"""Persist agent traces to a Hugging Face dataset repo.

Uses `huggingface_hub.CommitScheduler`: the `traces/` folder is committed to a
dataset repo in the background every minute (only new/changed files are
uploaded). This is the recommended pattern for persisting data from a Space —
ZeroGPU Spaces have ephemeral disks, so without this every trace is lost on
restart.

Configuration (env vars):
  HF_TOKEN             write token; on Spaces add it as a secret. Required.
  TRACES_DATASET_REPO  dataset repo id, e.g. "you/hugging-wizards-traces".
                       Defaults to "<SPACE_ID>-traces" when running on a Space.
  TRACES_DATASET_PRIVATE  "0" to create the dataset public (default private).

If the token or repo id is missing, syncing is disabled and the game runs
exactly as before (traces still land on local disk).
"""
from __future__ import annotations

import contextlib
import os

_scheduler = None
_disabled = False


def _repo_id() -> str | None:
    repo = os.environ.get("TRACES_DATASET_REPO")
    if repo:
        return repo
    space = os.environ.get("SPACE_ID")  # "owner/space-name" on HF Spaces
    return f"{space}-traces" if space else None


def start(trace_dir: str):
    """Begin background sync of `trace_dir` to the dataset repo (idempotent)."""
    global _scheduler, _disabled
    if _scheduler is not None or _disabled:
        return _scheduler

    token = os.environ.get("HF_TOKEN") or os.environ.get("HUGGING_FACE_HUB_TOKEN")
    repo = _repo_id()
    if not token or not repo:
        _disabled = True
        print("[trace_store] HF sync disabled "
              "(set HF_TOKEN and TRACES_DATASET_REPO to enable)")
        return None

    try:
        from huggingface_hub import CommitScheduler

        _scheduler = CommitScheduler(
            repo_id=repo,
            repo_type="dataset",
            folder_path=trace_dir,
            path_in_repo="traces",
            every=1,  # minutes
            private=os.environ.get("TRACES_DATASET_PRIVATE", "1") != "0",
            allow_patterns=["*.json"],
            token=token,
        )
        print(f"[trace_store] syncing traces to dataset {repo} every minute")
    except Exception as e:  # never let trace upload break the game
        _disabled = True
        print(f"[trace_store] HF sync disabled: {e}")
    return _scheduler


def lock():
    """Lock to hold while writing trace files, so a half-written file is
    never committed. A no-op context manager when syncing is disabled."""
    if _scheduler is not None:
        return _scheduler.lock
    return contextlib.nullcontext()