/* Communication module for Android terminals.  -*- c-file-style: "GNU" -*-

Copyright (C) 2023-2024 Free Software Foundation, Inc.

This file is part of GNU Emacs.

GNU Emacs is free software: you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation, either version 3 of the License, or (at
your option) any later version.

GNU Emacs 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.

You should have received a copy of the GNU General Public License
along with GNU Emacs.  If not, see <https://www.gnu.org/licenses/>.  */

package org.gnu.emacs;

import java.lang.IllegalStateException;
import java.util.List;
import java.util.ArrayList;

import android.app.Activity;

import android.content.ContentResolver;
import android.content.Context;
import android.content.Intent;

import android.os.Build;
import android.os.Bundle;

import android.util.Log;

import android.net.Uri;

import android.view.Menu;
import android.view.View;
import android.view.ViewTreeObserver;
import android.view.Window;
import android.view.WindowInsets;
import android.view.WindowInsetsController;

import android.widget.FrameLayout;

public class EmacsActivity extends Activity
  implements EmacsWindowAttachmentManager.WindowConsumer,
  ViewTreeObserver.OnGlobalLayoutListener
{
  public static final String TAG = "EmacsActivity";

  /* ID for URIs from a granted document tree.  */
  public static final int ACCEPT_DOCUMENT_TREE = 1;

  /* The currently attached EmacsWindow, or null if none.  */
  private EmacsWindow window;

  /* The frame layout associated with the activity.  */
  private FrameLayout layout;

  /* List of activities with focus.  */
  public static final List<EmacsActivity> focusedActivities;

  /* The last activity to have been focused.  */
  public static EmacsActivity lastFocusedActivity;

  /* The currently focused window.  */
  public static EmacsWindow focusedWindow;

  /* Whether or not this activity is paused.  */
  private boolean isPaused;

  /* Whether or not this activity is fullscreen.  */
  private boolean isFullscreen;

  /* The last context menu to be closed.  */
  private static Menu lastClosedMenu;

  static
  {
    focusedActivities = new ArrayList<EmacsActivity> ();
  };

  public static void
  invalidateFocus1 (EmacsWindow window)
  {
    if (window.view.isFocused ())
      focusedWindow = window;

    synchronized (window.children)
      {
	for (EmacsWindow child : window.children)
	  invalidateFocus1 (child);
      }
  }

  public static void
  invalidateFocus (int whence)
  {
    EmacsWindow oldFocus;

    /* Walk through each focused activity and assign the window focus
       to the bottom-most focused window within.  Record the old focus
       as well.  */
    oldFocus = focusedWindow;
    focusedWindow = null;

    for (EmacsActivity activity : focusedActivities)
      {
	if (activity.window != null)
	  invalidateFocus1 (activity.window);
      }

    /* Send focus in- and out- events to the previous and current
       focus.  */

    if (oldFocus != null)
      EmacsNative.sendFocusOut (oldFocus.handle,
				System.currentTimeMillis ());

    if (focusedWindow != null)
      EmacsNative.sendFocusIn (focusedWindow.handle,
			       System.currentTimeMillis ());
  }

  @Override
  public final void
  detachWindow ()
  {
    syncFullscreenWith (null);

    if (window == null)
      Log.w (TAG, "detachWindow called, but there is no window");
    else
      {
	/* Clear the window's pointer to this activity and remove the
	   window's view.  */
	window.setConsumer (null);

	/* The window can't be iconified any longer.  */
	window.noticeDeiconified ();
	layout.removeView (window.view);
	window = null;

	invalidateFocus (0);
      }
  }

  @Override
  public final void
  attachWindow (EmacsWindow child)
  {
    if (window != null)
      throw new IllegalStateException ("trying to attach window when one"
				       + " already exists");

    syncFullscreenWith (child);

    /* Record and attach the view.  */

    window = child;
    layout.addView (window.view);
    child.setConsumer (this);

    /* If the window isn't no-focus-on-map, focus its view.  */
    if (!child.getDontFocusOnMap ())
      window.view.requestFocus ();

    /* If the activity is iconified, send that to the window.  */
    if (isPaused)
      window.noticeIconified ();

