#!/usr/bin/perl
use warnings;
use strict;
use v5.10.1;
use Cwd qw(abs_path);
use File::Spec;
use Getopt::Long;
use Pod::Usage;

my %opts = (
	input => '@BUILDSCRIPT@',
	template_dir => '@TEMPLATE_DIR@',
);

my $template_name_charset = qr/[[:alnum:]+_.@-]/;
my $template_marker = qr/# template/;

sub burp {
	my ($file_name, @lines) = @_;
	open (my $fh, ">", $file_name) || die "can't create $file_name $!" ;
	print $fh @lines;
	close $fh;
}

# read a template marker line and parse values into a hash
# format is "# template (start|input); key=value; key2=value2; ..."
sub parse_template_line {
	my ($line, $filename, $linenumber) = @_;
	my %values;

	my ($marker, @elements) = split(/;\s?/, $line);

	($values{command}) = ($marker =~ /$template_marker (.*)/);

	foreach my $element (@elements) {
		my ($key, $val) = ($element =~ /^([a-z0-9]+)=(.*)$/);
		die "invalid key/value pair $filename:$linenumber: $line"
		    unless $key and $val;
		$values{$key} = $val;
	}

	# end doesn't take arguments
	if ($values{command} ne "end") {
		if (!$values{name}) {
			die "invalid template line: can't find template name\n",
				"$filename:$linenumber: $line";
		}

		unless ($values{name} =~ /^$template_name_charset+$/) {
			die "invalid chars used in name '$values{name}'. allowed: [:alnum:]+_.@-\n",
				"$filename:$linenumber: $line";
		}
	}

	return \%values;
}

# load a template, process possibly existing markers (nested templates)
sub load_template {
	my ($values) = @_;

	my $ret = "";

	my $path;
	if (!$opts{newest} and $values->{version}) {
		$path = "$opts{template_dir}/$values->{name}-$values->{version}.template";
	} else {
		$path = "$opts{template_dir}/$values->{name}.template";
	}

	# resolve symlink(s) and use the real file's name for version detection
	my ($version) = (abs_path($path) =~ /-([0-9.]+)[.]template$/);

	if (!$version) {
		die "Couldn't detect version for template '$values->{name}'";
	}

	my $parsed = process_file($path);

	$ret .= "# template start; name=$values->{name}; version=$version;\n";
	$ret .= $parsed;
	$ret .= "# template end;\n";
	return $ret;
}

# process input file and load templates for all markers found
sub process_file {
	my ($filename) = @_;

	my $ret = "";
	my $nesting_level = 0;
	my $linenumber = 0;

	open (my $fh, "<", $filename) or die "failed to open '$filename': $!";
	my @lines = <$fh>;
	close $fh;

	foreach my $line (@lines) {
		$linenumber++;

		if ($line =~ $template_marker) {
			my $values = parse_template_line($line, $filename, $linenumber);

			given ($values->{command}) {
				when (['start', 'input']) {
					if ($nesting_level == 0) {
						$ret .= load_template($values);
					}
				}

				when ('end') {
					# nothing to do here, just for completeness
				}

				default {
					die "Unknown template marker '$values->{command}'\n",
						"$filename:$linenumber: $line";
				}
			}

			$nesting_level++ if $values->{command} eq "start";
			$nesting_level-- if $values->{command} eq "end";

			# marker lines should never be added
			next;
		}

		# we replace code inside blocks with the template
		# so we ignore the content of the block
		next if $nesting_level > 0;

		$ret .= $line;
	}
	return $ret;
}

Getopt::Long::Configure ("bundling");
GetOptions(
	"help" => sub {pod2usage(-exitval => 0, -verbose => 1); },
	"h" => sub {pod2usage(-exitval => 0, -verbose => 0); },
	"input|p=s" => \$opts{input},
	"output|o=s" => \$opts{output},
	"newest|n" => \$opts{newest},
	"template-dir=s" => \$opts{template_dir},
) or pod2usage(1);

$opts{output} = $opts{input} unless $opts{output};

$opts{input} = "/dev/stdin" if $opts{input} eq "-";
$opts{output} = "/dev/stdout" if $opts{output} eq "-";

burp($opts{output}, process_file($opts{input}));

__END__
=head1 SYNOPSIS

makepkg-template [options]

 Options:
   --input, -p <file>     Build script to read (default: @BUILDSCRIPT@)
   --output, -o <file>    file to output to (default: input file)
   --newest, -n           update templates to newest version
                          (default: use specified version in the template markers)
   --template-dir <dir>   directory to search for templates
                          (default: @TEMPLATE_DIR@)

=cut
# vim: set noet: