LoinViewModel.kt

const val MIN_PASSWORD_LENGTH = 8 // 최소 비밀번호 길이
const val TAG = "LoginViewModel"

class LoginViewModel(lifecycleOwner: LifecycleOwner, private val loginActions: LoginActions) : ViewModel(), LifecycleObserver, LoginFragment.LoginFragmentActions {

    val loginData = MutableLiveData<LoginViewData>() // view data 

    private val fbAuthListener: FirebaseAuth.AuthStateListener //로그인 상태 리스너
    private val fbAuth = FirebaseAuth.getInstance() // firebase auth 객체

    init {
        // login view data 초기화
        loginData.value = LoginViewData("", "", "", null, false, false, null)
        
        // auth listener 초기화
        fbAuthListener = FirebaseAuth.AuthStateListener { firebaseAuth ->
            val user = firebaseAuth.currentUser
            if (user != null) {
                // User is signed in
                LogUtil.d(TAG, "onAuthStateChanged:signed_in:" + user.uid)
            } else {
                // User is signed out
                LogUtil.d(TAG, "onAuthStateChanged:signed_out")
            }
        }
        // lifecycle observer 등록
        lifecycleOwner.lifecycle.addObserver(this)
    }

    @OnLifecycleEvent(Lifecycle.Event.ON_START)
    fun registerAuthListener() {
        // auth 상태 정보 listener 등록
        fbAuth.addAuthStateListener(fbAuthListener)
    }

    @OnLifecycleEvent(Lifecycle.Event.ON_STOP)
    fun unregisterAuthListener() {
        // auth 상태 정보 listener 
        fbAuth.removeAuthStateListener(fbAuthListener)
    }

    /**
     * 이메일 확인
     */
    override fun onEmailChanged(email: String) {
        if (Validator.isEmailValid(email)) {
            loginData.value!!.email = email
        } else {
            loginData.value!!.email = ""
        }
    }

    /**
     * 패스워드 확인
     */
    override fun onPasswordChanged(password: String) {
        if (password.length >= MIN_PASSWORD_LENGTH) {
            loginData.value!!.password = password
        } else {
            loginData.value!!.password = ""
        }
    }

    /**
     * 이메일 로그인 시도
     */
    override fun onClickEmailLogin() {
        // 입력 정보 확인
        val error = checkError()
        if (error != null) {
            loginData.value = loginData.value!!.copy(error = error, isSuccessLogin = false)
            return
        }

        // 에러 초기화
        loginData.value!!.error = null

        // loading 시작 : show progressbar
        loginData.value = loginData.value!!.copy(isLoading = true)

        // firebase auth 이메일 로그인
        fbAuth.signInWithEmailAndPassword(loginData.value!!.email, loginData.value!!.password)
                .addOnCompleteListener({ task ->

                    // login response 처리
                    if (task.isSuccessful) {
                        loginActions.successLogin()
                    } else {
                        checkExistEmail()
                    }
                })
    }

    /**
     * 기존 가입 여부 확인
     */
    private fun checkExistEmail() {
        fbAuth.fetchProvidersForEmail(loginData.value!!.email)
                .addOnCompleteListener({ task ->
                    // 이메일 존재
                    if (task.isSuccessful) {
                        ///////// getProviders().size() will return size 1. if email ID is available.
                        loginData.value = loginData.value!!.copy(isAlreadyExist = task.result.providers!!.size == 1)
                    } else {
                        loginData.value = loginData.value!!.copy(isLoading = false,
                                isSuccessLogin = false,
                                error = ERROR.SERVER_ERROR
                                        .apply {
                                            errorMsg = task.exception?.message!!
                                        })

                        loginData.value!!.error = null
                    }
                })
    }

    /**
     * 이메일로 가입하기
     */
    fun signUpEmail() {
        fbAuth.createUserWithEmailAndPassword(loginData.value!!.email, loginData.value!!.password)
                .addOnCompleteListener({ task ->
                    //회원가입 완료
                    if (task.isSuccessful) {
                        loginActions.successLogin()
                    } else {
                        loginData.value = loginData.value!!.copy(isLoading = false,
                                isSuccessLogin = false,
                                error = ERROR.SERVER_ERROR
                                        .apply {
                                            errorMsg = task.exception?.message!!
                                        })

                        loginData.value!!.error = null
                    }
                })
    }

    /**
     * 입력값 에러 확인
     */
    private fun checkError(): ERROR? {
        when {
            TextUtils.isEmpty(loginData.value!!.email) -> return ERROR.INVALID_EMAIL
            TextUtils.isEmpty(loginData.value!!.password) -> return ERROR.INVALID_PASSWORD
        }

        return null
    }

    override fun onClickFacebookLogin() {
        TODO("not implemented") //To change body of created functions use File | Settings | File Templates.
    }

    class ViewModelFactory(private val lifecycleOwner: LifecycleOwner, private val loginActions: LoginActions) : ViewModelProvider.Factory {
        override fun <T : ViewModel?> create(modelClass: Class<T>): T {
            return LoginViewModel(lifecycleOwner, loginActions) as T
        }

    }

}