package Minion::Backend::Pg;
use Mojo::Base 'Minion::Backend';

use Carp 'croak';
use Mojo::IOLoop;
use Mojo::Pg 4.0;
use Sys::Hostname 'hostname';

has 'pg';

sub broadcast {
  my ($self, $command, $args, $ids) = (shift, shift, shift || [], shift || []);
  return !!$self->pg->db->query(
    q{update minion_workers set inbox = inbox || $1::jsonb
      where (id = any ($2) or $2 = '{}')}, {json => [[$command, @$args]]}, $ids
  )->rows;
}

sub dequeue {
  my ($self, $id, $wait, $options) = @_;

  if ((my $job = $self->_try($id, $options))) { return $job }
  return undef if Mojo::IOLoop->is_running;

  my $db = $self->pg->db;
  $db->listen('minion.job')->on(notification => sub { Mojo::IOLoop->stop });
  my $timer = Mojo::IOLoop->timer($wait => sub { Mojo::IOLoop->stop });
  Mojo::IOLoop->start;
  $db->unlisten('*') and Mojo::IOLoop->remove($timer);
  undef $db;

  return $self->_try($id, $options);
}

sub enqueue {
  my ($self, $task, $args, $options) = (shift, shift, shift || [], shift || {});

  my $db = $self->pg->db;
  return $db->query(
    "insert into minion_jobs
       (args, attempts, delayed, notes, parents, priority, queue, task)
     values (?, ?, (now() + (interval '1 second' * ?)), ?, ?, ?, ?, ?)
     returning id", {json => $args}, $options->{attempts} // 1,
    $options->{delay} // 0, {json => $options->{notes} || {}},
    $options->{parents} || [], $options->{priority} // 0,
    $options->{queue} // 'default', $task
  )->hash->{id};
}

sub fail_job   { shift->_update(1, @_) }
sub finish_job { shift->_update(0, @_) }

sub history {
  my $self = shift;

  my $daily = $self->pg->db->query(
    "select extract(epoch from ts) as epoch,
       coalesce(failed_jobs, 0) as failed_jobs,
       coalesce(finished_jobs, 0) as finished_jobs
     from (
       select extract (day from finished) as day,
         extract(hour from finished) as hour,
         count(*) filter (where state = 'failed') as failed_jobs,
         count(*) filter (where state = 'finished') as finished_jobs
       from minion_jobs
       where finished > now() - interval '23 hours'
       group by day, hour
     ) as j right outer join (
       select *
       from generate_series(now() - interval '23 hour', now(), '1 hour') as ts
     ) as s on extract(hour from ts) = j.hour and extract(day from ts) = j.day
     order by epoch asc"
  )->hashes->to_array;

  return {daily => $daily};
}

sub list_jobs {
  my ($self, $offset, $limit, $options) = @_;

  my $jobs = $self->pg->db->query(
    'select id, args, attempts,
       array(select id from minion_jobs where parents @> ARRAY[j.id])
         as children, extract(epoch from created) as created,
       extract(epoch from delayed) as delayed,
       extract(epoch from finished) as finished, notes, parents, priority,
       queue, result, extract(epoch from retried) as retried, retries,
       extract(epoch from started) as started, state, task,
       count(*) over() as total, worker
     from minion_jobs as j
     where (id = any ($1) or $1 is null) and (queue = any ($2) or $2 is null)
       and (state = any ($3) or $3 is null) and (task = any ($4) or $4 is null)
     order by id desc
     limit $5 offset $6', @$options{qw(ids queues states tasks)}, $limit,
    $offset
  )->expand->hashes->to_array;
  return _total('jobs', $jobs);
}

sub list_locks {
  my ($self, $offset, $limit, $options) = @_;

  my $locks = $self->pg->db->query(
    'select name, extract(epoch from expires) as expires,
       count(*) over() as total from minion_locks
     where expires > now() and (name = any ($1) or $1 is null)
     order by id desc limit $2 offset $3', $options->{names}, $limit, $offset
  )->hashes->to_array;
  return _total('locks', $locks);
}

sub list_workers {
  my ($self, $offset, $limit, $options) = @_;

  my $workers = $self->pg->db->query(
    "select id, extract(epoch from notified) as notified, array(
        select id from minion_jobs
        where state = 'active' and worker = minion_workers.id
      ) as jobs, host, pid, status, extract(epoch from started) as started,
      count(*) over() as total
     from minion_workers
     where (id = any (\$1) or \$1 is null)
     order by id desc limit \$2 offset \$3", $options->{ids}, $limit, $offset
  )->expand->hashes->to_array;
  return _total('workers', $workers);
}

