import { HashByteOrder, OutPoint } from '@node-dlc/bitcoin';

/**
 * ChannelId type that that encapsulates an outpoint as a 32-byte value
 * and is used to identify a channel. This type is defined in BOLT 2
 * under the peer protocol. It is defined as combinging the funding_txid
 * and the funding_output_index, using big-endian XOR (meaning the
 * output_index modifies the last two bytes).
 */
export class ChannelId {
  public static fromOutPoint(outpoint: OutPoint): ChannelId {
    const txid = outpoint.txid.serialize(HashByteOrder.RPC);

    if (outpoint.outputIndex > 0xffff) {
      throw new Error('Invalid output index length');
    }

    txid[30] ^= outpoint.outputIndex >> 8;
    txid[31] ^= outpoint.outputIndex & 0xff;

    return new ChannelId(txid);
  }

  constructor(readonly value: Buffer) {}

  /**
   * Converts the ChannelId into a buffer
   */
  public toBuffer(): Buffer {
    return Buffer.from(this.value);
  }

  /**
   * Converts the ChannelId into a hex-encoded string
   */
  public toString(): string {
    return this.toHex();
  }

  /**
   * Converts the ChannelId to a hex-encoded string
   */
  public toHex(): string {
    return this.value.toString('hex');
  }

  /**
   * Returns true if the ChannelIds are byte-wise equal
   * @param other
   */
  public equals(other: ChannelId): boolean {
    return this.value.equals(other.value);
  }
}