# proxy_example1.py
# 以下是一個(gè)代理類實(shí)現(xiàn)只讀訪問(wèn)的示例
# 目標(biāo)：代理后只能訪問(wèn)和修改Product的公開屬性，私有屬性_current只能查看不能修改
class Product:
    def __init__(self, price, quantity):
        self.price = price
        self.quantity = quantity
        self._current = 123

# 只暴露代理類Proxy給外部使用
class Proxy:
    def __init__(self, obj):
        self._obj = obj
    def __getattr__(self, item):    # 本實(shí)例沒(méi)有找到的屬性會(huì)執(zhí)行__getattr__方法
        if item.startswith("_"):    # 約定下劃線開頭的方法不能訪問(wèn)到被代理的類，只會(huì)訪問(wèn)到代理類
            raise Exception(f"{item} not found")    # Product存在的私有屬性也不希望被外部知道
        return getattr(self._obj, item)
    def __setattr__(self, key, value):
        if key.startswith("_"):     # 約定下劃線開頭的方法不能訪問(wèn)到被代理的類，只會(huì)訪問(wèn)到代理類
            # 注：這里不能raise，這會(huì)導(dǎo)致Proxy的實(shí)例都無(wú)法創(chuàng)建（__dict__等屬性無(wú)法創(chuàng)建）
            super(Proxy, self).__setattr__(key, value)   # 避免無(wú)限循環(huán)
        else:
            setattr(self._obj, key, value)
    # 要求只能刪除非下劃線開頭的屬性
    def __delattr__(self, item):
        if item.startswith("_"):
            super(Proxy, self).__delattr__(item)    # 避免無(wú)限循環(huán)
        else:
            delattr(self._obj, item)

def test_getattr():
    p = Product(10, 1)
    pp = Proxy(p)
    print(pp.price)
    print(pp._curr)

def test_setattr():
    p = Product(10, 2)
    pp = Proxy(p)
    pp.abc = 1
    print(pp.abc, p.abc)
    pp._curr = 10000
    print(pp._curr)  # 私有屬性，設(shè)置給了代理類
    print(p._curr)  # raise an error, 被代理的類Product的屬性沒(méi)有設(shè)置成功也無(wú)法訪問(wèn)

def test_delattr():
    p = Product(10, 2)
    pp = Proxy(p)
    pp.abc = 123
    print(pp.abc, p.abc)
    # 刪除公開屬性
    del pp.abc  # 成功
    # print(pp.abc, p.abc)  # 已被刪除
    # # 刪除私有屬性
    # del pp._curr    # 會(huì)嘗試刪除Proxy的私有屬性，raise AttributeError: _curr
    # 先創(chuàng)建在刪除
    pp._def = 123   # 這個(gè)操作只會(huì)設(shè)置Proxy的實(shí)例屬性
    print(pp._def)      # 訪問(wèn)的是Proxy實(shí)例屬性，被代理的Product實(shí)例沒(méi)有創(chuàng)建_def屬性
    # del pp._def     # 刪除的是Proxy的實(shí)例屬性
    # print(pp._def)

if __name__ == '__main__':
    test_getattr()

if __name__ == '__main__':
    test_delattr()

if __name__ == '__main__':    test_delattr()

# proxy_example2.py
class Product:
    def __init__(self, price, quantity):
        self.price = price
        self.quantity = quantity
        self._current = 123
    def __len__(self):
        return 111

# 只暴露代理類Proxy給外部使用
class Proxy:
    def __init__(self, obj):
        self._obj = obj
    def __getattr__(self, item):    # 本實(shí)例沒(méi)有找到的屬性會(huì)執(zhí)行__getattr__方法
        if item.startswith("_"):    # 約定下劃線開頭的方法不能訪問(wèn)到被代理的類，只會(huì)訪問(wèn)到代理類
            raise Exception(f"{item} not found")    # Product存在的私有屬性也不希望被外部知道
        return getattr(self._obj, item)
    def __setattr__(self, key, value):
        if key.startswith("_"):     # 約定下劃線開頭的方法不能訪問(wèn)到被代理的類，只會(huì)訪問(wèn)到代理類
            # 注：這里不能raise，這會(huì)導(dǎo)致Proxy的實(shí)例都無(wú)法創(chuàng)建（__dict__等屬性無(wú)法創(chuàng)建）
            super(Proxy, self).__setattr__(key, value)   # 避免無(wú)限循環(huán)
        else:
            setattr(self._obj, key, value)
    # 要求只能刪除非下劃線開頭的屬性
    def __delattr__(self, item):
        if item.startswith("_"):
            super(Proxy, self).__delattr__(item)    # 避免無(wú)限循環(huán)
        else:
            delattr(self._obj, item)
    @property
    def __class__(self):    # 偽造類
        return self._obj.__class__
    def __len__(self):
        return len(self._obj)
	def test_instance():
	    p = Product(10, 2)
	    pp = Proxy(p)
	    print(pp.__class__)
	    print(isinstance(pp, Product))      # 如果不偽造__class__，會(huì)返回False
	def test_len():
	    p = Product(10, 2)
	    pp = Proxy(p)
	    print(len(pp))  # 如果Proxy實(shí)例不定義__len__方法，會(huì)報(bào)錯(cuò)TypeError: object of type 'Proxy' has no len()

if __name__ == '__main__':
    test_instance()

if __name__ == '__main__':
    test_len()

# logger_proxy.py
# -*- coding:utf-8 -*-
from functools import wraps

class DAL:
    @classmethod
    def dm1(cls, req, *args):
        print("dm1...", f"{req=}")
        print(1/0)      # 故意拋出異常
        return "dm1"

class BLL:
    @classmethod
    def bm1(cls, req):
        print("bm1...", f"{req=}")
        return DAL.dm1(req)

class Application:
    def __init__(self, req):
        self.req = req
        self._p = "private attr"
    def hd1(self):
        return BLL.bm1(self.req)

class LoggerProxy:
    def __init__(self, obj):
        self._obj = obj
    def __getattr__(self, item):    # LoggerProxy類實(shí)例沒(méi)獲取到的屬性會(huì)執(zhí)行這個(gè)方法
        attr = getattr(self._obj, item)
        if callable(attr):  # 獲取到了方法，則處理異常捕獲
            @wraps(attr)
            def wrapped_method(*args, **kwargs):
                # print(f"Before access to attribute/method: {item}")
                try:
                    method = attr(*args, **kwargs)
                except ZeroDivisionError:
                    # 捕獲異常然后處理...
                    raise Exception(f"{attr.__name__} received a zero division error.")
                # print(f"After attribute/method {item} returned")
                return method
            return wrapped_method
        else:   # 獲取到了屬性，直接返回
            return attr

if __name__ == '__main__':
    lp = LoggerProxy(Application("abc"))
    print(lp.req)
    print(lp._p)
    print(lp.hd1())