[public-inbox.git] / lib / PublicInbox / LEI.pm

# Copyright (C) 2020-2021 all contributors <meta@public-inbox.org>
# License: AGPL-3.0+ <https://www.gnu.org/licenses/agpl-3.0.txt>

# Backend for `lei' (local email interface).  Unlike the C10K-oriented
# PublicInbox::Daemon, this is designed exclusively to handle trusted
# local clients with read/write access to the FS and use as many
# system resources as the local user has access to.
package PublicInbox::LEI;
use strict;
use v5.10.1;
use parent qw(PublicInbox::DS PublicInbox::LeiExternal
        PublicInbox::LeiQuery);
use Getopt::Long ();
use Socket qw(AF_UNIX SOCK_SEQPACKET MSG_EOR pack_sockaddr_un);
use Errno qw(EPIPE EAGAIN EINTR ECONNREFUSED ENOENT ECONNRESET);
use Cwd qw(getcwd);
use POSIX qw(strftime);
use IO::Handle ();
use Fcntl qw(SEEK_SET);
use PublicInbox::Config;
use PublicInbox::Syscall qw(SFD_NONBLOCK EPOLLIN EPOLLET);
use PublicInbox::Sigfd;
use PublicInbox::DS qw(now dwaitpid);
use PublicInbox::Spawn qw(spawn popen_rd);
use PublicInbox::Lock;
use PublicInbox::Eml;
use Time::HiRes qw(stat); # ctime comparisons for config cache
use File::Path qw(mkpath);
use File::Spec;
our $quit = \&CORE::exit;
our ($current_lei, $errors_log, $listener, $oldset);
my ($recv_cmd, $send_cmd);
my $GLP = Getopt::Long::Parser->new;
$GLP->configure(qw(gnu_getopt no_ignore_case auto_abbrev));
my $GLP_PASS = Getopt::Long::Parser->new;
$GLP_PASS->configure(qw(gnu_getopt no_ignore_case auto_abbrev pass_through));

our %PATH2CFG; # persistent for socket daemon

# TBD: this is a documentation mechanism to show a subcommand
# (may) pass options through to another command:
sub pass_through { $GLP_PASS }

my $OPT;
sub opt_dash ($$) {
        my ($spec, $re_str) = @_; # 'limit|n=i', '([0-9]+)'
        my ($key) = ($spec =~ m/\A([a-z]+)/g);
        my $cb = sub { # Getopt::Long "<>" catch-all handler
                my ($arg) = @_;
                if ($arg =~ /\A-($re_str)\z/) {
                        $OPT->{$key} = $1;
                } elsif ($arg eq '--') { # "--" arg separator, ignore first
                        push @{$OPT->{-argv}}, $arg if $OPT->{'--'}++;
                # lone (single) dash is handled elsewhere
                } elsif (substr($arg, 0, 1) eq '-') {
                        if ($OPT->{'--'}) {
                                push @{$OPT->{-argv}}, $arg;
                        } else {
                                die "bad argument: $arg\n";
                        }
                } else {
                        push @{$OPT->{-argv}}, $arg;
                }
        };
        ($spec, '<>' => $cb, $GLP_PASS) # for Getopt::Long
}

# rel2abs preserves symlinks in parent, unlike abs_path
sub rel2abs {
        my ($self, $p) = @_;
        if (index($p, '/') == 0) { # already absolute
                $p =~ tr!/!/!s; # squeeze redundant slashes
                return $p;
        }
        my $pwd = $self->{env}->{PWD};
        my $cwd;
        if (defined $pwd) {
                my $xcwd = $self->{3} //
                        ($cwd = getcwd() // die "getcwd(PWD=$pwd): $!");
                if (my @st_pwd = stat($pwd)) {
                        my @st_cwd = stat($xcwd) or die "stat($xcwd): $!";
                        "@st_pwd[1,0]" eq "@st_cwd[1,0]" or
                                $self->{env}->{PWD} = $pwd = undef;
                } else { # PWD was invalid
                        $self->{env}->{PWD} = $pwd = undef;
                }
        }
        $pwd //= $self->{env}->{PWD} = $cwd // getcwd() // die "getcwd: $!";
        File::Spec->rel2abs($p, $pwd);
}

# abs_path resolves symlinks in parent iff all parents exist
sub abs_path { Cwd::abs_path($_[1]) // rel2abs(@_) }

sub share_path ($) { # $HOME/.local/share/lei/$FOO
        my ($self) = @_;
        rel2abs($self, ($self->{env}->{XDG_DATA_HOME} //
                ($self->{env}->{HOME} // '/nonexistent').'/.local/share')
                .'/lei');
}

sub store_path ($) { share_path($_[0]) . '/store' }

sub _config_path ($) {
        my ($self) = @_;
        rel2abs($self, ($self->{env}->{XDG_CONFIG_HOME} //
                ($self->{env}->{HOME} // '/nonexistent').'/.config')
                .'/lei/config');
}

sub cache_dir ($) {
        my ($self) = @_;
        rel2abs($self, ($self->{env}->{XDG_CACHE_HOME} //
                ($self->{env}->{HOME} // '/nonexistent').'/.cache')
                .'/lei');
}

sub ale {
        my ($self) = @_;
        $self->{ale} //= do {
                require PublicInbox::LeiALE;
                $self->_lei_cfg(1)->{ale} //= PublicInbox::LeiALE->new($self);
        };
}

sub index_opt {
        # TODO: drop underscore variants everywhere, they're undocumented
        qw(fsync|sync! jobs|j=i indexlevel|L=s compact
        max_size|max-size=s sequential_shard|sequential-shard
        batch_size|batch-size=s skip-docdata)
}

my @c_opt = qw(c=s@ C=s@ quiet|q);
my @lxs_opt = (qw(remote! local! external! include|I=s@ exclude=s@ only=s@
        import-remote! no-torsocks torsocks=s),
        PublicInbox::LeiQuery::curl_opt());

# we generate shell completion + help using %CMD and %OPTDESC,
# see lei__complete() and PublicInbox::LeiHelp
# command => [ positional_args, 1-line description, Getopt::Long option spec ]
our %CMD = ( # sorted in order of importance/use:
'q' => [ '--stdin|SEARCH_TERMS...', 'search for messages matching terms',
        'stdin|', # /|\z/ must be first for lone dash
        @lxs_opt,
        qw(save output|mfolder|o=s format|f=s dedupe|d=s threads|t+
        sort|s=s reverse|r offset=i pretty jobs|j=s globoff|g augment|a
        import-before! lock=s@ rsyncable alert=s@ mua=s verbose|v+
        color! mail-sync!), @c_opt, opt_dash('limit|n=i', '[0-9]+') ],

'up' => [ 'OUTPUT|--all', 'update saved search',
        qw(jobs|j=s lock=s@ alert=s@ mua=s verbose|v+ all:s), @c_opt ],

