solana_stake_program/

stake_state.rs

//! Stake state
//! * delegate stakes to vote accounts
//! * keep track of rewards
//! * own mining pools

#[deprecated(
    since = "1.8.0",
    note = "Please use `solana_sdk::stake::state` or `solana_program::stake::state` instead"
)]
pub use solana_sdk::stake::state::*;
use {
    solana_program_runtime::{ic_msg, invoke_context::InvokeContext},
    solana_sdk::{
        account::{AccountSharedData, ReadableAccount, WritableAccount},
        account_utils::StateMut,
        clock::{Clock, Epoch},
        feature_set::{
            self, stake_allow_zero_undelegated_amount, stake_merge_with_unmatched_credits_observed,
            stake_split_uses_rent_sysvar, FeatureSet,
        },
        instruction::{checked_add, InstructionError},
        pubkey::Pubkey,
        rent::{Rent, ACCOUNT_STORAGE_OVERHEAD},
        stake::{
            config::Config,
            instruction::{LockupArgs, StakeError},
            program::id,
            tools::{acceptable_reference_epoch_credits, eligible_for_deactivate_delinquent},
        },
        stake_history::{StakeHistory, StakeHistoryEntry},
        transaction_context::{BorrowedAccount, InstructionContext, TransactionContext},
    },
    solana_vote_program::vote_state::{VoteState, VoteStateVersions},
    std::{collections::HashSet, convert::TryFrom},
};

#[derive(Debug)]
pub enum SkippedReason {
    DisabledInflation,
    JustActivated,
    TooEarlyUnfairSplit,
    ZeroPoints,
    ZeroPointValue,
    ZeroReward,
    ZeroCreditsAndReturnZero,
    ZeroCreditsAndReturnCurrent,
    ZeroCreditsAndReturnRewinded,
}

impl From<SkippedReason> for InflationPointCalculationEvent {
    fn from(reason: SkippedReason) -> Self {
        InflationPointCalculationEvent::Skipped(reason)
    }
}

#[derive(Debug)]
pub enum InflationPointCalculationEvent {
    CalculatedPoints(u64, u128, u128, u128),
    SplitRewards(u64, u64, u64, PointValue),
    EffectiveStakeAtRewardedEpoch(u64),
    RentExemptReserve(u64),
    Delegation(Delegation, Pubkey),
    Commission(u8),
    CreditsObserved(u64, Option<u64>),
    Skipped(SkippedReason),
}

pub(crate) fn null_tracer() -> Option<impl Fn(&InflationPointCalculationEvent)> {
    None::<fn(&_)>
}

// utility function, used by Stakes, tests
pub fn from<T: ReadableAccount + StateMut<StakeState>>(account: &T) -> Option<StakeState> {
    account.state().ok()
}

pub fn stake_from<T: ReadableAccount + StateMut<StakeState>>(account: &T) -> Option<Stake> {
    from(account).and_then(|state: StakeState| state.stake())
}

pub fn delegation_from(account: &AccountSharedData) -> Option<Delegation> {
    from(account).and_then(|state: StakeState| state.delegation())
}

pub fn authorized_from(account: &AccountSharedData) -> Option<Authorized> {
    from(account).and_then(|state: StakeState| state.authorized())
}

pub fn lockup_from<T: ReadableAccount + StateMut<StakeState>>(account: &T) -> Option<Lockup> {
    from(account).and_then(|state: StakeState| state.lockup())
}

pub fn meta_from(account: &AccountSharedData) -> Option<Meta> {
    from(account).and_then(|state: StakeState| state.meta())
}

fn redelegate_stake(
    invoke_context: &InvokeContext,
    stake: &mut Stake,
    stake_lamports: u64,
    voter_pubkey: &Pubkey,
    vote_state: &VoteState,
    clock: &Clock,
    stake_history: &StakeHistory,
    config: &Config,
) -> Result<(), StakeError> {
    // If stake is currently active:
    if stake.stake(clock.epoch, Some(stake_history)) != 0 {
        let stake_lamports_ok = if invoke_context
            .feature_set
            .is_active(&feature_set::stake_redelegate_instruction::id())
        {
            // When a stake account is redelegated, the delegated lamports from the source stake
            // account are transferred to a new stake account. Do not permit the deactivation of
            // the source stake account to be rescinded, by more generally requiring the delegation
            // be configured with the expected amount of stake lamports before rescinding.
            stake_lamports >= stake.delegation.stake
        } else {
            true
        };

        // 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
            && clock.epoch == stake.delegation.deactivation_epoch
            && stake_lamports_ok
        {
            stake.delegation.deactivation_epoch = std::u64::MAX;
            return Ok(());
        } else {
            // can't redelegate to another pubkey if stake is active.
            return Err(StakeError::TooSoonToRedelegate);
        }
    }
    // 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 = clock.epoch;
    stake.delegation.deactivation_epoch = std::u64::MAX;
    stake.delegation.voter_pubkey = *voter_pubkey;
    stake.delegation.warmup_cooldown_rate = config.warmup_cooldown_rate;
    stake.credits_observed = vote_state.credits();
    Ok(())
}

pub(crate) fn new_stake(
    stake: u64,
    voter_pubkey: &Pubkey,
    vote_state: &VoteState,
    activation_epoch: Epoch,
    config: &Config,
) -> Stake {
    Stake {
        delegation: Delegation::new(
            voter_pubkey,
            stake,
            activation_epoch,
            config.warmup_cooldown_rate,
        ),
        credits_observed: vote_state.credits(),
    }
}

/// captures a rewards round as lamports to be awarded
///  and the total points over which those lamports
///  are to be distributed
//  basically read as rewards/points, but in integers instead of as an f64
#[derive(Clone, Debug, PartialEq, Eq)]
pub struct PointValue {
    pub rewards: u64, // lamports to split
    pub points: u128, // over these points
}

fn redeem_stake_rewards(
    rewarded_epoch: Epoch,
    stake: &mut Stake,
    point_value: &PointValue,
    vote_state: &VoteState,
    stake_history: Option<&StakeHistory>,
    inflation_point_calc_tracer: Option<impl Fn(&InflationPointCalculationEvent)>,
    credits_auto_rewind: bool,
) -> Option<(u64, u64)> {
    if let Some(inflation_point_calc_tracer) = inflation_point_calc_tracer.as_ref() {
        inflation_point_calc_tracer(&InflationPointCalculationEvent::CreditsObserved(
            stake.credits_observed,
            None,
        ));
    }
    calculate_stake_rewards(
        rewarded_epoch,
        stake,
        point_value,
        vote_state,
        stake_history,
        inflation_point_calc_tracer.as_ref(),
        credits_auto_rewind,
    )
    .map(|calculated_stake_rewards| {
        if let Some(inflation_point_calc_tracer) = inflation_point_calc_tracer {
            inflation_point_calc_tracer(&InflationPointCalculationEvent::CreditsObserved(
                stake.credits_observed,
                Some(calculated_stake_rewards.new_credits_observed),
            ));
        }
        stake.credits_observed = calculated_stake_rewards.new_credits_observed;
        stake.delegation.stake += calculated_stake_rewards.staker_rewards;
        (
            calculated_stake_rewards.staker_rewards,
            calculated_stake_rewards.voter_rewards,
        )
    })
}

fn calculate_stake_points(
    stake: &Stake,
    vote_state: &VoteState,
    stake_history: Option<&StakeHistory>,
    inflation_point_calc_tracer: Option<impl Fn(&InflationPointCalculationEvent)>,
) -> u128 {
    calculate_stake_points_and_credits(
        stake,
        vote_state,
        stake_history,
        inflation_point_calc_tracer,
        true, // this is safe because this flag shouldn't affect the
              // `points` field of the returned struct in any way
    )
    .points
}

#[derive(Debug, PartialEq, Eq)]
struct CalculatedStakePoints {
    points: u128,
    new_credits_observed: u64,
    force_credits_update_with_skipped_reward: bool,
}

/// for a given stake and vote_state, calculate how many
///   points were earned (credits * stake) and new value
///   for credits_observed were the points paid
fn calculate_stake_points_and_credits(
    stake: &Stake,
    new_vote_state: &VoteState,
    stake_history: Option<&StakeHistory>,
    inflation_point_calc_tracer: Option<impl Fn(&InflationPointCalculationEvent)>,
    credits_auto_rewind: bool,
) -> CalculatedStakePoints {
    let credits_in_stake = stake.credits_observed;
    let credits_in_vote = new_vote_state.credits();
    // if there is no newer credits since observed, return no point
    if credits_in_vote <= credits_in_stake {
        if credits_auto_rewind && credits_in_vote < credits_in_stake {
            if let Some(inflation_point_calc_tracer) = inflation_point_calc_tracer.as_ref() {
                inflation_point_calc_tracer(&SkippedReason::ZeroCreditsAndReturnRewinded.into());
            }
            // Don't adjust stake.activation_epoch for simplicity:
            //  - generally fast-forwarding stake.activation_epoch forcibly (for
            //    artificial re-activation with re-warm-up) skews the stake
            //    history sysvar. And properly handling all the cases
            //    regarding deactivation epoch/warm-up/cool-down without
            //    introducing incentive skew is hard.
            //  - Conceptually, it should be acceptable for the staked SAFEs at
            //    the recreated vote to receive rewards again immediately after
            //    rewind even if it looks like instant activation. That's
            //    because it must have passed the required warmed-up at least
            //    once in the past already
            //  - Also such a stake account remains to be a part of overall
            //    effective stake calculation even while the vote account is
            //    missing for (indefinite) time or remains to be pre-remove
            //    credits score. It should be treated equally to staking with
            //    delinquent validator with no differentiation.

            // hint with true to indicate some exceptional credits handling is needed
            return CalculatedStakePoints {
                points: 0,
                new_credits_observed: credits_in_vote,
                force_credits_update_with_skipped_reward: true,
            };
        } else {
            // change the above `else` to `else if credits_in_vote == credits_in_stake`
            // (and remove the outermost enclosing `if`) when cleaning credits_auto_rewind
            // after activation

            if let Some(inflation_point_calc_tracer) = inflation_point_calc_tracer.as_ref() {
                inflation_point_calc_tracer(&SkippedReason::ZeroCreditsAndReturnCurrent.into());
            }
            // don't hint the caller and return current value if credits_auto_rewind is off or
            // credits remain to be unchanged (= delinquent)
            return CalculatedStakePoints {
                points: 0,
                new_credits_observed: credits_in_stake,
                force_credits_update_with_skipped_reward: false,
            };
        };
    }

    let mut points = 0;
    let mut new_credits_observed = credits_in_stake;

    for (epoch, final_epoch_credits, initial_epoch_credits) in
        new_vote_state.epoch_credits().iter().copied()
    {
        let stake_amount = u128::from(stake.delegation.stake(epoch, stake_history));

        // figure out how much this stake has seen that
        //   for which the vote account has a record
        let earned_credits = if credits_in_stake < initial_epoch_credits {
            // the staker observed the entire epoch
            final_epoch_credits - initial_epoch_credits
        } else if credits_in_stake < final_epoch_credits {
            // the staker registered sometime during the epoch, partial credit
            final_epoch_credits - new_credits_observed
        } else {
            // the staker has already observed or been redeemed this epoch
            //  or was activated after this epoch
            0
        };
        let earned_credits = u128::from(earned_credits);

        // don't want to assume anything about order of the iterator...
        new_credits_observed = new_credits_observed.max(final_epoch_credits);

        // finally calculate points for this epoch
        let earned_points = stake_amount * earned_credits;
        points += earned_points;

        if let Some(inflation_point_calc_tracer) = inflation_point_calc_tracer.as_ref() {
            inflation_point_calc_tracer(&InflationPointCalculationEvent::CalculatedPoints(
                epoch,
                stake_amount,
                earned_credits,
                earned_points,
            ));
        }
    }

    CalculatedStakePoints {
        points,
        new_credits_observed,
        force_credits_update_with_skipped_reward: false,
    }
}

