NAME
    Abilities - Simple, hierarchical user authorization for web
    applications, with optional support for plan-based (paid) services.

VERSION
    version 0.5

SYNOPSIS
            package User;
        
            use Moose; # or Moo
            with 'Abilities';
        
            # ... define required methods ...
        
            # somewhere else in your code:

            # get a user object that consumed the Abilities role
            my $user = MyApp->get_user('username'); # $user is a User object

            # check if the user is able to do something
            if ($user->can_perform('something')) {
                    do_something();
            } else {
                    die "Hey you can't do that, you can only do " . join(', ', keys %{$user->abilities});
            }

DESCRIPTION
    Abilities is a simple yet powerful mechanism for authorizing users of
    web applications (or any applications) to perform certain actions in the
    application. This is an extension of the familiar role-based access
    control that is common in various systems and frameworks like Catalyst
    (See Catalyst::Plugin::Authorization::Roles for the role-based
    implementation and Catalyst::Plugin::Authorization::Abilities for the
    ability-based implementation that inspired this module).

    As opposed to role-based access control - where users are allowed access
    to a certain feature (here called 'action') only through their
    association to a certain role that is hard-coded into the program - in
    ability-based acccess control, a list of actions is assigned to every
    user, and they are only allowed to perform these actions. Actions are
    not assigned by the developer during development, but rather by the
    end-user during deployment. This allows for much more flexibility, and
    also speeds up development, as you (the developer) do not need to think
    about who should be allowed to perform a certain action, and can easily
    grant access later-on after deployment (assuming you're also the
    end-user).

    Abilities to perform certain actions can be given to a user
    specifically, or via roles the user can assume (as in role-based access
    control). For example, if user 'user01' is a member of role 'admin', and
    this user wishes to perform some action, for example 'delete_foo', then
    they will only be able to do so if the 'delete_foo' ability was given to
    either the user itself or the 'admin' role itself. Furthermore, roles
    can recursively inherit other roles; for example, the role 'mega_mods'
    can inherit the roles 'mods' and 'editors'. Users of the 'mega_mods'
    role will assume all actions owned by the 'mods' and 'editors' roles.

    A commonly known use-case for this type of access control is message
    boards, where the administrator might wish to create roles with certain
    actions and associate users with the roles (more commonly called 'user
    groups'); for example, the admin can create an 'editor' role, giving
    users of this role the ability to edit and delete posts, but not any
    other administrative action. So in essence, this type of access control
    relieves the developer of deciding who gets to do what and passes these
    decisions to the end-user, which might actually be necessary in certain
    situations.

    The "Abilities" module is implemented as a Moo role (which makes it
    compatible with Moose code). In order to be able to use this mechanism,
    applications must implement a user management system that will consume
    this role. More specifically, a user class and a role class must be
    implemented, consuming this role. Entities is a reference implementation
    that can be used by applications, or just taken as an example of an
    ability-based authorization system. Entities::User and Entities::Role
    are the user and role classes that consume the Abilities role in the
    Entities distribution.

  CONSTRAINTS
    Generally, an ability is a yes/no option. Either the user can or can't
    perform a specific action. At times, this might not be flexible enough,
    and the user's ability to perform a certain action should be
    constrained. For example, a user might be granted the ability to edit
    posts in a blog, but this ability should be constrained to the user's
    posts only. The user is not to be allowed to edit posts created by other
    users. "Abilities" supports constraints by allowing to set a name-based
    constraint when granting a user/role a certain ability. Then, checking
    the user's ability to perform an action can include the constraint, for
    example:

            if ($post->{user_id} eq $user->id && $user->can_perform('edit_posts', 'only_his')) {
                    # allow
            } else {
                    # do not allow
            }

    Here, the "Abilities" module allows you to check if the user's ability
    is constrained, but the responsibility for making sure the constraint is
    actually relevant to the case is left to you. In the above example, it
    is the application that checks if the post the user is trying to edit
    was created by them, not the "Abilities" module.

  (PAID) SUBSCRIPTION-BASED WEB SERVICES
    Apart from the scenario described above, this module also provides
    optional support for subscription-based web services, such as those
    where customers subscribe to a certain paid (or free, doesn't matter)
    plan from a list of available plans (GitHub is an example of such a
    service). This functionality is also implemented as a Moo(se) role, in
    the Abilities::Features module provided with this distribution. Read its
    documentation for detailed information.

REQUIRED METHODS
    Classes that consume this role are required to implement the following
    methods:

  roles()
    Returns a list of all role names that a user object belongs to, or a
    role object inherits from.

