scripts/generate_mask.py

import requests
import json
from shapely.geometry import shape, mapping, Polygon, MultiPolygon
from shapely.ops import unary_union
import urllib.parse

def fetch_boundary(state):
    url = f"https://nominatim.openstreetmap.org/search?state={urllib.parse.quote(state)}&country=India&polygon_geojson=1&format=json"
    headers = {"User-Agent": "Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/115.0.0.0 Safari/537.36"}
    res = requests.get(url, headers=headers)
    res.raise_for_status()
    data = res.json()
    for item in data:
        if item.get('geojson') and item['geojson']['type'] in ['Polygon', 'MultiPolygon']:
            return shape(item['geojson'])
    return None

states = ["Maharashtra", "Goa", "Karnataka"]
polys = []

for s in states:
    print(f"Fetching {s} boundary...")
    poly = fetch_boundary(s)
    if poly:
        polys.append(poly)
    else:
        print(f"Could not find boundary for {s}")

if polys:
    print("Merging boundaries...")
    merged = unary_union(polys)
    
    # Create an outer bounding box that covers the world (or a large enough area)
    outer = Polygon([(-180, -90), (180, -90), (180, 90), (-180, 90)])
    
    # Create the inverse mask (hole)
    mask = outer.difference(merged)
    
    geojson_mask = {
        "type": "FeatureCollection",
        "features": [
            {
                "type": "Feature",
                "geometry": mapping(mask),
                "properties": {}
            }
        ]
    }
    
    geojson_bounds = {
        "type": "FeatureCollection",
        "features": [
            {
                "type": "Feature",
                "geometry": mapping(merged),
                "properties": {}
            }
        ]
    }
    
    out_mask_path = "frontend/public/data/multi_state_mask.json"
    out_bounds_path = "frontend/public/data/state_boundaries.json"
    
    with open(out_mask_path, 'w') as f:
        json.dump(geojson_mask, f)
    with open(out_bounds_path, 'w') as f:
        json.dump(geojson_bounds, f)
        
    print(f"Mask saved to {out_mask_path}")
    print(f"Boundaries saved to {out_bounds_path}")
else:
    print("Failed to fetch polygons.")