@node-dlc/core/lib/lightning/Htlc.ts

DLC Core

import { Value } from '@node-dlc/bitcoin';

import { HtlcDirection } from './HtlcDirection';

/**
 * An HTLC (hashed time-locked contract) is part of the transfer
 * layer of the Lightning network. HTLCs are used to trustlessly offer
 * a payment to a counterparty if they are able to provide a preimage
 * of the hash. The offeror can claw back funds after an expiration
 * period (absolute lock time) if the recipient is unable to provide
 * the preimage for the contract. HTLCs are used in Lightning for both
 * initiating payments to a peer directly and as part of forwarding
 * payments.
 */
export class Htlc {
  /**
   * The preimage of the payment hash using SHA256.
   */
  public paymentPreimage: Buffer;

  /**
   * Constructs an HTLC with associated information
   * @param htlcId Identifier for the HTLC is a counter maintained
   * per-channel, per-peer. It starts at zero and is incremented when
   * an HTLC is offered. This value is used when sending channel
   * related messages to disambiguate HTLCs that may share the same
   * preimage.
   *
   * @param direction Direction, from your node's perspective, that
   * indicates if the HTLC was offered or received.
   *
   * @param value The value of the HTLC in millisatoshi.
   *
   * @param cltvExpiry The absolutely blocktime expiry of the HTLC.
   * The value must be under 500,000,000 to ensure it is a block-based
   * locktime. After this timeout has expired, the offeror can perform
   * a forced resolution on-chain.
   *
   * @param paymentHash The 32-byte hash of the preimage. Knowledge of
   * the preimage is irrevocable and considers payment complete.
   */
  constructor(
    readonly htlcId: bigint,
    readonly direction: HtlcDirection,
    readonly value: Value,
    readonly cltvExpiry: number,
    readonly paymentHash: Buffer,
    paymentPreimage?: Buffer,
  ) {
    this.paymentPreimage = paymentPreimage;
  }
}