feat(plugin): add login prompt for metadata plugin access and implement authentication view model

composeApp/src/commonMain/composeResources/values/strings.xml

@@ -630,6 +630,12 @@
     <string name="media_user">User</string>
     <string name="media_playlist">Playlist</string>
 
+    <!-- Login required -->
+    <string name="login_required_title">Sign in to continue</string>
+    <string name="login_required_description">This part of Spotube needs you to be signed in with your music provider. Sign in once and everything will show up here.</string>
+    <string name="login_required_description_plugin">%1$s needs you to sign in before it can show this. Sign in once and everything will show up here.</string>
+    <string name="login_required_action">Sign in</string>
+
     <!-- Error display -->
     <string name="error_title">We\'re Truly Sorry</string>
     <string name="error_description">Something isn\'t working right now. Your experience matters to us, and we\'re doing our best to fix this. Please try again or check the error details below.</string>

composeApp/src/commonMain/kotlin/dev/krtirtho/spotube/core/di/Modules.kt

@@ -54,6 +54,7 @@ import dev.krtirtho.spotube.modules.downloads.DownloadManager
 import dev.krtirtho.spotube.modules.downloads.DownloadsViewModel
 import dev.krtirtho.spotube.modules.home.HomeScreenRepository
 import dev.krtirtho.spotube.modules.home.HomeScreenViewModel
+import dev.krtirtho.spotube.modules.plugin.MetadataAuthViewModel
 import dev.krtirtho.spotube.modules.library.LibraryRepository
 import dev.krtirtho.spotube.modules.library.LibraryState
 import dev.krtirtho.spotube.modules.library.album.LibraryAlbumsViewModel
@@ -116,6 +117,7 @@ val sharedModules = module {
     // Home
     singleOf(::HomeScreenRepository)
     viewModelOf(::HomeScreenViewModel)
+    viewModelOf(::MetadataAuthViewModel)
 
     // Search
     singleOf(::SearchRepository)

composeApp/src/commonMain/kotlin/dev/krtirtho/spotube/core/ui/component/ErrorDisplay.kt

@@ -50,6 +50,9 @@ import dev.krtirtho.spotube.core.ui.theming.AppTheme
 import com.composeunstyled.Text
 
 import androidx.compose.runtime.Composable
+import androidx.lifecycle.compose.collectAsStateWithLifecycle
+import dev.krtirtho.spotube.modules.plugin.MetadataAuthViewModel
+import org.koin.compose.viewmodel.koinViewModel
 import androidx.compose.runtime.getValue
 import androidx.compose.runtime.mutableStateOf
 import androidx.compose.runtime.remember
@@ -77,7 +80,16 @@ import spotube.composeapp.generated.resources.*
 fun ErrorDisplay(
     errorMessage: String,
     onRetry: () -> Unit,
-    modifier: Modifier = Modifier) {
+    modifier: Modifier = Modifier,
+    authViewModel: MetadataAuthViewModel = koinViewModel()) {
+    val authState by authViewModel.uiState.collectAsStateWithLifecycle()
+    if (authState.loginRequired) {
+        LoginRequiredDisplay(
+            pluginName = authState.pluginName,
+            onLogin = authViewModel::login,
+            modifier = modifier)
+        return
+    }
     var showFullLog by remember { mutableStateOf(false) }
     val clipboardManager = LocalClipboardManager.current
 
@@ -242,16 +254,6 @@ private fun ErrorLogDialog(
     }
 }
 
-@Preview
-@Composable
-private fun ErrorDisplayPreview() {
-    Box(modifier = Modifier.fillMaxSize().background(AppTheme.colors.background)) {
-        ErrorDisplay(
-            errorMessage = "This is an error message",
-            onRetry = {})
-    }
-}
-
 @Preview
 @Composable
 private fun ErrorLogDialogPreview() {

composeApp/src/commonMain/kotlin/dev/krtirtho/spotube/core/ui/component/LoginRequiredDisplay.kt

