android auth: add step-based email/register/2fa flow and startup route

android/CHANGELOG.md

@@ -765,3 +765,18 @@
   - group invites.
 - Removed direct `block by user id` controls from Settings UI as requested.
 - Removed extra bottom Settings actions (`Profile` row and `Back to chats` button) and kept categorized section layout.
+
+### Step 113 - Auth flow redesign (email -> password/register -> 2FA) + startup no-flicker
+- Added step-based auth domain/use-cases for:
+  - `GET /api/v1/auth/check-email`
+  - `POST /api/v1/auth/register`
+  - login with optional `otp_code` / `recovery_code`.
+- Updated Android login UI to multi-step flow:
+  - step 1: email input,
+  - step 2: password for existing account or register form (`name`, `username`, `password`) for new account,
+  - step 3: 2FA OTP/recovery code when backend requires it.
+- Improved login error mapping for 2FA-required responses, so app switches to OTP step instead of generic invalid-password message.
+- Removed auth screen flash on startup:
+  - introduced dedicated `startup` route with session-check loader,
+  - delayed auth/chats navigation until session check is finished.
+- Added safe fallback in `MainActivity` theme bootstrap to prevent crash if `ThemeRepository` injection is unexpectedly unavailable during startup.

android/app/src/main/java/ru/daemonlord/messenger/MainActivity.kt

@@ -34,7 +34,11 @@ class MainActivity : AppCompatActivity() {
 
     override fun onCreate(savedInstanceState: Bundle?) {
         super.onCreate(savedInstanceState)
-        val savedThemeMode = runBlocking { themeRepository.getThemeMode() }
+        val savedThemeMode = if (this::themeRepository.isInitialized) {
+            runBlocking { themeRepository.getThemeMode() }
+        } else {
+            AppThemeMode.SYSTEM
+        }
         AppCompatDelegate.setDefaultNightMode(
             when (savedThemeMode) {
                 AppThemeMode.LIGHT -> AppCompatDelegate.MODE_NIGHT_NO

android/app/src/main/java/ru/daemonlord/messenger/data/auth/repository/NetworkAuthRepository.kt

@@ -7,12 +7,15 @@ import ru.daemonlord.messenger.core.token.StoredAccount
 import ru.daemonlord.messenger.core.token.TokenRepository
 import ru.daemonlord.messenger.data.auth.api.AuthApiService
 import ru.daemonlord.messenger.data.auth.dto.AuthUserDto
+import ru.daemonlord.messenger.data.auth.dto.CheckEmailStatusDto
 import ru.daemonlord.messenger.data.auth.dto.AuthSessionDto
 import ru.daemonlord.messenger.data.auth.dto.LoginRequestDto
 import ru.daemonlord.messenger.data.auth.dto.RefreshTokenRequestDto
+import ru.daemonlord.messenger.data.auth.dto.RegisterRequestDto
 import ru.daemonlord.messenger.data.common.ApiErrorMode
 import ru.daemonlord.messenger.data.common.toAppError
 import ru.daemonlord.messenger.di.IoDispatcher
+import ru.daemonlord.messenger.domain.auth.model.AuthEmailStatus
 import ru.daemonlord.messenger.domain.auth.model.AuthUser
 import ru.daemonlord.messenger.domain.auth.model.AuthSession
 import ru.daemonlord.messenger.domain.auth.repository.AuthRepository
@@ -30,12 +33,56 @@ class NetworkAuthRepository @Inject constructor(
     @IoDispatcher private val ioDispatcher: CoroutineDispatcher,
 ) : AuthRepository {
 