#[derive(Debug, PartialEq, Eq)]
struct CalculatedStakeRewards {
    staker_rewards: u64,
    voter_rewards: u64,
    new_credits_observed: u64,
}

/// for a given stake and vote_state, calculate what distributions and what updates should be made
/// returns a tuple in the case of a payout of:
///   * staker_rewards to be distributed
///   * voter_rewards to be distributed
///   * new value for credits_observed in the stake
/// returns None if there's no payout or if any deserved payout is < 1 lamport
fn calculate_stake_rewards(
    rewarded_epoch: Epoch,
    stake: &Stake,
    point_value: &PointValue,
    vote_state: &VoteState,
    stake_history: Option<&StakeHistory>,
    inflation_point_calc_tracer: Option<impl Fn(&InflationPointCalculationEvent)>,
    credits_auto_rewind: bool,
) -> Option<CalculatedStakeRewards> {
    // ensure to run to trigger (optional) inflation_point_calc_tracer
    let CalculatedStakePoints {
        points,
        new_credits_observed,
        mut force_credits_update_with_skipped_reward,
    } = calculate_stake_points_and_credits(
        stake,
        vote_state,
        stake_history,
        inflation_point_calc_tracer.as_ref(),
        credits_auto_rewind,
    );

    // Drive credits_observed forward unconditionally when rewards are disabled
    // or when this is the stake's activation epoch
    if point_value.rewards == 0 {
        if let Some(inflation_point_calc_tracer) = inflation_point_calc_tracer.as_ref() {
            inflation_point_calc_tracer(&SkippedReason::DisabledInflation.into());
        }
        force_credits_update_with_skipped_reward = true;
    } else if stake.delegation.activation_epoch == rewarded_epoch {
        // not assert!()-ed; but points should be zero
        if let Some(inflation_point_calc_tracer) = inflation_point_calc_tracer.as_ref() {
            inflation_point_calc_tracer(&SkippedReason::JustActivated.into());
        }
        force_credits_update_with_skipped_reward = true;
    }

    if force_credits_update_with_skipped_reward {
        return Some(CalculatedStakeRewards {
            staker_rewards: 0,
            voter_rewards: 0,
            new_credits_observed,
        });
    }

    if points == 0 {
        if let Some(inflation_point_calc_tracer) = inflation_point_calc_tracer.as_ref() {
            inflation_point_calc_tracer(&SkippedReason::ZeroPoints.into());
        }
        return None;
    }
    if point_value.points == 0 {
        if let Some(inflation_point_calc_tracer) = inflation_point_calc_tracer.as_ref() {
            inflation_point_calc_tracer(&SkippedReason::ZeroPointValue.into());
        }
        return None;
    }

    let rewards = points
        .checked_mul(u128::from(point_value.rewards))
        .unwrap()
        .checked_div(point_value.points)
        .unwrap();

    let rewards = u64::try_from(rewards).unwrap();

    // don't bother trying to split if fractional lamports got truncated
    if rewards == 0 {
        if let Some(inflation_point_calc_tracer) = inflation_point_calc_tracer.as_ref() {
            inflation_point_calc_tracer(&SkippedReason::ZeroReward.into());
        }
        return None;
    }
    let (voter_rewards, staker_rewards, is_split) = vote_state.commission_split(rewards);
    if let Some(inflation_point_calc_tracer) = inflation_point_calc_tracer.as_ref() {
        inflation_point_calc_tracer(&InflationPointCalculationEvent::SplitRewards(
            rewards,
            voter_rewards,
            staker_rewards,
            (*point_value).clone(),
        ));
    }

    if (voter_rewards == 0 || staker_rewards == 0) && is_split {
        // don't collect if we lose a whole lamport somewhere
        //  is_split means there should be tokens on both sides,
        //  uncool to move credits_observed if one side didn't get paid
        if let Some(inflation_point_calc_tracer) = inflation_point_calc_tracer.as_ref() {
            inflation_point_calc_tracer(&SkippedReason::TooEarlyUnfairSplit.into());
        }
        return None;
    }

    Some(CalculatedStakeRewards {
        staker_rewards,
        voter_rewards,
        new_credits_observed,
    })
}

pub fn initialize(
    stake_account: &mut BorrowedAccount,
    authorized: &Authorized,
    lockup: &Lockup,
    rent: &Rent,
    feature_set: &FeatureSet,
) -> Result<(), InstructionError> {
    if stake_account.get_data().len() != StakeState::size_of() {
        return Err(InstructionError::InvalidAccountData);
    }
    if let StakeState::Uninitialized = stake_account.get_state()? {
        let rent_exempt_reserve = rent.minimum_balance(stake_account.get_data().len());
        // when removing this feature, remove `minimum_balance` and just use `rent_exempt_reserve`
        let minimum_balance = if feature_set.is_active(&stake_allow_zero_undelegated_amount::id()) {
            rent_exempt_reserve
        } else {
            let minimum_delegation = crate::get_minimum_delegation(feature_set);
            rent_exempt_reserve + minimum_delegation
        };

        if stake_account.get_lamports() >= minimum_balance {
            stake_account.set_state(&StakeState::Initialized(Meta {
                rent_exempt_reserve,
                authorized: *authorized,
                lockup: *lockup,
            }))
        } else {
            Err(InstructionError::InsufficientFunds)
        }
    } else {
        Err(InstructionError::InvalidAccountData)
    }
}

/// Authorize the given pubkey to manage stake (deactivate, withdraw). This may be called
/// multiple times, but will implicitly withdraw authorization from the previously authorized
/// staker. The default staker is the owner of the stake account's pubkey.
pub fn authorize(
    stake_account: &mut BorrowedAccount,
    signers: &HashSet<Pubkey>,
    new_authority: &Pubkey,
    stake_authorize: StakeAuthorize,
    require_custodian_for_locked_stake_authorize: bool,
    clock: &Clock,
    custodian: Option<&Pubkey>,
) -> Result<(), InstructionError> {
    match stake_account.get_state()? {
        StakeState::Stake(mut meta, stake) => {
            meta.authorized.authorize(
                signers,
                new_authority,
                stake_authorize,
                if require_custodian_for_locked_stake_authorize {
                    Some((&meta.lockup, clock, custodian))
                } else {
                    None
                },
            )?;
            stake_account.set_state(&StakeState::Stake(meta, stake))
        }
        StakeState::Initialized(mut meta) => {
            meta.authorized.authorize(
                signers,
                new_authority,
                stake_authorize,
                if require_custodian_for_locked_stake_authorize {
                    Some((&meta.lockup, clock, custodian))
                } else {
                    None
                },
            )?;
            stake_account.set_state(&StakeState::Initialized(meta))
        }
        _ => Err(InstructionError::InvalidAccountData),
    }
}

#[allow(clippy::too_many_arguments)]
pub fn authorize_with_seed(
    transaction_context: &TransactionContext,
    instruction_context: &InstructionContext,
    stake_account: &mut BorrowedAccount,
    authority_base_index: usize,
    authority_seed: &str,
    authority_owner: &Pubkey,
    new_authority: &Pubkey,
    stake_authorize: StakeAuthorize,
    require_custodian_for_locked_stake_authorize: bool,
    clock: &Clock,
    custodian: Option<&Pubkey>,
) -> Result<(), InstructionError> {
    let mut signers = HashSet::default();
    if instruction_context.is_instruction_account_signer(authority_base_index)? {
        let base_pubkey = transaction_context.get_key_of_account_at_index(
            instruction_context
                .get_index_of_instruction_account_in_transaction(authority_base_index)?,
        )?;
        signers.insert(Pubkey::create_with_seed(
            base_pubkey,
            authority_seed,
            authority_owner,
        )?);
    }
    authorize(
        stake_account,
        &signers,
        new_authority,
        stake_authorize,
        require_custodian_for_locked_stake_authorize,
        clock,
        custodian,
    )
}

#[allow(clippy::too_many_arguments)]
pub fn delegate(
    invoke_context: &InvokeContext,
    transaction_context: &TransactionContext,
    instruction_context: &InstructionContext,
    stake_account_index: usize,
    vote_account_index: usize,
    clock: &Clock,
    stake_history: &StakeHistory,
    config: &Config,
    signers: &HashSet<Pubkey>,
    feature_set: &FeatureSet,
) -> Result<(), InstructionError> {
    let vote_account = instruction_context
        .try_borrow_instruction_account(transaction_context, vote_account_index)?;
    if *vote_account.get_owner() != solana_vote_program::id() {
        return Err(InstructionError::IncorrectProgramId);
    }
    let vote_pubkey = *vote_account.get_key();
    let vote_state = vote_account.get_state::<VoteStateVersions>();
    drop(vote_account);

    let mut stake_account = instruction_context
        .try_borrow_instruction_account(transaction_context, stake_account_index)?;
    match stake_account.get_state()? {
        StakeState::Initialized(meta) => {
            meta.authorized.check(signers, StakeAuthorize::Staker)?;
            let ValidatedDelegatedInfo { stake_amount } =
                validate_delegated_amount(&stake_account, &meta, feature_set)?;
            let stake = new_stake(
                stake_amount,
                &vote_pubkey,
                &vote_state?.convert_to_current(),
                clock.epoch,
                config,
            );
            stake_account.set_state(&StakeState::Stake(meta, stake))
        }
        StakeState::Stake(meta, mut stake) => {
            meta.authorized.check(signers, StakeAuthorize::Staker)?;
            let ValidatedDelegatedInfo { stake_amount } =
                validate_delegated_amount(&stake_account, &meta, feature_set)?;
            redelegate_stake(
                invoke_context,
                &mut stake,
                stake_amount,
                &vote_pubkey,
                &vote_state?.convert_to_current(),
                clock,
                stake_history,
                config,
            )?;
            stake_account.set_state(&StakeState::Stake(meta, stake))
        }
        _ => Err(InstructionError::InvalidAccountData),
    }
}

pub fn deactivate(
    stake_account: &mut BorrowedAccount,
    clock: &Clock,
    signers: &HashSet<Pubkey>,
) -> Result<(), InstructionError> {
    if let StakeState::Stake(meta, mut stake) = stake_account.get_state()? {
        meta.authorized.check(signers, StakeAuthorize::Staker)?;
        stake.deactivate(clock.epoch)?;

        stake_account.set_state(&StakeState::Stake(meta, stake))
    } else {
        Err(InstructionError::InvalidAccountData)
    }
}

pub fn set_lockup(
    stake_account: &mut BorrowedAccount,
    lockup: &LockupArgs,
    signers: &HashSet<Pubkey>,
    clock: &Clock,
) -> Result<(), InstructionError> {
    match stake_account.get_state()? {
        StakeState::Initialized(mut meta) => {
            meta.set_lockup(lockup, signers, clock)?;
            stake_account.set_state(&StakeState::Initialized(meta))
        }
        StakeState::Stake(mut meta, stake) => {
            meta.set_lockup(lockup, signers, clock)?;
            stake_account.set_state(&StakeState::Stake(meta, stake))
        }
        _ => Err(InstructionError::InvalidAccountData),
    }
}

pub fn split(
    invoke_context: &InvokeContext,
    transaction_context: &TransactionContext,
    instruction_context: &InstructionContext,
    stake_account_index: usize,
    lamports: u64,
    split_index: usize,
    signers: &HashSet<Pubkey>,
) -> Result<(), InstructionError> {
    let split =
        instruction_context.try_borrow_instruction_account(transaction_context, split_index)?;
    if *split.get_owner() != id() {
        return Err(InstructionError::IncorrectProgramId);
    }
    if split.get_data().len() != StakeState::size_of() {
        return Err(InstructionError::InvalidAccountData);
    }
    if !matches!(split.get_state()?, StakeState::Uninitialized) {
        return Err(InstructionError::InvalidAccountData);
    }
    let split_lamport_balance = split.get_lamports();
    drop(split);
    let stake_account = instruction_context
        .try_borrow_instruction_account(transaction_context, stake_account_index)?;
    if lamports > stake_account.get_lamports() {
        return Err(InstructionError::InsufficientFunds);
    }
    let stake_state = stake_account.get_state()?;
    drop(stake_account);

    match stake_state {
        StakeState::Stake(meta, mut stake) => {
            meta.authorized.check(signers, StakeAuthorize::Staker)?;
            let minimum_delegation = crate::get_minimum_delegation(&invoke_context.feature_set);
            let validated_split_info = validate_split_amount(
                invoke_context,
                transaction_context,
                instruction_context,
                stake_account_index,
                split_index,
                lamports,
                &meta,
                Some(&stake),
                minimum_delegation,
            )?;

