feat: resolve gateway endpoints and methods per action

nepali_payment/factory.py

@@ -0,0 +1,71 @@
+"""Service interface + endpoint resolution factories."""
+
+from functools import lru_cache
+
+from nepali_payment.constants import ApiEndpoints
+from nepali_payment.enums import PaymentAction, PaymentMethod, PaymentMode
+from nepali_payment.exceptions import UnsupportedGatewayError
+
+# Each entry: (config_class, action -> (url_attr, method_attr))
+_ENDPOINTS: dict[
+    PaymentMethod,
+    tuple[type, dict[PaymentAction, tuple[str, str]]],
+] = {
+    PaymentMethod.ESEWA: (
+        ApiEndpoints.ESEWA,
+        {
+            PaymentAction.PROCESS_PAYMENT: ("PROCESS_PAYMENT_URL", "PROCESS_PAYMENT_METHOD"),
+            PaymentAction.VERIFY_PAYMENT: ("VERIFY_PAYMENT_URL", "VERIFY_PAYMENT_METHOD"),
+        },
+    ),
+    PaymentMethod.KHALTI: (
+        ApiEndpoints.KHALTI,
+        {
+            PaymentAction.PROCESS_PAYMENT: ("PROCESS_PAYMENT_URL", "PROCESS_PAYMENT_METHOD"),
+            PaymentAction.VERIFY_PAYMENT: ("VERIFY_PAYMENT_URL", "VERIFY_PAYMENT_METHOD"),
+        },
+    ),
+    PaymentMethod.FONEPAY: (
+        ApiEndpoints.FONEPAY,
+        {
+            PaymentAction.PROCESS_PAYMENT: ("QR_GENERATE_URL", "QR_GENERATE_METHOD"),
+            PaymentAction.VERIFY_PAYMENT: ("QR_STATUS_URL", "QR_STATUS_METHOD"),
+        },
+    ),
+}
+
+
+@lru_cache(maxsize=32)
+def _endpoint_for(
+    gateway: PaymentMethod,
+    action: PaymentAction,
+    mode: PaymentMode,
+) -> tuple[str, str]:
+    """
+    Get the API address and HTTP method for a gateway operation.
+
+    Args:
+        gateway: The payment method.
+        action: The operation (initiate or verify).
+        mode: Sandbox or production.
+
+    Returns:
+        A ``(url, http_method)`` tuple where ``http_method`` is ``"POST"`` or
+        ``"GET"``.
+
+    Raises:
+        UnsupportedGatewayError: For unsupported gateway/action combinations.
+
+    """
+    entry = _ENDPOINTS.get(gateway)
+    if entry is None:
+        raise UnsupportedGatewayError(f"The combination of {gateway}, {mode}, and {action} is not supported.")
+
+    config, action_map = entry
+    attrs = action_map.get(action)
+    if attrs is None:
+        raise UnsupportedGatewayError(f"The combination of {gateway}, {mode}, and {action} is not supported.")
+
+    base = config.BASE_URL if mode == PaymentMode.PRODUCTION else config.SANDBOX_BASE_URL
+    url_attr, method_attr = attrs
+    return base + getattr(config, url_attr), getattr(config, method_attr)