/*
 * Copyright © 2001 Red Hat, Inc.
 *
 * Permission to use, copy, modify, distribute, and sell this software and its
 * documentation for any purpose is hereby granted without fee, provided that
 * the above copyright notice appear in all copies and that both that
 * copyright notice and this permission notice appear in supporting
 * documentation, and that the name of Red Hat not be used in advertising or
 * publicity pertaining to distribution of the software without specific,
 * written prior permission.  Red Hat makes no representations about the
 * suitability of this software for any purpose.  It is provided "as is"
 * without express or implied warranty.
 *
 * RED HAT DISCLAIMS ALL WARRANTIES WITH REGARD TO THIS SOFTWARE, INCLUDING ALL
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS, IN NO EVENT SHALL RED HAT
 * BE LIABLE FOR ANY SPECIAL, 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.
 *
 * Author:  Owen Taylor, Red Hat, Inc.
 */
#include <limits.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>

#include <X11/Xlib.h>
#include <X11/Xmd.h>		/* For CARD16 */

#include "xsettings-client.h"

struct _XSettingsClient
{
  Display *display;
  int screen;
  XSettingsNotifyFunc notify;
  XSettingsWatchFunc watch;
  void *cb_data;

  Window manager_window;
  Atom manager_atom;
  Atom selection_atom;
  Atom xsettings_atom;

  XSettingsList *settings;
};

static void
notify_changes (XSettingsClient *client,
		XSettingsList   *old_list)
{
  XSettingsList *old_iter = old_list;
  XSettingsList *new_iter = client->settings;

  if (!client->notify)
    return;

  while (old_iter || new_iter)
    {
      int cmp;
      
      if (old_iter && new_iter)
	cmp = strcmp (old_iter->setting->name, new_iter->setting->name);
      else if (old_iter)
	cmp = -1;
      else
	cmp = 1;

      if (cmp < 0)
	{
	  client->notify (old_iter->setting->name,
			  XSETTINGS_ACTION_DELETED,
			  NULL,
			  client->cb_data);
	}
      else if (cmp == 0)
	{
	  if (!xsettings_setting_equal (old_iter->setting,
					new_iter->setting))
	    client->notify (old_iter->setting->name,
			    XSETTINGS_ACTION_CHANGED,
			    new_iter->setting,
			    client->cb_data);
	}
      else
	{
	  client->notify (new_iter->setting->name,
			  XSETTINGS_ACTION_NEW,
			  new_iter->setting,
			  client->cb_data);
	}

      if (old_iter)
	old_iter = old_iter->next;
      if (new_iter)
	new_iter = new_iter->next;
    }
}

static int
ignore_errors (Display *display, XErrorEvent *event)
{
  return True;
}

static char local_byte_order = '\0';

#define BYTES_LEFT(buffer) ((buffer)->data + (buffer)->len - (buffer)->pos)

static XSettingsResult
fetch_card16 (XSettingsBuffer *buffer,
	      CARD16          *result)
{
  CARD16 x;

  if (BYTES_LEFT (buffer) < 2)
    return XSETTINGS_ACCESS;

  x = *(CARD16 *)buffer->pos;
  buffer->pos += 2;
  
  if (buffer->byte_order == local_byte_order)
    *result = x;
  else
    *result = (x << 8) | (x >> 8);

  return XSETTINGS_SUCCESS;
}

static XSettingsResult
fetch_ushort (XSettingsBuffer *buffer,
	      unsigned short  *result) 
{
  CARD16 x;
  XSettingsResult r;  

  r = fetch_card16 (buffer, &x);
  if (r == XSETTINGS_SUCCESS)
    *result = x;

  return r;
}

static XSettingsResult
fetch_card32 (XSettingsBuffer *buffer,
	      CARD32          *result)
{
  CARD32 x;

  if (BYTES_LEFT (buffer) < 4)
    return XSETTINGS_ACCESS;

  x = *(CARD32 *)buffer->pos;
  buffer->pos += 4;
  
  if (buffer->byte_order == local_byte_order)
    *result = x;
  else
    *result = (x << 24) | ((x & 0xff00) << 8) | ((x & 0xff0000) >> 8) | (x >> 24);
  
  return XSETTINGS_SUCCESS;
}

static XSettingsResult
fetch_card8 (XSettingsBuffer *buffer,
	     CARD8           *result)
{
  if (BYTES_LEFT (buffer) < 1)
    return XSETTINGS_ACCESS;

