//
// wdmtg.vala: activity tracker
//
// Copyright (c) 2016 - 2020, Přemysl Eric Janouch <p@janouch.name>
//
// Permission to use, copy, modify, and/or distribute this software for any
// purpose with or without fee is hereby granted.
//
// THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
// WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
// MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY
// SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
// WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN ACTION
// OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF OR IN
// CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
//
// vim: set sw=2 ts=2 sts=2 et tw=80:
// modules: x11 xext  config
// vapidirs: . ../build build

namespace Wdmtg {

// --- Utilities ---------------------------------------------------------------

  void exit_fatal (string format, ...) {
    stderr.vprintf ("fatal: " + format + "\n", va_list ());
    Process.exit (1);
  }

  string[] get_xdg_config_dirs () {
    string[] paths = { Environment.get_user_config_dir () };
    foreach (var system_path in Environment.get_system_config_dirs ())
      paths += system_path;
    return paths;
  }

// --- Globals -----------------------------------------------------------------

  X.Display dpy;                        ///< X display handle
  int sync_base;                        ///< Sync extension base

  X.ID idle_counter;                    ///< XSync IDLETIME counter
  X.Sync.Value idle_timeout;            ///< User idle timeout

  X.ID idle_alarm_inactive;             ///< User is inactive
  X.ID idle_alarm_active;               ///< User is active

  X.Atom net_active_window;             ///< _NET_ACTIVE_WINDOW atom
  X.Atom net_wm_name;                   ///< _NET_WM_NAME atom

  string? current_title;                ///< Current window title
  X.Window current_window;              ///< Current window
  bool current_idle = false;            ///< Current idle status

  struct Event {
    public int64 timestamp;             ///< When the event happened
    public string? title;               ///< Current title at the time
    public bool idle;                   ///< Whether the user is idle
  }

  AsyncQueue<Event?> queue;             ///< Async queue

// --- X helpers ---------------------------------------------------------------

  X.ID get_counter (string name) {
    int n_counters = 0;
    var counters = X.Sync.list_system_counters (dpy, out n_counters);
    X.ID counter = X.None;
    while (n_counters-- > 0) {
      if (counters[n_counters].name == name)
        counter = counters[n_counters].counter;
    }
    X.Sync.free_system_counter_list (counters);
    return counter;
  }

  string? x_text_property_to_utf8 (ref X.TextProperty prop) {
    X.Atom utf8_string = dpy.intern_atom ("UTF8_STRING", true);
    if (prop.encoding == utf8_string)
      return (string) prop.value;

    int n = 0;
    uint8 **list = null;
    if (X.mb_text_property_to_text_list (dpy, ref prop, out list, out n)
      >= X.Success && n > 0 && null != list[0]) {
      var result = ((string) list[0]).locale_to_utf8 (-1, null, null);
      X.free_string_list (list);
      return result;
    }
    return null;
  }

  string? x_text_property (X.Window window, X.Atom atom) {
    X.TextProperty name;
    X.get_text_property (dpy, window, out name, atom);
    if (null == name.@value)
      return null;

    string? result = x_text_property_to_utf8 (ref name);
    X.free (name.@value);
    return result;
  }

// --- X error handling --------------------------------------------------------

  X.ErrorHandler default_x_error_handler;

  int on_x_error (X.Display dpy, X.ErrorEvent *ee) {
    // This just is going to happen since those windows aren't ours
    if (ee.error_code == X.ErrorCode.BAD_WINDOW)
      return 0;
    return default_x_error_handler (dpy, ee);
  }

// --- Application -------------------------------------------------------------

  string x_window_title (X.Window window) {
    string? title;
    if (null == (title = x_text_property (window, net_wm_name))
     && null == (title = x_text_property (window, X.XA_WM_NAME)))
      title = "broken";
    return title;
  }

  bool update_window_title (string? new_title) {
    bool changed = (null == current_title) != (null == new_title)
      || current_title != new_title;
    current_title = new_title;
    return changed;
  }

  void push_event () {
    queue.push(Event () {
      timestamp = get_real_time (),
      title = current_title,
      idle = current_idle
    });
  }

  void update_current_window () {
    var root = dpy.default_root_window ();
    X.Atom dummy_type; int dummy_format; ulong nitems, dummy_bytes;
    void *p = null;
    if (dpy.get_window_property (root, net_active_window,
      0, 1, false, X.XA_WINDOW, out dummy_type, out dummy_format,
      out nitems, out dummy_bytes, out p) != X.Success)
      return;

    string? new_title = null;
    if (0 != nitems) {
      X.Window active_window = *(X.Window *) p;
      X.free (p);

      if (current_window != active_window && X.None != current_window)
        dpy.select_input (current_window, 0);
      dpy.select_input (active_window, X.EventMask.PropertyChangeMask);
      new_title = x_window_title (active_window);
      current_window = active_window;
    }
    if (update_window_title (new_title)) {
      stdout.printf ("Window changed: %s\n",
        null != current_title ? current_title : "(none)");
      push_event ();
    }
  }

