"""Functions to parse the weigth string into a dictionary that represents
the weight in g
"""

import logging
from typing import Optional
import re

from helpers.misc import convert_units


UNIT_CONVERSIONS = {"pounds": 453.592, "ounces": 28.3495, "g": 1, "kg": 1000}


def parse_weight(weight: Optional[str]) -> Optional[float]:
    """Parse a weigth string into a dictionary representing the weight unit and
    value"""
    if weight is None:
        return None
    expr = r"(?P<value>\d*[.,]?\d*)\s+(?P<unit>[a-zA-Z]*)"

    # strip is needed to prevent the regex from lazily
    # matching just from the first whitespace separator,
    # this could happen because the number part in the
    # expression is technically all optional, to avoid
    # an expression too complex and unreadable
    if match := re.search(expr, weight.strip()):
        match_value = match.group("value")
        try:
            value = float(match_value)
        except ValueError:
            logging.error("could not parse value `%s` as a float for a weight")
            return None
        unit = match.group("unit").lower()
        return convert_units(value, unit, unit_conversions=UNIT_CONVERSIONS)

    return None


def dimensional_weight(
    height: Optional[float], width: Optional[float], depth: Optional[float]
) -> Optional[float]:
    """The dimensional weight (in kg) is calculated as:
    Length * Height * Width (in cm) / 5000.
    We'll return it in g here"""
    if None in [height, width, depth]:
        return None
    dimensional_weight_kg = height * width * depth / 5000
    return convert_units(
        value=dimensional_weight_kg, unit="kg", unit_conversions=UNIT_CONVERSIONS
    )