplay
            }
            handle = CXHandle(type: type, value: value)
        } else {
            let callKitId = CallKitCallManager.kAnonymousCallHandlePrefix + call.individualCall.localId.uuidString
            handle = CXHandle(type: .generic, value: callKitId)
            CallKitIdStore.setAddress(call.individualCall.remoteAddress, forCallKitId: callKitId)
        }

        let startCallAction = CXStartCallAction(call: call.individualCall.localId, handle: handle)

        startCallAction.isVideo = call.individualCall.hasLocalVideo

        let transaction = CXTransaction()
        transaction.addAction(startCallAction)

        requestTransaction(transaction)
    }

    func localHangup(call: SignalCall) {
        let endCallAction = CXEndCallAction(call: call.individualCall.localId)
        let transaction = CXTransaction()
        transaction.addAction(endCallAction)

        requestTransaction(transaction)
    }

    func setHeld(call: SignalCall, onHold: Bool) {
        let setHeldCallAction = CXSetHeldCallAction(call: call.individualCall.localId, onHold: onHold)
        let transaction = CXTransaction()
        transaction.addAction(setHeldCallAction)

        requestTransaction(transaction)
    }

    func setIsMuted(call: SignalCall, isMuted: Bool) {
        let muteCallAction = CXSetMutedCallAction(call: call.individualCall.localId, muted: isMuted)
        let transaction = CXTransaction()
        transaction.addAction(muteCallAction)

        requestTransaction(transaction)
    }

    func answer(call: SignalCall) {
        let answerCallAction = CXAnswerCallAction(call: call.individualCall.localId)
        let transaction = CXTransaction()
        transaction.addAction(answerCallAction)

        requestTransaction(transaction)
    }

    private func requestTransaction(_ transaction: CXTransaction) {
        callController.request(transaction) { error in
            if let error = error {
                Logger.error("Error requesting transaction: \(error)")
            } else {
                Logger.debug("Requested transaction successfully")
            }
        }
    }

    // MARK: Call Management

    private(set) var calls = [SignalCall]()

    func callWithLocalId(_ localId: UUID) -> SignalCall? {
        guard let index = calls.firstIndex(where: { $0.individualCall.localId == localId }) else {
            return nil
        }
        return calls[index]
    }

    func addCall(_ call: SignalCall) {
        Logger.verbose("call: \(call)")
        owsAssertDebug(call.isIndividualCall)
        call.individualCall.wasReportedToSystem = true
        calls.append(call)
    }

    func removeCall(_ call: SignalCall) {
        Logger.verbose("call: \(call)")
        owsAssertDebug(call.isIndividualCall)
        call.individualCall.wasRemovedFromSystem = true
        guard calls.removeFirst(where: { $0 === call }) != nil else {
            Logger.warn("no call matching: \(call) to remove")
            return
        }
    }

    func removeAllCalls() {
        Logger.verbose("")
        calls.forEach { $0.individualCall.wasRemovedFromSystem = true }
        calls.removeAll()
    }
}

fileprivate extension Array {

    mutating func removeFirst(where predicate: (Element) throws -> Bool) rethrows -> Element? {
        guard let index = try firstIndex(where: predicate) else {
            return nil
        }

        return remove(at: index)
    }
}