@@ -0,0 +1,101 @@
+/*
+ * Copyright (C) 2026 Kingkor Roy Tirtho and Spotube Contributors
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU Affero General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU Affero General Public License for more details.
+ *
+ * You should have received a copy of the GNU Affero General Public License
+ * along with this program.  If not, see <https://www.gnu.org/licenses/>.
+ */
+
+package dev.krtirtho.spotube.core.ui.component
+
+import androidx.compose.foundation.background
+import androidx.compose.foundation.layout.Arrangement
+import androidx.compose.foundation.layout.Box
+import androidx.compose.foundation.layout.Column
+import androidx.compose.foundation.layout.Row
+import androidx.compose.foundation.layout.fillMaxWidth
+import androidx.compose.foundation.layout.height
+import androidx.compose.foundation.layout.padding
+import androidx.compose.foundation.layout.size
+import androidx.compose.foundation.shape.CircleShape
+import androidx.compose.runtime.Composable
+import androidx.compose.ui.Alignment
+import androidx.compose.ui.Modifier
+import androidx.compose.ui.draw.clip
+import androidx.compose.ui.text.font.FontWeight
+import androidx.compose.ui.text.style.TextAlign
+import androidx.compose.ui.unit.dp
+import com.composeunstyled.Text
+import compose.icons.FeatherIcons
+import compose.icons.feathericons.Lock
+import compose.icons.feathericons.LogIn
+import dev.krtirtho.spotube.core.ui.theming.AppTheme
+import org.jetbrains.compose.resources.stringResource
+import org.spotube.millennium.composables.MillenniumButton
+import org.spotube.millennium.composables.MillenniumIcon
+import spotube.composeapp.generated.resources.*
+
+/** Friendly "sign in first" state for screens whose metadata plugin needs an account. */
+@Composable
+fun LoginRequiredDisplay(
+    pluginName: String?,
+    onLogin: () -> Unit,
+    modifier: Modifier = Modifier) {
+    Column(
+        modifier = modifier
+            .fillMaxWidth()
+            .padding(horizontal = 32.dp, vertical = 24.dp),
+        horizontalAlignment = Alignment.CenterHorizontally,
+        verticalArrangement = Arrangement.spacedBy(16.dp)) {
+        Box(
+            modifier = Modifier
+                .size(88.dp)
+                .clip(CircleShape)
+                .background(AppTheme.colors.primary.copy(alpha = 0.14f)),
+            contentAlignment = Alignment.Center) {
+            MillenniumIcon(
+                imageVector = FeatherIcons.Lock,
+                contentDescription = null,
+                modifier = Modifier.size(40.dp),
+                tint = AppTheme.colors.primary)
+        }
+
+        Text(
+            text = stringResource(Res.string.login_required_title),
+            style = AppTheme.typography.headlineSmall,
+            fontWeight = FontWeight.Bold,
+            color = AppTheme.colors.onSurface,
+            textAlign = TextAlign.Center)
+
+        Text(
+            text = if (pluginName.isNullOrBlank()) {
+                stringResource(Res.string.login_required_description)
+            } else {
+                stringResource(Res.string.login_required_description_plugin, pluginName)
+            },
+            style = AppTheme.typography.bodyMedium,
+            color = AppTheme.colors.onSurfaceVariant,
+            textAlign = TextAlign.Center)
+
+        MillenniumButton(
+            onClick = onLogin,
+            modifier = Modifier.height(44.dp)) {
+            Row(verticalAlignment = Alignment.CenterVertically) {
+                MillenniumIcon(
+                    imageVector = FeatherIcons.LogIn,
+                    contentDescription = null,
+                    modifier = Modifier.padding(end = 8.dp).size(18.dp))
+                Text(stringResource(Res.string.login_required_action))
+            }
+        }
+    }
+}

composeApp/src/commonMain/kotlin/dev/krtirtho/spotube/modules/library/LibraryScreen.kt

