Takroriy so‘rov puldan ikki marta yechmasligi kerak

create table payment_request (
  idempotency_key uuid        primary key,
  account_id      bigint      not null,
  request_hash    text        not null,
  status          text        not null
    check (status in ('in_progress', 'succeeded', 'failed')),
  response        jsonb,
  operation_id    bigint      references operation(id),
  created_at      timestamptz not null default now()
);

-- Amallar jurnali: faqat qo'shish. Bekor qilish — teskari ishorali yangi
-- yozuv, update emas va, albatta, delete emas.
create table operation (
  id         bigserial   primary key,
  account_id bigint      not null,
  amount     numeric(20, 4) not null,
  kind       text        not null,
  reverses   bigint      references operation(id),
  created_at timestamptz not null default now()
);

async function charge(req: ChargeRequest) {
  const hash = sha256(canonicalJson(req.body));

  // Kalitni band qilishga urinamiz. Agar u band bo'lsa — bu takror.
  const claimed = await db.insertIgnoreConflict('payment_request', {
    idempotency_key: req.key,
    account_id: req.accountId,
    request_hash: hash,
    status: 'in_progress',
  });

  if (!claimed) {
    const prev = await db.get('payment_request', req.key);

    // Bir xil kalit, boshqa tana — mijoz xato qildi yoki summani
    // almashtirmoqchi.
    if (prev.request_hash !== hash) throw new Conflict('key_reused');

    // Birinchi so'rov hali ishda: keyinroq takrorlashni so'raymiz,
    // lekin ikkinchi marta o'tkazmaymiz.
    if (prev.status === 'in_progress') throw new Retry('in_progress');

    // Tugagan so'rovning takrori — YANGI emas, O'SHA javobni qaytaramiz.
    return prev.response;
  }

  const result = await db.transaction(async (tx) => {
    const op = await tx.insert('operation', {
      account_id: req.accountId,
      amount: -req.body.amount,
      kind: 'charge',
    });

    // Provayderga murojaat BU YERDA emas: tranzaksiya ichidagi tarmoq
    // chaqiruvi — bu pul allaqachon ketgan holda bazada ortga qaytishni
    // olish usuli. Vazifani o'sha tranzaksiya bilan chiquvchi navbatga
    // qo'yamiz.
    await tx.insert('outbox', { type: 'provider.charge', operation_id: op.id });

    return { operationId: op.id };
  });

  await db.update('payment_request', req.key, {
    status: 'succeeded',
    response: result,
    operation_id: result.operationId,
  });

  return result;
}