sub lock {
  my ($self, $name, $duration, $options) = (shift, shift, shift, shift // {});
  return !!$self->pg->db->query('select * from minion_lock(?, ?, ?)',
    $name, $duration, $options->{limit} || 1)->array->[0];
}

sub new {
  my $self = shift->SUPER::new(pg => Mojo::Pg->new(@_));

  my $db = Mojo::Pg->new(@_)->db;
  croak 'PostgreSQL 9.5 or later is required'
    if $db->dbh->{pg_server_version} < 90500;
  $db->disconnect;

  $self->pg->auto_migrate(1)->migrations->name('minion')->from_data;

  return $self;
}

sub note {
  my ($self, $id, $merge) = @_;
  return !!$self->pg->db->query(
    'update minion_jobs set notes = notes || ? where id = ?',
    {json => $merge}, $id)->rows;
}

sub receive {
  my $array = shift->pg->db->query(
    "update minion_workers as new set inbox = '[]'
     from (select id, inbox from minion_workers where id = ? for update) as old
     where new.id = old.id and old.inbox != '[]'
     returning old.inbox", shift
  )->expand->array;
  return $array ? $array->[0] : [];
}

sub register_worker {
  my ($self, $id, $options) = (shift, shift, shift || {});

  return $self->pg->db->query(
    q{insert into minion_workers (id, host, pid, status)
      values (coalesce($1, nextval('minion_workers_id_seq')), $2, $3, $4)
      on conflict(id) do update set notified = now(), status = $4
      returning id}, $id, $self->{host} //= hostname, $$,
    {json => $options->{status} // {}}
  )->hash->{id};
}

sub remove_job {
  !!shift->pg->db->query(
    "delete from minion_jobs
     where id = ? and state in ('inactive', 'failed', 'finished')
     returning 1", shift
  )->rows;
}

sub repair {
  my $self = shift;

  # Workers without heartbeat
  my $db     = $self->pg->db;
  my $minion = $self->minion;
  $db->query(
    "delete from minion_workers
     where notified < now() - interval '1 second' * ?", $minion->missing_after
  );

  # Jobs with missing worker (can be retried)
  my $fail = $db->query(
    "select id, retries from minion_jobs as j
     where state = 'active'
       and not exists (select 1 from minion_workers where id = j.worker)"
  )->hashes;
  $fail->each(sub { $self->fail_job(@$_{qw(id retries)}, 'Worker went away') });

  # Old jobs with no unresolved dependencies
  $db->query(
    "delete from minion_jobs as j
     where finished <= now() - interval '1 second' * ? and not exists (
       select 1 from minion_jobs
       where parents @> ARRAY[j.id] and state != 'finished'
     ) and state = 'finished'", $minion->remove_after
  );
}

sub reset {
  shift->pg->db->query(
    'truncate minion_jobs, minion_locks, minion_workers restart identity');
}

sub retry_job {
  my ($self, $id, $retries, $options) = (shift, shift, shift, shift || {});

  return !!$self->pg->db->query(
    "update minion_jobs
     set attempts = coalesce(?, attempts),
       delayed = (now() + (interval '1 second' * ?)),
       parents = coalesce(?, parents), priority = coalesce(?, priority),
       queue = coalesce(?, queue), retried = now(), retries = retries + 1,
       state = 'inactive'
     where id = ? and retries = ?
     returning 1", $options->{attempts}, $options->{delay} // 0,
    @$options{qw(parents priority queue)}, $id, $retries
  )->rows;
}

sub stats {
  my $self = shift;

  my $stats = $self->pg->db->query(
    "select count(*) filter (where state = 'inactive') as inactive_jobs,
       count(*) filter (where state = 'active') as active_jobs,
       count(*) filter (where state = 'failed') as failed_jobs,
       count(*) filter (where state = 'finished') as finished_jobs,
       count(*) filter (where state = 'inactive'
         and delayed > now()) as delayed_jobs,
       (select count(*) from minion_locks where expires > now())
         as active_locks,
       count(distinct worker) filter (where state = 'active') as active_workers,
       (select case when is_called then last_value else 0 end
         from minion_jobs_id_seq) as enqueued_jobs,
       (select count(*) from minion_workers) as inactive_workers,
       extract(epoch from now() - pg_postmaster_start_time()) as uptime
     from minion_jobs"
  )->hash;
  $stats->{inactive_workers} -= $stats->{active_workers};

