AI Programming 16 & 17 & 18

assistant> Of course! What would you like the application to do?

assistant> Great! That sounds like a useful task management system. Let’s break it down into smaller pieces to make it easier to implement.

Firstly, we need to define a data structure to represent the tasks. Data classes are perfect for this use case. Can you give me an idea of what fields you want to store for each task?

assistant> Here’s a data class that represents a task with the fields you mentioned:

from dataclasses import dataclass
from typing import Optional

@dataclass
class Task:
    timestamp: str
    project: str
    repository: str
    target_goal: str
    goal_progress: str
    issue_id: Optional[str] = None
    additional_notes: Optional[str] = None

This data class has fields for the timestamp, project, repository, target goal, goal progress, and an optional external issue ID and additional notes fields. The timestamp field can be a string that represents the time the task was created, or you can use the datetime module to convert it to a Python datetime object.

We will be using fire.Fire() library to create tasks and edit tasks via command line. To start with, I suggest creating a TaskManager class that has methods for creating new tasks, retrieving tasks, and updating tasks. Does that sound reasonable?

assistant> Sure, here’s the fully functional code for the task management system:

from dataclasses import dataclass
from typing import Optional
from datetime import datetime
import json
import os
from typing import List
import fire

@dataclass
class Task:
    timestamp: str
    project: str
    repository: str
    target_goal: str
    goal_progress: str
    issue_id: Optional[str] = None
    additional_notes: Optional[str] = None

class TaskManager:
    
    def __init__(self, task_file_name='./tasks.json'):
        self.task_file_name = task_file_name
        
        
    def add_task(self, project: str, repo: str, target_goal: str, goal_progress: str, issue_id: Optional[str] = None, additional_notes: Optional[str] = None):
        timestamp = datetime.now().strftime("%d-%m-%Y %H:%M:%S")
        new_task = Task(timestamp=timestamp, project=project, repository=repo, target_goal=target_goal, goal_progress=goal_progress, issue_id=issue_id, additional_notes=additional_notes)
        existing_tasks = self._get_existing_tasks()
        existing_tasks.append(new_task)
        self._save_tasks(existing_tasks)
        print(f"New task added with timestamp {timestamp}")
        
        
    def update_task(self, index: int, project: Optional[str] = None, repo: Optional[str] = None, target_goal: Optional[str] = None, goal_progress: Optional[str] = None, issue_id: Optional[str] = None, additional_notes: Optional[str] = None):
        existing_tasks = self._get_existing_tasks()
        
        try:
            existing_task = existing_tasks[index]
        except IndexError:
            print(f"No task found with index {index}")
            return
        updated_task = Task(timestamp=existing_task.timestamp, project=project or existing_task.project, repository=repo or existing_task.repository, target_goal=target_goal or existing_task.target_goal, goal_progress=goal_progress or existing_task.goal_progress,
                            issue_id=issue_id or existing_task.issue_id, additional_notes=additional_notes or existing_task.additional_notes)
        existing_tasks[index] = updated_task
        self._save_tasks(existing_tasks)
        print(f"Task with index {index} updated.")
        
        
    def delete_task(self, index: int):
        existing_tasks = self._get_existing_tasks()
        
        try:
            existing_task = existing_tasks[index]
        except IndexError:
            print(f"No task found with index {index}")
            return

        del existing_tasks[index]
        self._save_tasks(existing_tasks)
        print(f"Task {existing_task} removed.")
        
    def list_tasks(self):
        existing_tasks = self._get_existing_tasks()
        for index, task in enumerate(existing_tasks):
            print(f"[{index}] {task}")
            
    def _get_existing_tasks(self) -> List[Task]:
        if not os.path.isfile(self.task_file_name):
            with open(self.task_file_name, 'w') as f:
                json.dump([], f)
                
        with open(self.task_file_name, 'r') as f:
            # Avoiding `TypeError: list indices must be integers or slices, not str`
            # As we are loading file with [] it is list, no need to index the list :)
            data = json.load(f)        
        
        return [Task(**task) for task in data]
        
    def _save_tasks(self, tasks: List[Task]):
        with open(self.task_file_name, 'w') as f:
            json.dump([task.__dict__ for task in tasks], f, indent=4)
            
            
if __name__ == '__main__':
    fire.Fire(TaskManager)

With this code, you can create a new task by calling

python task_manager.py add_task <project> <repository> <target_goal> <goal_progress> [--issue_id] [--additional_notes]

To update an existing task, call

python task_manager.py update_task <index> [--project] [--repo] [--target_goal] [--goal_progress] [--issue_id] [--additional_notes]

To delete a task, call

python task_manager.py delete_task <index>

To list all tasks, call

python task_manager.py list_tasks

All tasks are stored in a JSON file called tasks.json in the current directory. You can change the file name or path by passing it as an argument when creating a TaskManager object.

assistant> Sure! Here’s the updated code using a SQLite database to store the tasks:

from dataclasses import dataclass
from typing import Optional
from datetime import datetime
import sqlite3
from typing import List
import fire

@dataclass
class Task:
    id: Optional[int] = None
    timestamp: str
    project: str
    repository: str
    target_goal: str
    goal_progress: str
    issue_id: Optional[str] = None
    additional_notes: Optional[str] = None

    
class TaskManager:
    
    def __init__(self, db_file_name='tasks.db'):
        self.db_file_name = db_file_name
        self._initialize_database()
        
    def _initialize_database(self):
        with sqlite3.connect(self.db_file_name) as conn:
            cursor = conn.cursor()
            cursor.execute("""CREATE TABLE IF NOT EXISTS tasks (
                                id INTEGER PRIMARY KEY,
                                timestamp TEXT NOT NULL,
                                project TEXT NOT NULL,
                                repository TEXT NOT NULL,
                                target_goal TEXT NOT NULL,
                                goal_progress TEXT NOT NULL,
                                issue_id TEXT,
                                additional_notes TEXT
                            )""")
            conn.commit()
    
    def add_task(self, project: str, repo: str, target_goal: str, goal_progress: str, issue_id: Optional[str] = None, additional_notes: Optional[str] = None):
        timestamp = datetime.now().strftime("%d-%m-%Y %H:%M:%S")
        task = Task(timestamp=timestamp, project=project, repository=repo, target_goal=target_goal, goal_progress=goal_progress, issue_id=issue_id, additional_notes=additional_notes)
        with sqlite3.connect(self.db_file_name) as conn:
            cursor = conn.cursor()
            cursor.execute("""
                INSERT INTO tasks (timestamp, project, repository, target_goal, goal_progress, issue_id, additional_notes)
                VALUES (?, ?, ?, ?, ?, ?, ?)
            """, (task.timestamp, task.project, task.repository, task.target_goal, task.goal_progress, task.issue_id, task.additional_notes))
            task_id = cursor.lastrowid
            task.id = task_id
            conn.commit()
            print(f"New task added with ID {task_id}.")
        
    def update_task(self, task_id: int, project: Optional[str] = None, repo: Optional[str] = None, target_goal: Optional[str] = None, goal_progress: Optional[str] = None, issue_id: Optional[str] = None, additional_notes: Optional[str] = None):
        with sqlite3.connect(self.db_file_name) as conn:
            cursor = conn.cursor()
            cursor.execute("""SELECT * FROM tasks WHERE id = ?""", (task_id,))
            result = cursor.fetchone()
            
            if result is None:
                print(f"No task found with ID {task_id}")
                return
                
            db_task = Task(*result)
            updated_task = Task(db_task.id, db_task.timestamp, project or db_task.project, repo or db_task.repository, target_goal or db_task.target_goal, goal_progress or db_task.goal_progress, issue_id or db_task.issue_id, additional_notes or db_task.additional_notes)
            cursor.execute("""UPDATE tasks SET timestamp=?, project=?, repository=?, target_goal=?, goal_progress=?, issue_id=?, additional_notes=? WHERE id=?""",
                            (updated_task.timestamp, updated_task.project, updated_task.repository, updated_task.target_goal, updated_task.goal_progress, updated_task.issue_id, updated_task.additional_notes, updated_task.id))
            conn.commit()
            
            print(f"Task with ID {task_id} updated.")        
        
    def delete_task(self, task_id: int):
        with sqlite3.connect(self.db_file_name) as conn:
            cursor = conn.cursor()
            cursor.execute("""SELECT * FROM tasks WHERE id = ?""", (task_id,))
            result = cursor.fetchone()
            
            if result is None:
                print(f"No task found with ID {task_id}")
                return
                
            db_task = Task(*result)
            cursor.execute("""DELETE FROM tasks WHERE id = ?""", (task_id,))
            conn.commit()
            
            print(f"Task {db_task} removed.")
        
    def list_tasks(self):
        with sqlite3.connect(self.db_file_name) as conn:
            cursor = conn.cursor()
            cursor.execute("""SELECT * FROM tasks""")
            results = cursor.fetchall()
            if not results:
                print("No tasks found.")
            else:
                for task in results:
                    print(Task(*task))
                        
if __name__ == '__main__':
    fire.Fire(TaskManager)

With this code, you can create a new task by calling

python task_manager.py add_task <project> <repository> <target_goal> <goal_progress> [--issue_id] [--additional_notes]

To update an existing task, call

python task_manager.py update_task <task_id> [--project] [--repo] [--target_goal] [--goal_progress] [--issue_id] [--additional_notes]

To delete a task, call

python task_manager.py delete_task <task_id>

To list all tasks, call

python task_manager.py list_tasks

All tasks are stored in a SQLite database file called tasks.db in the current directory. You can change the file name or path by passing it as an argument when creating a TaskManager object.

assistant> Sure, I can help you with that! What kind of browser sessions do you want to share? And do you have any specific requirements in mind for the applications you want to create?

assistant> Great! Here’s an outline of how you could approach building these two components:

1. Firefox extension:
   1. Create a new Firefox extension with a background script and a content_scripts script. These scripts will communicate with each other to capture and send URL data to the websocket service.
   2. In the content_scripts script, use the window.location API to capture the URL of every page the user visits. You could use a setInterval() function to poll for URL changes every few seconds.
   3. Send the captured URL to the background script using the browser.runtime.sendMessage() function. Include a message type to identify that this message is a URL update.
   4. In the background script, use the browser.runtime.onMessage function to listen for incoming messages from the content_scripts script. When a message is received, send the URL data to the websocket service using the WebSocket() API.
   5. To enable remote browsing sessions, allow the user to enter the WebSocket URL of another user’s websocket service. When the user connects to this URL, send a WebSocket message that subscribes the current browser session to the remote browser session. Whenever the remote browser navigates to a new URL, send that URL data to the current browser session using the WebSocket() API.
2. Python websocket receiver:
   1. Install the websockets package using pip to use WebSockets in Python.
   2. Set up a WebSocket server using the websockets package. Use a async with websockets.serve() function to listen for incoming WebSocket connections on a specified IP address and port.
   3. In the server’s async def websocket_handler() function, receive incoming WebSocket messages from connected Firefox extensions. Use these messages to update a shared navigation history or broadcast navigation updates to other subscribed Firefox extensions.
   4. To handle multiple subscribed Firefox extensions, use a dictionary or list to keep track of connected clients and their WebSocket connections.

I hope this helps! Let me know if you have any questions or need further assistance.

assistant> Sure! Let’s start with the Firefox extension first. Here are the steps to create the extension:

1. Create a new directory for the extension called “url-tracker”.
2. In this directory, create a file called “manifest.json” with the following contents:

{
  "manifest_version": 2,
  "name": "URL Tracker",
  "version": "1.0",
  "background": {
    "scripts": ["background.js"]
  },
  "content_scripts": [
    {
      "matches": ["<all_urls>"],
      "js": ["content.js"]
    }
  ],
  "permissions": [
    "webRequest",
    "webRequestBlocking",
    "tabs",
    "notifications",
    "storage",
    "activeTab",
    "http://*/",
    "https://*/",
    "tcpSocket",
    "webSocket",
    "<all_urls>"
  ]
}

3. In the “url-tracker” directory, create a file called “background.js” with the following contents:

let socket;

// Connect to websocket server
function connectWebSocket(url) {
  socket = new WebSocket(url);

  socket.onopen = function(event) {
    console.log("websocket connection opened");
  };

  socket.onmessage = function(event) {
    console.log("received websocket message:", event.data);
  };

  socket.onerror = function(event) {
    console.error("websocket error:", event);
  };

  socket.onclose = function(event) {
    console.log("websocket connection closed:", event.code, event.reason);
  };
}

// Disconnect from websocket server
function disconnectWebSocket() {
  if (socket && socket.readyState !== WebSocket.CLOSED) {
    socket.close();
  }
}

