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142 changes: 142 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.
"""

# imports

import requests
from requests import Response
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Do you need to do this? You're basically importing from the same file twice (which AI seems to like doing and I'm not sure why). IMO better to just do from requests import Response, <whatever else you're using>.


# definitions
ars_interactionId = "urn:nhs:names:services:gpconnect:structured:fhir:operation:gpc.getstructuredrecord-1" # noqa: E501 this is standard InteractionID for accessRecordStructured
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You can break this over two lines, it doesn't need to bust the line length limit.

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

ars_fhir_base = "/FHIR/STU3"
ars_fhir_operation = "$gpc.getstructuredrecord"
timeout = None # None used for quicker dev, adjust as needed


class ExternalServiceError(Exception):
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I think we could move this into a common library. I've started one in my current ticket anyway.

"""
Exception raised when the downstream GPProvider FHIR API request fails.

This exception wraps :class:`requests.HTTPError` thrown by
``response.raise_for_status()`` and re-raises it as ``ExternalServiceError``
to decouple callers from the underlying ``requests`` library exception types.
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I don't understand this comment. The exception as written isn't related to requests.HTTPError and doesn't have any of its own logic. I'd just delete this bit?

"""


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:
"""
Create a GPProviderClient instance.

Args:
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.
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I suggest we write docstrings with Sphinx-style argument listing. Then we can auto-generate our documentation (though that said I don't know if the likes of ChatGPT are going to obsolete the likes of Sphinx). Still, it's standard and it gives us the option, and it's easy enough to just ask the AI to do. Don't know if @davidhamill1-nhs and @nhsd-jack-wainwright agree?


methods:
access_structured_record: fetch structured patient record
from GPProvider FHIR API.
"""
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_interactionId,
"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)

response = requests.post(
self.provider_endpoint + ars_fhir_base + "/patient/" + ars_fhir_operation,
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I was convinced that Python had a built-in function for constructing URLs from arbitrary components, but it turns out that it doesn't. And you can't use pathlib either because if any component has a leading slash it drops all the previous components. I wonder if it's worth writing one ourselves.

headers=headers,
data=body,
timeout=timeout,
)

try:
response.raise_for_status()
except requests.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
Original file line number Diff line number Diff line change
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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.

Fixtures:
- `stub`: Provides an instance of the `GpProviderStub` for simulating the GPProvider
- `mock_request_post`: Patches the `requests.post` method to intercept API calls and
route them to the stub provider. Captures request details for verification.
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Not sure we really need to list the fixtures in the module docstring. Easy enough to find them by looking through the file, and the header will go out of date because nobody will update it.


"""

from typing import Any

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

from gateway_api.provider_request import ExternalServiceError, GpProviderClient

ars_interactionId = "urn:nhs:names:services:gpconnect:structured:fhir:operation:gpc.getstructuredrecord-1" # noqa: E501 this is standard InteractionID for accessRecordStructured
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As above don't need to #noqa this, just break it across two lines.



@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

return stub.access_record_structured()

monkeypatch.setattr(requests, "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://invalid.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://invalid.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"]

for key, value in expected_headers.items():
assert captured_headers.get(key) == value
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://invalid.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://invalid.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()

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

assert result.status_code == expected_response.status_code
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://invalid.com"
trace_id = "some_uuid_value"

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

# Simulate an error response from the stub
def _fake_post_error(
url: str,
headers: CaseInsensitiveDict[str],
data: str,
timeout: int,
) -> Response:
response = Response()
response.status_code = 500
response._content = b"Internal Server Error" # noqa: SLF001 TODO: push this back into the stub?
response.reason = "Internal Server Error"
return response

monkeypatch.setattr(requests, "post", _fake_post_error)

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