#!/usr/bin/env perl

# reservoir -- read stdin until EOF, and _then_ write it all to stdout.

$usage =
  "usage: reservoir [ -o file | -O file ]\n".
  "where: -O file                open and write to file after end of input\n".
  "       -o file                same, but only if output is non-empty\n".
  " also: reservoir --version    report version number\n" .
  "       reservoir --help       display this help text\n" .
  "       reservoir --licence    display (MIT) licence text\n";

$licence =
  "reservoir is copyright 2005,2008 Simon Tatham.\n" .
  "\n" .
  "Permission is hereby granted, free of charge, to any person\n" .
  "obtaining a copy of this software and associated documentation files\n" .
  "(the \"Software\"), to deal in the Software without restriction,\n" .
  "including without limitation the rights to use, copy, modify, merge,\n" .
  "publish, distribute, sublicense, and/or sell copies of the Software,\n" .
  "and to permit persons to whom the Software is furnished to do so,\n" .
  "subject to the following conditions:\n" .
  "\n" .
  "The above copyright notice and this permission notice shall be\n" .
  "included in all copies or substantial portions of the Software.\n" .
  "\n" .
  "THE SOFTWARE IS PROVIDED \"AS IS\", WITHOUT WARRANTY OF ANY KIND,\n" .
  "EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF\n" .
  "MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND\n" .
  "NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS\n" .
  "BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN\n" .
  "ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN\n" .
  "CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE\n" .
  "SOFTWARE.\n";

$outputfile = undef;
$allowemptyoutput = 0;

while ($_=shift @ARGV) {
  last if /^--$/;
  unshift (@ARGV, $_), last unless /^-(.*)/;
  $arg = $1;
  if ($arg eq "-help") {
    print STDERR $usage;
    exit 0;
  } elsif ($arg eq "-version") {
    if ('$Revision$' =~ /Revision:\s+(\d+)/) {
	print "reservoir revision $1\n";
    } else {
	print "reservoir: unknown revision\n";
    }
    exit 0;
  } elsif ($arg eq "-licence" or $arg eq "-license") {
    print $licence;
    exit 0;
  } elsif ($arg =~ /^([oO])(.*)$/) {
    $allowemptyoutput = ($1 eq "O");
    $outputfile = $2;
    $outputfile = shift @ARGV if $outputfile eq "";
    die "reservoir: expected file name after '-$1'\n" if $outputfile eq "";
  } else {
    die "reservoir: unrecognised option '-$arg'\n";
  }
}

die $usage if $#ARGV > 0;

$data = '';

$data .= $_ while <STDIN>;

if (defined $outputfile) {
    exit unless length($data) or $allowemptyoutput;
    open OUT, ">$outputfile" or die "$outputfile: open: $!\n";
    select OUT;
}
print $data;