// Subscribe to a remote session
function subscribeWebSocket(url) {
  if (socket && socket.readyState === WebSocket.OPEN) {
    const message = {
      type: "subscribe",
      url: url
    };
    socket.send(JSON.stringify(message));
  }
}

// Listen for messages from content script and send to websocket server
browser.runtime.onMessage.addListener(function(message, sender, sendResponse) {
  if (message.type === "url-update") {
    const data = {
      type: "navigation",
      url: message.url,
      tabId: sender.tab.id,
      windowId: sender.tab.windowId
    };
    socket.send(JSON.stringify(data));
  }
});

4. In the “url-tracker” directory, create a file called “content.js” with the following contents:

let lastUrl = null;

// Send message to background script with current URL
function updateUrl() {
  const currentUrl = window.location.href;

  if (currentUrl !== lastUrl) {
    lastUrl = currentUrl;
    const message = {
      type: "url-update",
      url: currentUrl
    };
    browser.runtime.sendMessage(message);
  }
}

// Update URL every 3 seconds
setInterval(updateUrl, 3000);

5. Zip the “url-tracker” directory into a file called “url-tracker.zip”.
6. Install the extension by going to the “about:debugging” page in Firefox, clicking “This Firefox” on the left sidebar, clicking “Load Temporary Add-on”, and selecting the “url-tracker.zip” file.

Now the extension is installed and will send URL information to a WebSocket server. You still need to create the Python WebSocket server to receive this information. Here’s how to do it:

1. Install the websockets package using pip:

pip install websockets

2. In a new directory called “websocket-server”, create a file called “server.py” with the following contents:

import asyncio
import json
import websockets

clients = {}

async def register(websocket, path):
    clients[websocket] = {"subscriptions": []}
    try:
        async for message in websocket:
            data = json.loads(message)
            if data["type"] == "subscribe":
                url = data["url"]
                for client, info in clients.items():
                    if url in info["subscriptions"]:
                        client.send(json.dumps({"type": "duplicate"}))
                    elif client == websocket:
                        info["subscriptions"].append(url)
                        client.send(json.dumps({"type": "subscribed"}))
                    else:
                        client.send(json.dumps({
                            "type": "subscription",
                            "url": url
                        }))
            elif data["type"] == "navigation":
                for client, info in clients.items():
                    if (data["tabId"], data["windowId"]) in info["subscriptions"]:
                        client.send(message)
    except websockets.exceptions.ConnectionClosed:
        pass
    finally:
        del clients[websocket]

async def main():
    async with websockets.serve(register, "localhost", 8765):
        await asyncio.Future()  # run forever

if __name__ == "__main__":
    asyncio.run(main())

3. Start the WebSocket server by running “python server.py” in the “websocket-server” directory.

Now the WebSocket server is running and ready to receive data from the Firefox extension. Let me know if you have any questions or run into any issues!

assistant> Certainly! Here are some steps to add a login feature to the system:

1. Modify the manifest.json file to include a content_security_policy property that allows the extension to make cross-origin requests to a login API:

{
  "manifest_version": 2,
  "name": "URL Tracker",
  "version": "1.0",
  "background": {
    "scripts": ["background.js"]
  },
  "content_scripts": [
    {
      "matches": ["<all_urls>"],
      "js": ["content.js"]
    }
  ],
  "permissions": [
    "webRequest",
    "webRequestBlocking",
    "tabs",
    "notifications",
    "storage",
    "activeTab",
    "http://*/",
    "https://*/",
    "tcpSocket",
    "webSocket",
    "<all_urls>",
    "identity"
  ],
  "oauth2": {
    "client_id": "your-client-id-here",
    "scopes": ["openid", "email"],
    "authorization_endpoint": "https://your-auth-server.com/auth",
    "token_endpoint": "https://your-auth-server.com/token"
  },
  "content_security_policy": "script-src 'self' 'unsafe-eval' https://your-auth-server.com; connect-src 'self' ws://localhost:8765 https://your-ws-server.com"
}

2. In the background.js file, add a function to handle user authentication using the identity API:

async function authenticate() {
  try {
    const userinfo = await browser.identity.getProfileUserInfo();
    return { loggedin: true, email: userinfo.email };
  } catch (error) {
    return { loggedin: false };
  }
}

3. Modify the connectWebSocket function to authenticate the user before connecting to the WebSocket server:

async function connectWebSocket(url) {
  const userinfo = await authenticate();
  if (userinfo.loggedin) {
    socket = new WebSocket(url);

    socket.onopen = function(event) {
      console.log("websocket connection opened");
      const message = {
        type: "login",
        email: userinfo.email
      };
      socket.send(JSON.stringify(message));
    };

    socket.onmessage = function(event) {
      console.log("received websocket message:", event.data);
    };

    socket.onerror = function(event) {
      console.error("websocket error:", event);
    };

    socket.onclose = function(event) {
      console.log("websocket connection closed:", event.code, event.reason);
    };
  } else {
    console.error("user not logged in");
  }
}

4. Modify the subscribeWebSocket function to check if the user is logged in before sending the subscription message:

async function subscribeWebSocket(url) {
  const userinfo = await authenticate();
  if (userinfo.loggedin) {
    if (socket && socket.readyState === WebSocket.OPEN) {
      const message = {
        type: "subscribe",
        url: url
      };
      socket.send(JSON.stringify(message));
    }
  } else {
    console.error("user not logged in");
  }
}

5. In the server.py file, modify the register function to handle user authentication and limit access to certain API calls:

async def register(websocket, path):
    try:
        async for message in websocket:
            data = json.loads(message)
            if "email" in data:
                email = data["email"]
                if email in users:
                    clients[websocket] = {"subscriptions": []}
                    clients[websocket]["user"] = email
                    websocket.send(json.dumps({"type": "loggedin"}))
                else:
                    websocket.send(json.dumps({"type": "invalid"}))
            elif "type" in data and data["type"] == "subscribe" and \
                    "url" in data and "user" in clients[websocket]:
                if data["user"] in users:
                    for client, info in clients.items():
                        if data["url"] in info["subscriptions"]:
                            client.send(json.dumps({"type": "duplicate"}))
                        elif client == websocket:
                            user_info = users[data["user"]]
                            if data["url"] in user_info["subscriptions"]:
                                info["subscriptions"].append(data["url"])
                                client.send(json.dumps({"type": "subscribed"}))
                            else:
                                client.send(json.dumps({"type": "unauthorized"}))
                        else:
                            client.send(json.dumps({
                                "type": "subscription",
                                "url": data["url"],
                                "user": data["user"]
                            }))
                else:
                    websocket.send(json.dumps({"type": "invalid"}))
            elif "type" in data and data["type"] == "navigation":
                if "user" in clients[websocket]:
                    email = clients[websocket]["user"]
                    if email in users and "tabId" in data and "windowId" in data:
                        subscriptions = users[email]["subscriptions"]
                        if (data["tabId"], data["windowId"]) in subscriptions:
                            for client, _ in clients.items():
                                client.send(message)
                else:
                    websocket.send(json.dumps({"type": "unauthorized"}))
    except websockets.exceptions.ConnectionClosed:
        pass
    finally:
        del clients[websocket]

