Added checks before downloading modpack

main.py

@@ -120,26 +120,56 @@ def backup_mods(modpack_dir, mods_backup_dir):
     else:
         print("No mods directory found. No backup required.")
 
-# Downloads the modpack.
-def install_modpack(modpack_url, modpack_dir):
-    print("Downloading modpack...")
+# Helper function to save the list of mod filenames as a manifest.
+def save_modpack_manifest(modpack_dir, mod_filenames):
+    manifest_path = os.path.join(modpack_dir, 'modpack_manifest.txt')
+    with open(manifest_path, 'w') as manifest_file:
+        for filename in mod_filenames:
+            manifest_file.write(f"{filename}\n")
+
+# Function to check if modpack is already installed based on the manifest.
+def is_modpack_installed(modpack_dir):
+    manifest_path = os.path.join(modpack_dir, 'modpack_manifest.txt')
+    if not os.path.exists(manifest_path):
+        return False  # Manifest does not exist, modpack likely not installed.
+    with open(manifest_path, 'r') as manifest_file:
+        manifest_files = {line.strip() for line in manifest_file}
+    existing_files = {file for file in os.listdir(modpack_dir) if os.path.isfile(os.path.join(modpack_dir, file))}
+    return manifest_files.issubset(existing_files) and not manifest_files == set()
+
+# Updated install_modpack function.
+def install_modpack(modpack_url, modpack_dir, mods_backup_dir):
+    if is_modpack_installed(modpack_dir):
+        print("Modpack is already installed according to the manifest. Skipping download and installation.")
+        return
+
+    print("Modpack needs to be downloaded or updated. Proceeding with the installation.")
     try:
+        backup_mods(modpack_dir, mods_backup_dir)
         zip_path = os.path.join(modpack_dir, "modpack.zip")
         download_with_progress_bar(modpack_url, zip_path)
         print("Extracting modpack...")
+
+        modpack_files = set()
         with zipfile.ZipFile(zip_path) as modpack_zip:
             for member in modpack_zip.namelist():
-                filename = os.path.basename(member)
-                if not filename:
-                    continue
+                if not member.endswith("/"):  # Ignore directories
+                    filename = os.path.basename(member)  # Get base name to avoid directory structure
+                    if filename:  # Ignore any empty names
+                        # Compute target path for extraction
+                        target_path = os.path.join(modpack_dir, filename)
+                        modpack_files.add(filename)
 
+                        # Extract each file to its correct location
                         source = modpack_zip.open(member)
-                target = open(os.path.join(modpack_dir, filename), "wb")
+                        target = open(target_path, "wb")
 
                         with source, target:
                             shutil.copyfileobj(source, target)
+
         print("Modpack installed successfully.")
-        os.remove(zip_path)
+        os.remove(zip_path)  # Clean up the downloaded ZIP file
+        save_modpack_manifest(modpack_dir, modpack_files)  # Update the manifest
     except Exception as e:
         print(f"An error occurred during modpack installation: {e}")
 
@@ -149,8 +179,7 @@ def main():
         check_minecraft_installation(minecraft_dir)
         install_forge(forge_dir, forge_url)
         install_forge_libraries(forge_libraries_dir, forge_libraries_url)
-        backup_mods(modpack_dir, mods_backup_dir)
-        install_modpack(modpack_url, modpack_dir)
+        install_modpack(modpack_url, modpack_dir, mods_backup_dir)
     except KeyboardInterrupt:
         print("\033[91m\nSession ended by user.\033[0m")
     except Exception as e: