From 9c2bbb6c056372171db7f6204fe901c0d2b15be4 Mon Sep 17 00:00:00 2001
From: Paul Hauner <paul@paulhauner.com>
Date: Sun, 16 Jun 2019 16:39:48 -0400
Subject: [PATCH] Add stubbed-out block processing to fork choice

---
 beacon_node/beacon_chain/src/beacon_chain.rs |  2 +-
 beacon_node/beacon_chain/src/fork_choice.rs  |  5 ++++-
 eth2/lmd_ghost/src/lib.rs                    | 15 ++++++++++++---
 eth2/lmd_ghost/src/reduced_tree.rs           |  7 ++++++-
 4 files changed, 23 insertions(+), 6 deletions(-)

diff --git a/beacon_node/beacon_chain/src/beacon_chain.rs b/beacon_node/beacon_chain/src/beacon_chain.rs
index 8602d32c77..d7ba67a37d 100644
--- a/beacon_node/beacon_chain/src/beacon_chain.rs
+++ b/beacon_node/beacon_chain/src/beacon_chain.rs
@@ -624,7 +624,7 @@ impl<T: BeaconChainTypes> BeaconChain<T> {
         self.store.put(&state_root, &state)?;
 
         // Register the new block with the fork choice service.
-        self.fork_choice.process_block(&state, &block)?;
+        self.fork_choice.process_block(&state, &block, block_root)?;
 
         // Execute the fork choice algorithm, enthroning a new head if discovered.
         //
diff --git a/beacon_node/beacon_chain/src/fork_choice.rs b/beacon_node/beacon_chain/src/fork_choice.rs
index 0d132386d5..7aba6fdf5d 100644
--- a/beacon_node/beacon_chain/src/fork_choice.rs
+++ b/beacon_node/beacon_chain/src/fork_choice.rs
@@ -89,6 +89,7 @@ impl<T: BeaconChainTypes> ForkChoice<T> {
         &self,
         state: &BeaconState<T::EthSpec>,
         block: &BeaconBlock,
+        block_root: Hash256,
     ) -> Result<()> {
         // Note: we never count the block as a latest message, only attestations.
         //
@@ -100,6 +101,8 @@ impl<T: BeaconChainTypes> ForkChoice<T> {
             self.process_attestation_from_block(state, attestation)?;
         }
 
+        self.backend.process_block(block_root, block.slot)?;
+
         Ok(())
     }
 
@@ -138,7 +141,7 @@ impl<T: BeaconChainTypes> ForkChoice<T> {
 
             for validator_index in validator_indices {
                 self.backend
-                    .process_message(validator_index, block_hash, block_slot)?;
+                    .process_attestation(validator_index, block_hash, block_slot)?;
             }
         }
 
diff --git a/eth2/lmd_ghost/src/lib.rs b/eth2/lmd_ghost/src/lib.rs
index 59495e382c..8f5d0b5299 100644
--- a/eth2/lmd_ghost/src/lib.rs
+++ b/eth2/lmd_ghost/src/lib.rs
@@ -9,18 +9,27 @@ pub use reduced_tree::ThreadSafeReducedTree;
 pub type Result<T> = std::result::Result<T, String>;
 
 pub trait LmdGhost<S: Store, E: EthSpec>: Send + Sync {
-    fn new(store: Arc<S>, genesis_root: Hash256) -> Self;
+    /// Create a new instance, with the given `store` and `finalized_root`.
+    fn new(store: Arc<S>, finalized_root: Hash256) -> Self;
 
-    fn process_message(
+    /// Process an attestation message from some validator that attests to some `block_hash`
+    /// representing a block at some `block_slot`.
+    fn process_attestation(
         &self,
         validator_index: usize,
         block_hash: Hash256,
         block_slot: Slot,
     ) -> Result<()>;
 
+    /// Process a block that was seen on the network.
+    fn process_block(&self, block_hash: Hash256, block_slot: Slot) -> Result<()>;
+
+    /// Returns the head of the chain, starting the search at `start_block_root` and moving upwards
+    /// (in block height).
     fn find_head<F>(&self, start_block_root: Hash256, weight: F) -> Result<Hash256>
     where
         F: Fn(usize) -> Option<u64> + Copy;
 
-    fn update_finalized_root(&self, new_root: Hash256) -> Result<()>;
+    /// Provide an indication that the blockchain has been finalized at the given `finalized_root`.
+    fn update_finalized_root(&self, finalized_root: Hash256) -> Result<()>;
 }
diff --git a/eth2/lmd_ghost/src/reduced_tree.rs b/eth2/lmd_ghost/src/reduced_tree.rs
index 84249b603f..f6db34e36c 100644
--- a/eth2/lmd_ghost/src/reduced_tree.rs
+++ b/eth2/lmd_ghost/src/reduced_tree.rs
@@ -40,7 +40,7 @@ where
         }
     }
 
-    fn process_message(
+    fn process_attestation(
         &self,
         validator_index: usize,
         block_hash: Hash256,
@@ -52,6 +52,11 @@ where
             .map_err(Into::into)
     }
 
+    /// Process a block that was seen on the network.
+    fn process_block(&self, block_hash: Hash256, block_slot: Slot) -> SuperResult<()> {
+        unimplemented!();
+    }
+
     fn find_head<F>(&self, start_block_root: Hash256, weight_fn: F) -> SuperResult<Hash256>
     where
         F: Fn(usize) -> Option<u64> + Copy,