            // split the stake, subtract rent_exempt_balance unless
            // the destination account already has those lamports
            // in place.
            // this means that the new stake account will have a stake equivalent to
            // lamports minus rent_exempt_reserve if it starts out with a zero balance
            let (remaining_stake_delta, split_stake_amount) =
                if validated_split_info.source_remaining_balance == 0 {
                    // If split amount equals the full source stake (as implied by 0
                    // source_remaining_balance), the new split stake must equal the same
                    // amount, regardless of any current lamport balance in the split account.
                    // Since split accounts retain the state of their source account, this
                    // prevents any magic activation of stake by prefunding the split account.
                    //
                    // The new split stake also needs to ignore any positive delta between the
                    // original rent_exempt_reserve and the split_rent_exempt_reserve, in order
                    // to prevent magic activation of stake by splitting between accounts of
                    // different sizes.
                    let remaining_stake_delta = lamports.saturating_sub(meta.rent_exempt_reserve);
                    (remaining_stake_delta, remaining_stake_delta)
                } else {
                    // Otherwise, the new split stake should reflect the entire split
                    // requested, less any lamports needed to cover the split_rent_exempt_reserve.
                    (
                        lamports,
                        lamports.saturating_sub(
                            validated_split_info
                                .destination_rent_exempt_reserve
                                .saturating_sub(split_lamport_balance),
                        ),
                    )
                };
            let split_stake = stake.split(remaining_stake_delta, split_stake_amount)?;
            let mut split_meta = meta;
            split_meta.rent_exempt_reserve = validated_split_info.destination_rent_exempt_reserve;

            let mut stake_account = instruction_context
                .try_borrow_instruction_account(transaction_context, stake_account_index)?;
            stake_account.set_state(&StakeState::Stake(meta, stake))?;
            drop(stake_account);
            let mut split = instruction_context
                .try_borrow_instruction_account(transaction_context, split_index)?;
            split.set_state(&StakeState::Stake(split_meta, split_stake))?;
        }
        StakeState::Initialized(meta) => {
            meta.authorized.check(signers, StakeAuthorize::Staker)?;
            let additional_required_lamports = if invoke_context
                .feature_set
                .is_active(&stake_allow_zero_undelegated_amount::id())
            {
                0
            } else {
                crate::get_minimum_delegation(&invoke_context.feature_set)
            };
            let validated_split_info = validate_split_amount(
                invoke_context,
                transaction_context,
                instruction_context,
                stake_account_index,
                split_index,
                lamports,
                &meta,
                None,
                additional_required_lamports,
            )?;
            let mut split_meta = meta;
            split_meta.rent_exempt_reserve = validated_split_info.destination_rent_exempt_reserve;
            let mut split = instruction_context
                .try_borrow_instruction_account(transaction_context, split_index)?;
            split.set_state(&StakeState::Initialized(split_meta))?;
        }
        StakeState::Uninitialized => {
            let stake_pubkey = transaction_context.get_key_of_account_at_index(
                instruction_context
                    .get_index_of_instruction_account_in_transaction(stake_account_index)?,
            )?;
            if !signers.contains(stake_pubkey) {
                return Err(InstructionError::MissingRequiredSignature);
            }
        }
        _ => return Err(InstructionError::InvalidAccountData),
    }

    // Deinitialize state upon zero balance
    let mut stake_account = instruction_context
        .try_borrow_instruction_account(transaction_context, stake_account_index)?;
    if lamports == stake_account.get_lamports() {
        stake_account.set_state(&StakeState::Uninitialized)?;
    }
    drop(stake_account);

    let mut split =
        instruction_context.try_borrow_instruction_account(transaction_context, split_index)?;
    split.checked_add_lamports(lamports)?;
    drop(split);
    let mut stake_account = instruction_context
        .try_borrow_instruction_account(transaction_context, stake_account_index)?;
    stake_account.checked_sub_lamports(lamports)?;
    Ok(())
}

pub fn merge(
    invoke_context: &InvokeContext,
    transaction_context: &TransactionContext,
    instruction_context: &InstructionContext,
    stake_account_index: usize,
    source_account_index: usize,
    clock: &Clock,
    stake_history: &StakeHistory,
    signers: &HashSet<Pubkey>,
) -> Result<(), InstructionError> {
    let mut source_account = instruction_context
        .try_borrow_instruction_account(transaction_context, source_account_index)?;
    // Ensure source isn't spoofed
    if *source_account.get_owner() != id() {
        return Err(InstructionError::IncorrectProgramId);
    }
    // Close the stake_account-reference loophole
    if instruction_context.get_index_of_instruction_account_in_transaction(stake_account_index)?
        == instruction_context
            .get_index_of_instruction_account_in_transaction(source_account_index)?
    {
        return Err(InstructionError::InvalidArgument);
    }
    let mut stake_account = instruction_context
        .try_borrow_instruction_account(transaction_context, stake_account_index)?;

    ic_msg!(invoke_context, "Checking if destination stake is mergeable");
    let stake_merge_kind = MergeKind::get_if_mergeable(
        invoke_context,
        &stake_account.get_state()?,
        stake_account.get_lamports(),
        clock,
        stake_history,
    )?;

    // Authorized staker is allowed to split/merge accounts
    stake_merge_kind
        .meta()
        .authorized
        .check(signers, StakeAuthorize::Staker)?;

    ic_msg!(invoke_context, "Checking if source stake is mergeable");
    let source_merge_kind = MergeKind::get_if_mergeable(
        invoke_context,
        &source_account.get_state()?,
        source_account.get_lamports(),
        clock,
        stake_history,
    )?;

    ic_msg!(invoke_context, "Merging stake accounts");
    if let Some(merged_state) = stake_merge_kind.merge(invoke_context, source_merge_kind, clock)? {
        stake_account.set_state(&merged_state)?;
    }

    // Source is about to be drained, deinitialize its state
    source_account.set_state(&StakeState::Uninitialized)?;

    // Drain the source stake account
    let lamports = source_account.get_lamports();
    source_account.checked_sub_lamports(lamports)?;
    stake_account.checked_add_lamports(lamports)?;
    Ok(())
}

pub fn redelegate(
    invoke_context: &InvokeContext,
    transaction_context: &TransactionContext,
    instruction_context: &InstructionContext,
    stake_account: &mut BorrowedAccount,
    uninitialized_stake_account_index: usize,
    vote_account_index: usize,
    config: &Config,
    signers: &HashSet<Pubkey>,
) -> Result<(), InstructionError> {
    let clock = invoke_context.get_sysvar_cache().get_clock()?;

    // ensure `uninitialized_stake_account_index` is in the uninitialized state
    let mut uninitialized_stake_account = instruction_context
        .try_borrow_instruction_account(transaction_context, uninitialized_stake_account_index)?;
    if *uninitialized_stake_account.get_owner() != id() {
        ic_msg!(
            invoke_context,
            "expected uninitialized stake account owner to be {}, not {}",
            id(),
            *uninitialized_stake_account.get_owner()
        );
        return Err(InstructionError::IncorrectProgramId);
    }
    if uninitialized_stake_account.get_data().len() != StakeState::size_of() {
        ic_msg!(
            invoke_context,
            "expected uninitialized stake account data len to be {}, not {}",
            StakeState::size_of(),
            uninitialized_stake_account.get_data().len()
        );
        return Err(InstructionError::InvalidAccountData);
    }
    if !matches!(
        uninitialized_stake_account.get_state()?,
        StakeState::Uninitialized
    ) {
        ic_msg!(
            invoke_context,
            "expected uninitialized stake account to be uninitialized",
        );
        return Err(InstructionError::AccountAlreadyInitialized);
    }

    // validate the provided vote account
    let vote_account = instruction_context
        .try_borrow_instruction_account(transaction_context, vote_account_index)?;
    if *vote_account.get_owner() != solana_vote_program::id() {
        ic_msg!(
            invoke_context,
            "expected vote account owner to be {}, not {}",
            solana_vote_program::id(),
            *vote_account.get_owner()
        );
        return Err(InstructionError::IncorrectProgramId);
    }
    let vote_pubkey = *vote_account.get_key();
    let vote_state = vote_account.get_state::<VoteStateVersions>()?;

    let (stake_meta, effective_stake) =
        if let StakeState::Stake(meta, stake) = stake_account.get_state()? {
            let stake_history = invoke_context.get_sysvar_cache().get_stake_history()?;
            let status = stake
                .delegation
                .stake_activating_and_deactivating(clock.epoch, Some(&stake_history));
            if status.effective == 0 || status.activating != 0 || status.deactivating != 0 {
                ic_msg!(invoke_context, "stake is not active");
                return Err(StakeError::RedelegateTransientOrInactiveStake.into());
            }

            // Deny redelegating to the same vote account. This is nonsensical and could be used to
            // grief the global stake warm-up/cool-down rate
            if stake.delegation.voter_pubkey == vote_pubkey {
                ic_msg!(
                    invoke_context,
                    "redelegating to the same vote account not permitted"
                );
                return Err(StakeError::RedelegateToSameVoteAccount.into());
            }

            (meta, status.effective)
        } else {
            ic_msg!(invoke_context, "invalid stake account data",);
            return Err(InstructionError::InvalidAccountData);
        };

    // deactivate `stake_account`
    //
    // Note: This function also ensures `signers` contains the `StakeAuthorize::Staker`
    deactivate(stake_account, &clock, signers)?;

    // transfer the effective stake to the uninitialized stake account
    stake_account.checked_sub_lamports(effective_stake)?;
    uninitialized_stake_account.checked_add_lamports(effective_stake)?;

    // initialize and schedule `uninitialized_stake_account` for activation
    let sysvar_cache = invoke_context.get_sysvar_cache();
    let rent = sysvar_cache.get_rent()?;
    let mut uninitialized_stake_meta = stake_meta;
    uninitialized_stake_meta.rent_exempt_reserve =
        rent.minimum_balance(uninitialized_stake_account.get_data().len());

    let ValidatedDelegatedInfo { stake_amount } = validate_delegated_amount(
        &uninitialized_stake_account,
        &uninitialized_stake_meta,
        &invoke_context.feature_set,
    )?;
    uninitialized_stake_account.set_state(&StakeState::Stake(
        uninitialized_stake_meta,
        new_stake(
            stake_amount,
            &vote_pubkey,
            &vote_state.convert_to_current(),
            clock.epoch,
            config,
        ),
    ))?;

