"""
EXIF-Aufnahmedatum/-zeit aus Bildbytes (JPEG, PNG mit EXIF, …).

EXIF enthält keine Zeitzone; wir interpretieren die Wandzeit in PHOTO_EXIF_TIMEZONE
(Standard Europe/Berlin) und speichern als TIMESTAMPTZ (UTC in PostgreSQL).
"""
from __future__ import annotations

import os
from datetime import datetime, timezone
from io import BytesIO
from typing import Optional
from zoneinfo import ZoneInfo

from PIL import Image

EXIF_DATETIME_FMT = "%Y:%m:%d %H:%M:%S"
_EXIF_IFD = 0x8769
_EXIF_DATETIME_TAGS = (36867, 36868)  # DateTimeOriginal, DateTimeDigitized
_TAG_DATETIME_MAIN = 306


def extract_taken_at_from_image_bytes(raw: bytes) -> Optional[datetime]:
    """
    Liest DateTimeOriginal (o. ä.) aus EXIF und gibt ein timezone-aware datetime zurück,
    oder None wenn nicht ermittelbar.
    """
    try:
        img = Image.open(BytesIO(raw))
    except Exception:
        return None
    try:
        naive = _extract_exif_naive_datetime(img)
    finally:
        try:
            img.close()
        except Exception:
            pass
    if naive is None:
        return None
    tz_name = os.getenv("PHOTO_EXIF_TIMEZONE", "Europe/Berlin")
    try:
        tz = ZoneInfo(tz_name)
    except Exception:
        tz = ZoneInfo("Europe/Berlin")
    return naive.replace(tzinfo=tz)


def _extract_exif_naive_datetime(img: Image.Image) -> Optional[datetime]:
    exif = img.getexif()
    if not exif:
        return None
    strings: list[str] = []
    try:
        exif_ifd = exif.get_ifd(_EXIF_IFD)
    except Exception:
        exif_ifd = None
    if exif_ifd:
        for tag in _EXIF_DATETIME_TAGS:
            v = exif_ifd.get(tag)
            if isinstance(v, str) and v.strip():
                strings.append(v)
    v = exif.get(_TAG_DATETIME_MAIN)
    if isinstance(v, str) and v.strip():
        strings.append(v)
    for s in strings:
        dt = _parse_exif_datetime_str(s)
        if dt:
            return dt
    return None


def _parse_exif_datetime_str(s: str) -> Optional[datetime]:
    s = (s or "").strip()
    if not s:
        return None
    try:
        return datetime.strptime(s, EXIF_DATETIME_FMT)
    except ValueError:
        return None


def taken_at_from_file_last_modified_ms(ms_raw: Optional[str]) -> Optional[datetime]:
    """
    Browser sendet File.lastModified (ms seit UTC-Epoch), echte Dateirevision auf der Platte.
    Wird als echter Zeitpunkt interpretiert und nach PHOTO_EXIF_TIMEZONE für Anzeige gelegt
    (konsistent zu EXIF-Wandzeit).
    """
    if not ms_raw or not str(ms_raw).strip():
        return None
    try:
        ms = int(str(ms_raw).strip())
    except ValueError:
        return None
    if ms <= 0:
        return None
    instant_utc = datetime.fromtimestamp(ms / 1000.0, tz=timezone.utc)
    tz_name = os.getenv("PHOTO_EXIF_TIMEZONE", "Europe/Berlin")
    try:
        tz = ZoneInfo(tz_name)
    except Exception:
        tz = ZoneInfo("Europe/Berlin")
    return instant_utc.astimezone(tz)