/*
 * mygram-droid: Android TV client for Foldergram.
 * Copyright (C) 2026 Danilo M. <danix@danix.xyz>
 *
 * This program is free software; you can redistribute it and/or modify it
 * under the terms of the GNU General Public License version 2 as published
 * by the Free Software Foundation.
 *
 * 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 General Public License
 * for more details.
 */


package mygram.droid;

import android.app.Activity;
import android.content.Context;
import android.content.Intent;
import android.os.Bundle;
import android.view.Gravity;
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.ArrayList;
import java.util.List;
import java.util.concurrent.Callable;

/** 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)
				.putExtra("count", f.count));
	}

	@Override
	protected void onCreate(Bundle state) {
		super.onCreate(state);
		LinearLayout column = new LinearLayout(this);
		column.setOrientation(LinearLayout.VERTICAL);
		LinearLayout header = new LinearLayout(this);
		header.setGravity(Gravity.CENTER_VERTICAL);
		int p = Ui.dp(this, 16);
		header.setPadding(p * 2, p, p * 2, 0);
		header.addView(Ui.iconButton(this, R.drawable.ic_arrow_back, "Back", v -> finish()));
		TextView title = Ui.text(this, getIntent().getStringExtra("name"), 24);
		title.setPadding(p, 0, 0, 0);
		header.addView(title);
		column.addView(header);
		content = new FrameLayout(this);
		column.addView(content, new LinearLayout.LayoutParams(ViewGroup.LayoutParams.MATCH_PARENT, 0, 1));
		setContentView(column);
		show(Ui.text(this, "Loading…", 18));
		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 -> {
			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) {
			addTiles(); // the viewer may have appended to the shared list
			grid.getAdapter().notifyItemRangeChanged(0, grid.getAdapter().getItemCount());
		}
	}

	private void show(android.view.View v) {
		content.removeAllViews();
		content.addView(v);
	}
}