package CGI::Uploader::Transform::ImageMagick;

use base 'Exporter';
use File::Temp 'tempfile';
use Params::Validate ':all';
use Carp::Assert;
use vars qw(@EXPORT $VERSION);

$VERSION = 2.17;

@EXPORT = qw(&gen_thumb);

=head2 gen_thumb()

  use CGI::Uploader::Transform::ImageMagick;

As a class method:

 ($thumb_tmp_filename)  = CGI::Uploader::Transform::ImageMagick->gen_thumb({
    filename => $orig_filename, 
           w => $width, 
           h => $height 
    });

Within a CGI::Uploader C<spec>:

    gen_files => {
      my_thumb => gen_thumb({ w => $width, h => $height }),
    }

Looking for a different syntax? See L<BACKWARDS COMPATIBILITY>

This function creates a copy of given image file and resizes the copy to the
provided width and height.

C<gen_thumb> can be called as object or class method. As a class method,
there there is no need to call C<new()> before calling this method.

L<Graphics::Magick> is used as the first choice image service module.
L<Image::Magick> is tried next. 

Input:

    filename - filename of source image 
    w        - max width of thumbnail
    h        - max height of thumbnail

One or both  of C<w> or C<h> is required.

Output:
    - filename of generated tmp file for the thumbnail 
    - the initialized image generation object. (You generally shouldn't need this)

=cut

sub gen_thumb  {
    # If the first arg is an object, we have really work to do right now
    my $first_arg = $_[0];
    use Scalar::Util (qw/blessed/);
    if ((blessed $first_arg) or (eval {$first_arg->can('gen_thumb')})) {
        return _really_gen_thumb(@_);
    }
    # Otherwise, just generate a closure pass back a code ref for later use
    else {
        # require a single hashref as input
        my ($args_href) = validate_pos(@_, { type => HASHREF });
        return sub {
            my $self = shift;
            my $filename = shift;
            _really_gen_thumb($self, {
                    filename => $filename, 
                    %$args_href,
                });
        }
    }
}

sub _really_gen_thumb {
    my $self = shift || die "gen_thumb needs object";
    my (%p,$orig_filename,$params);
    # If we have the new hashref API
    if (ref $_[0] eq 'HASH') {
        %p = validate(@_,{ 
                filename => { type => SCALAR },
                w => { type => SCALAR | UNDEF, regex => qr/^\d*$/, optional => 1, },
                h => { type => SCALAR | UNDEF, regex => qr/^\d*$/, optional => 1 },
            });
        $orig_filename = $p{filename};
    }
    # we have the old ugly style API
    else {
        ($orig_filename, $params) = validate_pos(@_,1,{ type => ARRAYREF });
        # validate handles a hash or hashref transparently
        %p = validate(@$params,{ 
                w => { type => SCALAR | UNDEF, regex => qr/^\d*$/, optional => 1, },
                h => { type => SCALAR | UNDEF, regex => qr/^\d*$/, optional => 1 },
            });
    }
    die "must supply 'w' or 'h'" unless (defined $p{w} or defined $p{h});

    # Having both Graphics::Magick and Image::Magick loaded at the same time
    # can cause very strange problems, so we take care to avoid that
    # First see if we have already loaded Graphics::Magick or Image::Magick
    # If so, just use whichever one is already loaded.
    my $magick_module;
    if (exists $INC{'Graphics/Magick.pm'}) {
        $magick_module = 'Graphics::Magick';
    }
    elsif (exists $INC{'Image/Magick.pm'}) {
        $magick_module = 'Image::Magick';
    }

    # If neither are already loaded, try loading either one.
    elsif ( _load_magick_module('Graphics::Magick') ) {
        $magick_module = 'Graphics::Magick';
    }
    elsif ( _load_magick_module('Image::Magick') ) {
        $magick_module = 'Image::Magick';
    }
    else {
        die "No graphics module found for image resizing. Install Graphics::Magick or Image::Magick: $@ "
    }

    my ($thumb_tmp_fh, $thumb_tmp_filename) = tempfile('CGIuploaderXXXXX', UNLINK => 1, DIR => $self->{'temp_dir'});
    binmode($thumb_tmp_fh);

    my $img = $magick_module->new();

    my $err;
    eval {
        $err = $img->Read(filename=>$orig_filename);
        die "Error while reading $orig_filename: $err" if $err;

        my ($target_w,$target_h) = _calc_target_size($img,$p{w},$p{h});

        $err = $img->Resize($target_w.'x'.$target_h); 
        die "Error while resizing $orig_filename: $err" if $err;
        $err = $img->Write($thumb_tmp_filename);
        die "Error while writing $orig_filename: $err" if $err;
    };
    if ($@) {
        warn $@;
        my $code;
        # codes > 400 are fatal 
        die $err if ((($code) = $err =~ /(\d+)/) and ($code > 400));
    }

    assert ($thumb_tmp_filename, 'thumbnail tmp file created');
    return wantarray ? ($thumb_tmp_filename, $img ) :  $thumb_tmp_filename;

}


# Calculate the target with height
# 
# my ($target_w,$target_h) = _calc_target_size($img,$p{w},$p{h})
# 
# Input:
# 
#   - Magick object, pre-opened with the original file
#   - provided width
#   - provided height

sub _calc_target_size {
    my ($img,$w,$h) = @_;

    my $target_h = $h;
    my $target_w = $w;
    my ($orig_w,$orig_h) = $img->Get('width','height');

    $target_h = sprintf("%.1d", ($orig_h * $target_w) / $orig_w) unless $target_h;
    $target_w = sprintf("%.1d", ($orig_w * $target_h) / $orig_h) unless $target_w;

    return ($target_w,$target_h);

}




# load Graphics::Magick or Image::Magick if one is not already loaded.
sub _load_magick_module {
    my $module_name = shift;
    return eval "require $module_name";
}

=head2 BACKWARDS COMPATIBILITY

These older, more awkward syntaxes are still supported: 

As a class method:

 ($thumb_tmp_filename)  = CGI::Uploader::Transform::ImageMagick->gen_thumb(
    $orig_filename, 
    [ w => $width, h => $height ]
    );

In a C<CGI::Uploader> C<spec>:

'my_img_field_name' => {
    transform_method => \&gen_thumb,                                                                    
    params => [ w => 100, h => 100 ],                                                             
  }                                                                                                         


1;