#!/usr/bin/env perl

  # SPDX-License-Identifier: GPL-2.0-or-later

  use strict;

  # Copyright (c) 2017-2020 Mauro Carvalho Chehab <mchehab@kernel.org>

  #

  my $prefix = "./";
  $prefix = "$ENV{'srctree'}/" if ($ENV{'srctree'});
  
  my $conf = $prefix . "Documentation/conf.py";
  my $requirement_file = $prefix . "Documentation/sphinx/requirements.txt";

  my $virtenv_prefix = "sphinx_";

  #
  # Static vars
  #
  
  my %missing;
  my $system_release;
  my $need = 0;
  my $optional = 0;
  my $need_symlink = 0;
  my $need_sphinx = 0;

  my $need_pip = 0;

  my $need_virtualenv = 0;

  my $rec_sphinx_upgrade = 0;

  my $install = "";

  my $virtenv_dir = "";

  my $python_cmd = "";

  my $activate_cmd;

  my $min_version;

  my $cur_version;

  my $rec_version = "1.7.9";	# PDF won't build here
  my $min_pdf_version = "2.4.4";	# Min version where pdf builds

  my $latest_avail_ver;

  #
  # Command line arguments
  #
  
  my $pdf = 1;
  my $virtualenv = 1;

  my $version_check = 0;

  
  #
  # List of required texlive packages on Fedora and OpenSuse
  #
  
  my %texlive = (

  	'amsfonts.sty'       => 'texlive-amsfonts',
  	'amsmath.sty'        => 'texlive-amsmath',
  	'amssymb.sty'        => 'texlive-amsfonts',
  	'amsthm.sty'         => 'texlive-amscls',
  	'anyfontsize.sty'    => 'texlive-anyfontsize',
  	'atbegshi.sty'       => 'texlive-oberdiek',
  	'bm.sty'             => 'texlive-tools',
  	'capt-of.sty'        => 'texlive-capt-of',
  	'cmap.sty'           => 'texlive-cmap',
  	'ecrm1000.tfm'       => 'texlive-ec',
  	'eqparbox.sty'       => 'texlive-eqparbox',
  	'eu1enc.def'         => 'texlive-euenc',
  	'fancybox.sty'       => 'texlive-fancybox',
  	'fancyvrb.sty'       => 'texlive-fancyvrb',
  	'float.sty'          => 'texlive-float',
  	'fncychap.sty'       => 'texlive-fncychap',
  	'footnote.sty'       => 'texlive-mdwtools',
  	'framed.sty'         => 'texlive-framed',
  	'luatex85.sty'       => 'texlive-luatex85',
  	'multirow.sty'       => 'texlive-multirow',
  	'needspace.sty'      => 'texlive-needspace',
  	'palatino.sty'       => 'texlive-psnfss',
  	'parskip.sty'        => 'texlive-parskip',
  	'polyglossia.sty'    => 'texlive-polyglossia',
  	'tabulary.sty'       => 'texlive-tabulary',
  	'threeparttable.sty' => 'texlive-threeparttable',
  	'titlesec.sty'       => 'texlive-titlesec',
  	'ucs.sty'            => 'texlive-ucs',
  	'upquote.sty'        => 'texlive-upquote',
  	'wrapfig.sty'        => 'texlive-wrapfig',

  	'ctexhook.sty'       => 'texlive-ctex',

  );
  
  #
  # Subroutines that checks if a feature exists
  #
  
  sub check_missing(%)
  {
  	my %map = %{$_[0]};
  
  	foreach my $prog (sort keys %missing) {
  		my $is_optional = $missing{$prog};

  		# At least on some LTS distros like CentOS 7, texlive doesn't
  		# provide all packages we need. When such distros are
  		# detected, we have to disable PDF output.
  		#
  		# So, we need to ignore the packages that distros would
  		# need for LaTeX to work
  		if ($is_optional == 2 && !$pdf) {
  			$optional--;
  			next;
  		}

  		if ($is_optional) {
  			print "Warning: better to also install \"$prog\".
  ";
  		} else {
  			print "ERROR: please install \"$prog\", otherwise, build won't work.
  ";
  		}
  		if (defined($map{$prog})) {
  			$install .= " " . $map{$prog};
  		} else {
  			$install .= " " . $prog;
  		}
  	}
  
