"""Fetch monthly MERRA-2 weather over Ukraine from NASA POWER (regional grid endpoint).

Usage: python3 -I fetch_power.py <out_dir>
Writes one CSV per parameter: lat, lon, yyyymm, value. Month 13 (annual) is dropped.
"""
import csv
import json
import os
import sys
import time
import urllib.request

PARAMS = ["T2M_MAX", "PRECTOTCORR", "RH2M", "GWETTOP"]
BOXES = [(44.0, 52.5, 22.0, 31.0), (44.0, 52.5, 31.0, 40.5)]
URL = ("https://power.larc.nasa.gov/api/temporal/monthly/regional?"
       "latitude-min={a}&latitude-max={b}&longitude-min={c}&longitude-max={d}"
       "&parameters={p}&community=AG&start=2001&end=2025&format=JSON")


def get(url, tries=5):
    for i in range(tries):
        try:
            with urllib.request.urlopen(url, timeout=180) as r:
                return json.load(r)
        except Exception as e:  # noqa: BLE001
            print("retry", i, e, flush=True)
            time.sleep(3 + 3 * i)
    raise RuntimeError("failed " + url)


def main(out_dir):
    os.makedirs(out_dir, exist_ok=True)
    for p in PARAMS:
        out = os.path.join(out_dir, f"power_{p}.csv")
        if os.path.exists(out):
            print(p, "cached")
            continue
        rows = []
        for a, b, c, d in BOXES:
            js = get(URL.format(a=a, b=b, c=c, d=d, p=p))
            for f in js["features"]:
                lon, lat = f["geometry"]["coordinates"][:2]
                for k, v in f["properties"]["parameter"][p].items():
                    if k.endswith("13"):
                        continue
                    rows.append((lat, lon, k, v))
        with open(out, "w", newline="") as fh:
            w = csv.writer(fh)
            w.writerow(["lat", "lon", "yyyymm", "value"])
            w.writerows(rows)
        print(p, len(rows), "rows", flush=True)


if __name__ == "__main__":
    main(sys.argv[1])