#!/usr/bin/perl

use strict;
use warnings FATAL => 'all';

use IO::Pipe;

my $pipe = IO::Pipe->new();

map { tail($_) } @ARGV;

$pipe->reader();

while (<$pipe>) {
  print;
}

sub parse_host_file {
  my $spec = shift;
  if ( my ( $h, $f ) = $spec =~ m/^([^:]+):(.+)$/ ) {
    return ( $h, $f );
  }
  else {
    return ( undef, $spec );
  }
}

sub tail {
  my ( $spec ) = @_;
  my ( $host, $file ) = parse_host_file($spec);
  my $cmd = $host ? ['ssh', $host, 'tail', '-F', $file ] : ['tail', '-F', $file ];
  my $prefix = $host ? "$host: " : "";
  my $pid = fork();
  if ( $pid ) { # parent
    return $pid;
  }
  elsif ( defined($pid) ) { # child
    $pipe->writer();
    open( my $fh, '-|', @$cmd ) or exit 255;
    while ( <$fh> ) {
      s/^/$prefix/;
      $pipe->print($_);
      $pipe->flush();
    }
    close($fh);
    exit 0;
  }
  else {
    die "Failed to tail $spec (fork failed): $!";
  }
}