Bond Contract

-- Bond.daml
module Bond where

import DA.Date
import Daml.Script


template Bond
  with
    issuer       : Party
    owner        : Party
    isin         : Text       -- unique instrument identifier
    principal    : Decimal    -- face value
    couponRate   : Decimal    -- annual rate, e.g. 0.05 for 5%
    maturityDate : Date
    currency     : Text
  where
    signatory issuer
    observer  owner
    ensure
      principal > 0.0
      && couponRate >= 0.0
      && couponRate <= 1.0

    key (issuer, isin) : (Party, Text)
    maintainer key._1

    -- Owner transfers the bond to a new party.
    choice Transfer : ContractId Bond
      with newOwner : Party
      controller owner
      do create this with owner = newOwner

    -- Issuer makes a coupon payment.
    -- In a real system this would exercise a Cash token to make payment.
    -- Here we record the event and keep the bond active.
    nonconsuming choice PayCoupon : ContractId CouponPayment
      with
        paymentDate : Date
        amount      : Decimal
      controller issuer
      do
        assertMsg "coupon amount must be positive" (amount > 0.0)
        create CouponPayment with
          issuer; owner; isin; amount; paymentDate; currency

    -- Issuer redeems the bond at maturity, returning principal.
    choice Mature : ContractId MaturityReceipt
      with today : Date
      controller issuer
      do
        assertMsg "bond has not yet matured" (today >= maturityDate)
        create MaturityReceipt with
          issuer; owner; isin; principal; currency; maturityDate


template CouponPayment
  with
    issuer      : Party
    owner       : Party
    isin        : Text
    amount      : Decimal
    paymentDate : Date
    currency    : Text
  where
    signatory issuer
    observer  owner


template MaturityReceipt
  with
    issuer       : Party
    owner        : Party
    isin         : Text
    principal    : Decimal
    currency     : Text
    maturityDate : Date
  where
    signatory issuer
    observer  owner


-- ── Test ─────────────────────────────────────────────────
bondTest : Script ()
bondTest = do
  bank  <- allocateParty "Bank"
  alice <- allocateParty "Alice"

  let maturity = date 2026 Dec 31

  bondId <- submit bank do
    createCmd Bond with
      issuer       = bank
      owner        = alice
      isin         = "XS0000000001"
      principal    = 10000.0
      couponRate   = 0.05
      maturityDate = maturity
      currency     = "USD"

  -- Bank pays a coupon
  couponId <- submit bank do
    exerciseCmd bondId PayCoupon with
      paymentDate = date 2026 Jun 30
      amount      = 250.0   -- 5% annual, semi-annual payment

  Some coupon <- queryContractId alice couponId
  assert (coupon.amount == 250.0)

  -- Bank matures the bond
  receiptId <- submit bank do
    exerciseCmd bondId Mature with today = date 2027 Jan 1

  Some receipt <- queryContractId alice receiptId
  assert (receipt.principal == 10000.0)

Key points

Date utilities

• DA.Date exports date y m d : Year -> Month -> Day -> Date for constructing date literals. Month is an enum: Jan, Feb, ..., Dec.

Bond lifecycle

• nonconsuming choice PayCoupon keeps the bond alive after payment: coupon payments happen multiple times over the bond's life.
• Mature is consuming: it archives the bond and creates a MaturityReceipt, modelling redemption.

Production notes

• The isin key ensures only one active bond contract per issuer per instrument code.
• In production DAML Finance, CouponPayment would be replaced by an actual settlement of a cash instrument. This example uses a receipt pattern for clarity.
• couponRate is stored on the contract so the issuer can compute payment amounts off-chain; the amount is passed into PayCoupon as an argument.