/*
 * This file is a part of hildon
 *
 * Copyright (C) 2005, 2006 Nokia Corporation, all rights reserved.
 *
 * Contact: Rodrigo Novo <rodrigo.novo@nokia.com>
 *
 * This library is free software; you can redistribute it and/or
 * modify it under the terms of the GNU Lesser General Public License
 * as published by the Free Software Foundation; version 2.1 of
 * the License, or (at your option) any later version.
 *
 * This library 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
 * Lesser General Public License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public
 * License along with this library; if not, write to the Free Software
 * Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA
 * 02110-1301 USA
 *
 */

/**
 * SECTION:hildon-helper
 * @short_description: A collection of useful utilities and functions.
 *
 * Hildon provides some helper functions that can be used for commonly
 * performed tasks and functionality blocks. This includes operations
 * on widget styles and probing functions for touch events.
 */

#undef                                          HILDON_DISABLE_DEPRECATED

#ifdef                                          HAVE_CONFIG_H
#include                                        <config.h>
#endif

#define _GNU_SOURCE
#include                                        <string.h>
#include                                        "hildon-helper.h"
#include                                        "hildon-banner.h"

#define                                         HILDON_FINGER_PRESSURE_THRESHOLD 0.4

#define                                         HILDON_FINGER_BUTTON 8

#define                                         HILDON_FINGER_ALT_BUTTON 1

#define                                         HILDON_FINGER_ALT_MASK GDK_MOD4_MASK

#define                                         HILDON_FINGER_SIMULATE_BUTTON 2

struct                                          _HildonLogicalElement
{
    gboolean is_color;                          /* If FALSE, it's a logical font def */
    GtkRcFlags rc_flags;
    GtkStateType state;
    gchar *logical_color_name;
    gchar *logical_font_name;
} typedef                                       HildonLogicalElement;

static void
hildon_logical_element_list_free                (GSList *list)
{
    GSList *iterator = list;

    while (iterator) {
        HildonLogicalElement *element = (HildonLogicalElement *) iterator->data;

        g_free (element->logical_color_name);
        g_free (element->logical_font_name);
        g_slice_free (HildonLogicalElement, element);

        iterator = iterator->next;
    }

    /* Free the list itself */
    g_slist_free (list);
}

static GQuark
hildon_helper_logical_data_quark                (void)
{
    static GQuark quark = 0;

    if (G_UNLIKELY (quark == 0))
        quark = g_quark_from_static_string ("hildon-logical-data");

    return quark;
}

static HildonLogicalElement*
attach_blank_element                            (GtkWidget *widget, 
                                                 GSList **style_list)
{
    gboolean first = (*style_list == NULL) ? TRUE : FALSE;

    HildonLogicalElement *element = g_slice_new (HildonLogicalElement);
    
    element->is_color = FALSE;
    element->rc_flags = 0;
    element->state = 0;
    element->logical_color_name = NULL;
    element->logical_font_name = NULL;

    *style_list = g_slist_append (*style_list, element);

    if (first) 
        g_object_set_qdata_full (G_OBJECT (widget), hildon_helper_logical_data_quark (), *style_list, (GDestroyNotify) hildon_logical_element_list_free);

    return element;
}

static GSList*
attach_new_font_element                         (GtkWidget *widget, 
                                                 const gchar *font_name)
{
    GSList *style_list = g_object_get_qdata (G_OBJECT (widget), hildon_helper_logical_data_quark ());
    HildonLogicalElement *element = NULL;
   
    /* Try to find an element that already sets a font */
    GSList *iterator = style_list;
    while (iterator) {
        element = (HildonLogicalElement *) iterator->data;

        if (element->is_color == FALSE) {
            /* Reusing ... */
            g_free (element->logical_font_name);
            element->logical_font_name = g_strdup (font_name);
            return style_list;
        }

        iterator = iterator->next;
    }

    /* It was not found so we need to create a new one and attach it */
    element = attach_blank_element (widget, &style_list);
    element->is_color = FALSE;
    element->logical_font_name = g_strdup (font_name);
    return style_list;
}

static GSList*
attach_new_color_element                        (GtkWidget *widget, 
                                                 GtkRcFlags flags, 
                                                 GtkStateType state, 
                                                 const gchar *color_name)
{
    GSList *style_list = g_object_get_qdata (G_OBJECT (widget), hildon_helper_logical_data_quark ());
    HildonLogicalElement *element = NULL;
   
