feat: Use docker api to pull files from container

docker_agent_sandbox/sandbox.py

@@ -172,6 +172,42 @@ class DockerSandbox:
     # File I/O
     # ------------------------------------------------------------------
 
+    def _resolve_path(self, path: str) -> Path:
+        """Resolve *path* against working_dir if relative."""
+        p = Path(path)
+        if not p.is_absolute() and self._working_dir is not None:
+            p = Path(self._working_dir) / p
+        return p
+
+    def read_file(self, path: str) -> bytes:
+        """
+        Read the file at *path* from the container using ``get_archive``.
+
+        Returns the raw file bytes. Raises ``FileNotFoundError`` if the path
+        does not exist and ``RuntimeError`` if the container is not running.
+        """
+        if self._container is None:
+            raise RuntimeError("Sandbox container is not running.")
+
+        p = self._resolve_path(path)
+
+        try:
+            stream, _ = self._container.get_archive(str(p))
+        except docker.errors.NotFound:
+            raise FileNotFoundError(f"No such file in container: {path!r}") from None
+
+        buf = io.BytesIO()
+        for chunk in stream:
+            buf.write(chunk)
+        buf.seek(0)
+
+        with tarfile.open(fileobj=buf) as tar:
+            member = tar.getmembers()[0]
+            f = tar.extractfile(member)
+            if f is None:
+                raise IsADirectoryError(f"{path!r} is a directory, not a file")
+            return f.read()
+
     def write_file(self, path: str, content: str) -> None:
         """
         Write *content* to *path* inside the container using ``put_archive``.
@@ -182,9 +218,7 @@ class DockerSandbox:
         if self._container is None:
             raise RuntimeError("Sandbox container is not running.")
 
-        p = Path(path)
-        if not p.is_absolute() and self._working_dir is not None:
-            p = Path(self._working_dir) / p
+        p = self._resolve_path(path)
         encoded = content.encode("utf-8")
 
         self._container.exec_run(["mkdir", "-p", str(p.parent)])