'lcat' => [ '--stdin|MSGID_OR_URL..', 'display local copy of message(s)',
        'stdin|', # /|\z/ must be first for lone dash
        # some of these options are ridiculous for lcat
        @lxs_opt, qw(output|mfolder|o=s format|f=s dedupe|d=s threads|t+
        sort|s=s reverse|r offset=i jobs|j=s globoff|g augment|a
        import-before! lock=s@ rsyncable alert=s@ mua=s verbose|v+
        color!), @c_opt, opt_dash('limit|n=i', '[0-9]+') ],

'blob' => [ 'OID', 'show a git blob, reconstructing from mail if necessary',
        qw(git-dir=s@ cwd! verbose|v+ mail! oid-a|A=s path-a|a=s path-b|b=s),
        @lxs_opt, @c_opt ],

'add-external' => [ 'LOCATION',
        'add/set priority of a publicinbox|extindex for extra matches',
        qw(boost=i mirror=s no-torsocks torsocks=s inbox-version=i
        verbose|v+), @c_opt, index_opt(),
        PublicInbox::LeiQuery::curl_opt() ],
'ls-external' => [ '[FILTER]', 'list publicinbox|extindex locations',
        qw(format|f=s z|0 globoff|g invert-match|v local remote), @c_opt ],
'ls-label' => [ '', 'list labels', qw(z|0 stats:s), @c_opt ],
'ls-mail-sync' => [ '[FILTER]', 'list mail sync folders',
                qw(z|0 globoff|g invert-match|v local remote), @c_opt ],
'forget-external' => [ 'LOCATION...|--prune',
        'exclude further results from a publicinbox|extindex',
        qw(prune), @c_opt ],

'ls-search' => [ '[PREFIX]', 'list saved search queries',
                qw(format|f=s pretty l ascii z|0), @c_opt ],
'forget-search' => [ 'OUTPUT', 'forget a saved search',
                qw(verbose|v+), @c_opt ],
'edit-search' => [ 'OUTPUT', "edit saved search via `git config --edit'",
                        @c_opt ],

'plonk' => [ '--threads|--from=IDENT',
        'exclude mail matching From: or threads from non-Message-ID searches',
        qw(stdin| threads|t from|f=s mid=s oid=s), @c_opt ],
'tag' => [ 'KEYWORDS...',
        'set/unset keywords and/or labels on message(s)',
        qw(stdin| in-format|F=s input|i=s@ oid=s@ mid=s@),
        qw(no-torsocks torsocks=s), PublicInbox::LeiQuery::curl_opt(), @c_opt,
        pass_through('-kw:foo for delete') ],
'forget' => [ '[--stdin|--oid=OID|--by-mid=MID]',
        "exclude message(s) on stdin from `q' search results",
        qw(stdin| oid=s exact by-mid|mid:s), @c_opt ],

'purge-mailsource' => [ 'LOCATION|--all',
        'remove imported messages from IMAP, Maildirs, and MH',
        qw(exact! all jobs:i indexed), @c_opt ],

'add-watch' => [ 'LOCATION', 'watch for new messages and flag changes',
        qw(import! kw! interval=s recursive|r
        exclude=s include=s), @c_opt ],
'ls-watch' => [ '[FILTER...]', 'list active watches with numbers and status',
                qw(format|f=s z), @c_opt ],
'pause-watch' => [ '[WATCH_NUMBER_OR_FILTER]', qw(all local remote), @c_opt ],
'resume-watch' => [ '[WATCH_NUMBER_OR_FILTER]', qw(all local remote), @c_opt ],
'forget-watch' => [ '{WATCH_NUMBER|--prune}', 'stop and forget a watch',
        qw(prune), @c_opt ],

'import' => [ 'LOCATION...|--stdin',
        'one-time import/update from URL or filesystem',
        qw(stdin| offset=i recursive|r exclude=s include|I=s
        lock=s@ in-format|F=s kw! verbose|v+ incremental! mail-sync!),
        qw(no-torsocks torsocks=s), PublicInbox::LeiQuery::curl_opt(), @c_opt ],
'convert' => [ 'LOCATION...|--stdin',
        'one-time conversion from URL or filesystem to another format',
        qw(stdin| in-format|F=s out-format|f=s output|mfolder|o=s lock=s@ kw!),
        qw(no-torsocks torsocks=s), PublicInbox::LeiQuery::curl_opt(), @c_opt ],
'p2q' => [ 'FILE|COMMIT_OID|--stdin',
        "use a patch to generate a query for `lei q --stdin'",
        qw(stdin| want|w=s@ uri debug), @c_opt ],
'config' => [ '[...]', sub {
                'git-config(1) wrapper for '._config_path($_[0]);
        }, qw(config-file|system|global|file|f=s), # for conflict detection
         qw(c=s@ C=s@), pass_through('git config') ],
'inspect' => [ 'ITEMS...', 'inspect lei/store and/or local external',
        qw(pretty ascii dir=s), @c_opt ],

'init' => [ '[DIRNAME]', sub {
        "initialize storage, default: ".store_path($_[0]);
        }, @c_opt ],
'daemon-kill' => [ '[-SIGNAL]', 'signal the lei-daemon',
        # "-C DIR" conflicts with -CHLD, here, and chdir makes no sense, here
        opt_dash('signal|s=s', '[0-9]+|(?:[A-Z][A-Z0-9]+)') ],
'daemon-pid' => [ '', 'show the PID of the lei-daemon' ],
'help' => [ '[SUBCOMMAND]', 'show help' ],

# XXX do we need this?
# 'git' => [ '[ANYTHING...]', 'git(1) wrapper', pass_through('git') ],

'reorder-local-store-and-break-history' => [ '[REFNAME]',
        'rewrite git history in an attempt to improve compression',
        qw(gc!), @c_opt ],

# internal commands are prefixed with '_'
'_complete' => [ '[...]', 'internal shell completion helper',
                pass_through('everything') ],
); # @CMD

# switch descriptions, try to keep consistent across commands
# $spec: Getopt::Long option specification
# $spec => [@ALLOWED_VALUES (default is first), $description],
# $spec => $description
# "$SUB_COMMAND TAB $spec" => as above
my $stdin_formats = [ 'MAIL_FORMAT|eml|mboxrd|mboxcl2|mboxcl|mboxo',
                        'specify message input format' ];
my $ls_format = [ 'OUT|plain|json|null', 'listing output format' ];

# we use \x{a0} (non-breaking SP) to avoid wrapping in PublicInbox::LeiHelp
my %OPTDESC = (
'help|h' => 'show this built-in help',
'c=s@' => [ 'NAME=VALUE', 'set config option' ],
'C=s@' => [ 'DIR', 'chdir to specify to directory' ],
'quiet|q' => 'be quiet',
'lock=s@' => [ 'METHOD|dotlock|fcntl|flock|none',
        'mbox(5) locking method(s) to use (default: fcntl,dotlock)' ],

