#!/usr/bin/env perl

# Some aspects of this approach are due to:
# http://blog.bluefeet.net/2011/08/chained-git-hooks/
# see: http://web.archive.org/web/20111231092040/http://blog.bluefeet.net/2011/08/chained-git-hooks/
#
# This implementation using IO::Pipe is
# Copyright (C) 2020, 2022  Sean Whitton <spwhitton@spwhitton.name>
#
# This program is free software: you can redistribute it and/or modify
# it under the terms of the GNU General Public License as published by
# the Free Software Foundation, either version 3 of the License, or (at
# your option) any later version.
#
# This program is distributed in the hope that it will be useful, but
# WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
# General Public License for more details.
#
# You should have received a copy of the GNU General Public License
# along with this program.  If not, see <http://www.gnu.org/licenses/>.

# Use by symlinking this hook to .git/hooks/pre-push (or whichever
# hook you want to chain) and then add your hooks as
# .git/hooks/pre-push_01foo, .git/hooks/pre-push_02bar etc.

use strict;
use warnings;

use IO::Pipe;
use File::Basename qw(basename dirname);
use File::Spec::Functions qw(abs2rel rel2abs);

(my $hook_type = $0) =~ s{^.+/}{};

my @hooks;

chomp(my $git_dir = `git rev-parse --absolute-git-dir`);
my $rel = abs2rel dirname($git_dir), $ENV{HOME};

# Partially tidy up previous git hooks setup.
-l and readlink =~ m#/chained_hook$# and unlink
  for "$git_dir/hooks/$hook_type";

for my $dir (grep -d, "$git_dir/hooks",
    "$ENV{HOME}/src/dotfiles/hooks/git/$rel") {
    opendir(my $dirh, $dir);
    push @hooks, grep -x, map rel2abs($_, $dir),
      sort grep /\A($hook_type\z|${hook_type}_)/, readdir $dirh;
}

my @stdin = <STDIN>;

foreach my $hook (@hooks) {
    my $pipe = IO::Pipe->new;
    my $pid  = fork;
    die "fork() failed: $!" unless defined $pid;
    if ($pid) {
        $pipe->writer;
        print $pipe $_ for @stdin;
        $pipe->close;
        wait;
        # give up as soon as one hook fails; since we sort the hooks,
        # we can put more expensive hooks later in the sequence
        die "hook $hook exited non-zero" if $?;
    } else {
        $pipe->reader;
        open STDIN, "<&=" . $pipe->fileno
          or die "couldn't open child's STDIN";
        exec $hook, @ARGV;
    }
}