6. Modify the main function to load the list of authorized users:

with open("users.json") as f:
    users = json.load(f)

7. Create a file called users.json with a list of authorized users and their subscriptions:

{
  "user1@example.com": {
    "subscriptions": [
      "https://www.example.com"
    ]
  },
  "user2@example.com": {
    "subscriptions": [
      "https://www.example.com",
      "https://www.yahoo.com"
    ]
  }
}

With these changes, the extension will authenticate the user before connecting to the WebSocket server and subscribing to another user’s navigation session. The server.py script will ensure that only authorized users can subscribe to another user’s session. Note that this is just an example login/authentication system, and you may need to modify it to fit your specific requirements.

assistant> Of course! What kind of application do you have in mind?

assistant> Sure! Just to clarify, you want me to help you create a web application using the Python Dash framework that has similar functionality to Reddit, including user accounts, creating posts, and upvoting/downvoting posts, with the added feature of creating nested reply threads on posts, correct? Also, do you have any specific database or authentication requirements?

assistant> Got it! Here is one possible way to structure such an application using the Python Dash framework:

bootstrap.py

import psycopg2
from psycopg2.extensions import ISOLATION_LEVEL_AUTOCOMMIT

# Create the database if it doesn't exist
dbname = "reddit_clone"
conn = psycopg2.connect(database="postgres")
conn.set_isolation_level(ISOLATION_LEVEL_AUTOCOMMIT)
cur = conn.cursor()
cur.execute(f"CREATE DATABASE {dbname}")
cur.close()
conn.close()

# Connect to the newly created database
conn = psycopg2.connect(database=dbname)

# Create the user table
cur = conn.cursor()
cur.execute("""
    CREATE TABLE users (
        id SERIAL PRIMARY KEY,
        email VARCHAR(255) UNIQUE,
        password VARCHAR(255)
    )
""")
cur.close()

# Create the post table
cur = conn.cursor()
cur.execute("""
    CREATE TABLE posts (
        id SERIAL PRIMARY KEY,
        author_id INTEGER REFERENCES users(id),
        title VARCHAR(255),
        text TEXT,
        upvotes INTEGER DEFAULT 0,
        downvotes INTEGER DEFAULT 0,
        parent_post_id INTEGER REFERENCES posts(id),
        timestamp TIMESTAMP DEFAULT NOW()
    )
""")
cur.close()

# Create the comment table
cur = conn.cursor()
cur.execute("""
    CREATE TABLE comments (
        id SERIAL PRIMARY KEY,
        author_id INTEGER REFERENCES users(id),
        text TEXT,
        upvotes INTEGER DEFAULT 0,
        downvotes INTEGER DEFAULT 0,
        parent_post_id INTEGER REFERENCES posts(id),
        parent_comment_id INTEGER REFERENCES comments(id),
        timestamp TIMESTAMP DEFAULT NOW()
    )
""")
cur.close()

conn.commit()
conn.close()

app.py

import psycopg2
import dash
import dash_core_components as dcc
import dash_html_components as html
from dash.dependencies import Input, Output, State
from dataclasses import dataclass
from typing import Optional


@dataclass
class User:
    id: int
    email: str
    password: str


@dataclass
class Post:
    id: int
    author_id: int
    title: str
    text: str
    upvotes: int = 0
    downvotes: int = 0
    parent_post_id: Optional[int] = None


@dataclass
class Comment:
    id: int
    author_id: int
    text: str
    upvotes: int = 0
    downvotes: int = 0
    parent_post_id: Optional[int] = None
    parent_comment_id: Optional[int] = None


def get_db_conn():
    return psycopg2.connect(database="reddit_clone")


def get_user_by_email(email):
    conn = get_db_conn()
    cur = conn.cursor()
    cur.execute("SELECT * FROM users WHERE email = %s", (email,))
    row = cur.fetchone()
    cur.close()
    conn.close()
    if row:
        return User(*row)
    return None


def create_user(email, password):
    conn = get_db_conn()
    cur = conn.cursor()
    cur.execute(
        "INSERT INTO users (email, password) VALUES (%s, %s) RETURNING id",
        (email, password),
    )
    row = cur.fetchone()
    cur.close()
    conn.commit()
    conn.close()
    return User(row[0], email, password)


def create_post(author_id, title, text, parent_post_id=None):
    conn = get_db_conn()
    cur = conn.cursor()
    cur.execute(
        "INSERT INTO posts (author_id, title, text, parent_post_id) "
        "VALUES (%s, %s, %s, %s) "
        "RETURNING id",
        (author_id, title, text, parent_post_id),
    )
    row = cur.fetchone()
    cur.close()
    conn.commit()
    conn.close()
    return Post(row[0], author_id, title, text, parent_post_id=parent_post_id)


def create_comment(author_id, text, parent_post_id=None, parent_comment_id=None):
    conn = get_db_conn()
    cur = conn.cursor()
    cur.execute(
        "INSERT INTO comments (author_id, text, parent_post_id, parent_comment_id) "
        "VALUES (%s, %s, %s, %s) "
        "RETURNING id",
        (author_id, text, parent_post_id, parent_comment_id),
    )
    row = cur.fetchone()
    cur.close()
    conn.commit()
    conn.close()
    return Comment(
        row[0], author_id, text, parent_post_id=parent_post_id, parent_comment_id=parent_comment_id
    )


app = dash.Dash(__name__)

app.layout = html.Div(
    [
        html.H1("Reddit Clone"),
        html.Div(
            [
                html.H2("Create Post"),
                dcc.Input(id="post-title", placeholder="Title", type="text"),
                dcc.Textarea(
                    id="post-text", placeholder="Text", style={"width": "100%", "height": 100}
                ),
                html.Button("Submit", id="post-submit"),
            ],
            style={"width": "50%"},
        ),
        html.Div(
            [
                html.H2("Create Comment"),
                dcc.Input(id="comment-parent-post-id", placeholder="Parent Post ID", type="number"),
                dcc.Input(
                    id="comment-parent-comment-id",
                    placeholder="Parent Comment ID (optional)",
                    type="number",
                ),
                dcc.Textarea(
                    id="comment-text", placeholder="Text", style={"width": "100%", "height": 100}
                ),
                html.Button("Submit", id="comment-submit"),
            ],
            style={"width": "50%"},
        ),
        html.Div([], id="posts"),
    ],
    style={"padding": "20px"},
)