    Ok(())
}

#[allow(clippy::too_many_arguments)]
pub fn withdraw(
    transaction_context: &TransactionContext,
    instruction_context: &InstructionContext,
    stake_account_index: usize,
    lamports: u64,
    to_index: usize,
    clock: &Clock,
    stake_history: &StakeHistory,
    withdraw_authority_index: usize,
    custodian_index: Option<usize>,
    feature_set: &FeatureSet,
) -> Result<(), InstructionError> {
    let withdraw_authority_pubkey = transaction_context.get_key_of_account_at_index(
        instruction_context
            .get_index_of_instruction_account_in_transaction(withdraw_authority_index)?,
    )?;
    if !instruction_context.is_instruction_account_signer(withdraw_authority_index)? {
        return Err(InstructionError::MissingRequiredSignature);
    }
    let mut signers = HashSet::new();
    signers.insert(*withdraw_authority_pubkey);

    let mut stake_account = instruction_context
        .try_borrow_instruction_account(transaction_context, stake_account_index)?;
    let (lockup, reserve, is_staked) = match stake_account.get_state()? {
        StakeState::Stake(meta, stake) => {
            meta.authorized
                .check(&signers, StakeAuthorize::Withdrawer)?;
            // if we have a deactivation epoch and we're in cooldown
            let staked = if clock.epoch >= stake.delegation.deactivation_epoch {
                stake.delegation.stake(clock.epoch, Some(stake_history))
            } else {
                // Assume full stake if the stake account hasn't been
                //  de-activated, because in the future the exposed stake
                //  might be higher than stake.stake() due to warmup
                stake.delegation.stake
            };

            let staked_and_reserve = checked_add(staked, meta.rent_exempt_reserve)?;
            (meta.lockup, staked_and_reserve, staked != 0)
        }
        StakeState::Initialized(meta) => {
            meta.authorized
                .check(&signers, StakeAuthorize::Withdrawer)?;
            // stake accounts must have a balance >= rent_exempt_reserve
            let reserve = if feature_set.is_active(&stake_allow_zero_undelegated_amount::id()) {
                meta.rent_exempt_reserve
            } else {
                checked_add(
                    meta.rent_exempt_reserve,
                    crate::get_minimum_delegation(feature_set),
                )?
            };

            (meta.lockup, reserve, false)
        }
        StakeState::Uninitialized => {
            if !signers.contains(stake_account.get_key()) {
                return Err(InstructionError::MissingRequiredSignature);
            }
            (Lockup::default(), 0, false) // no lockup, no restrictions
        }
        _ => return Err(InstructionError::InvalidAccountData),
    };

    // verify that lockup has expired or that the withdrawal is signed by
    //   the custodian, both epoch and unix_timestamp must have passed
    let custodian_pubkey = if let Some(custodian_index) = custodian_index {
        if instruction_context.is_instruction_account_signer(custodian_index)? {
            Some(
                transaction_context.get_key_of_account_at_index(
                    instruction_context
                        .get_index_of_instruction_account_in_transaction(custodian_index)?,
                )?,
            )
        } else {
            None
        }
    } else {
        None
    };
    if lockup.is_in_force(clock, custodian_pubkey) {
        return Err(StakeError::LockupInForce.into());
    }

    let lamports_and_reserve = checked_add(lamports, reserve)?;
    // if the stake is active, we mustn't allow the account to go away
    if is_staked // line coverage for branch coverage
            && lamports_and_reserve > stake_account.get_lamports()
    {
        return Err(InstructionError::InsufficientFunds);
    }

    if lamports != stake_account.get_lamports() // not a full withdrawal
            && lamports_and_reserve > stake_account.get_lamports()
    {
        assert!(!is_staked);
        return Err(InstructionError::InsufficientFunds);
    }

    // Deinitialize state upon zero balance
    if lamports == stake_account.get_lamports() {
        stake_account.set_state(&StakeState::Uninitialized)?;
    }

    stake_account.checked_sub_lamports(lamports)?;
    drop(stake_account);
    let mut to =
        instruction_context.try_borrow_instruction_account(transaction_context, to_index)?;
    to.checked_add_lamports(lamports)?;
    Ok(())
}

pub(crate) fn deactivate_delinquent(
    transaction_context: &TransactionContext,
    instruction_context: &InstructionContext,
    stake_account: &mut BorrowedAccount,
    delinquent_vote_account_index: usize,
    reference_vote_account_index: usize,
    current_epoch: Epoch,
) -> Result<(), InstructionError> {
    let delinquent_vote_account_pubkey = transaction_context.get_key_of_account_at_index(
        instruction_context
            .get_index_of_instruction_account_in_transaction(delinquent_vote_account_index)?,
    )?;
    let delinquent_vote_account = instruction_context
        .try_borrow_instruction_account(transaction_context, delinquent_vote_account_index)?;
    if *delinquent_vote_account.get_owner() != solana_vote_program::id() {
        return Err(InstructionError::IncorrectProgramId);
    }
    let delinquent_vote_state = delinquent_vote_account
        .get_state::<VoteStateVersions>()?
        .convert_to_current();

    let reference_vote_account = instruction_context
        .try_borrow_instruction_account(transaction_context, reference_vote_account_index)?;
    if *reference_vote_account.get_owner() != solana_vote_program::id() {
        return Err(InstructionError::IncorrectProgramId);
    }
    let reference_vote_state = reference_vote_account
        .get_state::<VoteStateVersions>()?
        .convert_to_current();

    if !acceptable_reference_epoch_credits(&reference_vote_state.epoch_credits, current_epoch) {
        return Err(StakeError::InsufficientReferenceVotes.into());
    }

    if let StakeState::Stake(meta, mut stake) = stake_account.get_state()? {
        if stake.delegation.voter_pubkey != *delinquent_vote_account_pubkey {
            return Err(StakeError::VoteAddressMismatch.into());
        }

        // Deactivate the stake account if its delegated vote account has never voted or has not
        // voted in the last `MINIMUM_DELINQUENT_EPOCHS_FOR_DEACTIVATION`
        if eligible_for_deactivate_delinquent(&delinquent_vote_state.epoch_credits, current_epoch) {
            stake.deactivate(current_epoch)?;
            stake_account.set_state(&StakeState::Stake(meta, stake))
        } else {
            Err(StakeError::MinimumDelinquentEpochsForDeactivationNotMet.into())
        }
    } else {
        Err(InstructionError::InvalidAccountData)
    }
}

/// After calling `validate_delegated_amount()`, this struct contains calculated values that are used
/// by the caller.
struct ValidatedDelegatedInfo {
    stake_amount: u64,
}

/// 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.
fn validate_delegated_amount(
    account: &BorrowedAccount,
    meta: &Meta,
    feature_set: &FeatureSet,
) -> Result<ValidatedDelegatedInfo, InstructionError> {
    let stake_amount = account
        .get_lamports()
        .saturating_sub(meta.rent_exempt_reserve); // can't stake the rent

    // Stake accounts may be initialized with a stake amount below the minimum delegation so check
    // that the minimum is met before delegation.
    if (feature_set.is_active(&stake_allow_zero_undelegated_amount::id())
        || feature_set.is_active(&feature_set::stake_raise_minimum_delegation_to_1_sol::id()))
        && stake_amount < crate::get_minimum_delegation(feature_set)
    {
        return Err(StakeError::InsufficientDelegation.into());
    }
    Ok(ValidatedDelegatedInfo { stake_amount })
}

/// After calling `validate_split_amount()`, this struct contains calculated values that are used
/// by the caller.
#[derive(Copy, Clone, Debug, Default)]
struct ValidatedSplitInfo {
    source_remaining_balance: u64,
    destination_rent_exempt_reserve: u64,
}

/// Ensure the split amount is valid.  This checks the source and destination accounts meet the
/// minimum balance requirements, which is the rent exempt reserve plus the minimum stake
/// delegation, and that the source account has enough lamports for the request split amount.  If
/// not, return an error.
fn validate_split_amount(
    invoke_context: &InvokeContext,
    transaction_context: &TransactionContext,
    instruction_context: &InstructionContext,
    source_account_index: usize,
    destination_account_index: usize,
    lamports: u64,
    source_meta: &Meta,
    source_stake: Option<&Stake>,
    additional_required_lamports: u64,
) -> Result<ValidatedSplitInfo, InstructionError> {
    let source_account = instruction_context
        .try_borrow_instruction_account(transaction_context, source_account_index)?;
    let source_lamports = source_account.get_lamports();
    let source_data_len = source_account.get_data().len();
    drop(source_account);
    let destination_account = instruction_context
        .try_borrow_instruction_account(transaction_context, destination_account_index)?;
    let destination_lamports = destination_account.get_lamports();
    let destination_data_len = destination_account.get_data().len();
    drop(destination_account);

    // Split amount has to be something
    if lamports == 0 {
        return Err(InstructionError::InsufficientFunds);
    }

    // Obviously cannot split more than what the source account has
    if lamports > source_lamports {
        return Err(InstructionError::InsufficientFunds);
    }

    // Verify that the source account still has enough lamports left after splitting:
    // EITHER at least the minimum balance, OR zero (in this case the source
    // account is transferring all lamports to new destination account, and the source
    // account will be closed)
    let source_minimum_balance = source_meta
        .rent_exempt_reserve
        .saturating_add(additional_required_lamports);
    let source_remaining_balance = source_lamports.saturating_sub(lamports);
    if source_remaining_balance == 0 {
        // full amount is a withdrawal
        // nothing to do here
    } else if source_remaining_balance < source_minimum_balance {
        // the remaining balance is too low to do the split
        return Err(InstructionError::InsufficientFunds);
    } else {
        // all clear!
        // nothing to do here
    }

    // Verify the destination account meets the minimum balance requirements
    // This must handle:
    // 1. The destination account having a different rent exempt reserve due to data size changes
    // 2. The destination account being prefunded, which would lower the minimum split amount
    let destination_rent_exempt_reserve = if invoke_context
        .feature_set
        .is_active(&stake_split_uses_rent_sysvar::ID)
    {
        let rent = invoke_context.get_sysvar_cache().get_rent()?;
        rent.minimum_balance(destination_data_len)
    } else {
        calculate_split_rent_exempt_reserve(
            source_meta.rent_exempt_reserve,
            source_data_len as u64,
            destination_data_len as u64,
        )
    };
    let destination_minimum_balance =
        destination_rent_exempt_reserve.saturating_add(additional_required_lamports);
    let destination_balance_deficit =
        destination_minimum_balance.saturating_sub(destination_lamports);
    if lamports < destination_balance_deficit {
        return Err(InstructionError::InsufficientFunds);
    }

    // If the source account is already staked, the destination will end up staked as well.  Verify
    // the destination account's delegation amount is at least the minimum delegation.
    //
    // The *delegation* requirements are different than the *balance* requirements.  If the
    // destination account is prefunded with a balance of `rent exempt reserve + minimum stake
    // delegation - 1`, the minimum split amount to satisfy the *balance* requirements is 1
    // lamport.  And since *only* the split amount is immediately staked in the destination
    // account, the split amount must be at least the minimum stake delegation.  So if the minimum
    // stake delegation was 10 lamports, then a split amount of 1 lamport would not meet the
    // *delegation* requirements.
    if source_stake.is_some() && lamports < additional_required_lamports {
        return Err(InstructionError::InsufficientFunds);
    }

    Ok(ValidatedSplitInfo {
        source_remaining_balance,
        destination_rent_exempt_reserve,
    })
}