  *result = *(CARD8 *)buffer->pos;
  buffer->pos += 1;

  return XSETTINGS_SUCCESS;
}

#define XSETTINGS_PAD(n,m) ((n + m - 1) & (~(m-1)))

static XSettingsList *
parse_settings (unsigned char *data,
		size_t         len)
{
  XSettingsBuffer buffer;
  XSettingsResult result = XSETTINGS_SUCCESS;
  XSettingsList *settings = NULL;
  CARD32 serial;
  CARD32 n_entries;
  CARD32 i;
  XSettingsSetting *setting = NULL;
  
  local_byte_order = xsettings_byte_order ();

  buffer.pos = buffer.data = data;
  buffer.len = len;
  
  result = fetch_card8 (&buffer, &buffer.byte_order);
  if (buffer.byte_order != MSBFirst &&
      buffer.byte_order != LSBFirst)
    {
      fprintf (stderr, "Invalid byte order in XSETTINGS property\n");
      result = XSETTINGS_FAILED;
      goto out;
    }

  buffer.pos += 3;

  result = fetch_card32 (&buffer, &serial);
  if (result != XSETTINGS_SUCCESS)
    goto out;

  result = fetch_card32 (&buffer, &n_entries);
  if (result != XSETTINGS_SUCCESS)
    goto out;

  for (i = 0; i < n_entries; i++)
    {
      CARD8 type;
      CARD16 name_len;
      CARD32 v_int;
      size_t pad_len;
      
      result = fetch_card8 (&buffer, &type);
      if (result != XSETTINGS_SUCCESS)
	goto out;

      buffer.pos += 1;

      result = fetch_card16 (&buffer, &name_len);
      if (result != XSETTINGS_SUCCESS)
	goto out;

      pad_len = XSETTINGS_PAD(name_len, 4);
      if (BYTES_LEFT (&buffer) < pad_len)
	{
	  result = XSETTINGS_ACCESS;
	  goto out;
	}

      setting = malloc (sizeof *setting);
      if (!setting)
	{
	  result = XSETTINGS_NO_MEM;
	  goto out;
	}
      setting->type = XSETTINGS_TYPE_INT; /* No allocated memory */

      setting->name = malloc (name_len + 1);
      if (!setting->name)
	{
	  result = XSETTINGS_NO_MEM;
	  goto out;
	}

      memcpy (setting->name, buffer.pos, name_len);
      setting->name[name_len] = '\0';
      buffer.pos += pad_len;

      result = fetch_card32 (&buffer, &v_int);
      if (result != XSETTINGS_SUCCESS)
	goto out;
      setting->last_change_serial = v_int;

      switch (type)
	{
	case XSETTINGS_TYPE_INT:
	  result = fetch_card32 (&buffer, &v_int);
	  if (result != XSETTINGS_SUCCESS)
	    goto out;

	  setting->data.v_int = (INT32)v_int;
	  break;
	case XSETTINGS_TYPE_STRING:
	  result = fetch_card32 (&buffer, &v_int);
	  if (result != XSETTINGS_SUCCESS)
	    goto out;

	  pad_len = XSETTINGS_PAD (v_int, 4);
	  if (v_int + 1 == 0 || /* Guard against wrap-around */
	      BYTES_LEFT (&buffer) < pad_len)
	    {
	      result = XSETTINGS_ACCESS;
	      goto out;
	    }

	  setting->data.v_string = malloc (v_int + 1);
	  if (!setting->data.v_string)
	    {
	      result = XSETTINGS_NO_MEM;
	      goto out;
	    }
	  
	  memcpy (setting->data.v_string, buffer.pos, v_int);
	  setting->data.v_string[v_int] = '\0';
	  buffer.pos += pad_len;

	  break;
	case XSETTINGS_TYPE_COLOR:
	  result = fetch_ushort (&buffer, &setting->data.v_color.red);
	  if (result != XSETTINGS_SUCCESS)
	    goto out;
	  result = fetch_ushort (&buffer, &setting->data.v_color.green);
	  if (result != XSETTINGS_SUCCESS)
	    goto out;
	  result = fetch_ushort (&buffer, &setting->data.v_color.blue);
	  if (result != XSETTINGS_SUCCESS)
	    goto out;
	  result = fetch_ushort (&buffer, &setting->data.v_color.alpha);
	  if (result != XSETTINGS_SUCCESS)
	    goto out;

	  break;
	default:
	  /* Quietly ignore unknown types */
	  break;
	}

      setting->type = type;

      result = xsettings_list_insert (&settings, setting);
      if (result != XSETTINGS_SUCCESS)
	goto out;

      setting = NULL;
    }

 out:

  if (result != XSETTINGS_SUCCESS)
    {
      switch (result)
	{
	case XSETTINGS_NO_MEM:
	  fprintf(stderr, "Out of memory reading XSETTINGS property\n");
	  break;
	case XSETTINGS_ACCESS:
	  fprintf(stderr, "Invalid XSETTINGS property (read off end)\n");
	  break;
	case XSETTINGS_DUPLICATE_ENTRY:
	  fprintf (stderr, "Duplicate XSETTINGS entry for '%s'\n", setting->name);
	case XSETTINGS_FAILED:
	case XSETTINGS_SUCCESS:
	case XSETTINGS_NO_ENTRY:
	  break;
	}

      if (setting)
	xsettings_setting_free (setting);

      xsettings_list_free (settings);
      settings = NULL;