  return $stats;
}

sub unlock {
  !!shift->pg->db->query(
    'delete from minion_locks where id = (
       select id from minion_locks
       where expires > now() and name = ? order by expires limit 1
     ) returning 1', shift
  )->rows;
}

sub unregister_worker {
  shift->pg->db->query('delete from minion_workers where id = ?', shift);
}

sub _total {
  my ($name, $results) = @_;
  my $total = @$results ? $results->[0]{total} : 0;
  delete $_->{total} for @$results;
  return {total => $total, $name => $results};
}

sub _try {
  my ($self, $id, $options) = @_;

  return $self->pg->db->query(
    "update minion_jobs
     set started = now(), state = 'active', worker = ?
     where id = (
       select id from minion_jobs as j
       where delayed <= now() and id = coalesce(?, id)
         and (parents = '{}' or not exists (
           select 1 from minion_jobs
           where id = any (j.parents)
             and state in ('inactive', 'active', 'failed')
         )) and queue = any (?) and state = 'inactive' and task = any (?)
       order by priority desc, id
       limit 1
       for update skip locked
     )
     returning id, args, retries, task", $id, $options->{id},
    $options->{queues} || ['default'], [keys %{$self->minion->tasks}]
  )->expand->hash;
}

sub _update {
  my ($self, $fail, $id, $retries, $result) = @_;

  return undef unless my $row = $self->pg->db->query(
    "update minion_jobs
     set finished = now(), result = ?, state = ?
     where id = ? and retries = ? and state = 'active'
     returning attempts", {json => $result}, $fail ? 'failed' : 'finished',
    $id, $retries
  )->array;

  return 1 if !$fail || (my $attempts = $row->[0]) == 1;
  return 1 if $retries >= ($attempts - 1);
  my $delay = $self->minion->backoff->($retries);
  return $self->retry_job($id, $retries, {delay => $delay});
}

1;

=encoding utf8

=head1 NAME

Minion::Backend::Pg - PostgreSQL backend

=head1 SYNOPSIS

  use Minion::Backend::Pg;

  my $backend = Minion::Backend::Pg->new('postgresql://postgres@/test');

=head1 DESCRIPTION

L<Minion::Backend::Pg> is a backend for L<Minion> based on L<Mojo::Pg>. All
necessary tables will be created automatically with a set of migrations named
C<minion>. Note that this backend uses many bleeding edge features, so only the
latest, stable version of PostgreSQL is fully supported.

=head1 ATTRIBUTES

L<Minion::Backend::Pg> inherits all attributes from L<Minion::Backend> and
implements the following new ones.

=head2 pg

  my $pg   = $backend->pg;
  $backend = $backend->pg(Mojo::Pg->new);

L<Mojo::Pg> object used to store all data.

=head1 METHODS

L<Minion::Backend::Pg> inherits all methods from L<Minion::Backend> and
implements the following new ones.

=head2 broadcast

  my $bool = $backend->broadcast('some_command');
  my $bool = $backend->broadcast('some_command', [@args]);
  my $bool = $backend->broadcast('some_command', [@args], [$id1, $id2, $id3]);

Broadcast remote control command to one or more workers.

=head2 dequeue

  my $job_info = $backend->dequeue($worker_id, 0.5);
  my $job_info = $backend->dequeue($worker_id, 0.5, {queues => ['important']});

Wait a given amount of time in seconds for a job, dequeue it and transition from
C<inactive> to C<active> state, or return C<undef> if queues were empty.

These options are currently available:

=over 2

=item id

  id => '10023'

Dequeue a specific job.

=item queues

  queues => ['important']

One or more queues to dequeue jobs from, defaults to C<default>.

=back

These fields are currently available:

=over 2

=item args

  args => ['foo', 'bar']

Job arguments.

=item id

  id => '10023'

Job ID.

=item retries

  retries => 3

Number of times job has been retried.

=item task

  task => 'foo'

Task name.

=back

=head2 enqueue

  my $job_id = $backend->enqueue('foo');
  my $job_id = $backend->enqueue(foo => [@args]);
  my $job_id = $backend->enqueue(foo => [@args] => {priority => 1});

Enqueue a new job with C<inactive> state.

These options are currently available:

=over 2

=item attempts

  attempts => 25

Number of times performing this job will be attempted, with a delay based on
L<Minion/"backoff"> after the first attempt, defaults to C<1>.

