def make_view(robot):
    """
    为一个 BaseRoBot 生成 Flask view。

    Usage ::

        from werobot import WeRoBot

        robot = WeRoBot(token='token')


        @robot.handler
        def hello(message):
            return 'Hello World!'

        from flask import Flask
        from werobot.contrib.flask import make_view

        app = Flask(__name__)
        app.add_url_rule(rule='/robot/', # WeRoBot 的绑定地址
                        endpoint='werobot', # Flask 的 endpoint
                        view_func=make_view(robot),
                        methods=['GET', 'POST'])

    :param robot: 一个 BaseRoBot 实例
    :return: 一个标准的 Flask view
    """

    def werobot_view():
        timestamp = request.args.get('timestamp', '')
        nonce = request.args.get('nonce', '')
        signature = request.args.get('signature', '')
        if not robot.check_signature(
            timestamp,
            nonce,
            signature,
        ):
            return robot.make_error_page(html.escape(request.url)), 403
        if request.method == 'GET':
            return request.args['echostr']

        message = robot.parse_message(
            request.data,
            timestamp=timestamp,
            nonce=nonce,
            msg_signature=request.args.get('msg_signature', '')
        )
        response = make_response(robot.get_encrypted_reply(message))
        response.headers['content_type'] = 'application/xml'
        return response

    return werobot_view