from sympy import *
from convert_formula import *

def differential(function, point):
    """
    计算函数在指定点的导数
    :param function: 函数表达式
    :param point: 自变量的取值点
    :return: 导数值
    """
    # 转换函数表达式为SymPy表达式
    independent_variable, function = split_function(function)
    function = sympify(convert_formula(function))
    independent_variable=symbols(independent_variable)
    derivative = diff(function, independent_variable)
    derivative_value = derivative.subs(independent_variable, point)
    return derivative_value

def differential_function(function):
    """
    计算函数的导数
    :param function: 函数表达式
    :return: 导函数
    """
    # 转换函数表达式为SymPy表达式
    independent_variable, function = split_function(function)
    function = sympify(convert_formula(function))
    independent_variable=symbols(independent_variable)
    derivative = diff(function, independent_variable)
    return str(derivative)

def integration(function):
    """
    计算函数的积分
    :param function: 函数表达式
    :return: 积分公式
    """
    # 转换函数表达式为SymPy表达式
    independent_variable, function = split_function(function)
    function = sympify(convert_formula(function))
    independent_variable=symbols(independent_variable)
    integral = integrate(function, independent_variable)
    return str(integral)+'+C'

def test_differential():
    """
    测试微分函数
    """
    function = 'f(x)=x^2'
    point = 2
    assert differential(function, point) == 4
    assert differential_function(function) == '2*x'
    assert integration(function) == 'x**3/3+C'

def UI():
    """
    用户交互界面
    """
    while True:
        print('请选择功能 1. 微分 2. 积分 3. 返回')
        choice = input('请输入您的选择：')
        if choice == '1':
            function = input('请输入函数表达式：（注：只支持形如f(x)=的表达式，不支持y=的表达式）')
            point = input('请输入自变量的取值点，求导函数请留空：')
            if point == '':
                print('导函数为：', differential_function(function))
            elif 'pi' in point:
                print('导数值为：', differential(function, point))
            else:
                print('导数值为：', differential(function, float(point)))
        elif choice == '2':
            function = input('请输入函数表达式：（注：只支持形如f(x)=的表达式，不支持y=的表达式）')
            print('积分公式为：', integration(function))
        elif choice == '3':
            print('谢谢使用')
            break
        else:
            print('输入错误，请重新输入')

if __name__ == '__main__':
    test_differential()
    UI()