package Local::MrRepo;

# Copyright (C) 2019 Sean Whitton
#
# 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 <https://www.gnu.org/licenses/>.

use strict;
use warnings;
use lib "$ENV{HOME}/src/dotfiles/perl5";

use Cwd;
use File::Spec::Functions qw(catfile rel2abs);
use Exporter 'import';
use File::Find;

# Quoting perldoc perlmodlib: "As a general rule, if the module is
# trying to be object oriented then export nothing. If it's just a
# collection of functions then @EXPORT_OK anything but use @EXPORT
# with caution."
our @EXPORT_OK = qw( new_repo );

# Local::MrRepo::Repo::Git and its subclass require non-core
# modules, so we might not be able to load them.  If so we'll fall
# back on Local::MrRepo::Repo
#
# ~/bin/locmaint and Local::Homedir use the simpler technique of just
#
#     return unless eval "use Foo::Bar; 1";
#
# at the top of functions that require use Foo::Bar.  However, for
# MrRepo classes we want to rethrow exceptions (other than import
# failures) to make it easier to debug those classes.
#
# The purpose of wrapping conditional module inclusion in BEGIN is to
# provide subroutine definitions etc. to the compiler as early as
# possible.  AFAICT that's not really needed when importing modules
# providing only an OO interface, however, because they don't usually
# export anything at all.  That's why the simpler technique suffices
# over in ~/bin/locmaint and Local::Homedir, for Data::Manip and
# Git::Wrapper.
#
# References: Perl Cookbook 12.2, "Trapping Errors in require or use"
#             Modern Perl, ch. 8, "Catching Exceptions"
my $have_mrrepo_git;            # must not initialise here
BEGIN {
    local $@;
    eval "require Local::MrRepo::Repo::Git";
    if (my $exception = $@) {
        die $exception unless $exception =~ /^Can't locate .+ in \@INC/;
        $have_mrrepo_git = 0;
    } else {
        Local::MrRepo::Git->import();
        local $@;
        eval "require Local::MrRepo::Repo::Git::Annex";
        if (my $exception = $@) {
            die $exception unless $exception =~ /^Can't locate .+ in \@INC/;
            $have_mrrepo_git = 0;
        } else {
            Local::MrRepo::Git::Annex->import();
            $have_mrrepo_git = 1;
        }
    }
}

sub new_repo {
    my $dir = shift;

    # This matches git_test in mr(1).  That means we don't count bare
    # repos, and we're relying on that atm, because ~/lib/nmbug-*
    # should be checked using their custom `mr checkout` commands.  Maybe
    # we should instead be seeing whether `mr config $dir checkout`
    # matches /^git clone/, but that means disagreeing with mr(1)
    # about which repos are git repos.
    if ($have_mrrepo_git && -d catfile($dir, ".git")) {
        if (has_annex_objects($dir)) {
            return Local::MrRepo::Repo::Git::Annex->new($dir);
        } else {
            return Local::MrRepo::Repo::Git->new($dir);
        }
    } else {
        return Local::MrRepo::Repo->new($dir);
    }
}

sub has_annex_objects {
    my $repo = rel2abs(shift);

    my $objects_dir = catfile($repo, ".git", "annex", "objects");
    return 0 unless -d $objects_dir;
    # File::Find::find changes the working directory; undo that
    # (no_chdir doesn't seem to be sufficient)
    my $cwd   = getcwd();
    my $found = 0;
    find(
        sub {
            if (-f $File::Find::name) {
                $found = 1;
                # File::Find does not really support exiting the search
                goto MRREPO_DONE_ANNEX_OBJECTS;
            }
        },
        $objects_dir
    );
  MRREPO_DONE_ANNEX_OBJECTS:
    chdir $cwd;
    return $found;
}

1;