PhoneCaller.swift

import CallKit
import Foundation

class PhoneCaller: NSObject {
    typealias OnCallConnected = () -> Void

    static let shared: PhoneCaller = PhoneCaller()
    private let observer = CXCallObserver()

    private var isCalling: Bool = false
    private var onCallConnected: OnCallConnected?

    override init() {
        super.init()
        observer.setDelegate(self, queue: nil)
    }

    /// Shows the OS dialog for calling the given `telephoneNumber`. If the call connects,
    /// the `onCallConnected` callback will be executed.
    ///
    /// - Parameters:
    ///   - telephoneNumber: The number to call.
    ///   - onCallConnected: Executed when the call connects.
    func call(_ telephoneNumber: String, onCallConnected: OnCallConnected? = nil) {
        reset()

        guard
            let url = URL(string: "tel://\(telephoneNumber)"),
            UIApplication.shared.canOpenURL(url)
        else {
            return
        }

        self.onCallConnected = onCallConnected

        UIApplication.shared.open(url, options: [:]) { success in
            if !success {
                self.reset()
            }
        }
    }

    private func reset() {
        isCalling = false
        onCallConnected = nil
    }

    private func debugPrint(_ call: CXCall) {
        print("--------------")
        print("hasConnected: \(call.hasConnected)")
        print("hasEnded: \(call.hasEnded)")
        print("isOnHold: \(call.isOnHold)")
        print("isOutgoing: \(call.isOutgoing)")
        print("appState: \(UIApplication.shared.applicationState.rawValue)")
        print("--------------")
    }
}

extension PhoneCaller: CXCallObserverDelegate {
    func callObserver(_ callObserver: CXCallObserver, callChanged call: CXCall) {
        // debugPrint(call)

        guard let onCallConnected = onCallConnected, call.isOutgoing else { return }

        if UIApplication.shared.applicationState == .active && !call.hasEnded {
            isCalling = true
        }

        if isCalling {
            if call.hasConnected {
                onCallConnected()
                reset()
            } else if call.hasEnded {
                reset()
            }
        }
    }
}