weatherpred/data.py

"""Open-Meteo data fetching and local CSV/JSON cache helpers."""

from __future__ import annotations

import json
from datetime import date, datetime, timedelta, timezone
from typing import Any

import numpy as np
import pandas as pd
import requests

from weatherpred.config import (
    DAILY_COLUMNS,
    DATA_DIR,
    FORECAST_DAYS,
    HISTORY_CSV_PATH,
    HISTORY_JSON_PATH,
    HISTORY_YEARS,
    LATEST_JSON_PATH,
    TOKYO_LATITUDE,
    TOKYO_LONGITUDE,
    TOKYO_TIMEZONE,
)


def fetch_json(url: str, params: dict[str, str | float | int]) -> dict[str, Any]:
    response = requests.get(url, params=params, timeout=40)
    response.raise_for_status()
    return response.json()


def normalize_daily_weather(raw: dict[str, Any], observed: bool) -> pd.DataFrame:
    daily = raw["daily"]
    frame = pd.DataFrame(
        {
            "date": pd.to_datetime(daily["time"]),
            "high_c": daily["temperature_2m_max"],
            "low_c": daily["temperature_2m_min"],
            "rain_mm": daily["precipitation_sum"],
            "wind_kmh": daily["wind_speed_10m_max"],
        }
    )
    frame["confidence"] = 1.0 if observed else np.nan
    return frame.dropna(subset=["high_c", "low_c", "rain_mm", "wind_kmh"])


def fetch_historical_weather(
    years: int = HISTORY_YEARS,
    latitude: float = TOKYO_LATITUDE,
    longitude: float = TOKYO_LONGITUDE,
) -> pd.DataFrame:
    end = date.today() - timedelta(days=1)
    start = end.replace(year=end.year - years)
    params = {
        "latitude": latitude,
        "longitude": longitude,
        "timezone": TOKYO_TIMEZONE,
        "start_date": start.isoformat(),
        "end_date": end.isoformat(),
        "daily": ",".join(DAILY_COLUMNS),
    }
    raw = fetch_json("https://archive-api.open-meteo.com/v1/archive", params)
    return normalize_daily_weather(raw, observed=True)


def fetch_api_forecast(
    latitude: float = TOKYO_LATITUDE,
    longitude: float = TOKYO_LONGITUDE,
    days: int = FORECAST_DAYS,
) -> pd.DataFrame:
    params = {
        "latitude": latitude,
        "longitude": longitude,
        "timezone": TOKYO_TIMEZONE,
        "forecast_days": days,
        "current": "temperature_2m,precipitation,wind_speed_10m",
        "daily": ",".join(DAILY_COLUMNS),
    }
    raw = fetch_json("https://api.open-meteo.com/v1/forecast", params)
    latest = {
        "fetched_at": datetime.now(timezone.utc).isoformat(),
        "current": raw.get("current", {}),
        "daily": raw.get("daily", {}),
    }
    DATA_DIR.mkdir(parents=True, exist_ok=True)
    LATEST_JSON_PATH.write_text(json.dumps(latest, indent=2) + "\n", encoding="utf-8")
    return normalize_daily_weather(raw, observed=False)


def save_history(history: pd.DataFrame) -> None:
    DATA_DIR.mkdir(parents=True, exist_ok=True)
    history.to_csv(HISTORY_CSV_PATH, index=False)
    HISTORY_JSON_PATH.write_text(
        history.assign(date=history["date"].dt.strftime("%Y-%m-%d")).to_json(
            orient="records", indent=2
        )
        + "\n",
        encoding="utf-8",
    )


def load_or_fetch_history(force_refresh: bool = False) -> pd.DataFrame:
    if HISTORY_CSV_PATH.exists() and not force_refresh:
        return pd.read_csv(HISTORY_CSV_PATH, parse_dates=["date"])
    history = fetch_historical_weather()
    save_history(history)
    return history