/**
 * sublime-imfix.c
 * Use LD_PRELOAD to interpose some function to fix sublime input method support for linux.
 * By Cjacker Huang <jianzhong.huang at i-soft.com.cn>
 * By whitequark@whitequark.org
 *
 * How to compile:
 * gcc -shared -o libsublime-imfix.so sublime_imfix.c `pkg-config --libs --cflags gtk+-2.0` -fPIC
 * How to use:
 * LD_PRELOAD=./libsublime-imfix.so sublime_text
 *
 * Changes:
 * 2014 06-09
 * 1. Fix cursor position update for sublime text 3.
 * 2. Combine the codes from whitequark(fix for xim immodule) and add cursor update support for XIM immodule.
 */

/* for RTLD_NEXT */
#define _GNU_SOURCE

#include <assert.h>
#include <dlfcn.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>

#include <gtk/gtk.h>
#include <gdk/gdkx.h>
#include <X11/Xlib.h>
#include <X11/Xutil.h>

#ifdef VERBOSE
#define DEBUG(fmt, ...) do { \
        FILE* err = fopen("/tmp/libsublime-immethod-fix.log", "a"); \
        if (err) { \
            fprintf(err, fmt, __VA_ARGS__); \
            fclose(err); \
        } \
    } while(0)
#else
#define DEBUG(fmt, ...)
#endif

typedef GdkSegment GdkRegionBox;

struct _GdkRegion {
    long size;
    long numRects;
    GdkRegionBox *rects;
    GdkRegionBox extents;
};

GtkIMContext *local_context;

// This function is added to prevent some bugs caused by subprocess inheriting `LD_PRELOAD` settings
// For example, without it, `Preferences - Browse Packages` function won't work.
void __attribute__((constructor)) on_load(void) {
    // Clear `LD_PRELOAD` environment variable
    putenv("LD_PRELOAD=");
}

// this func is interposed to support cursor position update.
void
gdk_region_get_clipbox(const GdkRegion *region,
                       GdkRectangle    *rectangle) {
    g_return_if_fail(region != NULL);
    g_return_if_fail(rectangle != NULL);

    rectangle->x = region->extents.x1;
    rectangle->y = region->extents.y1;
    rectangle->width = region->extents.x2 - region->extents.x1;
    rectangle->height = region->extents.y2 - region->extents.y1;
    GdkRectangle rect;
    rect.x = rectangle->x;
    rect.y = rectangle->y;
    rect.width = 0;
    rect.height = rectangle->height;
    // The caret width is 2 in sublime text 2
    // And is 1 in sublime text 3.
    // Maybe sometimes we will make a mistake, but for most of the time, it should be the caret.
    if ((rectangle->width == 2 || rectangle->width == 1)  && GTK_IS_IM_CONTEXT(local_context)) {
        gtk_im_context_set_cursor_location(local_context, rectangle);
    }
}

// this is needed, for example, if you input something in file dialog and return back the edit area
// context will lost, so here we set it again.
static GdkFilterReturn event_filter(GdkXEvent *xevent, GdkEvent *event, gpointer im_context) {
    XEvent *xev = (XEvent *)xevent;
    if (xev->type == KeyRelease && GTK_IS_IM_CONTEXT(im_context)) {
        GdkWindow *win = g_object_get_data(G_OBJECT(im_context), "window");
        if (GDK_IS_WINDOW(win)) {
            gtk_im_context_set_client_window(im_context, win);
        }
    }
    return GDK_FILTER_CONTINUE;
}

void gtk_im_context_set_client_window(GtkIMContext *context,
                                      GdkWindow    *window) {
    GtkIMContextClass *klass;
    g_return_if_fail(GTK_IS_IM_CONTEXT(context));
    klass = GTK_IM_CONTEXT_GET_CLASS(context);
    if (klass->set_client_window) {
        klass->set_client_window(context, window);
    }

    //below is our interposed codes to save the context to local_context.
    if (!GDK_IS_WINDOW(window)) {
        return;
    }
    g_object_set_data(G_OBJECT(context), "window", window);
    int width = gdk_window_get_width(window);
    int height = gdk_window_get_height(window);
    if (width != 0 && height != 0) {
        gtk_im_context_focus_in(context);
        local_context = context;
    }
    //only add this event_filter when using 'fcitx' immodule.
    //for xim immodule, this function is as same as original from gtk2.
    const gchar *immodule = g_getenv("GTK_IM_MODULE");
    if (immodule && !strcmp(immodule, "fcitx")) {
        gdk_window_add_filter(window, event_filter, context);
    }
}


/* The following codes are from whitequark, fix for xim immodule */

/* See gtkimcontextxim.c */
GType gtk_type_im_context_xim = 0;

