cob: Implement COB removal function

Signed-off-by: Alexis Sellier <alexis@radicle.xyz>

radicle-cob/src/object/collaboration.rs

@@ -23,6 +23,9 @@ pub mod info;
 mod list;
 pub use list::list;
 
+mod remove;
+pub use remove::remove;
+
 mod update;
 pub use update::{update, Update};
 

radicle-cob/src/object/collaboration/error.rs

@@ -24,6 +24,13 @@ pub enum Create {
     SignerIsNotAuthor,
 }
 
+#[derive(Debug, Error)]
+#[error("failed to remove object: {err}")]
+pub struct Remove {
+    #[source]
+    pub(crate) err: Box<dyn std::error::Error + Send + Sync + 'static>,
+}
+
 #[derive(Debug, Error)]
 pub enum Retrieve {
     #[error(transparent)]

radicle-cob/src/object/collaboration/remove.rs

@@ -0,0 +1,33 @@
+// Copyright © 2022 The Radicle Link Contributors
+//
+// This file is part of radicle-link, distributed under the GPLv3 with Radicle
+// Linking Exception. For full terms see the included LICENSE file.
+
+use crate::{ObjectId, Store, TypeName};
+
+use super::error;
+
+/// Remove a [`crate::CollaborativeObject`].
+///
+/// The `storage` is the backing storage for storing
+/// [`crate::Change`]s at content-addressable locations. Please see
+/// [`Store`] for further information.
+///
+/// The `typename` is the type of object to be found, while the
+/// `object_id` is the identifier for the particular object under that
+/// type.
+pub fn remove<S>(
+    storage: &S,
+    identifier: &S::Identifier,
+    typename: &TypeName,
+    oid: &ObjectId,
+) -> Result<(), error::Remove>
+where
+    S: Store,
+{
+    storage
+        .remove(identifier, typename, oid)
+        .map_err(|e| error::Remove { err: e.into() })?;
+
+    Ok(())
+}

radicle-cob/src/object/storage.rs

@@ -61,6 +61,7 @@ pub trait Storage {
     type ObjectsError: Error + Send + Sync + 'static;
     type TypesError: Error + Send + Sync + 'static;
     type UpdateError: Error + Send + Sync + 'static;
+    type RemoveError: Error + Send + Sync + 'static;
 
     type Identifier;
 
@@ -84,6 +85,14 @@ pub trait Storage {
         object_id: &ObjectId,
         change: &Change,
     ) -> Result<(), Self::UpdateError>;
+
+    /// Remove a ref to a particular collaborative object
+    fn remove(
+        &self,
+        identifier: &Self::Identifier,
+        typename: &TypeName,
+        object_id: &ObjectId,
+    ) -> Result<(), Self::RemoveError>;
 }
 
 pub mod convert {

radicle-cob/src/test/storage.rs

@@ -96,6 +96,7 @@ impl object::Storage for Storage {
     type ObjectsError = error::Objects;
     type TypesError = error::Objects;
     type UpdateError = git2::Error;
+    type RemoveError = git2::Error;
 
     type Identifier = Urn;
 
@@ -157,4 +158,21 @@ impl object::Storage for Storage {
         self.raw.reference(&name, id.into(), true, "new change")?;
         Ok(())
     }
+
+    fn remove(
+        &self,
+        identifier: &Self::Identifier,
+        typename: &crate::TypeName,
+        object_id: &ObjectId,
+    ) -> Result<(), Self::RemoveError> {
+        let name = format!(
+            "refs/rad/{}/cobs/{}/{}",
+            identifier.to_path(),
+            typename,
+            object_id
+        );
+        self.raw.find_reference(&name)?.delete()?;
+
+        Ok(())
+    }
 }

radicle/src/storage/git.rs

@@ -705,6 +705,7 @@ impl cob::object::Storage for Repository {
     type ObjectsError = CobObjectsError;
     type TypesError = CobTypesError;
     type UpdateError = git2::Error;
+    type RemoveError = git2::Error;
 
     type Identifier = RemoteId;
 
@@ -780,6 +781,19 @@ impl cob::object::Storage for Repository {
 
         Ok(())
     }
+
+    fn remove(
+        &self,
+        identifier: &Self::Identifier,
+        typename: &cob::TypeName,
+        object_id: &cob::ObjectId,
+    ) -> Result<(), Self::RemoveError> {
+        let mut reference = self
+            .backend
+            .find_reference(git::refs::storage::cob(identifier, typename, object_id).as_str())?;
+
+        reference.delete().map_err(Self::RemoveError::from)
+    }
 }
 
 pub mod trailers {