package Mojo::Reactor;

use Mojo::Base 'Mojo::EventEmitter';

use Carp 'croak';

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

use Mojo::Loader;

sub again { croak 'Method "again" not implemented by subclass' }

sub detect {

  my $try = $ENV{MOJO_REACTOR} || 'Mojo::Reactor::EV';

  return Mojo::Loader->new->load($try) ? 'Mojo::Reactor::Poll' : $try;

}

sub io { croak 'Method "io" not implemented by subclass' }

sub is_readable {

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

  my $test = $self->{test} ||= IO::Poll->new;

  $test->mask($handle, POLLIN);

  $test->poll(0);

  my $result = $test->handles(POLLIN | POLLERR | POLLHUP);

  $test->remove($handle);

  return !!$result;

}

sub is_running { croak 'Method "is_running" not implemented by subclass' }

sub one_tick   { croak 'Method "one_tick" not implemented by subclass' }

sub recurring  { croak 'Method "recurring" not implemented by subclass' }

sub remove     { croak 'Method "remove" not implemented by subclass' }

sub start      { croak 'Method "start" not implemented by subclass' }

sub stop       { croak 'Method "stop" not implemented by subclass' }

sub timer      { croak 'Method "timer" not implemented by subclass' }

sub watch      { croak 'Method "watch" not implemented by subclass' }

1;

=encoding utf8

=head1 NAME

Mojo::Reactor - Low level event reactor base class

=head1 SYNOPSIS

  package Mojo::Reactor::MyEventLoop;

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

  $ENV{MOJO_REACTOR} ||= 'Mojo::Reactor::MyEventLoop';

  sub again      {...}

  sub io         {...}

  sub is_running {...}

  sub one_tick   {...}

  sub recurring  {...}

  sub remove     {...}

  sub start      {...}

  sub stop       {...}

  sub timer      {...}

  sub watch      {...}

=head1 DESCRIPTION

L<Mojo::Reactor> is an abstract base class for low level event reactors.

=head1 EVENTS

L<Mojo::Reactor> inherits all events from L<Mojo::EventEmitter> and can emit

the following new ones.

=head2 error

  $reactor->on(error => sub {

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

    ...

  });

Emitted for exceptions caught in callbacks, fatal if unhandled. Note that if

this event is unhandled or fails it might kill your program, so you need to be

careful.

  $reactor->on(error => sub {

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

    say "Something very bad happened: $err";

  });

=head1 METHODS

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

implements the following new ones.

=head2 again

  $reactor->again($id);

Restart active timer. Meant to be overloaded in a subclass.

=head2 detect

  my $class = Mojo::Reactor->detect;

Detect and load the best reactor implementation available, will try the value

of the MOJO_REACTOR environment variable, L<Mojo::Reactor::EV> or

L<Mojo::Reactor::Poll>.

  # Instantiate best reactor implementation available

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

=head2 io

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

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

readable or writable. Meant to be overloaded in a subclass.

  # Callback will be invoked twice if handle becomes readable and writable

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

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

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

  });

=head2 is_readable

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

Quick non-blocking check if a handle is readable, useful for identifying

tainted sockets.

=head2 is_running

  my $bool = $reactor->is_running;

Check if reactor is running. Meant to be overloaded in a subclass.

=head2 one_tick

  $reactor->one_tick;

Run reactor until an event occurs. Note that this method can recurse back into

the reactor, so you need to be careful. Meant to be overloaded in a subclass.

  # Don't block longer than 0.5 seconds

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

  $reactor->one_tick;

  $reactor->remove($id);

=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. Meant to be overloaded in a subclass.

  # Invoke as soon as possible

  $reactor->recurring(0 => sub { say 'Reactor tick.' });

=head2 remove

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

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

Remove handle or timer. Meant to be overloaded in a subclass.

=head2 start

  $reactor->start;

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

called. Note that some reactors stop automatically if there are no events

being watched anymore. Meant to be overloaded in a subclass.

=head2 stop

  $reactor->stop;

Stop watching for I/O and timer events. Meant to be overloaded in a subclass.

=head2 timer

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

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

seconds. Meant to be overloaded in a subclass.

  # Invoke as soon as possible

  $reactor->timer(0 => sub { say 'Next tick.' });

=head2 watch

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

Change I/O events to watch handle for with true and false values. Meant to be

overloaded in a subclass. Note that this method requires an active I/O

watcher.

  # Watch only for readable events

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

  # Watch only for writable events

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

  # Watch for readable and writable events

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

  # Pause watching for events

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

=head1 SEE ALSO

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

=cut