  	$install =~ s/^\s//;
  }
  
  sub add_package($$)
  {
  	my $package = shift;
  	my $is_optional = shift;
  
  	$missing{$package} = $is_optional;
  	if ($is_optional) {
  		$optional++;
  	} else {
  		$need++;
  	}
  }
  
  sub check_missing_file($$$)
  {

  	my $files = shift;

  	my $package = shift;
  	my $is_optional = shift;

  	for (@$files) {
  		return if(-e $_);
  	}

  
  	add_package($package, $is_optional);
  }
  
  sub findprog($)
  {
  	foreach(split(/:/, $ENV{PATH})) {
  		return "$_/$_[0]" if(-x "$_/$_[0]");
  	}
  }

  sub find_python_no_venv()
  {
  	my $prog = shift;
  
  	my $cur_dir = qx(pwd);
  	$cur_dir =~ s/\s+$//;
  
  	foreach my $dir (split(/:/, $ENV{PATH})) {
  		next if ($dir =~ m,($cur_dir)/sphinx,);
  		return "$dir/python3" if(-x "$dir/python3");
  	}
  	foreach my $dir (split(/:/, $ENV{PATH})) {
  		next if ($dir =~ m,($cur_dir)/sphinx,);
  		return "$dir/python" if(-x "$dir/python");
  	}
  	return "python";
  }

  sub check_program($$)
  {
  	my $prog = shift;
  	my $is_optional = shift;

  	return $prog if findprog($prog);

  
  	add_package($prog, $is_optional);
  }
  
  sub check_perl_module($$)
  {
  	my $prog = shift;
  	my $is_optional = shift;
  
  	my $err = system("perl -M$prog -e 1 2>/dev/null /dev/null");
  	return if ($err == 0);
  
  	add_package($prog, $is_optional);
  }
  
  sub check_python_module($$)
  {
  	my $prog = shift;
  	my $is_optional = shift;

  	return if (!$python_cmd);
  
  	my $err = system("$python_cmd -c 'import $prog' 2>/dev/null /dev/null");

  	return if ($err == 0);
  
  	add_package($prog, $is_optional);
  }
  
  sub check_rpm_missing($$)
  {
  	my @pkgs = @{$_[0]};
  	my $is_optional = $_[1];
  
  	foreach my $prog(@pkgs) {
  		my $err = system("rpm -q '$prog' 2>/dev/null >/dev/null");
  		add_package($prog, $is_optional) if ($err);
  	}
  }
  
  sub check_pacman_missing($$)
  {
  	my @pkgs = @{$_[0]};
  	my $is_optional = $_[1];
  
  	foreach my $prog(@pkgs) {
  		my $err = system("pacman -Q '$prog' 2>/dev/null >/dev/null");
  		add_package($prog, $is_optional) if ($err);
  	}
  }
  
  sub check_missing_tex($)
  {
  	my $is_optional = shift;
  	my $kpsewhich = findprog("kpsewhich");
  
  	foreach my $prog(keys %texlive) {
  		my $package = $texlive{$prog};
  		if (!$kpsewhich) {
  			add_package($package, $is_optional);
  			next;
  		}
  		my $file = qx($kpsewhich $prog);
  		add_package($package, $is_optional) if ($file =~ /^\s*$/);
  	}
  }

  sub get_sphinx_fname()

  {

  	my $fname = "sphinx-build";
  	return $fname if findprog($fname);

  	$fname = "sphinx-build-3";
  	if (findprog($fname)) {

  		$need_symlink = 1;

  		return $fname;

  	}

  	return "";
  }

  sub get_sphinx_version($)
  {
  	my $cmd = shift;
  	my $ver;
  
  	open IN, "$cmd --version 2>&1 |";
  	while (<IN>) {

  		if (m/^\s*sphinx-build\s+([\d\.]+)((\+\/[\da-f]+)|(b\d+))?$/) {

  			$ver=$1;
  			last;
  		}
  		# Sphinx 1.2.x uses a different format
  		if (m/^\s*Sphinx.*\s+([\d\.]+)$/) {
  			$ver=$1;
  			last;
  		}
  	}
  	close IN;
  	return $ver;
  }

  sub check_sphinx()
  {

  	my $default_version;

  
  	open IN, $conf or die "Can't open $conf";
  	while (<IN>) {
  		if (m/^\s*needs_sphinx\s*=\s*[\'\"]([\d\.]+)[\'\"]/) {
  			$min_version=$1;
  			last;
  		}
  	}
  	close IN;
  
  	die "Can't get needs_sphinx version from $conf" if (!$min_version);
  
  	open IN, $requirement_file or die "Can't open $requirement_file";
  	while (<IN>) {
  		if (m/^\s*Sphinx\s*==\s*([\d\.]+)$/) {

