Index: source/tools/entity/.flake8
===================================================================
--- /dev/null
+++ source/tools/entity/.flake8
@@ -0,0 +1,2 @@
+[flake8]
+max-line-length = 150
Index: source/tools/entity/checkrefs.pl
===================================================================
--- source/tools/entity/checkrefs.pl
+++ /dev/null
@@ -1,704 +0,0 @@
-use strict;
-use warnings;
-use Data::Dumper;
-use File::Find;
-use XML::Simple;
-use JSON;
-use Getopt::Long qw(GetOptions);
-
-use lib ".";
-use Entity;
-
-GetOptions (
-    '--check-unused' => \(my $checkUnused = 0),
-    '--check-map-xml' => \(my $checkMapXml = 0),
-    '--validate-templates' => \(my $validateTemplates = 0),
-    '--mod-to-check=s' => \(my $modToCheck = "public")
-);
-
-my @files;
-my @roots;
-my @deps;
-
-# Force and checkMapXml if checkUnused is enabled to avoid false positives.
-$checkMapXml |= $checkUnused;
-my $vfsroot = '../../../binaries/data/mods';
-my $supportedTextureFormats = 'dds|png';
-my $mods = get_mod_dependencies_string($modToCheck);
-my $mod_list_string = $modToCheck;
-if ($mods ne "")
-{
-   $mod_list_string =  $mod_list_string."|$mods";
-}
-$mod_list_string =  $mod_list_string."|mod";
-print("Checking $modToCheck\'s integrity. \n");
-print("The following mod(s) will be loaded: $mod_list_string. \n");
-my @mods_list = split(/\|/, "$mod_list_string");
-
-sub get_mod_dependencies
-{
-    my ($mod) = @_;
-    my $modjson = parse_json_file_full_path("$vfsroot/$mod/mod.json");
-    my $modjsondeps = $modjson->{'dependencies'};
-    for my $dep (@{$modjsondeps})
-    {
-        # 0ad's folder isn't named like the mod.
-        if(index($dep, "0ad") != -1)
-        {
-            $dep = "public";
-        }
-    }
-
-    return $modjsondeps;
-}
-
-sub get_mod_dependencies_string
-{
-    my ($mod) = @_;
-    return join( '|',@{get_mod_dependencies($mod)});
-}
-
-sub vfs_to_physical
-{
-    my ($vfsPath) = @_;
-    my $fn = vfs_to_relative_to_mods($vfsPath);
-    return "$vfsroot/$fn";
-}
-
-sub vfs_to_relative_to_mods
-{
-    my ($vfsPath) = @_;
-
-    for my $dep (@mods_list)
-    {
-        my $fn = "$dep/$vfsPath";
-
-        if (-e "$vfsroot/$fn")
-        {
-            return $fn;
-        }
-    }
-}
-
-sub find_files
-{
-    my ($vfsPath, $extn) = @_;
-    my @files;
-    my $find_process = sub {
-        return $File::Find::prune = 1 if $_ eq '.svn';
-        my $n = $File::Find::name;
-        return if /~$/;
-        return unless -f $_;
-        return unless /\.($extn)$/;
-        $n =~ s~\Q$vfsroot\E/($mod_list_string)/~~;
-        push @files, $n;
-    };
-
-    for my $dep (@mods_list)
-    {
-        find({ wanted => $find_process },"$vfsroot/$dep/$vfsPath") if -d "$vfsroot/$dep/$vfsPath";
-    }
-
-    return @files;
-}
-
-sub parse_json_file_full_path
-{
-    my ($vfspath) = @_;
-    open my $fh, $vfspath or die "Failed to open '$vfspath': $!";
-    # decode_json expects a UTF-8 string and doesn't handle BOMs, so we strip those
-    # (see http://trac.wildfiregames.com/ticket/1556)
-    return decode_json(do { local $/; my $file = <$fh>; $file =~ s/^\xEF\xBB\xBF//; $file });
-}
-
-sub parse_json_file
-{
-    my ($vfspath) = @_;
-    return parse_json_file_full_path(vfs_to_physical($vfspath))
-}
-
-sub add_entities
-{
-    print "Loading entities...\n";
-
-    my @entfiles = find_files('simulation/templates', 'xml');
-    s~^simulation/templates/(.*)\.xml$~$1~ for @entfiles;
-
-    for my $f (sort @entfiles)
-    {
-        my $path = "simulation/templates/$f.xml";
-        push @files, $path;
-        my $ent = Entity::load_inherited($f, "$mod_list_string");
-
-        push @deps, [ $path, "simulation/templates/" . $ent->{Entity}{'@parent'}{' content'} . ".xml" ] if $ent->{Entity}{'@parent'};
-
-        if ($f !~ /^template_/)
-        {
-            push @roots, $path;
-            if ($ent->{Entity}{VisualActor} and $ent->{Entity}{VisualActor}{Actor})
-            {
-                my $phenotypes = $ent->{Entity}{Identity}{Phenotype}{' content'} || "default";
-                my @phenotypes = split /\s/,$phenotypes;
-
-                for my $phenotype (@phenotypes)
-                {
-                    # See simulation2/components/CCmpVisualActor.cpp and Identity.js for explanation.
