import { BufferReader, BufferWriter } from '@node-dlc/bufio';
import { ChannelId } from '@node-dlc/common';

import { MessageType } from '../MessageType';
import { IWireMessage } from './IWireMessage';

/**
 * ShutdownMessage represents the `shutdown` message defined in BOLT #2 of the Lightning
 * Specification. This message can be sent by either node. The scriptPubKey must be a valid P2WPKH,
 * P2WSH, P2SH-P2WPKH, P2SH-P2WSH, or any valid witness script if option_shutdown_anysegwit is
 * negotiated and it should be same as `shutdown_scriptpubkey` value if it was sent during
 * `'open/accept' channel message`. Therefore, if both conditions hold true resulting transaction
 * will propagate to miners. If shutdown is sent by either node, corresponding node should send
 * commitment_signed to commit any outstanding changes before replying shutdown. Once shutdown is
 * sent by both nodes no new HTLCs should be added or accepted by the channel. After successful
 * handshake of shutdown message, fee negotiation and signature sending can begin with
 * `closing_signed` message.
 */
export class ShutdownMessage implements IWireMessage {
  public static type = MessageType.Shutdown;

  /**
   * Deserializes a shutdown message
   * @param buf
   */
  public static deserialize(buf: Buffer): ShutdownMessage {
    const instance = new ShutdownMessage();
    const reader = new BufferReader(buf);

    reader.readUInt16BE(); // read type
    instance.channelId = new ChannelId(reader.readBytes(32));
    const len = reader.readUInt16BE();
    instance.scriptPubKey = reader.readBytes(len);

    return instance;
  }

  /**
   * The type for message. Shutdown = 38
   */
  public readonly type: MessageType = ShutdownMessage.type;

  /**
   * ChannelId generated from the funding transactions outpoint.
   */
  public channelId: ChannelId;

  /**
   * scriptPubKey is used by the sender to get paid, it must be a valid P2WPKH, P2WSH, P2SH-P2WPKH,
   *  P2SH-P2WSH, or any valid witness script if option_shutdown_anysegwit is negotiated and it
   * should be same as `shutdown_scriptpubkey` value if it was sent during `'open/accept' channel
   * message`.
   */
  public scriptPubKey: Buffer;

  /**
   * Serializes the message into a Buffer
   */
  public serialize(): Buffer {
    const writer = new BufferWriter();
    writer.writeUInt16BE(this.type);
    writer.writeBytes(this.channelId.toBuffer());
    writer.writeUInt16BE(this.scriptPubKey.length);
    writer.writeBytes(this.scriptPubKey);
    return writer.toBuffer();
  }
}