@app.callback(
    Output("posts", "children"),
    [Input("post-submit", "n_clicks")],
    [State("post-title", "value"), State("post-text", "value")],
)
def create_post_callback(n_clicks, title, text):
    if not n_clicks:
        return []
    user = get_user_by_email("test@example.com")  # TODO: get current user from session
    post = create_post(user.id, title, text)
    return html.Div(
        [
            html.H3(f"{post.title} ({post.upvotes - post.downvotes} points)"),
            html.Div(post.text),
            dcc.Input(
                id=f"post-{post.id}-comment-text",
                placeholder="Write a comment",
                type="text",
                style={"width": "80%"},
            ),
            html.Button(
                "Submit",
                id=f"post-{post.id}-comment-submit",
                n_clicks=0,
                style={"margin": "10px"},
            ),
            html.Ul(id=f"post-{post.id}-comments"),
        ],
        style={"margin": "10px"},
    )


@app.callback(
    Output("post-{}-comments".format("{post_id}"), "children"),
    [Input("post-{}-comment-submit".format("{post_id}"), "n_clicks")],
    [State("post-{}-comment-text".format("{post_id}"), "value")],
)
def create_post_comment_callback(n_clicks, text, post_id):
    if not n_clicks:
        return []
    user = get_user_by_email("test@example.com")  # TODO: get current user from session
    comment = create_comment(user.id, text, parent_post_id=post_id)
    return html.Li(
        [
            html.H4(f"{user.email} ({comment.upvotes - comment.downvotes} points)"),
            html.Div(comment.text),
            dcc.Input(
                id=f"comment-{comment.id}-comment-text",
                placeholder="Write a reply",
                type="text",
                style={"width": "80%"},
            ),
            html.Button(
                "Submit",
                id=f"comment-{comment.id}-comment-submit",
                n_clicks=0,
                style={"margin": "10px"},
            ),
            html.Ul(id=f"comment-{comment.id}-comments"),
        ]
    )


@app.callback(
    Output("comment-{}-comments".format("{comment_id}"), "children"),
    [Input("comment-{}-comment-submit".format("{comment_id}"), "n_clicks")],
    [State("comment-{}-comment-text".format("{comment_id}"), "value")],
)
def create_comment_comment_callback(n_clicks, text, comment_id):
    if not n_clicks:
        return []
    user = get_user_by_email("test@example.com")  # TODO: get current user from session
    comment = create_comment(user.id, text, parent_comment_id=comment_id)
    return html.Li(
        [
            html.H4(f"{user.email} ({comment.upvotes - comment.downvotes} points)"),
            html.Div(comment.text),
            dcc.Input(
                id=f"comment-{comment.id}-comment-text",
                placeholder="Write a reply",
                type="text",
                style={"width": "80%"},
            ),
            html.Button(
                "Submit",
                id=f"comment-{comment.id}-comment-submit",
                n_clicks=0,
                style={"margin": "10px"},
            ),
            html.Ul(id=f"comment-{comment.id}-comments"),
        ]
    )


if __name__ == "__main__":
    app.run_server(debug=True)

This is just a starting point and can be expanded upon as needed, but it should give you a good idea of how to set up a Reddit clone using the Python Dash framework with a PostgreSQL database backend. You can also add more authentication and session management functionality as needed using Flask-Login or other similar libraries.

assistant> Of course! Here’s the modified version of the app code that utilizes Argon2 for password hashing and raises PreventDefault when n_clicks is None. The callbacks have also been modified to eliminate the use of a dynamically formatted string:

import psycopg2
from argon2 import PasswordHasher
import dash
import dash_core_components as dcc
import dash_html_components as html
from dash.dependencies import Input, Output, State, MATCH, ALL
from dataclasses import dataclass
from typing import Optional


@dataclass
class User:
    id: int
    email: str
    password: str


@dataclass
class Post:
    id: int
    author_id: int
    title: str
    text: str
    upvotes: int = 0
    downvotes: int = 0
    parent_post_id: Optional[int] = None


@dataclass
class Comment:
    id: int
    author_id: int
    text: str
    upvotes: int = 0
    downvotes: int = 0
    parent_post_id: Optional[int] = None
    parent_comment_id: Optional[int] = None


def get_db_conn():
    return psycopg2.connect(database="reddit_clone")


def get_user_by_email(email):
    conn = get_db_conn()
    cur = conn.cursor()
    cur.execute("SELECT * FROM users WHERE email = %s", (email,))
    row = cur.fetchone()
    cur.close()
    conn.close()
    if row:
        return User(*row)
    return None


def create_user(email, password):
    conn = get_db_conn()
    cur = conn.cursor()
    password_hasher = PasswordHasher()
    password_hash = password_hasher.hash(password)
    cur.execute(
        "INSERT INTO users (email, password) VALUES (%s, %s) RETURNING id",
        (email, password_hash),
    )
    row = cur.fetchone()
    cur.close()
    conn.commit()
    conn.close()
    return User(row[0], email, password_hash)


def create_post(author_id, title, text, parent_post_id=None):
    conn = get_db_conn()
    cur = conn.cursor()
    cur.execute(
        "INSERT INTO posts (author_id, title, text, parent_post_id) "
        "VALUES (%s, %s, %s, %s) "
        "RETURNING id",
        (author_id, title, text, parent_post_id),
    )
    row = cur.fetchone()
    cur.close()
    conn.commit()
    conn.close()
    return Post(row[0], author_id, title, text, parent_post_id=parent_post_id)


def create_comment(author_id, text, parent_post_id=None, parent_comment_id=None):
    conn = get_db_conn()
    cur = conn.cursor()
    cur.execute(
        "INSERT INTO comments (author_id, text, parent_post_id, parent_comment_id) "
        "VALUES (%s, %s, %s, %s) "
        "RETURNING id",
        (author_id, text, parent_post_id, parent_comment_id),
    )
    row = cur.fetchone()
    cur.close()
    conn.commit()
    conn.close()
    return Comment(
        row[0], author_id, text, parent_post_id=parent_post_id, parent_comment_id=parent_comment_id
    )


