Implemented postly client

postly/clients/postly_client.py

@@ -0,0 +1,144 @@
+import re
+from collections import Counter
+from typing import List
+
+from ..common.models import Post
+
+
+class PostlyClient:
+    """
+    The Postly service interface.
+
+    This allows adding and deleting users, adding, and retrieving posts
+    and getting trending topics.
+    """
+
+    def __init__(self) -> None:
+        self.userPosts = {}
+        self.post_max_length = 140
+        self.timestamp_iter = 0
+
+    @staticmethod
+    def get_topics_from_post(post: str) -> List[str]:
+        """
+        Get topics from post.
+
+        Args:
+            post: The post to extract topics from.
+        Returns:
+            A list of topics.
+        """
+        return re.findall(pattern=r"#(\w+)", string=post)
+
+    def add_user(self, user_name: str) -> None:
+        """
+        Add new user to system.
+
+        Args:
+            user_name: The name of the user to add.
+        Returns:
+            None
+        """
+        self.userPosts[user_name] = []
+
+    def add_post(self, user_name: str, post_text: str, timestamp: int) -> None:
+        """
+        Add new post to the user's post history.
+
+        Args:
+            user_name: The name of the user to add the post to.
+            post_text: The text of the post.
+            timestamp: The timestamp of the post.
+        Returns:
+            None
+        """
+        if user_name not in self.userPosts:
+            raise KeyError(f"User {user_name} not found.")
+        
+        if len(post_text) > self.post_max_length:
+            raise RuntimeError("Post is too long")
+
+        if not post_text.strip():
+            raise ValueError("Post cannot be empty.")
+        
+        if not isinstance(timestamp, int) or timestamp < 0:
+            raise ValueError("Timestamp must be a non-negative integer.")
+
+        self.timestamp_iter += 1
+        curr_topics = self.get_topics_from_post(post_text)
+
+        self.userPosts[user_name].append(Post(content=post_text, timestamp=self.timestamp_iter, topics=curr_topics))
+
+    def delete_user(self, user_name: str) -> None:
+        """
+        Delete user from system.
+
+        Args:
+            user_name: The name of the user to delete.
+        Returns:
+            None
+        """
+        if user_name not in self.userPosts:
+            raise KeyError(f"User '{user_name}' not found.")
+        
+        self.userPosts.pop(user_name, None)
+
+    def get_posts_for_user(self, user_name: str) -> List[str]:
+        """
+        Get all posts for user, sorted by timestamp in descending order.
+
+        Args:
+            user_name: The name of the user to retrieve posts for.
+        Returns:
+            A list of posts.
+        """
+        if user_name not in self.userPosts:
+            raise KeyError(f"User '{user_name} not found.")
+        
+        return [post_data.content for post_data in self.userPosts[user_name][::-1]]
+
+    def get_posts_for_topic(self, topic: str) -> List[str]:
+        """
+        Get all posts for topic.
+
+        Args:
+            topic: The topic to retrieve posts for.
+        Returns:
+            A list of posts.
+        """
+        matched_posts = []
+        for user in self.userPosts:
+            for post_data in self.userPosts[user]:
+                if topic in post_data.topics:
+                    matched_posts.append(post_data.content)
+
+        return matched_posts
+
+    def get_trending_topics(self, from_timestamp: int, to_timestamp: int) -> List[str]:
+        """
+        Get all trending topics within a time interval.
+
+        Args:
+            from_timestamp: The start of the time interval.
+            to_timestamp: The end of the time interval.
+        Returns:
+            A list of topics.
+        """
+        if not isinstance(from_timestamp, int) or from_timestamp < 0:
+            raise ValueError("from_timestamp must be a non-negative integer.")
+        
+        if not isinstance(to_timestamp, int) or to_timestamp < 0:
+            raise ValueError("to_timestamp must be a non-negative integer.")
+        
+        if from_timestamp > to_timestamp:
+            raise ValueError("from_timestamp cannot be greater than to_timestamp.")
+        
+        # construct topic histogram
+        topics_frequency = Counter()
+        for user in self.userPosts:
+            for post_data in self.userPosts[user]:
+                if from_timestamp <= post_data.timestamp <= to_timestamp:
+                    topics_frequency.update(post_data.topics)
+
+        # retriev top topics in descending order
+        return [topic for topic, _ in topics_frequency.most_common()]