package Slic3r::Print;
use Moo;

use File::Basename qw(basename fileparse);
use File::Spec;
use List::Util qw(min max first);
use Math::ConvexHull::MonotoneChain qw(convex_hull);
use Slic3r::ExtrusionPath ':roles';
use Slic3r::Geometry qw(X Y Z X1 Y1 X2 Y2 MIN MAX PI scale unscale move_points chained_path);
use Slic3r::Geometry::Clipper qw(diff_ex union_ex union_pt intersection_ex intersection offset
    offset2 traverse_pt JT_ROUND JT_SQUARE);
use Time::HiRes qw(gettimeofday tv_interval);

has 'config'                 => (is => 'rw', default => sub { Slic3r::Config->new_from_defaults }, trigger => 1);
has 'extra_variables'        => (is => 'rw', default => sub {{}});
has 'objects'                => (is => 'rw', default => sub {[]});
has 'processing_time'        => (is => 'rw');
has 'extruders'              => (is => 'rw', default => sub {[]});
has 'regions'                => (is => 'rw', default => sub {[]});
has 'support_material_flow'  => (is => 'rw');
has 'first_layer_support_material_flow' => (is => 'rw');
has 'has_support_material'   => (is => 'lazy');

# ordered collection of extrusion paths to build skirt loops
has 'skirt' => (is => 'rw', default => sub { Slic3r::ExtrusionPath::Collection->new });

# ordered collection of extrusion paths to build a brim
has 'brim' => (is => 'rw', default => sub { Slic3r::ExtrusionPath::Collection->new });

sub BUILD {
    my $self = shift;
    
    # call this manually because the 'default' coderef doesn't trigger the trigger
    $self->_trigger_config;
}

sub _trigger_config {
    my $self = shift;
    
    # store config in a handy place
    $Slic3r::Config = $self->config;
    
    # legacy with existing config files
    $self->config->set('first_layer_height', $self->config->layer_height)
        if !$self->config->first_layer_height;
    $self->config->set_ifndef('small_perimeter_speed',  $self->config->perimeter_speed);
    $self->config->set_ifndef('bridge_speed',           $self->config->infill_speed);
    $self->config->set_ifndef('solid_infill_speed',     $self->config->infill_speed);
    $self->config->set_ifndef('top_solid_infill_speed', $self->config->solid_infill_speed);
    $self->config->set_ifndef('top_solid_layers',       $self->config->solid_layers);
    $self->config->set_ifndef('bottom_solid_layers',    $self->config->solid_layers);
    
    # G-code flavors
    $self->config->set('extrusion_axis', 'A') if $self->config->gcode_flavor eq 'mach3';
    $self->config->set('extrusion_axis', '')  if $self->config->gcode_flavor eq 'no-extrusion';
    
    # enforce some settings when spiral_vase is set
    if ($self->config->spiral_vase) {
        $self->config->set('perimeters', 1);
        $self->config->set('fill_density', 0);
        $self->config->set('top_solid_layers', 0);
        $self->config->set('support_material', 0);
        $self->config->set('support_material_enforce_layers', 0);
        $self->config->set('retract_layer_change', [0]);  # TODO: only apply this to the spiral layers
    }
    
    # force all retraction lift values to be the same
    $self->config->set('retract_lift', [ map $self->config->retract_lift->[0], @{$self->config->retract_lift} ]);
}

sub _build_has_support_material {
    my $self = shift;
    return (first { $_->config->support_material } @{$self->objects})
        || (first { $_->config->raft_layers > 0 } @{$self->objects})
        || (first { $_->config->support_material_enforce_layers > 0 } @{$self->objects});
}

# caller is responsible for supplying models whose objects don't collide
# and have explicit instance positions
sub add_model {
    my $self = shift;
    my ($model) = @_;
    
    # optimization: if avoid_crossing_perimeters is enabled, split
    # this mesh into distinct objects so that we reduce the complexity
    # of the graphs 
    # -- Disabling this one because there are too many legit objects having nested shells
    # -- It also caused a bug where plater rotation was applied to each single object by the
    # -- code below (thus around its own center), instead of being applied to the whole 
    # -- thing before the split.
    ###$model->split_meshes if $Slic3r::Config->avoid_crossing_perimeters && !$Slic3r::Config->complete_objects;
    
    my %unmapped_materials = ();
    foreach my $object (@{ $model->objects }) {
        # we align object to origin before applying transformations
        my @align = $object->align_to_origin;
        
        # extract meshes by material
        my @meshes = ();  # by region_id
        foreach my $volume (@{$object->volumes}) {
            my $region_id;
            if (defined $volume->material_id) {
                if ($object->material_mapping) {
                    $region_id = $object->material_mapping->{$volume->material_id} - 1
                        if defined $object->material_mapping->{$volume->material_id};
                }
                $region_id //= $unmapped_materials{$volume->material_id};
                if (!defined $region_id) {
                    $region_id = $unmapped_materials{$volume->material_id} = scalar(keys %unmapped_materials);
                }
            }
            $region_id //= 0;
            
            my $mesh = $volume->mesh->clone;
            # should the object contain multiple volumes of the same material, merge them
            $meshes[$region_id] = $meshes[$region_id]
                ? Slic3r::TriangleMesh->merge($meshes[$region_id], $mesh)
                : $mesh;
        }
        $self->regions->[$_] //= Slic3r::Print::Region->new for 0..$#meshes;
        
        foreach my $mesh (grep $_, @meshes) {
            # the order of these transformations must be the same as the one used in plater
            # to make the object positioning consistent with the visual preview
            
