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146 changes: 146 additions & 0 deletions gateway-api/src/gateway_api/provider_request.py
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"""
Module: gateway_api.provider_request

This module contains the GpProviderClient class, which provides a
simple client for interacting with the GPProvider FHIR GP System.

The GpProviderClient class includes methods to fetch structured patient
records from a GPProvider FHIR API endpoint.

Usage:
Instantiate a GpProviderClient with:
- provider_endpoint: The FHIR API endpoint for the provider.
- provider_asid: The ASID for the provider.
- consumer_asid: The ASID for the consumer.

Use the `access_structured_record` method to fetch a structured patient record:
Parameters:
- trace_id (str): A unique identifier for the request.
- body (str): The request body in FHIR format.

Returns:
The response from the provider FHIR API.
"""

from collections.abc import Callable
from urllib.parse import urljoin

from requests import HTTPError, Response
from stubs.stub_provider import GpProviderStub

ARS_INTERACTION_ID = (
"urn:nhs:names:services:gpconnect:structured"
":fhir:operation:gpc.getstructuredrecord-1"
)
ARS_FHIR_BASE = "FHIR/STU3"
FHIR_RESOURCE = "patient"
ARS_FHIR_OPERATION = "$gpc.getstructuredrecord"
TIMEOUT: int | None = None # None used for quicker dev, adjust as needed

# Direct all requests to the stub provider for steel threading in dev.
# Replace with `from requests import post` for real requests.
PostCallable = Callable[..., Response]
_provider_stub = GpProviderStub()


def _stubbed_post(trace_id: str, body: str) -> Response:
"""A stubbed requests.post function that routes to the GPProviderStub."""
return _provider_stub.access_record_structured(trace_id, body)


post: PostCallable = _stubbed_post


class ExternalServiceError(Exception):
"""
Exception raised when the downstream GPProvider FHIR API request fails.
"""


class GpProviderClient:
"""
A client for interacting with the GPProvider FHIR GP System.

This class provides methods to interact with the GPProvider FHIR API,
including fetching structured patient records.

Attributes:
provider_endpoint (str): The FHIR API endpoint for the provider.
provider_asid (str): The ASID for the provider.
consumer_asid (str): The ASID for the consumer.

Methods:
access_structured_record(trace_id: str, body: str) -> Response:
Fetch a structured patient record from the GPProvider FHIR API.
"""

def __init__(
self,
provider_endpoint: str,
provider_asid: str,
consumer_asid: str,
) -> None:
self.provider_endpoint = provider_endpoint
self.provider_asid = provider_asid
self.consumer_asid = consumer_asid

def _build_headers(self, trace_id: str) -> dict[str, str]:
"""
Build the headers required for the GPProvider FHIR API request.

Args:
trace_id (str): A unique identifier for the request.

Returns:
dict[str, str]: A dictionary containing the headers for the request,
including content type, interaction ID, and ASIDs for the provider
and consumer.
"""
return {
"Content-Type": "application/fhir+json",
"Accept": "application/fhir+json",
"Ssp-InteractionID": ARS_INTERACTION_ID,
"Ssp-To": self.provider_asid,
"Ssp-From": self.consumer_asid,
"Ssp-TraceID": trace_id,
}

def access_structured_record(
self,
trace_id: str,
body: str,
) -> Response:
"""
Fetch a structured patient record from the GPProvider FHIR API.

Args:
trace_id (str): A unique identifier for the request, passed in the headers.
body (str): The request body in FHIR format.

Returns:
Response: The response from the GPProvider FHIR API.

Raises:
ExternalServiceError: If the API request fails with an HTTP error.
"""

headers = self._build_headers(trace_id)

endpoint_path = "/".join([ARS_FHIR_BASE, FHIR_RESOURCE, ARS_FHIR_OPERATION])
url = urljoin(self.provider_endpoint, endpoint_path)

response = post(
url,
headers=headers,
data=body,
timeout=TIMEOUT,
)

try:
response.raise_for_status()
except HTTPError as err:
raise ExternalServiceError(
f"GPProvider FHIR API request failed:{err.response.reason}"
) from err

return response
240 changes: 240 additions & 0 deletions gateway-api/src/gateway_api/test_provider_request.py
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"""
Unit tests for :mod:`gateway_api.provider_request`.

This module contains unit tests for the `GpProviderClient` class, which is responsible
for interacting with the GPProvider FHIR API.

"""

from typing import Any

import pytest
from requests import Response
from requests.structures import CaseInsensitiveDict
from stubs.stub_provider import GpProviderStub

from gateway_api import provider_request
from gateway_api.provider_request import ExternalServiceError, GpProviderClient

ars_interactionId = (
"urn:nhs:names:services:gpconnect:structured"
":fhir:operation:gpc.getstructuredrecord-1"
)


@pytest.fixture
def stub() -> GpProviderStub:
return GpProviderStub()


@pytest.fixture
def mock_request_post(
monkeypatch: pytest.MonkeyPatch, stub: GpProviderStub
) -> dict[str, Any]:
"""
Fixture to patch the `requests.post` method for testing.

This fixture intercepts calls to `requests.post` and routes them to the
stub provider. It also captures the most recent request details, such as
headers, body, and URL, for verification in tests.

