"""Utils."""

from datetime import date
from typing import Any, Generator, Optional

from dateutil.parser import parse

# Cells starting with any of these are evaluated as formulas by Excel /
# LibreOffice when a report is opened for review. Prefix with `'` to
# neutralise — the apostrophe is stripped by the spreadsheet on display
# and ignored by downstream CSV readers.
CSV_INJECTION_PREFIXES = ('=', '+', '-', '@', '\t', '\r')


def chunks(items: list[Any], chunk_size: int) -> Generator[list[Any], None, None]:
    """Yield chunks from list."""
    for i in range(0, len(items), chunk_size):
        yield items[i : i + chunk_size]


def sanitize_csv_cell(value: Any) -> Any:
    """Neutralise CSV-injection prefixes on string cells."""
    if isinstance(value, str) and value.startswith(CSV_INJECTION_PREFIXES):
        return "'" + value
    return value


def empty_str_to_none(value: str | None) -> str | None:
    """Parse empty strings as None."""
    return value or None


def parse_str_to_bool(value: str | bool | None) -> bool | None:
    """Parse boolean value."""
    if value is None or value == '':
        return None
    if isinstance(value, str):
        if value.upper() == 'TRUE':
            return True
        elif value.upper() == 'FALSE':
            return False
    elif isinstance(value, bool):
        return value
    raise ValueError('Invalid boolean string')


def parse_date(value: Optional[str | date]) -> Optional[date]:
    """Validate string as date in format %m/%d/%Y"""
    if not value:
        return None
    if isinstance(value, date):
        return value
    return parse(value).date()