-                    my $actorPath = $ent->{Entity}{VisualActor}{Actor}{' content'};
-                    $actorPath =~ s/{phenotype}/$phenotype/g;
-                    push @deps, [ $path, "art/actors/" . $actorPath ];
-                }
-
-                push @deps, [ $path, "art/actors/" . $ent->{Entity}{VisualActor}{FoundationActor}{' content'} ] if $ent->{Entity}{VisualActor}{FoundationActor};
-            }
-
-            if ($ent->{Entity}{Sound})
-            {
-                my $phenotypes = $ent->{Entity}{Identity}{Phenotype}{' content'} || "default";
-                my $lang = $ent->{Entity}{Identity}{Lang}{' content'} || "greek";
-
-                my @phenotypes = split /\s/,$phenotypes;
-
-                for my $phenotype (@phenotypes)
-                {
-                    for (grep ref($_), values %{$ent->{Entity}{Sound}{SoundGroups}})
-                    {
-                        # see simulation/components/Sound.js and Identity.js for explanation
-                        my $soundPath = $_->{' content'};
-                        $soundPath =~ s/{phenotype}/$phenotype/g;
-                        $soundPath =~ s/{lang}/$lang/g;
-                        push @deps, [ $path, "audio/" . $soundPath ];
-                    }
-                }
-            }
-
-            if ($ent->{Entity}{Identity})
-            {
-                push @deps, [ $path, "art/textures/ui/session/portraits/" . $ent->{Entity}{Identity}{Icon}{' content'} ] if $ent->{Entity}{Identity}{Icon} and $ent->{Entity}{Identity}{Icon}{' content'} ne '';
-            }
-
-            if ($ent->{Entity}{Heal} and $ent->{Entity}{Heal}{RangeOverlay})
-            {
-                push @deps, [ $path, "art/textures/selection/" . $ent->{Entity}{Heal}{RangeOverlay}{LineTexture}{' content'} ] if $ent->{Entity}{Heal}{RangeOverlay}{LineTexture} and $ent->{Entity}{Heal}{RangeOverlay}{LineTexture}{' content'} ne '';
-                push @deps, [ $path, "art/textures/selection/" . $ent->{Entity}{Heal}{RangeOverlay}{LineTextureMask}{' content'} ] if $ent->{Entity}{Heal}{RangeOverlay}{LineTextureMask} and $ent->{Entity}{Heal}{RangeOverlay}{LineTextureMask}{' content'} ne '';
-            }
-
-            if ($ent->{Entity}{Selectable} and $ent->{Entity}{Selectable}{Overlay} and $ent->{Entity}{Selectable}{Overlay}{Texture})
-            {
-                push @deps, [ $path, "art/textures/selection/" . $ent->{Entity}{Selectable}{Overlay}{Texture}{MainTexture}{' content'} ] if $ent->{Entity}{Selectable}{Overlay}{Texture}{MainTexture} and $ent->{Entity}{Selectable}{Overlay}{Texture}{MainTexture}{' content'} ne '';
-                push @deps, [ $path, "art/textures/selection/" . $ent->{Entity}{Selectable}{Overlay}{Texture}{MainTextureMask}{' content'} ] if $ent->{Entity}{Selectable}{Overlay}{Texture}{MainTextureMask} and $ent->{Entity}{Selectable}{Overlay}{Texture}{MainTextureMask}{' content'} ne '';
-            }
-
-            if ($ent->{Entity}{Formation})
-            {
-                push @deps, [ $path, "art/textures/ui/session/icons/" . $ent->{Entity}{Formation}{Icon}{' content'} ] if $ent->{Entity}{Formation}{Icon} and $ent->{Entity}{Formation}{Icon}{' content'} ne '';
-            }
-        }
-    }
-}
-
-sub push_variant_dependencies
-{
-    my ($variant, $f) = @_;
-    push @deps, [ $f, "art/variants/$variant->{file}" ] if $variant->{file};
-    push @deps, [ $f, "art/meshes/$variant->{mesh}" ] if $variant->{mesh};
-    push @deps, [ $f, "art/particles/$variant->{particles}{file}" ] if $variant->{particles}{file};
-    for my $tex (@{$variant->{textures}{texture}})
-    {
-        push @deps, [ $f, "art/textures/skins/$tex->{file}" ] if $tex->{file};
-    }
-    for my $prop (@{$variant->{props}{prop}})
-    {
-        push @deps, [ $f, "art/actors/$prop->{actor}" ] if $prop->{actor};
-    }
-    for my $anim (@{$variant->{animations}{animation}})
-    {
-        push @deps, [ $f, "art/animation/$anim->{file}" ] if $anim->{file};
-    }
-}
-
-sub add_actors
-{
-    print "Loading actors...\n";
-
-    my @actorfiles = find_files('art/actors', 'xml');
-    for my $f (sort @actorfiles)
-    {
-        push @files, $f;
-        push @roots, $f;
-
-        my $actor = XMLin(vfs_to_physical($f), ForceArray => [qw(group variant texture prop animation)], KeyAttr => []) or die "Failed to parse '$f': $!";
-
-        for my $group (@{$actor->{group}})
-        {
-            for my $variant (@{$group->{variant}})
-            {
-                push_variant_dependencies($variant, $f);
-            }
-        }
-
-        push @deps, [ $f, "art/materials/$actor->{material}" ] if $actor->{material};
-    }
-}
-
-
-sub add_variants
-{
-    print "Loading variants...\n";
-    my @variantfiles = find_files('art/variants', 'xml');
-
-    for my $f (sort @variantfiles)
-    {
-        push @files, $f;
-        push @roots, $f;
-        my $variant = XMLin(vfs_to_physical($f), ForceArray => [qw(texture prop animation)], KeyAttr => []) or die "Failed to parse '$f': $!";
-        push_variant_dependencies($variant, $f);
-    }
-}
-
-sub add_art
-{
-    print "Loading art files...\n";
-    push @files, find_files('art/textures/particles', $supportedTextureFormats);
-    push @files, find_files('art/textures/terrain', $supportedTextureFormats);
-    push @files, find_files('art/textures/skins', $supportedTextureFormats);
-    push @files, find_files('art/meshes', 'pmd|dae');
-    push @files, find_files('art/animation', 'psa|dae');
-}
-
-sub add_materials
-{
-    print "Loading materials...\n";
-    my @materialfiles = find_files('art/materials', 'xml');
-    for my $f (sort @materialfiles)
-    {
-        push @files, $f;
-
-        my $material = XMLin(vfs_to_physical($f), ForceArray => [qw(alternative)], KeyAttr => []);
-        for my $alternative (@{$material->{alternative}})
-        {
-            push @deps, [ $f, "art/materials/$alternative->{material}" ] if $alternative->{material};
-        }
-    }
-}
-
-sub add_particles
-{
-    print "Loading particles...\n";
-    my @particlefiles = find_files('art/particles', 'xml');
-    for my $f (sort @particlefiles)
-    {
-        push @files, $f;
-
-        my $particle = XMLin(vfs_to_physical($f));
-        push @deps, [ $f, "$particle->{texture}" ] if $particle->{texture};
-    }
-}
-
-sub add_maps_xml
-{
-    print "Loading maps XML...\n";
-    my @mapfiles = find_files('maps/scenarios', 'xml');
-    push @mapfiles, find_files('maps/skirmishes', 'xml');
-    push @mapfiles, find_files('maps/tutorials', 'xml');
-    for my $f (sort @mapfiles)
-    {
-        push @files, $f;
-        push @roots, $f;
-
-        my $map = XMLin(vfs_to_physical($f), ForceArray => [qw(Entity)], KeyAttr => []) or die "Failed to parse '$f': $!";
-
-        my %used;
-        for my $entity (@{$map->{Entities}{Entity}})
-        {
