Payment Instruction Parser – Node.js Backend

This project implements the payment instruction parser and executor described in the Resilience17 Node backend assessment, using the provided scaffold.

The main REST endpoint is:

• POST /payment-instructions

It parses instructions like:

DEBIT 30 USD FROM ACCOUNT a FOR CREDIT TO ACCOUNT b

or

CREDIT 300 NGN TO ACCOUNT acc-002 FOR DEBIT FROM ACCOUNT acc-001 ON 2026-12-31

and returns a structured response with transaction status, codes, and updated account balances.

---

Tech Stack

• Node.js (CommonJS)
• Express (via @app-core/server)
• In‑memory account processing (no database required for this assessment)

---

Local Setup

1. Install dependencies:

npm install

2. Create a .env file (optional). For this assessment:

• No MongoDB is required.
• Ensure either:
  • DISABLE_DB=1, or
  • MONGO_URI is not set.

3. Start the server:

node app.js

By default the app listens on process.env.PORT (or 8811 if set in your environment).

---

Live Endpoint

If this project is deployed, the assessment endpoint is available at:

POST https://payment-instruction-parser-hykt.onrender.com/payment-instructions

Quick test with curl:

curl -X POST https://payment-instruction-parser-hykt.onrender.com/payment-instructions \
  -H "Content-Type: application/json" \
  -d '{
    "accounts": [
      { "id": "a", "balance": 230, "currency": "USD" },
      { "id": "b", "balance": 300, "currency": "USD" }
    ],
    "instruction": "DEBIT 30 USD FROM ACCOUNT a FOR CREDIT TO ACCOUNT b"
  }'

Endpoint: POST /payment-instructions

Request body:

{
  "accounts": [
    { "id": "a", "balance": 230, "currency": "USD" },
    { "id": "b", "balance": 300, "currency": "USD" }
  ],
  "instruction": "DEBIT 30 USD FROM ACCOUNT a FOR CREDIT TO ACCOUNT b"
}

Response (successful example):

{
  "type": "DEBIT",
  "amount": 30,
  "currency": "USD",
  "debit_account": "a",
  "credit_account": "b",
  "execute_by": null,
  "status": "successful",
  "status_reason": "Transaction executed successfully",
  "status_code": "AP00",
  "accounts": [
    {
      "id": "a",
      "balance": 200,
      "balance_before": 230,
      "currency": "USD"
    },
    {
      "id": "b",
      "balance": 330,
      "balance_before": 300,
      "currency": "USD"
    }
  ]
}

Common error responses use:

• status: "failed" or "pending"
• status_code: one of AM01, CU01, CU02, AC01, AC02, AC03, AC04, DT01, SY01, SY02, SY03, AP00, AP02

For completely unparseable instructions, all parseable fields are null and accounts is an empty array.

---

Implementation Notes

• Parser is implemented in services/payment-instructions/parser.js using string methods only (no regex).
• Business rules and status codes live in services/payment-instructions/validator.js.
• Orchestration and response shaping are in services/payment-instructions/process-payment-instruction.js.
• Endpoint handler is endpoints/payment-instructions/create.js and is wired in app.js via ENDPOINT_CONFIGS.

---

Deployment (e.g. Render)

When deploying to a platform like Render:

• Build command: npm install
• Start command: node app.js
• Environment variables:
  • DISABLE_DB=1
  • NODE_ENV=production
  • Do not set MONGO_URI / MONGODB_URI

Deployed endpoint path remains:

POST https://<your-host>/payment-instructions