            # we ignore the per-instance transformations currently and only 
            # consider the first one
            if ($object->instances && @{$object->instances}) {
                $mesh->rotate($object->instances->[0]->rotation, $object->center_2D);
                $mesh->scale($object->instances->[0]->scaling_factor);
            }
            
            $mesh->scale(1 / &Slic3r::SCALING_FACTOR);
            $mesh->repair;
        }
        
        # we also align object after transformations so that we only work with positive coordinates
        # and the assumption that bounding_box === size works
        my $bb = Slic3r::Geometry::BoundingBox->merge(map $_->bounding_box, grep $_, @meshes);
        my @align2 = map -$bb->extents->[$_][MIN], (X,Y,Z);
        $_->translate(@align2) for grep $_, @meshes;
        
        # initialize print object
        push @{$self->objects}, Slic3r::Print::Object->new(
            print       => $self,
            meshes      => [ @meshes ],
            copies      => [
                map Slic3r::Point->new(@$_),
                $object->instances
                    ? (map [ scale($_->offset->[X] - $align[X]) - $align2[X], scale($_->offset->[Y] - $align[Y]) - $align2[Y] ], @{$object->instances})
                    : [0,0],
            ],
            size        => $bb->size,  # transformed size
            input_file  => $object->input_file,
            config_overrides    => $object->config,
            layer_height_ranges => $object->layer_height_ranges,
        );
    }
    
    if (!defined $self->extra_variables->{input_filename}) {
        if (defined (my $input_file = $self->objects->[0]->input_file)) {
            @{$self->extra_variables}{qw(input_filename input_filename_base)} = parse_filename($input_file);
        }
    }
}

sub validate {
    my $self = shift;
    
    if ($Slic3r::Config->complete_objects) {
        # check horizontal clearance
        {
            my @a = ();
            for my $obj_idx (0 .. $#{$self->objects}) {
                my $clearance;
                {
                    my @points = map [ @$_[X,Y] ], map @{$_->vertices}, @{$self->objects->[$obj_idx]->meshes};
                    my $convex_hull = Slic3r::Polygon->new(@{convex_hull(\@points)});
                    ($clearance) = @{offset([$convex_hull], scale $Slic3r::Config->extruder_clearance_radius / 2, 1, JT_ROUND)};
                }
                for my $copy (@{$self->objects->[$obj_idx]->copies}) {
                    my $copy_clearance = $clearance->clone;
                    $copy_clearance->translate(@$copy);
                    if (@{ intersection(\@a, [$copy_clearance]) }) {
                        die "Some objects are too close; your extruder will collide with them.\n";
                    }
                    @a = map $_->clone, map @$_, @{union_ex([ @a, $copy_clearance ])};
                }
            }
        }
        
        # check vertical clearance
        {
            my @object_height = ();
            foreach my $object (@{$self->objects}) {
                my $height = $object->size->[Z];
                push @object_height, $height for @{$object->copies};
            }
            @object_height = sort { $a <=> $b } @object_height;
            # ignore the tallest *copy* (this is why we repeat height for all of them):
            # it will be printed as last one so its height doesn't matter
            pop @object_height;
            if (@object_height && max(@object_height) > scale $Slic3r::Config->extruder_clearance_height) {
                die "Some objects are too tall and cannot be printed without extruder collisions.\n";
            }
        }
    }
    
    if ($Slic3r::Config->spiral_vase) {
        if ((map @{$_->copies}, @{$self->objects}) > 1) {
            die "The Spiral Vase option can only be used when printing a single object.\n";
        }
        if (@{$self->regions} > 1) {
            die "The Spiral Vase option can only be used when printing single material objects.\n";
        }
    }
}

sub init_extruders {
    my $self = shift;
    
    # map regions to extruders (ghetto mapping for now)
    my %extruder_mapping = map { $_ => $_ } 0..$#{$self->regions};
    
    # initialize all extruder(s) we need
    my @used_extruders = (
        0,
        (map $self->config->get("${_}_extruder")-1, qw(perimeter infill support_material support_material_interface)),
        (values %extruder_mapping),
    );
    for my $extruder_id (keys %{{ map {$_ => 1} @used_extruders }}) {
        $self->extruders->[$extruder_id] = Slic3r::Extruder->new(
            config => $self->config,
            id => $extruder_id,
            map { $_ => $self->config->get($_)->[$extruder_id] // $self->config->get($_)->[0] } #/
                @{&Slic3r::Extruder::OPTIONS}
        );
    }
    
    # calculate regions' flows
    for my $region_id (0 .. $#{$self->regions}) {
        my $region = $self->regions->[$region_id];
        
