import itertools
from dictionary import Dictionary, DICTS


def make_key(dictionary_name, letters):
    return (dictionary_name, frozenset(letters))


def candidates(letters, dictionary: Dictionary, min=2):
    permutations = itertools.chain.from_iterable(
        map(lambda r: itertools.permutations(letters, r), range(min, len(letters) + 1))
    )
    return dictionary.filter(map("".join, permutations))


class CandidateCache:
    def __init__(self, maxsize=5):
        self.maxsize = maxsize
        self.cache = {}
        self.keys = []

    def get(self, dictionary_name, letters):
        key = make_key(dictionary_name, letters)
        try:
            return self.cache[key]
        except KeyError:
            data = candidates(letters, DICTS[dictionary_name])
            self.create(key, data)
            return data

    def create(self, key, data):
        if len(self.keys) > self.maxsize:
            key = self.keys.pop()
            del self.cache[key]
        self.keys.insert(0, key)
        self.cache[key] = data