=head1 NAME

Reaction::Manual::Overview - Orientation in Reaction

=head1 DESCRIPTION

This document aims at describing the modular parts of L<Reaction> and explain
how they are tied together.

=head1 WHAT IS REACTION

Reaction is a L<Catalyst> extension providing you with:

=over 4

=item *

Model mutations abstracted into Action objects.

=item *

Reflection to generate interface models using the Action objects from a L<DBIx::Class>
schema.

=item *

An abstract UI expression system based on L<view|Reaction::UI::View::TT>, 
L<skin|Reaction::UI::Skin>, L<rendering context|Reaction::UI::RenderingContext>,
L<widget|Reaction::UI::Widget> and L<layout set|Reaction::UI::LayoutSet>.

=item *

Stylable via skins. Parts of the skins can be extended and flexibly from large
down to very small parts.

=item *

Full separation of interface rendering structure and templating, making re-usable
extensions even easier.

=bac

=head1 THE BIG PICTURE

          .=========.
          | Request |
          '========='
               |
               |
               v
    .--------------------.   .============================.
    |  Web Application   |   |      Interface Model       |
    | Action Dispatching |<--| Object, Collection, Action |
    '--------------------'   '============================'
               |                            ^
               v                            |
    .====================.        .-------------------.
    |      ViewPort      |        |   Domain Model    |
    | Plain, Collection, |        |  Business Logic,  |
    |   Object, Action   |        | Persistence Layer |
    '===================='        '-------------------'
               |
               v
    .====================.
    |     FocusStack     |
    | Contains ViewPorts |
    '===================='
               |
               v
         .-----------.     .===================.
         |   View    |     | RenderingContext  |
         | HTML, PDF |---->| Template Toolkit  |----.
         '-----------'     '==================='    |
               |                     ^              |
               v                     |              |
   .======================.          |              |
   | LayoutSet / ViewPort |          |              |
   | Layouts: widget, foo |          |              |
   '======================'          |              |
               |                     |              |
               v                     |              |
  .========================.         |              |
  |   Widget / LayoutSet   |         |              |
  | Fragments: widget, foo |---------'              v
  '========================'                  .==========.
                                              | Response |
                                              '=========='

=head1 APPLICATION

A Reaction application is really a L<Catalyst> application under the hood. Reaction
uses reflection to build more flexible and re-usable Catalyst components.

The main application module (usually called C<MyApp> or C<MyApp.pm> in documentation)
looks exactly like a typical Catalyst application module. Reaction's modular architecture
allows it therefor to be integrated into other Catalyst applications, or to integrate
other Catalyst extensions and components itself.

=head1 CONTROLLERS

Usually in Catalyst applications the controller's actions will take their arguments,
maybe modify them or clean them up. After that they are processed by the model and then
stashed away to be later used by the view.

Reactions approach is a bit different. The cleanup and validation of values, and the
involvement of the model are abstracted into a L<Reaction::InterfaceModel::Action>
subclass. Examples for such actions would be C<Create>, C<Update> or C<Delete> in a 
CRUD situation.

Controllers that use Reaction have to inherit from L<Reaction::UI::Controller> or a
subclass of it. Some other useful controller base classes are:

=over

=item *

L<Reaction::UI::Controller::Root> should be the base for the root controller to
every chain of Reaction actions. It will provide a C<base> action you can chain
to which will make sure the L<window viewport|/VIEWPORTS> and 
L<focus stack|/FOCUS STACK> are set up.

=item * 

L<Reaction::UI::Controller::Collection> to ease the creation of components that act
on collections as their model (database results for example). It provides actions
to list and view the collection items.

=item *

L<Reaction::UI::Controller::Collection::CRUD> is a subclass of the above and provides
additional C<create>, C<update>, C<delete> and C<delete_all> actions.

=back

=head1 VIEWPORTS

Viewports represent the components that render your page when combined.

The C<begin> action in L<Reaction::Controller::Root> creates a new L<Reaction::UI::Window>
object and stores it as C<window> in the stash. The L<focus stack|/FOCUSSTACKS> of that
window object is used as the base focus stack for the request.