  			$default_version=$1;

  			last;
  		}
  	}
  	close IN;

  	die "Can't get default sphinx version from $requirement_file" if (!$default_version);

  	$virtenv_dir = $virtenv_prefix . $default_version;

  
  	my $sphinx = get_sphinx_fname();

  	if ($sphinx eq "") {
  		$need_sphinx = 1;
  		return;
  	}

  	$cur_version = get_sphinx_version($sphinx);
  	die ("$sphinx returned an error") if (!$cur_version);

  
  	die "$sphinx didn't return its version" if (!$cur_version);

  	if ($cur_version lt $min_version) {

  		printf "ERROR: Sphinx version is %s. It should be >= %s (recommended >= %s)
  ",

  		       $cur_version, $min_version, $default_version;

  		$need_sphinx = 1;
  		return;
  	}

  	return if ($cur_version lt $rec_version);

  
  	# On version check mode, just assume Sphinx has all mandatory deps
  	exit (0) if ($version_check);

  }
  
  #
  # Ancillary subroutines
  #
  
  sub catcheck($)
  {
    my $res = "";
    $res = qx(cat $_[0]) if (-r $_[0]);
    return $res;
  }
  
  sub which($)
  {
  	my $file = shift;
  	my @path = split ":", $ENV{PATH};
  
  	foreach my $dir(@path) {
  		my $name = $dir.'/'.$file;
  		return $name if (-x $name );
  	}
  	return undef;
  }
  
  #
  # Subroutines that check distro-specific hints
  #
  
  sub give_debian_hints()
  {
  	my %map = (
  		"python-sphinx"		=> "python3-sphinx",
  		"sphinx_rtd_theme"	=> "python3-sphinx-rtd-theme",

  		"ensurepip"		=> "python3-venv",

  		"virtualenv"		=> "virtualenv",

  		"dot"			=> "graphviz",
  		"convert"		=> "imagemagick",
  		"Pod::Usage"		=> "perl-modules",
  		"xelatex"		=> "texlive-xetex",

  		"rsvg-convert"		=> "librsvg2-bin",

  	);
  
  	if ($pdf) {

  		check_missing_file(["/usr/share/texlive/texmf-dist/tex/latex/ctex/ctexhook.sty"],
  				   "texlive-lang-chinese", 2);

  		check_missing_file(["/usr/share/fonts/truetype/dejavu/DejaVuSans.ttf"],

  				   "fonts-dejavu", 2);

  		check_missing_file(["/usr/share/fonts/noto-cjk/NotoSansCJK-Regular.ttc",

  				    "/usr/share/fonts/opentype/noto/NotoSansCJK-Regular.ttc",
  				    "/usr/share/fonts/opentype/noto/NotoSerifCJK-Regular.ttc"],

  				   "fonts-noto-cjk", 2);

  	}

  	check_program("dvipng", 2) if ($pdf);

  	check_missing(\%map);
  
  	return if (!$need && !$optional);
  	printf("You should run:
  
  \tsudo apt-get install $install
  ");
  }
  
  sub give_redhat_hints()
  {
  	my %map = (
  		"python-sphinx"		=> "python3-sphinx",
  		"sphinx_rtd_theme"	=> "python3-sphinx_rtd_theme",
  		"virtualenv"		=> "python3-virtualenv",

  		"dot"			=> "graphviz",
  		"convert"		=> "ImageMagick",
  		"Pod::Usage"		=> "perl-Pod-Usage",
  		"xelatex"		=> "texlive-xetex-bin",

  		"rsvg-convert"		=> "librsvg2-tools",

  	);

  	my @fedora26_opt_pkgs = (
  		"graphviz-gd",		# Fedora 26: needed for PDF support
  	);

  	my @fedora_tex_pkgs = (
  		"texlive-collection-fontsrecommended",
  		"texlive-collection-latex",

