Add proxy design pattern

Author: ma1onso

structural_patterns/proxy.py

@@ -0,0 +1,84 @@
+from dataclasses import dataclass, field
+from abc import ABC, abstractmethod
+from random import choice
+
+
+# The interface of a remote service
+class ThirdPartyYoutubeLib(ABC):
+    @abstractmethod
+    def list_videos(self):
+        pass
+
+    @abstractmethod
+    def get_video_info(self, id):
+        pass
+
+    @abstractmethod
+    def download_video(self, id):
+        pass
+
+
+class ThirdPartyYoutubeClass(ThirdPartyYoutubeLib):
+    def list_videos(self):
+        print('Getting the video list from Youtube API')
+    
+    def get_video_info(self, id):
+        print(f'Get metadata from Youtube API about a video, with id: {id}')
+    
+    def download_video(self, id):
+        print(f'Download a video file from YouTube API, with id: {id}')
+
+
+@dataclass
+class CachedYoutubeClass(ThirdPartyYoutubeLib):
+    service: ThirdPartyYoutubeLib
+    # Reference: https://stackoverflow.com/questions/53632152/why-cant-dataclasses-have-mutable-defaults-in-their-class-attributes-declaratio
+    list_cache: list = field(default_factory=list)
+    video_cache: str = None
+    need_reset: bool = False
+
+    def list_videos(self):
+        if self.list_cache == [] or self.need_reset:
+            self.list_cache = self.service.list_videos()
+        
+        return self.list_cache
+
+    def get_video_info(self, id):
+        if self.video_cache == None or self.need_reset:
+            self.video_cache = self.service.get_video_info(id)
+        
+        return self.video_cache
+    
+    def download_video(self, id):
+        if not self.downdload_exists(id) or self.need_reset:
+            self.service.download_video(id)
+
+    def _download_exists(self):
+        return choice(True, False)
+
+
+@dataclass
+class YoutubeManager:
+    service: ThirdPartyYoutubeLib
+
+    def render_video_page(self, id):
+        info = self.service.get_video_info(id)
+
+        return info
+
+    def render_list_panel(self):
+        video_list = self.service.list_videos()
+
+        return video_list
+
+    def react_on_user_input(self, id):
+        self.render_video_page(id)
+        self.render_list_panel()
+
+
+if __name__ == '__main__':
+    concrete_youtube_class = ThirdPartyYoutubeClass()
+    proxy_youtube_class = CachedYoutubeClass(concrete_youtube_class)
+
+    manager = YoutubeManager(proxy_youtube_class)
+    manager.react_on_user_input(id='xc343fgg')