#!/usr/bin/perl

use strict;
use warnings;

use Win32;
use Win32::API;
use Win32::API::Callback;

my $org_title = "Unbenannt - Editor";
my $new_title = "Hacked by esskar! :-)";

my $EnumWindows   = Win32::API->new( "user32", "EnumWindows",      "PN",  "N" );
my $EnumChildWnds = Win32::API->new( "user32", "EnumChildWindows", "NKN", "N" );
my $FindWindowEx  = Win32::API->new( "user32", "FindWindowEx",  "NNPP", "N" );
my $GetClassName  = Win32::API->new( "user32", "GetClassName",  "NPN",  "N" );
my $SetWindowText = Win32::API->new( "user32", "SetWindowText", "NP",   "N" );
my $PostMessage   = Win32::API->new( "user32", "PostMessage",   "NNNN", "N" );

my $hwnd = $FindWindowEx->Call( 0, 0, "Notepad", 0 );
die "Window not found." unless $hwnd;

my $editHwnd        = 0;
my $EnumWindowsProc = Win32::API::Callback->new(
    sub {
        my ( $hwnd, $param ) = @_;

        my $className = " " x 256;
        my $len       =
          $GetClassName->Call( $hwnd, $className, length($className) - 1 );
        $className = substr( $className, 0, $len );

        if ( lc $className eq 'edit' ) {
            $editHwnd = $hwnd;
            return 0;
        }

        return 1;
    },
    "NN",
    "N"
);
$EnumChildWnds->Call( $hwnd, $EnumWindowsProc, 0 );

die "Edit Window not found." unless $editHwnd;

$SetWindowText->Call( $hwnd, $new_title );
&write_to_window( $editHwnd, "Just a test!\n" );

use constant WM_CHAR => 258;
sub write_to_window {
    my ( $hwnd, $text ) = @_;

    my @chars = split //, $text;
    foreach my $c (@chars) {
        $PostMessage->Call($hwnd, WM_CHAR, ord $c, 0);
    }
}