  		"texlive-xecjk",

  		"dejavu-sans-fonts",
  		"dejavu-serif-fonts",
  		"dejavu-sans-mono-fonts",
  	);

  	#
  	# Checks valid for RHEL/CentOS version 7.x.
  	#

  	my $old = 0;
  	my $rel;
  	$rel = $1 if ($system_release =~ /release\s+(\d+)/);

  	if (!($system_release =~ /Fedora/)) {

  		$map{"virtualenv"} = "python-virtualenv";

  		if ($rel && $rel < 8) {
  			$old = 1;
  			$pdf = 0;

  			printf("Note: texlive packages on RHEL/CENTOS <= 7 are incomplete. Can't support PDF output
  ");
  			printf("If you want to build PDF, please read:
  ");
  			printf("\thttps://www.systutorials.com/241660/how-to-install-tex-live-on-centos-7-linux/
  ");
  		}
  	} else {
  		if ($rel && $rel < 26) {
  			$old = 1;
  		}
  	}
  	if (!$rel) {
  		printf("Couldn't identify release number
  ");
  		$old = 1;
  		$pdf = 0;
  	}

  	if ($pdf) {

  		check_missing_file(["/usr/share/fonts/google-noto-cjk/NotoSansCJK-Regular.ttc"],

  				   "google-noto-sans-cjk-ttc-fonts", 2);
  	}

  	check_rpm_missing(\@fedora26_opt_pkgs, 2) if ($pdf && !$old);
  	check_rpm_missing(\@fedora_tex_pkgs, 2) if ($pdf);
  	check_missing_tex(2) if ($pdf);

  	check_missing(\%map);
  
  	return if (!$need && !$optional);

  	if (!$old) {

  		# dnf, for Fedora 18+
  		printf("You should run:
  
  \tsudo dnf install -y $install
  ");
  	} else {
  		# yum, for RHEL (and clones) or Fedora version < 18
  		printf("You should run:
  
  \tsudo yum install -y $install
  ");
  	}

  }
  
  sub give_opensuse_hints()
  {
  	my %map = (
  		"python-sphinx"		=> "python3-sphinx",
  		"sphinx_rtd_theme"	=> "python3-sphinx_rtd_theme",
  		"virtualenv"		=> "python3-virtualenv",

  		"dot"			=> "graphviz",
  		"convert"		=> "ImageMagick",
  		"Pod::Usage"		=> "perl-Pod-Usage",
  		"xelatex"		=> "texlive-xetex-bin",
  	);

  	# On Tumbleweed, this package is also named rsvg-convert
  	$map{"rsvg-convert"} = "rsvg-view" if (!($system_release =~ /Tumbleweed/));

  	my @suse_tex_pkgs = (
  		"texlive-babel-english",
  		"texlive-caption",
  		"texlive-colortbl",
  		"texlive-courier",
  		"texlive-dvips",
  		"texlive-helvetic",
  		"texlive-makeindex",
  		"texlive-metafont",
  		"texlive-metapost",
  		"texlive-palatino",
  		"texlive-preview",
  		"texlive-times",
  		"texlive-zapfchan",
  		"texlive-zapfding",
  	);

  	$map{"latexmk"} = "texlive-latexmk-bin";

  	# FIXME: add support for installing CJK fonts
  	#
  	# I tried hard, but was unable to find a way to install
  	# "Noto Sans CJK SC" on openSUSE

  	check_rpm_missing(\@suse_tex_pkgs, 2) if ($pdf);
  	check_missing_tex(2) if ($pdf);

  	check_missing(\%map);
  
  	return if (!$need && !$optional);
  	printf("You should run:
  
  \tsudo zypper install --no-recommends $install
  ");
  }

  sub give_mageia_hints()
  {
  	my %map = (
  		"python-sphinx"		=> "python3-sphinx",
  		"sphinx_rtd_theme"	=> "python3-sphinx_rtd_theme",
  		"virtualenv"		=> "python3-virtualenv",

  		"dot"			=> "graphviz",
  		"convert"		=> "ImageMagick",
  		"Pod::Usage"		=> "perl-Pod-Usage",
  		"xelatex"		=> "texlive",

  		"rsvg-convert"		=> "librsvg2",

  	);
  
  	my @tex_pkgs = (
  		"texlive-fontsextra",
  	);