    /* Invalidate the focus.  Since attachWindow may be called from
       either the main or the UI thread, post this to the UI thread.  */

    runOnUiThread (new Runnable () {
	@Override
	public void
	run ()
	{
	  invalidateFocus (1);
	}
      });
  }

  @Override
  public final void
  destroy ()
  {
    finish ();
  }

  @Override
  public final EmacsWindow
  getAttachedWindow ()
  {
    return window;
  }

  @Override
  public final void
  onCreate (Bundle savedInstanceState)
  {
    FrameLayout.LayoutParams params;
    Intent intent;
    View decorView;
    ViewTreeObserver observer;
    int matchParent;

    /* See if Emacs should be started with any extra arguments, such
       as `--quick'.  */
    intent = getIntent ();
    EmacsService.extraStartupArgument
      = intent.getStringExtra ("org.gnu.emacs.STARTUP_ARGUMENT");

    matchParent = FrameLayout.LayoutParams.MATCH_PARENT;
    params
      = new FrameLayout.LayoutParams (matchParent,
				      matchParent);

    /* Make the frame layout.  */
    layout = new FrameLayout (this);
    layout.setLayoutParams (params);

    /* Set it as the content view.  */
    setContentView (layout);

    /* Maybe start the Emacs service if necessary.  */
    EmacsService.startEmacsService (this);

    /* Add this activity to the list of available activities.  */
    EmacsWindowAttachmentManager.MANAGER.registerWindowConsumer (this);

    /* Start observing global layout changes between Jelly Bean and Q.
       This is required to restore the fullscreen state whenever the
       on screen keyboard is displayed, as there is otherwise no way
       to determine when the on screen keyboard becomes visible.  */

    if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.JELLY_BEAN
	&& Build.VERSION.SDK_INT < Build.VERSION_CODES.R)
      {
	decorView = getWindow ().getDecorView ();
	observer = decorView.getViewTreeObserver ();
	observer.addOnGlobalLayoutListener (this);
      }

    super.onCreate (savedInstanceState);
  }

  @Override
  public final void
  onGlobalLayout ()
  {
    syncFullscreenWith (window);
  }

  @Override
  public final void
  onDestroy ()
  {
    EmacsWindowAttachmentManager manager;
    boolean isMultitask;

    manager = EmacsWindowAttachmentManager.MANAGER;

    /* The activity will die shortly hereafter.  If there is a window
       attached, close it now.  */
    isMultitask = this instanceof EmacsMultitaskActivity;
    manager.removeWindowConsumer (this, isMultitask || isFinishing ());
    focusedActivities.remove (this);
    invalidateFocus (2);

    /* Remove this activity from the static field, lest it leak.  */
    if (lastFocusedActivity == this)
      lastFocusedActivity = null;

    super.onDestroy ();
  }

  @Override
  public final void
  onWindowFocusChanged (boolean isFocused)
  {
    /* At times and on certain versions of Android ISFOCUSED does not
       reflect whether the window actually holds focus, so replace it
       with the value of `hasWindowFocus'.  */
    isFocused = hasWindowFocus ();

    if (isFocused)
      {
	if (!focusedActivities.contains (this))
	  focusedActivities.add (this);

	lastFocusedActivity = this;

	/* Update the window insets as the focus change may have
	   changed the window insets as well, and the system does not
	   automatically restore visibility flags.  */

	if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.JELLY_BEAN
	    && Build.VERSION.SDK_INT < Build.VERSION_CODES.R
	    && isFullscreen)
	  syncFullscreenWith (window);
      }
    else
      focusedActivities.remove (this);

    invalidateFocus (3);
  }

  @Override
  public final void
  onPause ()
  {
    isPaused = true;

    EmacsWindowAttachmentManager.MANAGER.noticeIconified (this);
    super.onPause ();
  }

  @Override
  public final void
  onResume ()
  {
    isPaused = false;

    EmacsWindowAttachmentManager.MANAGER.noticeDeiconified (this);
    super.onResume ();
  }

  @Override
  public final void
  onContextMenuClosed (Menu menu)
  {
    int serial;

    /* See the comment inside onMenuItemClick.  */

    if (((EmacsContextMenu.wasSubmenuSelected == -2)
	 || (EmacsContextMenu.wasSubmenuSelected >= 0
	     && ((System.currentTimeMillis ()
		  - EmacsContextMenu.wasSubmenuSelected)
		 <= 300)))
	|| menu == lastClosedMenu)
      {
	EmacsContextMenu.wasSubmenuSelected = -1;
	lastClosedMenu = menu;
	return;
      }

    /* lastClosedMenu is set because Android apparently calls this
       function twice.  */

    lastClosedMenu = null;

    /* Send a context menu event given that no menu item has already
       been selected.  */
    if (!EmacsContextMenu.itemAlreadySelected)
      {
	serial = EmacsContextMenu.lastMenuEventSerial;
	EmacsNative.sendContextMenu ((short) 0, 0,
				     serial);
      }

    super.onContextMenuClosed (menu);
  }

  @SuppressWarnings ("deprecation")
  public final void
  syncFullscreenWith (EmacsWindow emacsWindow)
  {
    WindowInsetsController controller;
    Window window;
    int behavior, flags;
    View view;

    if (emacsWindow != null)
      isFullscreen = emacsWindow.fullscreen;
    else
      isFullscreen = false;

    /* On Android 11 or later, use the window insets controller to
       control whether or not the view is fullscreen.  */

    if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.R)
      {
	window = getWindow ();

	/* If there is no attached window, return immediately.  */
	if (window == null)
	  return;

	behavior = WindowInsetsController.BEHAVIOR_SHOW_TRANSIENT_BARS_BY_SWIPE;
	controller = window.getInsetsController ();
	controller.setSystemBarsBehavior (behavior);

	if (isFullscreen)
	  controller.hide (WindowInsets.Type.statusBars ()
			   | WindowInsets.Type.navigationBars ());
	else
	  controller.show (WindowInsets.Type.statusBars ()
			   | WindowInsets.Type.navigationBars ());

	return;
      }

    if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.JELLY_BEAN)
      {
	/* On Android 4.1 or later, use `setSystemUiVisibility'.  */

	window = getWindow ();

	if (window == null)
	  return;

	view = window.getDecorView ();

	if (isFullscreen)
	  {
	    flags = 0;
	    flags |= View.SYSTEM_UI_FLAG_FULLSCREEN;

	    if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.KITKAT)
	      {
		/* These flags means that Emacs will be full screen as
		   long as the state flag is set.  */
		flags |= View.SYSTEM_UI_FLAG_HIDE_NAVIGATION;
		flags |= View.SYSTEM_UI_FLAG_IMMERSIVE;
		flags |= View.SYSTEM_UI_FLAG_IMMERSIVE_STICKY;
	      }

	    /* Apply the given flags.  */
	    view.setSystemUiVisibility (flags);
	  }
	else
	  view.setSystemUiVisibility (View.SYSTEM_UI_FLAG_VISIBLE);
      }
  }

  @Override
  public final void
  onAttachedToWindow ()
  {
    super.onAttachedToWindow ();

    /* Update the window insets.  */
    syncFullscreenWith (window);
  }



  @Override
  public final void
  onActivityResult (int requestCode, int resultCode, Intent data)
  {
    ContentResolver resolver;
    Uri uri;
    int flags;

    switch (requestCode)
      {
      case ACCEPT_DOCUMENT_TREE:

	/* A document granted through
	   EmacsService.requestDirectoryAccess.  */

	if (resultCode == RESULT_OK)
	  {
	    resolver = getContentResolver ();
	    uri = data.getData ();
	    flags = (Intent.FLAG_GRANT_READ_URI_PERMISSION
		     | Intent.FLAG_GRANT_WRITE_URI_PERMISSION);

	    try
	      {
		if (uri != null)
		  resolver.takePersistableUriPermission (uri, flags);
	      }
	    catch (Exception exception)
	      {
		/* Permission to access URI might've been revoked in
		   between selecting the file and this callback being
		   invoked.  Don't crash in such cases.  */
	      }
	  }

	break;
      }
  }
};