pragma cashscript >= 0.7.1;

// v20220522

// This is an experimental perpetuity contract 
// Beta stage
contract Perpetuity(

 // interval for payouts, in blocks
 int period,

 // lockingBytecode of the beneficiary, 
 // the address receiving payments
 bytes recipientLockingBytecode,

 // extra allowance for administration of contract
 // fees are paid from executors' allowance. 
 int executorAllowance,

 // divisor for the payout, 
 // each payout must be greater than 
 // the input amount held on the contract
 //  divided by this number
 int decay
) {
 function execute() {

  // Check that the first output sends to the recipient
  require(tx.outputs[0].lockingBytecode == recipientLockingBytecode);

  // Check that time has passed and that time locks are enabled
  require(tx.age >= period);
   
  // require the second output to match the active bytecode
  require(tx.outputs[1].lockingBytecode == new LockingBytecodeP2SH(hash160(this.activeBytecode)));


  // Get the input value on the contract
  int currentValue = tx.inputs[this.activeInputIndex].value;

  // The payout is the current value divided by the decay
  int installment = currentValue/decay;

  // Calculate value returned to the contract
  int returnedValue = currentValue - installment - executorAllowance;

  // Check that the outputs send the correct amounts
  require(tx.outputs[0].value >= installment);
  require(tx.outputs[1].value >= returnedValue);
   
 }
}