=item delay

  delay => 10

Delay job for this many seconds (from now), defaults to C<0>.

=item notes

  notes => {foo => 'bar', baz => [1, 2, 3]}

Hash reference with arbitrary metadata for this job.

=item parents

  parents => [$id1, $id2, $id3]

One or more existing jobs this job depends on, and that need to have
transitioned to the state C<finished> before it can be processed.

=item priority

  priority => 5

Job priority, defaults to C<0>. Jobs with a higher priority get performed first.

=item queue

  queue => 'important'

Queue to put job in, defaults to C<default>.

=back

=head2 fail_job

  my $bool = $backend->fail_job($job_id, $retries);
  my $bool = $backend->fail_job($job_id, $retries, 'Something went wrong!');
  my $bool = $backend->fail_job(
    $job_id, $retries, {whatever => 'Something went wrong!'});

Transition from C<active> to C<failed> state with or without a result, and if
there are attempts remaining, transition back to C<inactive> with a delay based
on L<Minion/"backoff">.

=head2 finish_job

  my $bool = $backend->finish_job($job_id, $retries);
  my $bool = $backend->finish_job($job_id, $retries, 'All went well!');
  my $bool = $backend->finish_job(
    $job_id, $retries, {whatever => 'All went well!'});

Transition from C<active> to C<finished> state with or without a result.

=head2 history

  my $history = $backend->history;

Get history information for job queue. Note that this method is EXPERIMENTAL and
might change without warning!

These fields are currently available:

=over 2

=item daily

  daily => [{epoch => 12345, finished_jobs => 95, failed_jobs => 2}, ...]

Hourly counts for processed jobs from the past day.

=back

=head2 list_jobs

  my $results = $backend->list_jobs($offset, $limit);
  my $results = $backend->list_jobs($offset, $limit, {states => ['inactive']});

Returns the information about jobs in batches.

  # Get the total number of results (without limit)
  my $num = $backend->list_jobs(0, 100, {queues => ['important']})->{total};

  # Check job state
  my $results = $backend->list_jobs(0, 1, {ids => [$job_id]});
  my $state = $results->{jobs}[0]{state};

  # Get job result
  my $results = $backend->list_jobs(0, 1, {ids => [$job_id]});
  my $result  = $results->{jobs}[0]{result};

These options are currently available:

=over 2

=item ids

  ids => ['23', '24']

List only jobs with these ids.

=item queues

  queues => ['important', 'unimportant']

List only jobs in these queues.

=item states

  states => ['inactive', 'active']

List only jobs in these states.

=item tasks

  tasks => ['foo', 'bar']

List only jobs for these tasks.

=back

These fields are currently available:

=over 2

=item args

  args => ['foo', 'bar']

Job arguments.

=item attempts

  attempts => 25

Number of times performing this job will be attempted.

=item children

  children => ['10026', '10027', '10028']

Jobs depending on this job.

=item created

  created => 784111777

Epoch time job was created.

=item delayed

  delayed => 784111777

Epoch time job was delayed to.

=item finished

  finished => 784111777

Epoch time job was finished.

=item id

  id => 10025

Job id.

=item notes

  notes => {foo => 'bar', baz => [1, 2, 3]}

Hash reference with arbitrary metadata for this job.

=item parents

  parents => ['10023', '10024', '10025']

Jobs this job depends on.

=item priority

  priority => 3

Job priority.

=item queue

  queue => 'important'

Queue name.

=item result

  result => 'All went well!'

Job result.

=item retried

  retried => 784111777

Epoch time job has been retried.

=item retries

  retries => 3

Number of times job has been retried.

=item started

  started => 784111777

Epoch time job was started.

=item state

  state => 'inactive'

Current job state, usually C<active>, C<failed>, C<finished> or C<inactive>.

=item task

  task => 'foo'

Task name.

=item worker

  worker => '154'

Id of worker that is processing the job.

=back

=head2 list_locks

  my $results = $backend->list_locks($offset, $limit);
  my $results = $backend->list_locks($offset, $limit, {names => ['foo']});

Returns information about locks in batches.

  # Get the total number of results (without limit)
  my $num = $backend->list_locks(0, 100, {names => ['bar']})->{total};

  # Check expiration time
  my $results = $backend->list_locks(0, 1, {names => ['foo']});
  my $expires = $results->{locks}[0]{expires};

These options are currently available:

=over 2

=item names

  names => ['foo', 'bar']

List only locks with these names.

