Payment Monitor System

[clostao]

In high level for buying credits the user will create a Transfer transaction, using the extrinsic hash will create an invoice, and the submit the transaction. The invoice would expire if the payment is not received within a number of blocks. When the invoice is marked as 'paid' their subscription will be updated with the additional credits.

Implementation details

• Core design
  • A user requests the API for conversation rate between $AI3 and credits (measured in bytes).
  • Through our frontend, when the transaction is created an Invoice is automatically created including some data for enabling the transaction watcher find the extrinsic.
  • A user submits the balance.Transfer transaction with a selected amount targeting a number of upload credits.

Note: Probably this could be implemented in @autonomys/auto-drive to ease this integration

• Invoice creation

  • Create Invoice with fields:
    • invoiceId, userPublicId, productId, numCredits
    • extrinsic_hash, last_seen_block, for tracking the extrinsic (last_seen_block would help during re-orgs)
    • status (pending/paid/expired), createdAt, expiresAt
  • UI instructs the user to transfer the exact amount from payerAddress to the treasury address on the specified chain.

• Finality and event listening

  • Subscribe to finalised blocks; scan balances.Transfer where dest == TREASURY_ADDRESS.
  • Match events to invoices using (from == payerAddress) AND (amount == expectedAmountPlanck).
  • Accept only on finalised blocks (or finalised + X confirmations as configured).

• Operations and safety

  • Automatic expiry and clean-up of unpaid invoices.
  • Wrap payment with enhanced observability tools.

• Processing flow

  • On finalized match (dest == TREASURY_ADDRESS) && (extrinsic_hash = invoice.extrinsic_hash):
    • Begin DB transaction.
    • Verify invoice.status == pending and not already processed by (extrinsic_hash) uniqueness.
    • Mark invoice.status = paid, record chain refs.
    • Add service.
    • Commit.