"""Serve cached DOM.РФ photos.

GET /api/v1/photos/{obj_id}/{file_id}?size=thumb|full

- size=thumb (default): WebP 320×240 from local cache. If thumb is missing
  but the original is present locally, generate one on the fly. If neither
  is present, redirect to the upstream DOM.РФ URL.
- size=full: original PNG/JPG if cached locally, else redirect upstream.

This isolates the frontend grid from upstream latency and from Next.js dev-mode
optimizer cold-hit cost.
"""

from __future__ import annotations

import logging
from pathlib import Path
from typing import Annotated, Literal

from fastapi import APIRouter, Depends, HTTPException, Query
from fastapi.responses import FileResponse, RedirectResponse, Response
from sqlalchemy import text
from sqlalchemy.orm import Session

from app.core.db import get_db
from app.services.photos.thumbs import make_thumbnail

logger = logging.getLogger(__name__)
router = APIRouter()


_PHOTO_LOOKUP_SQL = text(
    """
    SELECT local_path, thumb_path, photo_url
      FROM domrf_kn_photos
     WHERE obj_id = :obj AND obj_file_id = :fid
     LIMIT 1
    """
)


@router.get("/{obj_id}/{file_id}")
def get_photo(
    db: Annotated[Session, Depends(get_db)],
    obj_id: int,
    file_id: str,
    size: Annotated[Literal["thumb", "full"], Query()] = "thumb",
) -> Response:
    row = db.execute(_PHOTO_LOOKUP_SQL, {"obj": obj_id, "fid": file_id}).mappings().first()
    if not row:
        raise HTTPException(status_code=404, detail="photo not registered")

    local_path = row["local_path"]
    thumb_path = row["thumb_path"]
    upstream = row["photo_url"]

    headers = {"Cache-Control": "public, max-age=604800, immutable"}

    if size == "full":
        if local_path and Path(local_path).exists():
            return FileResponse(local_path, headers=headers)
        if upstream:
            return RedirectResponse(upstream, status_code=302)
        raise HTTPException(status_code=404, detail="full photo unavailable")

    # size=thumb
    if thumb_path and Path(thumb_path).exists():
        return FileResponse(thumb_path, media_type="image/webp", headers=headers)

    # Generate thumb on the fly from cached original
    if local_path and Path(local_path).exists():
        generated = make_thumbnail(Path(local_path))
        if generated and generated.exists():
            db.execute(
                text(
                    "UPDATE domrf_kn_photos SET thumb_path = :tp"
                    " WHERE obj_id = :o AND obj_file_id = :f"
                ),
                {"tp": str(generated), "o": obj_id, "f": file_id},
            )
            db.commit()
            return FileResponse(str(generated), media_type="image/webp", headers=headers)

    # Last resort — redirect to upstream so the page still renders
    if upstream:
        return RedirectResponse(upstream, status_code=302)
    raise HTTPException(status_code=404, detail="photo unavailable")