-    override suspend fun login(email: String, password: String): AppResult<AuthUser> = withContext(ioDispatcher) {
+    override suspend fun checkEmailStatus(email: String): AppResult<AuthEmailStatus> = withContext(ioDispatcher) {
+        val normalized = email.trim().lowercase()
+        if (normalized.isBlank()) return@withContext AppResult.Error(AppError.Server("Email is required"))
+        try {
+            AppResult.Success(authApiService.checkEmailStatus(normalized).toDomain())
+        } catch (error: Throwable) {
+            AppResult.Error(error.toAppError())
+        }
+    }
+
+    override suspend fun register(
+        email: String,
+        name: String,
+        username: String,
+        password: String,
+    ): AppResult<Unit> = withContext(ioDispatcher) {
+        val normalizedEmail = email.trim().lowercase()
+        val normalizedName = name.trim()
+        val normalizedUsername = username.trim().removePrefix("@")
+        if (normalizedEmail.isBlank() || normalizedName.isBlank() || normalizedUsername.isBlank() || password.isBlank()) {
+            return@withContext AppResult.Error(AppError.Server("Email, name, username and password are required"))
+        }
+        try {
+            authApiService.register(
+                request = RegisterRequestDto(
+                    email = normalizedEmail,
+                    name = normalizedName,
+                    username = normalizedUsername,
+                    password = password,
+                )
+            )
+            AppResult.Success(Unit)
+        } catch (error: Throwable) {
+            AppResult.Error(error.toAppError())
+        }
+    }
+
+    override suspend fun login(
+        email: String,
+        password: String,
+        otpCode: String?,
+        recoveryCode: String?,
+    ): AppResult<AuthUser> = withContext(ioDispatcher) {
         try {
             val tokenResponse = authApiService.login(
                 request = LoginRequestDto(
                     email = email,
                     password = password,
+                    otpCode = otpCode?.trim()?.ifBlank { null },
+                    recoveryCode = recoveryCode?.trim()?.ifBlank { null },
                 )
             )
             tokenRepository.saveTokens(
@@ -183,4 +230,13 @@ class NetworkAuthRepository @Inject constructor(
         )
     }
 
+    private fun CheckEmailStatusDto.toDomain(): AuthEmailStatus {
+        return AuthEmailStatus(
+            email = email,
+            registered = registered,
+            emailVerified = emailVerified,
+            twofaEnabled = twofaEnabled,
+        )
+    }
+
 }

android/app/src/main/java/ru/daemonlord/messenger/data/common/ApiErrorMapper.kt

@@ -3,6 +3,7 @@ package ru.daemonlord.messenger.data.common
 import retrofit2.HttpException
 import ru.daemonlord.messenger.domain.common.AppError
 import java.io.IOException
+import org.json.JSONObject
 
 enum class ApiErrorMode {
     DEFAULT,
@@ -13,15 +14,24 @@ fun Throwable.toAppError(mode: ApiErrorMode = ApiErrorMode.DEFAULT): AppError {
     return when (this) {
         is IOException -> AppError.Network
         is HttpException -> when (mode) {
-            ApiErrorMode.LOGIN -> when (code()) {
-                400, 401, 403 -> AppError.InvalidCredentials
-                else -> AppError.Server(message = message())
+            ApiErrorMode.LOGIN -> {
+                val detail = extractErrorDetail()
+                when (code()) {
+                    400, 401, 403 -> {
+                        if (detail?.contains("2fa code required", ignoreCase = true) == true) {
+                            AppError.Server(message = detail)
+                        } else {
+                            AppError.InvalidCredentials
+                        }
+                    }
+                    else -> AppError.Server(message = detail ?: message())
+                }
             }
 
             ApiErrorMode.DEFAULT -> if (code() == 401 || code() == 403) {
                 AppError.Unauthorized
             } else {
-                AppError.Server(message = message())
+                AppError.Server(message = extractErrorDetail() ?: message())
             }
         }
 
@@ -29,3 +39,11 @@ fun Throwable.toAppError(mode: ApiErrorMode = ApiErrorMode.DEFAULT): AppError {
     }
 }
 
+private fun HttpException.extractErrorDetail(): String? {
+    return runCatching {
+        val body = response()?.errorBody()?.string()?.trim().orEmpty()
+        if (body.isBlank()) return@runCatching null
+        val json = JSONObject(body)
+        json.optString("detail").takeIf { it.isNotBlank() }
+    }.getOrNull()
+}

android/app/src/main/java/ru/daemonlord/messenger/domain/auth/model/AuthEmailStatus.kt

@@ -0,0 +1,9 @@
+package ru.daemonlord.messenger.domain.auth.model
+
+data class AuthEmailStatus(
+    val email: String,
+    val registered: Boolean,
+    val emailVerified: Boolean,
+    val twofaEnabled: Boolean,
+)
+

android/app/src/main/java/ru/daemonlord/messenger/domain/auth/repository/AuthRepository.kt

