radicle: introduce cob::TypedId

The combination of a COB's `TypeName` and `ObjectId` is useful for
parsing a Radicle COB refname, i.e. `refs/cobs/<typename>/<object
id>`.

Introduce `TypedId` for this and provide helper functions for parsing
from the git refname types, as well as being able to tell what kind of
COB it is.

Signed-off-by: Fintan Halpenny <fintan.halpenny@gmail.com>
X-Clacks-Overhead: GNU Terry Pratchett

radicle/src/cob.rs

@@ -18,3 +18,48 @@ pub use radicle_cob::{
     Store, TypeName, Update, Updated, Version,
 };
 pub use radicle_cob::{create, get, git, list, remove, update};
+
+#[derive(Clone, Debug, PartialEq, Eq, PartialOrd, Ord, Hash)]
+pub struct TypedId {
+    pub id: ObjectId,
+    pub type_name: TypeName,
+}
+
+#[derive(Debug, thiserror::Error)]
+pub enum ParseIdentifierError {
+    #[error(transparent)]
+    TypeName(#[from] TypeNameParse),
+    #[error(transparent)]
+    ObjectId(#[from] object::ParseObjectId),
+}
+
+impl TypedId {
+    pub fn is_issue(&self) -> bool {
+        self.type_name == *issue::TYPENAME
+    }
+
+    pub fn is_patch(&self) -> bool {
+        self.type_name == *patch::TYPENAME
+    }
+
+    pub fn from_namespaced(
+        n: &crate::git::Namespaced,
+    ) -> Result<Option<Self>, ParseIdentifierError> {
+        Self::from_qualified(&n.strip_namespace())
+    }
+
+    pub fn from_qualified(q: &crate::git::Qualified) -> Result<Option<Self>, ParseIdentifierError> {
+        match q.non_empty_iter() {
+            ("refs", "cobs", type_name, mut id) => {
+                let Some(id) = id.next() else {
+                    return Ok(None);
+                };
+                Ok(Some(Self {
+                    id: id.parse()?,
+                    type_name: type_name.parse()?,
+                }))
+            }
+            _ => Ok(None),
+        }
+    }
+}