Editing Portal:Payment Processing

==Introduction==
It is very easy to accept payments online using Perl; as this is a fundamental activity for any sustainable enterprise we shall endeavor to cover it as completely as possible here.

==Perl Modules==
There are modules on CPAN for handingling things like PayPal "IPNs"

==Example Dancer Handler for PayPal IPNs==
Paypal IPNs are old school webhooks that tell Paypal to hit an URL whenever you receive a payment. We will not cover how to set this up through PP, but here's a sketch snippet that will create a Dancer2 app that handles IPNs.
 package Application::ppipnd;
 
 use Dancer2;
 use HTTP::Tiny   ();
 use Util::H2O::More qw/h2o/;
 
 our $VERSION = '1.0';
 
 #my $PP_WEBSRC = q{<nowiki>https://www.sandbox.paypal.com/patchlodge/webscr}</nowiki>;
 my $PP_WEBSRC = q{<nowiki>https://www.paypal.com/cgi-bin/webscr}</nowiki>;
 
 post '/ipn' => sub {
     my %body   = params('body');
     my $http   = HTTP::Tiny->new;
 
     # handshake back to PayPal (this here you confirm it is actually from PayPal)
     my $resp = $http->post( $PP_WEBSRC, {%body} );
 
     #... if you trust what $resp tells you, then process the request
     
     # save raw body
     $body{raw} = JSON::XS::encode_json( \%body );
      
      
     # now process IPN (e.g.,...)
     my $ipn = h2o \%body, qw/raw txn_type subscr_id parent_txn_id option_selection1 option_selection2 txn_id first_name/;
 
     # hard pass if {txn_type} is not defined in %body
     if ( not $ipn->txn_type ) {
         printf qq{%s: %s request that contained no txn_type field. Replied as Teapot (418).\n}, INFO, REJECTED;
         status q{i_m_a_teapot}; #418
         send_as html => q{I'm a teapot.};
     }
 
     return q{ok}; # 200 OK is also required by PayPal's IPN sender to assume success
 };
Notes:

* PayPal IPNs require HTTPS
* There is an IPN generator to test at PayPal's developer site, but you can also employ a curl script, provided you get all the IPN variables correct; see an example [https://github.com/The-Perl-Cottage-Guild/ppipnd/blob/master/curl-tests/basic-account-lifecycle.sh\ here].