  	$map{"latexmk"} = "texlive-collection-basic";

  	my $packager_cmd;
  	my $noto_sans;
  	if ($system_release =~ /OpenMandriva/) {
  		$packager_cmd = "dnf install";
  		$noto_sans = "noto-sans-cjk-fonts";
  		@tex_pkgs = ( "texlive-collection-fontsextra" );
  	} else {
  		$packager_cmd = "urpmi";
  		$noto_sans = "google-noto-sans-cjk-ttc-fonts";
  	}

  	if ($pdf) {

  		check_missing_file(["/usr/share/fonts/google-noto-cjk/NotoSansCJK-Regular.ttc",
  				    "/usr/share/fonts/TTF/NotoSans-Regular.ttf"],
  				   $noto_sans, 2);

  	}

  	check_rpm_missing(\@tex_pkgs, 2) if ($pdf);

  	check_missing(\%map);
  
  	return if (!$need && !$optional);

  	printf("You should run:
  
  \tsudo $packager_cmd $install
  ");

  }

  sub give_arch_linux_hints()
  {
  	my %map = (
  		"sphinx_rtd_theme"	=> "python-sphinx_rtd_theme",
  		"virtualenv"		=> "python-virtualenv",

  		"dot"			=> "graphviz",
  		"convert"		=> "imagemagick",
  		"xelatex"		=> "texlive-bin",

  		"latexmk"		=> "texlive-core",

  		"rsvg-convert"		=> "extra/librsvg",

  	);
  
  	my @archlinux_tex_pkgs = (
  		"texlive-core",
  		"texlive-latexextra",
  		"ttf-dejavu",
  	);

  	check_pacman_missing(\@archlinux_tex_pkgs, 2) if ($pdf);

  	if ($pdf) {

  		check_missing_file(["/usr/share/fonts/noto-cjk/NotoSansCJK-Regular.ttc"],

  				   "noto-fonts-cjk", 2);
  	}

  	check_missing(\%map);
  
  	return if (!$need && !$optional);
  	printf("You should run:
  
  \tsudo pacman -S $install
  ");
  }
  
  sub give_gentoo_hints()
  {
  	my %map = (
  		"sphinx_rtd_theme"	=> "dev-python/sphinx_rtd_theme",
  		"virtualenv"		=> "dev-python/virtualenv",

  		"dot"			=> "media-gfx/graphviz",
  		"convert"		=> "media-gfx/imagemagick",
  		"xelatex"		=> "dev-texlive/texlive-xetex media-fonts/dejavu",

  		"rsvg-convert"		=> "gnome-base/librsvg",

  	);

  	check_missing_file(["/usr/share/fonts/dejavu/DejaVuSans.ttf"],

  			   "media-fonts/dejavu", 2) if ($pdf);

  	if ($pdf) {

  		check_missing_file(["/usr/share/fonts/noto-cjk/NotoSansCJKsc-Regular.otf",
  				    "/usr/share/fonts/noto-cjk/NotoSerifCJK-Regular.ttc"],

  				   "media-fonts/noto-cjk", 2);
  	}

  	check_missing(\%map);
  
  	return if (!$need && !$optional);

  
  	printf("You should run:
  
  ");

  
  	my $imagemagick = "media-gfx/imagemagick svg png";
  	my $cairo = "media-gfx/graphviz cairo pdf";
  	my $portage_imagemagick = "/etc/portage/package.use/imagemagick";
  	my $portage_cairo = "/etc/portage/package.use/graphviz";

  	if (qx(grep imagemagick $portage_imagemagick 2>/dev/null) eq "") {

  		printf("\tsudo su -c 'echo \"$imagemagick\" > $portage_imagemagick'
  ")
  	}

  	if (qx(grep graphviz $portage_cairo 2>/dev/null) eq  "") {

  		printf("\tsudo su -c 'echo \"$cairo\" > $portage_cairo'
  ");
  	}

  	printf("\tsudo emerge --ask $install
  ");

