/* Copyright (C) 2006 Openismus GmbH
 * 
 * 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; either
 * version 2 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., 59 Temple Place - Suite 330,
 * Boston, MA 02111-1307, USA.
 */

#include <config.h>
#include <string.h>
#include <gtk/gtk.h>
#include <gdk/gdkkeysyms.h>
#include <gtk/gtkimmodule.h>
#include "gtkimcontextmultipress.h"

#define AUTOMATIC_COMPOSE_TIMEOUT 1 /* seconds */

#define CONFIGURATION_FILENAME MULTIPRESS_CONFDIR G_DIR_SEPARATOR_S "im-multipress.conf"

#define MULTIPRESS_PASSTHROUGH_FLAG "multipress-passthrough-flag"

/** This contains rows of characters that can be inputed by pressing a particular key repeatedly.
 * Each row has one key (such as GDK_A), and an array of characters, such as 'a'.
 */
struct _KeySequence
{
  gunichar key_press; /* Such as 'a' (== GDK_a) */
  gchar **characters; /* Array of strings. */
  gsize characters_length; /* size of the array of strings. */
};

static void gtk_im_context_multipress_class_init (GtkImContextMultipressClass *klass);
static void gtk_im_context_multipress_init (GtkImContextMultipress *self);
static void gtk_im_context_multipress_finalize (GObject *obj);

static void gtk_im_context_multipress_load_config (GtkImContextMultipress *self);

static GObjectClass *gtk_im_context_multipress_parent_class = NULL;
static GType gtk_im_multi_press_im_context_type = 0;

/* Notice that we have a *_register_type(GTypeModule*) function instead of a
 * *_get_type() function, because we must use g_type_module_register_type(),
 * providing the GTypeModule* that was provided to im_context_init(). That
 * is also why we are not using G_DEFINE_TYPE().
 */
void
gtk_im_context_multipress_register_type (GTypeModule* type_module)
{
  static const GTypeInfo im_context_multipress_info =
  {
    sizeof (GtkImContextMultipressClass),
    (GBaseInitFunc) NULL,
    (GBaseFinalizeFunc) NULL,
    (GClassInitFunc) gtk_im_context_multipress_class_init,
    NULL,
    NULL,
    sizeof (GtkImContextMultipress),
    0,
    (GInstanceInitFunc) gtk_im_context_multipress_init,
    0,
  };

  gtk_im_multi_press_im_context_type =
    g_type_module_register_type (type_module,
                                 GTK_TYPE_IM_CONTEXT,
                                 "GtkImContextMultipress",
                                 &im_context_multipress_info, 0);
}

GType
gtk_im_context_multipress_get_type (void)
{
  g_assert (gtk_im_multi_press_im_context_type != 0);
  return gtk_im_multi_press_im_context_type;
}

/*
 * Returns TRUE if the passthrough flag is set on the currently focused
 * child of the widget that owns the GDK window.  In order to turn on
 * passthrough mode, call:
 * g_object_set_data (widget, "multipress-passthrough-flag", GINT_TO_POINTER (1));
 */
static gboolean 
passthrough_enabled_for_window (GdkWindow* window)
{
  gpointer event_widget = NULL;

  g_return_val_if_fail (window != NULL, FALSE);
  /*
   * For historical reasons, GTK+ assumes the user data attached to a GdkWindow
   * to point to the GtkWidget that owns the window.  It's even documented:
   * http://developer.gnome.org/doc/API/2.0/gdk/gdk-Windows.html#gdk-window-set-user-data
   * So we are really lucky here, as this allows us to attach IM state
   * information to a widget in a fairly straightforward manner.
   */
  gdk_window_get_user_data (window, &event_widget);

  if (event_widget && GTK_IS_WIDGET (event_widget))
  {
    GtkWidget *toplevel;
    GtkWidget *focus_widget;
    /*
     * The event window for key presses will usually belong to the toplevel
     * GtkWindow, but that might not be true for synthetic events.  In any
     * case we need to find the currently focused child widget.
     */
    toplevel = gtk_widget_get_toplevel ((GtkWidget *)event_widget);

    g_return_val_if_fail (toplevel != NULL && GTK_IS_WINDOW (toplevel), FALSE);

    focus_widget = gtk_window_get_focus ((GtkWindow *)toplevel);

    if (focus_widget)
    {
      static GQuark quark_passthrough_flag = 0;

      if (!quark_passthrough_flag)
        quark_passthrough_flag = g_quark_from_string (MULTIPRESS_PASSTHROUGH_FLAG);

      if (g_object_get_qdata (G_OBJECT (focus_widget), quark_passthrough_flag))
        return TRUE;
    }
  }

  return FALSE;
}

static gboolean vfunc_filter_keypress (GtkIMContext *context,
									   GdkEventKey  *event);
static void vfunc_reset (GtkIMContext *context);
static void vfunc_get_preedit_string (GtkIMContext   *context,
					                  gchar         **str,
					                  PangoAttrList **attrs,
					                  gint           *cursor_pos);

static void
gtk_im_context_multipress_class_init (GtkImContextMultipressClass *klass)
{
  GtkIMContextClass* im_context_class;

