Check if user is banned, log them out and then flash them with a funny message which is handled by error modals

main.py

@@ -1,4 +1,4 @@
-from flask import Flask, redirect, url_for, render_template, request, Response, send_from_directory, g
+from flask import Flask, redirect, url_for, render_template, request, Response, send_from_directory, g, flash
 from dotenv import load_dotenv
 from constants import RICKROLL_LINK, UPLOAD_DIR, MINIMUM_COSINE_SIMILARITY, MINIMUM_OCR_SIMILARITY, DATABASE_FILE
 from PIL import Image
@@ -82,6 +82,20 @@ def user_loader(user_id):
 def unauthorized_handler():
     return redirect(url_for("login"))
 
+@app.before_request
+def check_banned():
+    username = flask_login.current_user.id
+    
+    cur = get_db().cursor()
+    cur.execute("SELECT banned FROM Users WHERE username = ?", (username))
+    row = cur.fetchone()
+    cur.close()
+
+    if row is None or row[0]:
+        flash("Imagine forgetting to touch grass so you get banned from my app. Such a discord moderator you are. You have no life. Just go outside.")
+        flask_login.logout_user()
+        return redirect("/")
+
 def resize_image_file(path, max_side=256, fmt="JPEG"):
     img = Image.open(path)
     scale = max_side / max(img.size)