[Omaha.pm] Re: LWP form posts

[Jay Hannah]

On Sep 9, 2004, at 9:26 AM, Michael D. Maynard wrote:
> I have looked at WWW::Mechanize and I think that it might do what I am 
> trying to do, however, it is not installed on the 3rd party server 
> that the application will run on.  I am looking into getting it 
> installed or having them switch to my server.
>
> I am doing a PayPal IPN integration into our shopping cart system.  I 
> have the callback working (as well as it can, I guess.  From what I 
> have read in the forum, it is pretty buggy.).  The way it works is you 
> do a from post to their server with the merchant's info and the 
> transactions details, the user logs into PayPal, does their thing and 
> PayPal sends them back to your site and updates you with the payment 
> status.
>
> Server A is my server w/ Perl 5.8.  Server B is 3rd party, but we 
> won't worry about them for now.  Server C is PayPal (Apache/1.3.27 
> (Unix) mod_ssl/2.8.12 OpenSSL/0.9.7a) scripting language unknown.  
> When I do a standard HTML form post everything works fine, except I 
> would like to do the form post with PERL and save the user a click 
> (Gee, how thoughtful...).  When I use Perl from Server A to Server C, 
> the post goes OK.  Server C responds with HTML, the PayPal login page. 
>  They have everything written as relative to Server C so you get 
> broken images and JavaScript errors because Server A is now displaying 
> the content.
>
> Every example that I have found for LWP assumes that Server A will be 
> handling the content, but I need to have Server C handle the content 
> returned.  Authorize.net and PayFuse work great because they simple 
> reply with a Pass/Fail status, but PayPal requires login, etc. that 
> has to be done through their srever.
>
> Clear as mud?  Any thoughts?

Hmmm... We left out one computer, right?

D = web browser of customer who's actually needs to log into PayPal and 
authorize the transaction.

So, what you're trying to do is:

1) D -> A  Customer is cruising around on your server w/ their browser. 
They do something and now they need to pay $$$ w/ PayPal
2) A -> C  You submit whatever step 1 of PayPal IPN is to PayPal to 
initiate the payment
3) C -> A  PayPal throws HTML back to your server saying "Hi PayPal 
customer! Log in!"
4) A -> D  You redirect that HTML out to your customer's web browser so 
the human can, indeed, log into PayPal.
5) D -> C  Your customer is now clicking around on PayPal's server, 
logging in, pushing buttons, whatever. Eventually they Do The Right 
Thing, authorizing you to be paid. PayPal now redirects the customer 
back to your server.
6) D -> A  Customer is cruising around on your server again. You're 
paid, everybody's happy. Capitalism continues to make the world go 
'round.

Is that right, or am I drunk?

If that's what you're trying to do, then probably the trickiest thing 
is getting steps 1-4 to flow in a single run of your Perl program. That 
program would probably flow like this:

orderform.pl
- Customer has just clicked something. You need their money now. You 
know their PayPal login ID and whatever else you need for PayPal IPN.
   - orderform.pl uses LWP or WWW::Mechanize or whatever to hit PayPal 
IPN on the back end. The customer has no idea this is occuring.
   - PayPal responds with a bunch of HTML which happens to be a login 
page. You slurp that HTML into $paypal_response, but you still haven't 
returned anything to the customer. They still have no idea anything is 
going on.
- orderform.pl examines $paypal_response. If it's a login page, then 
we're happy. Spit $paypal_response out to STDOUT. This is the first and 
only thing the customer web browser ever saw.
- orderform.pl exits, safe in the knowledge that PayPal will do the 
Right Thing and re-direct the customer back to orderform.pl (or 
whatever URL you want) whenever they're done clicking around in PayPal.

Does that help? -ponder-

Take care,

j