"""TMDb daily ID export fetching, for full-catalog bulk sync.

TMDb publishes a full list of every movie/TV/person/collection id that
exists in their database once a day, specifically to support this exact
use case -- syncing an entire local mirror is what these files are for,
as opposed to paginating `/discover`, which caps at 10,000 results per
query regardless of how many actually match.

Format: https://developer.themoviedb.org/docs/daily-id-exports -- a
gzipped file, one JSON object per line, e.g. for movies:
`{"adult":false,"id":3924,"original_title":"Blondie","popularity":1.61,"video":false}`.
Only `id` is used here; ingestion re-fetches full details per entity
through the normal provider pipeline (app/services/ingestion/), so
nothing else in the export line matters.
"""

from __future__ import annotations

import gzip
import io
import json
from datetime import date, timedelta

import httpx

from app.core.logging import get_logger

logger = get_logger(__name__)

_EXPORT_URL = "http://files.tmdb.org/p/exports/{kind}_ids_{date}.json.gz"

# Aurora's entity_type -> the TMDb export file's own name for that kind.
_EXPORT_KIND: dict[str, str] = {
    "movie": "movie",
    "series": "tv_series",
    "person": "person",
    "collection": "collection",
}


class DailyExportUnavailableError(Exception):
    pass


async def fetch_daily_export_ids(entity_type: str, *, client: httpx.AsyncClient) -> list[str]:
    """Fetch and parse today's (or, failing that, yesterday's) TMDb daily
    export for `entity_type`, returning every id as a string. TMDb
    publishes a new file once a day at a fixed time (early UTC morning);
    "today's" file may not exist yet depending on when this runs, so this
    tries today first and falls back to yesterday rather than failing."""

    kind = _EXPORT_KIND[entity_type]
    last_status: int | None = None
    for day_offset in (0, 1):
        export_date = date.today() - timedelta(days=day_offset)
        url = _EXPORT_URL.format(kind=kind, date=export_date.strftime("%m_%d_%Y"))
        response = await client.get(url, follow_redirects=True)
        if response.status_code == 200:
            ids = _parse_export(response.content)
            logger.info(
                "tmdb_daily_export_fetched", entity_type=entity_type, url=url, count=len(ids)
            )
            return ids
        last_status = response.status_code
        logger.info("tmdb_daily_export_not_found", url=url, status=response.status_code)

    raise DailyExportUnavailableError(
        f"no TMDb daily export found for {entity_type} (tried today and yesterday, "
        f"last status {last_status})"
    )


def _parse_export(raw_gzip: bytes) -> list[str]:
    ids: list[str] = []
    with gzip.GzipFile(fileobj=io.BytesIO(raw_gzip)) as f:
        for line in f:
            line = line.strip()
            if not line:
                continue
            ids.append(str(json.loads(line)["id"]))
    return ids