app = dash.Dash(__name__)

app.layout = html.Div(
    [
        html.H1("Reddit Clone"),
        html.Div(
            [
                html.H2("Create Post"),
                dcc.Input(id="post-title", placeholder="Title", type="text"),
                dcc.Textarea(
                    id="post-text", placeholder="Text", style={"width": "100%", "height": 100}
                ),
                html.Button("Submit", id="post-submit"),
            ],
            style={"width": "50%"},
        ),
        html.Div(
            [
                html.H2("Create Comment"),
                dcc.Input(id="comment-parent-post-id", placeholder="Parent Post ID", type="number"),
                dcc.Input(
                    id="comment-parent-comment-id",
                    placeholder="Parent Comment ID (optional)",
                    type="number",
                ),
                dcc.Textarea(
                    id="comment-text", placeholder="Text", style={"width": "100%", "height": 100}
                ),
                html.Button("Submit", id="comment-submit"),
            ],
            style={"width": "50%"},
        ),
        html.Div([], id="posts"),
    ],
    style={"padding": "20px"},
)


@app.callback(
    Output("posts", "children"),
    [Input("post-submit", "n_clicks")],
    state={
        "title": State("post-title", "value"),
        "text": State("post-text", "value"),
    },
)
def create_post_callback(n_clicks, title, text):
    if n_clicks is None:
        raise PreventDefault
    user = get_user_by_email("test@example.com")  # TODO: get current user from session
    post = create_post(user.id, title, text)
    return html.Div(
        [
            html.H3(f"{post.title} ({post.upvotes - post.downvotes} points)"),
            html.Div(post.text),
            dcc.Input(
                id={"type": "post-comment-text", "index": post.id},
                placeholder="Write a comment",
                type="text",
                style={"width": "80%"},
            ),
            html.Button(
                "Submit",
                id={"type": "post-comment-submit", "index": post.id},
                n_clicks=0,
                style={"margin": "10px"},
            ),
            html.Ul(id=f"post-{post.id}-comments"),
        ],
        style={"margin": "10px"},
    )


@app.callback(
    Output({"type": "post-comment-submit-feedback", "index": MATCH["index"]}, "children"),
    [Input({"type": "post-comment-submit", "index": MATCH["index"]}, "n_clicks")],
    state={
        "text": State({"type": "post-comment-text", "index": MATCH["index"]}, "value"),
        "post_id": MATCH["index"],
    },
)
def create_post_comment_callback(n_clicks, text, post_id):
    if n_clicks is None:
        raise PreventDefault
    user = get_user_by_email("test@example.com")  # TODO: get current user from session
    comment = create_comment(user.id, text, parent_post_id=post_id)
    return html.Li(
        [
            html.H4(f"{user.email} ({comment.upvotes - comment.downvotes} points)"),
            html.Div(comment.text),
            dcc.Input(
                id={"type": "comment-comment-text", "index": comment.id},
                placeholder="Write a reply",
                type="text",
                style={"width": "80%"},
            ),
            html.Button(
                "Submit",
                id={"type": "comment-comment-submit", "index": comment.id},
                n_clicks=0,
                style={"margin": "10px"},
            ),
            html.Ul(id=f"comment-{comment.id}-comments"),
        ]
    )


@app.callback(
    Output({"type": "comment-comment-submit-feedback", "index": MATCH["index"]}, "children"),
    [Input({"type": "comment-comment-submit", "index": MATCH["index"]}, "n_clicks")],
    state={
        "text": State({"type": "comment-comment-text", "index": MATCH["index"]}, "value"),
        "comment_id": MATCH["index"],
    },
)
def create_comment_comment_callback(n_clicks, text, comment_id):
    if n_clicks is None:
        raise PreventDefault
    user = get_user_by_email("test@example.com")  # TODO: get current user from session
    comment = create_comment(user.id, text, parent_comment_id=comment_id)
    return html.Li(
        [
            html.H4(f"{user.email} ({comment.upvotes - comment.downvotes} points)"),
            html.Div(comment.text),
            dcc.Input(
                id={"type": "comment-comment-text", "index": comment.id},
                placeholder="Write a reply",
                type="text",
                style={"width": "80%"},
            ),
            html.Button(
                "Submit",
                id={"type": "comment-comment-submit", "index": comment.id},
                n_clicks=0,
                style={"margin": "10px

assistant> Of course! What kind of application would you like to create?

assistant> Wow, that’s a pretty complex application! I’ll do my best to help you out. Let’s break down the requirements and start with creating the necessary schemas in the bootstrap.py file.

First, we’ll need a User schema for user accounts:

from dataclasses import dataclass
from typing import Optional

@dataclass
class User:
    id: Optional[int] = None
    email: str
    password: str

We’ll also need a schema for Post:

from dataclasses import dataclass
from typing import Optional

@dataclass
class Post:
    id: Optional[int] = None
    author_id: int
    title: str
    body: str
    created_at: Optional[datetime] = None

Next, we’ll need a schema for Reply:

from dataclasses import dataclass
from typing import Optional

@dataclass
class Reply:
    id: Optional[int] = None
    author_id: int
    post_id: int
    parent_id: Optional[int] = None
    body: str
    created_at: Optional[datetime] = None

Now that we have our schemas, we can start setting up our database interactions using async sqlalchemy. We’ll create a class called Database that will manage our database operations:

from sqlalchemy.ext.asyncio import create_async_engine, AsyncSession
from sqlalchemy.orm import sessionmaker, selectinload
from sqlalchemy import select, func
from .schemas import User, Post, Reply

class Database:
    def __init__(self, db_url: str):
        self.engine = create_async_engine(db_url)
        self.async_session = sessionmaker(
            bind=self.engine, class_=AsyncSession, expire_on_commit=False
        )

    async def create_user(self, email: str, password: str) -> User:
        async with self.async_session() as session:
            user = User(email=email, password=password)
            session.add(user)
            await session.commit()
            await session.refresh(user)
            return user

    async def get_user_by_email(self, email: str) -> Optional[User]:
        async with self.async_session() as session:
            stmt = select(User).where(User.email == email)
            result = await session.execute(stmt)
            row = result.scalars().first()
            return row

