#!/usr/bin/env perl
# Copyright (c) 2011 David Bremner
# License: same as notmuch

use strict;
use warnings;
use File::Path qw(remove_tree make_path);
use File::Temp qw(tempdir tempfile);
use File::Basename;
use Pod::Usage;

no encoding;

my $NMBGIT = $ENV{NMBGIT} || $ENV{HOME}.'/.nmbug';

$NMBGIT .= '/.git' if (-d $NMBGIT.'/.git');

my $TAGPREFIX = $ENV{NMBPREFIX} || 'notmuch::';

# magic hashes for git
my $EMPTYBLOB = 'e69de29bb2d1d6434b8b29ae775ad8c2e48c5391';
my $EMPTYTREE = '4b825dc642cb6eb9a060e54bf8d69288fbee4904';

# for encoding

my $ESCAPE_CHAR =	'%';
my $NO_ESCAPE =		'ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789'.
			'+-_@=.:,';
my $MUST_ENCODE =	qr{[^\Q$NO_ESCAPE\E]};
my $ESCAPED_RX =	qr{$ESCAPE_CHAR([A-Fa-f0-9]{2})};

my %command = (
	     archive	=> \&do_archive,
	     checkout	=> \&do_checkout,
	     commit	=> \&do_commit,
	     fetch	=> \&do_fetch,
	     help	=> \&do_help,
	     log	=> \&do_log,
	     merge	=> \&do_merge,
	     pull	=> \&do_pull,
	     push	=> \&do_push,
	     status	=> \&do_status,
	     );

my $subcommand = shift;

if (!exists $command{$subcommand}){
  usage ();
}

&{$command{$subcommand}}(@ARGV);

sub git_pipe {
  my $envref = (ref $_[0] eq 'HASH') ? shift : {};
  my $ioref  = (ref $_[0] eq 'ARRAY') ? shift : undef;
  my $dir = ($_[0] eq '-|' or $_[0] eq '|-') ? shift : undef;

  unshift @_, 'git';
  $envref->{GIT_DIR} ||= $NMBGIT;
  spawn ($envref, defined $ioref ? $ioref : (), defined $dir ? $dir : (), @_);
}

sub git {
  my $fh = git_pipe (@_);
  my $str = join ('', <$fh>);
  chomp($str);
  return $str;
}

sub spawn {
  my $envref = (ref $_[0] eq 'HASH') ? shift : {};
  my $ioref  = (ref $_[0] eq 'ARRAY') ? shift : undef;
  my $dir = ($_[0] eq '-|' or $_[0] eq '|-') ? shift : '-|';

  die unless @_;

  if (open my $child, $dir) {
    return $child;
  }
  # child
  while (my ($key, $value) = each %{$envref}) {
    $ENV{$key} = $value;
  }

  if (defined $ioref && $dir eq '-|') {
      open my $fh, '|-', @_ or die "open $dir @_: $!";
      foreach my $line (@{$ioref}) {
	print $fh $line, "\n";
      }
      exit 0;
    } else {
      if ($dir ne '|-') {
	open STDIN, '<', '/dev/null' or die "reopening stdin: $!"
      }
      exec @_;
      die "exec @_: $!";
    }
}


sub get_tags {
  my $prefix = shift;
  my @tags;

  my $fh = spawn ('-|', qw/notmuch search --output=tags/, "*")
    or die 'error dumping tags';

  while (<$fh>) {
    chomp ();
    push @tags, $_ if (m/^$prefix/);
  }
  return @tags;
}


sub do_archive {
  system ('git', "--git-dir=$NMBGIT", 'archive', 'HEAD');
}


sub is_committed {
  my $status = shift;
  return scalar (@{$status->{added}} ) + scalar (@{$status->{deleted}} )==0
}


sub do_commit {
  my @args = @_;

  my $status = compute_status ();

  if ( is_committed ($status) ){
    print "Nothing to commit\n";
    return;
  }

  my $index = read_tree ('HEAD');

  update_index ($index, $status);

  my $tree = git ( { GIT_INDEX_FILE => $index }, 'write-tree')
    or die 'no output from write-tree';

  my $parent = git ( 'rev-parse', 'HEAD'  )
    or die 'no output from rev-parse';

  my $commit = git ([ @args ], 'commit-tree', $tree, '-p', $parent)
    or die 'commit-tree';

  git ('update-ref', 'HEAD', $commit);

  unlink $index || die "unlink: $!";