'incremental!   import' => 'import already seen IMAP and NNTP articles',
'globoff|g' => "do not match locations using '*?' wildcards ".
                "and\xa0'[]'\x{a0}ranges",
'invert-match|v' => 'select non-matching lines',
'color!' => 'disable color (for --format=text)',
'verbose|v+' => 'be more verbose',
'external!' => 'do not use externals',
'mail!' => 'do not look in mail storage for OID',
'cwd!' => 'do not look in git repo of current working directory',
'oid-a|A=s' => 'pre-image OID',
'path-a|a=s' => 'pre-image pathname associated with OID',
'path-b|b=s' => 'post-image pathname associated with OID',
'git-dir=s@' => 'additional git repository to scan',
'proxy=s' => [ 'PROTO://HOST[:PORT]', # shared with curl(1)
        "proxy for (e.g. `socks5h://0:9050')" ],
'torsocks=s' => ['VAL|auto|no|yes',
                'whether or not to wrap git and curl commands with torsocks'],
'no-torsocks' => 'alias for --torsocks=no',
'save' =>  "save a search for `lei up'",
'import-remote!' => 'do not memoize remote messages into local store',

'type=s' => [ 'any|mid|git', 'disambiguate type' ],

'dedupe|d=s' => ['STRATEGY|content|oid|mid|none',
                'deduplication strategy'],
'threads|t+' =>
        'return all messages in the same threads as the actual match(es)',

'want|w=s@' => [ 'PREFIX|dfpost|dfn', # common ones in help...
                'search prefixes to extract (default: dfpost7)' ],

'alert=s@' => ['CMD,:WINCH,:bell,<any command>',
        'run command(s) or perform ops when done writing to output ' .
        '(default: ":WINCH,:bell" with --mua and Maildir/IMAP output, ' .
        'nothing otherwise)' ],

'augment|a' => 'augment --output destination instead of clobbering',

'output|mfolder|o=s' => [ 'MFOLDER',
        "destination (e.g.\xa0`/path/to/Maildir', ".
        "or\xa0`-'\x{a0}for\x{a0}stdout)" ],
'mua=s' => [ 'CMD',
        "MUA to run on --output Maildir or mbox (e.g.\xa0`mutt\xa0-f\xa0%f')" ],

'inbox-version=i' => [ 'NUM|1|2',
                'force a public-inbox version with --mirror'],
'mirror=s' => [ 'URL', 'mirror a public-inbox'],

# public-inbox-index options
'fsync!' => 'speed up indexing after --mirror, risk index corruption',
'compact' => 'run compact index after mirroring',
'indexlevel|L=s' => [ 'LEVEL|full|medium|basic',
        "indexlevel with --mirror (default: full)" ],
'max_size|max-size=s' => [ 'SIZE',
        'do not index messages larger than SIZE (default: infinity)' ],
'batch_size|batch-size=s' => [ 'SIZE',
        'flush changes to OS after given number of bytes (default: 1m)' ],
'sequential_shard|sequential-shard' =>
        'index Xapian shards sequentially for slow storage',
'skip-docdata' =>
        'drop compatibility w/ public-inbox <1.6 to save ~1.5% space',

'format|f=s     q' => [
        'OUT|maildir|mboxrd|mboxcl2|mboxcl|mboxo|html|json|jsonl|concatjson',
                'specify output format, default depends on --output'],
'exclude=s@     q' => [ 'LOCATION',
                'exclude specified external(s) from search' ],
'include|I=s@   q' => [ 'LOCATION',
                'include specified external(s) in search' ],
'only=s@        q' => [ 'LOCATION',
                'only use specified external(s) for search' ],
'jobs=s q' => [ '[SEARCH_JOBS][,WRITER_JOBS]',
                'control number of search and writer jobs' ],
'jobs|j=i       add-external' => 'set parallelism when indexing after --mirror',

'in-format|F=s' => $stdin_formats,
'format|f=s     ls-search' => ['OUT|json|jsonl|concatjson',
                        'listing output format' ],
'l      ls-search' => 'long listing format',
'format|f=s     ls-external' => $ls_format,

'limit|n=i@' => ['NUM', 'limit on number of matches (default: 10000)' ],
'offset=i' => ['OFF', 'search result offset (default: 0)'],

'sort|s=s' => [ 'VAL|received|relevance|docid',
                "order of results is `--output'-dependent"],
'reverse|r' => 'reverse search results', # like sort(1)

'boost=i' => 'increase/decrease priority of results (default: 0)',

'local' => 'limit operations to the local filesystem',
'local!' => 'exclude results from the local filesystem',
'remote' => 'limit operations to those requiring network access',
'remote!' => 'prevent operations requiring network access',

'all:s  up' => ['local', 'update all (local) saved searches' ],

'mid=s' => 'specify the Message-ID of a message',
'oid=s' => 'specify the git object ID of a message',

'recursive|r' => 'scan directories/mailboxes/newsgroups recursively',
'exclude=s' => 'exclude mailboxes/newsgroups based on pattern',
'include=s' => 'include mailboxes/newsgroups based on pattern',

'exact' => 'operate on exact header matches only',
'exact!' => 'rely on content match instead of exact header matches',

'by-mid|mid:s' => [ 'MID', 'match only by Message-ID, ignoring contents' ],

'kw!' => 'disable/enable importing keywords (aka "flags")',

# xargs, env, use "-0", git(1) uses "-z".  We support z|0 everywhere
'z|0' => 'use NUL \\0 instead of newline (CR) to delimit lines',

'signal|s=s' => [ 'SIG', 'signal to send lei-daemon (default: TERM)' ],
); # %OPTDESC

my %CONFIG_KEYS = (
        'leistore.dir' => 'top-level storage location',
);

my @WQ_KEYS = qw(lxs l2m wq1); # internal workers

sub _drop_wq {
        my ($self) = @_;
        for my $wq (grep(defined, delete(@$self{@WQ_KEYS}))) {
                if ($wq->wq_kill) {
                        $wq->wq_close(0, undef, $self);
                } elsif ($wq->wq_kill_old) {
                        $wq->wq_wait_old(undef, $self);
                }
                $wq->DESTROY;
        }
}

# pronounced "exit": x_it(1 << 8) => exit(1); x_it(13) => SIGPIPE
sub x_it ($$) {
        my ($self, $code) = @_;
        # make sure client sees stdout before exit
        $self->{1}->autoflush(1) if $self->{1};
        dump_and_clear_log();
        if (my $s = $self->{pkt_op_p} // $self->{sock}) {
                send($s, "x_it $code", MSG_EOR);
        } elsif ($self->{oneshot}) {
                # don't want to end up using $? from child processes
                _drop_wq($self);
                # cleanup anything that has tempfiles or open file handles
                %PATH2CFG = ();
                delete @$self{qw(ovv dedupe sto cfg)};
                if (my $signum = ($code & 127)) { # usually SIGPIPE (13)
                        $SIG{PIPE} = 'DEFAULT'; # $SIG{$signum} doesn't work
                        kill $signum, $$;
                        sleep(1) while 1; # wait for signal
                } else {
                        $quit->($code >> 8);
                }
        } # else ignore if client disconnected
}

sub err ($;@) {
        my $self = shift;
        my $err = $self->{2} // ($self->{pgr} // [])->[2] // *STDERR{GLOB};
        my @eor = (substr($_[-1]//'', -1, 1) eq "\n" ? () : ("\n"));
        print $err @_, @eor and return;
        my $old_err = delete $self->{2};
        close($old_err) if $! == EPIPE && $old_err;
        $err = $self->{2} = ($self->{pgr} // [])->[2] // *STDERR{GLOB};
        print $err @_, @eor or print STDERR @_, @eor;
}

sub qerr ($;@) { $_[0]->{opt}->{quiet} or err(shift, @_) }

sub fail_handler ($;$$) {
        my ($lei, $code, $io) = @_;
        close($io) if $io; # needed to avoid warnings on SIGPIPE
        _drop_wq($lei);
        x_it($lei, $code // (1 << 8));
}

sub sigpipe_handler { # handles SIGPIPE from @WQ_KEYS workers
        fail_handler($_[0], 13, delete $_[0]->{1});
}