You can add a new inner viewport to the focus stack with the C<push_viewport> method
available on your controller:

  $controller->push_viewport($viewport_class, %viewport_args);

This will add a new instance of C<$viewport_class> to the current focus stack using
C<%viewport_args> as arguments. For more information on the usage and other options
(for example the C<next_action> option, which redirects afterwards) see
L<Reaction::UI::FocusStack> and L<Reaction::UI::ViewPort>.

You can use the L<Reaction::UI::ViewPort::Action> viewport to build viewports
that perform typical form actions like OK, Apply and Close.

=head1 FOCUSSTACKS

Viewports are pushed onto the current focus stack. The C<end> action in 
L<Reaction::Controller::Root> will C<flush> the L<Reaction::UI::Window>
object stored as C<window> in the stash.

=head1 DOMAIN MODELS

The domain models should be completely decoupled from the application and it's business
logic. Normally, you need to decide whether to put your business logic in your controller
or in your model. Reaction solves this problem by using L<interface models|/INTERFACE MODELS>
as a separation between the two.

If you want your domain model to be reflectable (L<DBIx::Class> for example) you will have
to use L<Moose> to add attribute metadata to those classes.

=head1 INTERFACE MODELS

The interface models contain your business logic. That is, the application specific logic
representing the model your application will use.

An interface model consists of action classes subclassing L<Reaction::InterfaceModel::Action>.
These instances will have both the request context and the target model available and can do
their work in a C<do_apply> method.

To allow your own models to be tied in to reflective controllers like
L<Reaction::Controller::Collection>, you can subclass L<Reaction::InterfaceModel::Object>.
That will provide you with a way to let the viewports introspect the actions that your
interface model defines for this model.

An example of this would be:

  - MyApp::Controller::Foo is a Reaction::Controller::Collection::CRUD 
    for MyApp::Model::Foo
  - The model_name config setting is 'Model::Foo'
  - User calls action MyApp::Controller::Foo->delete_old
  - The 'delete_old' controller action will call 
    $self->basic_model_action($c, \%vp_args)
  - The 'target' option in %vp_args will be asked for an action that
    corresponds with the 'delete_old' controller action
  - An instance of MyApp::Model::Foo::Action::DeleteOld is
    returned
  - This is passed as 'model' to a new instance of
    Reaction::UI::ViewPort::Action which is then pushed
    onto the focus stack.

Form processing as provided by L<Reaction::UI::ViewPort::Action> is a very good
example of Reaction's usefulness; Instead of creating a new dialog for every
form using myriads of helper functions, you provide a controller baseclass
rendering the dialog by introspecting an interface model object with fields and
actions.

Then you just need to create a new controller and interface model for your new
dialog and it just works.

If your model is a L<DBIx::Class::Schema> and contains L<Moose> metadata, you
can let L<Reaction::InterfaceModel::Reflector::DBIC> set up your interface
model objects and actions.

=head1 SKINS, LAYOUTS AND WIDGETS

When you push a viewport onto the focus stack like this:

  $controller->push_viewport('Reaction::UI::ViewPort::SiteLayout');

Reaction will look for a layout file named
C<$search_path/skin/$skin_name/layout/site_layout.tt>. If it can't find it,
it will also look in the base skin and search paths.

You can also provide a specific layout:

  $controller->push_viewport(
    'Reaction::UI::ViewPort::SiteLayout',
    layout => 'my_site_layout',
  );

A new instance of L<Reaction::UI::LayoutSet> will be created using the layout
file. It is then used to determine the class of widget to create. The widget
contains the Perl code counterpart of the templating part in the layout file.

The widget is either determined by the C<=widget> template directive in the
layout file or by the L<Reaction::UI::Skin> object created to represent the
skin.

The details of skins or layouts are documented in L<Reaction::Manual::Templates>.

=head1 SEE ALSO

=over 

=item * L<Reaction::Manual>

=item * L<Reaction::Manual::Intro>

=back

=head1 AUTHORS

See L<Reaction::Class> for authors.

=head1 LICENSE

See L<Reaction::Class> for the license.

=cut