    async def get_user_by_id(self, id: int) -> Optional[User]:
        async with self.async_session() as session:
            stmt = select(User).where(User.id == id)
            result = await session.execute(stmt)
            row = result.scalars().first()
            return row

    async def create_post(self, author_id: int, title: str, body: str) -> Post:
        async with self.async_session() as session:
            post = Post(author_id=author_id, title=title, body=body)
            session.add(post)
            await session.commit()
            await session.refresh(post)
            return post

    async def get_post_by_id(self, id: int) -> Optional[Post]:
        async with self.async_session() as session:
            stmt = select(Post).where(Post.id == id)
            result = await session.execute(stmt)
            row = result.scalars().first()
            return row

    async def get_posts_by_author_id(
        self, author_id: int, limit: Optional[int] = None, offset: int = 0
    ) -> List[Post]:
        async with self.async_session() as session:
            stmt = (
                select(Post)
                .where(Post.author_id == author_id)
                .offset(offset)
                .order_by(Post.created_at.desc())
            )
            if limit is not None:
                stmt = stmt.limit(limit)
            result = await session.execute(stmt)
            rows = result.scalars().all()
            return rows

    async def create_reply(
        self, author_id: int, post_id: int, body: str, parent_id: Optional[int] = None
    ) -> Reply:
        async with self.async_session() as session:
            reply = Reply(
                author_id=author_id, post_id=post_id, body=body, parent_id=parent_id
            )
            session.add(reply)
            await session.commit()
            await session.refresh(reply)
            return reply

    async def get_reply_by_id(self, id: int) -> Optional[Reply]:
        async with self.async_session() as session:
            stmt = select(Reply).where(Reply.id == id)
            result = await session.execute(stmt)
            row = result.scalars().first()
            return row

    async def get_replies_by_post_id(
        self, post_id: int, limit: Optional[int] = None, offset: int = 0
    ) -> List[Reply]:
        async with self.async_session() as session:
            stmt = (
                select(Reply)
                .where(Reply.post_id == post_id)
                .offset(offset)
                .order_by(Reply.created_at.asc())
            )
            if limit is not None:
                stmt = stmt.limit(limit)
            result = await session.execute(stmt)
            rows = result.scalars().all()
            return rows

    async def get_reply_count_by_post_id(self, post_id: int) -> int:
        async with self.async_session() as session:
            stmt = select(func.count(Reply.id)).where(Reply.post_id == post_id)
            result = await session.execute(stmt)
            row = result.scalar()
            return row

With our database operations set up, we can move on to our authentication system. We’ll use argon2 to hash passwords and store them in the database. Here’s the code for our auth.py module:

import argon2
from .database import Database
from .schemas import User
from typing import Optional

class AuthService:
    def __init__(self, db: Database):
        self.db = db
        self.hasher = argon2.PasswordHasher()

    async def create_user(self, email: str, password: str) -> User:
        hashed_password = self.hasher.hash(password)
        user = await self.db.create_user(email=email, password=hashed_password)
        return user

    async def authenticate_user(self, email: str, password: str) -> Optional[User]:
        user = await self.db.get_user_by_email(email)
        if user is None:
            return None
        try:
            self.hasher.verify(user.password, password)
        except argon2.exceptions.VerifyMismatchError:
            return None
        return user

Next, we’ll move on to creating our application using the Python Dash framework. We’ll start by setting up our app.py file with some basic imports and initializing the Dash object:

import os
from dotenv import load_dotenv
from typing import Tuple, Optional
from functools import wraps
from flask import request, redirect, url_for
import dash
import dash_core_components as dcc
import dash_html_components as html
import dash_bootstrap_components as dbc
from dash.dependencies import Input, Output, State, MATCH
from .database import Database
from .auth import AuthService
from .schemas import User, Post, Reply

load_dotenv()

db_url = os.getenv("DB_URL")

db = Database(db_url)
auth_service = AuthService(db)

app = dash.Dash(__name__, external_stylesheets=[dbc.themes.BOOTSTRAP])

Next, we’ll create some authentication-related routes. We’ll start with a login route:

@app.route("/login", methods=["GET", "POST"])
def login():
    if request.method == "POST":
        email = request.form["email"]
        password = request.form["password"]
        user = await auth_service.authenticate_user(email, password)
        if user is None:
            # authentication failed
            return html.Div("Invalid email or password.")
        else:
            # authentication succeeded
            session["user_id"] = user.id
            return redirect(url_for("index"))
    else:
        # show login form
        return html.Div(
            [
                html.H1("Log in"),
                dbc.Form(
                    [
                        dbc.FormGroup(
                            [
                                dbc.Label("Email", html_for="email"),
                                dbc.Input(
                                    type="email", id="email", name="email", required=True
                                ),
                            ]
                        ),
                        dbc.FormGroup(
                            [
                                dbc.Label("Password", html_for="password"),
                                dbc.PasswordInput(
                                    id="password", name="password", required=True
                                ),
                            ]
                        ),
                        dbc.Button("Log in", type="submit", color="primary"),
                    ],
                    method="POST",
                ),
                html.Div(
                    "Don't have an account? ",
                    html.A("Sign up", href="/register"),
                ),
            ],
            className="container",
        )

We’ll also create a logout route:

@app.route("/logout")
def logout():
    session.pop("user_id", None)
    return redirect(url_for("index"))

Now that we have our authentication routes set up, we can move on to building the functionality of our Reddit-like application. We’ll start with a simple route to display a list of posts:

@app.route("/")
def index():
    posts = await db.get_posts()
    return html.Div(
        [
            html.H1("Posts"),
            html.Ul(
                [
                    html.Li(
                        html.A(
                            post.title,
                            href=f"/posts/{post.id}",
                        )
                    )
                    for post in posts
                ]
            ),
            html.Div(
                html.Button("Create post", id="create-post-button"),
                className="container",
            ),
        ],
        className="container",
    )

We’ll also add some callbacks for the create-post-button button:

@app.callback(
    Output("create-post-modal", "is_open"),
    [Input("create-post-button", "n_clicks")],
    [State("create-post-modal", "is_open")],
)
def toggle_create_post_modal(n_clicks, is_open):
    if n_clicks is not None:
        return not is_open
    return is_open


