import { randomBytes } from "crypto";

export interface LNbitsInvoice {
  paymentHash: string;
  paymentRequest: string;
}

export interface LNbitsConfig {
  url: string;
  apiKey: string;
}

const stubPaidInvoices = new Set<string>();

export class LNbitsService {
  private readonly url: string;
  private readonly apiKey: string;
  readonly stubMode: boolean;

  constructor(config?: Partial<LNbitsConfig>) {
    this.url = config?.url ?? process.env.LNBITS_URL ?? "";
    this.apiKey = config?.apiKey ?? process.env.LNBITS_API_KEY ?? "";
    this.stubMode = !this.url || !this.apiKey;
    if (this.stubMode) {
      console.warn("[LNbitsService] No LNBITS_URL/LNBITS_API_KEY — running in STUB mode. Invoices are simulated.");
    }
  }

  async createInvoice(amountSats: number, memo: string): Promise<LNbitsInvoice> {
    if (this.stubMode) {
      const paymentHash = randomBytes(32).toString("hex");
      const paymentRequest = `lnbcrt${amountSats}u1stub_${paymentHash.slice(0, 16)}`;
      console.log(`[stub] Created invoice: ${amountSats} sats — "${memo}" — hash=${paymentHash}`);
      return { paymentHash, paymentRequest };
    }

    const response = await fetch(`${this.url.replace(/\/$/, "")}/api/v1/payments`, {
      method: "POST",
      headers: this.headers(),
      body: JSON.stringify({ out: false, amount: amountSats, memo }),
    });

    if (!response.ok) {
      const body = await response.text();
      throw new Error(`LNbits createInvoice failed (${response.status}): ${body}`);
    }

    const data = (await response.json()) as {
      payment_hash: string;
      payment_request: string;
    };
    return { paymentHash: data.payment_hash, paymentRequest: data.payment_request };
  }

  async checkInvoicePaid(paymentHash: string): Promise<boolean> {
    if (this.stubMode) {
      return stubPaidInvoices.has(paymentHash);
    }

    const response = await fetch(
      `${this.url.replace(/\/$/, "")}/api/v1/payments/${paymentHash}`,
      { method: "GET", headers: this.headers() },
    );

    if (!response.ok) {
      const body = await response.text();
      throw new Error(`LNbits checkInvoice failed (${response.status}): ${body}`);
    }

    const data = (await response.json()) as { paid: boolean };
    return data.paid;
  }

  /** Stub-only helper: mark an invoice as paid for testing/dev flows. */
  stubMarkPaid(paymentHash: string): void {
    if (!this.stubMode) {
      throw new Error("stubMarkPaid called on a real LNbitsService instance");
    }
    stubPaidInvoices.add(paymentHash);
    console.log(`[stub] Marked invoice paid: hash=${paymentHash}`);
  }

  private headers(): Record<string, string> {
    return {
      "Content-Type": "application/json",
      "X-Api-Key": this.apiKey,
    };
  }
}

export const lnbitsService = new LNbitsService();