  }
  
  sub check_distros()
  {
  	# Distro-specific hints
  	if ($system_release =~ /Red Hat Enterprise Linux/) {
  		give_redhat_hints;
  		return;
  	}

  	if ($system_release =~ /CentOS/) {
  		give_redhat_hints;
  		return;
  	}
  	if ($system_release =~ /Scientific Linux/) {
  		give_redhat_hints;
  		return;
  	}
  	if ($system_release =~ /Oracle Linux Server/) {
  		give_redhat_hints;
  		return;
  	}

  	if ($system_release =~ /Fedora/) {
  		give_redhat_hints;
  		return;
  	}
  	if ($system_release =~ /Ubuntu/) {
  		give_debian_hints;
  		return;
  	}
  	if ($system_release =~ /Debian/) {
  		give_debian_hints;
  		return;
  	}
  	if ($system_release =~ /openSUSE/) {
  		give_opensuse_hints;
  		return;
  	}

  	if ($system_release =~ /Mageia/) {
  		give_mageia_hints;
  		return;
  	}

  	if ($system_release =~ /OpenMandriva/) {
  		give_mageia_hints;
  		return;
  	}

  	if ($system_release =~ /Arch Linux/) {
  		give_arch_linux_hints;
  		return;
  	}
  	if ($system_release =~ /Gentoo/) {
  		give_gentoo_hints;
  		return;
  	}
  
  	#
  	# Fall-back to generic hint code for other distros
  	# That's far from ideal, specially for LaTeX dependencies.
  	#
  	my %map = (
  		"sphinx-build" => "sphinx"
  	);

  	check_missing_tex(2) if ($pdf);

  	check_missing(\%map);
  	print "I don't know distro $system_release.
  ";
  	print "So, I can't provide you a hint with the install procedure.
  ";
  	print "There are likely missing dependencies.
  ";
  }
  
  #
  # Common dependencies
  #

  sub deactivate_help()
  {

  	printf "
  If you want to exit the virtualenv, you can use:
  ";

  	printf "\tdeactivate
  ";
  }

  sub get_virtenv()
  {

  	my $ver;

  	my $min_activate = "$ENV{'PWD'}/${virtenv_prefix}${min_version}/bin/activate";
  	my @activates = glob "$ENV{'PWD'}/${virtenv_prefix}*/bin/activate";
  
  	@activates = sort {$b cmp $a} @activates;

  	foreach my $f (@activates) {
  		next if ($f lt $min_activate);
  
  		my $sphinx_cmd = $f;
  		$sphinx_cmd =~ s/activate/sphinx-build/;
  		next if (! -f $sphinx_cmd);
  
  		my $ver = get_sphinx_version($sphinx_cmd);
  		if ($need_sphinx && ($ver ge $min_version)) {
  			return ($f, $ver);
  		} elsif ($ver gt $cur_version) {
  			return ($f, $ver);
  		}
  	}
  	return ("", "");
  }

  sub recommend_sphinx_upgrade()

  {

  	my $venv_ver;

  
  	# Avoid running sphinx-builds from venv if $cur_version is good

  	if ($cur_version && ($cur_version ge $rec_version)) {
  		$latest_avail_ver = $cur_version;
  		return;
  	}

  
  	# Get the highest version from sphinx_*/bin/sphinx-build and the
  	# corresponding command to activate the venv/virtenv

  	$activate_cmd = get_virtenv();

  	# Store the highest version from Sphinx existing virtualenvs
  	if (($activate_cmd ne "") && ($venv_ver gt $cur_version)) {

  		$latest_avail_ver = $venv_ver;
  	} else {
  		$latest_avail_ver = $cur_version if ($cur_version);
  	}

  	# As we don't know package version of Sphinx, and there's no
  	# virtual environments, don't check if upgrades are needed
  	if (!$virtualenv) {
  		return if (!$latest_avail_ver);
  	}
  
  	# Either there are already a virtual env or a new one should be created
  	$need_pip = 1;
  
  	# Return if the reason is due to an upgrade or not
  	if ($latest_avail_ver lt $rec_version) {
  		$rec_sphinx_upgrade = 1;
  	}
  }
  
  #
  # The logic here is complex, as it have to deal with different versions:
  #	- minimal supported version;
  #	- minimal PDF version;
  #	- recommended version.
  # It also needs to work fine with both distro's package and venv/virtualenv
  sub recommend_sphinx_version($)
  {
  	my $virtualenv_cmd = shift;
  
  	if ($latest_avail_ver lt $min_pdf_version) {
  		print "note: If you want pdf, you need at least Sphinx $min_pdf_version.
  ";
  	}
  
