android: add auth UI flow and auth-to-chats navigation

android/CHANGELOG.md

@@ -14,3 +14,9 @@
 - Added auth network stack: bearer interceptor, 401 authenticator with refresh flow and retry guard.
 - Added clean-layer contracts and implementations: `domain/common`, `domain/auth`, `data/auth/repository`.
 - Wired dependencies with Hilt modules for DataStore, OkHttp/Retrofit, and repository bindings.
+
+### Step 3 - Minimal auth UI and navigation
+- Replaced Phase 0 placeholder UI with Compose auth flow (`AuthViewModel` + login screen).
+- Added loading/error states for login and startup session restore.
+- Added navigation graph: `AuthGraph (login)` to placeholder `Chats` screen after successful auth.
+- Implemented automatic session restore on app start using stored tokens.

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

@@ -3,18 +3,15 @@ package ru.daemonlord.messenger
 import android.os.Bundle
 import androidx.activity.ComponentActivity
 import androidx.activity.compose.setContent
-import androidx.compose.foundation.layout.Arrangement
-import androidx.compose.foundation.layout.Column
-import androidx.compose.foundation.layout.fillMaxSize
-import androidx.compose.foundation.layout.padding
 import androidx.compose.material3.MaterialTheme
 import androidx.compose.material3.Surface
-import androidx.compose.material3.Text
 import androidx.compose.runtime.Composable
-import androidx.compose.ui.Alignment
 import androidx.compose.ui.Modifier
-import androidx.compose.ui.unit.dp
+import androidx.compose.foundation.layout.fillMaxSize
+import dagger.hilt.android.AndroidEntryPoint
+import ru.daemonlord.messenger.ui.navigation.MessengerNavHost
 
+@AndroidEntryPoint
 class MainActivity : ComponentActivity() {
     override fun onCreate(savedInstanceState: Bundle?) {
         super.onCreate(savedInstanceState)
@@ -30,14 +27,5 @@ class MainActivity : ComponentActivity() {
 
 @Composable
 private fun AppRoot() {
-    Column(
-        modifier = Modifier
-            .fillMaxSize()
-            .padding(24.dp),
-        verticalArrangement = Arrangement.Center,
-        horizontalAlignment = Alignment.CenterHorizontally
-    ) {
-        Text(text = "Benya Messenger Android", style = MaterialTheme.typography.headlineSmall)
-        Text(text = "Phase 0 skeleton is ready.", style = MaterialTheme.typography.bodyMedium)
-    }
+    MessengerNavHost()
 }

android/app/src/main/java/ru/daemonlord/messenger/core/token/TokenBundle.kt

@@ -0,0 +1,7 @@
+package ru.daemonlord.messenger.core.token
+
+data class TokenBundle(
+    val accessToken: String,
+    val refreshToken: String,
+    val savedAtMillis: Long,
+)

android/app/src/main/java/ru/daemonlord/messenger/core/token/TokenRepository.kt

@@ -0,0 +1,10 @@
+package ru.daemonlord.messenger.core.token
+
+import kotlinx.coroutines.flow.Flow
+
+interface TokenRepository {
+    fun observeTokens(): Flow<TokenBundle?>
+    suspend fun getTokens(): TokenBundle?
+    suspend fun saveTokens(tokens: TokenBundle)
+    suspend fun clearTokens()
+}

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

@@ -0,0 +1,10 @@
+package ru.daemonlord.messenger.ui.auth
+
+data class AuthUiState(
+    val email: String = "",
+    val password: String = "",
+    val isCheckingSession: Boolean = true,
+    val isLoading: Boolean = false,
+    val isAuthenticated: Boolean = false,
+    val errorMessage: String? = null,
+)

