/*
 * 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.graphics.Color;
import android.graphics.drawable.Drawable;
import android.media.MediaMetadataRetriever;
import android.os.Bundle;
import android.os.Handler;
import android.os.Looper;
import android.os.SystemClock;
import android.view.Gravity;
import android.view.KeyEvent;
import android.view.View;
import android.view.ViewGroup;
import android.view.WindowManager;
import android.widget.FrameLayout;
import android.widget.ImageView;
import android.widget.ProgressBar;
import android.widget.TextView;
import android.widget.Toast;

import androidx.annotation.OptIn;
import androidx.media3.common.MediaItem;
import androidx.media3.common.PlaybackException;
import androidx.media3.common.Player;
import androidx.media3.common.util.UnstableApi;
import androidx.media3.exoplayer.ExoPlayer;
import androidx.media3.ui.PlayerView;

import com.bumptech.glide.Glide;
import com.bumptech.glide.load.DataSource;
import com.bumptech.glide.load.engine.GlideException;
import com.bumptech.glide.request.RequestListener;
import com.bumptech.glide.request.target.Target;

import java.util.HashMap;
import java.util.List;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;
import java.util.concurrent.ThreadLocalRandom;

/**
 * Fullscreen player over a blurred backdrop. Up/Down: post. Left/Right: slide,
 * or seek on a single video. OK: pause. Double OK: like.
 */
public final class ViewerActivity extends Activity {
	private static final long SEEK_MS = 10_000, TICK_MS = 100;
	/** Frame grabs block on the network; keep them off the API pool. */
	private static final ExecutorService FRAMES = Executors.newSingleThreadExecutor();
	/** One thread, so like toggles reach the server in order. */
	private static final ExecutorService LIKES = Executors.newSingleThreadExecutor();
	private static final ViewGroup.LayoutParams FILL = new ViewGroup.LayoutParams(
			ViewGroup.LayoutParams.MATCH_PARENT, ViewGroup.LayoutParams.MATCH_PARENT);

	private final Handler handler = new Handler(Looper.getMainLooper());
	private final Runnable ticker = this::tick;
	private final DoubleOk doubleOk = new DoubleOk();
	private ExoPlayer player;
	private PlayerView video;
	private ImageView backdrop, photo, pauseIcon, heart, bigHeart;
	private ProgressBar progress;
	private TextView message;
	private int index, slide;
	/** Bumped on every slide change; late callbacks for older slides are dropped. */
	private volatile int generation;
	private boolean paused, failed, loadingMore, parkedAtEnd, shown, stopped;
	private long photoElapsed, lastTick;

	@Override
	@OptIn(markerClass = UnstableApi.class)
	protected void onCreate(Bundle state) {
		super.onCreate(state);
		getWindow().addFlags(WindowManager.LayoutParams.FLAG_KEEP_SCREEN_ON);
		FrameLayout root = new FrameLayout(this);
		root.setBackgroundColor(Color.BLACK);
		backdrop = new ImageView(this);
		backdrop.setScaleType(ImageView.ScaleType.CENTER_CROP);
		Ui.blur(backdrop, 40);
		root.addView(backdrop, FILL);
		View dim = new View(this);
		dim.setBackgroundColor(0x66000000);
		root.addView(dim, FILL);
		photo = new ImageView(this);
		photo.setScaleType(ImageView.ScaleType.FIT_CENTER);
		root.addView(photo, FILL);
		player = new ExoPlayer.Builder(this).build();
		player.addListener(new Player.Listener() {
			@Override
			public void onPlaybackStateChanged(int s) {
				if (s == Player.STATE_ENDED)
					advance();
			}

			@Override
			public void onPlayerError(PlaybackException e) {
				fail();
			}
		});
		video = new PlayerView(this);
		video.setUseController(false);
		video.setShutterBackgroundColor(Color.TRANSPARENT);
		video.setPlayer(player);
		root.addView(video, FILL);
		message = Ui.text(this, "", 20);
		message.setGravity(Gravity.CENTER);
		root.addView(message, FILL);
		progress = new ProgressBar(this, null, android.R.attr.progressBarStyleHorizontal);
		progress.setMax(1000);
		root.addView(progress, new FrameLayout.LayoutParams(ViewGroup.LayoutParams.MATCH_PARENT,
				Ui.dp(this, 4), Gravity.BOTTOM));
		pauseIcon = overlay(root, R.drawable.ic_pause, "Paused", 32, Gravity.BOTTOM | Gravity.CENTER_HORIZONTAL);
		heart = overlay(root, R.drawable.ic_favorite, "Liked", 32, Gravity.BOTTOM | Gravity.END);
		bigHeart = overlay(root, R.drawable.ic_favorite, "Liked", 160, Gravity.CENTER);
		heart.setColorFilter(Ui.RED);
		bigHeart.setColorFilter(Ui.RED);
		setContentView(root);

		if (!Playlist.posts.isEmpty()) {
			show(Playlist.start);
		} else if (Playlist.more != null) {
			message.setText("Loading…");
			maybeLoadMore();
		} else {
			finish(); // process restarted; the list is gone
		}
	}

	private ImageView overlay(FrameLayout root, int icon, String description, int sizeDp, int gravity) {
		ImageView v = new ImageView(this);
		v.setImageResource(icon);
		v.setContentDescription(description);
		v.setVisibility(View.GONE);
		int s = Ui.dp(this, sizeDp), m = Ui.dp(this, 24);
		FrameLayout.LayoutParams lp = new FrameLayout.LayoutParams(s, s, gravity);
		lp.setMargins(m, m, m, m);
		root.addView(v, lp);
		return v;
	}

	private Post post() {
		return Playlist.posts.get(index);
	}

	private Post.Media media() {
		return post().media.get(slide);
	}

	private void show(int i) {
		index = i;
		slide = 0;
		maybeLoadMore();
		showSlide();
	}

	private void showSlide() {
		Post.Media m = media();
		int gen = ++generation;
		paused = false;
		failed = false;
		shown = false;
		photoElapsed = 0;
		lastTick = SystemClock.uptimeMillis();
		parkedAtEnd = false;
		message.setText("");
		pauseIcon.setVisibility(View.GONE);
		heart.setVisibility(Likes.has(post().id) ? View.VISIBLE : View.GONE);
		Glide.with(backdrop).load(m.video ? m.thumbnailUrl : m.previewUrl).override(200).into(backdrop);
		if (m.video) {
			Glide.with(photo).clear(photo);
			video.setVisibility(View.VISIBLE);
			player.setMediaItem(MediaItem.fromUri(m.previewUrl));
			player.prepare();
			player.play();
			randomFrame(m, gen);
		} else {
			player.stop();
			video.setVisibility(View.GONE);
			Glide.with(photo).load(m.previewUrl).listener(new RequestListener<Drawable>() {
				@Override
				public boolean onLoadFailed(GlideException e, Object model, Target<Drawable> target, boolean first) {
					if (gen == generation)
						fail();
					return false;
				}

				@Override
				public boolean onResourceReady(Drawable d, Object model, Target<Drawable> target, DataSource source,
						boolean first) {
					if (gen == generation) { // count from when the photo is on screen
						shown = true;
						photoElapsed = 0;
						lastTick = SystemClock.uptimeMillis();
					}
					return false;
				}
			}).into(photo);
		}
		tick();
		if (stopped) { // page arrived in the background: stay paused, onStart re-prepares
			setPaused(true);
			player.stop();
		}
	}

	// ponytail: a grab already blocked in setDataSource is not interrupted, so a slow one delays the next post's frame; upgrade: a timeout or per-post cancellation.
	/** Swaps the video backdrop for a frame from 20-80 % of the clip; ends are often black. */
	private void randomFrame(Post.Media m, int gen) {
		if (m.durationMs <= 0)
			return;
		long us = (long) (m.durationMs * 1000 * (0.2 + 0.6 * ThreadLocalRandom.current().nextDouble()));
		Api.async(FRAMES, () -> {
			if (gen != generation)
				return null;
			try (MediaMetadataRetriever r = new MediaMetadataRetriever()) {
				r.setDataSource(m.previewUrl, new HashMap<>(Api.cookieHeaders(m.previewUrl)));
				return r.getScaledFrameAtTime(us, MediaMetadataRetriever.OPTION_CLOSEST_SYNC, 320, 180);
			}
		}, frame -> {
			if (frame != null && gen == generation) {
				Glide.with(backdrop).clear(backdrop);
				backdrop.setImageBitmap(frame);
			}
		}, e -> {
			// keep the blurred server thumbnail
		});
	}

	/** Drives the progress bar and the photo timer. */
	private void tick() {
		handler.removeCallbacks(ticker);
		long now = SystemClock.uptimeMillis(), dt = now - lastTick;
		lastTick = now;
		if (media().video && !failed) {
			long d = player.getDuration();
			progress.setProgress(d > 0 ? (int) (1000 * player.getCurrentPosition() / d) : 0);
		} else {
			if (!paused && (shown || failed))
				photoElapsed += dt;
			long total = Prefs.photoSeconds() * 1000L;
			progress.setProgress((int) (1000 * Math.min(photoElapsed, total) / total));
			if (photoElapsed >= total) {
				advance();
				return;
			}
		}
		handler.postDelayed(ticker, TICK_MS);
	}

	private void advance() {
		if (slide < post().media.size() - 1) {
			slide++;
			showSlide();
		} else if (index < Playlist.posts.size() - 1) {
			show(index + 1);
		} else {
			parkedAtEnd = true;
			setPaused(true); // end of the list
		}
	}

	private void fail() {
		failed = true;
		photoElapsed = 0;
		message.setText("Cannot load this post");
		if (media().video)
			player.stop();
	}

	private void setPaused(boolean p) {
		paused = p;
		if (!p)
			lastTick = SystemClock.uptimeMillis();
		pauseIcon.setVisibility(p ? View.VISIBLE : View.GONE);
		if (media().video && !failed) {
			if (p)
				player.pause();
			else
				player.play();
		}
	}

	private void step(int dir) {
		if (post().media.size() > 1) {
			int s = slide + dir;
			if (s >= 0 && s < post().media.size()) {
				slide = s;
				showSlide();
			}
		} else if (media().video && !failed) {
			player.seekTo(Math.max(0, player.getCurrentPosition() + dir * SEEK_MS));
		}
	}

	private void toggleLike() {
		Post p = post();
		boolean on = !Likes.has(p.id);
		Likes.set(p.id, on);
		heart.setVisibility(on ? View.VISIBLE : View.GONE);
		if (on) {
			bigHeart.setAlpha(1f);
			bigHeart.setVisibility(View.VISIBLE);
			bigHeart.animate().alpha(0f).setDuration(700).withEndAction(() -> bigHeart.setVisibility(View.GONE)).start();
		}
		Api.async(LIKES, () -> {
			Api.setLike(p.id, on);
			return true;
		}, ok -> {
		}, e -> {
			if (Likes.has(p.id) != on)
				return; // a newer toggle wins
			Likes.set(p.id, !on);
			if (!isDestroyed() && post() == p)
				heart.setVisibility(on ? View.GONE : View.VISIBLE);
			String msg = e.getMessage();
			Toast.makeText(this, "Like failed" + (msg != null ? ": " + msg : ""), Toast.LENGTH_SHORT).show();
		});
	}

	/** Fetches the next page when three posts remain. */
	private void maybeLoadMore() {
		if (Playlist.more == null || loadingMore || index < Playlist.posts.size() - 3)
			return;
		loadingMore = true;
		List<Post> list = Playlist.posts;
		Api.async(Playlist.more, page -> {
			if (isDestroyed() || Playlist.posts != list)
				return;
			loadingMore = false;
			boolean first = list.isEmpty();
			int old = list.size();
			if (page.isEmpty())
				Playlist.more = null;
			Playlist.append(page);
			if (first && !list.isEmpty())
				show(0);
			else if (parkedAtEnd && index == old - 1 && list.size() > old)
				show(index + 1);
			else if (list.isEmpty() && Playlist.more == null)
				message.setText("Nothing to show");
		}, e -> {
			if (isDestroyed())
				return;
			loadingMore = false;
			if (Playlist.posts.isEmpty())
				message.setText("Cannot load posts. Press Down to retry.");
			else
				Toast.makeText(this, "Cannot load more: " + e.getMessage(), Toast.LENGTH_SHORT).show();
		});
	}

	@Override
	public boolean onKeyDown(int code, KeyEvent e) {
		if (Playlist.posts.isEmpty()) {
			if (code == KeyEvent.KEYCODE_DPAD_DOWN)
				maybeLoadMore();
			return super.onKeyDown(code, e);
		}
		switch (code) {
		case KeyEvent.KEYCODE_DPAD_UP:
			if (index > 0)
				show(index - 1);
			return true;
		case KeyEvent.KEYCODE_DPAD_DOWN:
			if (index < Playlist.posts.size() - 1)
				show(index + 1);
			else
				maybeLoadMore(); // retry a failed page
			return true;
		case KeyEvent.KEYCODE_DPAD_LEFT:
			step(-1);
			return true;
		case KeyEvent.KEYCODE_DPAD_RIGHT:
			step(1);
			return true;
		case KeyEvent.KEYCODE_DPAD_CENTER:
		case KeyEvent.KEYCODE_ENTER:
			if (e.getRepeatCount() > 0)
				return true;
			// Pause at once; a second press undoes it and likes instead.
			setPaused(!paused);
			if (doubleOk.press(e.getEventTime()))
				toggleLike();
			return true;
		default:
			return super.onKeyDown(code, e);
		}
	}

	@Override
	protected void onStart() {
		super.onStart();
		stopped = false;
		// The first show() already prepared (state is not IDLE), so this only revives a stopped decoder.
		if (!Playlist.posts.isEmpty() && media().video && !failed && player.getPlaybackState() == Player.STATE_IDLE) {
			player.setPlayWhenReady(!paused);
			player.prepare();
		}
	}

	@Override
	protected void onStop() {
		super.onStop();
		stopped = true;
		player.stop(); // free the video decoder while in the background
	}

	@Override
	protected void onPause() {
		super.onPause();
		if (!Playlist.posts.isEmpty() && !paused)
			setPaused(true);
	}

	@Override
	protected void onDestroy() {
		super.onDestroy();
		handler.removeCallbacksAndMessages(null);
		generation++;
		Glide.with(photo).clear(photo);
		Glide.with(backdrop).clear(backdrop);
		player.release();
	}
}