/// created by amir tutunchi

/// usage : to use this snippets of code go to project setting and in build phases in Link Binary With Libraries
/// add LocalAuthethication.framework (you can search it when you hit +) and call this method after you think user
/// enter correct username and password
/// self.saveAccountDetailsToKeychain(account: self.usernameTxtField.text!, password: self.passwordTxtField.text!, completion: {
///    print("data saved to keychain successfully")
/// })
/// hint : it will save username to userdefaults

import LocalAuthentication

extension ViewController{
    fileprivate func authenticateUserUsingTouchId() {
        let context = LAContext()
        if context.canEvaluatePolicy(LAPolicy.deviceOwnerAuthenticationWithBiometrics, error: nil) {
            self.evaulateTocuhIdAuthenticity(context: context)
        }
    }
    func evaulateTocuhIdAuthenticity(context: LAContext) {
        guard let lastAccessedUserName = UserDefaults.standard.string(forKey: "lastAccessedUserName") else { return }
        context.evaluatePolicy(LAPolicy.deviceOwnerAuthentication, localizedReason: lastAccessedUserName) { (authSuccessful, authError) in
            if authSuccessful {
                self.loadPasswordFromKeychainAndAuthenticateUser(lastAccessedUserName)
            } else {
                if let error = authError as? LAError {
                    self.showError(error: error)
                }
            }
        }
    }
    fileprivate func loadPasswordFromKeychainAndAuthenticateUser(_ account: String) {
        guard !account.isEmpty else { return }
        let passwordItem = KeychainPasswordItem(service:   KeychainConfiguration.serviceName, account: account, accessGroup: KeychainConfiguration.accessGroup)
        do {
            let storedPassword = try passwordItem.readPassword()
            atheticateUser(username : account  , password : storedPassword)
        } catch KeychainPasswordItem.KeychainError.noPassword {
            print("No saved password")
        } catch {
            print("Unhandled error")
        }
    }
    func atheticateUser(username : String , password : String){
        DispatchQueue.main.async {
          // set your username and password to text fields
            self.usernameTxtField.text = username
            self.passwordTxtField.text = password
          // call your login method
            self.LoginBtnClicked(UIButton())
        }
    }
    func showError(error: LAError) {
        var message: String = ""
        switch error.code {
        case LAError.authenticationFailed:
            message = "Authentication was not successful because the user failed to provide valid credentials. Please enter password to login."
            break
        case LAError.userCancel:
            message = "Authentication was canceled by the user"
            break
        case LAError.userFallback:
            message = "Authentication was canceled because the user tapped the fallback button"
            break
        case LAError.biometryNotEnrolled:
            message = "Authentication could not start because Touch ID has no enrolled fingers."
            break
        case LAError.passcodeNotSet:
            message = "Passcode is not set on the device."
            break
        case LAError.systemCancel:
            message = "Authentication was canceled by system"
            break
        default:
            message = error.localizedDescription
            break
        }
        print(message)
    }
    fileprivate func saveAccountDetailsToKeychain(account: String, password: String , completion : () -> Void) {
        UserDefaults.standard.set(account, forKey: "lastAccessedUserName")
        let passwordItem = KeychainPasswordItem(service: KeychainConfiguration.serviceName, account: account, accessGroup: KeychainConfiguration.accessGroup)
        do {
            try passwordItem.savePassword(password)
            completion()
        } catch {
            print("Error saving password")
            completion()
        }
    }
}