"""Download TuneECU Triumph map files into a local cache for the viewer.

The viewer can render any of these from a dropdown (when served over HTTP, since
browsers block fetch() on file://). Maps come from the same endpoint the TuneECU
app uses: https://www.tuneecu.fr/Maps/<path>  (found in the decompile).

    python3 download_maps.py                     # mechanical-odo Bonneville set
    python3 download_maps.py --filter Bonneville # all Bonneville twin maps
    python3 download_maps.py 20187 20188 20262   # specific map numbers
    python3 download_maps.py --all-twins         # every Triumph twin (~big)

Writes maps_cache/<n>Map.hex and maps_cache/index.json (id + description).
"""

from __future__ import annotations

import argparse
import json
import sys
import urllib.request
from pathlib import Path

BASE = "https://www.tuneecu.fr/Maps/"
LIST_URL = BASE + "mapList.dat"
CACHE = Path(__file__).parent / "maps_cache"
MAPS_JSON = Path(__file__).parent / "maps.json"

# Default: the 2010 mechanical-odometer Bonneville candidates.
DEFAULT_IDS = ["20187", "20188", "20191", "20192"]


def _get(url: str) -> bytes:
    req = urllib.request.Request(url, headers={"User-Agent": "tunie"})
    with urllib.request.urlopen(req, timeout=30) as r:
        return r.read()


def _map_list() -> list[str]:
    """Return the '<path>/<n>Map.hex' entries from the server's map list."""
    text = _get(LIST_URL).decode("latin1")
    return [ln.strip() for ln in text.splitlines() if ln.strip().endswith("Map.hex")]


def _descriptions() -> dict[str, list[str]]:
    if not MAPS_JSON.exists():
        return {}
    return {m["id"]: m["description"] for m in json.loads(MAPS_JSON.read_text())}


def main() -> int:
    ap = argparse.ArgumentParser()
    ap.add_argument("ids", nargs="*", help="specific map numbers to fetch")
    ap.add_argument("--filter", help="download every map whose path contains this substring")
    ap.add_argument("--all-twins", action="store_true", help="all Triumph twin maps")
    args = ap.parse_args()

    entries = _map_list()  # e.g. "Triumph/Bonneville/20187Map.hex"
    if args.ids:
        wanted = [e for e in entries if any(f"/{i}Map.hex" in e for i in args.ids)]
    elif args.all_twins:
        wanted = [e for e in entries if e.startswith("Triumph/")
                  and any(k in e for k in ("Bonneville", "Thruxton", "Scrambler",
                                           "America", "Speedmaster"))]
    elif args.filter:
        wanted = [e for e in entries if args.filter.lower() in e.lower()]
    else:
        wanted = [e for e in entries if any(f"/{i}Map.hex" in e for i in DEFAULT_IDS)]

    if not wanted:
        print("Nothing matched.", file=sys.stderr)
        return 1

    CACHE.mkdir(exist_ok=True)
    descs = _descriptions()
    index = []
    for path in wanted:
        fname = path.rsplit("/", 1)[-1]           # 20187Map.hex
        num = fname.replace("Map.hex", "")
        dest = CACHE / fname
        if not dest.exists():
            try:
                data = _get(BASE + path)
            except Exception as exc:
                print(f"  skip {fname}: {exc}", file=sys.stderr)
                continue
            dest.write_bytes(data)
            print(f"  got {fname} ({len(data)} bytes)")
        index.append({"file": fname, "id": num,
                      "desc": descs.get(num, [num])})

    index.sort(key=lambda x: x["id"])
    (CACHE / "index.json").write_text(json.dumps(index, indent=2))
    print(f"\n{len(index)} maps in {CACHE}/  (index.json written)")
    print("Serve them with:  python3 serve.py   then use the catalogue dropdown.")
    return 0


if __name__ == "__main__":
    raise SystemExit(main())