# PublicInbox::OnDestroy callback for SIGINT to take out the entire pgid
sub sigint_reap {
        my ($pgid) = @_;
        dwaitpid($pgid) if kill('-INT', $pgid);
}

sub fail ($$;$) {
        my ($self, $buf, $exit_code) = @_;
        err($self, $buf) if defined $buf;
        # calls fail_handler:
        send($self->{pkt_op_p}, '!', MSG_EOR) if $self->{pkt_op_p};
        x_it($self, ($exit_code // 1) << 8);
        undef;
}

sub out ($;@) {
        my $self = shift;
        return if print { $self->{1} // return } @_; # likely
        return note_sigpipe($self, 1) if $! == EPIPE;
        my $err = "error writing to output: $!";
        delete $self->{1};
        fail($self, $err);
}

sub puts ($;@) { out(shift, map { "$_\n" } @_) }

sub child_error { # passes non-fatal curl exit codes to user
        my ($self, $child_error, $msg) = @_; # child_error is $?
        $self->err($msg) if $msg;
        if (my $s = $self->{pkt_op_p} // $self->{sock}) {
                # send to the parent lei-daemon or to lei(1) client
                send($s, "child_error $child_error", MSG_EOR);
        } elsif (!$PublicInbox::DS::in_loop) {
                $self->{child_error} = $child_error;
        } # else noop if client disconnected
}

sub note_sigpipe { # triggers sigpipe_handler
        my ($self, $fd) = @_;
        close(delete($self->{$fd})); # explicit close silences Perl warning
        send($self->{pkt_op_p}, '|', MSG_EOR) if $self->{pkt_op_p};
        x_it($self, 13);
}

sub _lei_atfork_child {
        my ($self, $persist) = @_;
        # we need to explicitly close things which are on stack
        if ($persist) {
                chdir '/' or die "chdir(/): $!";
                close($_) for (grep(defined, delete @$self{qw(0 1 2 sock)}));
                if (my $cfg = $self->{cfg}) {
                        delete $cfg->{-lei_store};
                }
        } else { # worker, Net::NNTP (Net::Cmd) uses STDERR directly
                open STDERR, '+>&='.fileno($self->{2}) or warn "open $!";
                STDERR->autoflush(1);
        }
        close($_) for (grep(defined, delete @$self{qw(3 old_1 au_done)}));
        if (my $op_c = delete $self->{pkt_op_c}) {
                close(delete $op_c->{sock});
        }
        if (my $pgr = delete $self->{pgr}) {
                close($_) for (@$pgr[1,2]);
        }
        close $listener if $listener;
        undef $listener;
        %PATH2CFG = ();
        undef $errors_log;
        $quit = \&CORE::exit;
        $self->{-eml_noisy} or # only "lei import" sets this atm
                $SIG{__WARN__} = PublicInbox::Eml::warn_ignore_cb();
        $current_lei = $persist ? undef : $self; # for SIG{__WARN__}
}

sub _delete_pkt_op { # OnDestroy callback to prevent leaks on die
        my ($self) = @_;
        if (my $op = delete $self->{pkt_op_c}) { # in case of die
                $op->close; # PublicInbox::PktOp::close
        }
        my $unclosed_after_die = delete($self->{pkt_op_p}) or return;
        close $unclosed_after_die;
}

sub pkt_op_pair {
        my ($self) = @_;
        require PublicInbox::OnDestroy;
        require PublicInbox::PktOp;
        my $end = PublicInbox::OnDestroy->new($$, \&_delete_pkt_op, $self);
        @$self{qw(pkt_op_c pkt_op_p)} = PublicInbox::PktOp->pair;
        $end;
}

sub workers_start {
        my ($lei, $wq, $jobs, $ops) = @_;
        $ops = {
                '!' => [ \&fail_handler, $lei ],
                '|' => [ \&sigpipe_handler, $lei ],
                'x_it' => [ \&x_it, $lei ],
                'child_error' => [ \&child_error, $lei ],
                ($ops ? %$ops : ()),
        };
        $ops->{''} //= [ $wq->can('_lei_wq_eof') || \&wq_eof, $lei ];
        my $end = $lei->pkt_op_pair;
        my $ident = $wq->{-wq_ident} // "lei-$lei->{cmd} worker";
        $wq->wq_workers_start($ident, $jobs, $lei->oldset, { lei => $lei });
        delete $lei->{pkt_op_p};
        my $op_c = delete $lei->{pkt_op_c};
        @$end = ();
        $lei->event_step_init;
        ($op_c, $ops);
}

sub _help {
        require PublicInbox::LeiHelp;
        PublicInbox::LeiHelp::call($_[0], $_[1], \%CMD, \%OPTDESC);
}

sub optparse ($$$) {
        my ($self, $cmd, $argv) = @_;
        # allow _complete --help to complete, not show help
        return 1 if substr($cmd, 0, 1) eq '_';
        $self->{cmd} = $cmd;
        $OPT = $self->{opt} //= {};
        my $info = $CMD{$cmd} // [ '[...]' ];
        my ($proto, undef, @spec) = @$info;
        my $glp = ref($spec[-1]) eq ref($GLP) ? pop(@spec) : $GLP;
        push @spec, qw(help|h);
        my $lone_dash;
        if ($spec[0] =~ s/\|\z//s) { # "stdin|" or "clear|" allows "-" alias
                $lone_dash = $spec[0];
                $OPT->{$spec[0]} = \(my $var);
                push @spec, '' => \$var;
        }
        $glp->getoptionsfromarray($argv, $OPT, @spec) or
                return _help($self, "bad arguments or options for $cmd");
        return _help($self) if $OPT->{help};

        push @$argv, @{$OPT->{-argv}} if defined($OPT->{-argv});