        # per-role extruders and flows
        for (qw(perimeter infill solid_infill top_infill)) {
            my $extruder_name = $_;
            $extruder_name =~ s/^(?:solid|top)_//;
            $region->extruders->{$_} = ($self->regions_count > 1)
                ? $self->extruders->[$extruder_mapping{$region_id}]
                : $self->extruders->[$self->config->get("${extruder_name}_extruder")-1];
            $region->flows->{$_} = $region->extruders->{$_}->make_flow(
                width => $self->config->get("${_}_extrusion_width") || $self->config->extrusion_width,
                role  => $_,
            );
            $region->first_layer_flows->{$_} = $region->extruders->{$_}->make_flow(
                layer_height    => $self->config->get_value('first_layer_height'),
                width           => $self->config->first_layer_extrusion_width,
                role            => $_,
            ) if $self->config->first_layer_extrusion_width;
        }
    }
    
    # calculate support material flow
    # Note: we should calculate a different flow for support material interface
    if ($self->has_support_material) {
        my $extruder = $self->extruders->[$self->config->support_material_extruder-1];
        $self->support_material_flow($extruder->make_flow(
            width => $self->config->support_material_extrusion_width || $self->config->extrusion_width,
            role  => 'support_material',
        ));
        $self->first_layer_support_material_flow($extruder->make_flow(
            layer_height    => $self->config->get_value('first_layer_height'),
            width           => $self->config->first_layer_extrusion_width,
            role            => 'support_material',
        ));
    }
    
    # enforce tall skirt if using ooze_prevention
    # NOTE: this is not idempotent (i.e. switching ooze_prevention off will not revert skirt settings)
    if ($self->config->ooze_prevention && @{$self->extruders} > 1) {
        $self->config->set('skirt_height', 9999999999);
        $self->config->set('skirts', 1) if $self->config->skirts == 0;
    }
}

# this value is not supposed to be compared with $layer->id
# since they have different semantics
sub layer_count {
    my $self = shift;
    return max(map $_->layer_count, @{$self->objects});
}

sub regions_count {
    my $self = shift;
    return scalar @{$self->regions};
}

sub bounding_box {
    my $self = shift;
    
    my @points = ();
    foreach my $object (@{$self->objects}) {
        foreach my $copy (@{$object->copies}) {
            push @points,
                [ $copy->[X], $copy->[Y] ],
                [ $copy->[X] + $object->size->[X], $copy->[Y] + $object->size->[Y] ];
        }
    }
    return Slic3r::Geometry::BoundingBox->new_from_points([ map Slic3r::Point->new(@$_), @points ]);
}

sub size {
    my $self = shift;
    return $self->bounding_box->size;
}

sub _simplify_slices {
    my $self = shift;
    my ($distance) = @_;
    
    foreach my $layer (map @{$_->layers}, @{$self->objects}) {
        my @new = map $_->simplify($distance), map $_->clone, @{$layer->slices};
        $layer->slices->clear;
        $layer->slices->append(@new);
        foreach my $layerm (@{$layer->regions}) {
            my @new = map $_->simplify($distance), map $_->clone, @{$layerm->slices};
            $layerm->slices->clear;
            $layerm->slices->append(@new);
        }
    }
}

sub export_gcode {
    my $self = shift;
    my %params = @_;
    
    $self->init_extruders;
    my $status_cb = $params{status_cb} || sub {};
    my $t0 = [gettimeofday];
    
    # skein the STL into layers
    # each layer has surfaces with holes
    $status_cb->(10, "Processing triangulated mesh");
    $_->slice for @{$self->objects};
    
    # remove empty layers and abort if there are no more
    # as some algorithms assume all objects have at least one layer
    # note: this will change object indexes
    @{$self->objects} = grep @{$_->layers}, @{$self->objects};
    die "No layers were detected. You might want to repair your STL file(s) or check their size and retry.\n"
        if !@{$self->objects};
    
    if ($Slic3r::Config->resolution) {
        $status_cb->(15, "Simplifying input");
        $self->_simplify_slices(scale $Slic3r::Config->resolution);
    }
    
    # make perimeters
    # this will add a set of extrusion loops to each layer
    # as well as generate infill boundaries
    $status_cb->(20, "Generating perimeters");
    $_->make_perimeters for @{$self->objects};
    
    # simplify slices (both layer and region slices),
    # we only need the max resolution for perimeters
    $self->_simplify_slices(&Slic3r::SCALED_RESOLUTION);
    
    # this will assign a type (top/bottom/internal) to $layerm->slices
    # and transform $layerm->fill_surfaces from expolygon 
    # to typed top/bottom/internal surfaces;
    $status_cb->(30, "Detecting solid surfaces");
    $_->detect_surfaces_type for @{$self->objects};
    
    # decide what surfaces are to be filled
    $status_cb->(35, "Preparing infill surfaces");
    $_->prepare_fill_surfaces for map @{$_->regions}, map @{$_->layers}, @{$self->objects};
    
    # this will detect bridges and reverse bridges
    # and rearrange top/bottom/internal surfaces
    $status_cb->(45, "Detect bridges");
    $_->process_external_surfaces for @{$self->objects};
    
    # detect which fill surfaces are near external layers
    # they will be split in internal and internal-solid surfaces
    $status_cb->(60, "Generating horizontal shells");
    $_->discover_horizontal_shells for @{$self->objects};
    $_->clip_fill_surfaces for @{$self->objects};
    # the following step needs to be done before combination because it may need
    # to remove only half of the combined infill
    $_->bridge_over_infill for @{$self->objects};
    
    # combine fill surfaces to honor the "infill every N layers" option
    $status_cb->(70, "Combining infill");
    $_->combine_infill for @{$self->objects};
    
