package Git::SVN::Fetcher;
use vars qw/@ISA $_ignore_regex $_preserve_empty_dirs $_placeholder_filename
            @deleted_gpath %added_placeholder $repo_id/;
use strict;
use warnings;
use SVN::Delta;
use Carp qw/croak/;
use File::Basename qw/dirname/;
use IO::File qw//;
use Git qw/command command_oneline command_noisy command_output_pipe
           command_input_pipe command_close_pipe
           command_bidi_pipe command_close_bidi_pipe/;
BEGIN {
        @ISA = qw(SVN::Delta::Editor);
}

# file baton members: path, mode_a, mode_b, pool, fh, blob, base
sub new {
        my ($class, $git_svn, $switch_path) = @_;
        my $self = SVN::Delta::Editor->new;
        bless $self, $class;
        if (exists $git_svn->{last_commit}) {
                $self->{c} = $git_svn->{last_commit};
                $self->{empty_symlinks} =
                                  _mark_empty_symlinks($git_svn, $switch_path);
        }

        # some options are read globally, but can be overridden locally
        # per [svn-remote "..."] section.  Command-line options will *NOT*
        # override options set in an [svn-remote "..."] section
        $repo_id = $git_svn->{repo_id};
        my $k = "svn-remote.$repo_id.ignore-paths";
        my $v = eval { command_oneline('config', '--get', $k) };
        $self->{ignore_regex} = $v;

        $k = "svn-remote.$repo_id.preserve-empty-dirs";
        $v = eval { command_oneline('config', '--get', '--bool', $k) };
        if ($v && $v eq 'true') {
                $_preserve_empty_dirs = 1;
                $k = "svn-remote.$repo_id.placeholder-filename";
                $v = eval { command_oneline('config', '--get', $k) };
                $_placeholder_filename = $v;
        }

        # Load the list of placeholder files added during previous invocations.
        $k = "svn-remote.$repo_id.added-placeholder";
        $v = eval { command_oneline('config', '--get-all', $k) };
        if ($_preserve_empty_dirs && $v) {
                # command() prints errors to stderr, so we only call it if
                # command_oneline() succeeded.
                my @v = command('config', '--get-all', $k);
                $added_placeholder{ dirname($_) } = $_ foreach @v;
        }

        $self->{empty} = {};
        $self->{dir_prop} = {};
        $self->{file_prop} = {};
        $self->{absent_dir} = {};
        $self->{absent_file} = {};
        require Git::IndexInfo;
        $self->{gii} = $git_svn->tmp_index_do(sub { Git::IndexInfo->new });
        $self->{pathnameencoding} = Git::config('svn.pathnameencoding');
        $self;
}

# this uses the Ra object, so it must be called before do_{switch,update},
# not inside them (when the Git::SVN::Fetcher object is passed) to
# do_{switch,update}
sub _mark_empty_symlinks {
        my ($git_svn, $switch_path) = @_;
        my $bool = Git::config_bool('svn.brokenSymlinkWorkaround');
        return {} if (!defined($bool)) || (defined($bool) && ! $bool);

        my %ret;
        my ($rev, $cmt) = $git_svn->last_rev_commit;
        return {} unless ($rev && $cmt);

        # allow the warning to be printed for each revision we fetch to
        # ensure the user sees it.  The user can also disable the workaround
        # on the repository even while git svn is running and the next
        # revision fetched will skip this expensive function.
        my $printed_warning;
        chomp(my $empty_blob = `git hash-object -t blob --stdin < /dev/null`);
        my ($ls, $ctx) = command_output_pipe(qw/ls-tree -r -z/, $cmt);
        local $/ = "\0";
        my $pfx = defined($switch_path) ? $switch_path : $git_svn->path;
        $pfx .= '/' if length($pfx);
        while (<$ls>) {
                chomp;
                s/\A100644 blob $empty_blob\t//o or next;
                unless ($printed_warning) {
                        print STDERR "Scanning for empty symlinks, ",
                                     "this may take a while if you have ",
                                     "many empty files\n",
                                     "You may disable this with `",
                                     "git config svn.brokenSymlinkWorkaround ",
                                     "false'.\n",
                                     "This may be done in a different ",
                                     "terminal without restarting ",
                                     "git svn\n";
                        $printed_warning = 1;
                }
                my $path = $_;
                my (undef, $props) =
                               $git_svn->ra->get_file($pfx.$path, $rev, undef);
                if ($props->{'svn:special'}) {
                        $ret{$path} = 1;
                }
        }
        command_close_pipe($ls, $ctx);
        \%ret;
}

# returns true if a given path is inside a ".git" directory
sub in_dot_git {
        $_[0] =~ m{(?:^|/)\.git(?:/|$)};
}

# return value: 0 -- don't ignore, 1 -- ignore
sub is_path_ignored {
        my ($self, $path) = @_;
        return 1 if in_dot_git($path);
        return 1 if defined($self->{ignore_regex}) &&
                    $path =~ m!$self->{ignore_regex}!;
        return 0 unless defined($_ignore_regex);
        return 1 if $path =~ m!$_ignore_regex!o;
        return 0;
}

sub set_path_strip {
        my ($self, $path) = @_;
        $self->{path_strip} = qr/^\Q$path\E(\/|$)/ if length $path;
}

sub open_root {
        { path => '' };
}

sub open_directory {
        my ($self, $path, $pb, $rev) = @_;
        { path => $path };
}

sub git_path {
        my ($self, $path) = @_;
        if (my $enc = $self->{pathnameencoding}) {
                require Encode;
                Encode::from_to($path, 'UTF-8', $enc);
        }
        if ($self->{path_strip}) {
                $path =~ s!$self->{path_strip}!! or
                  die "Failed to strip path '$path' ($self->{path_strip})\n";
        }
        $path;
}

sub delete_entry {
        my ($self, $path, $rev, $pb) = @_;
        return undef if $self->is_path_ignored($path);

        my $gpath = $self->git_path($path);
        return undef if ($gpath eq '');

        # remove entire directories.
        my ($tree) = (command('ls-tree', '-z', $self->{c}, "./$gpath")
                         =~ /\A040000 tree ([a-f\d]{40})\t\Q$gpath\E\0/);
        if ($tree) {
                my ($ls, $ctx) = command_output_pipe(qw/ls-tree
                                                     -r --name-only -z/,
                                                     $tree);
                local $/ = "\0";
                while (<$ls>) {
                        chomp;
                        my $rmpath = "$gpath/$_";
                        $self->{gii}->remove($rmpath);
                        print "\tD\t$rmpath\n" unless $::_q;
                }
                print "\tD\t$gpath/\n" unless $::_q;
                command_close_pipe($ls, $ctx);
        } else {
                $self->{gii}->remove($gpath);
                print "\tD\t$gpath\n" unless $::_q;
        }
        # Don't add to @deleted_gpath if we're deleting a placeholder file.
        push @deleted_gpath, $gpath unless $added_placeholder{dirname($path)};
        $self->{empty}->{$path} = 0;
        undef;
}

sub open_file {
        my ($self, $path, $pb, $rev) = @_;
        my ($mode, $blob);

        goto out if $self->is_path_ignored($path);

        my $gpath = $self->git_path($path);
        ($mode, $blob) = (command('ls-tree', '-z', $self->{c}, "./$gpath")
                             =~ /\A(\d{6}) blob ([a-f\d]{40})\t\Q$gpath\E\0/);
        unless (defined $mode && defined $blob) {
                die "$path was not found in commit $self->{c} (r$rev)\n";
        }
        if ($mode eq '100644' && $self->{empty_symlinks}->{$path}) {
                $mode = '120000';
        }
out:
        { path => $path, mode_a => $mode, mode_b => $mode, blob => $blob,
          pool => SVN::Pool->new, action => 'M' };
}

sub add_file {
        my ($self, $path, $pb, $cp_path, $cp_rev) = @_;
        my $mode;

        if (!$self->is_path_ignored($path)) {
                my ($dir, $file) = ($path =~ m#^(.*?)/?([^/]+)$#);
                delete $self->{empty}->{$dir};
                $mode = '100644';

                if ($added_placeholder{$dir}) {
                        # Remove our placeholder file, if we created one.
                        delete_entry($self, $added_placeholder{$dir})
                                unless $path eq $added_placeholder{$dir};
                        delete $added_placeholder{$dir}
                }
        }

