From 549f9676f1e144d17927121f84ef9382ea3239ad Mon Sep 17 00:00:00 2001
From: Greg Fitzgerald <greg@solana.com>
Date: Tue, 5 Feb 2019 10:25:59 -0700
Subject: [PATCH] Allow validators to accumulate credits for voting

---
 programs/native/vote/src/lib.rs | 14 ++-------
 sdk/src/vote_program.rs         | 53 +++++++++++++++++++++++++++++----
 2 files changed, 49 insertions(+), 18 deletions(-)

diff --git a/programs/native/vote/src/lib.rs b/programs/native/vote/src/lib.rs
index 78c3d0e55..137fb8af0 100644
--- a/programs/native/vote/src/lib.rs
+++ b/programs/native/vote/src/lib.rs
@@ -39,19 +39,8 @@ fn process_vote(keyed_accounts: &mut [KeyedAccount], vote: Vote) -> Result<(), P
     }
 
     let mut vote_state = VoteState::deserialize(&keyed_accounts[0].account.userdata)?;
-
-    // TODO: Integrity checks
-    // a) Verify the vote's bank hash matches what is expected
-    // b) Verify vote is older than previous votes
-
-    // Only keep around the most recent MAX_VOTE_HISTORY votes
-    if vote_state.votes.len() == vote_program::MAX_VOTE_HISTORY {
-        vote_state.votes.pop_front();
-    }
-
-    vote_state.votes.push_back(vote);
+    vote_state.process_vote(vote);
     vote_state.serialize(&mut keyed_accounts[0].account.userdata)?;
-
     Ok(())
 }
 
@@ -152,6 +141,7 @@ mod tests {
         let vote = Vote::new(1);
         let vote_state = vote_and_deserialize(&vote_id, &mut vote_account, vote.clone()).unwrap();
         assert_eq!(vote_state.votes, vec![vote]);
+        assert_eq!(vote_state.credits(), 0);
     }
 
     #[test]
diff --git a/sdk/src/vote_program.rs b/sdk/src/vote_program.rs
index 2c2793cc9..3aa16e1c0 100644
--- a/sdk/src/vote_program.rs
+++ b/sdk/src/vote_program.rs
@@ -20,7 +20,7 @@ pub fn id() -> Pubkey {
 }
 
 // Maximum number of votes to keep around
-pub const MAX_VOTE_HISTORY: usize = 32;
+const MAX_VOTE_HISTORY: usize = 32;
 
 #[derive(Serialize, Default, Deserialize, Debug, PartialEq, Eq, Clone)]
 pub struct Vote {
@@ -51,6 +51,7 @@ pub struct VoteState {
     pub votes: VecDeque<Vote>,
     pub node_id: Pubkey,
     pub staker_id: Pubkey,
+    credits: u64,
 }
 
 pub fn get_max_size() -> usize {
@@ -64,10 +65,12 @@ pub fn get_max_size() -> usize {
 impl VoteState {
     pub fn new(node_id: Pubkey, staker_id: Pubkey) -> Self {
         let votes = VecDeque::new();
+        let credits = 0;
         Self {
             votes,
             node_id,
             staker_id,
+            credits,
         }
     }
 
@@ -81,6 +84,31 @@ impl VoteState {
             _ => ProgramError::GenericError,
         })
     }
+
+    pub fn process_vote(&mut self, vote: Vote) {
+        // TODO: Integrity checks
+        // a) Verify the vote's bank hash matches what is expected
+        // b) Verify vote is older than previous votes
+
+        // Only keep around the most recent MAX_VOTE_HISTORY votes
+        if self.votes.len() == MAX_VOTE_HISTORY {
+            self.votes.pop_front();
+            self.credits += 1;
+        }
+
+        self.votes.push_back(vote);
+    }
+
+    /// Number of "credits" owed to this account from the mining pool. Submit this
+    /// VoteState to the Rewards program to trade credits for lamports.
+    pub fn credits(&self) -> u64 {
+        self.credits
+    }
+
+    /// Clear any credits.
+    pub fn clear_credits(&mut self) {
+        self.credits = 0;
+    }
 }
 
 #[cfg(test)]
@@ -88,11 +116,24 @@ mod tests {
     use super::*;
 
     #[test]
-    fn test_serde() {
+    fn test_vote_serialize() {
         let mut buffer: Vec<u8> = vec![0; get_max_size()];
-        let mut vote_program = VoteState::default();
-        vote_program.votes = (0..MAX_VOTE_HISTORY).map(|_| Vote::default()).collect();
-        vote_program.serialize(&mut buffer).unwrap();
-        assert_eq!(VoteState::deserialize(&buffer).unwrap(), vote_program);
+        let mut vote_state = VoteState::default();
+        vote_state.votes.resize(MAX_VOTE_HISTORY, Vote::default());
+        vote_state.serialize(&mut buffer).unwrap();
+        assert_eq!(VoteState::deserialize(&buffer).unwrap(), vote_state);
+    }
+
+    #[test]
+    fn test_vote_credits() {
+        let mut vote_state = VoteState::default();
+        vote_state.votes.resize(MAX_VOTE_HISTORY, Vote::default());
+        assert_eq!(vote_state.credits(), 0);
+        vote_state.process_vote(Vote::new(42));
+        assert_eq!(vote_state.credits(), 1);
+        vote_state.process_vote(Vote::new(43));
+        assert_eq!(vote_state.credits(), 2);
+        vote_state.clear_credits();
+        assert_eq!(vote_state.credits(), 0);
     }
 }