    # this will generate extrusion paths for each layer
    $status_cb->(80, "Infilling layers");
    {
        Slic3r::parallelize(
            items => sub {
                my @items = ();  # [obj_idx, layer_id]
                for my $obj_idx (0 .. $#{$self->objects}) {
                    my $object = $self->objects->[$obj_idx];
                    for my $region_id (0 .. $#{$self->regions}) {
                        push @items, map [$obj_idx, $_, $region_id], 0..$#{$object->layers};
                    }
                }
                @items;
            },
            thread_cb => sub {
                my $q = shift;
                while (defined (my $obj_layer = $q->dequeue)) {
                    my ($obj_idx, $layer_i, $region_id) = @$obj_layer;
                    my $object = $self->objects->[$obj_idx];
                    my $layerm = $object->layers->[$layer_i]->regions->[$region_id];
                    $layerm->fills->append( $object->fill_maker->make_fill($layerm) );
                }
            },
            collect_cb => sub {},
            no_threads_cb => sub {
                foreach my $layerm (map @{$_->regions}, map @{$_->layers}, @{$self->objects}) {
                    $layerm->fills->append($layerm->layer->object->fill_maker->make_fill($layerm));
                }
            },
        );
    }
    
    # generate support material
    if ($self->has_support_material) {
        $status_cb->(85, "Generating support material");
        $_->generate_support_material for @{$self->objects};
    }
    
    # free memory (note that support material needs fill_surfaces)
    $_->fill_surfaces->clear for map @{$_->regions}, map @{$_->layers}, @{$self->objects};
    
    # make skirt
    $status_cb->(88, "Generating skirt");
    $self->make_skirt;
    $self->make_brim;  # must come after make_skirt
    
    # time to make some statistics
    if (0) {
        eval "use Devel::Size";
        print  "MEMORY USAGE:\n";
        printf "  meshes        = %.1fMb\n", List::Util::sum(map Devel::Size::total_size($_->meshes), @{$self->objects})/1024/1024;
        printf "  layer slices  = %.1fMb\n", List::Util::sum(map Devel::Size::total_size($_->slices), map @{$_->layers}, @{$self->objects})/1024/1024;
        printf "  region slices = %.1fMb\n", List::Util::sum(map Devel::Size::total_size($_->slices), map @{$_->regions}, map @{$_->layers}, @{$self->objects})/1024/1024;
        printf "  perimeters    = %.1fMb\n", List::Util::sum(map Devel::Size::total_size($_->perimeters), map @{$_->regions}, map @{$_->layers}, @{$self->objects})/1024/1024;
        printf "  fills         = %.1fMb\n", List::Util::sum(map Devel::Size::total_size($_->fills), map @{$_->regions}, map @{$_->layers}, @{$self->objects})/1024/1024;
        printf "  print object  = %.1fMb\n", Devel::Size::total_size($self)/1024/1024;
    }
    if (0) {
        eval "use Slic3r::Test::SectionCut";
        Slic3r::Test::SectionCut->new(print => $self)->export_svg("section_cut.svg");
    }
    
    # output everything to a G-code file
    my $output_file = $self->expanded_output_filepath($params{output_file});
    $status_cb->(90, "Exporting G-code" . ($output_file ? " to $output_file" : ""));
    $self->write_gcode($params{output_fh} || $output_file);
    
    # run post-processing scripts
    if (@{$Slic3r::Config->post_process}) {
        $status_cb->(95, "Running post-processing scripts");
        $Slic3r::Config->setenv;
        for (@{$Slic3r::Config->post_process}) {
            Slic3r::debugf "  '%s' '%s'\n", $_, $output_file;
            system($_, $output_file);
        }
    }
    
    # output some statistics
    unless ($params{quiet}) {
        $self->processing_time(tv_interval($t0));
        printf "Done. Process took %d minutes and %.3f seconds\n", 
            int($self->processing_time/60),
            $self->processing_time - int($self->processing_time/60)*60;
        
        # TODO: more statistics!
        print map sprintf("Filament required: %.1fmm (%.1fcm3)\n",
            $_->absolute_E, $_->extruded_volume/1000),
            @{$self->extruders};
    }
}

sub export_svg {
    my $self = shift;
    my %params = @_;
    
    # this shouldn't be needed, but we're currently relying on ->make_surfaces() which
    # calls ->perimeter_flow
    $self->init_extruders;
    
    $_->slice for @{$self->objects};
    
    my $fh = $params{output_fh};
    if (!$fh) {
        my $output_file = $self->expanded_output_filepath($params{output_file});
        $output_file =~ s/\.gcode$/.svg/i;
        Slic3r::open(\$fh, ">", $output_file) or die "Failed to open $output_file for writing\n";
        print "Exporting to $output_file..." unless $params{quiet};
    }
    
    my $print_size = $self->size;
    print $fh sprintf <<"EOF", unscale($print_size->[X]), unscale($print_size->[Y]);
<?xml version="1.0" encoding="UTF-8" standalone="yes"?>
<!DOCTYPE svg PUBLIC "-//W3C//DTD SVG 1.0//EN" "http://www.w3.org/TR/2001/REC-SVG-20010904/DTD/svg10.dtd">
<svg width="%s" height="%s" xmlns="http://www.w3.org/2000/svg" xmlns:svg="http://www.w3.org/2000/svg" xmlns:xlink="http://www.w3.org/1999/xlink" xmlns:slic3r="http://slic3r.org/namespaces/slic3r">
  <!-- 
  Generated using Slic3r $Slic3r::VERSION
  http://slic3r.org/
   -->
EOF
    