#[derive(Clone, Debug, PartialEq)]
enum MergeKind {
    Inactive(Meta, u64),
    ActivationEpoch(Meta, Stake),
    FullyActive(Meta, Stake),
}

impl MergeKind {
    fn meta(&self) -> &Meta {
        match self {
            Self::Inactive(meta, _) => meta,
            Self::ActivationEpoch(meta, _) => meta,
            Self::FullyActive(meta, _) => meta,
        }
    }

    fn active_stake(&self) -> Option<&Stake> {
        match self {
            Self::Inactive(_, _) => None,
            Self::ActivationEpoch(_, stake) => Some(stake),
            Self::FullyActive(_, stake) => Some(stake),
        }
    }

    fn get_if_mergeable(
        invoke_context: &InvokeContext,
        stake_state: &StakeState,
        stake_lamports: u64,
        clock: &Clock,
        stake_history: &StakeHistory,
    ) -> Result<Self, InstructionError> {
        match stake_state {
            StakeState::Stake(meta, stake) => {
                // stake must not be in a transient state. Transient here meaning
                // activating or deactivating with non-zero effective stake.
                let status = stake
                    .delegation
                    .stake_activating_and_deactivating(clock.epoch, Some(stake_history));

                match (status.effective, status.activating, status.deactivating) {
                    (0, 0, 0) => Ok(Self::Inactive(*meta, stake_lamports)),
                    (0, _, _) => Ok(Self::ActivationEpoch(*meta, *stake)),
                    (_, 0, 0) => Ok(Self::FullyActive(*meta, *stake)),
                    _ => {
                        let err = StakeError::MergeTransientStake;
                        ic_msg!(invoke_context, "{}", err);
                        Err(err.into())
                    }
                }
            }
            StakeState::Initialized(meta) => Ok(Self::Inactive(*meta, stake_lamports)),
            _ => Err(InstructionError::InvalidAccountData),
        }
    }

    fn metas_can_merge(
        invoke_context: &InvokeContext,
        stake: &Meta,
        source: &Meta,
        clock: &Clock,
    ) -> Result<(), InstructionError> {
        // lockups may mismatch so long as both have expired
        let can_merge_lockups = stake.lockup == source.lockup
            || (!stake.lockup.is_in_force(clock, None) && !source.lockup.is_in_force(clock, None));
        // `rent_exempt_reserve` has no bearing on the mergeability of accounts,
        // as the source account will be culled by runtime once the operation
        // succeeds. Considering it here would needlessly prevent merging stake
        // accounts with differing data lengths, which already exist in the wild
        // due to an SDK bug
        if stake.authorized == source.authorized && can_merge_lockups {
            Ok(())
        } else {
            ic_msg!(invoke_context, "Unable to merge due to metadata mismatch");
            Err(StakeError::MergeMismatch.into())
        }
    }

    fn active_delegations_can_merge(
        invoke_context: &InvokeContext,
        stake: &Delegation,
        source: &Delegation,
    ) -> Result<(), InstructionError> {
        if stake.voter_pubkey != source.voter_pubkey {
            ic_msg!(invoke_context, "Unable to merge due to voter mismatch");
            Err(StakeError::MergeMismatch.into())
        } else if (stake.warmup_cooldown_rate - source.warmup_cooldown_rate).abs() < f64::EPSILON
            && stake.deactivation_epoch == Epoch::MAX
            && source.deactivation_epoch == Epoch::MAX
        {
            Ok(())
        } else {
            ic_msg!(invoke_context, "Unable to merge due to stake deactivation");
            Err(StakeError::MergeMismatch.into())
        }
    }

    // Remove this when the `stake_merge_with_unmatched_credits_observed` feature is removed
    fn active_stakes_can_merge(
        invoke_context: &InvokeContext,
        stake: &Stake,
        source: &Stake,
    ) -> Result<(), InstructionError> {
        Self::active_delegations_can_merge(invoke_context, &stake.delegation, &source.delegation)?;
        // `credits_observed` MUST match to prevent earning multiple rewards
        // from a stake account by merging it into another stake account that
        // is small enough to not be paid out every epoch. This would effectively
        // reset the larger stake accounts `credits_observed` to that of the
        // smaller account.
        if stake.credits_observed == source.credits_observed {
            Ok(())
        } else {
            ic_msg!(
                invoke_context,
                "Unable to merge due to credits observed mismatch"
            );
            Err(StakeError::MergeMismatch.into())
        }
    }

    fn merge(
        self,
        invoke_context: &InvokeContext,
        source: Self,
        clock: &Clock,
    ) -> Result<Option<StakeState>, InstructionError> {
        Self::metas_can_merge(invoke_context, self.meta(), source.meta(), clock)?;
        self.active_stake()
            .zip(source.active_stake())
            .map(|(stake, source)| {
                if invoke_context
                    .feature_set
                    .is_active(&stake_merge_with_unmatched_credits_observed::id())
                {
                    Self::active_delegations_can_merge(
                        invoke_context,
                        &stake.delegation,
                        &source.delegation,
                    )
                } else {
                    Self::active_stakes_can_merge(invoke_context, stake, source)
                }
            })
            .unwrap_or(Ok(()))?;
        let merged_state = match (self, source) {
            (Self::Inactive(_, _), Self::Inactive(_, _)) => None,
            (Self::Inactive(_, _), Self::ActivationEpoch(_, _)) => None,
            (Self::ActivationEpoch(meta, mut stake), Self::Inactive(_, source_lamports)) => {
                stake.delegation.stake = checked_add(stake.delegation.stake, source_lamports)?;
                Some(StakeState::Stake(meta, stake))
            }
            (
                Self::ActivationEpoch(meta, mut stake),
                Self::ActivationEpoch(source_meta, source_stake),
            ) => {
                let source_lamports = checked_add(
                    source_meta.rent_exempt_reserve,
                    source_stake.delegation.stake,
                )?;
                merge_delegation_stake_and_credits_observed(
                    invoke_context,
                    &mut stake,
                    source_lamports,
                    source_stake.credits_observed,
                )?;
                Some(StakeState::Stake(meta, stake))
            }
            (Self::FullyActive(meta, mut stake), Self::FullyActive(_, source_stake)) => {
                // Don't stake the source account's `rent_exempt_reserve` to
                // protect against the magic activation loophole. It will
                // instead be moved into the destination account as extra,
                // withdrawable `lamports`
                merge_delegation_stake_and_credits_observed(
                    invoke_context,
                    &mut stake,
                    source_stake.delegation.stake,
                    source_stake.credits_observed,
                )?;
                Some(StakeState::Stake(meta, stake))
            }
            _ => return Err(StakeError::MergeMismatch.into()),
        };
        Ok(merged_state)
    }
}

fn merge_delegation_stake_and_credits_observed(
    invoke_context: &InvokeContext,
    stake: &mut Stake,
    absorbed_lamports: u64,
    absorbed_credits_observed: u64,
) -> Result<(), InstructionError> {
    if invoke_context
        .feature_set
        .is_active(&stake_merge_with_unmatched_credits_observed::id())
    {
        stake.credits_observed =
            stake_weighted_credits_observed(stake, absorbed_lamports, absorbed_credits_observed)
                .ok_or(InstructionError::ArithmeticOverflow)?;
    }
    stake.delegation.stake = checked_add(stake.delegation.stake, absorbed_lamports)?;
    Ok(())
}

/// Calculate the effective credits observed for two stakes when merging
///
/// When merging two `ActivationEpoch` or `FullyActive` stakes, the credits
/// observed of the merged stake is the weighted average of the two stakes'
/// credits observed.
///
/// This is because we can derive the effective credits_observed by reversing the staking
/// rewards equation, _while keeping the rewards unchanged after merge (i.e. strong
/// requirement)_, like below:
///
/// a(N) => account, r => rewards, s => stake, c => credits:
/// assume:
///   a3 = merge(a1, a2)
/// then:
///   a3.s = a1.s + a2.s
///
/// Next, given:
///   aN.r = aN.c * aN.s (for every N)
/// finally:
///        a3.r = a1.r + a2.r
/// a3.c * a3.s = a1.c * a1.s + a2.c * a2.s
///        a3.c = (a1.c * a1.s + a2.c * a2.s) / (a1.s + a2.s)     // QED
///
/// (For this discussion, we omitted irrelevant variables, including distance
///  calculation against vote_account and point indirection.)
fn stake_weighted_credits_observed(
    stake: &Stake,
    absorbed_lamports: u64,
    absorbed_credits_observed: u64,
) -> Option<u64> {
    if stake.credits_observed == absorbed_credits_observed {
        Some(stake.credits_observed)
    } else {
        let total_stake = u128::from(stake.delegation.stake.checked_add(absorbed_lamports)?);
        let stake_weighted_credits =
            u128::from(stake.credits_observed).checked_mul(u128::from(stake.delegation.stake))?;
        let absorbed_weighted_credits =
            u128::from(absorbed_credits_observed).checked_mul(u128::from(absorbed_lamports))?;
        // Discard fractional credits as a merge side-effect friction by taking
        // the ceiling, done by adding `denominator - 1` to the numerator.
        let total_weighted_credits = stake_weighted_credits
            .checked_add(absorbed_weighted_credits)?
            .checked_add(total_stake)?
            .checked_sub(1)?;
        u64::try_from(total_weighted_credits.checked_div(total_stake)?).ok()
    }
}

// utility function, used by runtime
// returns a tuple of (stakers_reward,voters_reward)
#[doc(hidden)]
pub fn redeem_rewards(
    rewarded_epoch: Epoch,
    stake_state: StakeState,
    stake_account: &mut AccountSharedData,
    vote_state: &VoteState,
    point_value: &PointValue,
    stake_history: Option<&StakeHistory>,
    inflation_point_calc_tracer: Option<impl Fn(&InflationPointCalculationEvent)>,
    credits_auto_rewind: bool,
) -> Result<(u64, u64), InstructionError> {
    if let StakeState::Stake(meta, mut stake) = stake_state {
        if let Some(inflation_point_calc_tracer) = inflation_point_calc_tracer.as_ref() {
            inflation_point_calc_tracer(
                &InflationPointCalculationEvent::EffectiveStakeAtRewardedEpoch(
                    stake.stake(rewarded_epoch, stake_history),
                ),
            );
            inflation_point_calc_tracer(&InflationPointCalculationEvent::RentExemptReserve(
                meta.rent_exempt_reserve,
            ));
            inflation_point_calc_tracer(&InflationPointCalculationEvent::Commission(
                vote_state.commission,
            ));
        }

        if let Some((stakers_reward, voters_reward)) = redeem_stake_rewards(
            rewarded_epoch,
            &mut stake,
            point_value,
            vote_state,
            stake_history,
            inflation_point_calc_tracer,
            credits_auto_rewind,
        ) {
            stake_account.checked_add_lamports(stakers_reward)?;
            stake_account.set_state(&StakeState::Stake(meta, stake))?;

            Ok((stakers_reward, voters_reward))
        } else {
            Err(StakeError::NoCreditsToRedeem.into())
        }
    } else {
        Err(InstructionError::InvalidAccountData)
    }
}

// utility function, used by runtime
#[doc(hidden)]
pub fn calculate_points(
    stake_state: &StakeState,
    vote_state: &VoteState,
    stake_history: Option<&StakeHistory>,
) -> Result<u128, InstructionError> {
    if let StakeState::Stake(_meta, stake) = stake_state {
        Ok(calculate_stake_points(
            stake,
            vote_state,
            stake_history,
            null_tracer(),
        ))
    } else {
        Err(InstructionError::InvalidAccountData)
    }
}

// utility function, used by Split
//This emulates current Rent math in order to preserve backward compatibility. In the future, and
//to support variable rent, the Split instruction should pass in the Rent sysvar instead.
fn calculate_split_rent_exempt_reserve(
    source_rent_exempt_reserve: u64,
    source_data_len: u64,
    split_data_len: u64,
) -> u64 {
    let lamports_per_byte_year =
        source_rent_exempt_reserve / (source_data_len + ACCOUNT_STORAGE_OVERHEAD);
    lamports_per_byte_year * (split_data_len + ACCOUNT_STORAGE_OVERHEAD)
}

pub type RewriteStakeStatus = (&'static str, (u64, u64), (u64, u64));

// utility function, used by runtime::Stakes, tests
pub fn new_stake_history_entry<'a, I>(
    epoch: Epoch,
    stakes: I,
    history: Option<&StakeHistory>,
) -> StakeHistoryEntry
where
    I: Iterator<Item = &'a Delegation>,
{
    stakes.fold(StakeHistoryEntry::default(), |sum, stake| {
        sum + stake.stake_activating_and_deactivating(epoch, history)
    })
}