@@ -117,7 +117,7 @@ fun LibraryScreen(libraryState: LibraryState = koinInject()) {
         }
         Column(Modifier.weight(1f).padding(horizontal = 12.dp)) {
             when (state.currentTab) {
-                LibraryTab.Playlists -> MetadataPluginGuard(showTopBar = false) {
+                LibraryTab.Playlists -> MetadataPluginGuard(showTopBar = false, requireLogin = true) {
                     LibraryPlaylistsScreen(
                         showCreatePlaylist = state.showCreatePlaylist,
                         onDismissCreatePlaylist = libraryState::dismissCreatePlaylist,
@@ -125,10 +125,10 @@ fun LibraryScreen(libraryState: LibraryState = koinInject()) {
                     )
                 }
 
-                LibraryTab.Albums -> MetadataPluginGuard(showTopBar = false) {
+                LibraryTab.Albums -> MetadataPluginGuard(showTopBar = false, requireLogin = true) {
                     LibraryAlbumsScreen(viewMode = viewMode)
                 }
-                LibraryTab.Artists -> MetadataPluginGuard(showTopBar = false) {
+                LibraryTab.Artists -> MetadataPluginGuard(showTopBar = false, requireLogin = true) {
                     LibraryArtistsScreen(viewMode = viewMode)
                 }
                 LibraryTab.LocalTracks -> LibraryLocalTracksScreen()

composeApp/src/commonMain/kotlin/dev/krtirtho/spotube/modules/plugin/MetadataAuthViewModel.kt

@@ -0,0 +1,80 @@
+/*
+ * Copyright (C) 2026 Kingkor Roy Tirtho and Spotube Contributors
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU Affero General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU Affero General Public License for more details.
+ *
+ * You should have received a copy of the GNU Affero General Public License
+ * along with this program.  If not, see <https://www.gnu.org/licenses/>.
+ */
+
+package dev.krtirtho.spotube.modules.plugin
+
+import androidx.lifecycle.ViewModel
+import androidx.lifecycle.viewModelScope
+import dev.krtirtho.spotube.core.di.injectLogger
+import kotlinx.coroutines.CancellationException
+import kotlinx.coroutines.ExperimentalCoroutinesApi
+import kotlinx.coroutines.flow.Flow
+import kotlinx.coroutines.flow.SharingStarted
+import kotlinx.coroutines.flow.StateFlow
+import kotlinx.coroutines.flow.combine
+import kotlinx.coroutines.flow.flatMapLatest
+import kotlinx.coroutines.flow.flow
+import kotlinx.coroutines.flow.flowOf
+import kotlinx.coroutines.flow.stateIn
+import org.koin.core.component.KoinComponent
+
+data class MetadataAuthUiState(
+    /** True when the selected metadata plugin needs an account and the user isn't signed in. */
+    val loginRequired: Boolean = false,
+    val pluginName: String? = null)
+
+/**
+ * Tells screens whether the selected metadata plugin is waiting for a login, so they can show a
+ * friendly sign-in prompt instead of surfacing the plugin's raw authorization exception.
+ */
+@OptIn(ExperimentalCoroutinesApi::class)
+class MetadataAuthViewModel(
+    private val pluginManager: PluginManager) : ViewModel(), KoinComponent {
+    private val logger by injectLogger<MetadataAuthViewModel>()
+
+    val uiState: StateFlow<MetadataAuthUiState> = combine(
+        pluginManager.selectedMetadataPlugin.flatMapLatest { service ->
+            if (service == null) flowOf(false) else loginRequiredFlow(service)
+        },
+        pluginManager.state) { loginRequired, managerState ->
+        val name = (managerState as? PluginManagerStates.Data)
+            ?.selectedPlugins?.get(PluginAbility.METADATA)?.name
+        MetadataAuthUiState(loginRequired = loginRequired, pluginName = name)
+    }.stateIn(viewModelScope, SharingStarted.WhileSubscribed(5_000), MetadataAuthUiState())
+
+    private fun loginRequiredFlow(service: dev.krtirtho.spotube.core.zipline.PluginService): Flow<Boolean> = flow {
+        val requiresAuth = try {
+            service.use { coreAPI.requiresAuthentication }
+        } catch (e: Exception) {
+            if (e is CancellationException) throw e
+            false
+        }
+        if (!requiresAuth) {
+            emit(false)
+        } else {
+            service.loggedInFlow.collect { emit(!it) }
+        }
+    }
+
+    fun login() {
+        val service = pluginManager.selectedMetadataPlugin.value ?: return
+        pluginManager.launchTask {
+            runCatching { service.use { coreAPI.login() } }
+                .onFailure { logger.e(it) { "Metadata plugin login failed" } }
+        }
+    }
+}