=back

These fields are currently available:

=over 2

=item expires

  expires => 784111777

Epoch time this lock will expire.

=item name

  name => 'foo'

Lock name.

=back

=head2 list_workers

  my $results = $backend->list_workers($offset, $limit);
  my $results = $backend->list_workers($offset, $limit, {ids => [23]});

Returns information about workers in batches.

  # Get the total number of results (without limit)
  my $num = $backend->list_workers(0, 100)->{total};

  # Check worker host
  my $results = $backend->list_workers(0, 1, {ids => [$worker_id]});
  my $host    = $results->{workers}[0]{host};

These options are currently available:

=over 2

=item ids

  ids => ['23', '24']

List only workers with these ids.

=back

These fields are currently available:

=over 2

=item id

  id => 22

Worker id.

=item host

  host => 'localhost'

Worker host.

=item jobs

  jobs => ['10023', '10024', '10025', '10029']

Ids of jobs the worker is currently processing.

=item notified

  notified => 784111777

Epoch time worker sent the last heartbeat.

=item pid

  pid => 12345

Process id of worker.

=item started

  started => 784111777

Epoch time worker was started.

=item status

  status => {queues => ['default', 'important']}

Hash reference with whatever status information the worker would like to share.

=back

=head2 lock

  my $bool = $backend->lock('foo', 3600);
  my $bool = $backend->lock('foo', 3600, {limit => 20});

Try to acquire a named lock that will expire automatically after the given
amount of time in seconds. An expiration time of C<0> can be used to check if a
named lock already exists without creating one.

These options are currently available:

=over 2

=item limit

  limit => 20

Number of shared locks with the same name that can be active at the same time,
defaults to C<1>.

=back

=head2 new

  my $backend = Minion::Backend::Pg->new('postgresql://postgres@/test');
  my $backend = Minion::Backend::Pg->new(Mojo::Pg->new);

Construct a new L<Minion::Backend::Pg> object.

=head2 note

  my $bool = $backend->note($job_id, {mojo => 'rocks', minion => 'too'});

Change one or more metadata fields for a job.

=head2 receive

  my $commands = $backend->receive($worker_id);

Receive remote control commands for worker.

=head2 register_worker

  my $worker_id = $backend->register_worker;
  my $worker_id = $backend->register_worker($worker_id);
  my $worker_id = $backend->register_worker(
    $worker_id, {status => {queues => ['default', 'important']}});

Register worker or send heartbeat to show that this worker is still alive.

These options are currently available:

=over 2

=item status

  status => {queues => ['default', 'important']}

Hash reference with whatever status information the worker would like to share.

=back

=head2 remove_job

  my $bool = $backend->remove_job($job_id);

Remove C<failed>, C<finished> or C<inactive> job from queue.

=head2 repair

  $backend->repair;

Repair worker registry and job queue if necessary.

=head2 reset

  $backend->reset;

Reset job queue.

=head2 retry_job

  my $bool = $backend->retry_job($job_id, $retries);
  my $bool = $backend->retry_job($job_id, $retries, {delay => 10});

Transition job back to C<inactive> state, already C<inactive> jobs may also be
retried to change options.

These options are currently available:

=over 2

=item attempts

  attempts => 25

Number of times performing this job will be attempted.

=item delay

  delay => 10

Delay job for this many seconds (from now), defaults to C<0>.

=item parents

  parents => [$id1, $id2, $id3]

Jobs this job depends on.

=item priority

  priority => 5

Job priority.

=item queue

  queue => 'important'

Queue to put job in.

=back

=head2 stats

  my $stats = $backend->stats;

Get statistics for the job queue.

These fields are currently available:

=over 2

=item active_jobs

  active_jobs => 100

Number of jobs in C<active> state.

=item active_locks

  active_locks => 100

Number of active named locks.

=item active_workers

  active_workers => 100

Number of workers that are currently processing a job.

=item delayed_jobs

  delayed_jobs => 100

Number of jobs in C<inactive> state that are scheduled to run at specific time
in the future. Note that this field is EXPERIMENTAL and might change without
warning!

=item enqueued_jobs

  enqueued_jobs => 100000

Rough estimate of how many jobs have ever been enqueued. Note that this field is
EXPERIMENTAL and might change without warning!

=item failed_jobs

  failed_jobs => 100

Number of jobs in C<failed> state.

=item finished_jobs

  finished_jobs => 100

Number of jobs in C<finished> state.