    /* Try to find an element that has same flags and state */
    GSList *iterator = style_list;
    while (iterator) {
        element = (HildonLogicalElement *) iterator->data;

        if (element->rc_flags == flags &&
            element->state == state &&
            element->is_color == TRUE) {
            /* Reusing ... */
            g_free (element->logical_color_name);
            element->logical_color_name = g_strdup (color_name);
            return style_list;
        }

        iterator = iterator->next;
    }

    /* It was not found so we need to create a new one and attach it */
    element = attach_blank_element (widget, &style_list);
    element->is_color = TRUE;
    element->state = state;
    element->rc_flags = flags;
    element->logical_color_name = g_strdup (color_name);
    return style_list;
}

static void 
hildon_change_style_recursive_from_list         (GtkWidget *widget, 
                                                 GtkStyle *prev_style, 
                                                 GSList *list)
{
    g_assert (GTK_IS_WIDGET (widget));

    /* Change the style for child widgets */
    if (GTK_IS_CONTAINER (widget)) {
        GList *iterator, *children;
        children = gtk_container_get_children (GTK_CONTAINER (widget));
        for (iterator = children; iterator != NULL; iterator = g_list_next (iterator))
            hildon_change_style_recursive_from_list (GTK_WIDGET (iterator->data), prev_style, list);
        g_list_free (children);
    }

    /* gtk_widget_modify_*() emit "style_set" signals, so if we got here from
       "style_set" signal, we need to block this function from being called
       again or we get into inifinite loop.

    FIXME: Compiling with gcc > 3.3 and -pedantic won't allow
    conversion between function and object pointers. GLib API however
    requires an object pointer for a function, so we have to work
    around this.
    See http://bugzilla.gnome.org/show_bug.cgi?id=310175
    */

    G_GNUC_EXTENSION
        g_signal_handlers_block_matched (G_OBJECT (widget), G_SIGNAL_MATCH_ID | G_SIGNAL_MATCH_FUNC,
                g_signal_lookup ("style_set", G_TYPE_FROM_INSTANCE (widget)),
                0, NULL,
                (gpointer) hildon_change_style_recursive_from_list,
                NULL);

    /* We iterate over all list elements and apply each style
     * specification. */

    GSList *iterator = list;
    while (iterator) {
    
        HildonLogicalElement *element = (HildonLogicalElement *) iterator->data;

        if (element->is_color == TRUE) {

            /* Changing logical color */
            GdkColor color;
            gtk_widget_ensure_style (widget);
            if (gtk_style_lookup_color (widget->style, element->logical_color_name, &color) == TRUE) {
               
                switch (element->rc_flags)
                {
                    case GTK_RC_FG:
                        gtk_widget_modify_fg (widget, element->state, &color);
                        break;

                    case GTK_RC_BG:
                        gtk_widget_modify_bg (widget, element->state, &color);
                        break;

                    case GTK_RC_TEXT:
                        gtk_widget_modify_text (widget, element->state, &color);
                        break;

                    case GTK_RC_BASE:
                        gtk_widget_modify_base (widget, element->state, &color);
                        break;
                }
            }
        } else {
            
            /* Changing logical font */
            GtkStyle *font_style = gtk_rc_get_style_by_paths (gtk_settings_get_default (), element->logical_font_name, NULL, G_TYPE_NONE);
            if (font_style != NULL) {
                PangoFontDescription *font_desc = font_style->font_desc;

                if (font_desc != NULL)
                    gtk_widget_modify_font (widget, font_desc);
            }
        }

        iterator = iterator->next;
    } 

    /* FIXME: Compilation workaround for gcc > 3.3 + -pedantic again */

    G_GNUC_EXTENSION
        g_signal_handlers_unblock_matched (G_OBJECT (widget), G_SIGNAL_MATCH_ID | G_SIGNAL_MATCH_FUNC,
                g_signal_lookup ("style_set", G_TYPE_FROM_INSTANCE (widget)),
                0, NULL,
                (gpointer) hildon_change_style_recursive_from_list,
                NULL);
}

