1 files changed, 74 insertions, 8 deletions

diff --git a/app/src/main/java/mygram/droid/FolderActivity.java b/app/src/main/java/mygram/droid/FolderActivity.java
index 10a9940..c7002c5 100644
--- a/app/src/main/java/mygram/droid/FolderActivity.java
+++ b/app/src/main/java/mygram/droid/FolderActivity.java
@@ -23,18 +23,27 @@ import android.view.ViewGroup;
 import android.widget.FrameLayout;
 import android.widget.LinearLayout;
 import android.widget.TextView;
+import android.widget.Toast;
 
+import androidx.recyclerview.widget.GridLayoutManager;
 import androidx.recyclerview.widget.RecyclerView;
 
-import java.util.Collections;
+import java.util.ArrayList;
+import java.util.List;
+import java.util.concurrent.Callable;
 
-/** One folder as a grid, shuffled once per open. */
+/** One folder as a grid, paged in lazily in random page order. */
 public final class FolderActivity extends Activity {
 	private FrameLayout content;
 	private RecyclerView grid;
+	private final List<Post> posts = new ArrayList<>();
+	private final List<TileAdapter.Tile> tiles = new ArrayList<>();
+	private Callable<List<Post>> more;
+	private boolean loading;
 
 	static void open(Context c, Api.Folder f) {
-		c.startActivity(new Intent(c, FolderActivity.class).putExtra("slug", f.slug).putExtra("name", f.name));
+		c.startActivity(new Intent(c, FolderActivity.class).putExtra("slug", f.slug).putExtra("name", f.name)
+				.putExtra("count", f.count));
 	}
 
 	@Override
@@ -49,19 +58,76 @@ public final class FolderActivity extends Activity {
 		column.addView(content, new LinearLayout.LayoutParams(ViewGroup.LayoutParams.MATCH_PARENT, 0, 1));
 		setContentView(column);
 		show(Ui.text(this, "Loading…", 18));
-		Api.async(() -> Api.folderPosts(getIntent().getStringExtra("slug")), posts -> {
-			Collections.shuffle(posts);
-			grid = Ui.grid(this, Ui.postTiles(this, posts), Ui.POST_W, Ui.POST_H, 6);
+		more = Api.folderPages(getIntent().getStringExtra("slug"), getIntent().getIntExtra("count", 0));
+		loading = true;
+		Api.async(more, page -> {
+			loading = false;
+			if (isDestroyed())
+				return;
+			append(page);
+			if (page.isEmpty()) {
+				show(Ui.text(this, "Nothing to show", 18));
+				return;
+			}
+			grid = Ui.grid(this, tiles, Ui.POST_W, Ui.POST_H, 6);
+			grid.addOnScrollListener(new RecyclerView.OnScrollListener() {
+				@Override
+				public void onScrolled(RecyclerView rv, int dx, int dy) {
+					loadMore();
+				}
+			});
 			show(grid);
 			grid.post(grid::requestFocus); // after layout
-		}, e -> show(Ui.text(this, "Cannot load folder: " + e.getMessage(), 18)));
+		}, e -> {
+			loading = false;
+			show(Ui.text(this, "Cannot load folder: " + e.getMessage(), 18));
+		});
+	}
+
+	/** Loads the next page when the last visible tile is within 12 of the end. */
+	private void loadMore() {
+		if (more == null || loading || grid == null)
+			return;
+		if (((GridLayoutManager) grid.getLayoutManager()).findLastVisibleItemPosition() < tiles.size() - 12)
+			return;
+		loading = true;
+		Api.async(more, page -> {
+			loading = false;
+			if (isDestroyed())
+				return;
+			if (page.isEmpty())
+				more = null;
+			append(page);
+		}, e -> {
+			loading = false;
+			if (!isDestroyed())
+				Toast.makeText(this, "Cannot load more: " + e.getMessage(), Toast.LENGTH_SHORT).show();
+		});
+	}
+
+	/** Pages from one pager never overlap, so no id check is needed here. */
+	private void append(List<Post> page) {
+		posts.addAll(page);
+		addTiles();
+	}
+
+	private void addTiles() {
+		int old = tiles.size();
+		for (int i = old; i < posts.size(); i++) {
+			int start = i;
+			tiles.add(TileAdapter.post(posts.get(i), () -> Playlist.open(this, posts, start, more)));
+		}
+		if (grid != null && tiles.size() > old)
+			grid.getAdapter().notifyItemRangeInserted(old, tiles.size() - old);
 	}
 
 	@Override
 	protected void onResume() {
 		super.onResume();
-		if (grid != null && grid.getAdapter() != null)
+		if (grid != null && grid.getAdapter() != null) {
+			addTiles(); // the viewer may have appended to the shared list
 			grid.getAdapter().notifyItemRangeChanged(0, grid.getAdapter().getItemCount());
+		}
 	}
 
 	private void show(android.view.View v) {