  /* Set this so we can use it later: */
  gtk_im_context_multipress_parent_class = g_type_class_peek_parent (klass);

  /* Specify our vfunc implementations: */
  im_context_class = GTK_IM_CONTEXT_CLASS (klass);
  im_context_class->filter_keypress = vfunc_filter_keypress;
  im_context_class->reset = vfunc_reset;
  im_context_class->get_preedit_string = vfunc_get_preedit_string;

  G_OBJECT_CLASS (klass)->finalize = gtk_im_context_multipress_finalize;
}

static void
gtk_im_context_multipress_init (GtkImContextMultipress *self)
{
  gtk_im_context_multipress_load_config (self);
}

static void
gtk_im_context_multipress_finalize (GObject *obj)
{
  GtkImContextMultipress *self = GTK_IM_CONTEXT_MULTIPRESS (obj);
   
  /* Release the configuration data: */

  /* Free each item: */
  gsize i = 0;
  for (i = 0; i < self->key_sequences_count; ++i)
  {
    KeySequence *item = self->key_sequences[i];

    /* Free the array of strings in the item: */
    /* This is only for null-terminated arrays: g_strfreev(item->characters); */
    gsize i = 0;
    for (i = 0; i < item->characters_length; ++i)
    {
      gchar *str = item->characters[i];
      g_free (str);
      item->characters[i] = NULL;
    }

    g_free (item->characters);
    item->characters = NULL;
    item->characters_length = 0;

    /* Free the item itself: */
    g_free (item);
  }

  /* Free the array of pointers: */
  g_free (self->key_sequences);

  self->key_sequences = NULL;
  self->key_sequences_count = 0;

    
  gtk_im_context_multipress_parent_class->finalize (obj);
}


GtkIMContext
*gtk_im_context_multipress_new (void)
{
  return (GtkIMContext *)g_object_new (GTK_TYPE_IM_CONTEXT_MULTIPRESS, NULL);
}

/* Lookup a compose sequence for the key press, from the table.  The result is
 * a null-terminated array of gchar*. It should not be freed by the caller.
 */
static KeySequence *
lookup_characters (GtkImContextMultipress *multipress_context, guint keypress)
{

  /* Find the matching KeySequence, so that the caller can look at the possible
   * characters for this keypress: */
  gsize i = 0;
  for (i = 0; i < multipress_context->key_sequences_count; ++i)
  {
    KeySequence *item = multipress_context->key_sequences[i];

    /* Just compare the first item, to match the keyval: */
    if (keypress == item->key_press)
      return item;
  }

  return NULL;
}

static void
cancel_automatic_timeout_commit (GtkImContextMultipress *multipress_context)
{
  /* printf("debug: cancelling timeout\n"); */

  if (multipress_context->timeout_id)
    g_source_remove (multipress_context->timeout_id);
 
  multipress_context->timeout_id = 0;
}


/* Clear the compose buffer, so we are ready to compose the next character.
 */
static void
clear_compose_buffer (GtkImContextMultipress *multipress_context)
{
  multipress_context->key_last_entered = 0;
  multipress_context->compose_count = 0;

  multipress_context->tentative_match = NULL;
  cancel_automatic_timeout_commit (multipress_context);

  g_signal_emit_by_name (multipress_context, "preedit-changed");
  g_signal_emit_by_name (multipress_context, "preedit-end");
}

/* Finish composing, provide the character, and clear our compose buffer.
 */
static void
accept_character (GtkImContextMultipress *multipress_context, const gchar *characters)
{
  /* Clear the compose buffer, so we are ready to compose the next character.
   * Note that if we emit "preedit-changed" after "commit", there's a segfault/
   * invalid-write with GtkTextView in gtk_text_layout_free_line_display(), when
   * destroying a PangoLayout (this can also be avoided by not using any Pango
   * attributes in get_preedit_string(). */
  clear_compose_buffer (multipress_context);

  /* Provide the character to GTK+ */
  g_signal_emit_by_name (multipress_context, "commit", characters);
}

static gboolean
on_timeout (gpointer data)
{
  GtkImContextMultipress *multipress_context;

  GDK_THREADS_ENTER();