@app.callback(
    Output("create-post-form-alert", "children"),
    [Input("create-post-form", "submit_n_clicks")],
    [State("create-post-form-title", "value"), State("create-post-form-body", "value")],
)
async def create_post(submit_n_clicks, title, body):
    if submit_n_clicks is not None:
        if title and body:
            user_id = session.get("user_id")
            if user_id is not None:
                post = await db.create_post(author_id=user_id, title=title, body=body)
                return dbc.Alert(
                    "Post created.", color="success", dismissable=True, duration=5000
                )
            else:
                return dbc.Alert(
                    "You must be logged in to create a post.",
                    color="warning",
                    dismissable=True,
                    duration=5000,
                )
        else:
            return dbc.Alert(
                "Please fill out all required fields.",
                color="danger",
                dismissable=True,
                duration=5000,
            )
    return None

We’ll also create a view post route:

@app.route("/posts/<int:post_id>")
def view_post(post_id: int):
    post = await db.get_post_by_id(post_id)
    replies = await db.get_replies_by_post_id(post_id)
    return html.Div(
        [
            html.H1(post.title),
            html.P(post.body),
            html.H2("Replies"),
            html.Ul(
                [
                    html.Li(
                        html.A(
                            reply.body,
                            href=f"/posts/{post_id}/replies/{reply.id}",
                        )
                    )
                    for reply in replies
                ]
            ),
            html.Form(
                [
                    dbc.FormGroup(
                        [
                            dbc.Label("Reply"),
                            dbc.Textarea(id="create-reply-form-body", required=True),
                        ]
                    ),
                    dbc.Button("Submit", type="submit"),
                ],
                id="create-reply-form",
                method="POST",
            ),
        ],
        className="container",
    )

And some callbacks for the create-reply-form:

@app.callback(
    Output("create-reply-form-alert", "children"),
    [
        Input("create-reply-form", "submit_n_clicks"),
        Input("create-reply-form-cancel-button", "n_clicks"),
    ],
    [State("create-reply-form-body", "value"), State("create-reply-form", "pathname")],
)
async def create_reply(submit_n_clicks, cancel_n_clicks, body, pathname):
    if body is None:
        return None
    if submit_n_clicks is not None:
        user_id = session.get("user_id")
        if user_id is None:
            return dbc.Alert(
                "You must be logged in to create a reply.",
                color="warning",
                dismissable=True,
                duration=5000,
            )
        post_id = int(pathname.split("/")[-2])
        parent_id = int(pathname.split("/")[-1].split("?")[0])
        reply = await db.create_reply(
            author_id=user_id, post_id=post_id, body=body, parent_id=parent_id
        )
        return dbc.Alert(
            "Reply added.",
            color="success",
            dismissable=True,
            duration=5000,
        )
    if cancel_n_clicks is not None:
        return None
    return None

Those are the basics of how to create a Reddit-like application using the Python Dash framework. Of course, this is just scratching the surface of what’s possible with Dash. But hopefully, this is enough to get you started!

assistant> Yes, I can help you write those methods. Here are some example implementations for each report:

Find the Top 10 Upvoted Posts:

async def get_top_upvoted_posts(limit: int = 10) -> List[Post]:
    async with engine.begin() as conn:
        result = await conn.execute(
            """
            SELECT posts.*, COUNT(votes.id) as vote_count
            FROM posts
            LEFT JOIN votes ON votes.post_id = posts.id AND votes.direction = 1
            GROUP BY posts.id
            ORDER BY vote_count DESC
            LIMIT :limit
            """,
            {"limit": limit},
        )
        rows = await result.fetchall()
        posts = [Post(**row._asdict()) for row in rows]
        return posts

Find the Top 10 Users with the Most Posts:

async def get_top_posting_users(limit: int = 10) -> List[Tuple[User, int]]:
    async with engine.begin() as conn:
        result = await conn.execute(
            """
            SELECT users.*, COUNT(posts.id) as post_count
            FROM users
            LEFT JOIN posts ON posts.author_id = users.id
            GROUP BY users.id
            ORDER BY post_count DESC
            LIMIT :limit
            """,
            {"limit": limit},
        )
        rows = await result.fetchall()
        users = [(User(**row._asdict()), row.post_count) for row in rows]
        return users

Find the Top 10 Users with the Most Comments:

async def get_top_commenting_users(limit: int = 10) -> List[Tuple[User, int]]:
    async with engine.begin() as conn:
        result = await conn.execute(
            """
            SELECT users.*, COUNT(comments.id) as comment_count
            FROM users
            LEFT JOIN comments ON comments.author_id = users.id
            GROUP BY users.id
            ORDER BY comment_count DESC
            LIMIT :limit
            """,
            {"limit": limit},
        )
        rows = await result.fetchall()
        users = [(User(**row._asdict()), row.comment_count) for row in rows]
        return users

Find the Top 10 Posts with the Deepest Comment Depth:

async def get_top_posts_by_comment_depth(limit: int = 10) -> List[Tuple[Post, int]]:
    async with engine.begin() as conn:
        result = await conn.execute(
            """
            WITH RECURSIVE "comments_hierarchy" AS (
                SELECT "comments".*, 1 as depth
                FROM "comments"
                WHERE "comments"."parent_id" IS NULL
                UNION ALL
                SELECT "comments".*, "comments_hierarchy"."depth" + 1
                FROM "comments"
                JOIN "comments_hierarchy" ON "comments"."parent_id" = "comments_hierarchy"."id"
            )
            SELECT "posts".*, MAX("comments_hierarchy".depth) as max_depth
            FROM "posts"
            JOIN "comments_hierarchy" ON "comments_hierarchy"."post_id" = "posts"."id"
            GROUP BY "posts"."id"
            ORDER BY max_depth DESC
            LIMIT :limit
            """,
            {"limit": limit},
        )
        rows = await result.fetchall()
        posts = [(Post(**row._asdict()), row.max_depth) for row in rows]
        return posts

assistant> Sure, here’s the updated version of the reporting methods that use SQLAlchemy instead of raw SQL queries. I’ve also reversed the order of the reports so that the top 10 posts with the deepest comment depth are first:

Find the Top 10 Posts with the Deepest Comment Depth:

from sqlalchemy import desc

async def get_top_posts_by_comment_depth(limit: int = 10) -> List[Tuple[Post, int]]:
    async with Session() as session:
        subquery = (
            session.query(
                Comment.post_id,
                func.max(
                    func.coalesce(
                        Comment.parent_id,
                        Comment.id,
                    ),
                ),
            )
            .group_by(Comment.post_id)
            .subquery()
        )

        query = (
            session.query(
                Post,
                coalesce(
                    func.max(subquery.columns[1]) - func.min(subquery.columns[1]),
                    0,
                ),