From 5d85c62f6e5fbf519b5a9a61f0b28bcf67b2ee27 Mon Sep 17 00:00:00 2001
From: Paul Hauner <paul@paulhauner.com>
Date: Sat, 20 Oct 2018 21:42:07 +1100
Subject: [PATCH] Finish implementing genesis (without tests)

---
 beacon_chain/chain/src/lib.rs                 | 44 ++++++++++++-------
 beacon_chain/types/src/shard_and_committee.rs |  2 +-
 2 files changed, 29 insertions(+), 17 deletions(-)

diff --git a/beacon_chain/chain/src/lib.rs b/beacon_chain/chain/src/lib.rs
index 27d605403..e4ec8ec8d 100644
--- a/beacon_chain/chain/src/lib.rs
+++ b/beacon_chain/chain/src/lib.rs
@@ -8,7 +8,6 @@ use types::{
     CrosslinkRecord,
     CrystallizedState,
     Hash256,
-    ValidatorRecord,
 };
 use validator_induction::{
     ValidatorInductor,
@@ -21,13 +20,24 @@ use validator_shuffling::{
 
 pub const INITIAL_FORK_VERSION: u32 = 0;
 
+/// A ChainHead structure represents the "head" or "tip" of a beacon chain blockchain.
+///
+/// Initially, a "gensis" chainhead will be created and then new blocks will be built upon it.
 pub struct ChainHead {
-    active_state: ActiveState,
-    crystallized_state: CrystallizedState,
-    config: ChainConfig,
+    /// The hash of the block that is the head of the chain.
+    pub head_hash: Hash256,
+    /// The active state at this head block.
+    pub active_state: ActiveState,
+    /// The crystallized state at this head block.
+    pub crystallized_state: CrystallizedState,
+    /// The configuration of the underlying chain.
+    pub config: ChainConfig,
 }
 
 impl ChainHead {
+    /// Initialize a new ChainHead with genesis parameters.
+    ///
+    /// Used when syncing a chain from scratch.
     pub fn genesis(
         initial_validator_entries: &[ValidatorRegistration],
         config: ChainConfig)
@@ -39,17 +49,11 @@ impl ChainHead {
          * Ignore any records which fail proof-of-possession or are invalid.
          */
         let validators = {
-            let mut validators = vec![];
-            let inductor = ValidatorInductor {
-                current_slot: 0,
-                shard_count: config.shard_count,
-                validators: &mut validators,
-                empty_validator_start: 0,
-            };
+            let mut inductor = ValidatorInductor::new(0, config.shard_count, vec![]);
             for registration in initial_validator_entries {
                 let _ = inductor.induct(&registration);
             };
-            validators
+            inductor.to_vec()
         };
 
         /*
@@ -58,9 +62,10 @@ impl ChainHead {
          * Crystallizedstate stores two cycles, so we simply repeat the same assignment twice.
          */
         let shard_and_committee_for_slots = {
-            let x = shard_and_committees_for_cycle(&vec![0; 32], &validators, 0, &config)?;
-            x.append(&mut x.clone());
-            x
+            let mut a = shard_and_committees_for_cycle(&vec![0; 32], &validators, 0, &config)?;
+            let mut b = a.clone();
+            a.append(&mut b);
+            a
         };
 
         /*
@@ -83,7 +88,7 @@ impl ChainHead {
          */
         let crystallized_state = CrystallizedState {
             validator_set_change_slot: 0,
-            validators,
+            validators: validators.to_vec(),
             crosslinks,
             last_state_recalculation_slot: 0,
             last_finalized_slot: 0,
@@ -97,6 +102,9 @@ impl ChainHead {
             fork_slot_number: 0,
         };
 
+        /*
+         * Set all recent block hashes to zero.
+         */
         let recent_block_hashes = {
             let mut x = vec![];
             for _ in 0..config.cycle_length {
@@ -105,6 +113,9 @@ impl ChainHead {
             x
         };
 
+        /*
+         * Create an active state.
+         */
         let active_state = ActiveState {
             pending_attestations: vec![],
             pending_specials: vec![],
@@ -114,6 +125,7 @@ impl ChainHead {
 
 
         Ok(Self {
+            head_hash: Hash256::zero(),
             active_state,
             crystallized_state,
             config,
diff --git a/beacon_chain/types/src/shard_and_committee.rs b/beacon_chain/types/src/shard_and_committee.rs
index 3b2bcd0fd..6cc74429a 100644
--- a/beacon_chain/types/src/shard_and_committee.rs
+++ b/beacon_chain/types/src/shard_and_committee.rs
@@ -1,4 +1,4 @@
-#[derive(Clone,Debug)]
+#[derive(Clone, Debug)]
 pub struct ShardAndCommittee {
     pub shard_id: u16,
     pub committee: Vec<usize>