use strict;
use warnings;
use Fcntl;
use Tie::File;
use Carp;
use Data::Dumper;
#use Benchmark;

#variables
#-----------------------
my $test_file =$ENV{FILE_NAME};
unless (defined $test_file) {
    croak "No filename in environment (FILENAME)\n";
}

my $path = $ENV{FILE_PATH};
unless (defined $path ) {
    croak "No path directory in environment (FILE_PATH)\n";
}

my $page_begin = '^PAGE_BEGIN$';
my $mark1 = '%%DELETE_PAGE%%';                                                  #delete a complete page
my @tied_metafile;

#MAIN
#-----------------------
#my $anfang = new Benchmark;                                                     #BENCHMARK BEGIN

sysopen METAFILE, $test_file, O_RDWR  or croak "Can't open $test_file: $!";     #open metafile for read/write
tie @tied_metafile, 'Tie::File', \*METAFILE;
my $stored_indexes_ref = search_mark();                                         #do sub 1
delete_marked ( $stored_indexes_ref );                                          #do sub 2
untie @tied_metafile;
close METAFILE or croak "Can't close $test_file: $!";                           #close metafile

#my $ende = new Benchmark;                                                       #BENCHMARK END

#my $vergangen = timediff ($ende, $anfang);                                      #BENCHMARK
#print "Vergangene Zeit: ", timestr ($vergangen), "\n";                          #BENCHMARK

#SUBS
#-----------------------
sub search_mark {
    my $index = 0;
    my @stored_indexes;                                                         #a helping array with relevant indexes
    foreach my $line ( @tied_metafile ) {
        if ( $line =~ m/$page_begin/) {
	    unshift( @stored_indexes, $index );
	}
        if ( $line =~ m/$mark1/) {
	    my @mark1_match_index;                                              #a helping array with index of mark as first element
	    unshift( @mark1_match_index, $index );
	    unshift( @stored_indexes, \@mark1_match_index );                    #store reverse
	}
	$index++;
    }
    unshift( @stored_indexes,$#tied_metafile+1);                                #necessary if last page should be deleted
    return \@stored_indexes;
}

sub delete_marked {
    my @stored_indexes_ref = shift;
    my $index = 0;
    print Dumper @stored_indexes_ref;
    foreach ( @$stored_indexes_ref ){
	if ( ref(@$stored_indexes_ref[$index]) eq 'ARRAY') {
	    my $del_from = @$stored_indexes_ref[$index+1];
	    my $del_until  = @$stored_indexes_ref[$index-1];
	    my $range = $del_until - $del_from;
	    print "delete from line : ", $del_from, "\n";
            print "delete until line: ", $del_until, "\n";
	    print "Range            : ", $range, "\n";
            splice( @tied_metafile, $del_from, $range);                         #delete last lines first
	}
	$index++;
    }
}

exit 0