use v6;

unit class File::Which::Win32;

use NativeCall;

try require Win32::Registry qw<&RegGetValueW &key-exists &open-key &close-key &wstr>;

method which(Str $exec, Bool :$all = False) {
  return Any unless $exec;
  fail("This only works on Windows") unless $*DISTRO.is-win;

  my @PATHEXT = '';
  # WinNT. PATHEXT might be set on Cygwin, but not used.
  if ( %*ENV<PATHEXT>.defined ) {
    @PATHEXT = flat( %*ENV<PATHEXT>.split(';') );
  } else {
    # Win9X or other: doesn't have PATHEXT, so needs hardcoded.
    @PATHEXT.push( <.com .exe .bat> );
  }

  my @results;

  my @path = flat( $*SPEC.path );

  for  @path.map({ $*SPEC.catfile($_, $exec) }) -> $base  {
    for @PATHEXT -> $ext {
      my $file = $base ~ $ext;

      # Ignore possibly -x directories
      next if $file.IO ~~ :d;

      # Windows systems don't pass -x on
      # non-exe/bat/com files. so we check -e.
      # However, we don't want to pass -e on files
      # that aren't in PATHEXT, like README.
      if @PATHEXT[1..@PATHEXT.elems - 1].grep({ $file.match(/ $_ $ /, :i) })
         && $file.IO ~~ :e
      {
        if $all {
          @results.push( $file );
        } else {
          return $file;
        }
      }
    }
  }

  return @results.unique if $all && @results;
  # Fallback to using win32 API to find executable location
  return self.which-win32-api($exec, @PATHEXT) || Any;
}

#
# Searches for and retrieves a file or protocol association-related string from the registry.
#
# https://msdn.microsoft.com/en-us/library/windows/desktop/bb773471%28v=vs.85%29.aspx
# https://source.winehq.org/WineAPI/AssocQueryStringA.html
#
sub AssocQueryStringA(uint32 $flags, uint32 $str, Str $assoc, uint32 $extra,
  CArray[uint8] $path, CArray[uint32] $out) returns uint32 is native('shlwapi') { * };

# This finds the executable path using the registry instead of the PATH
# environment variable
method which-win32-api(Str $exec, @paths) {
  constant ASSOCF_OPEN_BYEXENAME = 0x2;
  constant ASSOCSTR_EXECUTABLE   = 0x2;
  constant MAX_PATH              = 260;
  constant S_OK                  = 0;

  my $path = CArray[uint8].new;
  $path[$_] = 0 for 0..MAX_PATH - 1;

  my $size = CArray[uint32].new;
  $size[0] = MAX_PATH;
  my $hresult = &::("AssocQueryStringA")(ASSOCF_OPEN_BYEXENAME, ASSOCSTR_EXECUTABLE,
    $exec, 0, $path, $size);

  # Return nothing if it fails
  if $hresult == S_OK {
      # Compose path from CArray using the size DWORD (uint32)
      # Ignore null marker from null-terminated string
      my $exe-path = '';
      for 0 .. $size[0] - 2 {
          $exe-path ~= chr($path[$_]);
      }

      # Return the executable path string if found
      return $exe-path if $exe-path;
  }

  # search registry for apps
  my $has-extension = @paths.first({ $exec.ends-with($_, :i)}).so;

  my @keys-to-check;
  @keys-to-check = $has-extension
          ?? $exec
          !! @paths.map: { $exec ~ $_ } ;

  my @hives-to-check = <local_machine current_user>;
  my $key = 'SOFTWARE\Microsoft\Windows\CurrentVersion\App Paths';
  for @keys-to-check -> $k {
      for @hives-to-check -> $h {
          my $full-key = $h ~ "\\$key\\$k";
          if &::("key-exists")($full-key) {
              return get-path $full-key;
          }
      }
  }
}

sub get-path(Str:D $key) {
    my $k = &::("open-key")($key);

    my int32 $b = 600;
    my $value = CArray[uint16].new;
    $value[$_] = 0 for ^$b;

    my $blah = &::("RegGetValueW")($k, &::("wstr")(''), &::("wstr")(''), 0x0000ffff, 0,
            $value, $b);
    my $name = '';
    $value[$b] = 0;
    if !$blah {
        for ^$b {
            last if !$value[$_].so;
            $name ~= chr($value[$_]);
        }
    }
    &::("close-key")($k);

    # Sometimes, the path is surrounded by quotes for some reason. Remove them.
    $name.=trans( '"' => '');
    return $name;
}

=begin pod

=head1 NAME

File::Which::Win32 - Win32 which implementation

=head1 SYNOPSIS

  use File::Which::Win32;
  my $o = File::Which::Win32.new;
  say $o.which('raku');

=head1 DESCRIPTION

Implements the which method under win32-based platforms

=head1 METHODS

=head2 which

Returns the full executable path string

=head1 AUTHOR

Ahmad M. Zawawi <ahmad.zawawi@gmail.com>

=head1 COPYRIGHT AND LICENSE

Copyright 2016 Ahmad M. Zawawi

This library is free software; you can redistribute it and/or modify it under
the MIT License

=end pod