}

sub read_tree {
  my $treeish = shift;
  my $index = $NMBGIT.'/nmbug.index';
  git ({GIT_INDEX_FILE => $index}, 'read-tree', $EMPTYTREE);
  git ({GIT_INDEX_FILE => $index}, 'read-tree', $treeish);
  return $index;
}

sub update_index {
  my $index = shift;
  my $status = shift;

  my $git = spawn ({ GIT_DIR => $NMBGIT, GIT_INDEX_FILE => $index },
		     '|-', qw/git update-index --index-info/)
    or die 'git update-index';

  foreach my $pair (@{$status->{deleted}}){
    index_tags_for_msg ($git, $pair->{id}, 'D', $pair->{tag})
  }

  foreach my $pair (@{$status->{added}}){
     index_tags_for_msg ($git, $pair->{id}, 'A', $pair->{tag})
  }
}

sub do_fetch {
  my $remote = shift || 'origin';

  git ('fetch', $remote);
}


sub notmuch {
  my @args = @_;
  system ('notmuch', @args) == 0 or die  "notmuch @args failed: $?"
}


sub index_tags {

  my $index = $NMBGIT.'/nmbug.index';

  my $query = join ' ', map ("tag:$_", get_tags ($TAGPREFIX));

  my $fh = spawn ('-|', qw/notmuch dump --/, $query)
    or die "notmuch dump: $!";

  git ('read-tree', $EMPTYTREE);
  my $git = spawn ({ GIT_DIR => $NMBGIT, GIT_INDEX_FILE => $index },
		     '|-', qw/git update-index --index-info/)
    or die 'git update-index';

  while (<$fh>) {
    m/ ( [^ ]* ) \s+ \( ([^\)]* ) \) /x || die 'syntax error in dump';
    my ($id,$rest) = ($1,$2);

    #strip prefixes before writing
    my @tags = grep { s/^$TAGPREFIX//; } split (' ', $rest);
    index_tags_for_msg ($git,$id, 'A', @tags);
  }

  close $git;
  return $index;
}

sub index_tags_for_msg {
  my $fh = shift;
  my $msgid = shift;
  my $mode = shift;

  my $hash = $EMPTYBLOB;
  my $blobmode = '100644';

  if ($mode eq 'D') {
    $blobmode = '0';
    $hash = '0000000000000000000000000000000000000000';
  }

  foreach my $tag (@_){
    my $tagpath = 'tags/' . encode_for_fs ($msgid)  . '/' . encode_for_fs ($tag);
    print $fh "$blobmode $hash\t$tagpath\n";
  }
}


sub do_checkout {
  do_sync (action => 'checkout');
}


sub do_sync {

  my %args = @_;

  my $status = compute_status ();
  my ($A_action, $D_action);

  if ($args{action} eq 'checkout') {
    $A_action = '-';
    $D_action = '+';
  } else {
    $A_action = '+';
    $D_action = '-';
  }

  foreach my $pair (@{$status->{added}}){

    notmuch ('tag', $A_action.$TAGPREFIX.$pair->{tag},
	     'id:'.$pair->{id});
  }

  foreach my $pair (@{$status->{deleted}}){
    notmuch ('tag', $D_action.$TAGPREFIX.$pair->{tag},
	     'id:'.$pair->{id});
  }