#define GTK_TYPE_IM_CONTEXT_XIM            (gtk_type_im_context_xim)
#define GTK_IM_CONTEXT_XIM(obj)            (G_TYPE_CHECK_INSTANCE_CAST ((obj), GTK_TYPE_IM_CONTEXT_XIM, GtkIMContextXIM))
#define GTK_IM_CONTEXT_XIM_CLASS(klass)    (G_TYPE_CHECK_CLASS_CAST ((klass), GTK_TYPE_IM_CONTEXT_XIM, GtkIMContextXIMClass))
#define GTK_IS_IM_CONTEXT_XIM(obj)         (G_TYPE_CHECK_INSTANCE_TYPE ((obj), GTK_TYPE_IM_CONTEXT_XIM))
#define GTK_IS_IM_CONTEXT_XIM_CLASS(klass) (G_TYPE_CHECK_CLASS_TYPE ((klass), GTK_TYPE_IM_CONTEXT_XIM))
#define GTK_IM_CONTEXT_XIM_GET_CLASS(obj)  (G_TYPE_INSTANCE_GET_CLASS ((obj), GTK_TYPE_IM_CONTEXT_XIM, GtkIMContextXIMClass))

typedef struct _GtkIMContextXIM       GtkIMContextXIM;
typedef struct _GtkIMContextXIMClass  GtkIMContextXIMClass;

struct _GtkIMContextXIMClass {
    GtkIMContextClass parent_class;
};

typedef struct _StatusWindow StatusWindow;
typedef struct _GtkXIMInfo GtkXIMInfo;

struct _GtkIMContextXIM {
    GtkIMContext object;

    GtkXIMInfo *im_info;

    gchar *locale;
    gchar *mb_charset;

    GdkWindow *client_window;
    GtkWidget *client_widget;

    /* The status window for this input context; we claim the
     *     status window when we are focused and have created an XIC
     */
    StatusWindow *status_window;

    gint preedit_size;
    gint preedit_length;
    gunichar *preedit_chars;
    XIMFeedback *feedbacks;

    gint preedit_cursor;

    XIMCallback preedit_start_callback;
    XIMCallback preedit_done_callback;
    XIMCallback preedit_draw_callback;
    XIMCallback preedit_caret_callback;

    XIMCallback status_start_callback;
    XIMCallback status_done_callback;
    XIMCallback status_draw_callback;

    XIMCallback string_conversion_callback;

    XIC ic;

    guint filter_key_release : 1;
    guint use_preedit : 1;
    guint finalizing : 1;
    guint in_toplevel : 1;
    guint has_focus : 1;
};

static GClassInitFunc orig_gtk_im_context_xim_class_init;
static GType(*orig_g_type_module_register_type)(GTypeModule *,
        GType, const gchar *,
        const GTypeInfo *, GTypeFlags);
static gboolean(*orig_gtk_im_context_xim_filter_keypress)(GtkIMContext *context,
        GdkEventKey *event);

static gboolean
hook_gtk_im_context_xim_filter_keypress(GtkIMContext *context, GdkEventKey *event) {
    GtkIMContextXIM *im_context_xim = GTK_IM_CONTEXT_XIM(context);
    if (!im_context_xim->client_window) {
        DEBUG("im_context_xim == %p\n", im_context_xim);
        DEBUG("event->window == %p\n", event->window);

        gtk_im_context_set_client_window(context, event->window);
    }

    return orig_gtk_im_context_xim_filter_keypress(context, event);
}

static void
hook_gtk_im_context_xim_class_init(GtkIMContextXIMClass *class) {
    orig_gtk_im_context_xim_class_init(class, NULL); /* wat? */

    GtkIMContextClass *im_context_class = GTK_IM_CONTEXT_CLASS(class);

    assert(!orig_gtk_im_context_xim_filter_keypress);
    orig_gtk_im_context_xim_filter_keypress = im_context_class->filter_keypress;
    im_context_class->filter_keypress = hook_gtk_im_context_xim_filter_keypress;
    DEBUG("orig_gtk_im_context_xim_filter_keypress: %p\n",
          orig_gtk_im_context_xim_filter_keypress);
}

GType
g_type_module_register_type(GTypeModule *module,
                            GType parent_type,
                            const gchar *type_name,
                            const GTypeInfo *type_info,
                            GTypeFlags flags) {
    if (!orig_g_type_module_register_type) {
        orig_g_type_module_register_type = dlsym(RTLD_NEXT, "g_type_module_register_type");
        assert(orig_g_type_module_register_type);
    }

    if (type_name && !strcmp(type_name, "GtkIMContextXIM")) {
        assert(!orig_gtk_im_context_xim_class_init);
        orig_gtk_im_context_xim_class_init = type_info->class_init;

        assert(sizeof(GtkIMContextXIM) == type_info->instance_size);

        const GTypeInfo hook_im_context_xim_info = {
            type_info->class_size,
            type_info->base_init,
            type_info->base_finalize,
            (GClassInitFunc) hook_gtk_im_context_xim_class_init,
            type_info->class_finalize,
            type_info->class_data,
            type_info->instance_size,
            type_info->n_preallocs,
            type_info->instance_init,
        };

        DEBUG("orig_gtk_im_context_xim_class_init: %p\n", orig_gtk_im_context_xim_class_init);

        gtk_type_im_context_xim =
            orig_g_type_module_register_type(module, parent_type, type_name,
                                             &hook_im_context_xim_info, flags);

        return gtk_type_im_context_xim;
    }

    return orig_g_type_module_register_type(module, parent_type, type_name, type_info, flags);
}