Auction.daml

module Auction where
type AuctionId = ContractId Auction
data AuctionStateType
|S0
|S1
|S2
deriving (Eq, Show)

template Auction
state : AuctionStateType
state : AuctionStateType
o : Party
b : Party
b1 : Party
where
signatory o
observer o

choice Withdraw : AuctionId
controller b 
do
assertMsg "Invalid State" (this.state == S1)
create this with
state = S0

choice Bid : AuctionId
controller b 
do
assertMsg "Invalid State" (this.state == S0)
create this with
state = S1

choice End : AuctionId
controller o 
do
assertMsg "Invalid State" (this.state == S1)
create this with
state = S2