from fastapi import APIRouter, Depends, HTTPException, Query
from pydantic import BaseModel
from sqlalchemy.ext.asyncio import AsyncSession
from sqlalchemy import select
from datetime import datetime, timedelta
from collections import OrderedDict
import asyncio
import urllib.request
import urllib.parse
import urllib.error
import json

from app.database import get_db
from app.models.settings import Settings
from app.models.user import User
from app.config import settings as app_settings
from app.routers.auth import get_current_user, get_current_settings

router = APIRouter()

# SEC-15: Bounded LRU cache keyed by (user_id, location) — max 100 entries.
# OrderedDict preserves insertion order; move_to_end on hit, popitem(last=False)
# to evict the oldest when capacity is exceeded.
_CACHE_MAX = 100
_cache: OrderedDict = OrderedDict()


def _cache_get(key: tuple) -> dict | None:
    """Return cached entry if it exists and hasn't expired."""
    entry = _cache.get(key)
    if entry and datetime.now() < entry["expires_at"]:
        _cache.move_to_end(key)  # LRU: promote to most-recently-used
        return entry["data"]
    if entry:
        del _cache[key]  # expired — evict immediately
    return None


def _cache_set(key: tuple, data: dict) -> None:
    """Store an entry; evict the oldest if over capacity."""
    if key in _cache:
        _cache.move_to_end(key)
    _cache[key] = {"data": data, "expires_at": datetime.now() + timedelta(hours=1)}
    while len(_cache) > _CACHE_MAX:
        _cache.popitem(last=False)  # evict LRU (oldest)


class GeoSearchResult(BaseModel):
    name: str
    state: str
    country: str
    lat: float
    lon: float


def _fetch_json(url: str) -> dict:
    with urllib.request.urlopen(url, timeout=10) as resp:
        return json.loads(resp.read().decode())


@router.get("/search", response_model=list[GeoSearchResult])
async def search_locations(
    q: str = Query(..., min_length=1, max_length=100),
    current_user: User = Depends(get_current_user)
):
    api_key = app_settings.OPENWEATHERMAP_API_KEY
    if not api_key:
        raise HTTPException(status_code=500, detail="Weather API key not configured")

    try:
        loop = asyncio.get_running_loop()
        url = f"https://api.openweathermap.org/geo/1.0/direct?q={urllib.parse.quote(q)}&limit=5&appid={api_key}"
        results = await loop.run_in_executor(None, _fetch_json, url)

        return [
            {
                "name": r.get("name", ""),
                "state": r.get("state", ""),
                "country": r.get("country", ""),
                "lat": r.get("lat"),
                "lon": r.get("lon"),
            }
            for r in results
        ]
    except urllib.error.URLError:
        raise HTTPException(status_code=502, detail="Geocoding service unavailable")
    except (KeyError, json.JSONDecodeError):
        raise HTTPException(status_code=502, detail="Invalid geocoding data")


@router.get("/")
async def get_weather(
    db: AsyncSession = Depends(get_db),
    current_user: User = Depends(get_current_user),
    current_settings: Settings = Depends(get_current_settings),
):
    city = current_settings.weather_city
    lat = current_settings.weather_lat
    lon = current_settings.weather_lon

    if not city and (lat is None or lon is None):
        raise HTTPException(status_code=400, detail="No weather location configured")

    # Cache key includes user_id so each user gets isolated cache entries
    use_coords = lat is not None and lon is not None
    location_key = f"{lat},{lon}" if use_coords else city
    cache_key = (current_user.id, location_key)

    cached = _cache_get(cache_key)
    if cached is not None:
        return cached

    api_key = app_settings.OPENWEATHERMAP_API_KEY
    if not api_key:
        raise HTTPException(status_code=500, detail="Weather API key not configured")

    try:
        loop = asyncio.get_running_loop()

        # Build query params based on coordinates or city name
        if use_coords:
            location_params = f"lat={lat}&lon={lon}"
        else:
            location_params = f"q={urllib.parse.quote(city)}"

        current_url = f"https://api.openweathermap.org/data/2.5/weather?{location_params}&units=metric&appid={api_key}"
        forecast_url = f"https://api.openweathermap.org/data/2.5/forecast?{location_params}&units=metric&cnt=8&appid={api_key}"

        current_data, forecast_data = await asyncio.gather(
            loop.run_in_executor(None, _fetch_json, current_url),
            loop.run_in_executor(None, _fetch_json, forecast_url),
        )

        rain_chance = 0
        for item in forecast_data.get("list", []):
            pop = item.get("pop", 0)
            if pop > rain_chance:
                rain_chance = pop

        weather_result = {
            "temp": round(current_data["main"]["temp"]),
            "temp_min": round(current_data["main"]["temp_min"]),
            "temp_max": round(current_data["main"]["temp_max"]),
            "description": current_data["weather"][0]["description"],
            "rain_chance": round(rain_chance * 100),
            "sunrise": current_data["sys"]["sunrise"],
            "sunset": current_data["sys"]["sunset"],
            "city": current_data["name"],
        }

        _cache_set(cache_key, weather_result)
        return weather_result

    except urllib.error.URLError:
        raise HTTPException(status_code=502, detail="Weather service unavailable")
    except (KeyError, json.JSONDecodeError):
        raise HTTPException(status_code=502, detail="Invalid weather data")