package qz.utils;

import com.sun.jna.Library;
import com.sun.jna.Native;
import com.sun.jna.Pointer;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

import java.lang.reflect.Method;

public class GtkUtilities {
    private static final Logger log = LoggerFactory.getLogger(GtkUtilities.class);

    /**
     * Initializes Gtk2/3 and returns the desktop scaling factor, usually 1.0 or 2.0
     */
    public static double getScaleFactor() {
        GTK gtkHandle = getGtkInstance();
        if (gtkHandle != null && gtkHandle.gtk_init_check(0, null)) {
            log.debug("Initialized Gtk");

            if (gtkHandle instanceof GTK2) {
                return getGtk2ScaleFactor((GTK2)gtkHandle);
            } else {
                return getGtk3ScaleFactor((GTK3)gtkHandle);
            }
        } else {
            log.warn("An error occurred initializing the Gtk library");
        }
        return 0;
    }

    private static GTK getGtkInstance() {
        log.debug("Finding preferred Gtk version...");
        switch(getGtkMajorVersion()) {
            case 2:
                return GTK2.INSTANCE;
            case 3:
                return GTK3.INSTANCE;
            default:
                log.warn("Not a compatible Gtk version");
        }
        return null;
    }

    /**
     * Get the major version of Gtk (e.g. 2, 3)
     * UNIXToolkit is unavailable on Windows or Mac; reflection is required.
     * @return Major version if found, zero if not.
     */
    private static int getGtkMajorVersion() {
        try {
            Class toolkitClass = Class.forName("sun.awt.UNIXToolkit");
            Method versionMethod = toolkitClass.getDeclaredMethod("getGtkVersion");
            Enum versionInfo = (Enum)versionMethod.invoke(toolkitClass);
            Method numberMethod = versionInfo.getClass().getDeclaredMethod("getNumber");
            int version = ((Integer)numberMethod.invoke(versionInfo)).intValue();
            log.debug("Found Gtk{}", version);
            return version;
        } catch(Throwable t) {
            log.warn("Could not obtain GtkVersion information from UNIXToolkit: {}", t.getMessage());
        }
        return 0;
    }

    private static double getGtk2ScaleFactor(GTK2 gtk2) {
        Pointer display = gtk2.gdk_display_get_default();
        log.debug("Gtk 2.10+ detected, calling \"gdk_screen_get_resolution\"");
        Pointer screen = gtk2.gdk_display_get_default_screen(display);
        return gtk2.gdk_screen_get_resolution(screen) / 96.0d;
    }

    private static double getGtk3ScaleFactor(GTK3 gtk3) {
        Pointer display = gtk3.gdk_display_get_default();
        int gtkMinorVersion = gtk3.gtk_get_minor_version();
        if (gtkMinorVersion < 10) {
            log.warn("Gtk 3.10+ is required to detect scaling factor, skipping.");
        } else if (gtkMinorVersion >= 22) {
            log.debug("Gtk 3.22+ detected, calling \"gdk_monitor_get_scale_factor\"");
            Pointer monitor = gtk3.gdk_display_get_primary_monitor(display);
            return gtk3.gdk_monitor_get_scale_factor(monitor);
        } else if (gtkMinorVersion >= 10) {
            log.debug("Gtk 3.10+ detected, calling \"gdk_screen_get_monitor_scale_factor\"");
            Pointer screen = gtk3.gdk_display_get_default_screen(display);
            return gtk3.gdk_screen_get_monitor_scale_factor(screen, 0);
        }
        return 0;
    }

    /**
     * Gtk2/Gtk3 wrapper
     */
    private interface GTK extends Library {
        // Gtk2.0+
        boolean gtk_init_check(int argc, String[] argv);
        Pointer gdk_display_get_default();
        Pointer gdk_display_get_default_screen (Pointer display);
    }

    private interface GTK3 extends GTK {
        GTK3 INSTANCE = Native.loadLibrary("gtk-3", GTK3.class);

        // Gtk 3.0+
        int gtk_get_minor_version ();

        // Gtk 3.10-3.21
        int gdk_screen_get_monitor_scale_factor (Pointer screen, int monitor_num);

        // Gtk 3.22+
        Pointer gdk_display_get_primary_monitor (Pointer display);
        int gdk_monitor_get_scale_factor (Pointer monitor);
    }

    private interface GTK2 extends GTK {
        GTK2 INSTANCE = Native.loadLibrary("gtk-x11-2.0", GTK2.class);

        // Gtk 2.1-3.0
        double gdk_screen_get_resolution(Pointer screen);
    }
}