parameter unit ;
storage
  (pair
     string # S
     (pair
        timestamp # T
        (pair
           (pair mutez mutez) # P N
           (pair
              (contract unit) # X
              (pair (contract unit) (contract unit)))))) ; # A B
code
  { DUP ; CDAR ; # S
    PUSH string "open" ;
    COMPARE ; NEQ ;
    IF { FAIL } # on "success", "timeout" or a bad init value
       { DUP ; CDDAR ; # T
         NOW ;
         COMPARE ; LT ;
         IF { # Before timeout
              # We compute (P + N) mutez
              PUSH mutez 0 ;
              DIP { DUP ; CDDDAAR } ; ADD ; # P
              DIP { DUP ; CDDDADR } ; ADD ; # N
              # We compare to the cumulated amount
              BALANCE ;
              COMPARE; LT ;
              IF { # Not enough cash, we just accept the transaction
                   # and leave the global untouched
                   CDR ; NIL operation ; PAIR }
                 { # Enough cash, successful ending
                   # We update the global
                   CDDR ; PUSH string "success" ; PAIR ;
                   # We transfer the fee to the broker
                   DUP ; CDDAAR ; # P
                   DIP { DUP ; CDDDAR } ; # X
                   UNIT ; TRANSFER_TOKENS ;
                   # We transfer the rest to A
                   DIP { DUP ; CDDADR ; # N
                         DIP { DUP ; CDDDDAR } ; # A
                         UNIT ; TRANSFER_TOKENS } ;
                   NIL operation ; SWAP ; CONS ; SWAP ; CONS ;
                   PAIR } }
            { # After timeout, we refund
              # We update the global
              CDDR ; PUSH string "timeout" ; PAIR ;
              # We try to transfer the fee to the broker
              BALANCE ; # available
              DIP { DUP ; CDDAAR } ; # P
              COMPARE ; LT ; # available < P
              IF { BALANCE ; # available
                   DIP { DUP ; CDDDAR } ; # X
                   UNIT ; TRANSFER_TOKENS }
                 { DUP ; CDDAAR ; # P
                   DIP { DUP ; CDDDAR } ; # X
                   UNIT ; TRANSFER_TOKENS } ;
              # We transfer the rest to B
              DIP { BALANCE ; # available
                    DIP { DUP ; CDDDDDR } ; # B
                    UNIT ; TRANSFER_TOKENS } ;
              NIL operation ; SWAP ; CONS ; SWAP ; CONS ;
              PAIR } } }