  /* printf("debug: on_timeout\n"); */

  multipress_context = GTK_IM_CONTEXT_MULTIPRESS (data);

  /* A certain amount of time has passed, so we will assume that the user
   * really wants the currently chosen character */
  accept_character (multipress_context, multipress_context->tentative_match);

  multipress_context->timeout_id = 0;

  GDK_THREADS_LEAVE();

  return FALSE; /* don't call me again */
}

static gboolean
vfunc_filter_keypress (GtkIMContext *context, GdkEventKey *event)
{
  GtkIMContextClass *parent;
  GtkImContextMultipress *multipress_context;

  /* printf("debug: vfunc_filter_keypress:\n"); */

  multipress_context = GTK_IM_CONTEXT_MULTIPRESS (context);

  if (event->type == GDK_KEY_PRESS)
  {
    KeySequence *possible = NULL;

    /* printf("debug: multipress_context->compose_count=%d\n", multipress_context->compose_count); */

    /* Check whether the current key is the same as previously entered, because
	 * if it is not then we should accept the previous one, and start a new
	 * character. */
    if (multipress_context->compose_count > 0
		&& multipress_context->key_last_entered != event->keyval)
	{
	  /* Accept the previously chosen character: */
	  if (multipress_context->tentative_match)
	  {
	    /* This wipes the compose_count and key_last_entered. */
	    accept_character (multipress_context, multipress_context->tentative_match);
	  } 
	}

    /* Decide what character this key press would choose: */
    if (!passthrough_enabled_for_window (event->window))
      possible = lookup_characters (multipress_context, event->keyval); /* Not to be freed. */

    if (possible)
    {
      if (multipress_context->compose_count == 0)
        g_signal_emit_by_name (multipress_context, "preedit-start");

      /* Check whether we are at the end of a compose sequence, with no more possible characters: */
      /* Cycle back to the start if necessary: */
      if (multipress_context->compose_count >= possible->characters_length)
        multipress_context->compose_count = 0;

      /* Store the last key pressed in the compose sequence. */
      multipress_context->key_last_entered = event->keyval; 

      /* Get the possible match for this number of presses of the key.
       * compose_count starts at 1, so that 0 can mean not composing. */ 
      multipress_context->tentative_match = possible->characters[multipress_context->compose_count++];

      /* Indicate the current possible character.
       * This will cause our vfunc_get_preedit_string() vfunc to be called, 
       * which will provide the current possible character for the user to see.
       */
      g_signal_emit_by_name (multipress_context, "preedit-changed");
      
      /* Cancel any outstanding timeout, so we can start the timer again: */
      cancel_automatic_timeout_commit (multipress_context);

      /* Create a timeout that will cause the currently chosen character to be committed,
       * if nothing happens for a certain amount of time:
       */
      multipress_context->timeout_id = g_timeout_add_seconds
		  (AUTOMATIC_COMPOSE_TIMEOUT, on_timeout, multipress_context);

      return TRUE; /* TRUE means that the event was handled. */
    }
    else
    {
      guint32 keyval_uchar;

      /*
       * Just accept all other keypresses directly, but commit the
       * current preedit content first.
       */
      if (multipress_context->compose_count > 0 && multipress_context->tentative_match)
        accept_character (multipress_context, multipress_context->tentative_match);

      keyval_uchar = gdk_keyval_to_unicode (event->keyval);
      /*
       * Convert to a string, because that's what accept_character() needs.
       */
      if (keyval_uchar)
      {
        gchar keyval_utf8[7]; /* max length of UTF-8 sequence + 1 for NUL termination */
        gint  length;

        length = g_unichar_to_utf8 (keyval_uchar, keyval_utf8);
        keyval_utf8[length] = '\0';

        accept_character (multipress_context, keyval_utf8);

        return TRUE; /* key handled */
      }
    }
  }

  /* The default implementation just returns FALSE, 
   * but it is generally a good idea to call the base class implementation:
   */
  parent = (GtkIMContextClass *)gtk_im_context_multipress_parent_class;
  if (parent->filter_keypress)
    return parent->filter_keypress (context, event);
  else
    return FALSE;
}

static void 
vfunc_reset (GtkIMContext *context)
{
  GtkImContextMultipress *multipress_context = GTK_IM_CONTEXT_MULTIPRESS (context);

  clear_compose_buffer (multipress_context);
}


static void 
vfunc_get_preedit_string (GtkIMContext   *context,
                          gchar         **str,
                          PangoAttrList **attrs,
                          gint           *cursor_pos)
{
  /* printf("debug: get_preedit_string:\n"); */

  GtkImContextMultipress *multipress_context = GTK_IM_CONTEXT_MULTIPRESS (context);

