"""Functions to parse the dimensions string into a dictionary that represents
those dimenions in cm
"""

import logging
from typing import Dict, Optional
import re


UNIT_CONVERSIONS = {"inches": 2.54, "feet": 30.48, "cm": 1}


def parse_dimensions_measure(dimensions: str, measure: str) -> Optional[Dict]:
    """Using a regex, parse a measurement out of a dimensions string
    I expect to find a value of the form `1.2 inches (W)` specifying the value,
    unit and measurement.
    Return a dictionary representing the parsed value and its unit.
    """
    expr = rf"(?P<value>\d*[.,]?\d*)\s+(?P<unit>[a-zA-Z]*)\s+\({measure}\)"
    if match := re.search(expr, dimensions):
        match_value = match.group("value")
        try:
            value = float(match_value)
        except ValueError:
            logging.error("could not parse value `%s` as a float for a dimension")
            return None
        return {
            "value": value,
            "unit": match.group("unit").lower(),
        }
    return None


def units_to_cm(value: float, unit: str) -> Optional[float]:
    """Convert a given dimension unit into centimeters.
    If unrecognized unit, return None"""
    try:
        conversion = UNIT_CONVERSIONS[unit]
    except KeyError:
        logging.error("unrecognized unit: %s", unit)
        return None
    return value * conversion


def parse_dimensions(dimensions: Optional[str]) -> Dict[str, Optional[float]]:
    """Parse a string representing dimensions"""
    if dimensions is None:
        return {
            "height": None,
            "width": None,
            "depth": None,
        }
    height = parse_dimensions_measure(dimensions, "H")
    width = parse_dimensions_measure(dimensions, "W")
    depth = parse_dimensions_measure(dimensions, "D")
    parsed_dimensions = {
        "height": height,
        "width": width,
        "depth": depth,
    }
    result = {}
    for key, value in parsed_dimensions.items():
        if value is None:
            result[key] = value
        else:
            result[key] = units_to_cm(**value)
    return result