@@ -2,10 +2,18 @@ package ru.daemonlord.messenger.domain.auth.repository
 
 import ru.daemonlord.messenger.domain.auth.model.AuthUser
 import ru.daemonlord.messenger.domain.auth.model.AuthSession
+import ru.daemonlord.messenger.domain.auth.model.AuthEmailStatus
 import ru.daemonlord.messenger.domain.common.AppResult
 
 interface AuthRepository {
-    suspend fun login(email: String, password: String): AppResult<AuthUser>
+    suspend fun checkEmailStatus(email: String): AppResult<AuthEmailStatus>
+    suspend fun register(email: String, name: String, username: String, password: String): AppResult<Unit>
+    suspend fun login(
+        email: String,
+        password: String,
+        otpCode: String? = null,
+        recoveryCode: String? = null,
+    ): AppResult<AuthUser>
     suspend fun refreshTokens(): AppResult<Unit>
     suspend fun getMe(): AppResult<AuthUser>
     suspend fun restoreSession(): AppResult<AuthUser>

android/app/src/main/java/ru/daemonlord/messenger/domain/auth/usecase/CheckEmailStatusUseCase.kt

@@ -0,0 +1,15 @@
+package ru.daemonlord.messenger.domain.auth.usecase
+
+import ru.daemonlord.messenger.domain.auth.model.AuthEmailStatus
+import ru.daemonlord.messenger.domain.auth.repository.AuthRepository
+import ru.daemonlord.messenger.domain.common.AppResult
+import javax.inject.Inject
+
+class CheckEmailStatusUseCase @Inject constructor(
+    private val authRepository: AuthRepository,
+) {
+    suspend operator fun invoke(email: String): AppResult<AuthEmailStatus> {
+        return authRepository.checkEmailStatus(email)
+    }
+}
+

android/app/src/main/java/ru/daemonlord/messenger/domain/auth/usecase/LoginUseCase.kt

@@ -8,7 +8,17 @@ import javax.inject.Inject
 class LoginUseCase @Inject constructor(
     private val authRepository: AuthRepository,
 ) {
-    suspend operator fun invoke(email: String, password: String): AppResult<AuthUser> {
-        return authRepository.login(email = email, password = password)
+    suspend operator fun invoke(
+        email: String,
+        password: String,
+        otpCode: String? = null,
+        recoveryCode: String? = null,
+    ): AppResult<AuthUser> {
+        return authRepository.login(
+            email = email,
+            password = password,
+            otpCode = otpCode,
+            recoveryCode = recoveryCode,
+        )
     }
 }

android/app/src/main/java/ru/daemonlord/messenger/domain/auth/usecase/RegisterUseCase.kt

@@ -0,0 +1,24 @@
+package ru.daemonlord.messenger.domain.auth.usecase
+
+import ru.daemonlord.messenger.domain.auth.repository.AuthRepository
+import ru.daemonlord.messenger.domain.common.AppResult
+import javax.inject.Inject
+
+class RegisterUseCase @Inject constructor(
+    private val authRepository: AuthRepository,
+) {
+    suspend operator fun invoke(
+        email: String,
+        name: String,
+        username: String,
+        password: String,
+    ): AppResult<Unit> {
+        return authRepository.register(
+            email = email,
+            name = name,
+            username = username,
+            password = password,
+        )
+    }
+}
+

android/app/src/main/java/ru/daemonlord/messenger/ui/auth/AuthUiState.kt

@@ -1,10 +1,25 @@
 package ru.daemonlord.messenger.ui.auth
 
+enum class AuthStep {
+    EMAIL,
+    PASSWORD,
+    REGISTER,
+    OTP,
+}
+
 data class AuthUiState(
+    val step: AuthStep = AuthStep.EMAIL,
     val email: String = "",
+    val name: String = "",
+    val username: String = "",
     val password: String = "",
+    val otpCode: String = "",
+    val recoveryCode: String = "",
+    val useRecoveryCode: Boolean = false,
     val isCheckingSession: Boolean = true,
     val isLoading: Boolean = false,
     val isAuthenticated: Boolean = false,
+    val successMessage: String? = null,
     val errorMessage: String? = null,
 )
+

