#!/usr/bin/perl

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

$pod=join("",<>);
$pod=~s/^.*=head1 OPTIONS//s;
$pod=~s/=head1 EXAMPLES.*//s;
$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) {
	$lex = "seealso";
	$in_text = 0;
	$in_item = 0;
	$in_see_only = 1;
    } elsif(/^=item\s+(B<[{]=.*?perl expression.*?=[}]>|[IB]<.*?>)(\s|$)/s) {
	$lex = "item";
	$in_text = 0;
	$in_item = 1;
	$in_see_only = 0;
    } elsif(/\S/) {
	$lex = "text";
	$in_text = 1;
	$in_item = 0;
	$in_see_only = 0;
    }
  
    if($lex eq "seealso") {
	if($lastlex eq "item") {
	    @saveditems = @items;
	    @items = ();
	}
	my $to = $1;
	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;