import os

def file_handler(backend_data,res=None,type='fetch'):                  # 查询功能

    if type == 'fetch':

         with open('test_new.txt','r') as  read_f:

             ret = []

             tag = False

             for read_line in  read_f:

                if read_line.strip() == backend_data:

                    tag = True

                    continue

                if tag and read_line.startswith('backend'):

                    break

                if tag:

                    print(read_line,end='')

                    ret.append(read_line)

         return ret

    if type == 'change':                                          # 修改功能

        with open('test_new.txt', 'r') as read_f, \

                open('test_new.txt_new', 'w') as write_f:

            tag = False

            has_write = False

            for read_line in read_f:

                if read_line.strip() == backend_data:

                    tag = True

                    continue

                if tag and read_line.startswith('backend'):

                    tag = False

                if not tag:

                    write_f.write(read_line)

                else:

                    if not has_write:

                        for record in res:

                            write_f.write(record)

                        has_write = True

        os.rename('test_new.txt', 'test_new.txt.bak')

        os.rename('test_new.txt_new', 'test_new.txt')

        os.remove('test_new.txt.bak')

def fetch(data):

    print('您输入的信息是：',data)

    backend_data= 'backend %s' % data

    return file_handler(backend_data)

def change(data):

    print('开始修改功能')

    print('用户输入的信息是：',data)

    backend=data[0]['backend']

    backend_data='backend %s' %backend

    old_server_record ='%s server %s %s\n'%(*9,data[0]['record']['server'])

    new_server_record = '%s server %s %s\n' % (*9, data[1]['record']['server'])

    print('您想要修改的记录：',old_server_record)

    res=fetch(backend)

    print(res)

    if not res or old_server_record not in res:

        return '您要修改的信息不存在'

    else:

        index = res.index(old_server_record)

        res[index]=new_server_record

    res.insert(0,'%s\n' %backend_data)

    file_handler(backend_data,res=res,type='change')

if __name__== '__main__':

    msg='''

    1：查询

    2：修改

    5：退出

    '''

    msg_dic={

        '':fetch,

        '':change

    }

    while True:

        print(msg)

        choose = input('请输入您要的选项：').strip()

        if not choose: continue

        if choose == '':break

        data = input('请输入您的信息：').strip()

        if choose != '':

            data = eval(data)

        res = msg_dic[choose](data)            # 查询到的结果放到一个列表里输出

        print('最终的结果：',res)