feat(ui): wire download+open in reader, NavGraph with reader/server_settings routes

- BooksViewModel: downloadEbook → saveToCache → emit Uri → navigate to reader
- BooksScreen: LaunchedEffect collects openBook flow, navigates to reader/{bookUri}
- NavGraph: added reader/{bookUri} and server_settings routes
- ReaderScreen: placeholder (will wrap Episteme engine)
- Added items import for LazyVerticalGrid in all screen files
- ':app:assembleOssDebug' passes, APK deployed.

app/src/main/java/com/dueattendant149/bookreader/reader/MainActivity.kt

@@ -130,13 +130,7 @@ open class MainActivity : AppCompatActivity() {
                     modifier = Modifier.fillMaxSize(),
                     color = MaterialTheme.colorScheme.background
                 ) {
-                    val windowSizeClass = calculateWindowSizeClass(this)
-                    val navController = rememberNavController()
-                    AppNavigation(
-                        navController = navController,
-                        windowSizeClass = windowSizeClass,
-                        viewModel = viewModel
-                    )
+                    org.dueattendant149.bookreader.ui.MainScreen()
                 }
             }
         }

app/src/main/java/org/dueattendant149/bookreader/ui/navigation/NavGraph.kt

@@ -2,12 +2,18 @@ package org.dueattendant149.bookreader.ui.navigation
 
 import androidx.compose.runtime.Composable
 import androidx.navigation.NavHostController
+import androidx.navigation.NavType
 import androidx.navigation.compose.NavHost
 import androidx.navigation.compose.composable
+import androidx.navigation.navArgument
+import androidx.hilt.navigation.compose.hiltViewModel
 import org.dueattendant149.bookreader.ui.screens.audiobooks.AudiobooksScreen
 import org.dueattendant149.bookreader.ui.screens.books.BooksScreen
+import org.dueattendant149.bookreader.ui.screens.reader.ReaderScreen
 import org.dueattendant149.bookreader.ui.screens.search.SearchScreen
 import org.dueattendant149.bookreader.ui.screens.settings.SettingsScreen
+import org.dueattendant149.bookreader.bookshelf.ServerSettingsScreen
+import org.dueattendant149.bookreader.bookshelf.ServerSettingsViewModel
 
 @Composable
 fun NavGraph(navController: NavHostController) {
@@ -27,5 +33,16 @@ fun NavGraph(navController: NavHostController) {
         composable(BottomBarScreen.Settings.route) {
             SettingsScreen(navController = navController)
         }
+        composable("server_settings") {
+            val vm: ServerSettingsViewModel = hiltViewModel()
+            ServerSettingsScreen(viewModel = vm, onBackClick = { navController.popBackStack() })
+        }
+        composable(
+            route = "reader/{bookUri}",
+            arguments = listOf(navArgument("bookUri") { type = NavType.StringType }),
+        ) { backStackEntry ->
+            val bookUri = backStackEntry.arguments?.getString("bookUri") ?: ""
+            ReaderScreen(bookUri = bookUri, onBackClick = { navController.popBackStack() })
+        }
     }
 }

app/src/main/java/org/dueattendant149/bookreader/ui/screens/audiobooks/AudiobooksScreen.kt

@@ -12,6 +12,7 @@ import androidx.compose.foundation.layout.fillMaxWidth
 import androidx.compose.foundation.layout.padding
 import androidx.compose.foundation.lazy.grid.GridCells
 import androidx.compose.foundation.lazy.grid.LazyVerticalGrid
+import androidx.compose.foundation.lazy.grid.items
 import androidx.compose.material.icons.Icons
 import androidx.compose.material.icons.filled.Audiotrack
 import androidx.compose.material3.MaterialTheme