    my $print_polygon = sub {
        my ($polygon, $type) = @_;
        printf $fh qq{    <polygon slic3r:type="%s" points="%s" style="fill: %s" />\n},
            $type, (join ' ', map { join ',', map unscale $_, @$_ } @$polygon),
            ($type eq 'contour' ? 'white' : 'black');
    };
    
    my @layers = sort { $a->print_z <=> $b->print_z }
        map { @{$_->layers}, @{$_->support_layers} }
        @{$self->objects};
    
    my $layer_id = -1;
    my @previous_layer_slices = ();
    for my $layer (@layers) {
        $layer_id++;
        # TODO: remove slic3r:z for raft layers
        printf $fh qq{  <g id="layer%d" slic3r:z="%s">\n}, $layer_id, unscale($layer->slice_z);
        
        my @current_layer_slices = ();
        # sort slices so that the outermost ones come first
        my @slices = sort { $a->contour->encloses_point($b->contour->[0]) ? 0 : 1 } @{$layer->slices};
        foreach my $copy (@{$layer->object->copies}) {
            foreach my $slice (@slices) {
                my $expolygon = $slice->clone;
                $expolygon->translate(@$copy);
                $print_polygon->($expolygon->contour, 'contour');
                $print_polygon->($_, 'hole') for @{$expolygon->holes};
                push @current_layer_slices, $expolygon;
            }
        }
        # generate support material
        if ($self->has_support_material && $layer->id > 0) {
            my (@supported_slices, @unsupported_slices) = ();
            foreach my $expolygon (@current_layer_slices) {
                my $intersection = intersection_ex(
                    [ map @$_, @previous_layer_slices ],
                    $expolygon,
                );
                @$intersection
                    ? push @supported_slices, $expolygon
                    : push @unsupported_slices, $expolygon;
            }
            my @supported_points = map @$_, @$_, @supported_slices;
            foreach my $expolygon (@unsupported_slices) {
                # look for the nearest point to this island among all
                # supported points
                my $contour = $expolygon->contour;
                my $support_point = $contour->first_point->nearest_point(\@supported_points)
                    or next;
                my $anchor_point = $support_point->nearest_point([ @$contour ]);
                printf $fh qq{    <line x1="%s" y1="%s" x2="%s" y2="%s" style="stroke-width: 2; stroke: white" />\n},
                    map @$_, $support_point, $anchor_point;
            }
        }
        print $fh qq{  </g>\n};
        @previous_layer_slices = @current_layer_slices;
    }
    
    print $fh "</svg>\n";
    close $fh;
    print "Done.\n" unless $params{quiet};
}

sub make_skirt {
    my $self = shift;
    return unless $Slic3r::Config->skirts > 0
        || ($Slic3r::Config->ooze_prevention && @{$self->extruders} > 1);
    
    # collect points from all layers contained in skirt height
    my @points = ();
    foreach my $obj_idx (0 .. $#{$self->objects}) {
        my $object = $self->objects->[$obj_idx];
        my @layers = map $object->layers->[$_], 0..min($Slic3r::Config->skirt_height-1, $#{$object->layers});
        my @layer_points = (
            (map @$_, map @$_, map @{$_->slices}, @layers),
        );
        if (@{ $object->support_layers }) {
            my @support_layers = map $object->support_layers->[$_], 0..min($Slic3r::Config->skirt_height-1, $#{$object->support_layers});
            push @layer_points,
                (map @{$_->polyline}, map @{$_->support_fills}, grep $_->support_fills, @support_layers),
                (map @{$_->polyline}, map @{$_->support_interface_fills}, grep $_->support_interface_fills, @support_layers);
        }
        push @points, map move_points($_, @layer_points), @{$object->copies};
    }
    return if @points < 3;  # at least three points required for a convex hull
    
    # find out convex hull
    my $convex_hull = convex_hull([ map $_->arrayref, @points ]);
    
    my @extruded_length = ();  # for each extruder
    
    # TODO: use each extruder's own flow
    my $spacing = $self->objects->[0]->layers->[0]->regions->[0]->perimeter_flow->spacing;
    
    my $first_layer_height = $Slic3r::Config->get_value('first_layer_height');
    my @extruders_e_per_mm = ();
    my $extruder_idx = 0;
    
