This CordApp demonstrate the use encumbrance with a fun example of a Bakery.
In our Bakery, cake of various flavours [vanilla, chocolate, orange, pineapple, strawberry] and produced and sold with an Expiry associated with it.
The Bakery can only sell a cake if the Cake has not expired! and a Buyer can only Consume a cake if it's not Expired.
Encumbrance:
The encumbrance state, if present, forces additional controls over the encumbered state, since the platform checks that the encumbrance state is present as an input in the same transaction that consumes the encumbered state, and the contract code and rules of the encumbrance state will also be verified during the execution of the transaction.
CordApp Info: In this cordApp, encumbered state is the Cake and encumbrance is the Expiry.
This Expiry provides more control over the encumbered state i.e. Cake with an additional time-lock.
In this cordApp Expiry is Covenant i.e. it travels alongside each iteration of the encumbered state- Expiry will follow Cake where ever it goes.
We've 2 Types of Node in this CordApp: Bakery,Buyer
Flows: The below mentioned flows can be used via shell to create, sell and consume cake.
Go to Bakery Node, Create Cake of your choice. provide a flavour, an Id to the Cake and the Expiry of the Cake.
The encumbered state i.e. Cake refers to its encumbrance i.e. Expiry by index, and the referred encumbrance state i.e. Expiry is an output state in a particular position on the same transaction that created the encumbered state i.e. Cake.
In our case the position is 1
Create Cake
flow start CreateCake flavour: "vanilla", cakeId: "1", expireAfterMinutes: 2
Once the cake has been created, it can be sold to buyers by providing the cakeId, a buyer, to which the cake has to be sold
and a boolean includeEncumbrance to demonstrate what would happen if the Cake is Consumed without it's Expiry. It'll throw a missing encumbrance exception.
This can be done by passing includeEncumbrance as false
also, if by any chance the cake has expired, the validation will fail and cake will not be sold.
Sell Cake
flow start SellCakeInitiator cakeId: "1", buyer: "BuyerA", includeEncumbrance: true
Go to BuyerA or BuyerB Node to consume the cake.
The scrumptious cake created by our Corda Bakery can now be consumed by the buyer.
The buyer has to provide the cakeId which it wants to consume. In case, the Cake has expired the Buyer will not be able to consume the cake.
Consume Cake
flow start ConsumeCake cakeId: "1"
Vault Queries: The below queries can be used to get the Cake and Expiry from the vault.
Get All Cakes
run vaultQuery contractStateType: net.corda.demo.sc.state.Cake
Get All Expiry
run vaultQuery contractStateType: net.corda.demo.sc.state.Expiry