Almost finished, just have to do a quick check for everything to work, add error handling (+retries), polish it up and then make sure all features implemented fully.

main.py

@@ -6,6 +6,8 @@
 # © Uthmn 2025 under MIT license
 
 import time
+from datetime import datetime, timedelta
+from typing import Union
 
 import services.apt
 import services.mail
@@ -21,30 +23,66 @@ import typer
 
 app = typer.Typer()
 
+def wait_until(target_time):
+    now = datetime.now()
+    seconds_to_wait = (target_time - now).total_seconds()
+    if seconds_to_wait > 0:
+        time.sleep(seconds_to_wait)
+
+def schedule(mode, hour, minute=0, receiver_email=None):
+    print(f"Scheduler started at {datetime.now().strftime('%Y-%m-%d %H:%M:%S')} - Mode: {mode}")
+    while True:
+        now = datetime.now()
+        if mode == "daily":
+            target = now.replace(hour=hour, minute=minute, second=0, microsecond=0)
+            if target <= now:
+                target += timedelta(days=1)
+        elif mode == "hourly":
+            target = now.replace(minute=minute, second=0, microsecond=0)
+            if target <= now:
+                target += timedelta(hours=1)
+        else:
+            raise ValueError("Mode must be 'daily' or 'hourly'.")
+        
+        wait_until(target)
+        generate_email(receiver_email)
+
 @app.command()
-def serve(receiver_email: str = None, check_interval: int = 24):
+def serve(receiver_email: str = None, check_hourly: bool = False, check_daily: str = "18"):
     """
-    Checks for updates at a fixed interval and sends email at that interval as a daemon. Doesn't email without updates.
-    Accepts check_interval as a parameter in hours (default 24)
+    Runs scheduled checks and sends emails.
+
+    - check_hourly=True → every hour
+    - check_daily=int → hour of day for daily email
     """
     
+    if check_hourly and check_daily:
+        check_daily = False
+    
+    if check_hourly:
+        schedule("hourly", 0, receiver_email=receiver_email)
+    elif check_daily:
+        # Convert CLI string to int
+        if check_daily.lower() == "true":
+            hour = 18
+        else:
+            try:
+                hour = int(check_daily)
+            except ValueError:
+                print(f"Invalid check_daily value: {check_daily}")
+                exit(1)
+        schedule("daily", hour, receiver_email=receiver_email)
+    else:
+        print("No schedule selected.")
+
 @app.command()
 def now(receiver_email: str = None):
-    # Comma seperate
-    # FIXME: Fix if nonetype
-    receiver_emails = []
-    if receiver_email:
-        if "," in receiver_email:
-            receiver_emails = [email.strip() for email in receiver_email.split(",")]
-        else:
-            receiver_emails = [receiver_email.strip()]
-        
     """
     Checks for apt upgrades and emails them then exits.
     """
-    generate_email(receiver_emails)
+    generate_email(receiver_email)
     
-def generate_email(receiver_email: list):
+def generate_email(receiver_emails: Union[list, None]):
     services.apt.require_root()
     if not services.apt.detect_apt():
         print("Apt not found on this system.")
@@ -67,14 +105,21 @@ def generate_email(receiver_email: list):
     #    }
     #}
     
-    if exists(join(dirname(__file__), "users.json")):
-        with open(join(dirname(__file__), "users.json"), "r") as f:
-            users = json.load(f)
+    receiver_email = []
+    if receiver_emails:
+        if "," in receiver_emails:
+            receiver_email = [email.strip() for email in receiver_emails.split(",")]
+        else:
+            receiver_email = [receiver_emails.strip()]
     
-        receiver_email = users
-    else:
-        if receiver_email is None:
-            print("No email address provided.")
+    # If no CLI emails are provided
+    if not receiver_email:
+        users_json_path = join(dirname(__file__), "users.json")
+        if exists(users_json_path):
+            with open(users_json_path, "r") as f:
+                receiver_email = json.load(f)
+        else:
+            print("No email address provided and users.json not found.")
             exit(1)
     
     # Get how many security updates are available