-            $used{$entity->{Template}} = 1;
-        }
-
-        for my $template (keys %used)
-        {
-            if ($template =~ /^actor\|(.*)$/)
-            {
-                # Handle special 'actor|' case
-                push @deps, [ $f, "art/actors/$1" ];
-            }
-            else
-            {
-                if ($template =~ /^resource\|(.*)$/)
-                {
-                    # Handle special 'resource|' case
-                    $template = $1;
-                }
-                push @deps, [ $f, "simulation/templates/$template.xml" ];
-            }
-        }
-
-        # Map previews
-        my $settings = decode_json($map->{ScriptSettings});
-        push @deps, [ $f, "art/textures/ui/session/icons/mappreview/" . $settings->{Preview} ] if $settings->{Preview};
-    }
-}
-
-sub add_maps_pmp
-{
-    print "Loading maps PMP...\n";
-
-    # Need to generate terrain texture filename=>path lookup first
-    my %terrains;
-    for my $f (find_files('art/terrains', 'xml'))
-    {
-        $f =~ /([^\/]+)\.xml/ or die;
-
-        # ignore terrains.xml
-        if ($f !~ /terrains.xml$/)
-        {
-            warn "Duplicate terrain name '$1' (from '$terrains{$1}' and '$f')\n" if $terrains{$1};
-            $terrains{$1} = $f;
-        }
-    }
-
-    my @mapfiles = find_files('maps/scenarios', 'pmp');
-    push @mapfiles, find_files('maps/skirmishes', 'pmp');
-    for my $f (sort @mapfiles)
-    {
-        push @files, $f;
-
-        push @roots, $f;
-
-        open my $fh, vfs_to_physical($f) or die "Failed to open '$f': $!";
-        binmode $fh;
-
-        my $buf;
-
-        read $fh, $buf, 4;
-        die "Invalid PMP header ($buf) in '$f'" unless $buf eq "PSMP";
-
-        read $fh, $buf, 4;
-        my $version = unpack 'V', $buf;
-        die "Invalid PMP version ($version) in '$f'" unless $version == 6;
-
-        read $fh, $buf, 4;
-        my $datasize = unpack 'V', $buf;
-
-        read $fh, $buf, 4;
-        my $mapsize = unpack 'V', $buf;
-
-        seek $fh, 2 * ($mapsize*16+1)*($mapsize*16+1), 1; # heightmap
-
-        read $fh, $buf, 4;
-        my $numtexs = unpack 'V', $buf;
-
-        for (0..$numtexs-1)
-        {
-            read $fh, $buf, 4;
-            my $len = unpack 'V', $buf;
-            my $str;
-            read $fh, $str, $len;
-
-            push @deps, [ $f, $terrains{$str} || "art/terrains/(unknown)/$str" ];
-        }
-
-        # ignore patches data
-    }
-}
-
-sub add_soundgroups
-{
-    print "Loading sound groups...\n";
-    my @soundfiles = find_files('audio', 'xml');
-    for my $f (sort @soundfiles)
-    {
-        push @files, $f;
-        push @roots, $f;
-
-        my $sound = XMLin(vfs_to_physical($f), ForceArray => [qw(Sound)], KeyAttr => []) or die "Failed to parse '$f': $!";
-
-        my $path = $sound->{Path};
-        $path =~ s/\/$//; # strip optional trailing slash
-
-        for (@{$sound->{Sound}})
-        {
-            push @deps, [$f, "$path/$_" ];
-        }
-    }
-}
-
-sub add_audio
-{
-    print "Loading audio files...\n";
-    push @files, find_files('audio', 'ogg');
-}
-
-sub add_gui_xml
-{
-    print "Loading GUI XML...\n";
-    my @guifiles = find_files('gui', 'xml');
-    for my $f (sort @guifiles)
-    {
-        push @files, $f;
-
-        if ($f =~ /^gui\/page_/)
-        {
-            push @roots, $f;
-            my $xml = XMLin(vfs_to_physical($f), ForceArray => [qw(include)], KeyAttr => []) or die "Failed to parse '$f': $!";
-
-            for my $include (@{$xml->{include}})
-            {
-                # If including an entire directory, find all the *.xml files
-                if ($include =~ /\/$/)
-                {
-                    push @deps, [ $f, $_ ] for find_files("gui/$include", 'xml');
-                }
-                else
-                {
-                    push @deps, [ $f, "gui/$include" ];
-                }
-            }
-        }
-        else
-        {
-            my $xml = XMLin(vfs_to_physical($f), ForceArray => [qw(object script action sprite image)], KeyAttr => [], KeepRoot => 1) or die "Failed to parse '$f': $!";
-            my $name = (keys %$xml)[0];
-            if ($name eq 'objects' or $name eq 'object')
-            {
-                for (grep ref $_ , @{$xml->{objects}{script}})
-                {
-                    push @deps, [ $f, $_->{file} ] if $_->{file};
-                    if ($_->{directory})
-                    {
-                        # If including an entire directory, find all the *.js files
-                        push @deps, [ $f, $_ ] for find_files($_->{directory}, 'js')
-                    }
-                }
-                my $add_objects;
-                $add_objects = sub
-                {
-                    my ($parent) = @_;
-                    for my $obj (@{$parent->{object}})
-                    {
-                        # TODO: look at sprites, styles, etc
-                        $add_objects->($obj);
-                    }
-                };
-                $add_objects->($xml->{objects});
-            }
-            elsif ($name eq 'setup')
-            {
-                # TODO: look at sprites, styles, etc
-            }
-            elsif ($name eq 'styles')
-            {
-                # TODO: look at sprites, styles, etc
-            }
-            elsif ($name eq 'sprites')
-            {
-                for my $sprite (@{$xml->{sprites}{sprite}})
-                {
-                    for my $image (@{$sprite->{image}})
-                    {
-                        push @deps, [ $f, "art/textures/ui/$image->{texture}" ] if $image->{texture};
-                    }
-                }
-            }
-            else
-            {
-                print "Unexpected GUI XML root element '$name':\n" . Dumper $xml;
-                exit;
-            }
-        }
-    }
-}
-
-sub add_gui_data
-{
-    print "Loading GUI data...\n";
-    push @files, find_files('gui', 'js');
-    push @files, find_files('art/textures/ui', $supportedTextureFormats);
-    push @files, find_files('art/textures/selection', $supportedTextureFormats);
-}
-
-sub add_civs
-{
-    print "Loading civs...\n";
-
-    my @civfiles = find_files('simulation/data/civs', 'json');
-    for my $f (sort @civfiles)
-    {
-        push @files, $f;
-
-        push @roots, $f;
-
-        my $civ = parse_json_file($f);
-
-        push @deps, [ $f, "art/textures/ui/" . $civ->{Emblem} ] if $civ->{Emblem};
-
-        push @deps, [ $f, "audio/music/" . $_->{File} ] for @{$civ->{Music}};
-    }
-}
-
-sub add_rms
-{
-    print "Loading random maps...\n";
-
-    push @files, find_files('maps/random', 'js');
-    my @rmsdefs = find_files('maps/random', 'json');
-
-    for my $f (sort @rmsdefs)
-    {
-        next if $f =~ /^maps\/random\/rmbiome/;
-
-        push @files, $f;
-