}


sub insist_committed {

  my $status=compute_status();
  if ( !is_committed ($status) ){
    print "Uncommitted changes to $TAGPREFIX* tags in notmuch

For a summary of changes, run 'nmbug status'
To save your changes,     run 'nmbug commit' before merging/pull
To discard your changes,  run 'nmbug checkout'
";
    exit (1);
  }

}


sub do_pull {
  my $remote = shift || 'origin';

  git ( 'fetch', $remote);

  do_merge ();
}


sub do_merge {
  insist_committed ();

  my $tempwork = tempdir ('/tmp/nmbug-merge.XXXXXX', CLEANUP => 1);

  git ( { GIT_WORK_TREE => $tempwork }, 'checkout', '-f', 'HEAD');

  git ( { GIT_WORK_TREE => $tempwork }, 'merge', 'FETCH_HEAD');

  do_checkout ();
}


sub do_log {
  # we don't want output trapping here, because we want the pager.
  system ( 'git', "--git-dir=$NMBGIT", 'log', '--name-status', @_);
}


sub do_push {
  my $remote = shift || 'origin';

  git ('push', $remote);
}


sub do_status {
  my $status = compute_status ();

  my %output = ();
  foreach my $pair (@{$status->{added}}){
    $output{$pair->{id}} ||= {};
    $output{$pair->{id}}{$pair->{tag}} = 'A'
  }

  foreach my $pair (@{$status->{deleted}}){
    $output{$pair->{id}} ||= {};
    $output{$pair->{id}}{$pair->{tag}} = 'D'
  }

  foreach my $pair (@{$status->{missing}}){
    $output{$pair->{id}} ||= {};
    $output{$pair->{id}}{$pair->{tag}} = 'U'
  }

  if (is_unmerged ()) {
    foreach my $pair (diff_refs ('A')){
      $output{$pair->{id}} ||= {};
      $output{$pair->{id}}{$pair->{tag}} ||= ' ';
      $output{$pair->{id}}{$pair->{tag}} .= 'a';
    }

    foreach my $pair (diff_refs ('D')){
      $output{$pair->{id}} ||= {};
      $output{$pair->{id}}{$pair->{tag}} ||= ' ';
      $output{$pair->{id}}{$pair->{tag}} .= 'd';
    }
  }

  foreach my $id (sort keys %output) {
    foreach my $tag (sort keys %{$output{$id}}) {
      printf "%s\t%s\t%s\n",$output{$id}{$tag},$id,$tag;
    }
  }
}


sub is_unmerged {

  return 0 if (! -f $NMBGIT.'/FETCH_HEAD');

  my $fetch_head = git ('rev-parse', 'FETCH_HEAD');
  my $base = git ( 'merge-base', 'HEAD', 'FETCH_HEAD');

  return ($base ne $fetch_head);

}

sub compute_status {
  my %args = @_;

  my @added;
  my @deleted;
  my @missing;

  my $index = index_tags ();

  my @maybe_deleted = diff_index ($index,'D');

  foreach my $pair (@maybe_deleted){

    my $id = $pair->{id};

    my $fh = spawn ('-|', qw/notmuch search --output=files/,"id:$id")
      or die "searching for $id";
    if (!<$fh>) {
      push @missing, $pair;
    } else {
      push @deleted, $pair;
    }
  }


  @added = diff_index ($index, 'A');

  unlink $index || die "unlink $index: $!";

  return { added => [@added], deleted => [@deleted], missing => [@missing] };
}


sub diff_index {
  my $index = shift;
  my $filter = shift;

  my $fh = git_pipe ({GIT_INDEX_FILE => $index},
		  qw/diff-index --cached/,
		 "--diff-filter=$filter", qw/--name-only HEAD/ );

  return unpack_diff_lines ($fh);
}


sub diff_refs {
  my $filter=shift;
  my $ref1 = shift || 'HEAD';
  my $ref2 = shift || 'FETCH_HEAD';

  my $fh= git_pipe ( 'diff', "--diff-filter=$filter", '--name-only',
		 $ref1, $ref2);

  return unpack_diff_lines ($fh);
}


sub unpack_diff_lines {
  my $fh=shift;

  my @found;
  while(<$fh>){
    chomp ();
    my ($id,$tag) = m|tags/ ([^/]+) / ([^/]+) |x;