    # draw outlines from outside to inside
    # loop while we have less skirts than required or any extruder hasn't reached the min length if any
    my $distance = scale $Slic3r::Config->skirt_distance;
    for (my $i = $Slic3r::Config->skirts; $i > 0; $i--) {
        $distance += scale $spacing;
        my $loop = Slic3r::Geometry::Clipper::offset([$convex_hull], $distance, 0.0001, JT_ROUND)->[0];
        $self->skirt->append(Slic3r::ExtrusionLoop->new(
            polygon         => Slic3r::Polygon->new(@$loop),
            role            => EXTR_ROLE_SKIRT,
            flow_spacing    => $spacing,
        ));
        
        if ($Slic3r::Config->min_skirt_length > 0) {
            $extruded_length[$extruder_idx]     ||= 0;
            $extruders_e_per_mm[$extruder_idx]  ||= $self->extruders->[$extruder_idx]->e_per_mm($spacing, $first_layer_height);
            $extruded_length[$extruder_idx]     += unscale $loop->length * $extruders_e_per_mm[$extruder_idx];
            $i++ if defined first { ($extruded_length[$_] // 0) < $Slic3r::Config->min_skirt_length } 0 .. $#{$self->extruders};
            if ($extruded_length[$extruder_idx] >= $Slic3r::Config->min_skirt_length) {
                if ($extruder_idx < $#{$self->extruders}) {
                    $extruder_idx++;
                    next;
                }
            }
        }
    }
    
    $self->skirt->reverse;
}

sub make_brim {
    my $self = shift;
    return unless $Slic3r::Config->brim_width > 0;
    
    my $flow = $self->objects->[0]->layers->[0]->regions->[0]->perimeter_flow;
    
    my $grow_distance = $flow->scaled_width / 2;
    my @islands = (); # array of polygons
    foreach my $obj_idx (0 .. $#{$self->objects}) {
        my $object = $self->objects->[$obj_idx];
        my $layer0 = $object->layers->[0];
        my @object_islands = (
            (map $_->contour, @{$layer0->slices}),
        );
        if (@{ $object->support_layers }) {
            my $support_layer0 = $object->support_layers->[0];
            push @object_islands,
                (map $_->polyline->grow($grow_distance), @{$support_layer0->support_fills})
                if $support_layer0->support_fills;
            push @object_islands,
                (map $_->polyline->grow($grow_distance), @{$support_layer0->support_interface_fills})
                if $support_layer0->support_interface_fills;
        }
        foreach my $copy (@{$object->copies}) {
            push @islands, map { $_->translate(@$copy); $_ } map $_->clone, @object_islands;
        }
    }
    
    # if brim touches skirt, make it around skirt too
    # TODO: calculate actual skirt width (using each extruder's flow in multi-extruder setups)
    if ($Slic3r::Config->skirt_distance + (($Slic3r::Config->skirts - 1) * $flow->spacing) <= $Slic3r::Config->brim_width) {
        push @islands, map $_->split_at_first_point->polyline->grow($grow_distance), @{$self->skirt};
    }
    
    my @loops = ();
    my $num_loops = sprintf "%.0f", $Slic3r::Config->brim_width / $flow->width;
    for my $i (reverse 1 .. $num_loops) {
        # JT_SQUARE ensures no vertex is outside the given offset distance
        # -0.5 because islands are not represented by their centerlines
        # (first offset more, then step back - reverse order than the one used for 
        # perimeters because here we're offsetting outwards)
        push @loops, @{offset2(\@islands, ($i + 0.5) * $flow->scaled_spacing, -1.0 * $flow->scaled_spacing, 100000, JT_SQUARE)};
    }
    
    $self->brim->append(map Slic3r::ExtrusionLoop->new(
        polygon         => Slic3r::Polygon->new(@$_),
        role            => EXTR_ROLE_SKIRT,
        flow_spacing    => $flow->spacing,
    ), reverse traverse_pt( union_pt(\@loops) ));
}

sub write_gcode {
    my $self = shift;
    my ($file) = @_;
    
    # open output gcode file if we weren't supplied a file-handle
    my $fh;
    if (ref $file eq 'IO::Scalar') {
        $fh = $file;
    } else {
        Slic3r::open(\$fh, ">", $file)
            or die "Failed to open $file for writing\n";
    }
    
    # write some information
    my @lt = localtime;
    printf $fh "; generated by Slic3r $Slic3r::VERSION on %04d-%02d-%02d at %02d:%02d:%02d\n\n",
        $lt[5] + 1900, $lt[4]+1, $lt[3], $lt[2], $lt[1], $lt[0];

    print $fh "; $_\n" foreach split /\R/, $Slic3r::Config->notes;
    print $fh "\n" if $Slic3r::Config->notes;
    
    for (qw(layer_height perimeters top_solid_layers bottom_solid_layers fill_density perimeter_speed infill_speed travel_speed)) {
        printf $fh "; %s = %s\n", $_, $Slic3r::Config->$_;
    }
    for (qw(nozzle_diameter filament_diameter extrusion_multiplier)) {
        printf $fh "; %s = %s\n", $_, $Slic3r::Config->$_->[0];
    }
    printf $fh "; perimeters extrusion width = %.2fmm\n", $self->regions->[0]->flows->{perimeter}->width;
    printf $fh "; infill extrusion width = %.2fmm\n", $self->regions->[0]->flows->{infill}->width;
    printf $fh "; solid infill extrusion width = %.2fmm\n", $self->regions->[0]->flows->{solid_infill}->width;
    printf $fh "; top infill extrusion width = %.2fmm\n", $self->regions->[0]->flows->{top_infill}->width;
    printf $fh "; support material extrusion width = %.2fmm\n", $self->support_material_flow->width
        if $self->support_material_flow;
    printf $fh "; first layer extrusion width = %.2fmm\n", $self->regions->[0]->first_layer_flows->{perimeter}->width
        if $self->regions->[0]->first_layer_flows->{perimeter};
    print  $fh "\n";
    