        # "-" aliases "stdin" or "clear"
        $OPT->{$lone_dash} = ${$OPT->{$lone_dash}} if defined $lone_dash;

        my $i = 0;
        my $POS_ARG = '[A-Z][A-Z0-9_]+';
        my ($err, $inf);
        my @args = split(/ /, $proto);
        for my $var (@args) {
                if ($var =~ /\A$POS_ARG\.\.\.\z/o) { # >= 1 args;
                        $inf = defined($argv->[$i]) and last;
                        $var =~ s/\.\.\.\z//;
                        $err = "$var not supplied";
                } elsif ($var =~ /\A$POS_ARG\z/o) { # required arg at $i
                        $argv->[$i++] // ($err = "$var not supplied");
                } elsif ($var =~ /\.\.\.\]\z/) { # optional args start
                        $inf = 1;
                        last;
                } elsif ($var =~ /\A\[-?$POS_ARG\]\z/) { # one optional arg
                        $i++;
                } elsif ($var =~ /\A.+?\|/) { # required FOO|--stdin
                        $inf = 1 if index($var, '...') > 0;
                        my @or = split(/\|/, $var);
                        my $ok;
                        for my $o (@or) {
                                if ($o =~ /\A--([a-z0-9\-]+)/) {
                                        $ok = defined($OPT->{$1});
                                        last if $ok;
                                } elsif (defined($argv->[$i])) {
                                        $ok = 1;
                                        $i++;
                                        last;
                                } # else continue looping
                        }
                        last if $ok;
                        my $last = pop @or;
                        $err = join(', ', @or) . " or $last must be set";
                } else {
                        warn "BUG: can't parse `$var' in $proto";
                }
                last if $err;
        }
        if (!$inf && scalar(@$argv) > scalar(@args)) {
                $err //= 'too many arguments';
        }
        $err ? fail($self, "usage: lei $cmd $proto\nE: $err") : 1;
}

sub _tmp_cfg { # for lei -c <name>=<value> ...
        my ($self) = @_;
        my $cfg = _lei_cfg($self, 1);
        require File::Temp;
        my $ft = File::Temp->new(TEMPLATE => 'lei_cfg-XXXX', TMPDIR => 1);
        my $tmp = { '-f' => $ft->filename, -tmp => $ft };
        $ft->autoflush(1);
        print $ft <<EOM or return fail($self, "$tmp->{-f}: $!");
[include]
        path = $cfg->{-f}
EOM
        $tmp = $self->{cfg} = bless { %$cfg, %$tmp }, ref($cfg);
        for (@{$self->{opt}->{c}}) {
                /\A([^=\.]+\.[^=]+)(?:=(.*))?\z/ or return fail($self, <<EOM);
`-c $_' is not of the form -c <name>=<value>'
EOM
                my $name = $1;
                my $value = $2 // 1;
                _config($self, '--add', $name, $value);
                if (defined(my $v = $tmp->{$name})) {
                        if (ref($v) eq 'ARRAY') {
                                push @$v, $value;
                        } else {
                                $tmp->{$name} = [ $v, $value ];
                        }
                } else {
                        $tmp->{$name} = $value;
                }
        }
}

sub lazy_cb ($$$) {
        my ($self, $cmd, $pfx) = @_;
        my $ucmd = $cmd;
        $ucmd =~ tr/-/_/;
        my $cb;
        $cb = $self->can($pfx.$ucmd) and return $cb;
        my $base = $ucmd;
        $base =~ s/_([a-z])/\u$1/g;
        my $pkg = "PublicInbox::Lei\u$base";
        ($INC{"PublicInbox/Lei\u$base.pm"} // eval("require $pkg")) ?
                $pkg->can($pfx.$ucmd) : undef;
}

sub dispatch {
        my ($self, $cmd, @argv) = @_;
        local $current_lei = $self; # for __WARN__
        $self->{2}->autoflush(1); # keep stdout buffered until x_it|DESTROY
        dump_and_clear_log("from previous run\n");
        return _help($self, 'no command given') unless defined($cmd);
        # do not support Getopt bundling for this
        while ($cmd eq '-C' || $cmd eq '-c') {
                my $v = shift(@argv) // return fail($self, $cmd eq '-C' ?
                                        '-C DIRECTORY' : '-c <name>=<value>');
                push @{$self->{opt}->{substr($cmd, 1, 1)}}, $v;
                $cmd = shift(@argv) // return _help($self, 'no command given');
        }
        if (my $cb = lazy_cb(__PACKAGE__, $cmd, 'lei_')) {
                optparse($self, $cmd, \@argv) or return;
                $self->{opt}->{c} and (_tmp_cfg($self) // return);
                if (my $chdir = $self->{opt}->{C}) {
                        for my $d (@$chdir) {
                                next if $d eq ''; # same as git(1)
                                chdir $d or return fail($self, "cd $d: $!");
                        }
                        if (delete $self->{3}) { # update cwd for rel2abs
                                opendir my $dh, '.' or
                                        return fail($self, "opendir . $!");
                                $self->{3} = $dh;
                        }
                }
                $cb->($self, @argv);
        } elsif (grep(/\A-/, $cmd, @argv)) { # --help or -h only
                $GLP->getoptionsfromarray([$cmd, @argv], {}, qw(help|h C=s@))
                        or return _help($self, 'bad arguments or options');
                _help($self);
        } else {
                fail($self, "`$cmd' is not an lei command");
        }
}

sub _lei_cfg ($;$) {
        my ($self, $creat) = @_;
        return $self->{cfg} if $self->{cfg};
        my $f = _config_path($self);
        my @st = stat($f);
        my $cur_st = @st ? pack('dd', $st[10], $st[7]) : ''; # 10:ctime, 7:size
        my ($sto, $sto_dir);
        if (my $cfg = $PATH2CFG{$f}) { # reuse existing object in common case
                return ($self->{cfg} = $cfg) if $cur_st eq $cfg->{-st};
                ($sto, $sto_dir) = @$cfg{qw(-lei_store leistore.dir)};
        }
        if (!@st) {
                unless ($creat) {
                        delete $self->{cfg};
                        return bless {}, 'PublicInbox::Config';
                }
                my (undef, $cfg_dir, undef) = File::Spec->splitpath($f);
                -d $cfg_dir or mkpath($cfg_dir) or die "mkpath($cfg_dir): $!\n";
                open my $fh, '>>', $f or die "open($f): $!\n";
                @st = stat($fh) or die "fstat($f): $!\n";
                $cur_st = pack('dd', $st[10], $st[7]);
                qerr($self, "# $f created") if $self->{cmd} ne 'config';
        }
        my $cfg = PublicInbox::Config->git_config_dump($f);
        $cfg->{-st} = $cur_st;
        $cfg->{'-f'} = $f;
        if ($sto && File::Spec->canonpath($sto_dir // store_path($self))
                        eq File::Spec->canonpath($cfg->{'leistore.dir'} //
                                                store_path($self))) {
                $cfg->{-lei_store} = $sto;
        }
        if (scalar(keys %PATH2CFG) > 5) {
                # FIXME: use inotify/EVFILT_VNODE to detect unlinked configs
                for my $k (keys %PATH2CFG) {
                        delete($PATH2CFG{$k}) unless -f $k
                }
        }
        $self->{cfg} = $PATH2CFG{$f} = $cfg;
}

