"""Thumbnail endpoint: previews addressed only by asset ID and bounded size.

The browser never supplies a filesystem path. Errors return a consistent JSON
envelope with the service's typed code and status; successful responses carry the
image with an immutable cache header (the URL's identity comes from the versioned,
content-keyed cache).
"""

from __future__ import annotations

from fastapi import APIRouter, Query, Request
from fastapi.responses import FileResponse, JSONResponse

from photo_pipeline.services.thumbnails import ThumbnailError, ThumbnailService

router = APIRouter(tags=["thumbnails"])


@router.get("/assets/{asset_id}/thumbnail")
def get_thumbnail(asset_id: str, request: Request, size: int = Query(512)):
    service = ThumbnailService(
        request.app.state.session_factory, request.app.state.config
    )
    try:
        path = service.generate(asset_id, size)
    except ThumbnailError as error:
        return JSONResponse(
            status_code=error.http_status,
            content={"error": {"code": error.code, "message": str(error)}},
        )
    return FileResponse(
        path,
        media_type="image/webp",
        # private: the URL is versioned and immutable, but these bytes are the user's
        # photos and must never sit in a shared cache (US07-02).
        headers={"Cache-Control": "private, max-age=31536000, immutable"},
    )