3 files changed, 78 insertions, 7 deletions

diff --git a/lib/Plack/Client/Backend.pm b/lib/Plack/Client/Backend.pm
new file mode 100644
index 0000000..3ba7771
--- /dev/null
+++ b/lib/Plack/Client/Backend.pm
@@ -0,0 +1,66 @@
+package Plack::Client::Backend;
+use strict;
+use warnings;
+# ABSTRACT: turns a Plack::Request into a PSGI app
+
+use Carp;
+use Scalar::Util qw(weaken);
+
+use overload '&{}' => sub { shift->as_code(@_) }, fallback => 1;
+
+=head1 SYNOPSIS
+
+  package My::Backend;
+  use base 'Plack::Client::Backend';
+
+  sub app_from_request {
+      my $self = shift;
+      my ($req) = @_;
+      return sub { ... }
+  }
+
+=head1 DESCRIPTION
+
+This is a base class for L<Plack::Client> backends. These backends are handlers
+for a particular URL scheme, and translate a L<Plack::Request> instance into a
+PSGI application coderef.
+
+=cut
+
+=method new
+
+Creates a new backend instance. Takes no parameters by default, but may be
+overridden in subclasses.
+
+=cut
+
+sub new {
+    my $class = shift;
+    bless {}, $class;
+}
+
+=method app_from_request
+
+This method is called with an argument of a L<Plack::Request> object, and
+should return a PSGI application coderef. The Plack::Request object it receives
+contains the actual env hash that will be passed to the application, so
+backends can modify that too, if they need to.
+
+=cut
+
+sub app_from_request {
+    croak "Backends must implement app_from_request";
+}
+
+=method as_code
+
+Returns a coderef which will call L</app_from_request> as a method.
+
+=cut
+
+sub as_code {
+    my $self = shift;
+    return sub { $self->app_from_request(@_) };
+}
+
+1;
diff --git a/lib/Plack/Client/Backend/http.pm b/lib/Plack/Client/Backend/http.pm
index e443385..542c2ce 100644
--- a/lib/Plack/Client/Backend/http.pm
+++ b/lib/Plack/Client/Backend/http.pm
@@ -5,6 +5,8 @@ use warnings;
 
 use Plack::App::Proxy;
 
+use base 'Plack::Client::Backend';
+
 =head1 SYNOPSIS
 
   Plack::Client->new(
@@ -30,11 +32,11 @@ Constructor. Takes no arguments.
 
 sub new {
     my $class = shift;
-    my %params = @_;
+    my $self = $class->SUPER::new(@_);
+
+    $self->{proxy} = Plack::App::Proxy->new->to_app;
 
-    bless {
-        proxy => Plack::App::Proxy->new->to_app,
-    }, $class;
+    return $self;
 }
 
 sub _proxy { shift->{proxy} }
diff --git a/lib/Plack/Client/Backend/psgi_local.pm b/lib/Plack/Client/Backend/psgi_local.pm
index 1da572b..7bb9bcc 100644
--- a/lib/Plack/Client/Backend/psgi_local.pm
+++ b/lib/Plack/Client/Backend/psgi_local.pm
@@ -6,6 +6,8 @@ use warnings;
 use Carp;
 use Plack::Middleware::ContentLength;
 
+use base 'Plack::Client::Backend';
+
 =head1 SYNOPSIS
 
   Plack::Client->new(
@@ -43,13 +45,14 @@ A mapping of local app names to PSGI app coderefs.
 sub new {
     my $class = shift;
     my %params = @_;
+    my $self = $class->SUPER::new(@_);
 
     croak 'apps must be a hashref'
         if ref($params{apps}) ne 'HASH';
 
-    bless {
-        apps => $params{apps},
-    }, $class;
+    $self->{apps} = $params{apps};
+
+    return $self;
 }
 
 sub _apps { shift->{apps} }