sub _lei_store ($;$) {
        my ($self, $creat) = @_;
        my $cfg = _lei_cfg($self, $creat);
        $cfg->{-lei_store} //= do {
                require PublicInbox::LeiStore;
                my $dir = $cfg->{'leistore.dir'} // store_path($self);
                return unless $creat || -d $dir;
                PublicInbox::LeiStore->new($dir, { creat => $creat });
        };
}

sub _config {
        my ($self, @argv) = @_;
        my %env = (%{$self->{env}}, GIT_CONFIG => undef);
        my $cfg = _lei_cfg($self, 1);
        my $cmd = [ qw(git config -f), $cfg->{'-f'}, @argv ];
        my %rdr = map { $_ => $self->{$_} } (0..2);
        waitpid(spawn($cmd, \%env, \%rdr), 0);
}

sub lei_config {
        my ($self, @argv) = @_;
        $self->{opt}->{'config-file'} and return fail $self,
                "config file switches not supported by `lei config'";
        _config(@_);
        x_it($self, $?) if $?;
}

sub lei_daemon_pid { puts shift, $$ }

sub lei_daemon_kill {
        my ($self) = @_;
        my $sig = $self->{opt}->{signal} // 'TERM';
        kill($sig, $$) or fail($self, "kill($sig, $$): $!");
}

# Shell completion helper.  Used by lei-completion.bash and hopefully
# other shells.  Try to do as much here as possible to avoid redundancy
# and improve maintainability.
sub lei__complete {
        my ($self, @argv) = @_; # argv = qw(lei and any other args...)
        shift @argv; # ignore "lei", the entire command is sent
        @argv or return puts $self, grep(!/^_/, keys %CMD), qw(--help -h -C);
        my $cmd = shift @argv;
        my $info = $CMD{$cmd} // do { # filter matching commands
                @argv or puts $self, grep(/\A\Q$cmd\E/, keys %CMD);
                return;
        };
        my ($proto, undef, @spec) = @$info;
        my $cur = pop @argv;
        my $re = defined($cur) ? qr/\A\Q$cur\E/ : qr/./;
        if (substr(my $_cur = $cur // '-', 0, 1) eq '-') { # --switches
                # gross special case since the only git-config options
                # Consider moving to a table if we need more special cases
                # we use Getopt::Long for are the ones we reject, so these
                # are the ones we don't reject:
                if ($cmd eq 'config') {
                        puts $self, grep(/$re/, keys %CONFIG_KEYS);
                        @spec = qw(add z|null get get-all unset unset-all
                                replace-all get-urlmatch
                                remove-section rename-section
                                name-only list|l edit|e
                                get-color-name get-colorbool);
                        # fall-through
                }
                # generate short/long names from Getopt::Long specs
                puts $self, grep(/$re/, qw(--help -h -C), map {
                        if (s/[:=].+\z//) { # req/optional args, e.g output|o=i
                        } elsif (s/\+\z//) { # verbose|v+
                        } elsif (s/!\z//) {
                                # negation: mail! => no-mail|mail
                                s/([\w\-]+)/$1|no-$1/g
                        }
                        map {
                                my $x = length > 1 ? "--$_" : "-$_";
                                $x eq $_cur ? () : $x;
                        } grep(!/_/, split(/\|/, $_, -1)) # help|h
                } grep { $OPTDESC{"$_\t$cmd"} || $OPTDESC{$_} } @spec);
        } elsif ($cmd eq 'config' && !@argv && !$CONFIG_KEYS{$cur}) {
                puts $self, grep(/$re/, keys %CONFIG_KEYS);
        }

        # switch args (e.g. lei q -f mbox<TAB>)
        if (($argv[-1] // $cur // '') =~ /\A--?([\w\-]+)\z/) {
                my $opt = quotemeta $1;
                puts $self, map {
                        my $v = $OPTDESC{$_};
                        my @v = ref($v) ? split(/\|/, $v->[0]) : ();
                        # get rid of ALL CAPS placeholder (e.g "OUT")
                        # (TODO: completion for external paths)
                        shift(@v) if scalar(@v) && uc($v[0]) eq $v[0];
                        @v;
                } grep(/\A(?:[\w-]+\|)*$opt\b.*?(?:\t$cmd)?\z/, keys %OPTDESC);
        }
        if (my $cb = lazy_cb($self, $cmd, '_complete_')) {
                puts $self, $cb->($self, @argv, $cur ? ($cur) : ());
        }
        # TODO: URLs, pathnames, OIDs, MIDs, etc...  See optparse() for
        # proto parsing.
}

sub exec_buf ($$) {
        my ($argv, $env) = @_;
        my $argc = scalar @$argv;
        my $buf = 'exec '.join("\0", scalar(@$argv), @$argv);
        while (my ($k, $v) = each %$env) { $buf .= "\0$k=$v" };
        $buf;
}

sub start_mua {
        my ($self) = @_;
        my $mua = $self->{opt}->{mua} // return;
        my $mfolder = $self->{ovv}->{dst};
        my (@cmd, $replaced);
        if ($mua =~ /\A(?:mutt|mailx|mail|neomutt)\z/) {
                @cmd = ($mua, '-f');
        # TODO: help wanted: other common FOSS MUAs
        } else {
                require Text::ParseWords;
                @cmd = Text::ParseWords::shellwords($mua);
                # mutt uses '%f' for open-hook with compressed mbox, we follow
                @cmd = map { $_ eq '%f' ? ($replaced = $mfolder) : $_ } @cmd;
        }
        push @cmd, $mfolder unless defined($replaced);
        if ($self->{sock}) { # lei(1) client process runs it
                # restore terminal: echo $query | lei q -stdin --mua=...
                my $io = [];
                $io->[0] = $self->{1} if $self->{opt}->{stdin} && -t $self->{1};
                send_exec_cmd($self, $io, \@cmd, {});
        } elsif ($self->{oneshot}) {
                my $pid = fork // die "fork: $!";
                if ($pid > 0) { # original process
                        if ($self->{opt}->{stdin} && -t STDOUT) {
                                open STDIN, '+<&', \*STDOUT or die "dup2: $!";
                        }
                        exec(@cmd);
                        warn "exec @cmd: $!\n";
                        POSIX::_exit(1);
                }
                POSIX::setsid() > 0 or die "setsid: $!";
        }
        if ($self->{lxs} && $self->{au_done}) { # kick wait_startq
                syswrite($self->{au_done}, 'q' x ($self->{lxs}->{jobs} // 0));
        }
        return unless -t $self->{2}; # XXX how to determine non-TUI MUAs?
        $self->{opt}->{quiet} = 1;
        delete $self->{-progress};
        delete $self->{opt}->{verbose};
}

sub send_exec_cmd { # tell script/lei to execute a command
        my ($self, $io, $cmd, $env) = @_;
        my $sock = $self->{sock} // die 'lei client gone';
        my $fds = [ map { fileno($_) } @$io ];
        $send_cmd->($sock, $fds, exec_buf($cmd, $env), MSG_EOR);
}

