Tell me more about the integration module with four POS systems — architecture, what did it look like?

The integration module with four POS systems was built on the principle of a unified interface for interacting with different APIs. The architecture resembled an abstraction layer that concealed the specifics of each POS system and provided the frontend with standardized methods.

Main components:

• Adapters for each POS system — separate classes or modules implementing methods for working with a specific API (e.g., authorization, transaction sending, status retrieval).
• Adapter factory — selects the necessary adapter depending on the POS type.
• Unified interface — methods called from the frontend, such as processPayment(), getReceipt().

This approach allowed adding new POS systems without changing the client code, simply by implementing a new adapter. Data exchange was performed using REST requests or WebSocket, depending on the POS capabilities.

An example of a simplified interface:

class PosAdapter {
  processPayment(data) { throw 'Not implemented' }
}

class PosAAdapter extends PosAdapter {
  processPayment(data) {
    // call POS A API
  }
}

class PosBAdapter extends PosAdapter {
  processPayment(data) {
    // call POS B API
  }
}

function getAdapter(posType) {
  switch(posType) {
    case 'POS_A': return new PosAAdapter()
    case 'POS_B': return new PosBAdapter()
  }
}

const adapter = getAdapter(currentPosType)
adapter.processPayment(paymentData)

This module ensured scalability and ease of maintenance.