android/app/src/main/java/com/fabledsword/minstrel/library/ui/BrowseViewModel.kt

@@ -240,6 +240,11 @@ fun visibleGenres(
     }
 }
 
+// Integer division by this floors a year to its decade: 2007 -> 2000. Named
+// because detekt counts it as magic, and because the arithmetic reads as
+// arbitrary otherwise.
+private const val YEARS_PER_DECADE = 10
+
 /** A decade's worth of the year index, newest year first. */
 data class DecadeGroup(
     val decade: Int,
@@ -255,7 +260,7 @@ data class DecadeGroup(
  * same reason as [visibleGenres].
  */
 fun groupByDecade(years: List<YearCount>): List<DecadeGroup> =
-    years.groupBy { (it.year / 10) * 10 }
+    years.groupBy { (it.year / YEARS_PER_DECADE) * YEARS_PER_DECADE }
         .map { (decade, entries) ->
             DecadeGroup(
                 decade = decade,

android/app/src/main/java/com/fabledsword/minstrel/library/ui/LibraryScreen.kt

@@ -117,26 +117,40 @@ fun LibraryScreen(
             state = pagerState,
             modifier = Modifier.fillMaxSize().padding(inner),
         ) { page ->
-            when (page) {
+            LibraryTabPage(page = page, viewModel = viewModel, navController = navController)
-                TAB_ARTISTS -> ArtistsTab(viewModel = viewModel, navController = navController)
-                TAB_ALBUMS -> AlbumsTab(viewModel = viewModel, navController = navController)
-                TAB_GENRES -> GenresTab(
-                    onAlbumClick = { id -> navController.navigate(AlbumDetail(id)) },
-                )
-                TAB_YEARS -> YearsTab(
-                    onAlbumClick = { id -> navController.navigate(AlbumDetail(id)) },
-                )
-                TAB_HISTORY -> HistoryTab(
-                    onNavigateToAlbum = { id -> navController.navigate(AlbumDetail(id)) },
-                    onNavigateToArtist = { id -> navController.navigate(ArtistDetail(id)) },
-                )
-                TAB_LIKED -> LikedTab(navController = navController)
-                TAB_HIDDEN -> HiddenTab()
-            }
         }
     }
 }
 
+/**
+ * The pager's page bodies, split out of [LibraryScreen] so the screen stays
+ * the scaffold + tab bar and this stays the routing table. Adding a tab is
+ * then one line here and one label in [LIBRARY_TABS].
+ */
+@Composable
+private fun LibraryTabPage(
+    page: Int,
+    viewModel: LibraryViewModel,
+    navController: NavHostController,
+) {
+    when (page) {
+        TAB_ARTISTS -> ArtistsTab(viewModel = viewModel, navController = navController)
+        TAB_ALBUMS -> AlbumsTab(viewModel = viewModel, navController = navController)
+        TAB_GENRES -> GenresTab(
+            onAlbumClick = { id -> navController.navigate(AlbumDetail(id)) },
+        )
+        TAB_YEARS -> YearsTab(
+            onAlbumClick = { id -> navController.navigate(AlbumDetail(id)) },
+        )
+        TAB_HISTORY -> HistoryTab(
+            onNavigateToAlbum = { id -> navController.navigate(AlbumDetail(id)) },
+            onNavigateToArtist = { id -> navController.navigate(ArtistDetail(id)) },
+        )
+        TAB_LIKED -> LikedTab(navController = navController)
+        TAB_HIDDEN -> HiddenTab()
+    }
+}
+
 private const val TAB_ARTISTS = 0
 private const val TAB_ALBUMS = 1
 private const val TAB_GENRES = 2