composeApp/src/commonMain/kotlin/dev/krtirtho/spotube/modules/plugin/guard/MetadataPluginGuard.kt

@@ -43,6 +43,8 @@ import androidx.compose.ui.unit.dp
 import androidx.lifecycle.compose.collectAsStateWithLifecycle
 import com.composeunstyled.Text
 import dev.krtirtho.spotube.core.ui.component.ApplicationMainBar
+import dev.krtirtho.spotube.core.ui.component.LoginRequiredDisplay
+import dev.krtirtho.spotube.modules.plugin.MetadataAuthViewModel
 import dev.krtirtho.spotube.core.ui.theming.AppTheme
 import dev.krtirtho.spotube.modules.shell.LocalAppShellBottomInset
 import dev.krtirtho.spotube.resources.iconsax.Iconsax
@@ -76,19 +78,42 @@ import spotube.composeapp.generated.resources.no_metadata_plugin_title
  * the screen sit on an endless loading skeleton.
  *
  * @param backButton whether the placeholder's top bar shows a back button (for pushed screens).
+ * @param requireLogin also swap [content] for a friendly sign-in prompt while the plugin needs an
+ * account and the user isn't signed in (for screens that only make sense when logged in).
  * @param showTopBar false when the host screen already draws its own app bar (e.g. Library tabs).
  */
 @Composable
 fun MetadataPluginGuard(
     backButton: Boolean = false,
     showTopBar: Boolean = true,
+    requireLogin: Boolean = false,
     viewModel: MetadataPluginGuardViewModel = koinViewModel(),
+    authViewModel: MetadataAuthViewModel = koinViewModel(),
     content: @Composable () -> Unit
 ) {
     val state by viewModel.uiState.collectAsStateWithLifecycle()
+    val authState by authViewModel.uiState.collectAsStateWithLifecycle()
 
     when (val s = state) {
-        is MetadataPluginGuardState.Available -> content()
+        is MetadataPluginGuardState.Available ->
+            if (requireLogin && authState.loginRequired) {
+                Column(Modifier.fillMaxSize().background(MillenniumTheme.colors.background)) {
+                    if (showTopBar) ApplicationMainBar(backButton = backButton)
+                    Box(
+                        Modifier
+                            .fillMaxSize()
+                            .verticalScroll(rememberScrollState())
+                            .padding(bottom = LocalAppShellBottomInset.current),
+                        contentAlignment = Alignment.Center) {
+                        LoginRequiredDisplay(
+                            pluginName = authState.pluginName,
+                            onLogin = authViewModel::login,
+                            modifier = Modifier.widthIn(max = 420.dp))
+                    }
+                }
+            } else {
+                content()
+            }
         is MetadataPluginGuardState.Loading -> Box(
             Modifier.fillMaxSize().background(MillenniumTheme.colors.background))
         is MetadataPluginGuardState.Missing -> NoMetadataPluginScreen(