  /* Show the user what character he will get if he accepts: */
  gsize len_bytes = 0;
  gsize len_utf8_chars = 0;
  if (str)
  {
    if (multipress_context->tentative_match)
    {
      /*
      printf("debug: vfunc_get_preedit_string(): tentative_match != NULL\n");
      printf("debug: vfunc_get_preedit_string(): tentative_match=%s\n", multipress_context->tentative_match);
      */
      *str = g_strdup (multipress_context->tentative_match);
    }
    else
    {
      /* *str can never be NULL - that crashes the caller, which doesn't check for it: */
      *str = g_strdup("");
    }

    if (*str)
    {
      len_utf8_chars = g_utf8_strlen (*str, -1); /* For the cursor pos, which seems need to be UTF-8 characters (GtkEntry clamps it.) */
      len_bytes = strlen (*str); /* The number of bytes, not the number of UTF-8 characters. For the PangoAttribute. */ 
    }
  }

  /* Underline it, to show the user that he is in compose mode: */
  if (attrs)
    {
      *attrs = pango_attr_list_new ();

      if (len_bytes)
        {
          PangoAttribute *attr = pango_attr_underline_new (PANGO_UNDERLINE_SINGLE);
          attr->start_index = 0;
          attr->end_index = len_bytes;
          pango_attr_list_insert (*attrs, attr);
        }
  }

  if (cursor_pos)
    *cursor_pos = len_utf8_chars;
}

static void 
gtk_im_context_multipress_load_config (GtkImContextMultipress *self)
{
  /* Open the configuration file: */
  GKeyFile *key_file;
  GError *error = NULL;
  GArray *array;
  gboolean found;
  guint key_suffix_num = 0;
  gboolean keep_looking = TRUE;

  key_file = g_key_file_new ();
  found = g_key_file_load_from_file (key_file, CONFIGURATION_FILENAME, G_KEY_FILE_NONE, &error);
  if (!found || error)
  {
    if (error)
    {
      g_warning ("Error while trying to open the %s configuration file: %s", CONFIGURATION_FILENAME, error->message);
      g_error_free (error);
      error = NULL;

      /*debug_output_possible_data_dirs();*/
    }

    g_key_file_free (key_file);
    return;
  }

  /* Get data from the file:
   * Each KP_* key should have a value consiting of ;-separated values: */

  array = g_array_sized_new (FALSE /* Not zero_terminated */, TRUE /* clear */,
                            sizeof(KeySequence*), 10 /* reserved size */);

  /* Look at each KP_* key in sequence, until there are no more KP_* keys: */
  while (keep_looking)
  {
    gchar* key_name;
    gchar** values;
    gsize length_values = 0;

    key_name = g_strdup_printf ("KP_%d", key_suffix_num);
    values = g_key_file_get_string_list (key_file, "keys", key_name, &length_values, &error);
    if (error)
    {
      /* Only show the warning if this was the first key. It's OK to fail when trying to find subsequent keys: */
      if (key_suffix_num == 0)
      {
        g_warning ("Error while trying to read key values from the configuration file: %s", error->message);
      }

      g_error_free (error);
      error = NULL;
    }

    if (!values)
    {
       /* printf("debug: No values found for key %s\n", key_name); */
       keep_looking = FALSE; /* This must be the last in the array of keys. */
       /* debug_output_possible_config_keys(key_file); */
    }
    else
    {
      KeySequence *key_sequence;
      GArray *array_characters;
      gsize value_index = 0;

      key_sequence = g_new0 (KeySequence, 1);
      g_array_append_val (array, key_sequence);   

      array_characters = g_array_sized_new (FALSE /* Not zero_terminated */, TRUE /* clear */,
                                           sizeof(gchar*), 10 /* reserved size */);

      for (value_index = 0; value_index < length_values; ++value_index)
      {
        gchar *value;
        gchar *value_copy;

        value = values[value_index];

        if (value_index == 0)
        {
          g_assert (strlen(value) > 0);

          key_sequence->key_press = g_utf8_get_char (value);
        }

        value_copy = g_strdup (value);
        g_array_append_val (array_characters, value_copy);

        /* printf("debug: Key=%s, value=%s\n", key_name, value); */
      }

      g_strfreev (values);

      key_sequence->characters_length = array_characters->len;
      key_sequence->characters = (gchar **)g_array_free(array_characters,
          FALSE /* Don't free items - return a real array of them. */);
    }

    g_free (key_name);
    ++key_suffix_num;
  }

  g_key_file_free (key_file);

  self->key_sequences_count = array->len;
  self->key_sequences = (KeySequence **)g_array_free (array,
      FALSE /* Don't free items - return a real array of them. */);

  /* debug_output_key_sequences_array(self); */
}