#!/usr/bin/perl
# Copyright David Leadbeater 2007 <http://dgl.cx>.
# Licensed under the same terms as Perl itself.

# A simple example of using WWW::Facebook::API within a facebook canvas.
# You will need to change the api_key, secret and app_path below to match your
# account. To get an api_key and secret, go to
# http://www.facebook.com/developers/editapp.php?new, choose "Use FBML" and
# enter a unique name for the canvas which you should put into app_path.

use strict;
use CGI;
use WWW::Facebook::API;
use Data::Dumper;

my $facebook = WWW::Facebook::API->new(
    api_key  => "change-me",
    secret   => "change-me",
    app_path => "change-me",
    parse    => 1,
);

our %action_map = (
    ''   => \&index_page,
    info => \&info_page,
);

sub main {

    # Should also work with FastCGI (via CGI::Fast).
    my $q = new CGI;
    print $q->header;

    redirect("Must be called in facebook canvas")
        unless $facebook->canvas->in_fb_canvas($q);

    my $params = $facebook->canvas->validate_sig($q);
    if ( $params->{user} ) {

       # Canvas takes care of setting up a session for us, no need to call the
       # auth methods.
        $facebook->session_key( $params->{session_key} );
    }
    else {

        # User hasn't added app (could reject/display info/whatever)
        # (Or handle later when a user is needed).
    }

    my ( $action, $param ) = ( $q->path_info =~ m!^/(\w+)/?(.*)! );
    if ( my $s = $action_map{$action} ) {
        $s->( $param, $params );
    }
    else {
        div_error("Action unknown");
    }

    # Clear session_key (for if running under FastCGI).
    $facebook->session_key(undef);
}

sub index_page {
    my ( $param, $params ) = @_;

    print "<fb:header/><div style='padding: 20px'>";

# You could do this easier by using <fb:name>, just showing some API stuff here.
    my $name = "You";
    if ($params) {
        my $res =
            $facebook->fql->query( query =>
                "SELECT first_name FROM user WHERE uid=$params->{user}" );
        $name = "Hi $res->[0]->{first_name}, you";
    }
    print "$name ", ( $params ? "have" : "have't" ),
        " added this application. Some <a href='info'>info</a>.";
    if ( !$params ) {
        print "<a href='", $facebook->get_add_url,
            "'>Add this application</a>.";
    }
    print "</div>";
}

sub info_page {
    my ( $param, $params ) = @_;

    print "<fb:header/><div style='padding: 20px'><pre>";
    print Dumper($params);
    print "</pre></div>";
}

sub redirect {
    div_error("Please go <a href='"
            . $facebook->get_app_url
            . "'>to facebook</a>" );
    exit;
}

sub div_error {
    print "<div style='padding: 20px'>", join( "", @_ ), "</div>";
}

main();