-        push @roots, $f;
-
-        my $rms = parse_json_file($f);
-        push @deps, [ $f, "maps/random/" . $rms->{settings}{Script} ]   if $rms->{settings}{Script};
-
-        # Map previews
-        push @deps, [ $f, "art/textures/ui/session/icons/mappreview/" . $rms->{settings}{Preview} ] if $rms->{settings}{Preview};
-    }
-}
-
-sub add_techs
-{
-    print "Loading techs...\n";
-
-    my @techfiles = find_files('simulation/data/technologies', 'json');
-    for my $f (sort @techfiles)
-    {
-        push @files, $f;
-        push @roots, $f;
-
-        my $tech = parse_json_file($f);
-
-        push @deps, [ $f, "art/textures/ui/session/portraits/technologies/" . $tech->{icon} ] if $tech->{icon};
-        push @deps, [ $f, "simulation/data/technologies/" . $tech->{supersedes} . ".json" ] if $tech->{supersedes};
-    }
-}
-
-sub add_auras
-{
-    print "Loading auras...\n";
-
-    my @aurafiles = find_files('simulation/data/auras', 'json');
-    for my $f (sort @aurafiles)
-    {
-        push @files, $f;
-        push @roots, $f;
-
-        my $aura = parse_json_file($f);
-
-        push @deps, [ $f, $aura->{overlayIcon} ] if $aura->{overlayIcon};
-
-        if($aura->{rangeOverlay})
-        {
-            push @deps, [ $f, "art/textures/selection/" . $aura->{rangeOverlay}{lineTexture} ] if $aura->{rangeOverlay}{lineTexture};
-            push @deps, [ $f, "art/textures/selection/" . $aura->{rangeOverlay}{lineTextureMask} ] if $aura->{rangeOverlay}{lineTextureMask};
-        }
-    }
-}
-
-sub add_terrains
-{
-    print "Loading terrains...\n";
-
-    my @terrains = find_files('art/terrains', 'xml');
-    for my $f (sort @terrains)
-    {
-        # ignore terrains.xml
-        if ($f !~ /terrains.xml$/)
-        {
-            push @files, $f;
-            push @roots, $f;
-
-            my $terrain = XMLin(vfs_to_physical($f), ForceArray => [qw(texture)], KeyAttr => []) or die "Failed to parse '$f': $!";
-
-            for my $texture (@{$terrain->{textures}{texture}})
-            {
-                push @deps, [ $f, "art/textures/terrain/$texture->{file}" ] if $texture->{file};
-            }
-            push @deps, [ $f, "art/materials/$terrain->{material}" ] if $terrain->{material};
-        }
-    }
-}
-
-
-sub check_deps
-{
-    my %files;
-    @files{@files} = ();
-
-    my %lcfiles;
-    @lcfiles{map lc($_), @files} = @files;
-
-    my %revdeps;
-    for my $d (@deps)
-    {
-        push @{$revdeps{$d->[1]}}, $d->[0];
-    }
-
-    for my $f (sort keys %revdeps)
-    {
-        next if exists $files{$f};
-        warn "Missing file '$f' referenced by: " . (join ', ', map "'$_'", map vfs_to_relative_to_mods($_), sort @{$revdeps{$f}}) . "\n";
-
-        if (exists $lcfiles{lc $f})
-        {
-            warn "### Case-insensitive match (found '$lcfiles{lc $f}')\n";
-        }
-    }
-}
-
-sub check_unused
-{
-    my %reachable;
-    @reachable{@roots} = ();
-
-    my %deps;
-    for my $d (@deps)
-    {
-        push @{$deps{$d->[0]}}, $d->[1];
-    }
-
-    while (1)
-    {
-        my @newreachable;
-        for my $r (keys %reachable)
-        {
-            push @newreachable, grep { not exists $reachable{$_} } @{$deps{$r}};
-        }
-        last if @newreachable == 0;
-        @reachable{@newreachable} = ();
-    }
-
-    for my $f (sort @files)
-    {
-        next if exists $reachable{$f}
-        || index($f, "art/terrains/") != -1
-        || index($f, "maps/random/") != -1
-        || index($f, "art/materials/") != -1;
-        warn "Unused file '" . vfs_to_relative_to_mods($f) . "'\n";
-    }
-}
-
-
-add_maps_xml() if $checkMapXml;
-add_maps_pmp();
-add_entities();
-add_actors();
-add_variants();
-add_art();
-add_materials();
-add_particles();
-add_soundgroups();
-add_audio();
-add_gui_xml();
-add_gui_data();
-add_civs();
-add_rms();
-add_techs();
-add_terrains();
-add_auras();
-
-check_deps();
-check_unused() if $checkUnused;
-print "\n" if $checkUnused;
-system("perl ../xmlvalidator/validate.pl") if $validateTemplates;
Index: source/tools/entity/checkrefs.py
===================================================================
--- /dev/null
+++ source/tools/entity/checkrefs.py
@@ -0,0 +1,573 @@
+#!/usr/bin/env python3
+from argparse import ArgumentParser
+from collections import Counter
+from decimal import Decimal
+from io import BytesIO
+from json import load, loads
+from pathlib import Path
+from re import split
+from struct import unpack, calcsize
+from subprocess import run
+from sys import stderr, exit
+from xml.etree import ElementTree
+
+
+def warn(s):
+    print(f"warn: {s}", file=stderr)
+
+
+class SimulTemplateEntity:
+    def __init__(self, vfs_root):
+        self.vfs_root = vfs_root
+
+    def get_file(self, vfs_path, mod):
+        return (self.vfs_root / mod / vfs_path).with_suffix('.xml')
+
+    def get_main_mod(self, vfs_path, mods):
+        for mod in mods:
+            fp = self.get_file(vfs_path, mod)
+            if fp.exists():
+                main_mod = mod
+                break
+        else:
+            # default to first mod
+            # it should then not exist
+            # it will raise an exception when trying to read it
+            main_mod = mods[0]
+        return main_mod
+
+    def apply_layer(self, base_tag, tag):
+        if tag.get('datatype') == 'tokens':
+            base_tokens = split(r'\s+', base_tag.text or '')
+            tokens = split(r'\s+', tag.text or '')
+            final_tokens = base_tokens.copy()
+            for token in tokens:
+                if token.startswith('-'):
+                    token_to_remove = token[1:]
+                    if token_to_remove in final_tokens:
+                        del final_tokens[token_to_remove]
+                elif token not in final_tokens:
+                    final_tokens.append(token)
+            base_tag.text = ' '.join(final_tokens)
+        elif tag.get('op'):
+            op = tag.get('op')
+            op1 = Decimal(base_tag.text or '0')
+            op2 = Decimal(tag.text or '0')
+            if op == 'add':
+                base_tag.text = str(op1 + op2)
+            elif op == 'mul':
+                base_tag.text = str(op1 * op2)
+            else:
+                raise ValueError(f"Invalid operator '{op}'")
+        else:
+            base_tag.text = tag.text
+        for child in tag:
+            base_child = base_tag.find(child.tag)
+            if 'disable' in child.attrib:
+                if base_child:
+                    base_tag.remove(base_child)
+            else:
+                if 'replace' in child.attrib and base_child:
+                    base_tag.remove(base_child)
+                if not base_child:
+                    base_child = ElementTree.Element(child.tag)
+                self.apply_layer(base_child, child)
+                if 'replace' in base_child.attrib:
+                    del base_child.attrib['replace']
+
+    def load_inherited(self, base_path, vfs_path, mods):
+        """
+        vfs_path should be relative to base_path in a mod
+        """
+        main_mod = self.get_main_mod(base_path / vfs_path, mods)
+        fp = self.get_file(base_path / vfs_path, main_mod)
+        layer = ElementTree.parse(fp).getroot()
+        for el in layer.iter():
+            children = [x.tag for x in el]
+            duplicates = [x for x, c in Counter(children).items() if c > 1]
+            if duplicates:
+                for dup in duplicates:
+                    warn(f"Duplicate child node '{dup}' in tag {el.tag} of {fp}")
+        if layer.get('parent'):
+            parent = self.load_inherited(base_path, layer.get('parent'), mods)
+            self.apply_layer(parent, layer)
+            return parent
+        else:
+            return layer
+
+
+class CheckRefs:
+    def __init__(self):
+        # list of relative root file:str
+        self.files = []
+        # list of relative file:str
+        self.roots = []
+        # list of tuple (parent_file:str, dep_file:str)
+        self.deps = []
+        self.vfs_root = Path(__file__).resolve().parents[3] / 'binaries' / 'data' / 'mods'
+        self.supportedTextureFormats = ('dds', 'png')
+        self.supportedMeshesFormats = ('pmd', 'dae')
+        self.supportedAnimationFormats = ('psa', 'dae')
+        self.mods = []
+
+    def main(self):
+        ap = ArgumentParser(description="Checks the game files for missing dependencies, unused files,"
+                            " and for file integrity.")
+        ap.add_argument('-u', '--check-unused', action='store_true',
+                        help="check for all the unused files in the given mods and their dependencies."
+                        " Implies --check-map-xml. Currently yields a lot of false positives.")
+        ap.add_argument('-x', '--check-map-xml', action='store_true',
+                        help="check maps for missing actor and templates.")
+        ap.add_argument('-t', '--validate-templates', action='store_true',
+                        help="run the validator.py script to check if the xml files match their (.rng) grammar file."
+                        " This currently only works for the public mod.")
+        ap.add_argument('-m', '--mod-to-check', metavar="MOD", dest='mods', nargs='+', default=['public'],
+                        help="specify which mods to check. Default to public.")
+        args = ap.parse_args()
+        # force check_map_xml if check_unused is used to avoid false positives.
+        args.check_map_xml |= args.check_unused
+        # ordered uniq mods (dict maintains ordered keys from python 3.6)
+        self.mods = list(dict.fromkeys([*args.mods, *self.get_mod_dependencies(*args.mods), 'mod']).keys())
+        print(f"Checking {'|'.join(args.mods)}'s integrity.")
+        print(f"The following mods will be loaded: {'|'.join(self.mods)}.")
+        if args.check_map_xml:
+            self.add_maps_xml()
+        self.add_maps_pmp()
+        self.add_entities()
+        self.add_actors()
+        self.add_variants()
+        self.add_art()
+        self.add_materials()
+        self.add_particles()
+        self.add_soundgroups()
+        self.add_audio()
+        self.add_gui_xml()
+        self.add_gui_data()
+        self.add_civs()
+        self.add_rms()
+        self.add_techs()
+        self.add_terrains()
+        self.add_auras()
+        # Do some checks based on file, roots, deps
+        self.check_deps()
+        if args.check_unused:
+            self.check_unused()
+            print('')
+        if args.validate_templates:
+            proc = run([str((Path(__file__).parent / '../xmlvalidator/validator.py').resolve())])
+            exit(proc.returncode)
+
+    def get_mod_dependencies(self, *mods):
+        modjsondeps = []
+        for mod in mods:
+            with open(self.vfs_root / mod / 'mod.json') as f:
+                modjson = load(f)
+            # 0ad's folder isn't named like the mod.
+            modjsondeps.extend(['public' if '0ad' in dep else dep for dep in modjson.get('dependencies', [])])
+        return modjsondeps
+
+    def vfs_to_relative_to_mods(self, vfs_path):
+        for dep in self.mods:
+            fn = Path(dep) / vfs_path
+            if (self.vfs_root / fn).exists():
+                return fn
+        return None
+
+    def vfs_to_physical(self, vfs_path):
+        fn = self.vfs_to_relative_to_mods(vfs_path)
+        return self.vfs_root / fn
+
+    def find_files(self, vfs_path, *ext_list):
+        """
+        returns a list of 2-size tuple with:
+            - Path relative to the mod base
+            - full Path
+        """
+        full_exts = ['.' + ext for ext in ext_list]
+
+        def find_recursive(dp, base):
+            """(relative Path, full Path) generator"""
+            if dp.is_dir():
+                if dp.name != '.svn' and not dp.name.endswith('~'):
+                    for fp in dp.iterdir():
+                        yield from find_recursive(fp, base)
+            elif dp.suffix in full_exts:
+                relative_file_path = dp.relative_to(base)
+                yield (relative_file_path, dp.resolve())
+        return [(rp, fp) for mod in self.mods for (rp, fp) in find_recursive(self.vfs_root / mod / vfs_path, self.vfs_root / mod)]
+
+    def add_maps_xml(self):
+        print("Loading maps XML...")
+        mapfiles = self.find_files('maps/scenarios', 'xml')
+        mapfiles.extend(self.find_files('maps/skirmishes', 'xml'))
+        mapfiles.extend(self.find_files('maps/tutorials', 'xml'))
+        actor_prefix = 'actor|'
+        resource_prefix = 'resource|'
+        for (fp, ffp) in sorted(mapfiles):
+            self.files.append(str(fp))
+            self.roots.append(str(fp))
+            et_map = ElementTree.parse(ffp).getroot()
+            entities = et_map.find('Entities')
+            used = {entity.find('Template').text.strip() for entity in entities.findall('Entity')} if entities else {}
+            for template in used:
+                if template.startswith(actor_prefix):
+                    self.deps.append((str(fp), f'art/actors/{template[len(actor_prefix):]}'))
+                elif template.startswith(resource_prefix):
+                    self.deps.append((str(fp), f'simulation/templates/{template[len(resource_prefix):]}.xml'))
+                else:
+                    self.deps.append((str(fp), f'simulation/templates/{template}.xml'))
+            # Map previews
+            settings = loads(et_map.find('ScriptSettings').text)
+            if settings.get('Preview', None):
+                self.deps.append((str(fp), f'art/textures/ui/session/icons/mappreview/{settings["Preview"]}'))
+
+    def add_maps_pmp(self):
+        print("Loading maps PMP...")