android/app/src/main/java/ru/daemonlord/messenger/ui/auth/AuthViewModel.kt

@@ -8,8 +8,10 @@ import kotlinx.coroutines.flow.StateFlow
 import kotlinx.coroutines.flow.asStateFlow
 import kotlinx.coroutines.flow.update
 import kotlinx.coroutines.launch
+import ru.daemonlord.messenger.domain.auth.usecase.CheckEmailStatusUseCase
 import ru.daemonlord.messenger.domain.auth.usecase.LoginUseCase
 import ru.daemonlord.messenger.domain.auth.usecase.LogoutUseCase
+import ru.daemonlord.messenger.domain.auth.usecase.RegisterUseCase
 import ru.daemonlord.messenger.domain.auth.usecase.RestoreSessionUseCase
 import ru.daemonlord.messenger.domain.common.AppError
 import ru.daemonlord.messenger.domain.common.AppResult
@@ -18,6 +20,8 @@ import javax.inject.Inject
 @HiltViewModel
 class AuthViewModel @Inject constructor(
     private val restoreSessionUseCase: RestoreSessionUseCase,
+    private val checkEmailStatusUseCase: CheckEmailStatusUseCase,
+    private val registerUseCase: RegisterUseCase,
     private val loginUseCase: LoginUseCase,
     private val logoutUseCase: LogoutUseCase,
 ) : ViewModel() {
@@ -30,23 +34,220 @@ class AuthViewModel @Inject constructor(
     }
 
     fun onEmailChanged(value: String) {
-        _uiState.update { it.copy(email = value, errorMessage = null) }
+        _uiState.update {
+            it.copy(
+                email = value,
+                errorMessage = null,
+                successMessage = null,
+            )
+        }
+    }
+
+    fun onNameChanged(value: String) {
+        _uiState.update { it.copy(name = value, errorMessage = null) }
+    }
+
+    fun onUsernameChanged(value: String) {
+        _uiState.update { it.copy(username = value.replace("@", ""), errorMessage = null) }
     }
 
     fun onPasswordChanged(value: String) {
         _uiState.update { it.copy(password = value, errorMessage = null) }
     }
 
-    fun login() {
-        val state = uiState.value
-        if (state.email.isBlank() || state.password.isBlank()) {
-            _uiState.update { it.copy(errorMessage = "Email and password are required.") }
+    fun onOtpCodeChanged(value: String) {
+        _uiState.update { it.copy(otpCode = value.filter(Char::isDigit).take(8), errorMessage = null) }
+    }
+
+    fun onRecoveryCodeChanged(value: String) {
+        _uiState.update {
+            it.copy(
+                recoveryCode = value.uppercase().filter { ch -> ch.isLetterOrDigit() || ch == '-' }.take(32),
+                errorMessage = null,
+            )
+        }
+    }
+
+    fun toggleRecoveryCodeMode() {
+        _uiState.update {
+            it.copy(
+                useRecoveryCode = !it.useRecoveryCode,
+                errorMessage = null,
+                successMessage = null,
+            )
+        }
+    }
+
+    fun backToEmailStep() {
+        _uiState.update {
+            it.copy(
+                step = AuthStep.EMAIL,
+                password = "",
+                otpCode = "",
+                recoveryCode = "",
+                useRecoveryCode = false,
+                errorMessage = null,
+                successMessage = null,
+            )
+        }
+    }
+
+    fun continueWithEmail() {
+        val email = uiState.value.email.trim().lowercase()
+        if (email.isBlank()) {
+            _uiState.update { it.copy(errorMessage = "Enter email.") }
             return
         }
-
         viewModelScope.launch {
-            _uiState.update { it.copy(isLoading = true, errorMessage = null) }
+            _uiState.update {
+                it.copy(
+                    isLoading = true,
+                    errorMessage = null,
+                    successMessage = null,
+                )
+            }
+            when (val result = checkEmailStatusUseCase(email)) {
+                is AppResult.Success -> {
+                    _uiState.update {
+                        it.copy(
+                            email = result.data.email,
+                            isLoading = false,
+                            step = if (result.data.registered) AuthStep.PASSWORD else AuthStep.REGISTER,
+                            errorMessage = null,
+                            successMessage = if (result.data.registered) null else "This email is not registered. Complete sign up.",
+                        )
+                    }
+                }
+                is AppResult.Error -> {
+                    _uiState.update {
+                        it.copy(
+                            isLoading = false,
+                            errorMessage = result.reason.toUiMessage(),
+                            successMessage = null,
+                        )
+                    }
+                }
+            }
+        }
+    }
+
+    fun submitAuthStep() {
+        when (uiState.value.step) {
+            AuthStep.EMAIL -> continueWithEmail()
+            AuthStep.REGISTER -> register()
+            AuthStep.PASSWORD -> loginWithoutOtp()
+            AuthStep.OTP -> loginWithOtp()
+        }
+    }
+
+    private fun register() {
+        val state = uiState.value
+        if (state.name.isBlank() || state.username.isBlank() || state.password.isBlank()) {
+            _uiState.update { it.copy(errorMessage = "Name, username and password are required.") }
+            return
+        }
+        viewModelScope.launch {
+            _uiState.update { it.copy(isLoading = true, errorMessage = null, successMessage = null) }
+            when (
+                val result = registerUseCase(
+                    email = state.email.trim().lowercase(),
+                    name = state.name.trim(),
+                    username = state.username.trim().removePrefix("@"),
+                    password = state.password,
+                )
+            ) {
+                is AppResult.Success -> {
+                    _uiState.update {
+                        it.copy(
+                            isLoading = false,
+                            step = AuthStep.PASSWORD,
+                            successMessage = "Account created. Use password to sign in.",
+                            errorMessage = null,
+                        )
+                    }
+                }
+                is AppResult.Error -> {
+                    _uiState.update {
+                        it.copy(
+                            isLoading = false,
+                            errorMessage = result.reason.toUiMessage(),
+                            successMessage = null,
+                        )
+                    }
+                }
+            }
+        }
+    }
+
+    private fun loginWithoutOtp() {
+        val state = uiState.value
+        if (state.password.isBlank()) {
+            _uiState.update { it.copy(errorMessage = "Password is required.") }
+            return
+        }
+        viewModelScope.launch {
+            _uiState.update { it.copy(isLoading = true, errorMessage = null, successMessage = null) }
             when (val result = loginUseCase(state.email.trim(), state.password)) {
+                is AppResult.Success -> {
+                    _uiState.update {
+                        it.copy(
+                            isLoading = false,
+                            isAuthenticated = true,
+                            errorMessage = null,
+                            successMessage = null,
+                        )
+                    }
+                }
+                is AppResult.Error -> {
+                    val isOtpRequired = (result.reason as? AppError.Server)
+                        ?.message
+                        ?.contains("2fa code required", ignoreCase = true) == true
+                    if (isOtpRequired) {
+                        _uiState.update {
+                            it.copy(
+                                isLoading = false,
+                                step = AuthStep.OTP,
+                                errorMessage = null,
+                                successMessage = "Enter 2FA code or recovery code.",
+                            )
+                        }
+                    } else {
+                        _uiState.update {
+                            it.copy(
+                                isLoading = false,
+                                isAuthenticated = false,
+                                errorMessage = result.reason.toUiMessage(),
+                                successMessage = null,
+                            )
+                        }
+                    }
+                }
+            }
+        }
+    }
+
+    private fun loginWithOtp() {
+        val state = uiState.value
+        val otpCode = state.otpCode.trim().ifBlank { null }
+        val recoveryCode = state.recoveryCode.trim().ifBlank { null }
+        if (!state.useRecoveryCode && otpCode.isNullOrBlank()) {
+            _uiState.update { it.copy(errorMessage = "Enter 2FA code.") }
+            return
+        }
+        if (state.useRecoveryCode && recoveryCode.isNullOrBlank()) {
+            _uiState.update { it.copy(errorMessage = "Enter recovery code.") }
+            return
+        }
+        viewModelScope.launch {
+            _uiState.update { it.copy(isLoading = true, errorMessage = null, successMessage = null) }
+            when (
+                val result = loginUseCase(
+                    email = state.email.trim(),
+                    password = state.password,
+                    otpCode = if (state.useRecoveryCode) null else otpCode,
+                    recoveryCode = if (state.useRecoveryCode) recoveryCode else null,
+                )
+            ) {
                 is AppResult.Success -> {
                     _uiState.update {
                         it.copy(
@@ -56,7 +257,6 @@ class AuthViewModel @Inject constructor(
                         )
                     }
                 }
-
                 is AppResult.Error -> {
                     _uiState.update {
                         it.copy(
@@ -76,11 +276,18 @@ class AuthViewModel @Inject constructor(
             runCatching { logoutUseCase() }
             _uiState.update {
                 it.copy(
+                    step = AuthStep.EMAIL,
                     email = "",
+                    name = "",
+                    username = "",
                     password = "",
+                    otpCode = "",
+                    recoveryCode = "",
+                    useRecoveryCode = false,
                     isLoading = false,
                     isAuthenticated = false,
                     errorMessage = null,
+                    successMessage = null,
                 )
             }
         }
@@ -103,7 +310,6 @@ class AuthViewModel @Inject constructor(
                         )
                     }
                 }
-
                 is AppResult.Error -> {
                     val keepAuthenticatedOffline = result.reason is AppError.Network
                     _uiState.update {
@@ -123,7 +329,7 @@ class AuthViewModel @Inject constructor(
             AppError.InvalidCredentials -> "Invalid email or password."
             AppError.Network -> "Network error. Check your connection."
             AppError.Unauthorized -> "Session expired. Please sign in again."
-            is AppError.Server -> "Server error. Please try again."
+            is AppError.Server -> message ?: "Server error. Please try again."
             is AppError.Unknown -> "Unknown error. Please try again."
         }
     }

android/app/src/main/java/ru/daemonlord/messenger/ui/auth/LoginScreen.kt

@@ -27,12 +27,21 @@ import androidx.compose.ui.unit.dp
 fun LoginScreen(
     state: AuthUiState,
     onEmailChanged: (String) -> Unit,
+    onNameChanged: (String) -> Unit,
+    onUsernameChanged: (String) -> Unit,
     onPasswordChanged: (String) -> Unit,
-    onLoginClick: () -> Unit,
+    onOtpCodeChanged: (String) -> Unit,
+    onRecoveryCodeChanged: (String) -> Unit,
+    onToggleRecoveryCodeMode: () -> Unit,
+    onContinueEmail: () -> Unit,
+    onSubmitStep: () -> Unit,
+    onBackToEmail: () -> Unit,
     onOpenVerifyEmail: () -> Unit,
     onOpenResetPassword: () -> Unit,
 ) {
     val isTabletLayout = LocalConfiguration.current.screenWidthDp >= 840
+    val isBusy = state.isLoading
+
     Box(
         modifier = Modifier
             .fillMaxSize()
@@ -47,71 +56,194 @@ fun LoginScreen(
             verticalArrangement = Arrangement.Center,
             horizontalAlignment = Alignment.CenterHorizontally,
         ) {
-        Text(
-            text = "Messenger Login",
-            style = MaterialTheme.typography.headlineSmall,
-            modifier = Modifier.padding(bottom = 24.dp),
-        )
-
-        OutlinedTextField(
-            value = state.email,
-            onValueChange = onEmailChanged,
-            label = { Text(text = "Email") },
-            singleLine = true,
-            enabled = !state.isLoading,
-            modifier = Modifier
-                .fillMaxWidth()
-                .padding(bottom = 12.dp),
-        )
-
-        OutlinedTextField(
-            value = state.password,
-            onValueChange = onPasswordChanged,
-            label = { Text(text = "Password") },
-            visualTransformation = PasswordVisualTransformation(),
-            singleLine = true,
-            enabled = !state.isLoading,
-            modifier = Modifier
-                .fillMaxWidth()
-                .padding(bottom = 16.dp),
-        )
-
-        Button(
-            onClick = onLoginClick,
-            enabled = !state.isLoading,
-            modifier = Modifier.fillMaxWidth(),
-        ) {
-            if (state.isLoading) {
-                CircularProgressIndicator(
-                    strokeWidth = 2.dp,
-                    modifier = Modifier.padding(2.dp),
-                )
-            } else {
-                Text(text = "Login")
-            }
-        }
-
-        if (!state.errorMessage.isNullOrBlank()) {
             Text(
-                text = state.errorMessage,
-                color = MaterialTheme.colorScheme.error,
-                style = MaterialTheme.typography.bodyMedium,
-                modifier = Modifier.padding(top = 12.dp),
+                text = "Messenger Login",
+                style = MaterialTheme.typography.headlineSmall,
+                modifier = Modifier.padding(bottom = 14.dp),
             )
-        }
-        TextButton(
-            onClick = onOpenVerifyEmail,
-            enabled = !state.isLoading,
-            modifier = Modifier.padding(top = 8.dp),
-        ) {
-            Text(text = "Verify email by token")
-        }
-        TextButton(
-            onClick = onOpenResetPassword,
-            enabled = !state.isLoading,
-        ) {
-            Text(text = "Forgot password")
-        }
+
+            val subtitle = when (state.step) {
+                AuthStep.EMAIL -> "Enter your email to continue"
+                AuthStep.PASSWORD -> "Enter password for ${state.email}"
+                AuthStep.REGISTER -> "Create account for ${state.email}"
+                AuthStep.OTP -> "Two-factor authentication is enabled"
+            }
+            Text(
+                text = subtitle,
+                style = MaterialTheme.typography.bodyMedium,
+                color = MaterialTheme.colorScheme.onSurfaceVariant,
+                modifier = Modifier.padding(bottom = 18.dp),
+            )
+
+            when (state.step) {
+                AuthStep.EMAIL -> {
+                    OutlinedTextField(
+                        value = state.email,
+                        onValueChange = onEmailChanged,
+                        label = { Text(text = "Email") },
+                        singleLine = true,
+                        enabled = !isBusy,
+                        modifier = Modifier
+                            .fillMaxWidth()
+                            .padding(bottom = 16.dp),
+                    )
+                    Button(
+                        onClick = onContinueEmail,
+                        enabled = !isBusy,
+                        modifier = Modifier.fillMaxWidth(),
+                    ) {
+                        if (isBusy) {
+                            CircularProgressIndicator(strokeWidth = 2.dp, modifier = Modifier.padding(2.dp))
+                        } else {
+                            Text("Continue")
+                        }
+                    }
+                }
+
+                AuthStep.PASSWORD, AuthStep.REGISTER, AuthStep.OTP -> {
+                    OutlinedTextField(
+                        value = state.email,
+                        onValueChange = {},
+                        readOnly = true,
+                        label = { Text(text = "Email") },
+                        singleLine = true,
+                        modifier = Modifier
+                            .fillMaxWidth()
+                            .padding(bottom = 8.dp),
+                    )
+                    TextButton(
+                        onClick = onBackToEmail,
+                        enabled = !isBusy,
+                        modifier = Modifier
+                            .align(Alignment.Start)