// utility function, used by tests
pub fn create_stake_history_from_delegations(
    bootstrap: Option<u64>,
    epochs: std::ops::Range<Epoch>,
    delegations: &[Delegation],
) -> StakeHistory {
    let mut stake_history = StakeHistory::default();

    let bootstrap_delegation = if let Some(bootstrap) = bootstrap {
        vec![Delegation {
            activation_epoch: std::u64::MAX,
            stake: bootstrap,
            ..Delegation::default()
        }]
    } else {
        vec![]
    };

    for epoch in epochs {
        let entry = new_stake_history_entry(
            epoch,
            delegations.iter().chain(bootstrap_delegation.iter()),
            Some(&stake_history),
        );
        stake_history.add(epoch, entry);
    }

    stake_history
}

// genesis investor accounts
pub fn create_lockup_stake_account(
    authorized: &Authorized,
    lockup: &Lockup,
    rent: &Rent,
    lamports: u64,
) -> AccountSharedData {
    let mut stake_account = AccountSharedData::new(lamports, StakeState::size_of(), &id());

    let rent_exempt_reserve = rent.minimum_balance(stake_account.data().len());
    assert!(
        lamports >= rent_exempt_reserve,
        "lamports: {} is less than rent_exempt_reserve {}",
        lamports,
        rent_exempt_reserve
    );

    stake_account
        .set_state(&StakeState::Initialized(Meta {
            authorized: *authorized,
            lockup: *lockup,
            rent_exempt_reserve,
        }))
        .expect("set_state");

    stake_account
}

// utility function, used by Bank, tests, genesis for bootstrap
pub fn create_account(
    authorized: &Pubkey,
    voter_pubkey: &Pubkey,
    vote_account: &AccountSharedData,
    rent: &Rent,
    lamports: u64,
) -> AccountSharedData {
    do_create_account(
        authorized,
        voter_pubkey,
        vote_account,
        rent,
        lamports,
        Epoch::MAX,
    )
}

// utility function, used by tests
pub fn create_account_with_activation_epoch(
    authorized: &Pubkey,
    voter_pubkey: &Pubkey,
    vote_account: &AccountSharedData,
    rent: &Rent,
    lamports: u64,
    activation_epoch: Epoch,
) -> AccountSharedData {
    do_create_account(
        authorized,
        voter_pubkey,
        vote_account,
        rent,
        lamports,
        activation_epoch,
    )
}

fn do_create_account(
    authorized: &Pubkey,
    voter_pubkey: &Pubkey,
    vote_account: &AccountSharedData,
    rent: &Rent,
    lamports: u64,
    activation_epoch: Epoch,
) -> AccountSharedData {
    let mut stake_account = AccountSharedData::new(lamports, StakeState::size_of(), &id());

    let vote_state = VoteState::from(vote_account).expect("vote_state");

    let rent_exempt_reserve = rent.minimum_balance(stake_account.data().len());

    stake_account
        .set_state(&StakeState::Stake(
            Meta {
                authorized: Authorized::auto(authorized),
                rent_exempt_reserve,
                ..Meta::default()
            },
            new_stake(
                lamports - rent_exempt_reserve, // underflow is an error, is basically: assert!(lamports > rent_exempt_reserve);
                voter_pubkey,
                &vote_state,
                activation_epoch,
                &Config::default(),
            ),
        ))
        .expect("set_state");

    stake_account
}

#[cfg(test)]
mod tests {
    use {
        super::*,
        proptest::prelude::*,
        solana_program_runtime::invoke_context::InvokeContext,
        solana_sdk::{
            account::{create_account_shared_data_for_test, AccountSharedData},
            native_token,
            pubkey::Pubkey,
            sysvar::SysvarId,
            transaction_context::TransactionContext,
        },
    };

    #[test]
    fn test_authorized_authorize() {
        let staker = solana_sdk::pubkey::new_rand();
        let mut authorized = Authorized::auto(&staker);
        let mut signers = HashSet::new();
        assert_eq!(
            authorized.authorize(&signers, &staker, StakeAuthorize::Staker, None),
            Err(InstructionError::MissingRequiredSignature)
        );
        signers.insert(staker);
        assert_eq!(
            authorized.authorize(&signers, &staker, StakeAuthorize::Staker, None),
            Ok(())
        );
    }

    #[test]
    fn test_authorized_authorize_with_custodian() {
        let staker = solana_sdk::pubkey::new_rand();
        let custodian = solana_sdk::pubkey::new_rand();
        let invalid_custodian = solana_sdk::pubkey::new_rand();
        let mut authorized = Authorized::auto(&staker);
        let mut signers = HashSet::new();
        signers.insert(staker);

        let lockup = Lockup {
            epoch: 1,
            unix_timestamp: 1,
            custodian,
        };
        let clock = Clock {
            epoch: 0,
            unix_timestamp: 0,
            ..Clock::default()
        };

        // Legacy behaviour when the `require_custodian_for_locked_stake_authorize` feature is
        // inactive
        assert_eq!(
            authorized.authorize(&signers, &staker, StakeAuthorize::Withdrawer, None),
            Ok(())
        );

        // No lockup, no custodian
        assert_eq!(
            authorized.authorize(
                &signers,
                &staker,
                StakeAuthorize::Withdrawer,
                Some((&Lockup::default(), &clock, None))
            ),
            Ok(())
        );

        // No lockup, invalid custodian not a signer
        assert_eq!(
            authorized.authorize(
                &signers,
                &staker,
                StakeAuthorize::Withdrawer,
                Some((&Lockup::default(), &clock, Some(&invalid_custodian)))
            ),
            Ok(()) // <== invalid custodian doesn't matter, there's no lockup
        );

        // Lockup active, invalid custodian not a signer
        assert_eq!(
            authorized.authorize(
                &signers,
                &staker,
                StakeAuthorize::Withdrawer,
                Some((&lockup, &clock, Some(&invalid_custodian)))
            ),
            Err(StakeError::CustodianSignatureMissing.into()),
        );

        signers.insert(invalid_custodian);

        // No lockup, invalid custodian is a signer
        assert_eq!(
            authorized.authorize(
                &signers,
                &staker,
                StakeAuthorize::Withdrawer,
                Some((&Lockup::default(), &clock, Some(&invalid_custodian)))
            ),
            Ok(()) // <== invalid custodian doesn't matter, there's no lockup
        );

        // Lockup active, invalid custodian is a signer
        signers.insert(invalid_custodian);
        assert_eq!(
            authorized.authorize(
                &signers,
                &staker,
                StakeAuthorize::Withdrawer,
                Some((&lockup, &clock, Some(&invalid_custodian)))
            ),
            Err(StakeError::LockupInForce.into()), // <== invalid custodian rejected
        );

        signers.remove(&invalid_custodian);

        // Lockup active, no custodian
        assert_eq!(
            authorized.authorize(
                &signers,
                &staker,
                StakeAuthorize::Withdrawer,
                Some((&lockup, &clock, None))
            ),
            Err(StakeError::CustodianMissing.into()),
        );

        // Lockup active, custodian not a signer
        assert_eq!(
            authorized.authorize(
                &signers,
                &staker,
                StakeAuthorize::Withdrawer,
                Some((&lockup, &clock, Some(&custodian)))
            ),
            Err(StakeError::CustodianSignatureMissing.into()),
        );

        // Lockup active, custodian is a signer
        signers.insert(custodian);
        assert_eq!(
            authorized.authorize(
                &signers,
                &staker,
                StakeAuthorize::Withdrawer,
                Some((&lockup, &clock, Some(&custodian)))
            ),
            Ok(())
        );
    }

    #[test]
    fn test_stake_state_stake_from_fail() {
        let mut stake_account = AccountSharedData::new(0, StakeState::size_of(), &id());

        stake_account
            .set_state(&StakeState::default())
            .expect("set_state");

        assert_eq!(stake_from(&stake_account), None);
    }

    #[test]
    fn test_stake_is_bootstrap() {
        assert!(Delegation {
            activation_epoch: std::u64::MAX,
            ..Delegation::default()
        }
        .is_bootstrap());
        assert!(!Delegation {
            activation_epoch: 0,
            ..Delegation::default()
        }
        .is_bootstrap());
    }

    #[test]
    fn test_stake_activating_and_deactivating() {
        let stake = Delegation {
            stake: 1_000,
            activation_epoch: 0, // activating at zero
            deactivation_epoch: 5,
            ..Delegation::default()
        };

        // save this off so stake.config.warmup_rate changes don't break this test
        let increment = (1_000_f64 * stake.warmup_cooldown_rate) as u64;

        let mut stake_history = StakeHistory::default();
        // assert that this stake follows step function if there's no history
        assert_eq!(
            stake.stake_activating_and_deactivating(stake.activation_epoch, Some(&stake_history),),
            StakeActivationStatus::with_effective_and_activating(0, stake.stake),
        );
        for epoch in stake.activation_epoch + 1..stake.deactivation_epoch {
            assert_eq!(
                stake.stake_activating_and_deactivating(epoch, Some(&stake_history)),
                StakeActivationStatus::with_effective(stake.stake),
            );
        }
        // assert that this stake is full deactivating
        assert_eq!(
            stake
                .stake_activating_and_deactivating(stake.deactivation_epoch, Some(&stake_history),),
            StakeActivationStatus::with_deactivating(stake.stake),
        );
        // assert that this stake is fully deactivated if there's no history
        assert_eq!(
            stake.stake_activating_and_deactivating(
                stake.deactivation_epoch + 1,
                Some(&stake_history),
            ),
            StakeActivationStatus::default(),
        );

        stake_history.add(
            0u64, // entry for zero doesn't have my activating amount
            StakeHistoryEntry {
                effective: 1_000,
                ..StakeHistoryEntry::default()
            },
        );
        // assert that this stake is broken, because above setup is broken
        assert_eq!(
            stake.stake_activating_and_deactivating(1, Some(&stake_history)),
            StakeActivationStatus::with_effective_and_activating(0, stake.stake),
        );

        stake_history.add(
            0u64, // entry for zero has my activating amount
            StakeHistoryEntry {
                effective: 1_000,
                activating: 1_000,
                ..StakeHistoryEntry::default()
            },
            // no entry for 1, so this stake gets shorted
        );
        // assert that this stake is broken, because above setup is broken
        assert_eq!(
            stake.stake_activating_and_deactivating(2, Some(&stake_history)),
            StakeActivationStatus::with_effective_and_activating(
                increment,
                stake.stake - increment
            ),
        );

        // start over, test deactivation edge cases
        let mut stake_history = StakeHistory::default();

        stake_history.add(
            stake.deactivation_epoch, // entry for zero doesn't have my de-activating amount
            StakeHistoryEntry {
                effective: 1_000,
                ..StakeHistoryEntry::default()
            },
        );
        // assert that this stake is broken, because above setup is broken
        assert_eq!(
            stake.stake_activating_and_deactivating(
                stake.deactivation_epoch + 1,
                Some(&stake_history),
            ),
            StakeActivationStatus::with_deactivating(stake.stake),
        );

        // put in my initial deactivating amount, but don't put in an entry for next
        stake_history.add(
            stake.deactivation_epoch, // entry for zero has my de-activating amount
            StakeHistoryEntry {
                effective: 1_000,
                deactivating: 1_000,
                ..StakeHistoryEntry::default()
            },
        );
        // assert that this stake is broken, because above setup is broken
        assert_eq!(
            stake.stake_activating_and_deactivating(
                stake.deactivation_epoch + 2,
                Some(&stake_history),
            ),
            // hung, should be lower
            StakeActivationStatus::with_deactivating(stake.stake - increment),
        );
    }

    mod same_epoch_activation_then_deactivation {
        use super::*;

        enum OldDeactivationBehavior {
            Stuck,
            Slow,
        }

        fn do_test(
            old_behavior: OldDeactivationBehavior,
            expected_stakes: &[StakeActivationStatus],
        ) {
            let cluster_stake = 1_000;
            let activating_stake = 10_000;
            let some_stake = 700;
            let some_epoch = 0;

            let stake = Delegation {
                stake: some_stake,
                activation_epoch: some_epoch,
                deactivation_epoch: some_epoch,
                ..Delegation::default()
            };

            let mut stake_history = StakeHistory::default();
            let cluster_deactivation_at_stake_modified_epoch = match old_behavior {
                OldDeactivationBehavior::Stuck => 0,
                OldDeactivationBehavior::Slow => 1000,
            };

            let stake_history_entries = vec![
                (
                    cluster_stake,
                    activating_stake,
                    cluster_deactivation_at_stake_modified_epoch,
                ),
                (cluster_stake, activating_stake, 1000),
                (cluster_stake, activating_stake, 1000),
                (cluster_stake, activating_stake, 100),
                (cluster_stake, activating_stake, 100),
                (cluster_stake, activating_stake, 100),
                (cluster_stake, activating_stake, 100),
            ];

            for (epoch, (effective, activating, deactivating)) in
                stake_history_entries.into_iter().enumerate()
            {
                stake_history.add(
                    epoch as Epoch,
                    StakeHistoryEntry {
                        effective,
                        activating,
                        deactivating,
                    },
                );
            }

            assert_eq!(
                expected_stakes,
                (0..expected_stakes.len())
                    .map(|epoch| stake
                        .stake_activating_and_deactivating(epoch as u64, Some(&stake_history),))
                    .collect::<Vec<_>>()
            );
        }