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

@@ -0,0 +1,107 @@
+package ru.daemonlord.messenger.ui.auth
+
+import androidx.lifecycle.ViewModel
+import androidx.lifecycle.viewModelScope
+import dagger.hilt.android.lifecycle.HiltViewModel
+import kotlinx.coroutines.flow.MutableStateFlow
+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.LoginUseCase
+import ru.daemonlord.messenger.domain.auth.usecase.RestoreSessionUseCase
+import ru.daemonlord.messenger.domain.common.AppError
+import ru.daemonlord.messenger.domain.common.AppResult
+import javax.inject.Inject
+
+@HiltViewModel
+class AuthViewModel @Inject constructor(
+    private val restoreSessionUseCase: RestoreSessionUseCase,
+    private val loginUseCase: LoginUseCase,
+) : ViewModel() {
+
+    private val _uiState = MutableStateFlow(AuthUiState())
+    val uiState: StateFlow<AuthUiState> = _uiState.asStateFlow()
+
+    init {
+        restoreSession()
+    }
+
+    fun onEmailChanged(value: String) {
+        _uiState.update { it.copy(email = value, 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.") }
+            return
+        }
+
+        viewModelScope.launch {
+            _uiState.update { it.copy(isLoading = true, errorMessage = null) }
+            when (val result = loginUseCase(state.email.trim(), state.password)) {
+                is AppResult.Success -> {
+                    _uiState.update {
+                        it.copy(
+                            isLoading = false,
+                            isAuthenticated = true,
+                            errorMessage = null,
+                        )
+                    }
+                }
+
+                is AppResult.Error -> {
+                    _uiState.update {
+                        it.copy(
+                            isLoading = false,
+                            isAuthenticated = false,
+                            errorMessage = result.reason.toUiMessage(),
+                        )
+                    }
+                }
+            }
+        }
+    }
+
+    private fun restoreSession() {
+        viewModelScope.launch {
+            _uiState.update { it.copy(isCheckingSession = true) }
+            when (val result = restoreSessionUseCase()) {
+                is AppResult.Success -> {
+                    _uiState.update {
+                        it.copy(
+                            isCheckingSession = false,
+                            isAuthenticated = true,
+                            errorMessage = null,
+                        )
+                    }
+                }
+
+                is AppResult.Error -> {
+                    _uiState.update {
+                        it.copy(
+                            isCheckingSession = false,
+                            isAuthenticated = false,
+                            errorMessage = null,
+                        )
+                    }
+                }
+            }
+        }
+    }
+
+    private fun AppError.toUiMessage(): String {
+        return when (this) {
+            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.Unknown -> "Unknown error. Please try again."
+        }
+    }
+}

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

@@ -0,0 +1,95 @@
+package ru.daemonlord.messenger.ui.auth
+
+import androidx.compose.foundation.layout.Arrangement
+import androidx.compose.foundation.layout.Column
+import androidx.compose.foundation.layout.fillMaxSize
+import androidx.compose.foundation.layout.fillMaxWidth
+import androidx.compose.foundation.layout.padding
+import androidx.compose.material3.Button
+import androidx.compose.material3.CircularProgressIndicator
+import androidx.compose.material3.MaterialTheme
+import androidx.compose.material3.OutlinedTextField
+import androidx.compose.material3.Text
+import androidx.compose.material3.TextButton
+import androidx.compose.runtime.Composable
+import androidx.compose.ui.Alignment
+import androidx.compose.ui.Modifier
+import androidx.compose.ui.text.input.PasswordVisualTransformation
+import androidx.compose.ui.unit.dp
+
+@Composable
+fun LoginScreen(
+    state: AuthUiState,
+    onEmailChanged: (String) -> Unit,
+    onPasswordChanged: (String) -> Unit,
+    onLoginClick: () -> Unit,
+) {
+    Column(
+        modifier = Modifier
+            .fillMaxSize()
+            .padding(horizontal = 24.dp),
+        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),
+            )
+        } else {
+            TextButton(
+                onClick = {},
+                enabled = false,
+                modifier = Modifier.padding(top = 8.dp),
+            ) {
+                Text(text = "Use your existing backend account")
+            }
+        }
+    }
+}

android/app/src/main/java/ru/daemonlord/messenger/ui/chats/ChatsPlaceholderScreen.kt

