WIP game patcher

Now worthless can patch the game using xdelta3-python

worthless/installer.py

@@ -84,12 +84,16 @@ class Installer:
         self.temp_path.mkdir(parents=True, exist_ok=True)
         config_file = self._gamedir.joinpath("config.ini")
         self._config_file = config_file.resolve()
+        self._download_chunk = 8192
         self._version = None
         self._overseas = overseas
         self._launcher = Launcher(self._gamedir, overseas=self._overseas)
         self._version = self.get_game_version()
 
-    async def _download_file(self, file_url: str, file_name: str, file_len: int = None):
+    def set_download_chunk(self, chunk: int):
+        self._download_chunk = chunk
+
+    async def _download_file(self, file_url: str, file_name: str, file_len: int = None, overwrite=False):
         """
         Download file name to temporary directory,
         :param file_url:
@@ -98,9 +102,10 @@ class Installer:
         """
         params = {}
         file_path = AsyncPath(self.temp_path).joinpath(file_name)
+        if overwrite:
+            await file_path.unlink(missing_ok=True)
         if file_path.exists():
-            async with file_path.open("rb") as f:
-                cur_len = len(await f.read())
+            cur_len = len(await file_path.read_bytes())
             params |= {
                 "Range": f"bytes={cur_len}-{file_len if file_len else ''}"
             }
@@ -110,7 +115,7 @@ class Installer:
             rsp = await session.get(file_url, params=params, timeout=None)
             rsp.raise_for_status()
             while True:
-                chunk = await rsp.content.read(8192)
+                chunk = await rsp.content.read(self._download_chunk)
                 if not chunk:
                     break
                 async with file_path.open("ab") as f:
@@ -207,7 +212,9 @@ class Installer:
         # Update game version on local variable.
         self._version = self.get_game_version()
 
-    async def download_full_game(self):
+    async def download_full_game(self, overwrite: bool = False):
+        if self._version and not overwrite:
+            raise ValueError("Game already exists")
         archive = await self._launcher.get_resource_info()
         if archive is None:
             raise RuntimeError("Failed to fetch game resource info.")