  void on_x_property_notify (X.PropertyEvent *xproperty) {
    // This is from the EWMH specification, set by the window manager
    if (xproperty.atom == net_active_window)
      update_current_window ();
    else if (xproperty.window == current_window
      && xproperty.atom == net_wm_name) {
      if (update_window_title (x_window_title (current_window))) {
        stdout.printf ("Title changed: %s\n", current_title);
        push_event ();
      }
    }
  }

  void set_idle_alarm
    (ref X.ID alarm, X.Sync.TestType test, X.Sync.Value @value) {
    X.Sync.AlarmAttributes attr = {};
    attr.trigger.counter = idle_counter;
    attr.trigger.test_type = test;
    attr.trigger.wait_value = @value;
    X.Sync.int_to_value (out attr.delta, 0);

    X.Sync.CA flags = X.Sync.CA.Counter | X.Sync.CA.TestType
      | X.Sync.CA.Value | X.Sync.CA.Delta;
    if (X.None != alarm)
      X.Sync.change_alarm (dpy, alarm, flags, ref attr);
    else
      alarm = X.Sync.create_alarm (dpy, flags, ref attr);
  }

  void on_x_alarm_notify (X.Sync.AlarmNotifyEvent *xalarm) {
    if (xalarm.alarm == idle_alarm_inactive) {
      stdout.printf ("User is inactive\n");
      current_idle = true;
      push_event ();

      X.Sync.Value one, minus_one;
      X.Sync.int_to_value (out one, 1);

      int overflow;
      X.Sync.value_subtract
        (out minus_one, xalarm.counter_value, one, out overflow);

      // Set an alarm for IDLETIME <= current_idletime - 1
      set_idle_alarm (ref idle_alarm_active,
        X.Sync.TestType.NegativeComparison, minus_one);
    } else if (xalarm.alarm == idle_alarm_inactive) {
      stdout.printf ("User is active\n");
      current_idle = false;
      push_event ();

      set_idle_alarm (ref idle_alarm_inactive,
        X.Sync.TestType.PositiveComparison, idle_timeout);
    }
  }

  void generate_events () {
    var channel = new IOChannel.unix_new (dpy.connection_number ());
    var watch = channel.create_watch (IOCondition.IN);
    watch.set_callback (() => {
      X.Event ev = {0};
      while (0 != dpy.pending ()) {
        if (0 != dpy.next_event (ref ev)) {
          exit_fatal ("XNextEvent returned non-zero");
        } else if (ev.type == X.EventType.PropertyNotify) {
          on_x_property_notify (&ev.xproperty);
        } else if (ev.type == sync_base + X.Sync.EventType.AlarmNotify) {
          on_x_alarm_notify ((X.Sync.AlarmNotifyEvent *) (&ev));
        }
      }
      return true;
    });

    var loop = new MainLoop (MainContext.get_thread_default ());
    watch.attach (loop.get_context ());
    loop.run ();
  }

  bool show_version;
  const OptionEntry[] options = {
    { "version", 'V', OptionFlags.IN_MAIN, OptionArg.NONE, ref show_version,
      "output version information and exit" },
    { null }
  };

  public int main (string[] args) {
    if (null == Intl.setlocale (GLib.LocaleCategory.CTYPE))
      exit_fatal ("cannot set locale");
    if (0 == X.supports_locale ())
      exit_fatal ("locale not supported by Xlib");

    try {
      Gtk.init_with_args (ref args, " - activity tracker", options, null);
    } catch (OptionError e) {
      exit_fatal ("option parsing failed: %s", e.message);
    } catch (Error e) {
      exit_fatal ("%s", e.message);
    }
    if (show_version) {
      stdout.printf (Config.PROJECT_NAME + " " + Config.PROJECT_VERSION + "\n");
      return 0;
    }

    queue = new AsyncQueue<Event?> ();

    X.init_threads ();
    if (null == (dpy = new X.Display ()))
      exit_fatal ("cannot open display");

    net_active_window = dpy.intern_atom ("_NET_ACTIVE_WINDOW", true);
    net_wm_name       = dpy.intern_atom ("_NET_WM_NAME", true);

    // TODO: it is possible to employ a fallback mechanism via XScreenSaver
    //   by polling the XScreenSaverInfo::idle field, see
    //   https://www.x.org/releases/X11R7.5/doc/man/man3/Xss.3.html

    int dummy;
    if (0 == X.Sync.query_extension (dpy, out sync_base, out dummy)
     || 0 == X.Sync.initialize (dpy, out dummy, out dummy))
      exit_fatal ("cannot initialize XSync");

    // The idle counter is not guaranteed to exist, only SERVERTIME is
    if (X.None == (idle_counter = get_counter ("IDLETIME")))
      exit_fatal ("idle counter is missing");

    var root = dpy.default_root_window ();
    dpy.select_input (root, X.EventMask.PropertyChangeMask);
    X.sync (dpy, false);
    default_x_error_handler = X.set_error_handler (on_x_error);

    int timeout = 600;  // 10 minutes by default
    try {
      var kf = new KeyFile ();
      kf.load_from_dirs (Config.PROJECT_NAME + Path.DIR_SEPARATOR_S
        + Config.PROJECT_NAME + ".conf", get_xdg_config_dirs (), null, 0);

      var n = kf.get_uint64 ("Settings", "idle_timeout");
      if (0 != n && n <= int.MAX / 1000)
        timeout = (int) n;
    } catch (Error e) {
      // Ignore errors this far, keeping the defaults
    }

    X.Sync.int_to_value (out idle_timeout, timeout * 1000);
    update_current_window ();
    set_idle_alarm (ref idle_alarm_inactive,
      X.Sync.TestType.PositiveComparison, idle_timeout);

    var data_path = Path.build_filename (Environment.get_user_data_dir (),
      Config.PROJECT_NAME);
    DirUtils.create_with_parents (data_path, 0755);

    // TODO: try exclusivity/invocation either via DBus directly,
    // or via GApplication or GtkApplication:
    //  - GtkApplication calls Gtk.init automatically during "startup" signal,
    //    Gtk.init doesn't get command line args
    //  - "inhibiting" makes no sense, it can't be used for mere delays
    //     - actually, the "query-end" signal
    //     - should check whether it tries to exit cleanly
    //  - what is the session manager, do I have it?
    //     - "register-session" looks useful
    //     - GTK+ keeps the application running as long as it has windows,
    //       though I want to keep it running forever
    //        - g_application_hold(), perhaps
    //  - so maybe just use GApplication, that will provide more control

    // Bind to a control socket, also ensuring only one instance is running
    var socket_path = Path.build_filename (data_path, "socket");

    Posix.Flock fl = Posix.Flock () {
      l_type = Posix.F_WRLCK,
      l_start = 0,
      l_whence = Posix.SEEK_SET,
      l_len = 0
    };

    var lk = FileStream.open (socket_path + ".lock", "w");
    if (Posix.fcntl (lk.fileno (), Posix.F_SETLK, &fl) < 0)
      exit_fatal("failed to acquire lock: %s", Posix.errno.to_string ());
    FileUtils.unlink (socket_path);

    Socket socket;
    try {
      socket = new Socket (SocketFamily.UNIX, SocketType.STREAM,
          SocketProtocol.DEFAULT);
      socket.bind (new UnixSocketAddress (socket_path), true /* allow_reuse */);
      socket.listen ();
    } catch (Error e) {
      exit_fatal ("%s: %s", socket_path, e.message);
    }

    Sqlite.Database db;
    var db_path = Path.build_filename (data_path, "db.sqlite");
    int rc = Sqlite.Database.open (db_path, out db);
    if (rc != Sqlite.OK)
      exit_fatal ("%s: %s", db_path, db.errmsg ());

    // This shouldn't normally happen but external applications may decide
    // to read things out, and mess with us.  When that takes too long, we may
    // a/ wait for it to finish, b/ start with a whole-database lock or, even
    // more simply, c/ crash on the BUSY error.
    db.busy_timeout (1000);

    string errmsg;
    if ((rc = db.exec ("BEGIN", null, out errmsg)) != Sqlite.OK)
      exit_fatal ("%s: %s", db_path, errmsg);

    Sqlite.Statement stmt;
    if ((rc = db.prepare_v2 ("PRAGMA user_version", -1, out stmt, null))
      != Sqlite.OK)
      exit_fatal ("%s: %s", db_path, db.errmsg ());
    if ((rc = stmt.step ()) != Sqlite.ROW || stmt.data_count () != 1)
      exit_fatal ("%s: %s", db_path, "cannot retrieve user version");

    var user_version = stmt.column_int (0);
    if (user_version == 0) {
      if ((rc = db.exec ("""CREATE TABLE events (
        id INTEGER PRIMARY KEY AUTOINCREMENT,
        timestamp INTEGER,
        title TEXT,
        idle BOOLEAN
      )""", null, out errmsg)) != Sqlite.OK)
        exit_fatal ("%s: %s", db_path, errmsg);

      if ((rc = db.exec ("PRAGMA user_version = 1", null, out errmsg))
        != Sqlite.OK)
        exit_fatal ("%s: %s", db_path, errmsg);
    } else if (user_version != 1) {
      exit_fatal ("%s: unsupported DB version: %d", db_path, user_version);
    }
    if ((rc = db.exec ("COMMIT", null, out errmsg)) != Sqlite.OK)
      exit_fatal ("%s: %s", db_path, errmsg);

    var generator = new Thread<void> ("generator", generate_events);
    // TODO: somehow read events from the async queue
    // TODO: listen for connections on the control socket
    Gtk.main ();
    generator.join ();
    return 0;
  }
}