        { path => $path, mode_a => $mode, mode_b => $mode,
          pool => SVN::Pool->new, action => 'A' };
}

sub add_directory {
        my ($self, $path, $cp_path, $cp_rev) = @_;
        goto out if $self->is_path_ignored($path);
        my $gpath = $self->git_path($path);
        if ($gpath eq '') {
                my ($ls, $ctx) = command_output_pipe(qw/ls-tree
                                                     -r --name-only -z/,
                                                     $self->{c});
                local $/ = "\0";
                while (<$ls>) {
                        chomp;
                        $self->{gii}->remove($_);
                        print "\tD\t$_\n" unless $::_q;
                        push @deleted_gpath, $gpath;
                }
                command_close_pipe($ls, $ctx);
                $self->{empty}->{$path} = 0;
        }
        my ($dir, $file) = ($path =~ m#^(.*?)/?([^/]+)$#);
        delete $self->{empty}->{$dir};
        $self->{empty}->{$path} = 1;

        if ($added_placeholder{$dir}) {
                # Remove our placeholder file, if we created one.
                delete_entry($self, $added_placeholder{$dir});
                delete $added_placeholder{$dir}
        }

out:
        { path => $path };
}

sub change_dir_prop {
        my ($self, $db, $prop, $value) = @_;
        return undef if $self->is_path_ignored($db->{path});
        $self->{dir_prop}->{$db->{path}} ||= {};
        $self->{dir_prop}->{$db->{path}}->{$prop} = $value;
        undef;
}

sub absent_directory {
        my ($self, $path, $pb) = @_;
        return undef if $self->is_path_ignored($path);
        $self->{absent_dir}->{$pb->{path}} ||= [];
        push @{$self->{absent_dir}->{$pb->{path}}}, $path;
        undef;
}

sub absent_file {
        my ($self, $path, $pb) = @_;
        return undef if $self->is_path_ignored($path);
        $self->{absent_file}->{$pb->{path}} ||= [];
        push @{$self->{absent_file}->{$pb->{path}}}, $path;
        undef;
}

sub change_file_prop {
        my ($self, $fb, $prop, $value) = @_;
        return undef if $self->is_path_ignored($fb->{path});
        if ($prop eq 'svn:executable') {
                if ($fb->{mode_b} != 120000) {
                        $fb->{mode_b} = defined $value ? 100755 : 100644;
                }
        } elsif ($prop eq 'svn:special') {
                $fb->{mode_b} = defined $value ? 120000 : 100644;
        } else {
                $self->{file_prop}->{$fb->{path}} ||= {};
                $self->{file_prop}->{$fb->{path}}->{$prop} = $value;
        }
        undef;
}

sub apply_textdelta {
        my ($self, $fb, $exp) = @_;
        return undef if $self->is_path_ignored($fb->{path});
        my $fh = $::_repository->temp_acquire('svn_delta');
        # $fh gets auto-closed() by SVN::TxDelta::apply(),
        # (but $base does not,) so dup() it for reading in close_file
        open my $dup, '<&', $fh or croak $!;
        my $base = $::_repository->temp_acquire('git_blob');

        if ($fb->{blob}) {
                my ($base_is_link, $size);

                if ($fb->{mode_a} eq '120000' &&
                    ! $self->{empty_symlinks}->{$fb->{path}}) {
                        print $base 'link ' or die "print $!\n";
                        $base_is_link = 1;
                }
        retry:
                $size = $::_repository->cat_blob($fb->{blob}, $base);
                die "Failed to read object $fb->{blob}" if ($size < 0);

                if (defined $exp) {
                        seek $base, 0, 0 or croak $!;
                        my $got = ::md5sum($base);
                        if ($got ne $exp) {
                                my $err = "Checksum mismatch: ".
                                       "$fb->{path} $fb->{blob}\n" .
                                       "expected: $exp\n" .
                                       "     got: $got\n";
                                if ($base_is_link) {
                                        warn $err,
                                             "Retrying... (possibly ",
                                             "a bad symlink from SVN)\n";
                                        $::_repository->temp_reset($base);
                                        $base_is_link = 0;
                                        goto retry;
                                }
                                die $err;
                        }
                }
        }
        seek $base, 0, 0 or croak $!;
        $fb->{fh} = $fh;
        $fb->{base} = $base;
        [ SVN::TxDelta::apply($base, $dup, undef, $fb->{path}, $fb->{pool}) ];
}

