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package AE::AdHoc;

use warnings;
use strict;

=head1 NAME

AE::AdHoc - Simplified interface for tests/examples of AnyEvent-related code.

=head1 NON-DESCRIPTION

This module is NOT for introducing oneself to AnyEvent, despite the mention of
"simplified". More over, it REQUIRES knowledge of what a conditional variable,
or simply "condvar", is. See L<Anyevent::Intro>.

This module is NOT for building other modules, it's for running them with
minimal typing.

=head1 SYNOPSIS

Suppose we have a subroutine named C<do_stuff( @args, $subref )>
that is designed to run under AnyEvent. As do_stuff may have to wait for
some external events to happen, it does not return a value right away.
Instead, it will call C<$subref-E<gt>( $results )> when stuff is done.

Now we need to test do_stuff, so we set up an event loop. We also need a timer,
because a test that runs forever is annoying. So the script goes like this:

    use AnyEvent;

    # set up event loop
    my $cv = AnyEvent->condvar;
    my $timer = AnyEvent->timer(
        after => 10, cb => sub { $cv->croak("Timeout"); }
    );

    do_stuff( @args, sub{ $cv->send(shift); } );

    # run event loop, get rid of timer
    my $result = $cv->recv();
    undef $timer;

    # finally
    analyze_results( $result );

Now, the same with AE::AdHoc:

    use AE::AdHoc;

    my $result = ae_recv {
         do_stuff( @args, ae_send );
    } 10; # timeout
    analyze_results( $result );

=head1 EXPORT

Functions C<ae_recv>, C<ae_send>, C<ae_croak>, C<ae_begin>, C<ae_end>, and
C<ae_goal> are exported by default.

=head1 SUBROUTINES

B<Note>: Anywhere below, C<$cv> means L<AnyEvent>'s conditional variable
responsible for current event loop. See C<condvar> section of L<AnyEvent>.

=cut

our $VERSION = '0.0805';

use Carp;
use AnyEvent::Strict;
use Scalar::Util qw(weaken looks_like_number);

use Exporter;

BEGIN {
	our @ISA = qw(Exporter);
	our @EXPORT = qw(ae_recv ae_send ae_croak ae_begin ae_end ae_goal ae_action);
};

=head2 ae_recv { CODE; } [ $timeout ] %options;

The main entry point of the module.

Run CODE block, enter event loop and wait for $timeout seconds for callbacks
set up in CODE to fire, then die. Return whatever was sent via C<ae_send>.

$timeout must be a nonzero real number. Negative value means "run forever".
$timeout=0 would be ambigous, so it's excluded.

Options may include:

=over

=item * timeout - override the $timeout parameter (one timeout MUST be present).

=item * soft_timeout - Override $timeout, and don't die,
but return undef instead.

=back

Other functions in this module would die if called outside of C<ae_recv>.

=cut

# $cv is our so that it can be localized and act as a lock
our $cv;

# These are for error pretty-printing.
my $iter; # ++ every time
our $where; # "$file:$line[$iter]"

sub ae_recv (&@) { ## no critic
	my $code = shift;
	my $timeout = @_ % 2 && shift; # load bare timeout if present
	my %opt = @_;

	$timeout = $opt{timeout} || $opt{soft_timeout} || $timeout;

	# check we're not in event loop before dying
	$cv and _croak("Nested calls to ae_recv are not allowed");
	local $cv = AnyEvent->condvar;

	croak "Parameter timeout must be a nonzero real number"
		if (!$timeout or !looks_like_number($timeout));

	# find out where we are
	$iter++;
	my @caller = caller(0);
	local $where = "ae_recv[$iter] at $caller[1]:$caller[2]";

	my $on_timeout = $opt{soft_timeout}
		? sub { $cv->send }
		: sub { $cv->croak("Timeout after $timeout seconds"); };
	my $timer;
	$timeout > 0 and $timer = AnyEvent->timer( after => $timeout,
		cb => $on_timeout,
	);
	_clear_goals();
	$code->();
	return $cv->recv;
	# on exit, $timer is autodestroyed
	# on exit, $cv is restored => destroyed
};

=head2 ae_send ( [@fixed_args] )

Create callback for normal event loop ending.

Returns a sub that feeds its arguments to C<$cv-E<gt>send()>. Arguments given to
the function itself are prepended, as in
C<$cv-E<gt>send(@fixed_args, @callback_args)>.

B<NOTE> that ae_recv will return all sent data "as is" in list context, and
only first argument in scalar context.

May be called as ae_send->( ... ) if you want to stop event loop immediately
(i.e. in a handcrafted callback).

=head2 ae_croak ( [$fixed_error] )

Create callback for event loop termination.

Returns a sub that feeds its first argument to $cv->croak(). If argument is
given, it will be used instead.

=head2 ae_begin ( [ sub { ... } ] )

=head2 ae_end

These subroutines provide ability to wait for several events to complete.

The AnyEvent's condition variable has a counter that is incremented by
C<begin()> and decreased by C<end()>. Optionally, the C<begin()> function
may also set a callback.

Whenever the counter reaches zero, either that callback or just C<send()> is
executed on the condvar.

B<Note>: If you do provide callback and want the event loop to stop there,
consider putting C<ae_send-E<gt>( ... )> somewhere inside the callback.

B<Note>: C<ae_begin()> acts at once, and does NOT return a closure. ae_end,
however, returns a subroutine reference just like C<ae_send>/C<ae_croak> do.

See begin/end section in L<AnyEvent>.

=cut

# set prototypes
sub ae_send (@); ## no critic
sub ae_croak (;$); ## no critic
sub ae_end (); ## no critic