Escrow with collateral

metadata.json

{"valueParameterDescriptions":[["Collateral amount","The amount of Lovelace to be deposited by both parties at the start of the contract to serve as an incentive for collaboration."],["Price","The amount of Lovelace to be paid by the *Buyer* as part of the exchange."]],"slotParameterDescriptions":[["Collateral deposit by seller timeout","The deadline by which the *Seller* must deposit the *Collateral amount* in the contract."],["Deposit of collateral by buyer timeout","The deadline by which the *Buyer* must deposit the *Collateral amount* in the contract."],["Deposit of price by buyer timeout","The deadline by which the *Buyer* must deposit the *Price* in the contract."],["Dispute by buyer timeout","The deadline by which, if the *Buyer* has not opened a dispute, the *Seller* will be paid."],["Seller's response timeout","The deadline by which, if the *Seller* has not responded to the dispute, the *Buyer* will be refunded."]],"roleDescriptions":[["Buyer","The party that pays for the item on sale."],["Seller","The party that sells the item and gets the money if the exchange is successful."]],"contractType":"ES","contractName":"Escrow with collateral","contractDescription":"Regulates a money exchange between a *Buyer* and a *Seller* using a collateral from both parties to incentivize collaboration. If there is a disagreement the collateral is burned.","choiceDescriptions":[["Confirm problem","Acknowledge that there was a problem and a refund must be granted."],["Dispute problem","The *Seller* disagrees with the *Buyer* about the claim that something went wrong and the collateral will be burnt."],["Everything is alright","The exchange was successful and the *Buyer* agrees to pay the *Seller*."],["Report problem","The *Buyer* claims not having received the product that was paid for as agreed and would like a refund."]]}

playground.js

    /* We can set explicitRefunds true to run Close refund analysis
       but we get a shorter contract if we set it to false */
    const explicitRefunds: Boolean = false;

    const buyer: Party = Role("Buyer");
    const seller: Party = Role("Seller");
    const burnAddress: Party = PK("0000000000000000000000000000000000000000000000000000000000000000");

    const price: Value = ConstantParam("Price");
    const collateral: Value = ConstantParam("Collateral amount");

    const sellerCollateralTimeout: Timeout = SlotParam("Collateral deposit by seller timeout");
    const buyerCollateralTimeout: Timeout = SlotParam("Deposit of collateral by buyer timeout");
    const depositTimeout: Timeout = SlotParam("Deposit of price by buyer timeout");
    const disputeTimeout: Timeout = SlotParam("Dispute by buyer timeout");
    const answerTimeout: Timeout = SlotParam("Seller's response timeout");

    function depositCollateral(party: Party, timeout: Timeout, timeoutContinuation: Contract, continuation: Contract): Contract {
        return When([Case(Deposit(party, party, ada, collateral), continuation)],
            timeout,
            timeoutContinuation);
    }

    function burnCollaterals(continuation: Contract): Contract {
        return Pay(seller, Party(burnAddress), ada, collateral,
            Pay(buyer, Party(burnAddress), ada, collateral,
                continuation));
    }

    function deposit(timeout: Timeout, timeoutContinuation: Contract, continuation: Contract): Contract {
        return When([Case(Deposit(seller, buyer, ada, price), continuation)],
            timeout,
            timeoutContinuation);
    }

    function choice(choiceName: string, chooser: Party, choiceValue: SomeNumber, continuation: Contract): Case {
        return Case(Choice(ChoiceId(choiceName, chooser),
            [Bound(choiceValue, choiceValue)]),
            continuation);
    }

    function choices(timeout: Timeout, chooser: Party, timeoutContinuation: Contract, list: { value: SomeNumber, name: string, continuation: Contract }[]): Contract {
        var caseList: Case[] = new Array(list.length);
        list.forEach((element, index) =>
            caseList[index] = choice(element.name, chooser, element.value, element.continuation)
        );
        return When(caseList, timeout, timeoutContinuation);
    }

    function sellerToBuyer(continuation: Contract): Contract {
        return Pay(seller, Account(buyer), ada, price, continuation);
    }

    function refundSellerCollateral(continuation: Contract): Contract {
        if (explicitRefunds) {
            return Pay(seller, Party(seller), ada, collateral, continuation);
        } else {
            return continuation;
        }
    }

    function refundBuyerCollateral(continuation: Contract): Contract {
        if (explicitRefunds) {
            return Pay(buyer, Party(buyer), ada, collateral, continuation);
        } else {
            return continuation;
        }
    }

    function refundCollaterals(continuation: Contract): Contract {
        return refundSellerCollateral(refundBuyerCollateral(continuation));
    }

    const refundBuyer: Contract = explicitRefunds ? Pay(buyer, Party(buyer), ada, price, Close) : Close;

    const refundSeller: Contract = explicitRefunds ? Pay(seller, Party(seller), ada, price, Close) : Close;

    const contract: Contract =
        depositCollateral(seller, sellerCollateralTimeout, Close,
            depositCollateral(buyer, buyerCollateralTimeout, refundSellerCollateral(Close),
                deposit(depositTimeout, refundCollaterals(Close),
                    choices(disputeTimeout, buyer, refundCollaterals(refundSeller),
                        [{ value: 0n, name: "Everything is alright", continuation: refundCollaterals(refundSeller) },
                        {
                            value: 1n, name: "Report problem",
                            continuation:
                                sellerToBuyer(
                                    choices(answerTimeout, seller, refundCollaterals(refundBuyer),
                                        [{ value: 1n, name: "Confirm problem", continuation: refundCollaterals(refundBuyer) },
                                        { value: 0n, name: "Dispute problem", continuation: burnCollaterals(refundBuyer) }]))
                        }]))));

    return contract;

playground.marlowe.json

{}