diff --git a/src/routes/index.py b/src/routes/index.py
index 6e0add2..84439b9 100644
--- a/src/routes/index.py
+++ b/src/routes/index.py
@@ -1,8 +1,6 @@
-from os import path as os_path
-
 from config import Config
 from flask import Blueprint, flash, redirect, render_template, request
-from utils.misc import get_posts, post_filename
+from utils.misc import create_post, fresh_file_id, get_posts
 from werkzeug import Response
 
 name = __name__.split(".")[-1]
@@ -26,23 +24,15 @@ def new_post() -> Response:
     if Config.is_logged():
         content = request.form.get("p")
         if content:
-            # finding all posts
-            paths = get_posts()
-
             # finding an appropriate filename
-            filename = 0
-            if len(paths) > filename:
-                filename = paths.index(max(iter(paths), key=os_path.getmtime)) + 1
+            filename = fresh_file_id()
 
-            # creating the post
-            with open(
-                post_filename(filename),
-                "w",
-                encoding="utf-8",
-            ) as f:
-                f.write(content)
+            # create/update the post
+            update = create_post(filename, content)
 
-            flash(f"<a href='/read/{filename}'>post created</a>.")
+            flash(
+                f"<a href='/read/{filename}'>post {'updated' if update else 'created'}</a>."
+            )
         else:
             flash(f"invalid post: {content}")
     else:
diff --git a/src/utils/misc.py b/src/utils/misc.py
index ca6ad52..af8c54a 100644
--- a/src/utils/misc.py
+++ b/src/utils/misc.py
@@ -5,7 +5,7 @@ from os import remove as os_remove
 from config import Config
 
 
-def post_filename(number: int):
+def post_filename(number: int) -> str:
     """get filename of post"""
     return f"{Config.data_dir}/{number}.txt"
 
@@ -37,3 +37,37 @@ def delete_post(filename: str) -> bool:
     else:
         os_remove(filename)
         return True
+
+
+def fresh_file_id() -> int:
+    # finding all posts
+    paths = get_posts()
+
+    # use the latest file as the reference and increment the ID
+    filename = 0
+    if len(paths) > filename:
+        chosen = max(iter(paths), key=os_path.getmtime)
+
+        # add 1 to the chosen id
+        filename = int(chosen.split("/")[-1][:-4]) + 1
+    return filename
+
+
+def exist_post(file_id: int) -> bool:
+    try:
+        open(post_filename(file_id))
+        return True
+    except FileNotFoundError:
+        return False
+
+
+def create_post(file_id: int, content: str) -> bool:
+    """create a post"""
+    # check if the file already exists
+    update = exist_post(file_id)
+
+    # write into the file
+    with open(post_filename(file_id), "w", encoding="utf-8") as f:
+        f.write(content)
+
+    return update