Move gossipsub into a separate crate (#5401)

* move gossipsub into a separate crate

* Merge branch 'unstable' of github.com:sigp/lighthouse into separate-gossipsub

* address review 2

* clippy beta

* update logging to log gossipsub logs

beacon_node/lighthouse_network/gossipsub/src/topic.rs

@@ -0,0 +1,123 @@
+// Copyright 2020 Sigma Prime Pty Ltd.
+//
+// Permission is hereby granted, free of charge, to any person obtaining a
+// copy of this software and associated documentation files (the "Software"),
+// to deal in the Software without restriction, including without limitation
+// the rights to use, copy, modify, merge, publish, distribute, sublicense,
+// and/or sell copies of the Software, and to permit persons to whom the
+// Software is furnished to do so, subject to the following conditions:
+//
+// The above copyright notice and this permission notice shall be included in
+// all copies or substantial portions of the Software.
+//
+// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS
+// OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
+// FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
+// DEALINGS IN THE SOFTWARE.
+
+use crate::rpc_proto::proto;
+use base64::prelude::*;
+use prometheus_client::encoding::EncodeLabelSet;
+use quick_protobuf::Writer;
+use sha2::{Digest, Sha256};
+use std::fmt;
+
+/// A generic trait that can be extended for various hashing types for a topic.
+pub trait Hasher {
+    /// The function that takes a topic string and creates a topic hash.
+    fn hash(topic_string: String) -> TopicHash;
+}
+
+/// A type for representing topics who use the identity hash.
+#[derive(Debug, Clone)]
+pub struct IdentityHash {}
+impl Hasher for IdentityHash {
+    /// Creates a [`TopicHash`] as a raw string.
+    fn hash(topic_string: String) -> TopicHash {
+        TopicHash { hash: topic_string }
+    }
+}
+
+#[derive(Debug, Clone)]
+pub struct Sha256Hash {}
+impl Hasher for Sha256Hash {
+    /// Creates a [`TopicHash`] by SHA256 hashing the topic then base64 encoding the
+    /// hash.
+    fn hash(topic_string: String) -> TopicHash {
+        use quick_protobuf::MessageWrite;
+
+        let topic_descripter = proto::TopicDescriptor {
+            name: Some(topic_string),
+            auth: None,
+            enc: None,
+        };
+        let mut bytes = Vec::with_capacity(topic_descripter.get_size());
+        let mut writer = Writer::new(&mut bytes);
+        topic_descripter
+            .write_message(&mut writer)
+            .expect("Encoding to succeed");
+        let hash = BASE64_STANDARD.encode(Sha256::digest(&bytes));
+        TopicHash { hash }
+    }
+}
+
+#[derive(Debug, Clone, PartialEq, Eq, Hash, PartialOrd, Ord, EncodeLabelSet)]
+pub struct TopicHash {
+    /// The topic hash. Stored as a string to align with the protobuf API.
+    hash: String,
+}
+
+impl TopicHash {
+    pub fn from_raw(hash: impl Into<String>) -> TopicHash {
+        TopicHash { hash: hash.into() }
+    }
+
+    pub fn into_string(self) -> String {
+        self.hash
+    }
+
+    pub fn as_str(&self) -> &str {
+        &self.hash
+    }
+}
+
+/// A gossipsub topic.
+#[derive(Debug, Clone, PartialEq, Eq, PartialOrd, Ord)]
+pub struct Topic<H: Hasher> {
+    topic: String,
+    phantom_data: std::marker::PhantomData<H>,
+}
+
+impl<H: Hasher> From<Topic<H>> for TopicHash {
+    fn from(topic: Topic<H>) -> TopicHash {
+        topic.hash()
+    }
+}
+
+impl<H: Hasher> Topic<H> {
+    pub fn new(topic: impl Into<String>) -> Self {
+        Topic {
+            topic: topic.into(),
+            phantom_data: std::marker::PhantomData,
+        }
+    }
+
+    pub fn hash(&self) -> TopicHash {
+        H::hash(self.topic.clone())
+    }
+}
+
+impl<H: Hasher> fmt::Display for Topic<H> {
+    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+        write!(f, "{}", self.topic)
+    }
+}
+
+impl fmt::Display for TopicHash {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        write!(f, "{}", self.hash)
+    }
+}