feat: complete client runtime foundation

src/archive_clients/probes.py

@@ -4,6 +4,7 @@ from __future__ import annotations
 
 import os
 import tempfile
+import fcntl
 from dataclasses import dataclass
 from pathlib import Path
 
@@ -18,9 +19,23 @@ class FilesystemProbe:
     readable: bool
     writable: bool
     hard_link: bool
+    reflink: bool
     sparse_files: bool
 
 
+def probe_writable_directory(path: Path) -> None:
+    if not path.is_absolute() or not path.is_dir():
+        raise ProbeError(f"configured directory is not existing and absolute: {path}")
+    try:
+        descriptor, raw_path = tempfile.mkstemp(
+            prefix=".archive-control-write-probe-", dir=path
+        )
+        os.close(descriptor)
+        Path(raw_path).unlink()
+    except OSError as exc:
+        raise ProbeError(f"configured directory is not writable: {path}") from exc
+
+
 def probe_root(root: Path) -> FilesystemProbe:
     if not root.is_absolute() or not root.is_dir():
         raise ProbeError(f"configured root is not an existing absolute directory: {root}")
@@ -28,6 +43,7 @@ def probe_root(root: Path) -> FilesystemProbe:
         raise ProbeError(f"configured root permissions are insufficient: {root}")
     source: Path | None = None
     linked: Path | None = None
+    cloned: Path | None = None
     try:
         descriptor, raw_path = tempfile.mkstemp(prefix=".archive-control-probe-", dir=root)
         source = Path(raw_path)
@@ -44,11 +60,20 @@ def probe_root(root: Path) -> FilesystemProbe:
             hard_link = linked.stat().st_ino == source.stat().st_ino
         except OSError:
             hard_link = False
-        return FilesystemProbe(root, True, True, hard_link, sparse)
+        cloned = source.with_name(f"{source.name}.clone")
+        try:
+            with source.open("rb") as source_file, cloned.open("xb") as clone_file:
+                fcntl.ioctl(clone_file.fileno(), 0x40049409, source_file.fileno())
+            reflink = cloned.stat().st_size == source.stat().st_size
+        except OSError:
+            reflink = False
+        return FilesystemProbe(root, True, True, hard_link, reflink, sparse)
     except OSError as exc:
         raise ProbeError(f"filesystem capability probe failed for {root}") from exc
     finally:
         if linked is not None:
             linked.unlink(missing_ok=True)
+        if cloned is not None:
+            cloned.unlink(missing_ok=True)
         if source is not None:
             source.unlink(missing_ok=True)