Feature: Card Payment – Happy Path End-to-End (UI, Integration, Test, CI/CD)

[neronguyen]

User Story

As a merchant, I want to accept card payments from customers for their orders, so that I can receive payments and complete sales.

Acceptance Criteria (user/outcome focused; testable)

1. Navigation & Input
   • Given the merchant is on PaymentEntryScreen, when they enter an amount and press "Next", then the app navigates to ReadCardScreen.
2. Card Capture Simulation
   • Given the merchant is on ReadCardScreen, when the fake POS SDK is invoked, then it returns a card token within a short delay.
3. Gateway Call & Success
   • Given a valid PaymentIntent and card token, when the app calls the fake Payment Gateway, then it receives a success response with a unique transactionId.
4. Persistence
   • Given a successful gateway response, the payment intent in local DB is updated to COMPLETED and stores the transactionId.
5. UI Feedback
   • After success, the UI displays a simple pop-up dialog that shows success and the transactionId (no dedicated result screen).
6. Tests & CI
   • Unit tests verify the happy path flow (Repository + ViewModel) and the CI pipeline runs these tests successfully.

Implementation Tasks (developer-focused)

• UI
  1. Add PaymentEntryScreen: amount input, validation (positive amount), card method auto-selected, and "Next" button to ReadCardScreen.
  2. Add ReadCardScreen: loading/reading state and invokes FakePosSdk.readCard(), triggers payment, shows simple pop-up dialog on success (transactionId).
• Fake POS SDK
  3. Implement FakePosSdk.readCard() to resolve after a short delay and return a fake card token.
• Fake Payment Gateway
  4. Implement FakePaymentGateway.charge(amount, idempotencyKey, cardToken) to always return success and a unique transactionId (handle idempotencyKey).
• Repository & Domain
  5. PaymentRepository: createPaymentIntent(amount), startCardPayment(intentId) flow: load intent, call FakePosSdk, call FakePaymentGateway, update intent to COMPLETED and save transactionId.
• ViewModels & State
  6. ViewModels for PaymentEntryScreen and ReadCardScreen to manage states and transitions.
• Local DB
  7. Define/extend PaymentIntent entity: intentId, amount, status (PENDING/COMPLETED/FAILED), idempotencyKey, transactionId, lastError, createdAt, updatedAt.
• Tests
  8. Unit test: happy path end-to-end using fakes. ViewModel tests: input -> navigation -> read -> success.
• CI/CD
  9. Ensure unit tests run in pipeline; update pipeline to fail on regressions.

Out of Scope

• Retry logic, timeouts, network error handling, or failure flows.
• QR Payments and partial payments.
• Real POS/Gateway integration and security/encryption.
• Advanced/polished UI or dedicated result screen.

References

• README and docs/diagrams for architecture context.

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Note: This issue focuses on the happy path only. Failure and retry behaviors will be added in separate tickets later.