+        # Need to generate terrain texture filename=>relative path lookup first
+        terrains = dict()
+        for (fp, ffp) in self.find_files('art/terrains', 'xml'):
+            name = fp.stem
+            # ignore terrains.xml
+            if name != 'terrains':
+                if name in terrains:
+                    warn(f"Duplicate terrain name '{name}' (from '{terrains[name]}' and '{ffp}')")
+                terrains[name] = str(fp)
+        mapfiles = self.find_files('maps/scenarios', 'pmp')
+        mapfiles.extend(self.find_files('maps/skirmishes', 'pmp'))
+        for (fp, ffp) in sorted(mapfiles):
+            self.files.append(str(fp))
+            self.roots.append(str(fp))
+            with open(ffp, 'rb') as f:
+                expected_header = b'PSMP'
+                header = f.read(len(expected_header))
+                if header != expected_header:
+                    raise ValueError(f"Invalid PMP header {header} in '{ffp}'")
+                int_fmt = '<L'  # little endian long int
+                int_len = calcsize(int_fmt)
+                version, = unpack(int_fmt, f.read(int_len))
+                if version != 6:
+                    raise ValueError(f"Invalid PMP version ({version}) in '{ffp}'")
+                datasize, = unpack(int_fmt, f.read(int_len))
+                mapsize, = unpack(int_fmt, f.read(int_len))
+                f.seek(2 * (mapsize * 16 + 1) * (mapsize * 16 + 1), 1)  # skip heightmap
+                numtexs, = unpack(int_fmt, f.read(int_len))
+                for i in range(numtexs):
+                    length, = unpack(int_fmt, f.read(int_len))
+                    terrain_name = f.read(length).decode('ascii')  # suppose ascii encoding
+                    self.deps.append((str(fp), terrains.get(terrain_name, f'art/terrains/(unknown)/{terrain_name}')))
+
+    def add_entities(self):
+        print("Loading entities...")
+        simul_templates_path = Path('simulation/templates')
+        simul_template_entity = SimulTemplateEntity(self.vfs_root)
+        for (fp, ffp) in sorted(self.find_files(simul_templates_path, 'xml')):
+            self.files.append(str(fp))
+            entity = simul_template_entity.load_inherited(simul_templates_path, str(fp.relative_to(simul_templates_path)), self.mods)
+            if entity.get('parent'):
+                self.deps.append((str(fp), str(simul_templates_path / (entity.get('parent') + '.xml'))))
+            if not str(fp).startswith('template_'):
+                self.roots.append(str(fp))
+                if entity.find('VisualActor') and entity.find('VisualActor').find('Actor'):
+                    phenotype_tag = entity.find('Identity').find('Phenotype')
+                    phenotypes = split(r'\s', phenotype_tag.text if phenotype_tag and phenotype_tag.text else 'default')
+                    actor = entity.find('VisualActor').find('Actor')
+                    if '{phenotype}' in actor.text:
+                        for phenotype in phenotypes:
+                            # See simulation2/components/CCmpVisualActor.cpp and Identity.js for explanation.
+                            actor_path = actor.text.replace('{phenotype}', phenotype)
+                            self.deps.append((str(fp), f'art/actors/{actor_path}'))
+                    else:
+                        actor_path = actor.text
+                        self.deps.append((str(fp), f'art/actors/{actor_path}'))
+                    foundaction_actor = entity.find('VisualActor').find('FoundationActor')
+                    if foundaction_actor:
+                        self.deps.append((str(fp), f'art/actors/{foundaction_actor.text}'))
+                if entity.find('Sound'):
+                    phenotype_tag = entity.find('Identity').find('Phenotype')
+                    phenotypes = split(r'\s', phenotype_tag.text if phenotype_tag and phenotype_tag.text else 'default')
+                    lang_tag = entity.find('Identity').find('Lang')
+                    lang = lang_tag.text if lang_tag and lang_tag.text else 'greek'
+                    sound_groups = entity.find('Sound').find('SoundGroups')
+                    for sound_group in sound_groups:
+                        if sound_group.text and sound_group.text.strip():
+                            if '{phenotype}' in sound_group.text:
+                                for phenotype in phenotypes:
+                                    # see simulation/components/Sound.js and Identity.js for explanation
+                                    sound_path = sound_group.text.replace('{phenotype}', phenotype).replace('{lang}', lang)
+                                    self.deps.append((str(fp), f'audio/{sound_path}'))
+                            else:
+                                sound_path = sound_group.text.replace('{lang}', lang)
+                                self.deps.append((str(fp), f'audio/{sound_path}'))
+                if entity.find('Identity'):
+                    icon = entity.find('Identity').find('Icon')
+                    if icon and icon.text:
+                        self.deps.append((str(fp), f'art/textures/ui/session/portraits/{icon.text}'))
+                if entity.find('Heal') and entity.find('Heal').find('RangeOverlay'):
+                    range_overlay = entity.find('Heal').find('RangeOverlay')
+                    for tag in ('LineTexture', 'LineTextureMask'):
+                        elem = range_overlay.find(tag)
+                        if elem and elem.text:
+                            self.deps.append((str(fp), f'art/textures/selection/{elem.text}'))
+                if entity.find('Selectable') and entity.find('Selectable').find('Overlay') \
+                        and entity.find('Selectable').find('Overlay').find('Texture'):
+                    texture = entity.find('Selectable').find('Overlay').find('Texture')
+                    for tag in ('MainTexture', 'MainTextureMask'):
+                        elem = texture.find(tag)
+                        if elem and elem.text:
+                            self.deps.append((str(fp), f'art/textures/selection/{elem.text}'))
+                if entity.find('Formation'):
+                    icon = entity.find('Formation').find('Icon')
+                    if icon and icon.text:
+                        self.deps.append((str(fp), f'art/textures/ui/session/icons/{icon.text}'))
+
+    def append_variant_dependencies(self, variant, fp):
+        variant_file = variant.get('file')
+        mesh = variant.find('mesh')
+        particles = variant.find('particles')
+        texture_files = [tex.get('file') for tex in variant.find('textures').findall('texture')] if variant.find('textures') else []
+        prop_actors = [prop.get('actor') for prop in variant.find('props').findall('prop')] if variant.find('props') else []
+        animation_files = [anim.get('file') for anim in variant.find('animations').findall('animation')] if variant.find('animations') else []
+        if variant_file:
+            self.deps.append((str(fp), f'art/variants/{variant_file}'))
+        if mesh and mesh.text:
+            self.deps.append((str(fp), f'art/meshes/{mesh.text}'))
+        if particles and particles.get('file'):
+            self.deps.append((str(fp), f'art/particles/{particles.get("file")}'))
+        for texture_file in [x for x in texture_files if x]:
+            self.deps.append((str(fp), f'art/textures/skins/{texture_file}'))
+        for prop_actor in [x for x in prop_actors if x]:
+            self.deps.append((str(fp), f'art/actors/{prop_actor}'))
+        for animation_file in [x for x in animation_files if x]:
+            self.deps.append((str(fp), f'art/animation/{animation_file}'))
+
+    def add_actors(self):
+        print("Loading actors...")