    # set up our extruder object
    my $gcodegen = Slic3r::GCode->new(
        config              => $self->config,
        extra_variables     => $self->extra_variables,
        extruders           => $self->extruders,    # we should only pass the *used* extruders (but maintain the Tx indices right!)
        layer_count         => $self->layer_count,
    );
    print $fh "G21 ; set units to millimeters\n" if $Slic3r::Config->gcode_flavor ne 'makerware';
    print $fh $gcodegen->set_fan(0, 1) if $Slic3r::Config->cooling && $Slic3r::Config->disable_fan_first_layers;
    
    # set bed temperature
    if ((my $temp = $Slic3r::Config->first_layer_bed_temperature) && $Slic3r::Config->start_gcode !~ /M(?:190|140)/i) {
        printf $fh $gcodegen->set_bed_temperature($temp, 1);
    }
    
    # set extruder(s) temperature before and after start G-code
    my $print_first_layer_temperature = sub {
        my ($wait) = @_;
        
        return if $Slic3r::Config->start_gcode =~ /M(?:109|104)/i;
        for my $t (0 .. $#{$self->extruders}) {
            my $temp = $self->extruders->[$t]->first_layer_temperature;
            $temp += $self->config->standby_temperature_delta if $self->config->ooze_prevention;
            printf $fh $gcodegen->set_temperature($temp, $wait, $t) if $temp > 0;
        }
    };
    $print_first_layer_temperature->(0);
    printf $fh "%s\n", $gcodegen->replace_variables($Slic3r::Config->start_gcode);
    $print_first_layer_temperature->(1);
    
    # set other general things
    print  $fh "G90 ; use absolute coordinates\n" if $Slic3r::Config->gcode_flavor ne 'makerware';
    if ($Slic3r::Config->gcode_flavor =~ /^(?:reprap|teacup)$/) {
        printf $fh $gcodegen->reset_e;
        if ($Slic3r::Config->use_relative_e_distances) {
            print $fh "M83 ; use relative distances for extrusion\n";
        } else {
            print $fh "M82 ; use absolute distances for extrusion\n";
        }
    }
    
    # always start with first extruder
    # TODO: make sure we select the first *used* extruder
    print $fh $gcodegen->set_extruder($self->extruders->[0]);
    
    # calculate X,Y shift to center print around specified origin
    my $print_bb = $self->bounding_box;
    my $print_size = $print_bb->size;
    my @shift = (
        $Slic3r::Config->print_center->[X] - unscale($print_size->[X]/2 + $print_bb->x_min),
        $Slic3r::Config->print_center->[Y] - unscale($print_size->[Y]/2 + $print_bb->y_min),
    );
    
    # initialize a motion planner for object-to-object travel moves
    if ($Slic3r::Config->avoid_crossing_perimeters) {
        my $distance_from_objects = 1;
        # compute the offsetted convex hull for each object and repeat it for each copy.
        my @islands = ();
        foreach my $obj_idx (0 .. $#{$self->objects}) {
            my $convex_hull = convex_hull([
                map @{$_->contour->pp}, map @{$_->slices}, @{$self->objects->[$obj_idx]->layers},
            ]);
            # discard layers only containing thin walls (offset would fail on an empty polygon)
            if (@$convex_hull) {
                my $expolygon = Slic3r::ExPolygon->new($convex_hull);
                $expolygon->translate(scale $shift[X], scale $shift[Y]);
                my @island = @{$expolygon->offset_ex(scale $distance_from_objects, 1, JT_SQUARE)};
                foreach my $copy (@{ $self->objects->[$obj_idx]->copies }) {
                    push @islands, map { my $c = $_->clone; $c->translate(@$copy); $c } @island;
                }
            }
        }
        $gcodegen->external_mp(Slic3r::GCode::MotionPlanner->new(
            islands     => union_ex([ map @$_, @islands ]),
            internal    => 0,
        ));
    }
    
    # calculate wiping points if needed
    if ($self->config->ooze_prevention) {
        my $outer_skirt = Slic3r::Polygon->new(@{convex_hull([ map $_->pp, map @$_, @{$self->skirt} ])});
        my @skirts = ();
        foreach my $extruder (@{$self->extruders}) {
            push @skirts, my $s = $outer_skirt->clone;
            $s->translate(map scale($_), @{$extruder->extruder_offset});
        }
        my $convex_hull = Slic3r::Polygon->new(@{convex_hull([ map @$_, map $_->pp, @skirts ])});
        $gcodegen->standby_points([ map $_->clone, map @$_, map $_->subdivide(scale 10), @{offset([$convex_hull], scale 3)} ]);
    }
    
    # prepare the layer processor
    my $layer_gcode = Slic3r::GCode::Layer->new(
        print       => $self,
        gcodegen    => $gcodegen,
        shift       => \@shift,
    );
    