sub poke_mua { # forces terminal MUAs to wake up and hopefully notice new mail
        my ($self) = @_;
        my $alerts = $self->{opt}->{alert} // return;
        while (my $op = shift(@$alerts)) {
                if ($op eq ':WINCH') {
                        # hit the process group that started the MUA
                        if ($self->{sock}) {
                                send($self->{sock}, '-WINCH', MSG_EOR);
                        } elsif ($self->{oneshot}) {
                                kill('-WINCH', $$);
                        }
                } elsif ($op eq ':bell') {
                        out($self, "\a");
                } elsif ($op =~ /(?<!\\),/) { # bare ',' (not ',,')
                        push @$alerts, split(/(?<!\\),/, $op);
                } elsif ($op =~ m!\A([/a-z0-9A-Z].+)!) {
                        my $cmd = $1; # run an arbitrary command
                        require Text::ParseWords;
                        $cmd = [ Text::ParseWords::shellwords($cmd) ];
                        if (my $s = $self->{sock}) {
                                send($s, exec_buf($cmd, {}), MSG_EOR);
                        } elsif ($self->{oneshot}) {
                                $self->{"pid.$self.$$"}->{spawn($cmd)} = $cmd;
                        }
                } else {
                        err($self, "W: unsupported --alert=$op"); # non-fatal
                }
        }
}

my %path_to_fd = ('/dev/stdin' => 0, '/dev/stdout' => 1, '/dev/stderr' => 2);
$path_to_fd{"/dev/fd/$_"} = $_ for (0..2);

# this also normalizes the path
sub path_to_fd {
        my ($self, $path) = @_;
        $path = rel2abs($self, $path);
        $path =~ tr!/!/!s;
        $path_to_fd{$path} // (
                ($path =~ m!\A/(?:dev|proc/self)/fd/[0-9]+\z!) ?
                        fail($self, "cannot open $path from daemon") : -1
        );
}

# caller needs to "-t $self->{1}" to check if tty
sub start_pager {
        my ($self) = @_;
        my $fh = popen_rd([qw(git var GIT_PAGER)]);
        chomp(my $pager = <$fh> // '');
        close($fh) or warn "`git var PAGER' error: \$?=$?";
        return if $pager eq 'cat' || $pager eq '';
        my $new_env = { LESS => 'FRX', LV => '-c' };
        $new_env->{MORE} = 'FRX' if $^O eq 'freebsd';
        pipe(my ($r, $wpager)) or return warn "pipe: $!";
        my $rdr = { 0 => $r, 1 => $self->{1}, 2 => $self->{2} };
        my $pgr = [ undef, @$rdr{1, 2} ];
        my $env = $self->{env};
        if ($self->{sock}) { # lei(1) process runs it
                delete @$new_env{keys %$env}; # only set iff unset
                send_exec_cmd($self, [ @$rdr{0..2} ], [$pager], $new_env);
        } elsif ($self->{oneshot}) {
                my $cmd = [$pager];
                $self->{"pid.$self.$$"}->{spawn($cmd, $new_env, $rdr)} = $cmd;
        } else {
                die 'BUG: start_pager w/o socket';
        }
        $self->{1} = $wpager;
        $self->{2} = $wpager if -t $self->{2};
        $env->{GIT_PAGER_IN_USE} = 'true'; # we may spawn git
        $self->{pgr} = $pgr;
}

sub stop_pager {
        my ($self) = @_;
        my $pgr = delete($self->{pgr}) or return;
        $self->{2} = $pgr->[2];
        # do not restore original stdout, just close it so we error out
        close(delete($self->{1})) if $self->{1};
}

sub accept_dispatch { # Listener {post_accept} callback
        my ($sock) = @_; # ignore other
        $sock->autoflush(1);
        my $self = bless { sock => $sock }, __PACKAGE__;
        vec(my $rvec = '', fileno($sock), 1) = 1;
        select($rvec, undef, undef, 60) or
                return send($sock, 'timed out waiting to recv FDs', MSG_EOR);
        # (4096 * 33) >MAX_ARG_STRLEN
        my @fds = $recv_cmd->($sock, my $buf, 4096 * 33) or return; # EOF
        if (!defined($fds[0])) {
                warn(my $msg = "recv_cmd failed: $!");
                return send($sock, $msg, MSG_EOR);
        } else {
                my $i = 0;
                for my $fd (@fds) {
                        open($self->{$i++}, '+<&=', $fd) and next;
                        send($sock, "open(+<&=$fd) (FD=$i): $!", MSG_EOR);
                }
                $i == 4 or return send($sock, 'not enough FDs='.($i-1), MSG_EOR)
        }
        # $ENV_STR = join('', map { "\0$_=$ENV{$_}" } keys %ENV);
        # $buf = "$argc\0".join("\0", @ARGV).$ENV_STR."\0\0";
        substr($buf, -2, 2, '') eq "\0\0" or  # s/\0\0\z//
                return send($sock, 'request command truncated', MSG_EOR);
        my ($argc, @argv) = split(/\0/, $buf, -1);
        undef $buf;
        my %env = map { split(/=/, $_, 2) } splice(@argv, $argc);
        if (chdir($self->{3})) {
                local %ENV = %env;
                $self->{env} = \%env;
                eval { dispatch($self, @argv) };
                send($sock, $@, MSG_EOR) if $@;
        } else {
                send($sock, "fchdir: $!", MSG_EOR); # implicit close
        }
}

sub dclose {
        my ($self) = @_;
        delete $self->{-progress};
        _drop_wq($self);
        close(delete $self->{1}) if $self->{1}; # may reap_compress
        $self->close if $self->{-event_init_done}; # PublicInbox::DS::close
}

# for long-running results
sub event_step {
        my ($self) = @_;
        local %ENV = %{$self->{env}};
        my $sock = $self->{sock};
        local $current_lei = $self;
        eval {
                while (my @fds = $recv_cmd->($sock, my $buf, 4096)) {
                        if (scalar(@fds) == 1 && !defined($fds[0])) {
                                return if $! == EAGAIN;
                                next if $! == EINTR;
                                last if $! == ECONNRESET;
                                die "recvmsg: $!";
                        }
                        for my $fd (@fds) {
                                open my $rfh, '+<&=', $fd;
                        }
                        die "unrecognized client signal: $buf";
                }
                dclose($self);
        };
        if (my $err = $@) {
                eval { $self->fail($err) };
                dclose($self);
        }
}

sub event_step_init {
        my ($self) = @_;
        return if $self->{-event_init_done}++;
        if (my $sock = $self->{sock}) { # using DS->EventLoop
                $self->SUPER::new($sock, EPOLLIN|EPOLLET);
        }
}

sub noop {}

sub oldset { $oldset }

sub dump_and_clear_log {
        if (defined($errors_log) && -s STDIN && seek(STDIN, 0, SEEK_SET)) {
                my @pfx = @_;
                unshift(@pfx, "$errors_log ") if @pfx;
                warn @pfx, do { local $/; <STDIN> };
                truncate(STDIN, 0) or warn "ftruncate ($errors_log): $!";
        }
}

