"""Export MongoDB info_items collection to an Excel file."""

from __future__ import annotations

import os
import sys
from pathlib import Path
from typing import Any, Dict, Iterable, List, Optional

import pandas as pd
from pymongo import MongoClient
from pymongo.errors import PyMongoError


MONGO_URI = os.getenv("MONGO_URI", "mongodb://localhost:27017")
MONGO_DB = os.getenv("MONGO_DB", "haier")
MONGO_COLLECTION = os.getenv("MONGO_COLLECTION", "info_items")
DEFAULT_OUTPUT = Path(__file__).resolve().parent.parent / "exports" / "info_items.xlsx"
FETCH_BATCH_SIZE = 2000


def _ensure_output_dir(path: Path) -> None:
    path.parent.mkdir(parents=True, exist_ok=True)


def _iter_docs(
    collection, query: Optional[Dict[str, Any]] = None
) -> Iterable[Dict[str, Any]]:
    cursor = collection.find(query or {}, batch_size=FETCH_BATCH_SIZE)
    for doc in cursor:
        # Convert ObjectId to string for Excel friendliness.
        if "_id" in doc:
            doc["_id"] = str(doc["_id"])
        yield doc


def export_to_excel(output_path: Path, query: Optional[Dict[str, Any]] = None) -> Path:
    """Fetch documents and write them to an Excel file.

    Parameters
    ----------
    output_path : Path
        Destination Excel path. Directories are created if missing.
    query : Optional[Dict[str, Any]]
        Optional MongoDB query filter.
    """

    client = MongoClient(MONGO_URI)
    collection = client[MONGO_DB][MONGO_COLLECTION]

    _ensure_output_dir(output_path)

    docs: List[Dict[str, Any]] = list(_iter_docs(collection, query))
    if not docs:
        # Create an empty file with a header to indicate no data.
        pd.DataFrame().to_excel(output_path, index=False)
        return output_path

    df = pd.DataFrame(docs)
    df.to_excel(output_path, index=False)
    return output_path


def main(argv: List[str]) -> int:
    """CLI entry point. Usage: python export_info_to_excel.py [output_path]"""

    output_path = Path(argv[1]) if len(argv) > 1 else DEFAULT_OUTPUT
    try:
        result_path = export_to_excel(output_path)
    except (
        PyMongoError,
        OSError,
        ValueError,
    ) as exc:  # pragma: no cover - defensive runtime path
        print(f"Export failed: {exc}", file=sys.stderr)
        return 1

    print(f"Export completed: {result_path}")
    return 0


if __name__ == "__main__":
    raise SystemExit(main(sys.argv))