Create the fork-choice crate.

- Adds the naive fork choice (longest chain) rule.
- Adds basic documentation for the crate.

Cargo.toml

@@ -3,7 +3,7 @@ members = [
 	"eth2/attester",
 	"eth2/block_producer",
 	"eth2/genesis",
-	"eth2/naive_fork_choice",
+	"eth2/fork_choice",
 	"eth2/types",
 	"eth2/utils/bls",
 	"eth2/utils/boolean-bitfield",

eth2/fork_choice/Cargo.toml

@@ -1,10 +1,11 @@
 [package]
-name = "naive_fork_choice"
+name = "fork_choice"
 version = "0.1.0"
-authors = ["Paul Hauner <paul@paulhauner.com>"]
+authors = ["Age Manning <Age@AgeManning.com>"]
 edition = "2018"
 
 [dependencies]
 db = { path = "../../beacon_node/db" }
 ssz = { path = "../utils/ssz" }
 types = { path = "../types" }
+

eth2/fork_choice/src/lib.rs

@@ -0,0 +1,24 @@
+//! This crate stores the various implementations of fork-choice rules that can be used for the
+//! beacon blockchain.
+//!
+//! There are four implementations. One is the naive longest chain rule (primarily for testing
+//! purposes). The other three are proposed implementations of the LMD-GHOST fork-choice rule with various forms of optimisation.
+//!
+//! The current implementations are:
+//! - [`longest-chain`]: Simplistic longest-chain fork choice - primarily for testing, **not for
+//! production**.
+//! - [`basic_lmd_ghost`]: This is a simple and very inefficient implementation given in the ethereum 2.0
+//! specifications (https://github.com/ethereum/eth2.0-specs/blob/v0.1/specs/core/0_beacon-chain.md#get_block_root).
+//! - [`optimised_lmd_ghost`]: This is an optimised version of the naive implementation as proposed
+//! by Vitalik. The reference implementation can be found at: https://github.com/ethereum/research/blob/master/ghost/ghost.py
+//! - [`protolambda_lmd_ghost`]: Another optimised version of LMD-GHOST designed by @protolambda.
+//! The go implementation can be found here: https://github.com/protolambda/lmd-ghost.
+//!
+//! [`basic_lmd_ghost`]: struct.BasicLmdGhost.html
+//! [`optimised_lmd_ghost`]: struct.OptimisedLmdGhost.html
+//! [`protolambda_lmd_ghost`]: struct.ProtolambdaLmdGhost.html
+
+pub mod basic_lmd_ghost;
+pub mod longest_chain;
+pub mod optimised_lmd_ghost;
+pub mod protolambda_lmd_ghost;

eth2/fork_choice/src/longest_chain.rs

@@ -14,7 +14,7 @@ pub enum ForkChoiceError {
     DBError(String),
 }
 
-pub fn naive_fork_choice<T>(
+pub fn longest_chain<T>(
     head_block_hashes: &[Hash256],
     block_store: &Arc<BeaconBlockStore<T>>,
 ) -> Result<Option<usize>, ForkChoiceError>