+                            .padding(bottom = 6.dp),
+                    ) {
+                        Text("Change email")
+                    }
+
+                    if (state.step == AuthStep.REGISTER) {
+                        OutlinedTextField(
+                            value = state.name,
+                            onValueChange = onNameChanged,
+                            label = { Text(text = "Name") },
+                            singleLine = true,
+                            enabled = !isBusy,
+                            modifier = Modifier
+                                .fillMaxWidth()
+                                .padding(bottom = 10.dp),
+                        )
+                        OutlinedTextField(
+                            value = state.username,
+                            onValueChange = onUsernameChanged,
+                            label = { Text(text = "Username") },
+                            singleLine = true,
+                            enabled = !isBusy,
+                            modifier = Modifier
+                                .fillMaxWidth()
+                                .padding(bottom = 10.dp),
+                        )
+                    }
+
+                    if (state.step != AuthStep.OTP) {
+                        OutlinedTextField(
+                            value = state.password,
+                            onValueChange = onPasswordChanged,
+                            label = { Text(text = "Password") },
+                            visualTransformation = PasswordVisualTransformation(),
+                            singleLine = true,
+                            enabled = !isBusy,
+                            modifier = Modifier
+                                .fillMaxWidth()
+                                .padding(bottom = 10.dp),
+                        )
+                    }
+
+                    if (state.step == AuthStep.OTP) {
+                        TextButton(
+                            onClick = onToggleRecoveryCodeMode,
+                            enabled = !isBusy,
+                            modifier = Modifier
+                                .align(Alignment.Start)
+                                .padding(bottom = 4.dp),
+                        ) {
+                            Text(if (state.useRecoveryCode) "Use OTP code" else "Use recovery code")
+                        }
+                        if (state.useRecoveryCode) {
+                            OutlinedTextField(
+                                value = state.recoveryCode,
+                                onValueChange = onRecoveryCodeChanged,
+                                label = { Text(text = "Recovery code") },
+                                singleLine = true,
+                                enabled = !isBusy,
+                                modifier = Modifier
+                                    .fillMaxWidth()
+                                    .padding(bottom = 10.dp),
+                            )
+                        } else {
+                            OutlinedTextField(
+                                value = state.otpCode,
+                                onValueChange = onOtpCodeChanged,
+                                label = { Text(text = "2FA code") },
+                                singleLine = true,
+                                enabled = !isBusy,
+                                modifier = Modifier
+                                    .fillMaxWidth()
+                                    .padding(bottom = 10.dp),
+                            )
+                        }
+                    }
+
+                    Button(
+                        onClick = onSubmitStep,
+                        enabled = !isBusy,
+                        modifier = Modifier.fillMaxWidth(),
+                    ) {
+                        if (isBusy) {
+                            CircularProgressIndicator(strokeWidth = 2.dp, modifier = Modifier.padding(2.dp))
+                        } else {
+                            Text(
+                                when (state.step) {
+                                    AuthStep.PASSWORD -> "Sign in"
+                                    AuthStep.REGISTER -> "Create account"
+                                    AuthStep.OTP -> "Confirm 2FA"
+                                    AuthStep.EMAIL -> "Continue"
+                                }
+                            )
+                        }
+                    }
+                }
+            }
+
+            if (!state.errorMessage.isNullOrBlank()) {
+                Text(
+                    text = state.errorMessage,
+                    color = MaterialTheme.colorScheme.error,
+                    style = MaterialTheme.typography.bodyMedium,
+                    modifier = Modifier.padding(top = 12.dp),
+                )
+            }
+            if (!state.successMessage.isNullOrBlank()) {
+                Text(
+                    text = state.successMessage,
+                    color = MaterialTheme.colorScheme.primary,
+                    style = MaterialTheme.typography.bodyMedium,
+                    modifier = Modifier.padding(top = 12.dp),
+                )
+            }
+
+            TextButton(
+                onClick = onOpenVerifyEmail,
+                enabled = !isBusy,
+                modifier = Modifier.padding(top = 8.dp),
+            ) {
+                Text(text = "Verify email by token")
+            }
+            TextButton(
+                onClick = onOpenResetPassword,
+                enabled = !isBusy,
+            ) {
+                Text(text = "Forgot password")
+            }
         }
     }
 }