@@ -0,0 +1,32 @@
+package ru.daemonlord.messenger.ui.chats
+
+import androidx.compose.foundation.layout.Arrangement
+import androidx.compose.foundation.layout.Column
+import androidx.compose.foundation.layout.fillMaxSize
+import androidx.compose.foundation.layout.padding
+import androidx.compose.material3.MaterialTheme
+import androidx.compose.material3.Text
+import androidx.compose.runtime.Composable
+import androidx.compose.ui.Alignment
+import androidx.compose.ui.Modifier
+import androidx.compose.ui.unit.dp
+
+@Composable
+fun ChatsPlaceholderScreen() {
+    Column(
+        modifier = Modifier
+            .fillMaxSize()
+            .padding(24.dp),
+        verticalArrangement = Arrangement.Center,
+        horizontalAlignment = Alignment.CenterHorizontally,
+    ) {
+        Text(
+            text = "Chats",
+            style = MaterialTheme.typography.headlineMedium,
+        )
+        Text(
+            text = "Phase 1 placeholder. Chats list comes next.",
+            style = MaterialTheme.typography.bodyMedium,
+        )
+    }
+}

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

@@ -0,0 +1,95 @@
+package ru.daemonlord.messenger.ui.navigation
+
+import androidx.compose.foundation.layout.Arrangement
+import androidx.compose.foundation.layout.Column
+import androidx.compose.foundation.layout.fillMaxSize
+import androidx.compose.material3.CircularProgressIndicator
+import androidx.compose.runtime.Composable
+import androidx.compose.runtime.LaunchedEffect
+import androidx.compose.runtime.collectAsState
+import androidx.compose.runtime.getValue
+import androidx.compose.ui.Alignment
+import androidx.compose.ui.Modifier
+import androidx.hilt.navigation.compose.hiltViewModel
+import androidx.navigation.NavGraph.Companion.findStartDestination
+import androidx.navigation.NavHostController
+import androidx.navigation.compose.NavHost
+import androidx.navigation.compose.composable
+import androidx.navigation.compose.navigation
+import androidx.navigation.compose.rememberNavController
+import ru.daemonlord.messenger.ui.auth.AuthViewModel
+import ru.daemonlord.messenger.ui.auth.LoginScreen
+import ru.daemonlord.messenger.ui.chats.ChatsPlaceholderScreen
+
+private object Routes {
+    const val AuthGraph = "auth_graph"
+    const val Login = "login"
+    const val Chats = "chats"
+}
+
+@Composable
+fun MessengerNavHost(
+    navController: NavHostController = rememberNavController(),
+    viewModel: AuthViewModel = hiltViewModel(),
+) {
+    val uiState by viewModel.uiState.collectAsState()
+
+    LaunchedEffect(uiState.isCheckingSession, uiState.isAuthenticated) {
+        if (uiState.isCheckingSession) {
+            return@LaunchedEffect
+        }
+        if (uiState.isAuthenticated) {
+            navController.navigate(Routes.Chats) {
+                popUpTo(navController.graph.findStartDestination().id) {
+                    inclusive = true
+                }
+                launchSingleTop = true
+            }
+        } else {
+            navController.navigate(Routes.Login) {
+                popUpTo(navController.graph.findStartDestination().id) {
+                    inclusive = true
+                }
+                launchSingleTop = true
+            }
+        }
+    }
+
+    NavHost(
+        navController = navController,
+        startDestination = Routes.AuthGraph,
+    ) {
+        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,
+                    )
+                }
+            }
+        }
+
+        composable(route = Routes.Chats) {
+            ChatsPlaceholderScreen()
+        }
+    }
+}
+
+@Composable
+private fun SessionCheckingScreen() {
+    Column(
+        modifier = Modifier.fillMaxSize(),
+        verticalArrangement = Arrangement.Center,
+        horizontalAlignment = Alignment.CenterHorizontally,
+    ) {
+        CircularProgressIndicator()
+    }
+}