Escrow

-- Escrow.daml
module Escrow where

import Daml.Script


template Escrow
  with
    buyer  : Party
    seller : Party
    agent  : Party   -- neutral third party
    asset  : Text
    amount : Decimal
  where
    -- All three must authorize creation.
    signatory buyer, seller, agent
    ensure amount > 0.0

    -- Agent is satisfied: seller gets the funds.
    choice Release : ContractId Receipt
      controller agent
      do
        create Receipt with
          from    = buyer
          to      = seller
          asset; amount
          settled = True

    -- Agent is not satisfied: buyer is refunded.
    choice Cancel : ContractId Receipt
      controller agent
      do
        create Receipt with
          from    = buyer
          to      = buyer   -- refund
          asset; amount
          settled = False

    -- Buyer raises a dispute for the agent to investigate.
    -- nonconsuming: the escrow stays active during dispute resolution.
    nonconsuming choice RaiseDispute : ContractId Dispute
      with reason : Text
      controller buyer
      do
        create Dispute with
          escrowParties = EscrowParties with buyer; seller; agent
          asset; reason


-- ── Supporting types ─────────────────────────────────────
data EscrowParties = EscrowParties
  with
    buyer  : Party
    seller : Party
    agent  : Party
  deriving (Eq, Show)

template Receipt
  with
    from    : Party
    to      : Party
    asset   : Text
    amount  : Decimal
    settled : Bool
  where
    signatory from, to

template Dispute
  with
    escrowParties : EscrowParties
    asset         : Text
    reason        : Text
  where
    signatory escrowParties.buyer
    observer  escrowParties.agent, escrowParties.seller


-- ── Test ─────────────────────────────────────────────────
escrowTest : Script ()
escrowTest = do
  alice <- allocateParty "Alice"  -- buyer
  bob   <- allocateParty "Bob"    -- seller
  carol <- allocateParty "Carol"  -- agent

  -- All three must submit jointly (or use Propose/Accept chain in practice)
  escrowId <- submitMultiParty [alice, bob, carol] do
    createCmd Escrow with
      buyer  = alice
      seller = bob
      agent  = carol
      asset  = "Widget"
      amount = 500.0

  -- Carol releases after verifying delivery
  receiptId <- submit carol do
    exerciseCmd escrowId Release

  Some receipt <- queryContractId alice receiptId
  assert (receipt.settled == True)
  assert (receipt.to == bob)

Key points

Authorization

• submitMultiParty [party1, party2, ...] do submits a transaction authorized by all listed parties simultaneously. This is only available in Script (for testing); in production, multi-signatory creation uses the Propose/Accept pattern.
• A three-party contract means no single party can unilaterally archive it: a useful property for neutral custody.

Design patterns

• nonconsuming on RaiseDispute allows the buyer to file a dispute without destroying the escrow.
• Embedding a named record (EscrowParties) rather than repeating party fields keeps templates clean when many parties share a logical role.
• Receipt has from and to as signatories, so it is a bilateral acknowledgement of the outcome.
• In production systems, the escrow's asset is represented as a ContractId to an actual asset contract, not just a Text label.