"""Safe coercion of JSON-transported values into typed OPC write values.

Fixes 1879 BUG-1 (bool('false') is True in Python) and BUG-2 (uncaught
TypeError/ValueError from int/float on bad input).
"""

_FALSE_STRINGS = {'false', '0', 'no', 'off', ''}


class ConversionError(ValueError):
    """Raised when a raw value cannot be coerced to the requested type."""


def _to_bool(raw) -> bool:
    if isinstance(raw, bool):
        return raw
    if isinstance(raw, (int, float)):
        return bool(raw)
    return str(raw).strip().lower() not in _FALSE_STRINGS


def to_typed_value(raw, data_type: str):
    """Coerce raw (often a JSON string) to the given data_type.

    data_type: 'boolean' | 'int' | 'float' | 'double' | 'string'.
    Raises ConversionError on any invalid input (never a bare TypeError).
    """
    if not isinstance(data_type, str):
        raise ConversionError(f'data_type must be a string, got {type(data_type).__name__}')
    dtype = data_type.strip().lower()
    try:
        if dtype in ('bool', 'boolean'):
            return _to_bool(raw)
        if dtype in ('int', 'integer'):
            if isinstance(raw, str) and ('.' in raw or raw.strip() == ''):
                raise ConversionError(f'invalid int: {raw!r}')
            return int(raw)
        if dtype in ('float', 'double', 'real'):
            return float(raw)
        if dtype in ('str', 'string'):
            return str(raw)
    except (TypeError, ValueError) as e:
        raise ConversionError(f'cannot convert {raw!r} to {data_type}: {e}') from e
    raise ConversionError(f'unknown data_type: {data_type!r}')