Specs for VendTTP Client-to-Server Communication

vendttp_comm_specs.txt

Specs for VendTTP Client-to-Server Communication
revision 3.3
==============================================================
 
Notes:
* <"asdf"|"uiop"> means either "asdf" or "uiop"
* ( ) means attibute may be null
* ~ prefix means non-literal placeholder value
* all requests should be shorter than 512 characters (this may be removed in the future)
* the client should not send a request before receiving the response to a previous non-stand-alone request

new guest log-in request (stand-alone):
{
 "type" : "guest"
}
When logged in as guest, any rfid login response will be ignored, because logging out of guest requires user to confirm donation of guest balance.

#rfid login "response" (stand-alone):
{
 "type" : "log in",
 "username" : ~"George Matter",
 "balance" : ~5
}

#inventory request with key-exchange (a null key is treated like an expired key)
{
 "type" : "inventory",
 ("key" : ~"asdf")
}

#inventory response ("categories" attribute will be null if key was valid)
{
 "type" : "inventory",
 "inventory" : {"key" : ~"uiop",
                ("categories" : [
                                 {
                                  "name" : ~"cat1",
                                  "items" : [
                                             {
                                              "vendId"   : ~"00",
                                              "price"    : ~.75,
                                              "quantity" : ~12,
                                              "name"     : ~"Fruit Snacks"
                                             },
                                             ...
                                            ]
                                 },
                                 ...
                                ])
               }
}
 
#logout request (stand-alone):
{
 "type" : "log out"
}
 
#vend request
{
 "type" : "vend",
 "vendId"  : ~"00"
}
 
#vending succeeded
{
 "type" : "vend success",
 "vendId" : ~"00",
 "balance" : ~4.25
}
 
#vending failed because user had insufficient funds, item was sold out, or item was not found in database, or an error occurred.
{
 "type" : "vend failure",
 "vendId" : ~"00",
 "reason" : <"balance"|"quantity"|"vendId"|"error">
}
 
#when user inserts cash (stand-alone):
{
 "type" : "balance update",
 "balance" : ~5.25
}