refactor(cli): model image references as a value object

libs/cli/langgraph_cli/image_reference.py

@@ -0,0 +1,32 @@
+from __future__ import annotations
+
+from dataclasses import dataclass, replace
+
+DIGEST_SEPARATOR = "@sha256:"
+TAG_SEPARATOR = ":"
+PATH_SEPARATOR = "/"
+
+
+@dataclass(frozen=True, slots=True)
+class ImageReference:
+    repository: str
+    tag: str | None = None
+
+    @classmethod
+    def parse(cls, reference: str) -> ImageReference:
+        path_start = reference.rfind(PATH_SEPARATOR) + 1
+        name, separator, tag = reference[path_start:].partition(TAG_SEPARATOR)
+        if not separator:
+            return cls(reference)
+        return cls(reference[:path_start] + name, tag)
+
+    def with_tag(self, tag: str) -> ImageReference:
+        return replace(self, tag=tag)
+
+    def matches_digest(self, repo_digest: str) -> bool:
+        return repo_digest.startswith(f"{self.repository}{DIGEST_SEPARATOR}")
+
+    def __str__(self) -> str:
+        if self.tag is None:
+            return self.repository
+        return f"{self.repository}{TAG_SEPARATOR}{self.tag}"