  	# Version is OK. Nothing to do.
  	return if ($cur_version && ($cur_version ge $rec_version));

  	if (!$need_sphinx) {
  		# sphinx-build is present and its version is >= $min_version
  
  		#only recommend enabling a newer virtenv version if makes sense.
  		if ($latest_avail_ver gt $cur_version) {

  			printf "
  You may also use the newer Sphinx version $latest_avail_ver with:
  ";

  			printf "\tdeactivate
  "  if ($ENV{'PWD'} =~ /${virtenv_prefix}/);

  			printf "\t. $activate_cmd
  ";

  			deactivate_help();
  
  			return;
  		}
  		return if ($latest_avail_ver ge $rec_version);
  	}
  
  	if (!$virtualenv) {
  		# No sphinx either via package or via virtenv. As we can't
  		# Compare the versions here, just return, recommending the
  		# user to install it from the package distro.
  		return if (!$latest_avail_ver);
  
  		# User doesn't want a virtenv recommendation, but he already
  		# installed one via virtenv with a newer version.
  		# So, print commands to enable it
  		if ($latest_avail_ver gt $cur_version) {

  			printf "
  You may also use the Sphinx virtualenv version $latest_avail_ver with:
  ";

  			printf "\tdeactivate
  "  if ($ENV{'PWD'} =~ /${virtenv_prefix}/);

  			printf "\t. $activate_cmd
  ";

  			deactivate_help();
  
  			return;
  		}
  		print "
  ";
  	} else {
  		$need++ if ($need_sphinx);
  	}
  
  	# Suggest newer versions if current ones are too old
  	if ($latest_avail_ver && $cur_version ge $min_version) {
  		# If there's a good enough version, ask the user to enable it
  		if ($latest_avail_ver ge $rec_version) {

  			printf "
  Need to activate Sphinx (version $latest_avail_ver) on virtualenv with:
  ";
  			printf "\t. $activate_cmd
  ";

  			deactivate_help();
  
  			return;
  		}
  
  		# Version is above the minimal required one, but may be
  		# below the recommended one. So, print warnings/notes
  
  		if ($latest_avail_ver lt $rec_version) {
  			print "Warning: It is recommended at least Sphinx version $rec_version.
  ";

  		}
  	}
  
  	# At this point, either it needs Sphinx or upgrade is recommended,
  	# both via pip
  
  	if ($rec_sphinx_upgrade) {
  		if (!$virtualenv) {
  			print "Instead of install/upgrade Python Sphinx pkg, you could use pip/pypi with:
  
  ";
  		} else {
  			print "To upgrade Sphinx, use:
  
  ";
  		}
  	} else {
  		print "Sphinx needs to be installed either as a package or via pip/pypi with:
  ";
  	}
  
  	$python_cmd = find_python_no_venv();

  	printf "\t$virtualenv_cmd $virtenv_dir
  ";

  	printf "\t. $virtenv_dir/bin/activate
  ";
  	printf "\tpip install -r $requirement_file
  ";
  	deactivate_help();
  }

  sub check_needs()
  {

  	# Check if Sphinx is already accessible from current environment

  	check_sphinx();

  	if ($system_release) {

  		print "Detected OS: $system_release.
  ";

  	} else {

  		print "Unknown OS
  ";

  	}

  	printf "Sphinx version: %s
  
  ", $cur_version if ($cur_version);

  	# Check python command line, trying first python3
  	$python_cmd = findprog("python3");
  	$python_cmd = check_program("python", 0) if (!$python_cmd);
  
  	# Check the type of virtual env, depending on Python version
  	if ($python_cmd) {
  		if ($virtualenv) {
  			my $tmp = qx($python_cmd --version 2>&1);
  			if ($tmp =~ m/(\d+\.)(\d+\.)/) {

  				if ($1 < 3) {

  					# Fail if it finds python2 (or worse)
  					die "Python 3 is required to build the kernel docs
  ";

  				}

  				if ($1 == 3 && $2 < 3) {
  					# Need Python 3.3 or upper for venv
  					$need_virtualenv = 1;
  				}