sub close_file {
        my ($self, $fb, $exp) = @_;
        return undef if $self->is_path_ignored($fb->{path});

        my $hash;
        my $path = $self->git_path($fb->{path});
        if (my $fh = $fb->{fh}) {
                if (defined $exp) {
                        seek($fh, 0, 0) or croak $!;
                        my $got = ::md5sum($fh);
                        if ($got ne $exp) {
                                die "Checksum mismatch: $path\n",
                                    "expected: $exp\n    got: $got\n";
                        }
                }
                if ($fb->{mode_b} == 120000) {
                        sysseek($fh, 0, 0) or croak $!;
                        my $rd = sysread($fh, my $buf, 5);

                        if (!defined $rd) {
                                croak "sysread: $!\n";
                        } elsif ($rd == 0) {
                                warn "$path has mode 120000",
                                     " but it points to nothing\n",
                                     "converting to an empty file with mode",
                                     " 100644\n";
                                $fb->{mode_b} = '100644';
                        } elsif ($buf ne 'link ') {
                                warn "$path has mode 120000",
                                     " but is not a link\n";
                        } else {
                                my $tmp_fh = $::_repository->temp_acquire(
                                        'svn_hash');
                                my $res;
                                while ($res = sysread($fh, my $str, 1024)) {
                                        my $out = syswrite($tmp_fh, $str, $res);
                                        defined($out) && $out == $res
                                                or croak("write ",
                                                        Git::temp_path($tmp_fh),
                                                        ": $!\n");
                                }
                                defined $res or croak $!;

                                ($fh, $tmp_fh) = ($tmp_fh, $fh);
                                Git::temp_release($tmp_fh, 1);
                        }
                }

                $hash = $::_repository->hash_and_insert_object(
                                Git::temp_path($fh));
                $hash =~ /^[a-f\d]{40}$/ or die "not a sha1: $hash\n";

                Git::temp_release($fb->{base}, 1);
                Git::temp_release($fh, 1);
        } else {
                $hash = $fb->{blob} or die "no blob information\n";
        }
        $fb->{pool}->clear;
        $self->{gii}->update($fb->{mode_b}, $hash, $path) or croak $!;
        print "\t$fb->{action}\t$path\n" if $fb->{action} && ! $::_q;
        undef;
}

sub abort_edit {
        my $self = shift;
        $self->{nr} = $self->{gii}->{nr};
        delete $self->{gii};
        $self->SUPER::abort_edit(@_);
}

sub close_edit {
        my $self = shift;

        if ($_preserve_empty_dirs) {
                my @empty_dirs;

                # Any entry flagged as empty that also has an associated
                # dir_prop represents a newly created empty directory.
                foreach my $i (keys %{$self->{empty}}) {
                        push @empty_dirs, $i if exists $self->{dir_prop}->{$i};
                }

                # Search for directories that have become empty due subsequent
                # file deletes.
                push @empty_dirs, $self->find_empty_directories();

                # Finally, add a placeholder file to each empty directory.
                $self->add_placeholder_file($_) foreach (@empty_dirs);

                $self->stash_placeholder_list();
        }

        $self->{git_commit_ok} = 1;
        $self->{nr} = $self->{gii}->{nr};
        delete $self->{gii};
        $self->SUPER::close_edit(@_);
}

sub find_empty_directories {
        my ($self) = @_;
        my @empty_dirs;
        my %dirs = map { dirname($_) => 1 } @deleted_gpath;

        foreach my $dir (sort keys %dirs) {
                next if $dir eq ".";

                # If there have been any additions to this directory, there is
                # no reason to check if it is empty.
                my $skip_added = 0;
                foreach my $t (qw/dir_prop file_prop/) {
                        foreach my $path (keys %{ $self->{$t} }) {
                                if (exists $self->{$t}->{dirname($path)}) {
                                        $skip_added = 1;
                                        last;
                                }
                        }
                        last if $skip_added;
                }
                next if $skip_added;

                # Use `git ls-tree` to get the filenames of this directory
                # that existed prior to this particular commit.
                my $ls = command('ls-tree', '-z', '--name-only',
                                 $self->{c}, "$dir/");
                my %files = map { $_ => 1 } split(/\0/, $ls);

