#!/usr/bin/env python3
"""
math.py - 数学运算工具
提供乘法和除法运算功能
"""

def multiply(a: float, b: float) -> float:
    """
    计算两个数的乘积

    参数:
        a: 第一个数
        b: 第二个数

    返回:
        两个数的乘积
    """
    return a * b


def divide(a: float, b: float) -> float:
    """
    计算两个数的除法

    参数:
        a: 被除数
        b: 除数

    返回:
        除法结果

    异常:
        ValueError: 当除数为0时抛出
    """
    if b == 0:
        raise ValueError("除数不能为0")
    return a / b


def test_operations():
    """测试乘法和除法运算"""
    print("测试乘法运算:")
    print("-" * 30)

    # 测试乘法
    test_cases_multiply = [
        (2, 3, 6),
        (0, 5, 0),
        (-3, 4, -12),
        (2.5, 4, 10.0),
        (-2.5, -4, 10.0),
        (0, 0, 0),
    ]

    for a, b, expected in test_cases_multiply:
        result = multiply(a, b)
        status = "✓" if abs(result - expected) < 1e-10 else "✗"
        print(f"{a} × {b} = {result} {status} (期望: {expected})")

    print("\n测试除法运算:")
    print("-" * 30)

    # 测试除法
    test_cases_divide = [
        (6, 2, 3),
        (10, 4, 2.5),
        (-12, 3, -4),
        (0, 5, 0),
        (7.5, 2.5, 3),
        (-10, -2, 5),
    ]

    for a, b, expected in test_cases_divide:
        try:
            result = divide(a, b)
            status = "✓" if abs(result - expected) < 1e-10 else "✗"
            print(f"{a} ÷ {b} = {result} {status} (期望: {expected})")
        except ValueError as e:
            print(f"{a} ÷ {b} = 错误: {e}")

    # 测试除数为0的情况
    print("\n测试除数为0的情况:")
    print("-" * 30)
    zero_test_cases = [
        (5, 0),
        (0, 0),
        (-3, 0),
        (10.5, 0),
    ]

    for a, b in zero_test_cases:
        try:
            result = divide(a, b)
            print(f"{a} ÷ {b} = {result} ✗ (应该抛出异常)")
        except ValueError as e:
            print(f"{a} ÷ {b} = 正确抛出异常: {e}")


def interactive_mode():
    """交互式模式"""
    print("\n" + "=" * 40)
    print("交互式计算模式 (输入 'exit' 退出)")
    print("=" * 40)

    while True:
        print("\n选择操作:")
        print("1. 乘法")
        print("2. 除法")
        print("exit. 退出")

        choice = input("请选择 (1/2/exit): ").strip().lower()

        if choice == 'exit':
            print("退出交互模式。")
            break

        if choice not in ['1', '2']:
            print("无效选择，请重新输入。")
            continue

        try:
            a = float(input("请输入第一个数: "))
            b = float(input("请输入第二个数: "))

            if choice == '1':
                result = multiply(a, b)
                print(f"{a} × {b} = {result}")
            elif choice == '2':
                try:
                    result = divide(a, b)
                    print(f"{a} ÷ {b} = {result}")
                except ValueError as e:
                    print(f"错误: {e}")

        except ValueError:
            print("错误：请输入有效的数字。")


def main():
    """主函数"""
    print("数学运算工具测试")
    print("=" * 40)

    # 运行测试
    test_operations()

    # 询问是否进入交互模式
    choice = input("\n是否进入交互式计算模式? (y/n): ").strip().lower()
    if choice == 'y':
        interactive_mode()
    else:
        print("程序结束。")


if __name__ == "__main__":
    main()