#!/usr/bin/perl

# Copyright (C) 2007-2022 Ole Tange, http://ole.tange.dk and Free
# Software Foundation, Inc.
#
# This program is free software; you can redistribute it and/or modify
# it under the terms of the GNU General Public License as published by
# the Free Software Foundation; either version 3 of the License, or
# (at your option) any later version.
#
# This program is distributed in the hope that it will be useful, but
# WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
# General Public License for more details.
#
# You should have received a copy of the GNU General Public License
# along with this program; if not, see <https://www.gnu.org/licenses/>
# or write to the Free Software Foundation, Inc., 51 Franklin St,
# Fifth Floor, Boston, MA 02110-1301 USA
#
# SPDX-FileCopyrightText: 2021-2022 Ole Tange, http://ole.tange.dk and Free Software and Foundation, Inc.
# SPDX-License-Identifier: GPL-3.0-or-later

# Convert .pod file containing:
#
#   =item --option
#   
#   See also: --other-option
#
# to a graph.pdf with link between --option and --other-option

$pod=join("",<>);
# Remove stuff before OPTIONS
$pod=~s/^.*=head1 OPTIONS//s;
# Remove from EXAMPLES (which is next section) and till end
$pod=~s/=head1 EXAMPLES.*//s;
# Remove =over / =back pairs
$pod=~s/^.*?=over//s;
$pod=~s/=back\s*$//s;
$pod=~s/=over.*?=back//sg;

$in_text = 0;
$in_item = 0;
$in_see_also = 0;

for(split(/\n\n+/,$pod)) {
    if(/^See also:\s+(\S.*)/s) {
	# "See also" paragraph
	$lex = "seealso";
	$in_text = 0;
	$in_item = 0;
	$in_see_only = 1;
    } elsif(/^=item\s+(B<[{]=.*?perl expression.*?=[}]>|[IB]<.*?>)(\s|$)/s) {
	# "=item" paragraph
	$lex = "item";
	$in_text = 0;
	$in_item = 1;
	$in_see_only = 0;
    } elsif(/\S/) {
	# else it is just text
	$lex = "text";
	$in_text = 1;
	$in_item = 0;
	$in_see_only = 0;
    }
  
    if($lex eq "seealso") {
	# We found "See also": output edge
	if($lastlex eq "item") {
	    @saveditems = @items;
	    @items = ();
	}
	my $to = $1;
	# Edge from = item/item/item
	my $from = (join "/",
		    map {
			s/I<(.*?)>/$1/g;
			s/B<(.*?)>/$1/g;
			$_ }
		    @saveditems[0]);
	my @to;
	while($to =~ s/(B<[{]=.*?perl expression.*?=[}]>|[BI]<.*?>)(\s|$)//) {
	    my $v = $1;
	    push @to, map {
			      s/I<(.*?)>/$1/g;
			      s/B<(.*?)>/$1/g;
			      $_;
	    } $v;
	}
	map {
	    if(not $seen{$from,$_}++
	       and
	       not $seen{$_,$from}++) {
		push @nodelines, "\"$from\" -- \"$_\"\n"
	    }
	} @to;
	
    } elsif($lex eq "text") {
	if($lastlex eq "item") {
	    @saveditems = @items;
	    @items = ();
	}
    } elsif($lex eq "item") {
	push(@items,$1);
    }	
    $lastlex=$lex;
}


sub header() {
    return q[
	graph test123 {
	    graph [splines=true; overlap=false;];
	    labelloc="t";
	    label="Related map for options for GNU Parallel\nFind the options you use and learn about the options related to it";fontsize=33;
	    
	    "{}"[margin=0.3;]
		"--sshlogin"[margin=0.3;]
		"--pipe"[margin=0.3;]
		":::"[margin=0.3;]
		"-X"[margin=0.3;]
	];
}

open(GRAPHVIZ,"|-","tee foo.dot |neato -Gepsilon=.000000001 -Tpdf") || die;
print GRAPHVIZ header(), (sort { rand()*3 -1 } @nodelines), "}";
close GRAPHVIZ;