#!/usr/bin/env perl
use utf8;
###############################################################################
# This program copies the first few and last few lines of stdin to stdout
# 
# Copyright © 2020 Richard Lesh.  All rights reserved.
###############################################################################

use Utils;
use strict;
use warnings;

MAIN:
{
    binmode(STDOUT, ":utf8");
    binmode(STDERR, ":utf8");
    binmode(STDIN, ":utf8");
    foreach my $arg (@ARGV) {
        utf8::decode($arg);
    }
    my $max_lines = 10;
    if (scalar(@ARGV) == 1) {
        $max_lines = Utils::stoiWithDefault($ARGV[0], 10);
    }

    my $buffer = [(undef) x $max_lines];
    my $line;
    my $count = 0;
    while ($line = <STDIN>) {
        chomp($line);
        $buffer->[$count % $max_lines] = $line;
        if ($count < $max_lines) {
            print $line, "\n";
        }
        ++$count;
    }
    if ($count > $max_lines && $count <= 2 * $max_lines) {
        my $REMAINING = $count - $max_lines;
        for (my $i = 0; $i < $REMAINING; ++$i) {
            print $buffer->[$i], "\n";
        }
    } elsif ($count > 2 * $max_lines) {
        print "...\n";
        for (my $i = 0; $i < $max_lines; ++$i) {
            print $buffer->[($count + $i) % $max_lines], "\n";
        }
    }
}