package Plack::Middleware::Conditional;
use strict;
use parent qw(Plack::Middleware);

use Plack::Util::Accessor qw( condition middleware builder );

sub prepare_app {
    my $self = shift;
    $self->middleware( $self->builder->($self->app) );

sub call {
    my($self, $env) = @_;

    my $app = $self->condition->($env) ? $self->middleware : $self->app;
    return $app->($env);



=head1 NAME

Plack::Middleware::Conditional - Conditional wrapper for Plack middleware


  use Plack::Builder;

  builder {
      enable_if { $_[0]->{REMOTE_ADDR} eq '' } 'StackTrace', force => 1;

  # or using the OO interface:
  $app = Plack::Middleware::Conditional->wrap(
      condition  => sub { $_[0]->{REMOTE_ADDR} eq '' },
      builder => sub { Plack::Middleware::StackTrace->wrap($_[0], force => 1) },


Plack::Middleware::Conditional is a piece of meta-middleware, to run a
specific middleware component under runtime conditions. The goal of
this middleware is to avoid baking runtime configuration options in
individual middleware components, and rather share them as another
middleware component.


Note that some of the middleware component names are just made up for
the explanation and might not exist.

  # Minify JavaScript if the browser is Firefox
  enable_if { $_[0]->{HTTP_USER_AGENT} =~ /Firefox/ } 'JavaScriptMinifier';

  # Enable Stacktrace when being accessed from the local network
  enable_if { $_[0]->{REMOTE_ADDR} =~ /^10\.0\.1\.*/ } 'StackTrace';

  # Work with other conditional setter middleware:
  # Transcode Jpeg on the fly for mobile clients
  builder {
      enable 'MobileDetector';
      enable_if { $_[0]->{'plack.mobile_detected'} }
        'TranscodeJpeg', max_size => 30_000;

Note that in the last example I<MobileDetector> should come first
because the conditional check runs in I<pre-run> conditions, which is
from outer to inner: that is, from the top to the bottom in the
Builder DSL code.

=head1 AUTHOR

Tatsuhiko Miyagawa

Steve Cook

=head1 SEE ALSO