#!@PERL@ -w

#  This script is free software; you can redistribute it and/or modify
#  it under the terms of the GNU General Public License version 2 as
#  published by the Free Software Foundation.
#
#  See the COPYING and AUTHORS files for more details.

# Extract or update a section from a combined patch + documentation +
# meta information file.

use FileHandle;
use Getopt::Long;
use File::Temp qw(tempfile);
use strict;

my $select;
my $update;

if (!GetOptions("s|select=s" => \$select,
		"u|update=s" => \$update) ||
    (!defined $select && !defined $update)) {
	print STDERR "USAGE: $0 {-s|-u} section file [< replacement]\n";
	exit 1;
}

foreach my $arg (@ARGV) {
	my $fh;

	if (! -e $arg) {
		$fh = new FileHandle("/dev/null");
	} elsif ($arg =~ /\.gz$/) {
		$fh = new FileHandle("gzip -cd $arg |");
	} elsif ($arg =~ /\.bz2$/) {
		$fh = new FileHandle("bzip2 -cd $arg |");
	} else {
		$fh = new FileHandle("< $arg");
	}

	unless ($fh) {
		print STDERR "$arg: $!\n";
		next;
	}

	if (defined $select) {
		my $section = "head";
		my $newline = "";
		while (<$fh>) {
			if (/^%(.*)/) {
				last if $section eq $select;
				$section = $1;
				next;
			}
			if ($section eq $select) {
				print $newline;
				if ($_ eq "\n") {
					$newline = $_;
				} else {
					$newline="";
					print;
				}
			}
		}
	} elsif (defined $update) {
		my ($fh2, $tempname) = tempfile("$arg.XXXXXX");
		if ($arg =~ /\.gz$/) {
			$fh2->close();
			if (! -e $tempname) {
				die "File $tempname disappeared!\n";
			}
			$fh2 = new FileHandle("| gzip -c > $tempname");
		} elsif ($arg =~ /\.bz2$/) {
			$fh2->close();
			if (! -e $tempname) {
				die "File $tempname disappeared!\n";
			}
			$fh2 = new FileHandle("| bzip2 -c > $tempname");
		}
		unless ($fh2) {
			die "$tempname: $!\n";
		}

		# Copy things before updated section
		my $last_was_newline=1; # start first section in first line
		while (<$fh>) {
			if (/^%(.*)/ && $1 eq $update) {
				last;
			}
			$last_was_newline = ($_ eq "\n");
			print $fh2 $_;
		}
		print $fh2 "\n"
			unless ($last_was_newline);

		# Create/replace updated section
		print $fh2 "%$update\n";
		while (<STDIN>) {
			print $fh2 $_;
		}
		print $fh2 "\n";

		# Skip obsolete section
		while (<$fh>) {
			if (/^%(.*)/) {
				print $fh2 $_;
				last;
			}
		}
		# Copy things after updated section
		while (<$fh>) {
			print $fh2 $_;
		}
		unless (close $fh2) {
			die "$arg.patch: $!\n";
		}

		if (-e $arg) {
			unlink "$arg~";
			unless (rename $arg, "$arg~") {
				die "Failed to rename $arg to $arg~: $!\n";
			}
		}
		unless (rename $tempname, $arg) {
			rename("$arg~", $arg);
			die "Failed to rename $arg.parse to $arg: $!\n";
		}
	}
	close $fh;
}