Returns:
dict[str, Any]: A dictionary containing the captured request details.
"""
capture: dict[str, Any] = {}

def _fake_post(
url: str,
headers: CaseInsensitiveDict[str],
data: str,
timeout: int,
) -> Response:
"""A fake requests.post implementation."""

capture["headers"] = dict(headers)
capture["data"] = data
capture["url"] = url

# Provide dummy or captured arguments as required by the stub signature
return stub.access_record_structured(
trace_id=headers.get("Ssp-TraceID", "dummy-trace-id"), body=data
)

monkeypatch.setattr(provider_request, "post", _fake_post)
return capture


def test_valid_gpprovider_access_structured_record_makes_request_correct_url_post_200(
mock_request_post: dict[str, Any],
stub: GpProviderStub,
) -> None:
"""
Test that the `access_structured_record` method constructs the correct URL
for the GPProvider FHIR API request and receives a 200 OK response.

This test verifies that the URL includes the correct FHIR base path and
operation for accessing a structured patient record.
"""
provider_asid = "200000001154"
consumer_asid = "200000001152"
provider_endpoint = "https://test.com"
trace_id = "some_uuid_value"

client = GpProviderClient(
provider_endpoint=provider_endpoint,
provider_asid=provider_asid,
consumer_asid=consumer_asid,
)

result = client.access_structured_record(trace_id, "body")

captured_url = mock_request_post.get("url", provider_endpoint)

assert (
captured_url
== provider_endpoint + "/FHIR/STU3/patient/$gpc.getstructuredrecord"
)
assert result.status_code == 200


def test_valid_gpprovider_access_structured_record_with_correct_headers_post_200(
mock_request_post: dict[str, Any],
stub: GpProviderStub,
) -> None:
"""
Test that the `access_structured_record` method includes the correct headers
in the GPProvider FHIR API request and receives a 200 OK response.

This test verifies that the headers include:
- Content-Type and Accept headers for FHIR+JSON.
- Ssp-TraceID, Ssp-From, Ssp-To, and Ssp-InteractionID for GPConnect.
"""
provider_asid = "200000001154"
consumer_asid = "200000001152"
provider_endpoint = "https://test.com"
trace_id = "some_uuid_value"

client = GpProviderClient(
provider_endpoint=provider_endpoint,
provider_asid=provider_asid,
consumer_asid=consumer_asid,
)
expected_headers = {
"Content-Type": "application/fhir+json",
"Accept": "application/fhir+json",
"Ssp-TraceID": str(trace_id),
"Ssp-From": consumer_asid,
"Ssp-To": provider_asid,
"Ssp-InteractionID": ars_interactionId,
}

result = client.access_structured_record(trace_id, "body")

captured_headers = mock_request_post["headers"]

assert expected_headers == captured_headers
assert result.status_code == 200


def test_valid_gpprovider_access_structured_record_with_correct_body_200(
mock_request_post: dict[str, Any],
stub: GpProviderStub,
) -> None:
"""
Test that the `access_structured_record` method includes the correct body
in the GPProvider FHIR API request and receives a 200 OK response.

This test verifies that the request body matches the expected FHIR parameters
resource sent to the GPProvider API.
"""
provider_asid = "200000001154"
consumer_asid = "200000001152"
provider_endpoint = "https://test.com"
trace_id = "some_uuid_value"

request_body = "some_FHIR_request_params"

client = GpProviderClient(
provider_endpoint=provider_endpoint,
provider_asid=provider_asid,
consumer_asid=consumer_asid,
)

result = client.access_structured_record(trace_id, request_body)

captured_body = mock_request_post["data"]

assert result.status_code == 200
assert captured_body == request_body


def test_valid_gpprovider_access_structured_record_returns_stub_response_200(
mock_request_post: dict[str, Any],
stub: GpProviderStub,
) -> None:
"""
Test that the `access_structured_record` method returns the same response
as provided by the stub provider.

This test verifies that the response from the GPProvider FHIR API matches
the expected response, including the status code and content.
"""
provider_asid = "200000001154"
consumer_asid = "200000001152"
provider_endpoint = "https://test.com"
trace_id = "some_uuid_value"

client = GpProviderClient(
provider_endpoint=provider_endpoint,
provider_asid=provider_asid,
consumer_asid=consumer_asid,
)

expected_response = stub.access_record_structured(trace_id, "body")

result = client.access_structured_record(trace_id, "body")

assert result.status_code == 200
assert result.content == expected_response.content


def test_access_structured_record_raises_external_service_error(
mock_request_post: dict[str, Any],
stub: GpProviderStub,
monkeypatch: pytest.MonkeyPatch,
) -> None:
"""
Test that the `access_structured_record` method raises an `ExternalServiceError`
when the GPProvider FHIR API request fails with an HTTP error.
"""
provider_asid = "200000001154"
consumer_asid = "200000001152"
provider_endpoint = "https://test.com"
trace_id = "invalid for test"

client = GpProviderClient(
provider_endpoint=provider_endpoint,
provider_asid=provider_asid,
consumer_asid=consumer_asid,
)

with pytest.raises(
ExternalServiceError,
match="GPProvider FHIR API request failed:Bad Request",
):
client.access_structured_record(trace_id, "body")


def test_stubbed_post_function(stub: GpProviderStub) -> None:
"""
Test the `_stubbed_post` function to ensure it routes to the stub provider.
"""
trace_id = "test-trace-id"
body = "test-body"

# Call the `_stubbed_post` function
response = provider_request._stubbed_post(trace_id, body) # noqa: SLF001 this is testing the private method

# Verify the response is as expected
assert response.status_code == 200
assert response.json() == stub.access_record_structured(trace_id, body).json()
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