  			} else {
  				die "Warning: couldn't identify $python_cmd version!";
  			}
  		} else {
  			add_package("python-sphinx", 0);
  		}
  	}

  	recommend_sphinx_upgrade();

  	my $virtualenv_cmd;

  
  	if ($need_pip) {
  		# Set virtualenv command line, if python < 3.3
  		if ($need_virtualenv) {
  			$virtualenv_cmd = findprog("virtualenv-3");
  			$virtualenv_cmd = findprog("virtualenv-3.5") if (!$virtualenv_cmd);
  			if (!$virtualenv_cmd) {
  				check_program("virtualenv", 0);
  				$virtualenv_cmd = "virtualenv";
  			}
  		} else {
  			$virtualenv_cmd = "$python_cmd -m venv";
  			check_python_module("ensurepip", 0);

  		}
  	}

  	# Check for needed programs/tools

  	check_perl_module("Pod::Usage", 0);
  	check_program("make", 0);
  	check_program("gcc", 0);
  	check_python_module("sphinx_rtd_theme", 1) if (!$virtualenv);

  	check_program("dot", 1);
  	check_program("convert", 1);

  
  	# Extra PDF files - should use 2 for is_optional
  	check_program("xelatex", 2) if ($pdf);
  	check_program("rsvg-convert", 2) if ($pdf);
  	check_program("latexmk", 2) if ($pdf);

  	# Do distro-specific checks and output distro-install commands

  	check_distros();

  	if (!$python_cmd) {
  		if ($need == 1) {
  			die "Can't build as $need mandatory dependency is missing";
  		} elsif ($need) {
  			die "Can't build as $need mandatory dependencies are missing";
  		}
  	}
  
  	# Check if sphinx-build is called sphinx-build-3

  	if ($need_symlink) {
  		printf "\tsudo ln -sf %s /usr/bin/sphinx-build
  
  ",
  		       which("sphinx-build-3");
  	}

  	recommend_sphinx_version($virtualenv_cmd);

  	printf "
  ";

  	print "All optional dependencies are met.
  " if (!$optional);

  
  	if ($need == 1) {
  		die "Can't build as $need mandatory dependency is missing";
  	} elsif ($need) {
  		die "Can't build as $need mandatory dependencies are missing";
  	}
  
  	print "Needed package dependencies are met.
  ";
  }
  
  #
  # Main
  #
  
  while (@ARGV) {
  	my $arg = shift(@ARGV);
  
  	if ($arg eq "--no-virtualenv") {
  		$virtualenv = 0;
  	} elsif ($arg eq "--no-pdf"){
  		$pdf = 0;

  	} elsif ($arg eq "--version-check"){
  		$version_check = 1;

  	} else {

  		print "Usage:
  \t$0 <--no-virtualenv> <--no-pdf> <--version-check>
  
  ";
  		print "Where:
  ";
  		print "\t--no-virtualenv\t- Recommend installing Sphinx instead of using a virtualenv
  ";
  		print "\t--version-check\t- if version is compatible, don't check for missing dependencies
  ";
  		print "\t--no-pdf\t- don't check for dependencies required to build PDF docs
  
  ";

  		exit -1;
  	}
  }
  
  #
  # Determine the system type. There's no standard unique way that would
  # work with all distros with a minimal package install. So, several
  # methods are used here.
  #
  # By default, it will use lsb_release function. If not available, it will
  # fail back to reading the known different places where the distro name
  # is stored
  #
  
  $system_release = qx(lsb_release -d) if which("lsb_release");
  $system_release =~ s/Description:\s*// if ($system_release);
  $system_release = catcheck("/etc/system-release") if !$system_release;
  $system_release = catcheck("/etc/redhat-release") if !$system_release;
  $system_release = catcheck("/etc/lsb-release") if !$system_release;
  $system_release = catcheck("/etc/gentoo-release") if !$system_release;

  
  # This seems more common than LSB these days
  if (!$system_release) {
  	my %os_var;
  	if (open IN, "cat /etc/os-release|") {
  		while (<IN>) {
  			if (m/^([\w\d\_]+)=\"?([^\"]*)\"?
  /) {
  				$os_var{$1}=$2;
  			}
  		}
  		$system_release = $os_var{"NAME"};
  		if (defined($os_var{"VERSION_ID"})) {
  			$system_release .= " " . $os_var{"VERSION_ID"} if (defined($os_var{"VERSION_ID"}));
  		} else {
  			$system_release .= " " . $os_var{"VERSION"};
  		}
  	}
  }

  $system_release = catcheck("/etc/issue") if !$system_release;
  $system_release =~ s/\s+$//;
  
  check_needs;