    $id = decode_from_fs ($id);
    $tag = decode_from_fs ($tag);

    push @found, { id => $id, tag => $tag };
  }

  return @found;
}


sub encode_for_fs{
  my $str = shift;

  $str =~ s/($MUST_ENCODE)/"$ESCAPE_CHAR".sprintf ("%02x",ord ($1))/ge;
  return $str;
}


sub decode_from_fs{
  my $str = shift;

  $str =~ s/$ESCAPED_RX/ chr (hex ($1))/eg;

  return $str;

}


sub usage {
  pod2usage ();
  exit (1);
}


sub do_help {
  pod2usage ( -verbose => 2 );
  exit (0);
}

__END__

=head1 NAME

nmbug - manage notmuch tags about notmuch

=head1 SYNOPSIS

nmbug subcommand [options]

B<nmbug help> for more help

=head1 OPTIONS

=head2 Most common commands

=over 8

=item B<commit> [message]

Commit appropriately prefixed tags from the notmuch database to
git. Any extra arguments are used (one per line) as a commit message.

=item  B<push> [remote]

push local nmbug git state to remote repo

=item  B<pull> [remote]

pull (merge) remote repo changes to notmuch. B<pull> is equivalent to
B<fetch> followed by B<merge>.

=back

=head2 Other Useful Commands

=over 8

=item B<checkout>

Update the notmuch database from git. This is mainly useful to discard
your changes in notmuch relative to git.

=item B<fetch> [remote]

Fetch changes from the remote repo (see merge to bring those changes
into notmuch).

=item B<help> [subcommand]

print help [for subcommand]

=item B<log> [parameters]

A simple wrapper for git log. After running C<nmbug fetch>, you can
inspect the changes with C<nmbug log HEAD..FETCH_HEAD>

=item B<merge>

Merge changes from FETCH_HEAD into HEAD, and load the result into
notmuch.

=item  B<status>

Show pending updates in notmuch or git repo. See below for more
information about the output format.

=back

=head2 Less common commands

=over 8

=item B<archive>

Dump a tar archive (using git archive) of the current nmbug tag set.

=back

=head1 STATUS FORMAT

B<nmbug status> prints lines of the form

   ng Message-Id tag

where n is a single character representing notmuch database status

=over 8

=item B<A>

Tag is present in notmuch database, but not committed to nmbug
(equivalently, tag has been deleted in nmbug repo, e.g. by a pull, but
not restored to notmuch database).

=item B<D>

Tag is present in nmbug repo, but not restored to notmuch database
(equivalently, tag has been deleted in notmuch)

=item B<U>

Message is unknown (missing from local notmuch database)

=back

The second character (if present) represents a difference between remote
git and local. Typically C<nmbug fetch> needs to be run to update this.

=over 8


=item B<a>

Tag is present in remote, but not in local git.


=item B<d>

Tag is present in local git, but not in remote git.


=back

=head1 DUMP FORMAT

Each tag $tag for message with Message-Id $id is written to
an empty file

	tags/encode($id)/encode($tag)

The encoding preserves alphanumerics, and the characters "+-_@=.:,"
(not the quotes).  All other octets are replaced with '%' followed by
a two digit hex number.

=head1 ENVIRONMENT

B<NMBGIT> specifies the location of the git repository used by nmbug.
If not specified $HOME/.nmbug is used.

B<NMBPREFIX> specifies the prefix in the notmuch database for tags of
interest to nmbug. If not specified 'notmuch::' is used.