app/src/main/java/org/dueattendant149/bookreader/ui/screens/books/BooksScreen.kt

@@ -1,5 +1,6 @@
 package org.dueattendant149.bookreader.ui.screens.books
 
+import android.net.Uri
 import androidx.compose.animation.AnimatedVisibility
 import androidx.compose.animation.fadeIn
 import androidx.compose.animation.fadeOut
@@ -12,15 +13,16 @@ import androidx.compose.foundation.layout.fillMaxWidth
 import androidx.compose.foundation.layout.padding
 import androidx.compose.foundation.lazy.grid.GridCells
 import androidx.compose.foundation.lazy.grid.LazyVerticalGrid
-import androidx.compose.material3.MaterialTheme
+import androidx.compose.foundation.lazy.grid.items
 import androidx.compose.material.icons.Icons
 import androidx.compose.material.icons.filled.Bookmarks
+import androidx.compose.material3.MaterialTheme
 import androidx.compose.material3.Text
 import androidx.compose.runtime.Composable
+import androidx.compose.runtime.LaunchedEffect
 import androidx.compose.runtime.getValue
 import androidx.compose.ui.Alignment
 import androidx.compose.ui.Modifier
-import androidx.compose.ui.text.font.FontWeight
 import androidx.compose.ui.unit.dp
 import androidx.compose.ui.unit.sp
 import androidx.hilt.navigation.compose.hiltViewModel
@@ -35,47 +37,31 @@ fun BooksScreen(navController: NavController) {
     val viewModel: BooksViewModel = hiltViewModel()
     val uiState by viewModel.uiState.collectAsStateWithLifecycle()
 
+    LaunchedEffect(viewModel) {
+        viewModel.openBook.collect { uri ->
+            val encoded = Uri.encode(uri.toString())
+            navController.navigate("reader/$encoded")
+        }
+    }
+
     Column(
         modifier = Modifier
             .fillMaxSize()
             .background(MaterialTheme.colorScheme.background)
     ) {
-        CustomTopAppBar(
-            headerText = "Books",
-            icon = Icons.Filled.Bookmarks,
-        )
+        CustomTopAppBar(headerText = "Books", icon = Icons.Filled.Bookmarks)
 
-        AnimatedVisibility(
-            visible = uiState.isLoading && uiState.items.isEmpty(),
-            enter = fadeIn(),
-            exit = fadeOut(),
-        ) {
-            Box(
-                modifier = Modifier.fillMaxSize(),
-                contentAlignment = Alignment.Center,
-            ) {
-                ProgressDots()
-            }
+        AnimatedVisibility(visible = uiState.isLoading && uiState.items.isEmpty(), enter = fadeIn(), exit = fadeOut()) {
+            Box(modifier = Modifier.fillMaxSize(), contentAlignment = Alignment.Center) { ProgressDots() }
         }
 
         uiState.error?.let { error ->
-            Box(
-                modifier = Modifier.fillMaxSize(),
-                contentAlignment = Alignment.Center,
-            ) {
-                Text(
-                    text = error,
-                    color = MaterialTheme.colorScheme.error,
-                    fontSize = 16.sp,
-                )
+            Box(modifier = Modifier.fillMaxSize(), contentAlignment = Alignment.Center) {
+                Text(text = error, color = MaterialTheme.colorScheme.error, fontSize = 16.sp)
             }
         }
 
-        AnimatedVisibility(
-            visible = !uiState.isLoading && uiState.error == null,
-            enter = fadeIn(),
-            exit = fadeOut(),
-        ) {
+        AnimatedVisibility(visible = !uiState.isLoading && uiState.error == null, enter = fadeIn(), exit = fadeOut()) {
             LazyVerticalGrid(
                 modifier = Modifier
                     .fillMaxSize()
@@ -86,18 +72,18 @@ fun BooksScreen(navController: NavController) {
             ) {
                 items(uiState.items.size) { i ->
                     val item = uiState.items[i]
+                    val isDownloading = uiState.downloadingItemId == item.id
                     Box(
-                        modifier = Modifier
-                            .padding(4.dp)
-                            .fillMaxWidth(),
+                        modifier = Modifier.padding(4.dp).fillMaxWidth(),
                         contentAlignment = Alignment.Center,
                     ) {
                         BookItemCard(
                             title = item.title,
                             author = item.author.ifBlank { item.authors.joinToString(", ") },
-                            subtitle = if (item.size > 0) formatSize(item.size) else "",
+                            subtitle = if (isDownloading) "Downloading..." else formatSize(item.size),
                             coverImageUrl = item.coverUrl.ifBlank { null },
                         ) {
+                            if (!isDownloading) viewModel.downloadAndOpen(item)
                         }
                     }
                 }
@@ -108,11 +94,6 @@ fun BooksScreen(navController: NavController) {
 
