"""Perpetual Inventory helpers."""


def dict_from_collection(coll, key):
    """Return a dict indexed by unique values of a specified in a collection.

    Args:
        coll (list): list of dicts
        key (str): key

    Returns:
        _dict (dict): dict keyed by unique values from collection.
    """
    _dict = {}
    for i, d in enumerate(coll):
        curr_dict = d
        if curr_dict[key] not in _dict.keys():
            _dict[curr_dict[key]] = [curr_dict]
        else:
            _dict[curr_dict[key]].append(curr_dict)
    return _dict


def min_dict(_d, user_key):
    """Return dict where user_key matches the min value."""
    _dict = {}
    for key, value in _d.items():
        _dict[key] = dict(min(value, key=lambda x: x[user_key]))
    return _dict


def max_dict(_d, user_key):
    """Return dict where user_key matches the max value."""
    _dict = {}
    for key, value in _d.items():
        _dict[key] = dict(max(value, key=lambda x: x[user_key]))
    return _dict


def sum_key_in_collection(coll, key):
    """Return a sum for a key in a collection."""
    if not coll:
        return 0
    return sum([dict(item).get(key, 0) or 0 for item in coll])