#include "screensaver.h"

#include <QX11Info>
#include <QStringList>
#include <QProcess>
#include <X11/Xlib.h>
#include <X11/Xatom.h>

#ifdef X11_Xscreensaver_FOUND
#include <X11/extensions/scrnsaver.h>
#include <X11/Xutil.h>
#endif
#ifdef X11_dpms_FOUND
#include <X11/extensions/dpms.h>
#endif

namespace {

Display *display = nullptr;
bool extensionSupported = false;
bool dpmsSupported = false;
Atom XA_SCREENSAVER_VERSION, XA_SCREENSAVER_STATUS, XA_LOCK;
XErrorHandler old_handler = nullptr;
Bool got_badwindow = False;

bool init()
{
    if (display != nullptr) {
        return true;
    }
    display = QX11Info::display();
    if (display == nullptr) {
        return false;
    }
#ifdef X11_Xscreensaver_FOUND
    int dummy;
    extensionSupported = (XScreenSaverQueryExtension(display, &dummy, &dummy) == True);
    if (extensionSupported) {
        XA_SCREENSAVER_STATUS = XInternAtom( display, "_SCREENSAVER_STATUS", False );
        XA_SCREENSAVER_VERSION = XInternAtom( display, "_SCREENSAVER_VERSION",False );
        XA_LOCK = XInternAtom( display, "LOCK", False );
    }
#endif
#ifdef X11_dpms_FOUND
    dpmsSupported = (DPMSCapable(display) == True);
#endif
    return true;
}

static int BadWindow_ehandler( Display *dpy, XErrorEvent *error )
{
    if( error->error_code == BadWindow ) {
        got_badwindow = True;
        return 0;
    } else {
        if( !old_handler ) {
            abort();
        }
        return ( *old_handler )( dpy, error );
    }
}

#ifdef X11_Xscreensaver_FOUND
static Window find_screensaver_window( Display *dpy, char **version )
{
    unsigned int i;
    Window root = RootWindowOfScreen( DefaultScreenOfDisplay( dpy ) );
    Window root2, parent, *kids;
    unsigned int nkids;

    if( version ) {
        *version = 0;
    }

    if( ! XQueryTree( dpy, root, &root2, &parent, &kids, &nkids ) ) {
        abort();
    }
    if( root != root2 ) {
        abort();
    }
    if( parent ) {
        abort();
    }
    if( !( kids && nkids ) ) {
        return 0;
    }
    for( i = 0; i < nkids; i++ ) {
        Atom type;
        int format;
        unsigned long nitems, bytesafter;
        unsigned char *v;
        int status;

        /* We're walking the list of root-level windows and trying to find
               the one that has a particular property on it.  We need to trap
               BadWindows errors while doing this, because it's possible that
               some random window might get deleted in the meantime.  (That
               window won't have been the one we're looking for.)
             */
        XSync( dpy, False );
        if( old_handler ) {
            abort();
        }
        got_badwindow = False;
        old_handler = XSetErrorHandler( BadWindow_ehandler );
        status = XGetWindowProperty( dpy, kids[i],
                                     XA_SCREENSAVER_VERSION,
                                     0, 200, False, XA_STRING,
                                     &type, &format, &nitems, &bytesafter,
                                     &v );
        XSync( dpy, False );
        XSetErrorHandler( old_handler );
        old_handler = nullptr;

        if( got_badwindow ) {
            status = BadWindow;
            got_badwindow = False;
        }

        if( status == Success && type != None ) {
            Window ret = kids[i];
            if( version ) {
                *version = ( char* )v;
            }
            XFree( kids );
            return ret;
        }
    }

    if( kids ) {
        XFree( kids );
    }
    return 0;
}
#endif

}

/*
 * Main attraction
 */

namespace ScreenSaver {

void allowSaverAndStandby(bool allow)
{
    if (!init())
        return;
#ifdef X11_Xscreensaver_FOUND
    if (extensionSupported) {
        XScreenSaverSuspend(display, allow ? False : True);
        return;
    }
#endif
    // TODO: Maybe try some fallback, call xset, or trigger some event periodically
}

void forceScreenOn()
{
    if (!init())
        return;
#ifdef X11_dpms_FOUND
    CARD16 power_level;
    BOOL state;
    if (DPMSInfo(display, &power_level, &state) && state) {
        DPMSForceLevel(display, DPMSModeOn);
        return;
    }
#endif
}

bool isLocked()
{
#ifdef X11_Xscreensaver_FOUND
    if (!init())
        return false;
    char *v = nullptr;
    Window window = find_screensaver_window( display, &v );
    if( !window )
        return false;
    if( !v || !*v )
        return false;
    XClassHint hint;
    memset( &hint, 0, sizeof( hint ) );
    XGetClassHint( display, window, &hint );
    if( !hint.res_class )
        return false;

    Atom type;
    int format;
    unsigned long nitems, bytesafter;
    Atom *data = nullptr;
    if( XGetWindowProperty( display,
                            RootWindow( display, 0 ),
                            XA_SCREENSAVER_STATUS,
                            0, 999, False, XA_INTEGER,
                            &type, &format, &nitems, &bytesafter,
                            reinterpret_cast<unsigned char**>(&data) )
            != Success
            || !type
            || data == nullptr )
        return false;
    if( type != XA_INTEGER || nitems < 3 ) {
        if( data ) {
            free( data );
        }
        return false;
    }

    Atom blanked = ( Atom ) data[0];
    if( blanked == XA_LOCK )
        return true; // Yay
#endif
    return false;
}

}