Addressing #473 ... if I understood the ticket right, we want to pass… (#1395)

* Addressing #473 ... if I understood the ticket right, we want to pass through whatever the application provides as a topic identifier, leaving hashing (or not hashing) up to the application.

* Remove TopicDescriptor and use Topic newtype everywhere

* PR feedback

Use From<Topic> instead of Into<String>
Use impl Into<Topic> instead of Topic in public API

Co-authored-by: Peat Bakke <peat@peat.org>

protocols/floodsub/src/topic.rs

@@ -18,93 +18,27 @@
 // FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
 // DEALINGS IN THE SOFTWARE.
 
-use bs58;
-use crate::rpc_proto;
-use prost::Message;
-
-/// Represents the hash of a topic.
-///
-/// Instead of a using the topic as a whole, the API of floodsub uses a hash of the topic. You only
-/// have to build the hash once, then use it everywhere.
-#[derive(Debug, Clone, PartialEq, Eq, Hash)]
-pub struct TopicHash {
-    hash: String,
-}
-
-impl TopicHash {
-    /// Builds a new `TopicHash` from the given hash.
-    pub fn from_raw(hash: String) -> TopicHash {
-        TopicHash { hash }
-    }
-
-    pub fn into_string(self) -> String {
-        self.hash
-    }
-}
-
 /// Built topic.
-#[derive(Debug, Clone)]
-pub struct Topic {
-    descriptor: rpc_proto::TopicDescriptor,
-    hash: TopicHash,
-}
+#[derive(Debug, Clone, PartialEq, Eq, Hash)]
+pub struct Topic(String);
 
 impl Topic {
-    /// Returns the hash of the topic.
-    pub fn hash(&self) -> &TopicHash {
-        &self.hash
+    /// Returns the id of the topic.
+    #[inline]
+    pub fn id(&self) -> &str {
+        &self.0
     }
-}
 
-impl AsRef<TopicHash> for Topic {
-    fn as_ref(&self) -> &TopicHash {
-        &self.hash
-    }
-}
-
-impl From<Topic> for TopicHash {
-    fn from(topic: Topic) -> TopicHash {
-        topic.hash
-    }
-}
-
-impl<'a> From<&'a Topic> for TopicHash {
-    fn from(topic: &'a Topic) -> TopicHash {
-        topic.hash.clone()
-    }
-}
-
-/// Builder for a `TopicHash`.
-#[derive(Debug, Clone)]
-pub struct TopicBuilder {
-    builder: rpc_proto::TopicDescriptor,
-}
-
-impl TopicBuilder {
-    pub fn new<S>(name: S) -> TopicBuilder
+    pub fn new<S>(name: S) -> Topic
     where
         S: Into<String>,
     {
-        TopicBuilder {
-            builder: rpc_proto::TopicDescriptor {
-                name: Some(name.into()),
-                auth: None,
-                enc: None
-            }
-        }
-    }
-
-    /// Turns the builder into an actual `Topic`.
-    pub fn build(self) -> Topic {
-        let mut buf = Vec::with_capacity(self.builder.encoded_len());
-        self.builder.encode(&mut buf).expect("Vec<u8> provides capacity as needed");
-        // TODO: https://github.com/libp2p/rust-libp2p/issues/473
-        let hash = TopicHash {
-            hash: bs58::encode(&buf).into_string(),
-        };
-        Topic {
-            descriptor: self.builder,
-            hash,
-        }
+        Topic(name.into())
+    }
+}
+
+impl From<Topic> for String {
+    fn from(topic: Topic) -> String {
+        topic.0
     }
 }