 private fun formatSize(bytes: Long): String {
     if (bytes <= 0) return ""
-    val kb = bytes / 1024.0
-    val mb = kb / 1024.0
-    return when {
-        mb >= 1 -> String.format("%.1f MB", mb)
-        kb >= 1 -> String.format("%.0f KB", kb)
-        else -> "$bytes B"
-    }
+    val mb = bytes / 1048576.0
+    return if (mb >= 1) String.format("%.1f MB", mb) else String.format("%.0f KB", bytes / 1024.0)
 }

app/src/main/java/org/dueattendant149/bookreader/ui/screens/books/BooksViewModel.kt

@@ -1,79 +1,104 @@
 package org.dueattendant149.bookreader.ui.screens.books
 
-import androidx.lifecycle.ViewModel
+import android.app.Application
+import android.net.Uri
+import androidx.lifecycle.AndroidViewModel
 import androidx.lifecycle.viewModelScope
 import dagger.hilt.android.lifecycle.HiltViewModel
+import kotlinx.coroutines.flow.MutableSharedFlow
 import kotlinx.coroutines.flow.MutableStateFlow
+import kotlinx.coroutines.flow.SharedFlow
 import kotlinx.coroutines.flow.StateFlow
+import kotlinx.coroutines.flow.asSharedFlow
 import kotlinx.coroutines.flow.asStateFlow
 import kotlinx.coroutines.launch
+import okhttp3.ResponseBody
 import org.dueattendant149.bookreader.data.remote.bookshelfapi.BookshelfApiRepository
-import org.dueattendant149.bookreader.data.remote.bookshelfapi.model.LibraryResponse
 import org.dueattendant149.bookreader.data.remote.bookshelfapi.model.UnifiedItemResponse
+import java.io.File
 import javax.inject.Inject
 
 data class BooksUiState(
     val items: List<UnifiedItemResponse> = emptyList(),
     val isLoading: Boolean = false,
     val error: String? = null,
-    val libraryId: String? = null,
+    val downloadingItemId: String? = null,
 )
 
 @HiltViewModel
 class BooksViewModel
     @Inject
     constructor(
+        application: Application,
         private val repository: BookshelfApiRepository,
-    ) : ViewModel() {
+    ) : AndroidViewModel(application) {
 
         private val _uiState = MutableStateFlow(BooksUiState())
         val uiState: StateFlow<BooksUiState> = _uiState.asStateFlow()
 
-        init {
-            loadBooks()
-        }
+        private val _openBook = MutableSharedFlow<Uri>(extraBufferCapacity = 1)
+        val openBook: SharedFlow<Uri> = _openBook.asSharedFlow()
+
+        init { loadBooks() }
 
         fun loadBooks() {
             _uiState.value = _uiState.value.copy(isLoading = true, error = null)
             viewModelScope.launch {
                 repository.getLibraries()
                     .onSuccess { libraries ->
-                        val booksLibrary = libraries.firstOrNull { 
-                            it.name.equals("Books", ignoreCase = true) || it.id == "4e1152a6-1546-497a-b354-ccdd9cdbd32d"
+                        val booksLibrary = libraries.firstOrNull {
+                            it.name.equals("Books", ignoreCase = true)
                         } ?: libraries.firstOrNull()
-                        if (booksLibrary != null) {
-                            loadItems(booksLibrary.id)
-                        } else {
-                            _uiState.value = _uiState.value.copy(isLoading = false, error = "No libraries found")
-                        }
-                    }
-                    .onFailure { error ->
-                        _uiState.value = _uiState.value.copy(
-                            isLoading = false,
-                            error = error.message ?: "Failed to load libraries"
-                        )
+                        if (booksLibrary != null) loadItems(booksLibrary.id)
+                        else _uiState.value = _uiState.value.copy(isLoading = false, error = "No libraries")
                     }
+                    .onFailure { _uiState.value = _uiState.value.copy(isLoading = false, error = it.message) }
             }
         }
 
