Step 2

app/path_utils.py

@@ -0,0 +1,32 @@
+"""Helpers for working with hex-encoded routing paths."""
+
+
+def get_path_hop_width(path_hex: str | None, path_len: int | None) -> int:
+    """Return hop width in hex chars, falling back to legacy 1-byte hops."""
+    if not path_hex:
+        return 2
+    if isinstance(path_len, int) and path_len > 0 and len(path_hex) % path_len == 0:
+        hop_width = len(path_hex) // path_len
+        if hop_width > 0 and hop_width % 2 == 0:
+            return hop_width
+    return 2
+
+
+def split_path_hops(path_hex: str | None, path_len: int | None) -> list[str]:
+    """Split a hex path string into hop-sized chunks."""
+    if not path_hex:
+        return []
+
+    hop_width = get_path_hop_width(path_hex, path_len)
+    normalized = path_hex.lower()
+    return [
+        normalized[i : i + hop_width]
+        for i in range(0, len(normalized), hop_width)
+        if i + hop_width <= len(normalized)
+    ]
+
+
+def first_path_hop(path_hex: str | None, path_len: int | None) -> str | None:
+    """Return the first hop from a hex path string, if any."""
+    hops = split_path_hops(path_hex, path_len)
+    return hops[0] if hops else None