main.py

from fastapi import FastAPI, Query
from pyproj import CRS, Transformer
from shapely.geometry import Point

from google.cloud import secretmanager
from secretmanager import Config

import requests
import geopandas as gpd

config = Config()
api_key = config.get_api_key()

statsector_parquet = 'data/statistical_sectors_2022.parquet'

app = FastAPI()

@app.get("/get-statsector/")
async def get_statsector(
    lat: float = Query(None, description="Latitude"),
    lon: float = Query(None, description="Longitude"),
    address: str = Query(None, description="Address")
):
    if lat is None and lon is None:
        if address is not None:
            # Additional validation: Ensure address is a string
            if not isinstance(address, str):
                return {"error": "'address' must be of type string."}
            
            base_url = "https://maps.googleapis.com/maps/api/geocode/json"
            
            params = {
                "address": address,
                "key": api_key,
            }
            
            try:
                response = requests.get(base_url, params=params)
                data = response.json()
                
                if response.status_code == 200:
                    if data["status"] == "OK":
                        location = data["results"][0]["geometry"]["location"]
                        lat = location["lat"]
                        lon = location["lng"]
                    else:
                        return {"error": f"Geocoding API response status: {data['status']}"}
                else:
                    return {"error": f"Request failed with status code: {response.status_code}"}
            except Exception as e:
                return {"error": f"An error occurred: {e}"}


        else:
            return {"error": "Either 'lat' and 'lon' or 'address' must be provided."}
    else:
        if not isinstance(lat, float) or not isinstance(lon, float):
            return {"error": "'lat' and 'lon' must be of type float."}

    # Stat Sector uses Lambert projection 
    # So we have to have transformers, World Geodetic System to Lambert and back
    # https://www.ngi.be/website/de-lambert-kaartprojectie-2/
    crs_lambert = CRS.from_string("EPSG:31370")
    crs_wgs = CRS.from_string("EPSG:4326")

    transformer_l2w = Transformer.from_crs(crs_lambert, crs_wgs)
    transformer_w2l = Transformer.from_crs(crs_wgs, crs_lambert)

    # The following file takes a short while to load
    statsectors = gpd.read_parquet(statsector_parquet)

    # Transform to Lambert projection
    res_lam = transformer_w2l.transform(lat, lon)
    lam_coo = Point(res_lam[0], res_lam[1])

    try:
        # Look up coordinates in the file
        sector_results = statsectors[statsectors['geometry'].contains(lam_coo)]
        first_sector_result = sector_results.iloc[0]

        response = {"sector_id": first_sector_result['cd_sector'], "sector_name": first_sector_result['tx_sector_descr_nl']}
        
        if first_sector_result['cd_sector']:
            return response
        else:
            return {"error": "Sector not found for the given coordinates"}
    except Exception as e:
        return {"error": str(e)}