"""Lightweight, dependency-free geocoding.

We deliberately avoid calling an external geocoding API per-article (rate
limits, latency, privacy) and avoid a heavyweight NER model. Instead we match
article text against a curated gazetteer of cities/regions/countries
(app/data/gazetteer.csv), preferring the most specific (longest) name found.
This is a heuristic: it will miss unlisted places and can occasionally match
the wrong entity for very generic names. Extend data/gazetteer.csv to
improve coverage.
"""

import csv
import re
from dataclasses import dataclass
from functools import lru_cache

from .config import settings


@dataclass(frozen=True)
class Place:
    name: str
    lat: float
    lon: float
    type: str
    country: str


def _load_gazetteer() -> list[Place]:
    places: list[Place] = []
    with open(settings.gazetteer_file, newline="", encoding="utf-8") as f:
        for row in csv.DictReader(f):
            places.append(
                Place(
                    name=row["name"],
                    lat=float(row["lat"]),
                    lon=float(row["lon"]),
                    type=row["type"],
                    country=row["country"],
                )
            )
    # Longest name first so "Gaza Strip" wins over "Gaza", "New York" over "York", etc.
    places.sort(key=lambda p: len(p.name), reverse=True)
    return places


@lru_cache(maxsize=1)
def _gazetteer() -> list[tuple[re.Pattern, Place]]:
    compiled = []
    for place in _load_gazetteer():
        pattern = re.compile(r"\b" + re.escape(place.name) + r"\b", re.IGNORECASE)
        compiled.append((pattern, place))
    return compiled


def locate(text: str) -> Place | None:
    """Return the most specific gazetteer place mentioned in `text`, if any."""
    if not text:
        return None
    for pattern, place in _gazetteer():
        if pattern.search(text):
            return place
    return None


def cluster_key_for(lat: float, lon: float) -> str:
    """Grid-snap coordinates (~11km cells) so nearby stories share a bucket."""
    return f"{round(lat, 1)}:{round(lon, 1)}"