        #[test]
        fn test_new_behavior_previously_slow() {
            // any stake accounts activated and deactivated at the same epoch
            // shouldn't been activated (then deactivated) at all!

            do_test(
                OldDeactivationBehavior::Slow,
                &[
                    StakeActivationStatus::default(),
                    StakeActivationStatus::default(),
                    StakeActivationStatus::default(),
                    StakeActivationStatus::default(),
                    StakeActivationStatus::default(),
                    StakeActivationStatus::default(),
                    StakeActivationStatus::default(),
                ],
            );
        }

        #[test]
        fn test_new_behavior_previously_stuck() {
            // any stake accounts activated and deactivated at the same epoch
            // shouldn't been activated (then deactivated) at all!

            do_test(
                OldDeactivationBehavior::Stuck,
                &[
                    StakeActivationStatus::default(),
                    StakeActivationStatus::default(),
                    StakeActivationStatus::default(),
                    StakeActivationStatus::default(),
                    StakeActivationStatus::default(),
                    StakeActivationStatus::default(),
                    StakeActivationStatus::default(),
                ],
            );
        }
    }

    #[test]
    fn test_inflation_and_slashing_with_activating_and_deactivating_stake() {
        // some really boring delegation and stake_history setup
        let (delegated_stake, mut stake, stake_history) = {
            let cluster_stake = 1_000;
            let delegated_stake = 700;

            let stake = Delegation {
                stake: delegated_stake,
                activation_epoch: 0,
                deactivation_epoch: 4,
                ..Delegation::default()
            };

            let mut stake_history = StakeHistory::default();
            stake_history.add(
                0,
                StakeHistoryEntry {
                    effective: cluster_stake,
                    activating: delegated_stake,
                    ..StakeHistoryEntry::default()
                },
            );
            let newly_effective_at_epoch1 = (cluster_stake as f64 * 0.25) as u64;
            assert_eq!(newly_effective_at_epoch1, 250);
            stake_history.add(
                1,
                StakeHistoryEntry {
                    effective: cluster_stake + newly_effective_at_epoch1,
                    activating: delegated_stake - newly_effective_at_epoch1,
                    ..StakeHistoryEntry::default()
                },
            );
            let newly_effective_at_epoch2 =
                ((cluster_stake + newly_effective_at_epoch1) as f64 * 0.25) as u64;
            assert_eq!(newly_effective_at_epoch2, 312);
            stake_history.add(
                2,
                StakeHistoryEntry {
                    effective: cluster_stake
                        + newly_effective_at_epoch1
                        + newly_effective_at_epoch2,
                    activating: delegated_stake
                        - newly_effective_at_epoch1
                        - newly_effective_at_epoch2,
                    ..StakeHistoryEntry::default()
                },
            );
            stake_history.add(
                3,
                StakeHistoryEntry {
                    effective: cluster_stake + delegated_stake,
                    ..StakeHistoryEntry::default()
                },
            );
            stake_history.add(
                4,
                StakeHistoryEntry {
                    effective: cluster_stake + delegated_stake,
                    deactivating: delegated_stake,
                    ..StakeHistoryEntry::default()
                },
            );
            let newly_not_effective_stake_at_epoch5 =
                ((cluster_stake + delegated_stake) as f64 * 0.25) as u64;
            assert_eq!(newly_not_effective_stake_at_epoch5, 425);
            stake_history.add(
                5,
                StakeHistoryEntry {
                    effective: cluster_stake + delegated_stake
                        - newly_not_effective_stake_at_epoch5,
                    deactivating: delegated_stake - newly_not_effective_stake_at_epoch5,
                    ..StakeHistoryEntry::default()
                },
            );

            (delegated_stake, stake, stake_history)
        };

        // helper closures
        let calculate_each_staking_status = |stake: &Delegation, epoch_count: usize| -> Vec<_> {
            (0..epoch_count)
                .map(|epoch| {
                    stake.stake_activating_and_deactivating(epoch as u64, Some(&stake_history))
                })
                .collect::<Vec<_>>()
        };
        let adjust_staking_status = |rate: f64, status: &[StakeActivationStatus]| {
            status
                .iter()
                .map(|entry| StakeActivationStatus {
                    effective: (entry.effective as f64 * rate) as u64,
                    activating: (entry.activating as f64 * rate) as u64,
                    deactivating: (entry.deactivating as f64 * rate) as u64,
                })
                .collect::<Vec<_>>()
        };

        let expected_staking_status_transition = vec![
            StakeActivationStatus::with_effective_and_activating(0, 700),
            StakeActivationStatus::with_effective_and_activating(250, 450),
            StakeActivationStatus::with_effective_and_activating(562, 138),
            StakeActivationStatus::with_effective(700),
            StakeActivationStatus::with_deactivating(700),
            StakeActivationStatus::with_deactivating(275),
            StakeActivationStatus::default(),
        ];
        let expected_staking_status_transition_base = vec![
            StakeActivationStatus::with_effective_and_activating(0, 700),
            StakeActivationStatus::with_effective_and_activating(250, 450),
            StakeActivationStatus::with_effective_and_activating(562, 138 + 1), // +1 is needed for rounding
            StakeActivationStatus::with_effective(700),
            StakeActivationStatus::with_deactivating(700),
            StakeActivationStatus::with_deactivating(275 + 1), // +1 is needed for rounding
            StakeActivationStatus::default(),
        ];

        // normal stake activating and deactivating transition test, just in case
        assert_eq!(
            expected_staking_status_transition,
            calculate_each_staking_status(&stake, expected_staking_status_transition.len())
        );

        // 10% inflation rewards assuming some sizable epochs passed!
        let rate = 1.10;
        stake.stake = (delegated_stake as f64 * rate) as u64;
        let expected_staking_status_transition =
            adjust_staking_status(rate, &expected_staking_status_transition_base);

        assert_eq!(
            expected_staking_status_transition,
            calculate_each_staking_status(&stake, expected_staking_status_transition_base.len()),
        );

        // 50% slashing!!!
        let rate = 0.5;
        stake.stake = (delegated_stake as f64 * rate) as u64;
        let expected_staking_status_transition =
            adjust_staking_status(rate, &expected_staking_status_transition_base);

        assert_eq!(
            expected_staking_status_transition,
            calculate_each_staking_status(&stake, expected_staking_status_transition_base.len()),
        );
    }

    #[test]
    fn test_stop_activating_after_deactivation() {
        let stake = Delegation {
            stake: 1_000,
            activation_epoch: 0,
            deactivation_epoch: 3,
            ..Delegation::default()
        };

        let base_stake = 1_000;
        let mut stake_history = StakeHistory::default();
        let mut effective = base_stake;
        let other_activation = 100;
        let mut other_activations = vec![0];

        // Build a stake history where the test staker always consumes all of the available warm
        // up and cool down stake. However, simulate other stakers beginning to activate during
        // the test staker's deactivation.
        for epoch in 0..=stake.deactivation_epoch + 1 {
            let (activating, deactivating) = if epoch < stake.deactivation_epoch {
                (stake.stake + base_stake - effective, 0)
            } else {
                let other_activation_sum: u64 = other_activations.iter().sum();
                let deactivating = effective - base_stake - other_activation_sum;
                (other_activation, deactivating)
            };

            stake_history.add(
                epoch,
                StakeHistoryEntry {
                    effective,
                    activating,
                    deactivating,
                },
            );

            let effective_rate_limited = (effective as f64 * stake.warmup_cooldown_rate) as u64;
            if epoch < stake.deactivation_epoch {
                effective += effective_rate_limited.min(activating);
                other_activations.push(0);
            } else {
                effective -= effective_rate_limited.min(deactivating);
                effective += other_activation;
                other_activations.push(other_activation);
            }
        }

        for epoch in 0..=stake.deactivation_epoch + 1 {
            let history = stake_history.get(epoch).unwrap();
            let other_activations: u64 = other_activations[..=epoch as usize].iter().sum();
            let expected_stake = history.effective - base_stake - other_activations;
            let (expected_activating, expected_deactivating) = if epoch < stake.deactivation_epoch {
                (history.activating, 0)
            } else {
                (0, history.deactivating)
            };
            assert_eq!(
                stake.stake_activating_and_deactivating(epoch, Some(&stake_history)),
                StakeActivationStatus {
                    effective: expected_stake,
                    activating: expected_activating,
                    deactivating: expected_deactivating,
                },
            );
        }
    }

    #[test]
    fn test_stake_warmup_cooldown_sub_integer_moves() {
        let delegations = [Delegation {
            stake: 2,
            activation_epoch: 0, // activating at zero
            deactivation_epoch: 5,
            ..Delegation::default()
        }];
        // give 2 epochs of cooldown
        let epochs = 7;
        // make boostrap stake smaller than warmup so warmup/cooldownn
        //  increment is always smaller than 1
        let bootstrap = (delegations[0].warmup_cooldown_rate * 100.0 / 2.0) as u64;
        let stake_history =
            create_stake_history_from_delegations(Some(bootstrap), 0..epochs, &delegations);
        let mut max_stake = 0;
        let mut min_stake = 2;

        for epoch in 0..epochs {
            let stake = delegations
                .iter()
                .map(|delegation| delegation.stake(epoch, Some(&stake_history)))
                .sum::<u64>();
            max_stake = max_stake.max(stake);
            min_stake = min_stake.min(stake);
        }
        assert_eq!(max_stake, 2);
        assert_eq!(min_stake, 0);
    }

    #[test]
    fn test_stake_warmup_cooldown() {
        let delegations = [
            Delegation {
                // never deactivates
                stake: 1_000,
                activation_epoch: std::u64::MAX,
                ..Delegation::default()
            },
            Delegation {
                stake: 1_000,
                activation_epoch: 0,
                deactivation_epoch: 9,
                ..Delegation::default()
            },
            Delegation {
                stake: 1_000,
                activation_epoch: 1,
                deactivation_epoch: 6,
                ..Delegation::default()
            },
            Delegation {
                stake: 1_000,
                activation_epoch: 2,
                deactivation_epoch: 5,
                ..Delegation::default()
            },
            Delegation {
                stake: 1_000,
                activation_epoch: 2,
                deactivation_epoch: 4,
                ..Delegation::default()
            },
            Delegation {
                stake: 1_000,
                activation_epoch: 4,
                deactivation_epoch: 4,
                ..Delegation::default()
            },
        ];
        // chosen to ensure that the last activated stake (at 4) finishes
        //  warming up and cooling down
        //  a stake takes 2.0f64.log(1.0 + STAKE_WARMUP_RATE) epochs to warm up or cool down
        //  when all alone, but the above overlap a lot
        let epochs = 20;

        let stake_history = create_stake_history_from_delegations(None, 0..epochs, &delegations);

        let mut prev_total_effective_stake = delegations
            .iter()
            .map(|delegation| delegation.stake(0, Some(&stake_history)))
            .sum::<u64>();

