from bisect import insort
from heapq import merge
from collections import namedtuple

class Library(object):
    def __init__(self):
        self._users = set()
        self._bookrecords = []

    BookRecord = namedtuple("BookRecord", "name reservations") #reservations ordered by from_
    Reservation = namedtuple("Reservation", "from_ to")

    def add_user(self, name):
        if name in self._users:
            return False
        self._users.add(name)
        return True

    def add_book(self, name):
        self._bookrecords.append(Library.BookRecord(name, []))

    def reserve_book(self, user, book, date_from, date_to):
        if user not in self._users or date_from > date_to:
            return False
        disjoint_range = lambda rng: rng.to < date_from or date_to < rng.from_
        is_free = lambda record: all((disjoint_range(range_) for range_ in record.reservations))
        same_name = lambda record: record.name == book
        #it is important that we encounter the records always in the same order
        #this guarantees that reservations will not be fragmented
        for record in filter(is_free, filter(same_name, self._bookrecords)): 
            insort(record.reservations, Library.Reservation(date_from, date_to))
            return True
        return False

    def books(self):
        return (x.name for x in self._bookrecords)

    def reservations(self):
        triple_gen = lambda record: ((x.from_, x.to, record.name) for x in record.reservations)
        return merge(*[triple_gen(record) for record in self._bookrecords], key=lambda x: x[0])


def at_most_books(max_number_of_books):
    def decorator(cls):
        class NewBookCollection(cls): # pylint: disable=too-few-public-methods
            def add_book(self, name):
                #pouzitie _bookrecords je nebezpecne
                if sum([x.name == name for x in self._bookrecords]) >= max_number_of_books:
                    return False
                cls.add_book(self, name)
                return True
        return NewBookCollection
    return decorator

def one_book(bookcollection):
    return at_most_books(1)(bookcollection)