+        for (fp, ffp) in sorted(self.find_files('art/actors', 'xml')):
+            self.files.append(str(fp))
+            self.roots.append(str(fp))
+            actor = ElementTree.parse(ffp).getroot()
+            for group in actor.findall('group'):
+                for variant in group.findall('variant'):
+                    self.append_variant_dependencies(variant, fp)
+            material = actor.find('material')
+            if material and material.text:
+                self.deps.append((str(fp), f'art/materials/{material.text}'))
+
+    def add_variants(self):
+        print("Loading variants...")
+        for (fp, ffp) in sorted(self.find_files('art/variants', 'xml')):
+            self.files.append(str(fp))
+            self.roots.append(str(fp))
+            variant = ElementTree.parse(ffp).getroot()
+            self.append_variant_dependencies(variant, fp)
+
+    def add_art(self):
+        print("Loading art files...")
+        self.files.extend([str(fp) for (fp, ffp) in self.find_files('art/textures/particles', *self.supportedTextureFormats)])
+        self.files.extend([str(fp) for (fp, ffp) in self.find_files('art/textures/terrain', *self.supportedTextureFormats)])
+        self.files.extend([str(fp) for (fp, ffp) in self.find_files('art/textures/skins', *self.supportedTextureFormats)])
+        self.files.extend([str(fp) for (fp, ffp) in self.find_files('art/meshes', *self.supportedMeshesFormats)])
+        self.files.extend([str(fp) for (fp, ffp) in self.find_files('art/animation', *self.supportedAnimationFormats)])
+
+    def add_materials(self):
+        print("Loading materials...")
+        for (fp, ffp) in sorted(self.find_files('art/materials', 'xml')):
+            self.files.append(str(fp))
+            material_elem = ElementTree.parse(ffp).getroot()
+            for alternative in material_elem.findall('alternative'):
+                material = alternative.get('material')
+                if material:
+                    self.deps.append((str(fp), f'art/materials/{material}'))
+
+    def add_particles(self):
+        print("Loading particles...")
+        for (fp, ffp) in sorted(self.find_files('art/particles', 'xml')):
+            self.files.append(str(fp))
+            particle = ElementTree.parse(ffp).getroot()
+            texture = particle.get('texture')
+            if texture:
+                self.deps.append((str(fp), texture))
+
+    def add_soundgroups(self):
+        print("Loading sound groups...")
+        for (fp, ffp) in sorted(self.find_files('audio', 'xml')):
+            self.files.append(str(fp))
+            self.roots.append(str(fp))
+            sound_group = ElementTree.parse(ffp).getroot()
+            path = sound_group.find('Path').text.rstrip('/')
+            for sound in sound_group.findall('sound'):
+                self.deps.append((str(fp), f'{path}/{sound.text}'))
+
+    def add_audio(self):
+        print("Loading audio files...")
+        self.files.extend([str(fp) for (fp, ffp) in self.find_files('audio', 'ogg')])
+
+    def add_gui_xml(self):
+        print("Loading GUI XML...")
+        for (fp, ffp) in sorted(self.find_files('gui', 'xml')):
+            self.files.append(str(fp))
+            if str(fp).startswith('gui/page_'):
+                self.roots.append(str(fp))
+                root_xml = ElementTree.parse(ffp).getroot()
+                for include in root_xml.findall('include'):
+                    # If including an entire directory, find all the *.xml files
+                    if include.text.endswith('/'):
+                        self.deps.extend([(str(fp), str(sub_fp)) for (sub_fp, sub_ffp) in self.find_files(f'gui/{include.text}', 'xml')])
+                    else:
+                        self.deps.append((str(fp), f'gui/{include.text}'))
+            else:
+                xml = ElementTree.parse(ffp)
+                root_xml = xml.getroot()
+                name = root_xml.tag
+                if name in ('objects', 'object'):
+                    for script in root_xml.findall('script'):
+                        if script.get('file'):
+                            self.deps.append((str(fp), script.get('file')))
+                        if script.get('directory'):
+                            # If including an entire directory, find all the *.js files
+                            self.deps.extend([(str(fp), str(sub_fp)) for (sub_fp, sub_ffp) in self.find_files(script.get('directory'), 'js')])
+                    if name == 'objects':
+                        def add_objects(parent):
+                            for obj in parent.findall('object'):
+                                # TODO: look at sprites, styles, etc
+                                add_objects(obj)
+                        add_objects(root_xml)
+                elif name == 'setup':
+                    # TODO: look at sprites, styles, etc
+                    pass
+                elif name == 'styles':
+                    # TODO: look at sprites, styles, etc
+                    pass
+                elif name == 'sprites':
+                    for sprite in root_xml.findall('sprite'):
+                        for image in sprite.findall('image'):
+                            if image.get('texture'):
+                                self.deps.append((str(fp), f"art/textures/ui/{image.get('texture')}"))
+                else:
+                    bio = BytesIO()
+                    xml.write(bio)
+                    bio.seek(0)
+                    raise ValueError(f"Unexpected GUI XML root element '{name}':\n{bio.read().decode('ascii')}")
+
+    def add_gui_data(self):
+        print("Loading GUI data...")
+        self.files.extend([str(fp) for (fp, ffp) in self.find_files('gui', 'js')])
+        self.files.extend([str(fp) for (fp, ffp) in self.find_files('art/textures/ui', *self.supportedTextureFormats)])
+        self.files.extend([str(fp) for (fp, ffp) in self.find_files('art/textures/selection', *self.supportedTextureFormats)])
+
+    def add_civs(self):
+        print("Loading civs...")
+        for (fp, ffp) in sorted(self.find_files('simulation/data/civs', 'json')):
+            self.files.append(str(fp))
+            self.roots.append(str(fp))
+            with open(ffp) as f:
+                civ = load(f)
+            if civ.get('Emblem', None):
+                self.deps.append((str(fp), f"art/textures/ui/{civ['Emblem']}"))
+            for music in civ.get('Music', []):
+                self.deps.append((str(fp), f"audio/music/{music['File']}"))
+
+    def add_rms(self):
+        print("Loading random maps...")
