function_app.py

'''Azure Function App to append ONS Geography data to OS API calls'''

import json
import requests

import azure.functions as func

from azure.functions import HttpRequest, HttpResponse

from ons_geography import get_ons_from_postcodes

app = func.FunctionApp(http_auth_level=func.AuthLevel.ANONYMOUS)


@app.function_name('places')
@app.route(route="places/{operation}")
def http_trigger(req: HttpRequest) -> HttpResponse:
    '''HTTP trigger function provides the route into the application.'''

    # The operation is one of "find", "postcode", "uprn", "nearest", "bbox", "radius", "polygon"
    operation = req.route_params.get("operation")

    query_params = req.params

    # Call the OS Places API
    api_url = "https://api.os.uk/search/places/v1/" + operation + "?"

    # Add all the query parameters to the URL
    for key, value in query_params.items():
        api_url += f"&{key}={value}"

    try:
        # Call the OS Places API
        response = requests.get(api_url, timeout=10)

        # If the response is successful, append the ONS Geography data
        if response.status_code == 200:
            # Get the JSON response
            response_json = response.json()

            # The return data is a list of results with a "DPA" key and/or an "LPI" key
            # The DPA object is the delivery point address - use the POSTCODE key
            # The LPI object is the land and property identifier - use the POSTAL_ADDRESS_CODE key

            # Create an array of postcodes by trying first from the LPI object or the DPA object
            postcodes = []
            for result in response_json["results"]:
                postcode = result.get("LPI", {}).get(
                    "POSTAL_ADDRESS_CODE") or result.get("DPA", {}).get("POSTCODE")
                if postcode and postcode.replace(' ', '') not in postcodes:
                    postcodes.append(postcode.replace(' ', ''))

            ons_data_array = get_ons_from_postcodes(postcodes)

            # For each result, append the ONS Geography data
            for result in response_json["results"]:
                # Get the postcode
                postcode = result.get("LPI", {}).get(
                    "POSTAL_ADDRESS_CODE") or result.get("DPA", {}).get("POSTCODE")

                # Find the ONS Geography data for the postcode
                ons_postcode_data = None
                for ons_data in ons_data_array:
                    if ons_data.get("postcode").replace(' ', '') == postcode.replace(' ', ''):
                        ons_postcode_data = ons_data
                        break

                # Add the ONS Geography data to the result
                result["ons_postcode_data"] = ons_postcode_data

            return func.HttpResponse(json.dumps(response_json), status_code=200, mimetype="application/json")

        else:
            # If the response is not successful, return the error message
            return func.HttpResponse(
                "Error calling OS Places API: " + response.text,
                status_code=response.status_code
            )

    except Exception as e:
        # If there is an exception, return the error message
        return func.HttpResponse(
            "Error calling OS Places API: " + str(e),
            status_code=500
        )