android/app/src/main/java/ru/daemonlord/messenger/ui/navigation/AppNavGraph.kt

@@ -68,6 +68,7 @@ import ru.daemonlord.messenger.ui.profile.ProfileRoute
 import ru.daemonlord.messenger.ui.settings.SettingsRoute
 
 private object Routes {
+    const val Startup = "startup"
     const val AuthGraph = "auth_graph"
     const val Login = "login"
     const val VerifyEmail = "verify_email"
@@ -167,25 +168,32 @@ fun MessengerNavHost(
     Box(modifier = Modifier.fillMaxSize()) {
         NavHost(
             navController = navController,
-            startDestination = Routes.AuthGraph,
+            startDestination = Routes.Startup,
         ) {
+            composable(route = Routes.Startup) {
+                SessionCheckingScreen()
+            }
+
             navigation(
                 route = Routes.AuthGraph,
                 startDestination = Routes.Login,
             ) {
                 composable(route = Routes.Login) {
-                    if (uiState.isCheckingSession) {
-                        SessionCheckingScreen()
-                    } else {
-                        LoginScreen(
-                            state = uiState,
-                            onEmailChanged = viewModel::onEmailChanged,
-                            onPasswordChanged = viewModel::onPasswordChanged,
-                            onLoginClick = viewModel::login,
-                            onOpenVerifyEmail = { navController.navigate(Routes.VerifyEmail) },
-                            onOpenResetPassword = { navController.navigate(Routes.ResetPassword) },
-                        )
-                    }
+                    LoginScreen(
+                        state = uiState,
+                        onEmailChanged = viewModel::onEmailChanged,
+                        onNameChanged = viewModel::onNameChanged,
+                        onUsernameChanged = viewModel::onUsernameChanged,
+                        onPasswordChanged = viewModel::onPasswordChanged,
+                        onOtpCodeChanged = viewModel::onOtpCodeChanged,
+                        onRecoveryCodeChanged = viewModel::onRecoveryCodeChanged,
+                        onToggleRecoveryCodeMode = viewModel::toggleRecoveryCodeMode,
+                        onContinueEmail = viewModel::continueWithEmail,
+                        onSubmitStep = viewModel::submitAuthStep,
+                        onBackToEmail = viewModel::backToEmailStep,
+                        onOpenVerifyEmail = { navController.navigate(Routes.VerifyEmail) },
+                        onOpenResetPassword = { navController.navigate(Routes.ResetPassword) },
+                    )
                 }
             }