"""Download Copernicus DEM GLO-30 COG tiles for an AOI."""

from __future__ import annotations

import argparse
import math
from pathlib import Path
from urllib.error import HTTPError, URLError
from urllib.request import urlretrieve

COPERNICUS_DEM_30M_BASE_URL = "https://copernicus-dem-30m.s3.amazonaws.com"


def parse_bbox(raw: str) -> tuple[float, float, float, float]:
    parts = [float(part.strip()) for part in raw.split(",")]
    if len(parts) != 4:
        raise argparse.ArgumentTypeError("bbox must be minlon,minlat,maxlon,maxlat")
    minlon, minlat, maxlon, maxlat = parts
    if minlon >= maxlon or minlat >= maxlat:
        raise argparse.ArgumentTypeError("bbox min values must be lower than max values")
    return minlon, minlat, maxlon, maxlat


def _hemisphere(value: int, positive: str, negative: str) -> str:
    return positive if value >= 0 else negative


def tile_name(lat: int, lon: int) -> str:
    lat_prefix = _hemisphere(lat, "N", "S")
    lon_prefix = _hemisphere(lon, "E", "W")
    return (
        f"Copernicus_DSM_COG_10_{lat_prefix}{abs(lat):02d}_00_"
        f"{lon_prefix}{abs(lon):03d}_00_DEM"
    )


def tile_url(lat: int, lon: int) -> str:
    name = tile_name(lat, lon)
    return f"{COPERNICUS_DEM_30M_BASE_URL}/{name}/{name}.tif"


def tiles_for_bbox(bbox: tuple[float, float, float, float]) -> list[tuple[int, int]]:
    minlon, minlat, maxlon, maxlat = bbox
    lats = range(math.floor(minlat), math.ceil(maxlat))
    lons = range(math.floor(minlon), math.ceil(maxlon))
    return [(lat, lon) for lat in lats for lon in lons]


def parse_args() -> argparse.Namespace:
    parser = argparse.ArgumentParser(description="Bootstrap Copernicus DEM for an AOI")
    parser.add_argument("--bbox", required=True, type=parse_bbox, help="minlon,minlat,maxlon,maxlat")
    parser.add_argument("--output-dir", default=Path("data/dem"), type=Path)
    parser.add_argument("--overwrite", action="store_true", help="Re-download existing tiles")
    return parser.parse_args()


def main() -> None:
    args = parse_args()
    args.output_dir.mkdir(parents=True, exist_ok=True)
    downloaded = 0
    skipped = 0
    failed: list[str] = []

    for lat, lon in tiles_for_bbox(args.bbox):
        name = tile_name(lat, lon)
        destination = args.output_dir / f"{name}.tif"
        if destination.exists() and not args.overwrite:
            skipped += 1
            print(f"skip existing {destination}")
            continue

        url = tile_url(lat, lon)
        print(f"download {url}")
        try:
            urlretrieve(url, destination)
        except (HTTPError, URLError) as exc:
            failed.append(f"{name}: {exc}")
            if destination.exists():
                destination.unlink()
            continue
        downloaded += 1

    print(f"downloaded={downloaded} skipped={skipped} failed={len(failed)}")
    if failed:
        for item in failed:
            print(f"failed {item}")
        raise SystemExit(1)


if __name__ == "__main__":
    main()