import click
from math import sqrt
from functools import wraps
from random import randint


def retry_on_exception(attempts = 1):
    def decorator(func):
        @wraps(func)
        def wrapper(*args, **kwargs):
            for i in range(attempts):
                try:
                    result = func(*args, **kwargs)
                except Exception as e:
                    if i == attempts - 1:
                        raise e
                    else:
                        continue
                else:
                    return result
        return wrapper
    return decorator


@retry_on_exception(3)
def test_random_even():
    num = randint(1, 10)
    assert num % 2 == 0


class EquationSolver:
    @staticmethod
    def solve_square(a, b, c):
        D = b ** 2 - 4 * a * c
        if D < 0:
            return
        elif D == 0:
            yield -b / (2 * a)
        else:
            yield (-b + sqrt(D)) / (2 * a)
            yield (-b - sqrt(D)) / (2 * a)

    @staticmethod
    def solve_linear(a, b, c, d):
        if a - c == 0:
            return
        yield (d - b) / (a - c)


def test_linear_D_zero():
    assert list(EquationSolver.solve_linear(1, 2, 2, 0)) == [2]


def test_linear_normal():
    assert list(EquationSolver.solve_linear(1, 2, 3, 4)) == [-1]


def test_linear_zero():
    assert list(EquationSolver.solve_linear(1, 2, 1, 4)) == []


def test_linear_infinite():
    assert list(EquationSolver.solve_linear(1, 2, 1, 2)) == []


def test_square_normal():
    assert list(EquationSolver.solve_square(1, 2, 1)) == [-1]
    assert list(EquationSolver.solve_square(1, 2, -3)) == [1, -3]


def test_square_complex():
    assert list(EquationSolver.solve_square(1, 2, 3)) == []


def test_square_no_B_C():
    assert list(EquationSolver.solve_square(1, 0, 0)) == [0]


def testAll():
    print("Testing linear")
    test_linear_D_zero()
    test_linear_normal()
    test_linear_zero()
    test_linear_infinite()
    print("Testing square")
    test_square_normal()
    test_square_complex()
    test_square_no_B_C()
    print("Test retry on exception")
    test_random_even()
    print("All tests passed")


"""
1. linear: читает параметры a, b, c, d из консоли и выводит результат работы solve_linear
2. square: читает параметры a, b, c из консоли и выводит результат работы solve_square
3. tests: запускает тесты
"""


@click.group()
def cli():
    pass


@cli.command()
def linear():
    a, b, c, d = map(float, input().split())
    solves = EquationSolver.solve_linear(a, b, c, d)
    try:
        first = next(solves)
        print("x = {}".format(first))
    except StopIteration:
        print("No solutions")
    else:
        for x in solves:
            print("x = {}".format(x))


@cli.command()
def square():
    a, b, c = map(float, input().split())
    solves = EquationSolver.solve_square(a, b, c)
    try:
        first = next(solves)
        print("x = {}".format(first))
    except StopIteration:
        print("No solutions")
    else:
        for x in solves:
            print("x = {}".format(x))


@cli.command()
def tests():
    print("Running tests...")
    testAll()
    print("Tests passed")


if __name__ == '__main__':
    test_random_even()
    cli()