modified_vesting_lock_validator

use aiken/hash.{Blake2b_224, Hash}
use aiken/transaction/credential.{VerificationKey}
 
type Datum {
  /// POSIX time in second, e.g. 1672843961000
  lock_until: POSIXTime,
  /// POSIX time in second, e.g. 1672843961000 + 2 days
  return_time: POSIXTime,
  /// Owner's credentials
  owner: VerificationKeyHash,
  /// Beneficiary's credentials
  beneficiary: VerificationKeyHash,
}
 
type VerificationKeyHash =
  Hash<Blake2b_224, VerificationKey>
 
type POSIXTime =
  Int

validator {
  fn vesting(datum: Datum, _redeemer: Void, ctx: ScriptContext) {
   // spending eUTxO
    when ctx.purpose is {
      Spend(_) ->
        or([
          must_be_signed_by(ctx.transaction, datum.owner),
          and([
            must_be_signed_by(ctx.transaction, datum.beneficiary),
            must_start_after(ctx.transaction.validity_range, datum.lock_until),
          ]),
          and([
            must_be_signed_by(ctx.transaction, datum.owner),
            must_start_after(ctx.transaction.validity_range, datum.return_time),
          ])
        ])
      _ ->
      False
    }
  }
}

fn must_be_signed_by(transaction: Transaction, vk: VerificationKeyHash) {
  list.has(transaction.extra_signatories, vk)
}
 
fn must_start_after(range: ValidityRange, lower_bound: POSIXTime) {
  when range.lower_bound.bound_type is {
    Finite(now) -> now >= lower_bound
    _ -> False
  }
}