diff --git a/autoupdate_app_sources/autoupdate_app_sources.py b/autoupdate_app_sources/autoupdate_app_sources.py
index 9333fe8..8733539 100644
--- a/autoupdate_app_sources/autoupdate_app_sources.py
+++ b/autoupdate_app_sources/autoupdate_app_sources.py
@@ -1,3 +1,4 @@
+import hashlib
 import re
 import sys
 import requests
@@ -39,6 +40,7 @@ class AppAutoUpdater():
         if not os.path.exists(app_path + "/manifest.toml"):
             raise Exception("manifest.toml doesnt exists?")
 
+        self.app_path = app_path
         manifest = toml.load(open(app_path + "/manifest.toml"))
 
         self.current_version = manifest["version"].split("~")[0]
@@ -68,7 +70,57 @@ class AppAutoUpdater():
 
             print(f"Current version in manifest: {self.current_version}")
             print(f"Newest version on upstream: {version}")
-            print(assets)
+
+            if source == "main":
+                if self.current_version == version:
+                    print(f"Version is still {version}, no update required for {source}")
+                    continue
+            else:
+                if isinstance(assets, str) and infos["url"] == assets:
+                    print(f"URL is still up to date for asset {source}")
+                    continue
+                elif isinstance(assets, dict) and assets == {k: infos[k]["url"] for k in assets.keys()}:
+                    print(f"URLs are still up to date for asset {source}")
+                    continue
+
+            if isinstance(assets, str):
+                sha256 = self.sha256_of_remote_file(assets)
+            elif isinstance(assets, dict):
+                sha256 = {url: self.sha256_of_remote_file(url) for url in assets.values()}
+
+            # FIXME: should create a tmp dir in which to make those changes
+
+            if source == "main":
+                self.replace_upstream_version_in_manifest(version)
+            if isinstance(assets, str):
+                self.replace_string_in_manifest(infos["url"], assets)
+                self.replace_string_in_manifest(infos["sha256"], sha256)
+            elif isinstance(assets, dict):
+                for key, url in assets.items():
+                    self.replace_string_in_manifest(infos[key]["url"], url)
+                    self.replace_string_in_manifest(infos[key]["sha256"], sha256[url])
+
+    def replace_upstream_version_in_manifest(self, new_version):
+
+        # FIXME : should be done in a tmp git clone ...?
+        manifest_raw = open(self.app_path + "/manifest.toml").read()
+
+        def repl(m):
+            return m.group(1) + new_version + m.group(3)
+
+        print(re.findall(r"(\s*version\s*=\s*[\"\'])([\d\.]+)(\~ynh\d+[\"\'])", manifest_raw))
+
+        manifest_new = re.sub(r"(\s*version\s*=\s*[\"\'])([\d\.]+)(\~ynh\d+[\"\'])", repl, manifest_raw)
+
+        open(self.app_path + "/manifest.toml", "w").write(manifest_new)
+
+    def replace_string_in_manifest(self, pattern, replace):
+
+        manifest_raw = open(self.app_path + "/manifest.toml").read()
+
+        manifest_new = manifest_raw.replace(pattern, replace)
+
+        open(self.app_path + "/manifest.toml", "w").write(manifest_new)
 
     def get_latest_version_and_asset(self, strategy, asset, infos):
 
@@ -120,6 +172,17 @@ class AppAutoUpdater():
         assert r.status_code == 200, r
         return r.json()
 
+    def sha256_of_remote_file(self, url):
+        try:
+            r = requests.get(url, stream=True)
+            m = hashlib.sha256()
+            for data in r.iter_content(8192):
+                m.update(data)
+            return m.hexdigest()
+        except Exception as e:
+            print(f"Failed to compute sha256 for {url} : {e}")
+            return None
+
 
 if __name__ == "__main__":
     AppAutoUpdater(sys.argv[1]).run()