#!/usr/bin/perl -w
use strict;
use Carp;
use Data::Dumper;

my @d = <>;
unshift @d, "# dummy line to make line 1 index 1 in \@d\n";

our $i_last_l_ok = -1;
our $count_i_last_l_ok;

sub l_ok ($) {
    my ($i) = @_;

    if ($i == $i_last_l_ok) {
	confess $i if $count_i_last_l_ok++ > 50;
    } else {
	$count_i_last_l_ok = 0;
	$i_last_l_ok = $i;
    }

    return unless $i < @d;
    $_ = $d[$i];
    #print STDERR "L $i\n";
    1;
}

sub l ($) {
    my ($i) = @_;
    confess $i unless l_ok $i;
};

our ($ifilehead, $ihunkhead, $ichunkstart, $ichunkend);
our ($before, $after);

sub analyse_chunk () {
    print Dumper($ichunkstart, $ichunkend, $before, $after);
    flush STDOUT;
}

for ($ifilehead = 0; l_ok $ifilehead; $ifilehead++) {
    m{^diff} or next;
    while (l_ok $ifilehead and m{^diff|^index|^---|^\Q+++\E}) { $ifilehead++ }
    $ihunkhead = $ifilehead;
    while (l_ok $ihunkhead) {
	m{^\@\@} or confess "$ihunkhead $_ ?";
	my $i = $ihunkhead + 1;
	for (; ; $i++) {
	    if (!l_ok $i or m{^ } or m{^\@\@}) {
		if (defined $ichunkstart) {
		    $ichunkend = $i;
		    analyse_chunk();
		    $ichunkstart = $ichunkend = $before = $after = undef;
		}
		l_ok $i or last;
		m{^\@\@} and last;
	    } elsif (m{^[-+]}) {
		my $which = $& eq '-' ? \$before : \$after;
		$ichunkstart //= $i;
		$$which //= '';
		$$which .= $';
	    } else {
		confess "$i $_ ?";
	    }
	}
	$ichunkend = $i;
	$ihunkhead = $i;
    }
}