Baseline modular DNS sync

dns_sync/normalizer.py

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+import ipaddress
+import re
+
+_LABEL_RE = re.compile(r"^[a-z0-9](?:[a-z0-9-]{0,61}[a-z0-9])?$")
+
+
+def normalize_hostname(value: str, allow_wildcard: bool = True) -> tuple[str, bool]:
+    hostname = value.strip().rstrip(".").lower()
+    wildcard = False
+
+    if allow_wildcard and hostname.startswith("*."):
+        wildcard = True
+        hostname = hostname[2:]
+
+    if not hostname or len(hostname) > 253:
+        raise RuntimeError(f"Invalid hostname: {value!r}")
+
+    for label in hostname.split("."):
+        if not _LABEL_RE.match(label):
+            raise RuntimeError(f"Invalid hostname: {value!r}")
+
+    normalized = f"*.{hostname}" if wildcard else hostname
+    return normalized, wildcard
+
+
+def normalize_ipv4(value: str, label: str = "IP") -> str:
+    try:
+        addr = ipaddress.ip_address(value.strip())
+    except ValueError as exc:
+        raise RuntimeError(f"{label}: {value!r} is not a valid IP address") from exc
+
+    if addr.version != 4:
+        raise RuntimeError(f"{label}: only IPv4 is currently supported")
+
+    return str(addr)