#!/usr/bin/env perl
#
# Copyright (c) 2022 Omar Polo <op@omarpolo.com>
#
# Permission to use, copy, modify, and distribute this software for any
# purpose with or without fee is hereby granted, provided that the above
# copyright notice and this permission notice appear in all copies.
#
# THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
# WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
# MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
# ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
# WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
# ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
# OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
#
# subst -- filter that replaces key=values pairs
#
# usage: subst key1=val1 [... keyn=valn] [files...]
#
# Use `--' before the first file if it may contain an = in its name.
# If no files are given, read and substitute from standard input.

use v5.10;
use strict;
use warnings;

my @args = ();

while (1) {
	$_ = shift;
	last if !$_;

	if ($_ eq '--') {
		last;
	} elsif ($_ !~ m/=/) {
		unshift @ARGV, $_;
		last;
	}

	my ($match, $repl) = m/^([^\s]*)=(.*)$/;
	push @args, "-e", "s,$match,$repl,g";
}

# OK, shelling out to sed is a bit lame...
exec "sed", @args, @ARGV;