Misc delegate flow refactor (#198)

Author: grod220

program/src/helpers/delegate.rs

@@ -1,13 +1,11 @@
 use {
-    crate::PERPETUAL_NEW_WARMUP_COOLDOWN_RATE_EPOCH,
     solana_account_info::AccountInfo,
     solana_clock::Epoch,
     solana_program_error::ProgramError,
     solana_pubkey::Pubkey,
     solana_stake_interface::{
         error::StakeError,
         state::{Delegation, Meta, Stake},
-        sysvar::stake_history::StakeHistorySysvar,
     },
 };
 
@@ -29,46 +27,6 @@ pub(crate) fn new_stake(
     }
 }
 
-pub(crate) fn redelegate_stake(
-    stake: &mut Stake,
-    stake_lamports: u64,
-    voter_pubkey: &Pubkey,
-    credits_observed: u64,
-    epoch: Epoch,
-    stake_history: &StakeHistorySysvar,
-) -> Result<(), ProgramError> {
-    // If stake is currently active:
-    if stake.stake(
-        epoch,
-        stake_history,
-        PERPETUAL_NEW_WARMUP_COOLDOWN_RATE_EPOCH,
-    ) != 0
-    {
-        // If pubkey of new voter is the same as current,
-        // and we are scheduled to start deactivating this epoch,
-        // we rescind deactivation
-        if stake.delegation.voter_pubkey == *voter_pubkey
-            && epoch == stake.delegation.deactivation_epoch
-        {
-            stake.delegation.deactivation_epoch = u64::MAX;
-            return Ok(());
-        } else {
-            // can't redelegate to another pubkey if stake is active.
-            return Err(StakeError::TooSoonToRedelegate.into());
-        }
-    }
-    // Either the stake is freshly activated, is active but has been
-    // deactivated this epoch, or has fully de-activated.
-    // Redelegation implies either re-activation or un-deactivation
-
-    stake.delegation.stake = stake_lamports;
-    stake.delegation.activation_epoch = epoch;
-    stake.delegation.deactivation_epoch = u64::MAX;
-    stake.delegation.voter_pubkey = *voter_pubkey;
-    stake.credits_observed = credits_observed;
-    Ok(())
-}
-
 /// Ensure the stake delegation amount is valid.  This checks that the account
 /// meets the minimum balance requirements of delegated stake.  If not, return
 /// an error.

program/src/processor.rs

@@ -404,22 +404,45 @@ impl Processor {
                 )
             }
             StakeStateV2::Stake(meta, mut stake, flags) => {
+                // Only the staker may (re)delegate
                 meta.authorized
                     .check(&signers, StakeAuthorize::Staker)
                     .map_err(to_program_error)?;
 
+                // Compute the maximum stake allowed to (re)delegate
                 let ValidatedDelegatedInfo { stake_amount } =
                     validate_delegated_amount(stake_account_info, &meta)?;
 
-                redelegate_stake(
-                    &mut stake,
-                    stake_amount,
-                    vote_account_info.key,
-                    vote_state.credits(),
+                // Get current activation status at this epoch
+                let effective_stake = stake.delegation.stake(
                     clock.epoch,
                     stake_history,
-                )?;
+                    PERPETUAL_NEW_WARMUP_COOLDOWN_RATE_EPOCH,
+                );
+
+                if effective_stake == 0 {
+                    // The stake has no effective voting power this epoch. This means it is either:
+                    //   1. Inactive (fully cooled down after a previous deactivation)
+                    //   2. Still activating (was delegated for the first time this epoch)
+                    stake = new_stake(
+                        stake_amount,
+                        vote_account_info.key,
+                        vote_state.credits(),
+                        clock.epoch,
+                    );
+                } else if clock.epoch == stake.delegation.deactivation_epoch
+                    && stake.delegation.voter_pubkey == *vote_account_info.key
+                {
+                    if stake_amount < stake.delegation.stake {
+                        return Err(StakeError::InsufficientDelegation.into());
+                    }
+                    stake.delegation.deactivation_epoch = u64::MAX;
+                } else {
+                    // Not a valid state for redelegation
+                    return Err(StakeError::TooSoonToRedelegate.into());
+                }
 
+                // Persist the updated stake state back to the account.
                 set_stake_state(stake_account_info, &StakeStateV2::Stake(meta, stake, flags))
             }
             _ => Err(ProgramError::InvalidAccountData),