NAME

Net::Facebook::Oauth2 - a simple Perl wrapper around Facebook OAuth 2.0 protocol

FACEBOOK GRAPH API VERSION

This module complies to Facebook Graph API version 4.0, the latest at the time of publication, scheduled for deprecation not sooner than August 3rd, 2021.

SYNOPSIS

Somewhere in your application's login process:

use Net::Facebook::Oauth2;

my $fb = Net::Facebook::Oauth2->new(
    application_id     => 'your_application_id', 
    application_secret => 'your_application_secret',
    callback           => 'http://yourdomain.com/facebook/callback'
);

# get the authorization URL for your application
my $url = $fb->get_authorization_url(
    scope   => [ 'email' ],
    display => 'page'
);

Now redirect the user to this $url.

Once the user authorizes your application, Facebook will send him/her back to your application, on the callback link provided above. PLEASE NOTE THAT YOU MUST PRE-AUTHORIZE YOUR CALLBACK URI ON FACEBOOK'S APP DASHBOARD.

Inside that callback route, use the verifier code parameter that Facebook sends to get the access token:

# param() below is a bogus function. Use whatever your web framework
# provides (e.g. $c->req->param('code'), $cgi->param('code'), etc)
my $code = param('code');

use Try::Tiny;  # or eval {}, or whatever

my ($unique_id, $access_token);
try {
    $access_token = $fb->get_access_token(code => $code); # <-- could die!

    # Facebook tokens last ~2h, but you may upgrade them to ~60d if you want:
    $access_token = $fb->get_long_lived_token( access_token => $access_token );

    my $access_data = $fb->debug_token( input => $access_token );
    if ($access_data && $access_data->{is_valid}) {
        $unique_id = $access_data->{user_id};
        # you could also check here for what scopes were granted to you
        # by inspecting $access_data->{scopes}->@*
    }
} catch {
    # handle errors here!
};

If you got so far, your user is logged! Save the access token in your database or session. As shown in the example above, Facebook also provides a unique user_id for this token so you can associate it with a particular user of your app.

Later on you can use that access token to communicate with Facebook on behalf of this user:

my $fb = Net::Facebook::Oauth2->new(
    access_token => $access_token
);

my $info = $fb->get(
    'https://graph.facebook.com/v4.0/me'   # Facebook API URL
);

print $info->as_json;

NOTE: if you skipped the call to debug_token() you can still find the unique user id value with a call to the 'me' endpoint shown above, under $info->{id}

DESCRIPTION

Net::Facebook::Oauth2 gives you a way to simply access FaceBook Oauth 2.0 protocol.

The example folder contains some snippets you can look at, or for more information just keep reading :)

USAGE

`Net::Facebook::Oauth->new( %args )`

Returns a new object to handle user authentication. Pass arguments as a hash. The following arguments are REQUIRED unless you're passing an access_token (see optional arguments below):

application_id

Your application id as you get from facebook developers platform when you register your application
application_secret

Your application secret id as you get from facebook developers platform when you register your application

The following arguments are OPTIONAL:

access_token

If you want to instantiate an object to an existing access token, you may do so by passing it to this argument.
browser

The user agent that will handle requests to Facebook's API. Defaults to LWP::UserAgent, but can be any method that implements the methods get, post and delete and whose response to such methods implements is_success and content.
display

See display under the get_authorization_url method below.
api_version

Use this to replace the API version on all endpoints. The default value is 'v4.0'. Note that defining an api_version parameter together with authorize_url, access_token_url or debug_token_url is a fatal error.
authorize_url

Overrides the default (4.0) API endpoint for Facebook's oauth. Used mostly for testing new versions.
access_token_url

Overrides the default (4.0) API endpoint for Facebook's access token. Used mostly for testing new versions.
debug_token_url

Overrides the default (4.0) API endpoint for Facebook's token information. Used mostly for testing new versions.

`$fb->get_authorization_url( %args )`

Returns an authorization URL for your application. Once you receive this URL, redirect your user there in order to authorize your application.

The following argument is REQUIRED:

callback
```
callback => 'http://example.com/login/facebook/success'
```
The callback URL, where Facebook will send users after they authorize your application. YOU MUST CONFIRM THIS URL ON FACEBOOK'S APP DASHBOARD.

To do that, go to the App Dashboard, click Facebook Login in the right-hand menu, and check the Valid OAuth redirect URIs in the Client OAuth Settings section.

This method also accepts the following OPTIONAL arguments:

scope
```
scope => ['user_birthday','user_friends', ...]
```
Array of Extended permissions as described by the Facebook Oauth API. You can get more information about scope/Extended Permission from

https://developers.facebook.com/docs/facebook-login/permissions/

Please note that requesting information other than name, email and profile_picture will require your app to be reviewed by Facebook!
state
```
state => '123456abcde'
```
An arbitrary unique string provided by you to guard against Cross-site Request Forgery. This value will be returned to you by Facebook, unchanged. Note that, as of Facebook API v3.0, this argument is mandatory, so if you don't provide a 'state' argument, we will default to time().
auth_type

When a user declines a given permission, you must reauthorize them. But when you do so, any previously declined permissions will not be asked again by Facebook. Set this argument to 'rerequest' to explicitly tell the dialog you're re-asking for a declined permission.
display
```
display => 'page'
```
How to display Facebook Authorization page. Defaults to page. Can be any of the following:
- page
  
  This will display facebook authorization page as full page
- popup
  
  This option is useful if you want to popup authorization page as this option tell facebook to reduce the size of the authorization page
- wab
  
  From the name, for wab and mobile applications this option is the best, as the facebook authorization page will fit there :)
response_type
```
response_type => 'code'
```
When the redirect back to the app occurs, determines whether the response data is in URL parameters or fragments. Defaults to code, which is Facebook's default and useful for cases where the server handles the token (which is most likely why you are using this module), but can be also be token, code%20token, or granted_scopes. Note that changing this to anything other than 'code' might change the login flow described in this documentation, rendering calls to get_access_token() pointless. Please see Facebook's login documentation for more information.

