add db method to remove a post

src/db.rs

@@ -100,8 +100,8 @@ impl Database {
 
     /// Remove a peer from the database, as represented by the given public
     /// key.
-    pub fn remove_peer(&self, public_key: &str) -> Result<Option<IVec>> {
-        self.peer_tree.remove(&public_key)
+    pub fn remove_peer(&self, public_key: &str) -> Result<()> {
+        self.peer_tree.remove(&public_key).map(|_| ())
     }
 
     /// Get a list of all peers in the peer tree. The public key of each peer
@@ -120,6 +120,8 @@ impl Database {
     /// the public key of the peer who authored the post and the key of the
     /// post itself, separated by an underscore. The Post is serialized as
     /// bincode before the database entry is inserted.
+    ///
+    /// This method can also be used to update an existing database entry.
     pub fn add_post(&self, public_key: &str, post: Post) -> Result<Option<IVec>> {
         let post_key = format!("{}_{}", public_key, post.key);
         let post_bytes = bincode::serialize(&post).unwrap();
@@ -175,5 +177,15 @@ impl Database {
         Ok(post)
     }
 
-    // TODO: remove_post
+    /// Remove a single post from the post tree, authored by the given public
+    /// key and defined by the given message ID.
+    pub fn remove_post(&self, public_key: &str, msg_id: &str) -> Result<()> {
+        let post_key = format!("{}_{}", public_key, msg_id);
+
+        // .remove() would ordinarily return the value of the deleted entry
+        // as an Option, returning None if the post_key was not found.
+        // We don't care about the value of the deleted entry so we simply
+        // map the Option to ().
+        self.post_tree.remove(post_key.as_bytes()).map(|_| ())
+    }
 }