"""Reader factory: CSV, fast calamine (xlsx), or streaming iterparse fallback."""
from __future__ import annotations

import os

from .xlsx_reader import TransactionReader


def _calamine_available() -> bool:
    if os.environ.get("AR_USE_CALAMINE", "1") == "0":
        return False
    try:
        import python_calamine  # noqa: F401
        return True
    except Exception:
        return False


def make_reader(path: str, saved_overrides: dict[str, str] | None = None):
    """
    Return a reader with the TransactionReader interface (detect/iter_records/file_meta/close).

    CSV reports (Amazon "Custom Unified Transaction" downloads) use CsvReader. Spreadsheets
    use python-calamine when available (much faster, higher peak memory); otherwise the
    low-memory streaming reader. Set AR_USE_CALAMINE=0 to force the streaming reader.
    """
    ext = os.path.splitext(path)[1].lower()
    if ext == ".csv":
        from .csv_reader import CsvReader
        return CsvReader(path, saved_overrides=saved_overrides)
    if _calamine_available():
        from .calamine_reader import CalamineReader
        return CalamineReader(path, saved_overrides=saved_overrides)
    return TransactionReader(path, saved_overrides=saved_overrides)