=item inactive_jobs

  inactive_jobs => 100

Number of jobs in C<inactive> state.

=item inactive_workers

  inactive_workers => 100

Number of workers that are currently not processing a job.

=item uptime

  uptime => 1000

Uptime in seconds.

=back

=head2 unlock

  my $bool = $backend->unlock('foo');

Release a named lock.

=head2 unregister_worker

  $backend->unregister_worker($worker_id);

Unregister worker.

=head1 SEE ALSO

L<Minion>, L<Mojolicious::Guides>, L<https://mojolicious.org>.

=cut

__DATA__

@@ minion
-- 1 up
create table if not exists minion_jobs (
  id       bigserial not null primary key,
  args     json not null,
  created  timestamp with time zone not null,
  delayed  timestamp with time zone not null,
  finished timestamp with time zone,
  priority int not null,
  result   json,
  retried  timestamp with time zone,
  retries  int not null,
  started  timestamp with time zone,
  state    text not null,
  task     text not null,
  worker   bigint
);
create table if not exists minion_workers (
  id      bigserial not null primary key,
  host    text not null,
  pid     int not null,
  started timestamp with time zone not null
);

-- 1 down
drop table if exists minion_jobs;
drop table if exists minion_workers;

-- 2 up
alter table minion_jobs alter column created set default now();
alter table minion_jobs alter column state set default 'inactive';
alter table minion_jobs alter column retries set default 0;
alter table minion_workers add column
  notified timestamp with time zone not null default now();
alter table minion_workers alter column started set default now();

-- 4 up
alter table minion_jobs add column queue text not null default 'default';

-- 5 up
alter table minion_jobs add column attempts int not null default 1;

-- 7 up
create type minion_state as enum ('inactive', 'active', 'failed', 'finished');
alter table minion_jobs alter column state set default 'inactive'::minion_state;
alter table minion_jobs
  alter column state type minion_state using state::minion_state;
alter table minion_jobs alter column args type jsonb using args::jsonb;
alter table minion_jobs alter column result type jsonb using result::jsonb;

-- 7 down
alter table minion_jobs alter column state type text using state;
alter table minion_jobs alter column state set default 'inactive';
drop type if exists minion_state;

-- 8 up
alter table minion_jobs add constraint args check(jsonb_typeof(args) = 'array');

-- 9 up
create or replace function minion_jobs_notify_workers() returns trigger as $$
  begin
    if new.delayed <= now() then
      notify "minion.job";
    end if;
    return null;
  end;
$$ language plpgsql;
set client_min_messages to warning;
drop trigger if exists minion_jobs_insert_trigger on minion_jobs;
drop trigger if exists minion_jobs_notify_workers_trigger on minion_jobs;
set client_min_messages to notice;
create trigger minion_jobs_notify_workers_trigger
  after insert or update of retries on minion_jobs
  for each row execute procedure minion_jobs_notify_workers();

-- 9 down
drop trigger if exists minion_jobs_notify_workers_trigger on minion_jobs;
drop function if exists minion_jobs_notify_workers();

-- 10 up
alter table minion_jobs add column parents bigint[] not null default '{}';

-- 11 up
create index on minion_jobs (state, priority desc, id);

-- 12 up
alter table minion_workers add column inbox jsonb
  check(jsonb_typeof(inbox) = 'array') not null default '[]';

-- 15 up
alter table minion_workers add column status jsonb
  check(jsonb_typeof(status) = 'object') not null default '{}';

-- 16 up
create index on minion_jobs using gin (parents);
create table if not exists minion_locks (
  id      bigserial not null primary key,
  name    text not null,
  expires timestamp with time zone not null
);

-- 16 down
drop table if exists minion_locks;

-- 17 up
alter table minion_jobs add column notes jsonb
  check(jsonb_typeof(notes) = 'object') not null default '{}';
alter table minion_locks set unlogged;
create index on minion_locks (name, expires);

-- 18 up
create or replace function minion_lock(text, int, int) returns bool as $$
declare
  new_expires timestamp with time zone = now() + (interval '1 second' * $2);
begin
  lock table minion_locks in exclusive mode;
  delete from minion_locks where expires < now();
  if (select count(*) >= $3 from minion_locks where name = $1) then
    return false;
  end if;
  if new_expires > now() then
    insert into minion_locks (name, expires) values ($1, new_expires);
  end if;
  return true;
end;
$$ language plpgsql;

-- 18 down
drop function if exists minion_lock(text, int, int);