"""Read atomic public result revisions from a Dataset without rebuilding the Space."""
import json
import logging
import os
import shutil
from pathlib import Path
import threading
import time


class ResultFeed:
    def __init__(self, fallback, repo_id=None, cache_dir=None):
        self.current = str(fallback)
        self.repo_id = repo_id or os.getenv("HF_RESULTS_REPO")
        self.cache_dir = Path(cache_dir or Path(fallback).parent / ".result-cache")
        self.revision = None
        self.checked_at = 0.0
        self.lock = threading.Lock()

    def refresh(self):
        if not self.repo_id:
            return self.current
        with self.lock:
            if time.monotonic() - self.checked_at < 30:
                return self.current
            self.checked_at = time.monotonic()
            try:
                from huggingface_hub import HfApi, snapshot_download
                revision = HfApi(token=False).dataset_info(self.repo_id, timeout=15).sha
                if revision == self.revision:
                    return self.current
                destination = self.cache_dir / revision
                snapshot_download(self.repo_id, repo_type="dataset", revision=revision,
                                  allow_patterns=["results/**"], local_dir=destination,
                                  token=False, max_workers=4)
                results = destination / "results"
                status = json.loads((results / "online_status.json").read_text())
                if status.get("aggregate_status") != "ok" or not list(results.glob("*/all_results.csv")):
                    raise ValueError("Incomplete result revision")
                # Readers receive a complete immutable directory, never half an upload.
                self.current = str(results)
                self.revision = revision
                # Leave recent revisions long enough for in-flight UI callbacks.
                for old in self.cache_dir.iterdir():
                    if old.is_dir() and old != destination and time.time() - old.stat().st_mtime > 600:
                        shutil.rmtree(old)
            except Exception:
                logging.exception("Result feed unavailable; retaining the last complete revision")
        return self.current