import {
  fetchTransactionBlockHeight,
  initializeElectrumClient,
} from "@electrum-cash/protocol";

export interface ElectrumServiceConfig {
  host?: string;
  applicationIdentifier?: string;
}

export abstract class BlockchainService {
  abstract hasSeenTransaction(transactionHash: string): Promise<boolean>;
}

/**
 * Small Electrum adapter used by CLI services.
 * Keeps connection logic in one place and exposes a tiny API.
 */
export class ElectrumService {
  private readonly host: string;
  private readonly applicationIdentifier: string;
  private clientPromise?: ReturnType<typeof initializeElectrumClient>;

  constructor(config: ElectrumServiceConfig = {}) {
    this.host =
      config.host ?? process.env["ELECTRUM_HOST"] ?? "bch.imaginary.cash";
    this.applicationIdentifier = "xo-cli";
  }

  private async getClient() {
    if (!this.clientPromise) {
      this.clientPromise = initializeElectrumClient(
        this.applicationIdentifier,
        this.host,
      );
    }

    return this.clientPromise;
  }

  /**
   * Returns true when the transaction is known by Electrum
   * (confirmed or currently in mempool).
   */
  async hasSeenTransaction(transactionHash: string): Promise<boolean> {
    try {
      const client = await this.getClient();
      const height = await fetchTransactionBlockHeight(client, transactionHash);

      // Electrum returns numbers for known transactions
      // (e.g. >0 confirmed, 0/-1 unconfirmed variants).
      return typeof height === "number";
    } catch {
      return false;
    }
  }
}