# lei(1) calls this when it can't connect
sub lazy_start {
        my ($path, $errno, $narg) = @_;
        local ($errors_log, $listener);
        ($errors_log) = ($path =~ m!\A(.+?/)[^/]+\z!);
        $errors_log .= 'errors.log';
        my $addr = pack_sockaddr_un($path);
        my $lk = bless { lock_path => $errors_log }, 'PublicInbox::Lock';
        $lk->lock_acquire;
        socket($listener, AF_UNIX, SOCK_SEQPACKET, 0) or die "socket: $!";
        if ($errno == ECONNREFUSED || $errno == ENOENT) {
                return if connect($listener, $addr); # another process won
                if ($errno == ECONNREFUSED && -S $path) {
                        unlink($path) or die "unlink($path): $!";
                }
        } else {
                $! = $errno; # allow interpolation to stringify in die
                die "connect($path): $!";
        }
        umask(077) // die("umask(077): $!");
        bind($listener, $addr) or die "bind($path): $!";
        listen($listener, 1024) or die "listen: $!";
        $lk->lock_release;
        undef $lk;
        my @st = stat($path) or die "stat($path): $!";
        my $dev_ino_expect = pack('dd', $st[0], $st[1]); # dev+ino
        local $oldset = PublicInbox::DS::block_signals();
        if ($narg == 5) {
                $send_cmd = PublicInbox::Spawn->can('send_cmd4');
                $recv_cmd = PublicInbox::Spawn->can('recv_cmd4') // do {
                        require PublicInbox::CmdIPC4;
                        $send_cmd = PublicInbox::CmdIPC4->can('send_cmd4');
                        PublicInbox::CmdIPC4->can('recv_cmd4');
                };
        }
        $recv_cmd or die <<"";
(Socket::MsgHdr || Inline::C) missing/unconfigured (narg=$narg);

        require PublicInbox::Listener;
        require PublicInbox::EOFpipe;
        (-p STDOUT) or die "E: stdout must be a pipe\n";
        open(STDIN, '+>>', $errors_log) or die "open($errors_log): $!";
        STDIN->autoflush(1);
        dump_and_clear_log("from previous daemon process:\n");
        POSIX::setsid() > 0 or die "setsid: $!";
        my $pid = fork // die "fork: $!";
        return if $pid;
        $0 = "lei-daemon $path";
        local %PATH2CFG;
        $listener->blocking(0);
        my $exit_code;
        my $pil = PublicInbox::Listener->new($listener, \&accept_dispatch);
        local $quit = do {
                pipe(my ($eof_r, $eof_w)) or die "pipe: $!";
                PublicInbox::EOFpipe->new($eof_r, \&noop, undef);
                sub {
                        $exit_code //= shift;
                        my $lis = $pil or exit($exit_code);
                        # closing eof_w triggers \&noop wakeup
                        $listener = $eof_w = $pil = $path = undef;
                        $lis->close; # DS::close
                        PublicInbox::DS->SetLoopTimeout(1000);
                };
        };
        my $sig = {
                CHLD => \&PublicInbox::DS::enqueue_reap,
                QUIT => $quit,
                INT => $quit,
                TERM => $quit,
                HUP => \&noop,
                USR1 => \&noop,
                USR2 => \&noop,
        };
        my $sigfd = PublicInbox::Sigfd->new($sig, SFD_NONBLOCK);
        local @SIG{keys %$sig} = values(%$sig) unless $sigfd;
        undef $sig;
        local $SIG{PIPE} = 'IGNORE';
        if ($sigfd) { # TODO: use inotify/kqueue to detect unlinked sockets
                undef $sigfd;
                PublicInbox::DS->SetLoopTimeout(5000);
        } else {
                # wake up every second to accept signals if we don't
                # have signalfd or IO::KQueue:
                PublicInbox::DS::sig_setmask($oldset);
                PublicInbox::DS->SetLoopTimeout(1000);
        }
        PublicInbox::DS->SetPostLoopCallback(sub {
                my ($dmap, undef) = @_;
                if (@st = defined($path) ? stat($path) : ()) {
                        if ($dev_ino_expect ne pack('dd', $st[0], $st[1])) {
                                warn "$path dev/ino changed, quitting\n";
                                $path = undef;
                        }
                } elsif (defined($path)) { # ENOENT is common
                        warn "stat($path): $!, quitting ...\n" if $! != ENOENT;
                        undef $path;
                        $quit->();
                }
                return 1 if defined($path);
                my $now = now();
                my $n = 0;
                for my $s (values %$dmap) {
                        $s->can('busy') or next;
                        if ($s->busy($now)) {
                                ++$n;
                        } else {
                                $s->close;
                        }
                }
                $n; # true: continue, false: stop
        });

        # STDIN was redirected to /dev/null above, closing STDERR and
        # STDOUT will cause the calling `lei' client process to finish
        # reading the <$daemon> pipe.
        local $SIG{__WARN__} = sub {
                $current_lei ? err($current_lei, @_) : warn(
                  strftime('%Y-%m-%dT%H:%M:%SZ', gmtime(time))," $$ ", @_);
        };
        open STDERR, '>&STDIN' or die "redirect stderr failed: $!";
        open STDOUT, '>&STDIN' or die "redirect stdout failed: $!";
        # $daemon pipe to `lei' closed, main loop begins:
        PublicInbox::DS->EventLoop;
        exit($exit_code // 0);
}

sub busy { 1 } # prevent daemon-shutdown if client is connected

# for users w/o Socket::Msghdr installed or Inline::C enabled
sub oneshot {
        my ($main_pkg) = @_;
        my $exit = $main_pkg->can('exit'); # caller may override exit()
        local $quit = $exit if $exit;
        local %PATH2CFG;
        umask(077) // die("umask(077): $!");
        my $self = bless { oneshot => 1, env => \%ENV }, __PACKAGE__;
        for (0..2) { open($self->{$_}, '+<&=', $_) or die "open fd=$_: $!" }
        dispatch($self, @ARGV);
        x_it($self, $self->{child_error}) if $self->{child_error};
}

# ensures stdout hits the FS before sock disconnects so a client
# can immediately reread it
sub DESTROY {
        my ($self) = @_;
        $self->{1}->autoflush(1) if $self->{1};
        stop_pager($self);
        my $err = $?;
        my $oneshot_pids = delete $self->{"pid.$self.$$"} or return;
        waitpid($_, 0) for keys %$oneshot_pids;
        $? = $err if $err; # preserve ->fail or ->x_it code
}

sub wq_done_wait { # dwaitpid callback
        my ($arg, $pid) = @_;
        my ($wq, $lei) = @$arg;
        my $err_type = $lei->{-err_type};
        $? and $lei->child_error($?,
                        $err_type ? "$err_type errors during $lei->{cmd}" : ());
        $lei->dclose;
}

sub wq_eof { # EOF callback for main daemon
        my ($lei) = @_;
        my $wq1 = delete $lei->{wq1} // return $lei->fail; # already failed
        $wq1->wq_wait_old(\&wq_done_wait, $lei);
}

1;