#!/usr/bin/env perl

use strict;

use Getopt::Std;

my %opts;

getopts('d:v:p:fmn', \%opts);

my $device = $opts{'d'};
if (!$device) {
    my $vid = $opts{'v'} || "046d";
    my $pid = $opts{'p'} || "c52b";

    $device = findDevice($vid, $pid);

}

my $hidraw = findHidRaw($device);

if (!$hidraw) {
    die("Unable to find Unifying Receiver");
}

if ($opts{'f'}) {
    open(F, ">/dev/$hidraw") || die("Unable to open /dev/$hidraw");
    print(F "\x10\x02\x0c\x1c\x00\x00\x00");
    close(F);
    if ($opts{'n'}) {
        system("notify-send 'Logitech K780' 'Function keys selected'");
    }
    print "Function keys selected\n";
    exit(0);
}
if ($opts{'m'}) {
    open(F, ">/dev/$hidraw") || die("Unable to open /dev/$hidraw");
    print(F "\x10\x02\x0c\x1c\x01\x00\x00");
    close(F);
    if ($opts{'n'}) {
        system("notify-send 'Logitech K780' 'Media keys selected'");
    }
    print "Media keys selected\n";
    exit(0);
}

print "$hidraw\n";

sub findHidRaw($) {
    my $device = shift;

    opendir(DIR, "/sys/bus/usb/devices/$device");
    while (my $file = readdir(DIR)) {
        if (substr($file, 0, length($device) + 1) eq "$device:") {
            opendir(SUBDIR, "/sys/bus/usb/devices/$device/$file");
            while (my $subfile = readdir(SUBDIR)) {
                if ($subfile =~ /^[0-9A-F]{4}:[0-9A-F]{4}:[0-9A-F]{4}\.[0-9A-F]{4}$/) {
                    if (-d "/sys/bus/usb/devices/$device/$file/$subfile/hidraw") {
                        opendir(HIDDIR, "/sys/bus/usb/devices/$device/$file/$subfile/hidraw");
                        while (my $hidfile = readdir(HIDDIR)) {
                            if ($hidfile =~ /^hidraw\d+$/) {
                                closedir(HIDDIR);
                                closedir(SUBDIR);
                                closedir(DIR);
                                return $hidfile;
                            }
                        }
                        closedir(HIDDIR);
                    }
                }
            }
            closedir(SUBDIR);
        }
    }
    closedir(DIR);
    return undef;
}

sub findDevice($$) {
    my $vid = shift;
    my $pid = shift;

    opendir(DIR, "/sys/bus/usb/devices");
    while (my $file = readdir(DIR)) {
        if (-f "/sys/bus/usb/devices/$file/idVendor") {
            open(F, "/sys/bus/usb/devices/$file/idVendor") || continue;
            my $testVid = <F>;
            close(F);
            chomp($testVid);
            open(F, "/sys/bus/usb/devices/$file/idProduct") || continue;
            my $testPid = <F>;
            close(F);
            chomp($testPid);

            if ((lc($vid) eq lc($testVid)) && (lc($pid) eq lc($testPid))) {
                closedir(DIR);
                return $file;
            }
        }
    }

    closedir(DIR);
    return undef;
}