/**
 * hildon_helper_event_button_is_finger:
 * @event: A #GtkEventButton to check
 *
 * Checks if the given button event is a finger event.
 *
 * Return value: TRUE if the event is a finger event.
 **/
gboolean 
hildon_helper_event_button_is_finger            (GdkEventButton *event)
{
    gdouble pressure;

    if (gdk_event_get_axis ((GdkEvent*) event, GDK_AXIS_PRESSURE, &pressure) &&
        pressure > HILDON_FINGER_PRESSURE_THRESHOLD)
        return TRUE;

    if (event->button == HILDON_FINGER_BUTTON)
        return TRUE;

    if (event->button == HILDON_FINGER_ALT_BUTTON &&
        event->state & HILDON_FINGER_ALT_MASK)
        return TRUE;

    if (event->button == HILDON_FINGER_SIMULATE_BUTTON)
        return TRUE;

    return FALSE;
}

/**
 * hildon_helper_set_logical_font:
 * @widget: a #GtkWidget to assign this logical font for.
 * @logicalfontname: a gchar* with the logical font name to assign to the widget.
 *
 * This function assigns a defined logical font to the @widget and all its child widgets.
 * it also connects to the "style_set" signal which will retrieve & assign the new font
 * for the given logical name each time the theme is changed
 * The returned signal id can be used to disconnect the signal.
 * When calling multiple times the previous signal (obtained by calling this function) is disconnected
 * automatically and should not be used.
 *
 * Return value: the signal id that is triggered every time theme is changed. 0 if font set failed.
 **/
gulong
hildon_helper_set_logical_font                  (GtkWidget *widget, 
                                                 const gchar *logicalfontname)
{
    gulong signum = 0;
    GSList *list;

    g_return_val_if_fail (GTK_IS_WIDGET (widget), 0);
    g_return_val_if_fail (logicalfontname != NULL, 0);

    list = attach_new_font_element (widget, logicalfontname);

    /* Disconnects the previously connected signals. That calls the closure notify
     * and effectively disposes the allocated data (hildon_logical_data_free) */
    g_signal_handlers_disconnect_matched (G_OBJECT (widget), G_SIGNAL_MATCH_FUNC, 
                                          0, 0, NULL, 
                                          G_CALLBACK (hildon_change_style_recursive_from_list), NULL);

    /* Change the font now */
    hildon_change_style_recursive_from_list (widget, NULL, list);

    /* Connect to "style_set" so that the font gets changed whenever theme changes. */
    signum = g_signal_connect_data (G_OBJECT (widget), "style_set",
                                    G_CALLBACK (hildon_change_style_recursive_from_list),
                                    list, NULL, 0);

    return signum;
}

static GQuark
hildon_helper_insensitive_message_quark         (void)
{
    static GQuark quark = 0;

    if (G_UNLIKELY (quark == 0))
        quark = g_quark_from_static_string ("hildon-insensitive-message");

    return quark;
}

static void
show_insensitive_message                        (GtkWidget *widget, 
                                                 gpointer user_data)
{
    gchar *message = NULL;

    g_assert (GTK_IS_WIDGET (widget));

    message = (gchar*) g_object_get_qdata (G_OBJECT (widget),
            hildon_helper_insensitive_message_quark ());

    if (message)
        hildon_banner_show_information (widget, NULL, message);
}


/**
 * hildon_helper_set_insensitive_message:
 * @widget: A #GtkWidget to assign a banner to
 * @message: A message to display to the user
 *
 * This function assigns an insensitive message to a @widget. When the @widget is
 * in an insensitive state and the user activates it, the @message will be displayed
 * using a standard #HildonBanner.
 *
 * Deprecated: As of hildon 2.2, it is strongly discouraged to use insensitive messages.
 **/
void
hildon_helper_set_insensitive_message           (GtkWidget *widget,
                                                 const gchar *message)
{
    g_return_if_fail (GTK_IS_WIDGET (widget));

    /* Clean up any previous instance of the insensitive message */
    g_signal_handlers_disconnect_matched (G_OBJECT (widget), G_SIGNAL_MATCH_FUNC,
					  0, 0, NULL,
					  G_CALLBACK (show_insensitive_message), NULL);
    
    /* We need to dup the string because the pointer might not be valid when the
     insensitive-press signal callback is executed */
    g_object_set_qdata_full (G_OBJECT (widget), hildon_helper_insensitive_message_quark (), 
			     (gpointer)g_strdup (message),
			     g_free);

    if (message != NULL) {
      g_signal_connect (G_OBJECT (widget), "insensitive-press",
			G_CALLBACK (show_insensitive_message), NULL);
    }
}