    Example return structure:

            ( 'moderator', 'supporter' )

    NOTE: In previous versions, this method was required to return an array
    of role objects, not a list of role names. This has been changed in
    version 0.3.

  actions()
    Returns a list of all action names that a user object has been
    explicitely granted, or that a role object has been granted. If a
    certain action is constrained, then it should be added to the list as an
    array reference with two items, the first being the name of the action,
    the second being the name of the constraint.

    Example return structure:

            ( 'create_posts', ['edit_posts', 'only_his'], 'comment_on_posts' )

    NOTE: In previous versions, this method was required to return an array
    of action objects, not a list of action names. This has been changed in
    version 0.3.

  is_super()
    This is a boolean attribute that both user and role objects should have.
    If a user/role object has a true value for this attribute, then they
    will be able to perform any action, even if it wasn't granted to them.

  get_role( $name )
    This is a method that returns the object of the role named $name.

PROVIDED METHODS
    Classes that consume this role will have the following methods available
    to them:

  can_perform( $action, [ $constraint ] )
    Receives the name of an action, and possibly a constraint, and returns a
    true value if the user/role can perform the provided action.

  assigned_role( $role_name )
    This method receives a role name and returns a true value if the
    user/role is a direct member of the provided role. Only direct
    membership is checked, so the user/role must be specifically assigned to
    the provided role, and not to a role that inherits from that role (see
    "does_role( $role )" instead).

  does_role( $role_name )
    Receives the name of a role, and returns a true value if the user/role
    inherits the abilities of the provided role. This method takes
    inheritance into account, so if a user was directly assigned to the
    'admins' role, and the 'admins' role inherits from the 'devs' role, then
    "does_role('devs')" will return true for that user (while
    "assigned_role('devs')" returns false).

  abilities()
    Returns a hash reference of all the abilities a user/role object can
    perform, after consolidating abilities inherited from roles (including
    recursively) and directly granted. Keys in the hash-ref will be names of
    actions, values will be 1 (for yes/no actions) or a single-item
    array-ref with the name of a constraint (for constrained actions).

UPGRADING FROM v0.2
    Up to version 0.2, "Abilities" required the "roles" and "actions"
    attributes to return objects. While this made it easier to calculate
    abilities, it made this system a bit less flexible.

    In version 0.3, "Abilities" changed the requirement such that both these
    attributes need to return strings (the names of the roles/actions). If
    your implementation has granted roles and actions stored in a database
    by names, this made life a bit easier for you. On other implementations,
    however, this has the potential of requiring you to write a bit more
    code. If that is the case, I apologize, but keep in mind that you can
    still store granted roles and actions any way you want in a database
    (either by names or by references), just as long as you correctly
    provide "roles" and "actions".

    Unfortunately, in both versions 0.3 and 0.4, I made a bit of a mess that
    rendered both versions unusable. While I documented the "roles"
    attribute as requiring role names instead of role objects, the actual
    implementation still required role objects. This has now been fixed, but
    it also meant I had to add a new requirement: consuming classes now have
    to provide a method called "get_role()" that takes the name of a role
    and returns its object. This will probably means loading the role from a
    database and blessing it into your role class that also consumes this
    module.

    I apologize for any inconvenience this might have caused.

AUTHOR
    Ido Perlmuter, "<ido at ido50 dot net>"

BUGS
    Please report any bugs or feature requests to "bug-abilities at
    rt.cpan.org", or through the web interface at
    <http://rt.cpan.org/NoAuth/ReportBug.html?Queue=Abilities>. I will be
    notified, and then you'll automatically be notified of progress on your
    bug as I make changes.

SUPPORT
    You can find documentation for this module with the perldoc command.

            perldoc Abilities

    You can also look for information at:

    *   RT: CPAN's request tracker

        <http://rt.cpan.org/NoAuth/Bugs.html?Dist=Abilities>

    *   AnnoCPAN: Annotated CPAN documentation

        <http://annocpan.org/dist/Abilities>

    *   CPAN Ratings

        <http://cpanratings.perl.org/d/Abilities>

    *   Search CPAN

        <http://search.cpan.org/dist/Abilities/>

LICENSE AND COPYRIGHT
    Copyright 2010-2013 Ido Perlmuter.

    This program is free software; you can redistribute it and/or modify it
    under the terms of either: the GNU General Public License as published
    by the Free Software Foundation; or the Artistic License.

    See http://dev.perl.org/licenses/ for more information.

