"""
Skriv og les bib-metadata i bildefiler via EXIF UserComment (JSON).

Bruker piexif + Pillow som allerede er i requirements.txt.
Metadata lagres i Exif.UserComment som:
  b"ASCII\x00\x00\x00" + JSON-bytes

Eksempel-innhold:
  {"bibs": ["42", "87"], "station": "finish", "confidence": 0.93, "confirmed": true}
"""

import json
import logging
from pathlib import Path
from typing import Optional

import piexif
from PIL import Image

logger = logging.getLogger(__name__)

_ASCII_PREFIX = b"ASCII\x00\x00\x00"


def write_bib_tags(
    image_path: Path,
    bibs: list[str],
    *,
    station: Optional[str] = None,
    race_id: Optional[str] = None,
    confidence: Optional[float] = None,
    confirmed: bool = False,
) -> None:
    """
    Skriv startnummer-metadata til bildefil som EXIF UserComment (JSON).
    Bevarer all eksisterende EXIF. Feiler stille — krasjer ikke ingest-prosessen.
    """
    data: dict = {"bibs": bibs}
    if station:
        data["station"] = station
    if race_id:
        data["race_id"] = race_id
    if confidence is not None:
        data["confidence"] = round(confidence, 4)
    if confirmed:
        data["confirmed"] = True

    json_bytes = json.dumps(data, ensure_ascii=True, separators=(",", ":")).encode("ascii")
    comment_bytes = _ASCII_PREFIX + json_bytes

    try:
        img = Image.open(image_path)
        raw_exif = img.info.get("exif")
        if raw_exif:
            exif_dict = piexif.load(raw_exif)
        else:
            exif_dict = {"0th": {}, "Exif": {}, "GPS": {}, "Interop": {}, "1st": {}}

        exif_dict.setdefault("Exif", {})[piexif.ExifIFD.UserComment] = comment_bytes
        new_exif = piexif.dump(exif_dict)

        # Lagre til midlertidig fil, rename for atomisk skriving
        tmp = image_path.with_suffix(".tmp" + image_path.suffix)
        img.save(tmp, exif=new_exif)
        tmp.replace(image_path)

        logger.debug("EXIF-tags skrevet til %s: bibs=%s", image_path.name, bibs)
    except Exception as e:
        logger.warning("Kunne ikke skrive EXIF-tags til %s: %s", image_path, e)


def read_bib_tags(image_path: Path) -> Optional[dict]:
    """
    Les startnummer-metadata fra EXIF UserComment.
    Returnerer dict (med nøkkel 'bibs') eller None hvis ikke satt.
    """
    try:
        img = Image.open(image_path)
        raw_exif = img.info.get("exif")
        if not raw_exif:
            return None
        exif_dict = piexif.load(raw_exif)
        comment = exif_dict.get("Exif", {}).get(piexif.ExifIFD.UserComment)
        if not comment or not comment.startswith(_ASCII_PREFIX):
            return None
        json_str = comment[len(_ASCII_PREFIX):].decode("ascii", errors="replace")
        return json.loads(json_str)
    except Exception:
        return None