+        self.files.extend([str(fp) for (fp, ffp) in self.find_files('maps/random', 'js')])
+        for (fp, ffp) in sorted(self.find_files('maps/random', 'json')):
+            if str(fp).startswith('maps/random/rmbiome'):
+                continue
+            self.files.append(str(fp))
+            self.roots.append(str(fp))
+            with open(ffp) as f:
+                randmap = load(f)
+            settings = randmap.get('settings', {})
+            if settings.get('Script', None):
+                self.deps.append((str(fp), f"maps/random/{settings['Script']}"))
+            # Map previews
+            if settings.get('Preview', None):
+                self.deps.append((str(fp), f'art/textures/ui/session/icons/mappreview/{settings["Preview"]}'))
+
+    def add_techs(self):
+        print("Loading techs...")
+        for (fp, ffp) in sorted(self.find_files('simulation/data/technologies', 'json')):
+            self.files.append(str(fp))
+            self.roots.append(str(fp))
+            with open(ffp) as f:
+                tech = load(f)
+            if tech.get('icon', None):
+                self.deps.append((str(fp), f"art/textures/ui/session/portraits/technologies/{tech['icon']}"))
+            if tech.get('supersedes', None):
+                self.deps.append((str(fp), f"simulation/data/technologies/{tech['supersedes']}.json"))
+
+    def add_terrains(self):
+        print("Loading terrains...")
+        for (fp, ffp) in sorted(self.find_files('art/terrains', 'xml')):
+            # ignore terrains.xml
+            if str(fp).endswith('terrains.xml'):
+                continue
+            self.files.append(str(fp))
+            self.roots.append(str(fp))
+            terrain = ElementTree.parse(ffp).getroot()
+            for texture in terrain.find('textures').findall('texture'):
+                if texture.get('file'):
+                    self.deps.append((str(fp), f"art/textures/terrain/{texture.get('file')}"))
+            if terrain.find('material'):
+                material = terrain.find('material').text
+                self.deps.append((str(fp), f"art/materials/{material}"))
+
+    def add_auras(self):
+        print("Loading auras...")
+        for (fp, ffp) in sorted(self.find_files('simulation/data/auras', 'json')):
+            self.files.append(str(fp))
+            self.roots.append(str(fp))
+            with open(ffp) as f:
+                aura = load(f)
+            if aura.get('overlayIcon', None):
+                self.deps.append((str(fp), aura['overlayIcon']))
+            range_overlay = aura.get('rangeOverlay', {})
+            for prop in ('lineTexture', 'lineTextureMask'):
+                if range_overlay.get(prop, None):
+                    self.deps.append((str(fp), f"art/textures/selection/{range_overlay[prop]}"))
+
+    def check_deps(self):
+        uniq_files = set(self.files)
+        lower_case_files = {f.lower(): f for f in uniq_files}
+        reverse_deps = dict()
+        for parent, dep in self.deps:
+            if dep not in reverse_deps:
+                reverse_deps[dep] = {parent}
+            else:
+                reverse_deps[dep].add(parent)
+        for dep in sorted(reverse_deps.keys()):
+            if dep in uniq_files:
+                continue
+            warn(f"Missing file '{dep}' referenced by: {', '.join(sorted([str(self.vfs_to_relative_to_mods(ref)) for ref in reverse_deps[dep]]))}")
+            if dep.lower() in lower_case_files:
+                warn(f"### Case-insensitive match (found '{lower_case_files[dep.lower()]}')")
+
+    def check_unused(self):
+        reachable = list(set(self.roots))
+        deps = dict()
+        for parent, dep in self.deps:
+            if parent not in deps:
+                deps[parent] = {dep}
+            else:
+                deps[parent].add(dep)
+        while True:
+            new_reachable = []
+            for r in reachable:
+                new_reachable.extend([x for x in deps.get(r, {}) if x not in reachable])
+            if new_reachable:
+                reachable.extend(new_reachable)
+            else:
+                break
+        for f in sorted(self.files):
+            if any((
+                f in reachable,
+                'art/terrains' in f,
+                'maps/random' in f,
+                'art/materials' in f,
+            )):
+                continue
+            warn(f"Unused file '{str(self.vfs_to_relative_to_mods(f))}'")
+
+
+if __name__ == '__main__':
+    CheckRefs().main()
Index: source/tools/entity/readme.md
===================================================================
--- source/tools/entity/readme.md
+++ source/tools/entity/readme.md
@@ -1,4 +1,4 @@
-# Checkrefs.pl
+# Checkrefs.py
 
 ## Description
 
@@ -6,24 +6,28 @@
 
 ## Requirements
 
-- Perl interpreter installed
-- Dependencies:
-  - XML::Parser
-  - XML::Simple
-  - Getopt::Long
-  - File::Find
-  - Data::Dumper
-  - JSON
+- Python 3.6+ interpreter installed
 
 ## Usage
 
-- cd in source/tools/entity and run the script.
+- cd in `source/tools/entity` and run the script.
 
 ```
-Usage: perl checkrefs.pl [OPTION]...
-Checks the game files for missing dependencies, unused files, and for file integrity.
-      --check-unused         check for all the unused files in the given mods and their dependencies. Implies --check-map-xml. Currently yields a lot of false positives.
-      --check-map-xml        check maps for missing actor and templates.
-      --validate-templates   run the validate.pl script to check if the xml files match their (.rng) grammar file. This currently only works for the public mod.
-      --mod-to-check=mods    specify which mods to check. 'mods' should be a list of mods separated by '|'. Default value: 'public|mod'.
+usage: checkrefs.py [-h] [-u] [-x] [-t] [-m MOD [MOD ...]]
+
+Checks the game files for missing dependencies, unused files, and for file
+integrity.
+
+optional arguments:
+  -h, --help            show this help message and exit
+  -u, --check-unused    check for all the unused files in the given mods and
+                        their dependencies. Implies --check-map-xml. Currently
+                        yields a lot of false positives.
+  -x, --check-map-xml   check maps for missing actor and templates.
+  -t, --validate-templates
+                        run the validator.py script to check if the xml files
+                        match their (.rng) grammar file. This currently only
+                        works for the public mod.
+  -m MOD [MOD ...], --mod-to-check MOD [MOD ...]
+                        specify which mods to check. Default to public.
 ```
Index: source/tools/xmlvalidator/validator.py
===================================================================
--- source/tools/xmlvalidator/validator.py
+++ source/tools/xmlvalidator/validator.py
@@ -1,4 +1,4 @@
-#!/usr/bin/env python
+#!/usr/bin/env python3
 import argparse
 import os
 import re