The bilateral trade agreement pattern

Intent

Creation of a smart contract where 1 instance of the smart contract will allow for exactly 1 trade with another entity, where the entity that created the smart contract determines what other entity it will trade with.

Consequences

Structure

Participants

Implementation

const start = zcf => {
  const firstOfferOfferHandler = creatorSeat => {
    assertProposalShape(creatorSeat, /*some shape*/);
    const counterOfferOfferHandler = counterPartySeat => {
      //some reallocation
      //exit all seats
      //return success message
    };
    const counterPartyInvitation = zcf.makeInvitation(
      counterOfferOfferHandler,
      'counterOffer',
      /*some shape*/
    );
    return counterPartyInvitation;
  };
  const creatorInvitation = zcf.makeInvitation(
    firstOfferOfferHandler,
    'firstOffer',
  );
  return { creatorInvitation };
};
harden(start);
export { start };

The smart contract returns a single creatorInvitation. The offer handler linked to the creatorInvitation will return a counterPartyInvitation which is an invitation for the counterparty. Thus: when the creator uses this creatorInvitation in an offer and gets a creatorSeat in return, the creator will be able to call the getOfferResult method on the creatorSeat in order to obtain the counterPartyInvitation. The creator can then start looking for a counterparty who is interested to participate in the trade. Once this counterparty has been found, the creator can send the counterPartyInvitation to this entity. In the offer handler of the counterPartyInvitation, a reallocation happens, each seat is exited and a string message is returned. Thus, when the counterparty uses the counterPartyInvitation in an offer, the trade will be completed. Note that optional assertions about the shape of each proposal can be made.

Known uses