package Mojo::Reactor::Poll;

use Mojo::Base 'Mojo::Reactor';

use IO::Poll qw(POLLERR POLLHUP POLLIN POLLOUT);

use List::Util 'min';

use Mojo::Util qw(md5_sum steady_time);

use Time::HiRes 'usleep';

sub again {

  my $timer = shift->{timers}{shift()};

  $timer->{time} = steady_time + $timer->{after};

}

sub io {

  my ($self, $handle, $cb) = @_;

  $self->{io}{fileno $handle} = {cb => $cb};

  return $self->watch($handle, 1, 1);

}

sub is_running { !!shift->{running} }

sub one_tick {

  my $self = shift;

  # Remember state for later

  my $running = $self->{running};

  $self->{running} = 1;

  # Wait for one event

  my $i;

  my $poll = $self->_poll;

  until ($i) {

    # Stop automatically if there is nothing to watch

    return $self->stop unless keys %{$self->{timers}} || keys %{$self->{io}};

    # Calculate ideal timeout based on timers

    my $min = min map { $_->{time} } values %{$self->{timers}};

    my $timeout = defined $min ? ($min - steady_time) : 0.5;

    $timeout = 0 if $timeout < 0;

    # I/O

    if (keys %{$self->{io}}) {

      $poll->poll($timeout);

      ++$i and $self->_sandbox('Read', $self->{io}{fileno $_}{cb}, 0)

        for $poll->handles(POLLIN | POLLHUP | POLLERR);

      ++$i and $self->_sandbox('Write', $self->{io}{fileno $_}{cb}, 1)

        for $poll->handles(POLLOUT);

    }

    # Wait for timeout if poll can't be used

    elsif ($timeout) { usleep $timeout * 1000000 }

    # Timers (time should not change in between timers)

    my $now = steady_time;

    for my $id (keys %{$self->{timers}}) {

      next unless my $t = $self->{timers}{$id};

      next unless $t->{time} <= $now;

      # Recurring timer

      if (exists $t->{recurring}) { $t->{time} = $now + $t->{recurring} }

      # Normal timer

      else { $self->remove($id) }

      ++$i and $self->_sandbox("Timer $id", $t->{cb}) if $t->{cb};

    }

  }

  # Restore state if necessary

  $self->{running} = $running if $self->{running};

}

sub recurring { shift->_timer(1, @_) }

sub remove {

  my ($self, $remove) = @_;

  return !!delete $self->{timers}{$remove} unless ref $remove;

  $self->_poll->remove($remove);

  return !!delete $self->{io}{fileno $remove};

}

sub start {

  my $self = shift;

  return if $self->{running}++;

  $self->one_tick while $self->{running};

}

sub stop { delete shift->{running} }

sub timer { shift->_timer(0, @_) }

sub watch {

  my ($self, $handle, $read, $write) = @_;

  my $poll = $self->_poll;

  $poll->remove($handle);

  if ($read && $write) { $poll->mask($handle, POLLIN | POLLOUT) }

  elsif ($read)  { $poll->mask($handle, POLLIN) }

  elsif ($write) { $poll->mask($handle, POLLOUT) }

  return $self;

}

sub _poll { shift->{poll} ||= IO::Poll->new }

sub _sandbox {

  my ($self, $event, $cb) = (shift, shift, shift);

  eval { $self->$cb(@_); 1 } or $self->emit(error => "$event failed: $@");

}

sub _timer {

  my ($self, $recurring, $after, $cb) = @_;

  my $timers = $self->{timers} //= {};

  my $id;

  do { $id = md5_sum('t' . steady_time . rand 999) } while $timers->{$id};

  my $timer = $timers->{$id}

    = {cb => $cb, after => $after, time => steady_time + $after};

  $timer->{recurring} = $after if $recurring;

  return $id;

}

1;

=encoding utf8

=head1 NAME

Mojo::Reactor::Poll - Low level event reactor with poll support

=head1 SYNOPSIS

  use Mojo::Reactor::Poll;

  # Watch if handle becomes readable or writable

  my $reactor = Mojo::Reactor::Poll->new;

  $reactor->io($handle => sub {

    my ($reactor, $writable) = @_;

    say $writable ? 'Handle is writable' : 'Handle is readable';

  });

  # Change to watching only if handle becomes writable

  $reactor->watch($handle, 0, 1);

  # Add a timer

  $reactor->timer(15 => sub {

    my $reactor = shift;

    $reactor->remove($handle);

    say 'Timeout!';

  });

  # Start reactor if necessary

  $reactor->start unless $reactor->is_running;

=head1 DESCRIPTION

L<Mojo::Reactor::Poll> is a low level event reactor based on L<IO::Poll>.

=head1 EVENTS

L<Mojo::Reactor::Poll> inherits all events from L<Mojo::Reactor>.

=head1 METHODS

L<Mojo::Reactor::Poll> inherits all methods from L<Mojo::Reactor> and

implements the following new ones.

=head2 again

  $reactor->again($id);

Restart active timer.

=head2 io

  $reactor = $reactor->io($handle => sub {...});

Watch handle for I/O events, invoking the callback whenever handle becomes

readable or writable.

=head2 is_running

  my $bool = $reactor->is_running;

Check if reactor is running.

=head2 one_tick

  $reactor->one_tick;

Run reactor until an event occurs or no events are being watched anymore. Note

that this method can recurse back into the reactor, so you need to be careful.

=head2 recurring

  my $id = $reactor->recurring(0.25 => sub {...});

Create a new recurring timer, invoking the callback repeatedly after a given

amount of time in seconds.

=head2 remove

  my $bool = $reactor->remove($handle);

  my $bool = $reactor->remove($id);

Remove handle or timer.

=head2 start

  $reactor->start;

Start watching for I/O and timer events, this will block until L</"stop"> is

called or no events are being watched anymore.

=head2 stop

  $reactor->stop;

Stop watching for I/O and timer events.

=head2 timer

  my $id = $reactor->timer(0.5 => sub {...});

Create a new timer, invoking the callback after a given amount of time in

seconds.

=head2 watch

  $reactor = $reactor->watch($handle, $readable, $writable);

Change I/O events to watch handle for with true and false values. Note that

this method requires an active I/O watcher.

=head1 SEE ALSO

L<Mojolicious>, L<Mojolicious::Guides>, L<http://mojolicio.us>.

=cut