`$fb->get_access_token( %args )`

This method issues a GET request to Facebook's API to retrieve the access token string for the specified code (passed as an argument).

Returns the access token string or raises an exception in case of errors (make sure to trap calls with eval blocks or a try/catch module). Note that Facebook's access tokens are short-lived, around 2h of idle time before expiring. If you want to "upgrade" the token to a long lived one (with around 60 days of idle time), use this token to feed the get_long_lived_token() method.

You should call this method inside the route for the callback URI defined in the get_authorization_url method. It receives the following arguments:

code

This is the verifier code that Facebook sends back to your callback URL once user authorize your app, you need to capture this code and pass to this method in order to get the access token.

Verifier code will be presented with your callback URL as code parameter as the following:

http://your-call-back-url.com?code=234er7y6fdgjdssgfsd...

Note that if you have fiddled with the response_type argument, you might not get this parameter properly.

When the access token is returned you need to save it in a secure place in order to use it later in your application. The token indicates that a user has authorized your site/app, meaning you can associate that token to that user and issue API requests to Facebook on their behalf.

To know WHICH user has granted you the authorization (e.g. when building a login system to associate that token with a unique user on your database), you must make a request to fetch Facebook's own unique identifier for that user, and then associate your own user's unique id to Facebook's.

This was usually done by making a GET request to the me API endpoint and looking for the 'id' field. However, Facebook has introduced a new endpoint for that flow that returns the id (this time as 'user_id') and some extra validation data, like whether the token is valid, to which app it refers to, what scopes the user agreed to, etc, so now you are encouraged to call the debug_token() method as shown in the SYNOPSIS.

IMPORTANT: Expect that the length of all access token types will change over time as Facebook makes changes to what is stored in them and how they are encoded. You can expect that they will grow and shrink over time. Please use a variable length data type without a specific maximum size to store access tokens.

`$fb->get_long_lived_token( access_token => $access_token )`

Asks facebook to retrieve the long-lived (~60d) version of the provided short-lived (~2h) access token retrieved from get_access_token(). If successful, this method will return the long-lived token, which you can use to replace the short-lived one. Otherwise, it croaks with an error message, in which case you can continue to use the short-lived version.

See here for the gory details.

`$fb->debug_token( input => $access_token )`

This method should be called right after get_access_token(). It will query Facebook for details about the given access token and validate that it was indeed granted to your app (and not someone else's).

It requires a single argument, input, containing the access code obtained from calling get_access_token.

It croaks on HTTP/connection/Facebook errors, returns nothing if for whatever reason the response is invalid without errors (e.g. no app_id and no user_id), and also if the returned app_id is not the same as your own application_id (pass a true value to skip_check to skip this validation).

If all goes well, it returns a hashref with the JSON structure returned by Facebook.

`$fb->get( $url, $args )`

Sends a GET request to Facebook and stores the response in the given object.

url

Facebook Graph API URL as string. You must provide the full URL.
$args

hashref of parameters to be sent with graph API URL if required.

You can access the response using the following methods:

$response>as_json

Returns response as json object
$response>as_hash

Returns response as perl hashref

For more information about facebook graph API, please check http://developers.facebook.com/docs/api

`$fb->post( $url, $args )`

Send a POST request to Facebook and stores the response in the given object. See the as_hash and as_json methods above for how to retrieve the response.

url

Facebook Graph API URL as string
$args

hashref of parameters to be sent with graph API URL

For more information about facebook graph API, please check http://developers.facebook.com/docs/api

`$fb->delete( $url, $args )`

Send a DELETE request to Facebook and stores the response in the given object. See the as_hash and as_json methods above for how to retrieve the response.

url

Facebook Graph API URL as string
$args

hashref of parameters to be sent with graph API URL

AUTHOR

Mahmoud A. Mehyar, <mamod.mehyar@gmail.com>

CONTRIBUTORS

Big Thanks To

Takatsugu Shigeta @comewalk
Breno G. de Oliveira @garu
squinker @squinker
Valcho Nedelchev @valchonedelchev

COPYRIGHT AND LICENSE

This library is free software; you can redistribute it and/or modify it under the same terms as Perl itself, either Perl version 5.10.1 or, at your option, any later version of Perl 5 you may have available.

To install Net::Facebook::Oauth2, copy and paste the appropriate command in to your terminal.

cpanm

cpanm Net::Facebook::Oauth2

CPAN shell

perl -MCPAN -e shell
install Net::Facebook::Oauth2

For more information on module installation, please visit the detailed CPAN module installation guide.

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NAME

FACEBOOK GRAPH API VERSION

SYNOPSIS

DESCRIPTION

SEE ALSO

USAGE

Net::Facebook::Oauth->new( %args )

$fb->get_authorization_url( %args )

$fb->get_access_token( %args )

$fb->get_long_lived_token( access_token => $access_token )

$fb->debug_token( input => $access_token )

$fb->get( $url, $args )

$fb->post( $url, $args )

$fb->delete( $url, $args )