/**
 * Public invoice endpoints.
 *
 *   POST /api/invoice       {listing_id}         → create a fresh invoice
 *   GET  /api/invoice/<id>                        → status
 *
 * No auth. The invoice contents are a payment request to the operator's own
 * address — paying the exact amount shown settles the listing it was issued
 * for. If somebody creates an unused invoice, they have an unused invoice;
 * nothing moves until the mempool watcher (or an admin) sees the payment.
 */

import {
  createInvoice,
  paymentsConfigured,
  toPublic as invoiceToPublic,
  reapInvoice,
} from './payments.js';
import { getInvoice, getListing } from './db.js';

export async function handleInvoiceCreate(req, res) {
  if (req.method !== 'POST') return json(res, 405, { ok: false, reason: 'method not allowed' });
  if (!paymentsConfigured()) {
    return json(res, 503, { ok: false, reason: 'payments are not enabled on this instance' });
  }

  let body;
  try { body = await readJson(req); }
  catch (err) { return json(res, 400, { ok: false, reason: String(err?.message || err) }); }

  const listingId = String(body?.listing_id || '').trim();
  if (!listingId) return json(res, 400, { ok: false, reason: '`listing_id` required' });
  const listing = getListing(listingId);
  if (!listing) return json(res, 404, { ok: false, reason: 'no such listing' });

  try {
    const invoice = await createInvoice(listingId);
    return json(res, 201, { ok: true, invoice: invoiceToPublic(invoice) });
  } catch (err) {
    return json(res, 500, { ok: false, reason: String(err?.message || err) });
  }
}

export function handleInvoiceGet(req, res, url) {
  const parts = new URL(url, 'http://localhost').pathname.split('/').filter(Boolean);
  // ['api', 'invoice', '<id>']
  if (parts.length !== 3) return json(res, 400, { ok: false, reason: 'expected /api/invoice/<id>' });
  const id = parts[2];
  const invoice = getInvoice(id);
  if (!invoice) return json(res, 404, { ok: false, reason: 'no such invoice' });

  // A pending invoice past its deadline flips to 'expired' here lazily — the
  // mempool watcher does not need a periodic sweeper if every status check
  // takes care of its own invoice.
  if (invoice.status === 'pending' && Date.parse(invoice.expires_at) < Date.now()) {
    reapInvoice(id);
    invoice.status = 'expired';
  }
  return json(res, 200, { ok: true, invoice: invoiceToPublic(invoice) });
}

/* -------- helpers -------- */

const MAX_BODY = 32 * 1024;

async function readJson(req) {
  const chunks = [];
  let total = 0;
  for await (const chunk of req) {
    total += chunk.length;
    if (total > MAX_BODY) throw new Error('body too large');
    chunks.push(chunk);
  }
  const body = Buffer.concat(chunks).toString('utf8');
  if (!body.trim()) throw new Error('empty request body');
  return JSON.parse(body);
}

function json(res, status, body) {
  const payload = JSON.stringify(body);
  res.writeHead(status, {
    'content-type': 'application/json; charset=utf-8',
    'cache-control': 'no-store',
    'content-length': Buffer.byteLength(payload),
  });
  res.end(payload);
}