/**
 * hildon_helper_set_insensitive_messagef:
 * @widget: A #GtkWidget to assign a banner to
 * @format: a printf-like format string
 * @Varargs: arguments for the format string
 *
 * A version of hildon_helper_set_insensitive_message with string formatting.
 *
 * Deprecated: As of hildon 2.2, it is strongly discouraged to use insensitive messages.
 **/
void
hildon_helper_set_insensitive_messagef          (GtkWidget *widget,
                                                 const gchar *format,
                                                 ...)
{
    g_return_if_fail (GTK_IS_WIDGET (widget));

    gchar *message;
    va_list args;

    va_start (args, format);
    message = g_strdup_vprintf (format, args);
    va_end (args);

    hildon_helper_set_insensitive_message (widget, message);

    g_free (message);
}

/**
 * hildon_helper_set_logical_color:
 * @widget: A #GtkWidget to assign this logical font for.
 * @rcflags: #GtkRcFlags enumeration defining whether to assign to FG, BG, TEXT or BASE style.
 * @state: #GtkStateType indicating to which state to assign the logical color
 * @logicalcolorname: A gchar* with the logical font name to assign to the widget.
 * 
 * This function assigns a defined logical color to the @widget and all it's child widgets.
 * It also connects to the "style_set" signal which will retrieve & assign the new color 
 * for the given logical name each time the theme is changed.
 * The returned signal id can be used to disconnect the signal.
 * When calling multiple times the previous signal (obtained by calling this function) is disconnected 
 * automatically and should not be used. 
 * 
 * Example : If the style you want to modify is bg[NORMAL] then set rcflags to GTK_RC_BG and state to GTK_STATE_NORMAL.
 * 
 * Return value: The signal id that is triggered every time theme is changed. 0 if color set failed.
 **/
gulong 
hildon_helper_set_logical_color                 (GtkWidget *widget, 
                                                 GtkRcFlags rcflags,
                                                 GtkStateType state, 
                                                 const gchar *logicalcolorname)
{
    gulong signum = 0;
    GSList *list = NULL;

    g_return_val_if_fail (GTK_IS_WIDGET (widget), 0);
    g_return_val_if_fail (logicalcolorname != NULL, 0);
    
    list = attach_new_color_element (widget, rcflags, state, logicalcolorname);

    /* Disconnects the previously connected signals. */
    g_signal_handlers_disconnect_matched (G_OBJECT (widget), G_SIGNAL_MATCH_FUNC, 
                                          0, 0, NULL, 
                                          G_CALLBACK (hildon_change_style_recursive_from_list), NULL);

    /* Change the colors now */
    hildon_change_style_recursive_from_list (widget, NULL, list);

    /* Connect to "style_set" so that the colors gets changed whenever theme */
    signum = g_signal_connect_data (G_OBJECT (widget), "style_set",
                                    G_CALLBACK (hildon_change_style_recursive_from_list),
                                    list, NULL, 0);

    return signum;
}


/**
 * hildon_helper_set_thumb_scrollbar:
 * @win: A #GtkScrolledWindow to use as target
 * @thumb: TRUE to enable the thumb scrollbar, FALSE to disable
 *
 * This function enables a thumb scrollbar on a given scrolled window. It'll convert the
 * existing normal scrollbar into a larger, finger-usable scrollbar that works without a stylus.
 * As fingerable list rows are fairly high, consider using the whole available vertical space
 * of your application for the content in order to have as many rows as possible
 * visible on the screen at once.
 *
 * Finger-Sized scrollbar should always be used together with finger-sized content.
 **/
void
hildon_helper_set_thumb_scrollbar               (GtkScrolledWindow *win, 
                                                 gboolean thumb)
{
    g_return_if_fail (GTK_IS_SCROLLED_WINDOW (win));

    if (win->vscrollbar) 
        gtk_widget_set_name (win->vscrollbar, (thumb) ? "hildon-thumb-scrollbar" : NULL);
}

