PayRam Top-Up Wallet Integration (recommended for existing apps)

New store with no payment history? Use the checkout/plugin path (payram-checkout-integration, or the WooCommerce plugin). Existing app with users and invoices? Use THIS pattern.

Why top-up-first, not pay-per-invoice

Crypto payments are approximate by nature. A customer paying a $50 invoice may send $49.20 (gas mental-math), $60 (round number), $50 in two transfers, or the right amount two hours after the link "expired" — the funds still arrive on-chain. If you bind payments directly to invoices, every one of those is an exception you must code for.

The top-up pattern flips it: whatever arrives is credited to the user's wallet balance — exactly the amount received. Invoices are then debited from the balance as a plain, atomic app-side operation. Every crypto quirk becomes a balance state, not a payment failure:

Architecture: the ledger

Three tables. The ledger is append-only; the balance is derived (cache it, but the ledger is truth).

CREATE TABLE user_wallets (
  id            BIGSERIAL PRIMARY KEY,
  user_id       BIGINT NOT NULL UNIQUE,
  balance_usd   NUMERIC(20,8) NOT NULL DEFAULT 0 CHECK (balance_usd >= 0),
  updated_at    TIMESTAMPTZ NOT NULL DEFAULT now()
);

CREATE TABLE wallet_ledger (
  id                   BIGSERIAL PRIMARY KEY,
  wallet_id            BIGINT NOT NULL REFERENCES user_wallets(id),
  entry_type           TEXT NOT NULL CHECK (entry_type IN
                         ('credit','credit_adjustment','debit','debit_reversal')),
  amount_usd           NUMERIC(20,8) NOT NULL CHECK (amount_usd > 0),
  payram_reference_id  TEXT,          -- set on credit/credit_adjustment
  invoice_id           BIGINT,        -- set on debit/debit_reversal
  memo                 TEXT,
  created_at           TIMESTAMPTZ NOT NULL DEFAULT now()
);
-- Idempotency: exactly ONE base credit per PayRam payment reference.
CREATE UNIQUE INDEX one_credit_per_reference
  ON wallet_ledger (payram_reference_id) WHERE entry_type = 'credit';

CREATE TABLE invoices (
  id            BIGSERIAL PRIMARY KEY,
  user_id       BIGINT NOT NULL,
  amount_usd    NUMERIC(20,8) NOT NULL,
  status        TEXT NOT NULL DEFAULT 'pending'
                  CHECK (status IN ('pending','awaiting_funds','paid','cancelled')),
  paid_at       TIMESTAMPTZ
);

Use NUMERIC, never floats. Everything is denominated in USD — PayRam's filled_amount_in_usd gives you the USD value of what actually arrived, so a single-currency ledger sidesteps FX entirely.

The critical PayRam semantic: filled amounts are CUMULATIVE

One payment reference can fire several webhooks as funds arrive: PARTIALLY_FILLED (filled_amount_in_usd: 20.00) → FILLED (filled_amount_in_usd: 50.00). The amount is the running total for that reference, not a delta. Your credit logic must be:

on webhook (reference_id, status, filled_amount_in_usd):
  if status not in (PARTIALLY_FILLED, FILLED, OVER_FILLED): ack and ignore
  in one DB transaction:
    prior = SUM(amount) of credit + credit_adjustment rows for reference_id
    delta = filled_amount_in_usd - prior
    if delta <= 0: ack (duplicate or out-of-order webhook — already credited)
    insert ledger row:
      entry_type = 'credit' if prior == 0 else 'credit_adjustment'
      amount_usd = delta, payram_reference_id = reference_id
    balance_usd += delta
  then: try_settle_open_invoices(user)

This one function absorbs duplicates (delta ≤ 0), out-of-order delivery, partial-then-full fills, and overpayment — with zero special cases.

The flows

Flow A — invoice settlement (spend from balance)

create invoice → BEGIN; SELECT balance FROM user_wallets WHERE user_id=? FOR UPDATE;
  if balance >= invoice.amount:
      insert debit row (invoice_id), balance -= amount, invoice.status='paid'; COMMIT
  else:
      invoice.status='awaiting_funds'; COMMIT → go to Flow B for the shortfall

FOR UPDATE (or SERIALIZABLE) makes concurrent debits of one wallet safe — the balance check and the debit are one atomic unit.

Flow B — top-up (get funds in)

shortfall = invoice.amount - balance
POST {payram}/api/v1/payment  (API-Key header)
  { customerEmail, customerID: "<your user_id>", amountInUSD: shortfall, invoiceID: "<your invoice id>" }
→ show returned url to the user

• customerID = your user id — it's how the webhook maps back to the wallet.
• invoiceID is optional metadata; the ledger does NOT rely on it (credits are wallet-level).
• Ask for the shortfall, not the full invoice — existing balance already counts.
• Creating a payment cancels that customer's other open payments in the project. Reuse the user's open link while it is still valid, rather than minting a new one on every page view.
• Create the link on your server; the project API key can also create payouts, so it never goes to the browser.

Flow C — the credit webhook (funds arrived)

Register your webhook in the PayRam project (Project → Webhooks). PayRam POSTs snake_case JSON with amounts as decimal strings, and signs every delivery.

1. Ping: if the request carries X-Webhook-Test: true, it is an unsigned payout ping. Answer 200 and stop.
2. Verify: check the X-Payram-Signature: sha256=<hex HMAC-SHA256 of the raw body> header, keyed with your project API key (the newest active one; there is no separate webhook secret). Compute the HMAC over the raw request bytes and compare in constant time.
3. Credit: parse the body, run the cumulative-credit logic above, then re-attempt Flow A for any awaiting_funds invoices of that user.

Flow D — refunds & cancellations

• App-level refund (user keeps money in your app): insert debit_reversal for the invoice → balance goes back up. No crypto moves.
• Crypto must actually leave: pay out via PayRam's payout flow (see payram-payouts) AND insert a matching debit (memo: refund payout) so the ledger mirrors reality.

Case matrix (all of them)

PayRam API surface you use

Statuses that credit: PARTIALLY_FILLED, FILLED, OVER_FILLED. Ignore OPEN; treat CANCELLED as informational (no funds → no credit).

Generate the code

The MCP tool generate_topup_integration_snippet emits the ledger SQL, the cumulative-credit webhook handler, and the atomic settle function for your framework — start there, then adapt table names to your app.

Rollout checklist

1. Create the three tables; wire the webhook endpoint (verify X-Payram-Signature over the raw body, constant-time; ack the payout ping).
2. Implement cumulative credit + atomic settle (use the generator).
3. Point a test invoice at testnet, pay the link partially, verify awaiting_funds → top up → paid.
4. Add the nightly reconciliation query before going to mainnet.
5. Go live; monitor node sync (payram_ops_playbook task node_sync, or check_node_sync in local mode). A lagging chain delays credits, not correctness.