    # do all objects for each layer
    if ($Slic3r::Config->complete_objects) {
        
        # print objects from the smallest to the tallest to avoid collisions
        # when moving onto next object starting point
        my @obj_idx = sort { $self->objects->[$a]->size->[Z] <=> $self->objects->[$b]->size->[Z] } 0..$#{$self->objects};
        
        my $finished_objects = 0;
        for my $obj_idx (@obj_idx) {
            for my $copy (@{ $self->objects->[$obj_idx]->copies }) {
                # move to the origin position for the copy we're going to print.
                # this happens before Z goes down to layer 0 again, so that 
                # no collision happens hopefully.
                if ($finished_objects > 0) {
                    $gcodegen->set_shift(map $shift[$_] + unscale $copy->[$_], X,Y);
                    print $fh $gcodegen->retract;
                    print $fh $gcodegen->G0(Slic3r::Point->new(0,0), undef, 0, 'move to origin position for next object');
                }
                
                my $buffer = Slic3r::GCode::CoolingBuffer->new(
                    config      => $Slic3r::Config,
                    gcodegen    => $gcodegen,
                );
                
                my $object = $self->objects->[$obj_idx];
                my @layers = sort { $a->print_z <=> $b->print_z } @{$object->layers}, @{$object->support_layers};
                for my $layer (@layers) {
                    # if we are printing the bottom layer of an object, and we have already finished
                    # another one, set first layer temperatures. this happens before the Z move
                    # is triggered, so machine has more time to reach such temperatures
                    if ($layer->id == 0 && $finished_objects > 0) {
                        printf $fh $gcodegen->set_bed_temperature($Slic3r::Config->first_layer_bed_temperature),
                            if $Slic3r::Config->first_layer_bed_temperature;
                        $print_first_layer_temperature->();
                    }
                    print $fh $buffer->append(
                        $layer_gcode->process_layer($layer, [$copy]),
                        $layer->object."",
                        $layer->id,
                        $layer->print_z,
                    );
                }
                print $fh $buffer->flush;
                $finished_objects++;
            }
        }
    } else {
        # order objects using a nearest neighbor search
        my @obj_idx = chained_path([ map Slic3r::Point->new(@{$_->copies->[0]}), @{$self->objects} ]);
        
        # sort layers by Z
        my %layers = ();  # print_z => [ [layers], [layers], [layers] ]  by obj_idx
        foreach my $obj_idx (0 .. $#{$self->objects}) {
            my $object = $self->objects->[$obj_idx];
            foreach my $layer (@{$object->layers}, @{$object->support_layers}) {
                $layers{ $layer->print_z } ||= [];
                $layers{ $layer->print_z }[$obj_idx] ||= [];
                push @{$layers{ $layer->print_z }[$obj_idx]}, $layer;
            }
        }
        
        my $buffer = Slic3r::GCode::CoolingBuffer->new(
            config      => $Slic3r::Config,
            gcodegen    => $gcodegen,
        );
        foreach my $print_z (sort { $a <=> $b } keys %layers) {
            foreach my $obj_idx (@obj_idx) {
                foreach my $layer (@{ $layers{$print_z}[$obj_idx] // [] }) {
                    print $fh $buffer->append(
                        $layer_gcode->process_layer($layer, $layer->object->copies),
                        $layer->object . ref($layer),  # differentiate $obj_id between normal layers and support layers
                        $layer->id,
                        $layer->print_z,
                    );
                }
            }
        }
        print $fh $buffer->flush;
    }
    
    # write end commands to file
    print $fh $gcodegen->retract if $gcodegen->extruder;  # empty prints don't even set an extruder
    print $fh $gcodegen->set_fan(0);
    printf $fh "%s\n", $gcodegen->replace_variables($Slic3r::Config->end_gcode);
    
    foreach my $extruder (@{$self->extruders}) {
        printf $fh "; filament used = %.1fmm (%.1fcm3)\n",
            $extruder->absolute_E, $extruder->extruded_volume/1000;
    }
    
    if ($Slic3r::Config->gcode_comments) {
        # append full config
        print $fh "\n";
        foreach my $opt_key (sort keys %{$Slic3r::Config}) {
            next if $Slic3r::Config::Options->{$opt_key}{shortcut};
            next if $Slic3r::Config::Options->{$opt_key}{gui_only};
            printf $fh "; %s = %s\n", $opt_key, $Slic3r::Config->serialize($opt_key);
        }
    }
    
    # close our gcode file
    close $fh;
}

# this method will return the supplied input file path after expanding its
# format variables with their values
sub expanded_output_filepath {
    my $self = shift;
    my ($path, $input_file) = @_;
    
    my $extra_variables = {};
    if ($input_file) {
        @$extra_variables{qw(input_filename input_filename_base)} = parse_filename($input_file);
    } else {
        # if no input file was supplied, take the first one from our objects
        $input_file = $self->objects->[0]->input_file // return undef;
    }
    
    if ($path && -d $path) {
        # if output path is an existing directory, we take that and append
        # the specified filename format
        $path = File::Spec->join($path, $self->config->output_filename_format);
    } elsif (!$path) {
        # if no explicit output file was defined, we take the input
        # file directory and append the specified filename format
        $path = (fileparse($input_file))[1] . $self->config->output_filename_format;
    } else {
        # path is a full path to a file so we use it as it is
    }
    
    return $self->config->replace_options($path, { %{$self->extra_variables}, %$extra_variables });
}

# given the path to a file, this function returns its filename with and without extension
sub parse_filename {
    my ($path) = @_;
    
    my $filename = my $filename_base = basename($path);
    $filename_base =~ s/\.[^.]+$//;
    return ($filename, $filename_base);
}

1;