                # Remove the filenames that were deleted during this commit.
                delete $files{$_} foreach (@deleted_gpath);

                # Report the directory if there are no filenames left.
                push @empty_dirs, $dir unless (scalar %files);
        }
        @empty_dirs;
}

sub add_placeholder_file {
        my ($self, $dir) = @_;
        my $path = "$dir/$_placeholder_filename";
        my $gpath = $self->git_path($path);

        my $fh = $::_repository->temp_acquire($gpath);
        my $hash = $::_repository->hash_and_insert_object(Git::temp_path($fh));
        Git::temp_release($fh, 1);
        $self->{gii}->update('100644', $hash, $gpath) or croak $!;

        # The directory should no longer be considered empty.
        delete $self->{empty}->{$dir} if exists $self->{empty}->{$dir};

        # Keep track of any placeholder files we create.
        $added_placeholder{$dir} = $path;
}

sub stash_placeholder_list {
        my ($self) = @_;
        my $k = "svn-remote.$repo_id.added-placeholder";
        my $v = eval { command_oneline('config', '--get-all', $k) };
        command_noisy('config', '--unset-all', $k) if $v;
        foreach (values %added_placeholder) {
                command_noisy('config', '--add', $k, $_);
        }
}

1;
__END__

=head1 NAME

Git::SVN::Fetcher - tree delta consumer for "git svn fetch"

=head1 SYNOPSIS

    use SVN::Core;
    use SVN::Ra;
    use Git::SVN;
    use Git::SVN::Fetcher;
    use Git;

    my $gs = Git::SVN->find_by_url($url);
    my $ra = SVN::Ra->new(url => $url);
    my $editor = Git::SVN::Fetcher->new($gs);
    my $reporter = $ra->do_update($SVN::Core::INVALID_REVNUM, '',
                                  1, $editor);
    $reporter->set_path('', $old_rev, 0);
    $reporter->finish_report;
    my $tree = $gs->tmp_index_do(sub { command_oneline('write-tree') });

    foreach my $path (keys %{$editor->{dir_prop}) {
        my $props = $editor->{dir_prop}{$path};
        foreach my $prop (keys %$props) {
            print "property $prop at $path changed to $props->{$prop}\n";
        }
    }
    foreach my $path (keys %{$editor->{empty}) {
        my $action = $editor->{empty}{$path} ? 'added' : 'removed';
        print "empty directory $path $action\n";
    }
    foreach my $path (keys %{$editor->{file_prop}) { ... }
    foreach my $parent (keys %{$editor->{absent_dir}}) {
        my @children = @{$editor->{abstent_dir}{$parent}};
        print "cannot fetch directory $parent/$_: not authorized?\n"
            foreach @children;
    }
    foreach my $parent (keys %{$editor->{absent_file}) { ... }

=head1 DESCRIPTION

This is a subclass of C<SVN::Delta::Editor>, which means it implements
callbacks to act as a consumer of Subversion tree deltas.  This
particular implementation of those callbacks is meant to store
information about the resulting content which B<git svn fetch> could
use to populate new commits and new entries for F<unhandled.log>.
More specifically:

=over

=item * Additions, removals, and modifications of files are propagated
to git-svn's index file F<$GIT_DIR/svn/$refname/index> using
B<git update-index>.

=item * Changes in Subversion path properties are recorded in the
C<dir_prop> and C<file_prop> fields (which are hashes).

=item * Addition and removal of empty directories are indicated by
entries with value 1 and 0 respectively in the C<empty> hash.

=item * Paths that are present but cannot be conveyed (presumably due
to permissions) are recorded in the C<absent_file> and
C<absent_dirs> hashes.  For each key, the corresponding value is
a list of paths under that directory that were present but
could not be conveyed.

=back

The interface is unstable.  Do not use this module unless you are
developing git-svn.

=head1 DEPENDENCIES

L<SVN::Delta> from the Subversion perl bindings,
the core L<Carp>, L<File::Basename>, and L<IO::File> modules,
and git's L<Git> helper module.

C<Git::SVN::Fetcher> has not been tested using callers other than
B<git-svn> itself.

=head1 SEE ALSO

L<SVN::Delta>,
L<Git::SVN::Editor>.

=head1 INCOMPATIBILITIES

None reported.

=head1 BUGS

None.