// SPDX-License-Identifier: AGPL-3.0

/**

* @title Hash Time Lock Contract (HTLC)

*

* @author Meheret Tesfaye Batu <[email protected]>

*

* HTLC -> A Hash Time Lock Contract is essentially a type of payment in which two people

* agree to a financial arrangement where one party will pay the other party a certain amount

* of cryptocurrencies, such as Bitcoin or Vapor assets.

* However, because these contracts are Time-Locked, the receiving party only has a certain

* amount of time to accept the payment, otherwise the money can be returned to the sender.

*

* Hash-Locked -> A Hash locked functions like “two-factor authentication” (2FA). It requires

* the intended recipient to provide the correct secret passphrase to withdraw the funds.

*

* Time-Locked -> A Time locked adds a “timeout” expiration date to a payment. It requires

* the intended recipient to claim the funds prior to the expiry. Otherwise, the transaction

* defaults to enabling the original sender of funds to withdraw a refund.

*/

contract HTLC (secret_hash: Hash, recipient_public_key: PublicKey, sender_public_key: PublicKey, endblock: Integer) locks valueAmount of valueAsset {

clause withdraw (preimage: String, signature: Signature) {

verify sha256(preimage) == secret_hash

verify checkTxSig(recipient_public_key, signature)

unlock valueAmount of valueAsset

}

clause refund (signature: Signature) {

verify above(endblock)

verify checkTxSig(sender_public_key, signature)

unlock valueAmount of valueAsset

}

}