#!/usr/bin/env perl

package Git::Hooks::CheckWhitespace;
# ABSTRACT: Git::Hooks plugin for checking whitespace errors
$Git::Hooks::CheckWhitespace::VERSION = '2.5.0';
use 5.010;
use utf8;
use strict;
use warnings;
use Git::Hooks;
use Text::Glob qw/glob_to_regex/;

(my $CFG = __PACKAGE__) =~ s/.*::/githooks./;

# This routine can act both as an update or a pre-receive hook.
sub check_affected_refs {
    my ($git) = @_;

    return 1 if $git->im_admin();

    my $errors = 0;

    foreach my $ref ($git->get_affected_refs()) {
        my ($old_commit, $new_commit) = $git->get_affected_ref_range($ref);

        # If the referece is being deleted we have nothing to check
        next if $new_commit eq $git->undef_commit;

        # If the reference is being created we have to calculate a proper
        # $old_commit to diff against.
        if ($old_commit eq $git->undef_commit) {
            my $last_log;
            my $log_iterator = $git->log($new_commit, qw/--not --all/);
            while (my $log = $log_iterator->next()) {
                $last_log = $log;
            }
            next unless $last_log;
            my @parents = $last_log->parent;
            if (@parents == 0) {
                # We reached the repository root. Hence, let's consider
                # $old_commit to be the empty tree.
                $old_commit = $git->empty_tree;
            } elsif (@parents == 1) {
                # We reached the first new commit and it's a normal commit. So,
                # let's consider $old_commit to be its parent.
                $old_commit = $parents[0];
            } else {
                # We reached the first new commit and it's a merge commit. So,
                # let's consider $old_commit to be this commit, disregarding
                # only the eventual conflict resolutions.
                $old_commit = $last_log->commit;
            }
        }

        my $output = $git->run(
            {fatal => [-129, -128]},
            qw/diff-tree -r --check/,
            $old_commit eq $git->undef_commit ? $git->empty_tree : $old_commit,
            $new_commit);
        if ($? != 0) {
            $git->fault(<<"EOS", {details => $output});
There are extra whitespaces in the changed files in $ref.
Please, remove them and amend your commit.
EOS
            ++$errors;
        };
    }

    return $errors == 0;
}

sub check_commit {
    my ($git) = @_;

    my $output = $git->run(
        {fatal => [-129, -128]},
        qw/diff-index --check --cached/, $git->get_head_or_empty_tree());
    if ($? == 0) {
        return 1;
    } else {
        $git->fault(<<"EOS", {details => $output});
There are extra whitespaces in the changed files.
Please, remove them and amend your commit.
EOS
        return 0;
    };
}

sub check_patchset {
    my ($git, $opts) = @_;

    return 1 if $git->im_admin();

    my $output = $git->run(
        {fatal => [-129, -128]},
        qw/diff-tree -r -m --check/, $opts->{'--commit'});
    if ($? == 0) {
        return 1;
    } else {
        $git->fault(<<"EOS", {details => $output});
There are extra whitespaces in the changed files.
Please, remove them and amend your commit.
EOS
        return 0;
    };
}

# Install hooks
PRE_COMMIT       \&check_commit;
UPDATE           \&check_affected_refs;
PRE_RECEIVE      \&check_affected_refs;
REF_UPDATE       \&check_affected_refs;
PATCHSET_CREATED \&check_patchset;
DRAFT_PUBLISHED  \&check_patchset;

1;

__END__

=pod

=encoding UTF-8

=head1 NAME

Git::Hooks::CheckWhitespace - Git::Hooks plugin for checking whitespace errors

=head1 VERSION

version 2.5.0

=head1 SYNOPSIS

As a C<Git::Hooks> plugin you don't use this Perl module directly. Instead, you
may configure it in a Git configuration file like this:

  [githooks]
    plugin = CheckWhitespace
    admin = joe molly

The first section enables the plugin and defines the users C<joe> and C<molly>
as administrators, effectivelly exempting them from any restrictions the plugin
may impose.

=head1 DESCRIPTION

This L<Git::Hooks> plugin hooks itself to the hooks below to check if the
contents of files added to or modified in the repository have whitespace
errors as detected by C<git diff --check> command. If they don't, the
commit/push is aborted.

=over

=item * B<pre-commit>

=item * B<update>

=item * B<pre-receive>

=item * B<ref-update>

=item * B<patchset-created>

=item * B<draft-published>

=back

To enable it you should add it to the githooks.plugin configuration
option:

    git config --add githooks.plugin CheckWhitespace

=for Pod::Coverage check_affected_refs check_commit check_patchset

=head1 NAME

CheckWhitespace - Git::Hooks plugin for checking whitespace errors

=head1 CONFIGURATION

There's no configuration needed or provided.

=head1 AUTHOR

Gustavo L. de M. Chaves <gnustavo@cpan.org>

=head1 COPYRIGHT AND LICENSE

This software is copyright (c) 2018 by CPqD <www.cpqd.com.br>.

This is free software; you can redistribute it and/or modify it under
the same terms as the Perl 5 programming language system itself.

=cut