"""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


# Strip HTML tags + collapse whitespace + take the first non-empty line.
# Used to derive a display title from a body when the platform doesn't
# expose a separate title field (subscribestar posts always write
# `title: ""` and put the leading sentence inside `content` as HTML).
# Truncated to 120 chars with an ellipsis if longer — long enough to be
# meaningful in a feed, short enough to fit a row.
_TAG_RE = re.compile(r"<[^>]+>")
_WS_RE = re.compile(r"\s+")


def _first_line_text(body: str, limit: int = 120) -> str | None:
    if not body:
        return None
    text = _TAG_RE.sub(" ", body)
    text = text.replace("\xa0", " ")
    # Split on hard line breaks first; the body-stripped HTML often
    # collapses to one logical line, in which case the first sentence
    # split is the next-best heuristic.
    for line in text.splitlines():
        line = _WS_RE.sub(" ", line).strip()
        if line:
            if len(line) > limit:
                return line[: limit - 1].rstrip() + "…"
            return line
    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 lookup order: post_id MUST come before id.
    # SubscribeStar gallery-dl writes the per-attachment id in `id`
    # (e.g. 711509) and the actual post id in `post_id` (e.g. 360360);
    # picking `id` first fragments every multi-image subscribestar post
    # into N distinct Post rows in FC. Patreon/Pixiv have no `post_id`
    # so `id` still wins for them; HF uses `index`, Discord uses
    # `message_id` — all reached via the remaining chain entries.
    # Operator-flagged 2026-05-27 during the sidecar audit.
    external_post_id = None
    for k in ("post_id", "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

    # `message` is Discord gallery-dl's body field (no `content`); added
    # 2026-05-27 to the description fallback chain.
    description = _first_str(
        data, ("content", "description", "caption", "message"),
    )

    # SubscribeStar posts always write `title: ""` and put the leading
    # sentence inside `content` (confirmed against the operator's
    # /mnt/Data/Patreon/Cheunart/subscribestar/ dump 2026-05-27). When
    # no explicit title is present, synthesize one from the description
    # body's first non-empty line. Patreon retains its explicit titles
    # because they're non-empty and short-circuit the fallback.
    post_title = _first_str(data, ("title",))
    if post_title is None and description:
        post_title = _first_line_text(description)

    # post_url derivation: SubscribeStar/Pixiv/HF/Discord put the FILE
    # download URL in `url`, not a post permalink. Synthesize the
    # permalink from per-platform fields when possible. Patreon's `url`
    # IS a permalink and is used as-is. For the four file-URL platforms,
    # the bare `url` is NEVER trusted — derive or return None rather
    # than persist a CDN URL in post.post_url.
    if platform in _DERIVED_URL_PLATFORMS:
        post_url = _derive_post_url(platform, data)
    else:
        post_url = _first_str(data, ("url", "post_url"))

    return SidecarData(
        platform=platform,
        external_post_id=external_post_id,
        post_url=post_url,
        post_title=post_title,
        description=description,
        attachment_count=attachment_count,
        post_date=post_date,
        raw=data,
    )


_DERIVED_URL_PLATFORMS = frozenset({
    "subscribestar", "pixiv", "hentaifoundry", "discord",
})


def _derive_post_url(platform: str, data: dict) -> str | None:
    """Synthesize the post-permalink URL from per-platform metadata.

    gallery-dl writes the file-download URL in `url` for these four
    platforms; we need a real permalink for the PostCard "open original"
    button. Returns None if the platform-specific fields are missing
    (rare in well-formed sidecars but defensive).
    """
    if platform == "subscribestar":
        pid = data.get("post_id")
        if isinstance(pid, (str, int)) and str(pid).strip():
            return f"https://www.subscribestar.com/posts/{pid}"
    elif platform == "pixiv":
        pid = data.get("id")
        if isinstance(pid, (str, int)) and not isinstance(pid, bool) and str(pid).strip():
            return f"https://www.pixiv.net/artworks/{pid}"
    elif platform == "hentaifoundry":
        user = _first_str(data, ("user", "artist"))
        idx = data.get("index")
        if user and isinstance(idx, (str, int)) and not isinstance(idx, bool) and str(idx).strip():
            return f"https://www.hentai-foundry.com/pictures/user/{user}/{idx}"
    elif platform == "discord":
        sid = data.get("server_id")
        cid = data.get("channel_id")
        mid = data.get("message_id")
        if all(isinstance(v, (str, int)) and not isinstance(v, bool) and str(v).strip()
               for v in (sid, cid, mid)):
            return f"https://discord.com/channels/{sid}/{cid}/{mid}"
    return None