"""
Урок 54. Итераторы и генераторные выражения — весь код примеров одним файлом.

Источник: subjects/python-fundamentals/course/lessons/54-iterators-generators/examples.html
Файл собран автоматически (tools/build_lesson_examples.py): правьте страницу урока.
Запуск: python lesson-54.py
"""



# ====================================================================
# Ручное управление итератором
# ====================================================================
numbers = [10, 20, 30]

iterator = iter(numbers)
print(iterator)          # <list_iterator object at ...>
print(next(iterator))    # 10
print(next(iterator))    # 20
print(next(iterator))    # 30
print(next(iterator, "end"))  # end


# ====================================================================
# Как устроен цикл for внутри
# ====================================================================
numbers = [10, 20, 30]
iterator = iter(numbers)

while True:
    try:
        num = next(iterator)
        print(num)
    except StopIteration:
        break


# ====================================================================
# Примеры из модуля itertools
# ====================================================================
import itertools

# Бесконечный счётчик
counter = itertools.count(start=1, step=10)
print(next(counter), next(counter), next(counter))  # 1 11 21

# Бесконечное повторение
cycler = itertools.cycle(["A", "B", "C"])
print(next(cycler), next(cycler), next(cycler), next(cycler))  # A B C A

# Объединение коллекций
merged = itertools.chain([1, 2, 3], [100, 200, 300])
print(list(merged))  # [1, 2, 3, 100, 200, 300]

# Декартово произведение
pairs = itertools.product([1, 2], ["A", "B"])
print(list(pairs))  # [(1, 'A'), (1, 'B'), (2, 'A'), (2, 'B')]

# Перестановки
letters = ["A", "B", "C"]
print(list(itertools.permutations(letters, 2)))
# [('A', 'B'), ('A', 'C'), ('B', 'A'), ('B', 'C'), ('C', 'A'), ('C', 'B')]


# ====================================================================
# Генераторные выражения
# ====================================================================
import sys

# Генераторное выражение
squares = (x ** 2 for x in range(5))
print(squares)        # <generator object ...>
print(list(squares))  # [0, 1, 4, 9, 16]

# Повторно использовать уже нельзя
print(list(squares))  # []


# ====================================================================
# Сравнение памяти: список vs генератор
# ====================================================================
import sys

list_comp = [x ** 2 for x in range(10 ** 6)]
gen_expr = (x ** 2 for x in range(10 ** 6))

print("List:", sys.getsizeof(list_comp), "bytes")
print("Generator:", sys.getsizeof(gen_expr), "bytes")


# ====================================================================
# Генераторы в any() и all()
# ====================================================================
words = ["apple", "Banana", "cherry", "Apricot"]

has_upper = any(word[0].isupper() for word in words)
all_long = all(len(word) > 3 for word in words)

print(has_upper)  # True
print(all_long)   # True


# ====================================================================
# Практический пример: генерация безопасных паролей
# ====================================================================
from itertools import permutations
from string import ascii_lowercase, ascii_uppercase, digits
from collections.abc import Iterator

ALL_CHARS = list(ascii_lowercase + ascii_uppercase + digits)


def is_valid(password: tuple[str, ...]) -> bool:
    """Проверяет, соответствует ли пароль всем требованиям."""
    chars = "".join(password)

    has_lower = any(ch in ascii_lowercase for ch in chars)
    has_upper = any(ch in ascii_uppercase for ch in chars)
    has_digit = any(ch in digits for ch in chars)

    if not (has_lower and has_upper and has_digit):
        return False

    for i in range(len(chars) - 1):
        if abs(ord(chars[i]) - ord(chars[i + 1])) == 1:
            return False

    return True


def generate_passwords() -> Iterator[str]:
    """Генерирует подходящие пароли длиной 4 символа."""
    all_variants = permutations(ALL_CHARS, 4)
    return ("".join(variant) for variant in all_variants if is_valid(variant))


def main() -> None:
    valid_passwords = generate_passwords()
    with open("valid_passwords.txt", "w", encoding="utf-8") as file:
        file.write("\n".join(valid_passwords))


if __name__ == "__main__":
    main()