/**
 * hildon_format_file_size_for_display:
 * @size: a size in bytes
 *
 * Formats a file size in bytes for display in applications.
 *
 * This function is similar to g_format_file_size_for_display() but the
 * translations are from Maemo so might differ slightly.
 *
 * Since: 2.2
 **/
gchar *
hildon_format_file_size_for_display             (goffset size)
{
    #define _HFM(string) g_dgettext ("hildon-fm", string)

    if (size < 1024)
        return g_strdup_printf (_HFM ("ckdg_va_properties_size_kb"),
                                1);
    else if (size < 100 * 1024)
        return g_strdup_printf (_HFM ("ckdg_va_properties_size_1kb_99kb"),
                                (int)size / 1024);
    else if (size < 1024 * 1024)
        return g_strdup_printf (_HFM ("ckdg_va_properties_size_100kb_1mb"),
                                (int)size / 1024);
    else if (size < 10 * 1024 * 1024)
        return g_strdup_printf (_HFM ("ckdg_va_properties_size_1mb_10mb"),
                                size / (1024.0f * 1024.0f));
    else if (size < 1024 * 1024 * 1024)
        return g_strdup_printf (_HFM ("ckdg_va_properties_size_10mb_1gb"),
                                size / (1024.0f * 1024.0f));
    else
        return g_strdup_printf (_HFM ("ckdg_va_properties_size_1gb_or_greater"),
                                size / (1024.0f * 1024.0f * 1024.0f));
}


/**
 * stripped_char:
 *
 * Returns a stripped version of @ch, removing any case, accentuation
 * mark, or any special mark on it.
 **/
static gunichar
stripped_char (gunichar ch)
{
  gunichar *decomp, retval;
  GUnicodeType utype;
  gsize dlen;

  utype = g_unichar_type (ch);

  switch (utype) {
  case G_UNICODE_CONTROL:
  case G_UNICODE_FORMAT:
  case G_UNICODE_UNASSIGNED:
  case G_UNICODE_COMBINING_MARK:
    /* Ignore those */
    return 0;
    break;
  default:
    /* Convert to lowercase, fall through */
    ch = g_unichar_tolower (ch);
  case G_UNICODE_LOWERCASE_LETTER:
    if ((decomp = g_unicode_canonical_decomposition (ch, &dlen))) {
      retval = decomp[0];
      g_free (decomp);
      return retval;
    }
    break;
  }

  return 0;
}

static gchar *
e_util_unicode_get_utf8 (const gchar *text, gunichar *out)
{
  *out = g_utf8_get_char (text);
  return (*out == (gunichar)-1) ? NULL : g_utf8_next_char (text);
}

/**
 * get_next:
 * @p: a pointer to the string to search.
 * @o: a place to store the location of the next valid char.
 * @out: a place to store the next valid char.
 * @separators: whether to search only for alphanumeric strings
 * and skip any word separator.
 *
 * Gets the next character that is valid in our search scope, and
 * store it into @out. The next char, after @out is returned.
 *
 * Returns: the next point in the string @p where to continue the
 * string iteration.
 **/
static const gchar *
get_next (const gchar *p, const gchar **o, gunichar *out, gboolean separators)
{
  gunichar utf8;

  if (separators) {
    do {
       *o = p;
       p = e_util_unicode_get_utf8 (p, &utf8);
       *out = stripped_char (utf8);
    } while (p && utf8 && !g_unichar_isalnum (*out));
  } else {
    *o = p;
    p = e_util_unicode_get_utf8 (p, &utf8);
    *out = stripped_char (utf8);
  }

  return p;
}

/**
 * hildon_helper_utf8_strstrcasedecomp_needle_stripped:
 * @haystack: a haystack where to search
 * @nuni: a needle to search for, already stripped with hildon_helper_strip_string()
 *
 * Heavily modified version of e_util_utf8_strstrcasedecomp(). As its
 * original version, it finds the first occurrence of @nuni in
 * @haystack.  However, instead of stripping @nuni, it expect it to be
 * already stripped. See hildon_helper_strip_string().
 *
 * This is done for performance reasons, since this search is done
 * several times for the same string @nuni, it is undesired to strip
 * it more than once.
 *
 * Also, the search is done as a prefix search, starting in the first
 * alphanumeric character after any non-alphanumeric one. Searching
 * for "aba" in "Abasto" will match, searching in "Moraba" will not,
 * and searching in "A tool (abacus)" will do.
 *
 * Returns: the first instance of @nuni in @haystack
 *
 * Since: 2.2.18
 **/
const gchar *
hildon_helper_utf8_strstrcasedecomp_needle_stripped (const gchar *haystack, const gunichar *nuni)
{
  gunichar unival;
  gint nlen = 0;
  const gchar *o, *p;
  gunichar sc;

