Go object-oriented

Easy to imagine a trait here that's implemented using a Bank or
a testnet.

programs/native/rewards/tests/rewards.rs

@@ -8,73 +8,89 @@ use solana_sdk::signature::{Keypair, KeypairUtil};
 use solana_sdk::vote_program::{self, VoteState};
 use solana_sdk::vote_transaction::VoteTransaction;
 
-fn create_rewards_account(
-    bank: &Bank,
-    from_keypair: &Keypair,
-    rewards_id: Pubkey,
-    lamports: u64,
-) -> Result<()> {
-    let last_id = bank.last_id();
-    let tx = RewardsTransaction::new_account(from_keypair, rewards_id, last_id, lamports, 0);
-    bank.process_transaction(&tx)
+struct RewardsBank<'a> {
+    bank: &'a Bank,
 }
 
-fn create_vote_account(
-    bank: &Bank,
-    from_keypair: &Keypair,
-    vote_id: Pubkey,
-    lamports: u64,
-) -> Result<()> {
-    let last_id = bank.last_id();
-    let tx = VoteTransaction::new_account(from_keypair, vote_id, last_id, lamports, 0);
-    bank.process_transaction(&tx)
-}
+impl<'a> RewardsBank<'a> {
+    fn new(bank: &'a Bank) -> Self {
+        bank.add_native_program("solana_rewards_program", &rewards_program::id());
+        Self { bank }
+    }
 
-fn submit_vote(bank: &Bank, vote_keypair: &Keypair, tick_height: u64) -> Result<VoteState> {
-    let last_id = bank.last_id();
-    let tx = VoteTransaction::new_vote(vote_keypair, tick_height, last_id, 0);
-    bank.process_transaction(&tx)?;
-    bank.register_tick(&hash(last_id.as_ref()));
+    fn create_rewards_account(
+        &self,
+        from_keypair: &Keypair,
+        rewards_id: Pubkey,
+        lamports: u64,
+    ) -> Result<()> {
+        let last_id = self.bank.last_id();
+        let tx = RewardsTransaction::new_account(from_keypair, rewards_id, last_id, lamports, 0);
+        self.bank.process_transaction(&tx)
+    }
 
-    let vote_account = bank.get_account(&vote_keypair.pubkey()).unwrap();
-    Ok(VoteState::deserialize(&vote_account.userdata).unwrap())
-}
+    fn create_vote_account(
+        &self,
+        from_keypair: &Keypair,
+        vote_id: Pubkey,
+        lamports: u64,
+    ) -> Result<()> {
+        let last_id = self.bank.last_id();
+        let tx = VoteTransaction::new_account(from_keypair, vote_id, last_id, lamports, 0);
+        self.bank.process_transaction(&tx)
+    }
 
-fn redeem_credits(
-    bank: &Bank,
-    rewards_id: Pubkey,
-    vote_keypair: &Keypair,
-    to_id: Pubkey,
-) -> Result<VoteState> {
-    let last_id = bank.last_id();
-    let tx = RewardsTransaction::new_redeem_credits(&vote_keypair, rewards_id, to_id, last_id, 0);
-    bank.process_transaction(&tx)?;
-    let vote_account = bank.get_account(&vote_keypair.pubkey()).unwrap();
-    Ok(VoteState::deserialize(&vote_account.userdata).unwrap())
+    fn submit_vote(&self, vote_keypair: &Keypair, tick_height: u64) -> Result<VoteState> {
+        let last_id = self.bank.last_id();
+        let tx = VoteTransaction::new_vote(vote_keypair, tick_height, last_id, 0);
+        self.bank.process_transaction(&tx)?;
+        self.bank.register_tick(&hash(last_id.as_ref()));
+
+        let vote_account = self.bank.get_account(&vote_keypair.pubkey()).unwrap();
+        Ok(VoteState::deserialize(&vote_account.userdata).unwrap())
+    }
+
+    fn redeem_credits(
+        &self,
+        rewards_id: Pubkey,
+        vote_keypair: &Keypair,
+        to_id: Pubkey,
+    ) -> Result<VoteState> {
+        let last_id = self.bank.last_id();
+        let tx =
+            RewardsTransaction::new_redeem_credits(&vote_keypair, rewards_id, to_id, last_id, 0);
+        self.bank.process_transaction(&tx)?;
+        let vote_account = self.bank.get_account(&vote_keypair.pubkey()).unwrap();
+        Ok(VoteState::deserialize(&vote_account.userdata).unwrap())
+    }
 }
 
 #[test]
 fn test_redeem_vote_credits_via_bank() {
     let (genesis_block, from_keypair) = GenesisBlock::new(10_000);
     let bank = Bank::new(&genesis_block);
-    bank.add_native_program("solana_rewards_program", &rewards_program::id());
+    let rewards_bank = RewardsBank::new(&bank);
 
     // Create a rewards account to hold all rewards pool tokens.
     let rewards_keypair = Keypair::new();
     let rewards_id = rewards_keypair.pubkey();
-    create_rewards_account(&bank, &from_keypair, rewards_id, 100).unwrap();
+    rewards_bank
+        .create_rewards_account(&from_keypair, rewards_id, 100)
+        .unwrap();
 
     // A staker create a vote account account and delegates a validator to vote on its behalf.
     let vote_keypair = Keypair::new();
     let vote_id = vote_keypair.pubkey();
-    create_vote_account(&bank, &from_keypair, vote_id, 100).unwrap();
+    rewards_bank
+        .create_vote_account(&from_keypair, vote_id, 100)
+        .unwrap();
 
     // The validator submits votes to accumulate credits.
     for _ in 0..vote_program::MAX_VOTE_HISTORY {
-        let vote_state = submit_vote(&bank, &vote_keypair, 1).unwrap();
+        let vote_state = rewards_bank.submit_vote(&vote_keypair, 1).unwrap();
         assert_eq!(vote_state.credits(), 0);
     }
-    let vote_state = submit_vote(&bank, &vote_keypair, 1).unwrap();
+    let vote_state = rewards_bank.submit_vote(&vote_keypair, 1).unwrap();
     assert_eq!(vote_state.credits(), 1);
 
     // TODO: Add VoteInstruction::RegisterStakerId so that we don't need to point the "to"
@@ -84,7 +100,9 @@ fn test_redeem_vote_credits_via_bank() {
 
     // Periodically, the staker sumbits its vote account to the rewards pool
     // to exchange its credits for lamports.
-    let vote_state = redeem_credits(&bank, rewards_id, &vote_keypair, to_id).unwrap();
+    let vote_state = rewards_bank
+        .redeem_credits(rewards_id, &vote_keypair, to_id)
+        .unwrap();
     assert!(bank.get_balance(&to_id) > to_tokens);
     assert_eq!(vote_state.credits(), 0);
 }