From 3bca5e1d0f1d68841caeca20d9f736b324c7b377 Mon Sep 17 00:00:00 2001
From: Paul Hauner <paul@paulhauner.com>
Date: Tue, 17 Jul 2018 18:06:53 +1000
Subject: [PATCH] Implement initialize_new_epoch()

---
 src/state/transition/epoch.rs | 127 ++++++++++++++++++++++++++++++++++
 src/state/transition/mod.rs   |   1 +
 2 files changed, 128 insertions(+)
 create mode 100644 src/state/transition/epoch.rs

diff --git a/src/state/transition/epoch.rs b/src/state/transition/epoch.rs
new file mode 100644
index 0000000000..5d4c227968
--- /dev/null
+++ b/src/state/transition/epoch.rs
@@ -0,0 +1,127 @@
+use super::active_state::ActiveState;
+use super::crystallized_state::CrystallizedState;
+use super::validator_record::ValidatorRecord;
+use super::utils::types::{ Bitfield, U256, Sha256Digest };
+use super::config::Config;
+
+use super::deposits::process_ffg_deposits;
+use super::crosslinks::process_crosslinks;
+use super::attestors::process_recent_attesters;
+use super::proposers::process_recent_proposers;
+use super::validators::get_incremented_validator_sets;
+use super::shuffling::get_shuffling;
+
+pub fn initialize_new_epoch(
+    cry_state: &CrystallizedState,
+    act_state: &ActiveState,
+    config: &Config) 
+    -> (CrystallizedState, ActiveState)
+{
+    let mut new_validator_records: Vec<ValidatorRecord> = 
+        cry_state.active_validators.to_vec();
+    let ffg_voter_bitfield: Bitfield = 
+        act_state.ffg_voter_bitfield.clone();
+
+    let (ffg_deltas, _, _,
+         should_justify, should_finalize) = process_ffg_deposits (
+             &cry_state,
+             &ffg_voter_bitfield);
+
+    let (crosslink_notaries_deltas, new_crosslinks) = 
+        process_crosslinks(
+            &cry_state,
+            &act_state.partial_crosslinks,
+            &config);
+
+    let recent_attesters_deltas = process_recent_attesters(
+        &cry_state,
+        &act_state.recent_attesters,
+        &config);
+
+    let recent_proposers_deltas = process_recent_proposers(
+        &cry_state,
+        &act_state.recent_proposers);
+
+    for (i, validator) in new_validator_records.iter_mut().enumerate() {
+        let balance: i64 = 
+            validator.balance.low_u64() as i64 +
+            ffg_deltas[i] + 
+            crosslink_notaries_deltas[i] +
+            recent_attesters_deltas[i] +
+            recent_proposers_deltas[i];
+        if balance > 0 {
+            validator.balance = U256::from(balance as u64);
+        } else {
+            validator.balance = U256::zero();
+        }
+    }
+   
+    let deposit_sum: i64 = 
+        ffg_deltas.iter().sum::<i64>() + 
+        crosslink_notaries_deltas.iter().sum::<i64>() +
+        recent_attesters_deltas.iter().sum::<i64>() +
+        recent_proposers_deltas.iter().sum::<i64>();
+
+    let total_deposits: U256 = match deposit_sum > 0 {
+        true => U256::from(deposit_sum as u64),
+        false => U256::zero()
+    };
+
+    let last_justified_epoch = match should_justify {
+        true => cry_state.current_epoch,
+        false => cry_state.last_justified_epoch
+    };
+
+    let (last_finalized_epoch, dynasty) = match should_finalize {
+        true => (cry_state.current_epoch - 1, cry_state.dynasty + 1),
+        false => (cry_state.last_finalized_epoch, cry_state.dynasty)
+    };
+
+    let (new_queued_validators, new_active_validators, new_exited_validators) =
+        match should_finalize 
+    {
+        true => get_incremented_validator_sets(
+            &cry_state,
+            &new_validator_records,
+            &config),
+        false => (cry_state.queued_validators.to_vec(), 
+                  cry_state.active_validators.to_vec(),
+                  cry_state.exited_validators.to_vec())
+    };
+
+    let shuffling = get_shuffling(
+        &act_state.randao,
+        &new_active_validators.len(),
+        &config);
+
+    let new_cry_state = CrystallizedState {
+        active_validators: new_active_validators,
+        queued_validators: new_queued_validators,
+        exited_validators: new_exited_validators,
+        current_shuffling: shuffling,
+        current_epoch: cry_state.current_epoch + 1,
+        last_justified_epoch,
+        last_finalized_epoch,
+        dynasty,
+        // TODO: why is this zero?
+        next_shard: 0,
+        // TODO: currenct checkpoint wasnt in reference implementation
+        current_checkpoint: Sha256Digest::zero(),
+        crosslink_records: new_crosslinks,
+        total_deposits
+    };
+
+    let new_act_state = ActiveState {
+        height: act_state.height,
+        randao: act_state.randao,
+        ffg_voter_bitfield: Bitfield::new(),
+        recent_attesters: vec![],
+        partial_crosslinks: vec![],
+        total_skip_count: act_state.total_skip_count,
+        recent_proposers: vec![]
+    };
+
+    (new_cry_state, new_act_state)
+}
+
+
diff --git a/src/state/transition/mod.rs b/src/state/transition/mod.rs
index 52a1712049..391752ffda 100644
--- a/src/state/transition/mod.rs
+++ b/src/state/transition/mod.rs
@@ -11,6 +11,7 @@ use super::validator_record;
 
 pub mod crosslinks;
 pub mod deposits;
+pub mod epoch;
 pub mod ffg;
 pub mod proposers;
 pub mod shuffling;