  if (haystack == NULL) return NULL;
  if (nuni == NULL) return NULL;
  if (strlen (haystack) == 0) return NULL;
  while (*(nuni + nlen) != 0) nlen++;

  if (nlen < 1) return haystack;

  for (p = get_next (haystack, &o, &sc, g_unichar_isalnum (nuni[0]));
       p && sc;
       p = get_next (p, &o, &sc, g_unichar_isalnum (nuni[0]))) {
    if (sc) {
      /* We have valid stripped gchar */
      if (sc == nuni[0]) {
        const gchar *q = p;
        gint npos = 1;
        while (npos < nlen) {
          q = e_util_unicode_get_utf8 (q, &unival);
          if (!q || !unival) return NULL;
          sc = stripped_char (unival);
          if ((!sc) || (sc != nuni[npos])) break;
          npos++;
        }
        if (npos == nlen) {
          return o;
        }
      }
    }
    while (p) {
      sc = g_utf8_get_char (p);
      if (!g_unichar_isalnum (sc))
        break;
      p = g_utf8_next_char (p);
    }
  }

  return NULL;
}

/**
 * hildon_helper_strip_string:
 * @string: a string to be stripped off.
 *
 * Strips all capitalization and accentuation marks from a string.
 * The returned Unicode string is %NULL-terminated.
 *
 * Returns: a newly allocated Unicode, lowercase, and without accentuation
 * marks version of @string, or %NULL if @string is an empty string.
 *
 * Since: 2.2.18
 **/
gunichar *
hildon_helper_strip_string (const gchar *string)
{
  gunichar *nuni;
  gint nlen;
  gunichar unival;
  const gchar *p;

  if (strlen (string) == 0) return NULL;

  nuni = g_malloc (sizeof (gunichar) * (strlen (string) + 1));

  nlen = 0;
  for (p = e_util_unicode_get_utf8 (string, &unival);
       p && unival;
       p = e_util_unicode_get_utf8 (p, &unival)) {
      gunichar sc;
      sc = stripped_char (unival);
      if (sc) {
          nuni[nlen++] = sc;
      }
  }

  /* NULL means there was illegal utf-8 sequence */
  if (!p) nlen = 0;

  nuni[nlen] = 0;

  return nuni;
}

/**
 * hildon_helper_normalize_string:
 * @string: a string
 *
 * Transform a string into an ascii equivalent representation.
 * This is necessary for hildon_helper_smart_match() to work properly.
 *
 * Returns: a newly allocated string.
 **/
gchar *
hildon_helper_normalize_string (const gchar *string)
{
    gchar *str = g_convert (string, -1, "ascii//translit", "utf-8", NULL, NULL, NULL);

    return str;
}

/**
 * hildon_helper_smart_match:
 * @haystack: a string where to find a match
 * @needle: what to find
 *
 * Searches for the first occurence of @needle in @haystack. The search
 * is performed only in the first alphanumeric character after a
 * sequence of non-alphanumeric ones. This allows smart matching of words
 * inside more complex strings.
 *
 * If @haystack itself doesn't start with an alphanumeric character,
 * then the search is equivalent to strcasecmp().
 *
 * To make the best of this method, it is recommended that both the needle
 * and the haystack are already normalized as ASCII strings. For this, you
 * should call hildon_helper_normalize_string() on both strings.
 *
 * Returns: a pointer to the first occurence of @needle in @haystack or %NULL
 * if not found
 **/
gchar *
hildon_helper_smart_match (const gchar *haystack, const gchar *needle)
{
    if (haystack == NULL) return NULL;
    if (needle == NULL) return NULL;
    if (strlen (haystack) == 0) return NULL;

    gboolean skip_separators = g_ascii_isalnum (needle[0]);

    if (skip_separators) {
        gint i = 0;
        while (haystack[i] != '\0') {
            while (haystack[i] != '\0' && !g_ascii_isalnum (haystack[i]))
                i++;
            if (g_ascii_strncasecmp (haystack + i, needle, strlen (needle)) == 0) {
                return (gchar *)haystack + i;
            }
            while (g_ascii_isalnum (haystack[i]))
                   i++;
        }
    } else {
        return strcasestr (haystack, needle);
    }

    return NULL;
}