    }

  return settings;
}

static void
read_settings (XSettingsClient *client)
{
  Atom type;
  int format;
  unsigned long n_items;
  unsigned long bytes_after;
  unsigned char *data;
  int result;

  int (*old_handler) (Display *, XErrorEvent *);
  
  XSettingsList *old_list = client->settings;

  client->settings = NULL;
  
  old_handler = XSetErrorHandler (ignore_errors);
  result = XGetWindowProperty (client->display, client->manager_window,
			       client->xsettings_atom, 0, LONG_MAX,
			       False, client->xsettings_atom,
			       &type, &format, &n_items, &bytes_after, &data);
  XSetErrorHandler (old_handler);

  if (result == Success && type == client->xsettings_atom)
    {
      if (format != 8)
	{
	  fprintf (stderr, "Invalid format for XSETTINGS property %d", format);
	}
      else
	client->settings = parse_settings (data, n_items);

      XFree (data);
    }

  notify_changes (client, old_list);
  xsettings_list_free (old_list);
}

static void
add_events (Display *display,
	    Window   window,
	    long     mask)
{
  XWindowAttributes attr;

  XGetWindowAttributes (display, window, &attr);
  XSelectInput (display, window, attr.your_event_mask | mask);
}

static void
check_manager_window (XSettingsClient *client)
{
  if (client->manager_window && client->watch)
    client->watch (client->manager_window, False, 0, client->cb_data);
  
  XGrabServer (client->display);

  client->manager_window = XGetSelectionOwner (client->display,
					       client->selection_atom);
  if (client->manager_window)
    XSelectInput (client->display, client->manager_window,
		  PropertyChangeMask | StructureNotifyMask);

  XUngrabServer (client->display);
  XFlush (client->display);

  if (client->manager_window && client->watch)
    client->watch (client->manager_window, True, 
		   PropertyChangeMask | StructureNotifyMask,
		   client->cb_data);
  
  read_settings (client);
}

XSettingsClient *
xsettings_client_new (Display             *display,
		      int                  screen,
		      XSettingsNotifyFunc  notify,
		      XSettingsWatchFunc   watch,
		      void                *cb_data)
{
  XSettingsClient *client;
  char buffer[256];

  client = malloc (sizeof *client);
  if (!client)
    return NULL;

  client->display = display;
  client->screen = screen;
  client->notify = notify;
  client->watch = watch;
  client->cb_data = cb_data;
  
  client->manager_window = None;
  client->settings = NULL;

  sprintf(buffer, "_XSETTINGS_S%d", screen);
  client->selection_atom = XInternAtom (display, buffer, False);
  client->xsettings_atom = XInternAtom (display, "_XSETTINGS_SETTINGS", False);
  client->manager_atom = XInternAtom (display, "MANAGER", False);

  /* Select on StructureNotify so we get MANAGER events
   */
  add_events (display, RootWindow (display, screen), StructureNotifyMask);

  if (client->watch)
    client->watch (RootWindow (display, screen), True, StructureNotifyMask,
		   client->cb_data);

  check_manager_window (client);

  return client;
}

void
xsettings_client_destroy (XSettingsClient *client)
{
  if (client->watch)
    client->watch (RootWindow (client->display, client->screen),
		   False, 0, client->cb_data);
  if (client->manager_window && client->watch)
    client->watch (client->manager_window, False, 0, client->cb_data);
  
  xsettings_list_free (client->settings);
  free (client);
}

XSettingsResult
xsettings_client_get_setting (XSettingsClient   *client,
			      const char        *name,
			      XSettingsSetting **setting)
{
  XSettingsSetting *search = xsettings_list_lookup (client->settings, name);
  if (search)
    {
      *setting = xsettings_setting_copy (search);
      return *setting ? XSETTINGS_SUCCESS : XSETTINGS_NO_MEM;
    }
  else
    return XSETTINGS_NO_ENTRY;
}

Bool
xsettings_client_process_event (XSettingsClient *client,
				XEvent          *xev)
{
  /* The checks here will not unlikely cause us to reread
   * the properties from the manager window a number of
   * times when the manager changes from A->B. But manager changes
   * are going to be pretty rare.
   */
  if (xev->xany.window == RootWindow (client->display, client->screen))
    {
      if (xev->xany.type == ClientMessage &&
	  xev->xclient.message_type == client->manager_atom &&
	  xev->xclient.data.l[1] == client->selection_atom)
	{
	  check_manager_window (client);
	  return True;
	}
    }
  else if (xev->xany.window == client->manager_window)
    {
      if (xev->xany.type == DestroyNotify)
	{
	  check_manager_window (client);
	  return True;
	}
      else if (xev->xany.type == PropertyNotify)
	{
	  read_settings (client);
	  return True;
	}
    }
  
  return False;
}