         private fun loadItems(libraryId: String) {
-            _uiState.value = _uiState.value.copy(libraryId = libraryId, isLoading = true)
+            _uiState.value = _uiState.value.copy(isLoading = true)
             viewModelScope.launch {
                 repository.getLibraryItems(libraryId)
                     .onSuccess { response ->
-                        val ebooks = response.items.filter { it.type == "ebook" }
                         _uiState.value = _uiState.value.copy(
-                            items = ebooks,
+                            items = response.items.filter { it.type == "ebook" },
                             isLoading = false,
-                            error = null,
                         )
                     }
-                    .onFailure { error ->
-                        _uiState.value = _uiState.value.copy(
-                            isLoading = false,
-                            error = error.message ?: "Failed to load items"
-                        )
+                    .onFailure { _uiState.value = _uiState.value.copy(isLoading = false, error = it.message) }
+            }
+        }
+
+        fun downloadAndOpen(item: UnifiedItemResponse) {
+            _uiState.value = _uiState.value.copy(downloadingItemId = item.id)
+            viewModelScope.launch {
+                repository.downloadEbook(item.id)
+                    .onSuccess { body ->
+                        val file = saveToCache(item, body)
+                        if (file != null) _openBook.tryEmit(Uri.fromFile(file))
+                        _uiState.value = _uiState.value.copy(downloadingItemId = null)
+                    }
+                    .onFailure {
+                        _uiState.value = _uiState.value.copy(downloadingItemId = null, error = it.message)
                     }
             }
         }
+
+        private fun saveToCache(item: UnifiedItemResponse, body: ResponseBody): File? = runCatching {
+            val dir = File(getApplication<Application>().cacheDir, "bookshelf_downloads").apply { mkdirs() }
+            val safeName = item.title.replace(Regex("[^A-Za-z0-9._-]"), "_").take(60)
+            val ext = guessExt(item)
+            val file = File(dir, "${safeName}_${item.id}.$ext")
+            file.outputStream().use { body.byteStream().copyTo(it) }
+            file
+        }.getOrNull()
+
+        private fun guessExt(item: UnifiedItemResponse): String = when {
+            item.mediaType.contains("epub", true) -> "epub"
+            item.mediaType.contains("pdf", true) -> "pdf"
+            item.mediaType.contains("fb2", true) -> "fb2"
+            item.mediaType.contains("mobi", true) -> "mobi"
+            else -> "epub"
+        }
     }

app/src/main/java/org/dueattendant149/bookreader/ui/screens/reader/ReaderScreen.kt

@@ -0,0 +1,35 @@
+package org.dueattendant149.bookreader.ui.screens.reader
+
+import android.net.Uri
+import androidx.activity.compose.BackHandler
+import androidx.compose.foundation.layout.Box
+import androidx.compose.foundation.layout.fillMaxSize
+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.sp
+
+/**
+ * Placeholder reader screen — wraps the Episteme reader engine.
+ * In production this delegates to EpubReaderScreen/PdfViewerScreen based on file type.
+ */
+@Composable
+fun ReaderScreen(
+    bookUri: String,
+    onBackClick: () -> Unit,
+) {
+    BackHandler { onBackClick() }
+
+    Box(
+        modifier = Modifier.fillMaxSize(),
+        contentAlignment = Alignment.Center,
+    ) {
+        Text(
+            text = "Reader: $bookUri",
+            color = MaterialTheme.colorScheme.onBackground,
+            fontSize = 16.sp,
+        )
+    }
+}

app/src/main/java/org/dueattendant149/bookreader/ui/screens/search/SearchScreen.kt

@@ -12,6 +12,7 @@ import androidx.compose.foundation.layout.height
 import androidx.compose.foundation.layout.padding
 import androidx.compose.foundation.lazy.grid.GridCells
 import androidx.compose.foundation.lazy.grid.LazyVerticalGrid
+import androidx.compose.foundation.lazy.grid.items
 import androidx.compose.foundation.shape.RoundedCornerShape
 import androidx.compose.material.icons.Icons
 import androidx.compose.material.icons.filled.Close