"""Minimal gallery-dl sidecar parsing (one-time filesystem-import aid).

No per-platform branching: a small common key set with fallbacks; the
full JSON is kept in raw so anything unmapped is recoverable later.
"""

import re
from dataclasses import dataclass
from datetime import UTC, datetime
from pathlib import Path


@dataclass(frozen=True)
class SidecarData:
    platform: str | None
    external_post_id: str | None
    post_url: str | None
    post_title: str | None
    description: str | None
    attachment_count: int | None
    post_date: datetime | None
    raw: dict


# gallery-dl prefixes media filenames with `NN_` for in-post ordering
# (`01_HOLLOW-ICHIGO.png`, `02_HOLOW ICHIGO.zip`) but writes the sidecar
# under the attachment's stem WITHOUT that ordering prefix
# (`HOLLOW-ICHIGO.json`). Strip the prefix when looking for sidecars.
# Confirmed against real Patreon downloads 2026-05-26 — without this
# strip, every gallery-dl post-level sidecar was invisible to FC since
# FC-3 shipped (24 deep-refresh calls produced 0 Posts in operator's DB).
_NUMBERING_PREFIX = re.compile(r"^\d+_(.+)$")


def find_sidecar(media: Path) -> Path | None:
    # Attachment-level sidecars (image.jpg.json, image.json).
    for cand in (media.with_suffix(".json"), Path(str(media) + ".json")):
        if cand.is_file():
            return cand
    # gallery-dl post-numbered convention: strip the `NN_` prefix from
    # the stem and look for that.json in the same directory.
    m = _NUMBERING_PREFIX.match(media.stem)
    if m:
        cand = media.parent / f"{m.group(1)}.json"
        if cand.is_file():
            return cand
    return None


def _first_str(data: dict, keys: tuple[str, ...]) -> str | None:
    for k in keys:
        v = data.get(k)
        if isinstance(v, str) and v.strip():
            return v.strip()
    return None


def _parse_date(v) -> datetime | None:
    if isinstance(v, bool):
        return None
    if isinstance(v, (int, float)):
        try:
            return datetime.fromtimestamp(v, tz=UTC)
        except (OverflowError, OSError, ValueError):
            return None
    if isinstance(v, str):
        s = v.strip()
        if not s:
            return None
        if s.endswith("Z"):
            s = s[:-1] + "+00:00"
        try:
            dt = datetime.fromisoformat(s)
        except ValueError:
            return None
        return dt if dt.tzinfo else dt.replace(tzinfo=UTC)
    return None


def parse_sidecar(data: dict) -> SidecarData:
    if not isinstance(data, dict):
        data = {}

    cat = data.get("category")
    platform = cat if isinstance(cat, str) and cat.strip() else None

    external_post_id = None
    for k in ("id", "post_id", "index", "message_id"):
        v = data.get(k)
        if isinstance(v, bool):
            continue
        if isinstance(v, (str, int)) and str(v).strip():
            external_post_id = str(v)
            break

    pc = data.get("page_count")
    if isinstance(pc, bool):
        attachment_count = None
    elif isinstance(pc, int) and pc > 0:
        attachment_count = pc
    elif isinstance(data.get("images"), list):
        attachment_count = len(data["images"])
    else:
        attachment_count = None

    post_date = None
    for k in ("published_at", "created_at", "date", "create_date",
              "timestamp"):
        if k in data:
            post_date = _parse_date(data[k])
            if post_date is not None:
                break

    return SidecarData(
        platform=platform,
        external_post_id=external_post_id,
        post_url=_first_str(data, ("url", "post_url")),
        post_title=_first_str(data, ("title",)),
        description=_first_str(data, ("content", "description", "caption")),
        attachment_count=attachment_count,
        post_date=post_date,
        raw=data,
    )