        // uncomment and add ! for fun with graphing
        // eprintln("\n{:8} {:8} {:8}", "   epoch", "   total", "   delta");
        for epoch in 1..epochs {
            let total_effective_stake = delegations
                .iter()
                .map(|delegation| delegation.stake(epoch, Some(&stake_history)))
                .sum::<u64>();

            let delta = if total_effective_stake > prev_total_effective_stake {
                total_effective_stake - prev_total_effective_stake
            } else {
                prev_total_effective_stake - total_effective_stake
            };

            // uncomment and add ! for fun with graphing
            //eprint("{:8} {:8} {:8} ", epoch, total_effective_stake, delta);
            //(0..(total_effective_stake as usize / (stakes.len() * 5))).for_each(|_| eprint("#"));
            //eprintln();

            assert!(
                delta
                    <= ((prev_total_effective_stake as f64 * Config::default().warmup_cooldown_rate) as u64)
                        .max(1)
            );

            prev_total_effective_stake = total_effective_stake;
        }
    }

    #[test]
    fn test_stake_state_redeem_rewards() {
        let mut vote_state = VoteState::default();
        // assume stake.stake() is right
        // bootstrap means fully-vested stake at epoch 0
        let stake_lamports = 1;
        let mut stake = new_stake(
            stake_lamports,
            &Pubkey::default(),
            &vote_state,
            std::u64::MAX,
            &Config::default(),
        );

        // this one can't collect now, credits_observed == vote_state.credits()
        assert_eq!(
            None,
            redeem_stake_rewards(
                0,
                &mut stake,
                &PointValue {
                    rewards: 1_000_000_000,
                    points: 1
                },
                &vote_state,
                None,
                null_tracer(),
                true,
            )
        );

        // put 2 credits in at epoch 0
        vote_state.increment_credits(0, 1);
        vote_state.increment_credits(0, 1);

        // this one should be able to collect exactly 2
        assert_eq!(
            Some((stake_lamports * 2, 0)),
            redeem_stake_rewards(
                0,
                &mut stake,
                &PointValue {
                    rewards: 1,
                    points: 1
                },
                &vote_state,
                None,
                null_tracer(),
                true,
            )
        );

        assert_eq!(
            stake.delegation.stake,
            stake_lamports + (stake_lamports * 2)
        );
        assert_eq!(stake.credits_observed, 2);
    }

    #[test]
    fn test_stake_state_calculate_points_with_typical_values() {
        let mut vote_state = VoteState::default();

        // bootstrap means fully-vested stake at epoch 0 with
        //  10_000_000 SAFE is a big but not unreasaonable stake
        let stake = new_stake(
            native_token::sol_to_lamports(10_000_000f64),
            &Pubkey::default(),
            &vote_state,
            std::u64::MAX,
            &Config::default(),
        );

        // this one can't collect now, credits_observed == vote_state.credits()
        assert_eq!(
            None,
            calculate_stake_rewards(
                0,
                &stake,
                &PointValue {
                    rewards: 1_000_000_000,
                    points: 1
                },
                &vote_state,
                None,
                null_tracer(),
                true,
            )
        );

        let epoch_slots: u128 = 14 * 24 * 3600 * 160;
        // put 193,536,000 credits in at epoch 0, typical for a 14-day epoch
        //  this loop takes a few seconds...
        for _ in 0..epoch_slots {
            vote_state.increment_credits(0, 1);
        }

        // no overflow on points
        assert_eq!(
            u128::from(stake.delegation.stake) * epoch_slots,
            calculate_stake_points(&stake, &vote_state, None, null_tracer())
        );
    }

    #[test]
    fn test_stake_state_calculate_rewards() {
        let mut vote_state = VoteState::default();
        // assume stake.stake() is right
        // bootstrap means fully-vested stake at epoch 0
        let mut stake = new_stake(
            1,
            &Pubkey::default(),
            &vote_state,
            std::u64::MAX,
            &Config::default(),
        );

        // this one can't collect now, credits_observed == vote_state.credits()
        assert_eq!(
            None,
            calculate_stake_rewards(
                0,
                &stake,
                &PointValue {
                    rewards: 1_000_000_000,
                    points: 1
                },
                &vote_state,
                None,
                null_tracer(),
                true,
            )
        );

        // put 2 credits in at epoch 0
        vote_state.increment_credits(0, 1);
        vote_state.increment_credits(0, 1);

        // this one should be able to collect exactly 2
        assert_eq!(
            Some(CalculatedStakeRewards {
                staker_rewards: stake.delegation.stake * 2,
                voter_rewards: 0,
                new_credits_observed: 2,
            }),
            calculate_stake_rewards(
                0,
                &stake,
                &PointValue {
                    rewards: 2,
                    points: 2 // all his
                },
                &vote_state,
                None,
                null_tracer(),
                true,
            )
        );

        stake.credits_observed = 1;
        // this one should be able to collect exactly 1 (already observed one)
        assert_eq!(
            Some(CalculatedStakeRewards {
                staker_rewards: stake.delegation.stake,
                voter_rewards: 0,
                new_credits_observed: 2,
            }),
            calculate_stake_rewards(
                0,
                &stake,
                &PointValue {
                    rewards: 1,
                    points: 1
                },
                &vote_state,
                None,
                null_tracer(),
                true,
            )
        );

        // put 1 credit in epoch 1
        vote_state.increment_credits(1, 1);

        stake.credits_observed = 2;
        // this one should be able to collect the one just added
        assert_eq!(
            Some(CalculatedStakeRewards {
                staker_rewards: stake.delegation.stake,
                voter_rewards: 0,
                new_credits_observed: 3,
            }),
            calculate_stake_rewards(
                1,
                &stake,
                &PointValue {
                    rewards: 2,
                    points: 2
                },
                &vote_state,
                None,
                null_tracer(),
                true,
            )
        );

        // put 1 credit in epoch 2
        vote_state.increment_credits(2, 1);
        // this one should be able to collect 2 now
        assert_eq!(
            Some(CalculatedStakeRewards {
                staker_rewards: stake.delegation.stake * 2,
                voter_rewards: 0,
                new_credits_observed: 4,
            }),
            calculate_stake_rewards(
                2,
                &stake,
                &PointValue {
                    rewards: 2,
                    points: 2
                },
                &vote_state,
                None,
                null_tracer(),
                true,
            )
        );

        stake.credits_observed = 0;
        // this one should be able to collect everything from t=0 a warmed up stake of 2
        // (2 credits at stake of 1) + (1 credit at a stake of 2)
        assert_eq!(
            Some(CalculatedStakeRewards {
                staker_rewards: stake.delegation.stake * 2 // epoch 0
                    + stake.delegation.stake // epoch 1
                    + stake.delegation.stake, // epoch 2
                voter_rewards: 0,
                new_credits_observed: 4,
            }),
            calculate_stake_rewards(
                2,
                &stake,
                &PointValue {
                    rewards: 4,
                    points: 4
                },
                &vote_state,
                None,
                null_tracer(),
                true,
            )
        );

        // same as above, but is a really small commission out of 32 bits,
        //  verify that None comes back on small redemptions where no one gets paid
        vote_state.commission = 1;
        assert_eq!(
            None, // would be Some((0, 2 * 1 + 1 * 2, 4)),
            calculate_stake_rewards(
                2,
                &stake,
                &PointValue {
                    rewards: 4,
                    points: 4
                },
                &vote_state,
                None,
                null_tracer(),
                true,
            )
        );
        vote_state.commission = 99;
        assert_eq!(
            None, // would be Some((0, 2 * 1 + 1 * 2, 4)),
            calculate_stake_rewards(
                2,
                &stake,
                &PointValue {
                    rewards: 4,
                    points: 4
                },
                &vote_state,
                None,
                null_tracer(),
                true,
            )
        );

        // now one with inflation disabled. no one gets paid, but we still need
        // to advance the stake state's credits_observed field to prevent back-
        // paying rewards when inflation is turned on.
        assert_eq!(
            Some(CalculatedStakeRewards {
                staker_rewards: 0,
                voter_rewards: 0,
                new_credits_observed: 4,
            }),
            calculate_stake_rewards(
                2,
                &stake,
                &PointValue {
                    rewards: 0,
                    points: 4
                },
                &vote_state,
                None,
                null_tracer(),
                true,
            )
        );

        // credits_observed remains at previous level when vote_state credits are
        // not advancing and inflation is disabled
        stake.credits_observed = 4;
        assert_eq!(
            Some(CalculatedStakeRewards {
                staker_rewards: 0,
                voter_rewards: 0,
                new_credits_observed: 4,
            }),
            calculate_stake_rewards(
                2,
                &stake,
                &PointValue {
                    rewards: 0,
                    points: 4
                },
                &vote_state,
                None,
                null_tracer(),
                true,
            )
        );

        assert_eq!(
            CalculatedStakePoints {
                points: 0,
                new_credits_observed: 4,
                force_credits_update_with_skipped_reward: false,
            },
            calculate_stake_points_and_credits(&stake, &vote_state, None, null_tracer(), true)
        );

        // credits_observed is auto-rewinded when vote_state credits are assumed to have been
        // recreated
        stake.credits_observed = 1000;
        // this is old behavior; return the pre-recreation (large) credits from stake account
        assert_eq!(
            CalculatedStakePoints {
                points: 0,
                new_credits_observed: 1000,
                force_credits_update_with_skipped_reward: false,
            },
            calculate_stake_points_and_credits(&stake, &vote_state, None, null_tracer(), false)
        );
        // this is new behavior 1; return the post-recreation rewinded credits from the vote account
        assert_eq!(
            CalculatedStakePoints {
                points: 0,
                new_credits_observed: 4,
                force_credits_update_with_skipped_reward: true,
            },
            calculate_stake_points_and_credits(&stake, &vote_state, None, null_tracer(), true)
        );
        // this is new behavior 2; don't hint when credits both from stake and vote are identical
        stake.credits_observed = 4;
        assert_eq!(
            CalculatedStakePoints {
                points: 0,
                new_credits_observed: 4,
                force_credits_update_with_skipped_reward: false,
            },
            calculate_stake_points_and_credits(&stake, &vote_state, None, null_tracer(), true)
        );

        // get rewards and credits observed when not the activation epoch
        vote_state.commission = 0;
        stake.credits_observed = 3;
        stake.delegation.activation_epoch = 1;
        assert_eq!(
            Some(CalculatedStakeRewards {
                staker_rewards: stake.delegation.stake, // epoch 2
                voter_rewards: 0,
                new_credits_observed: 4,
            }),
            calculate_stake_rewards(
                2,
                &stake,
                &PointValue {
                    rewards: 1,
                    points: 1
                },
                &vote_state,
                None,
                null_tracer(),
                true,
            )
        );

        // credits_observed is moved forward for the stake's activation epoch,
        // and no rewards are perceived
        stake.delegation.activation_epoch = 2;
        stake.credits_observed = 3;
        assert_eq!(
            Some(CalculatedStakeRewards {
                staker_rewards: 0,
                voter_rewards: 0,
                new_credits_observed: 4,
            }),
            calculate_stake_rewards(
                2,
                &stake,
                &PointValue {
                    rewards: 1,
                    points: 1
                },
                &vote_state,
                None,
                null_tracer(),
                true,
            )
        );
    }

    fn create_mock_tx_context() -> TransactionContext {
        TransactionContext::new(
            vec![(
                Rent::id(),
                create_account_shared_data_for_test(&Rent::default()),
            )],
            Some(Rent::default()),
            1,
            1,
        )
    }

    #[test]
    fn test_lockup_is_expired() {
        let custodian = solana_sdk::pubkey::new_rand();
        let lockup = Lockup {
            epoch: 1,
            unix_timestamp: 1,
            custodian,
        };
        // neither time
        assert!(lockup.is_in_force(
            &Clock {
                epoch: 0,
                unix_timestamp: 0,
                ..Clock::default()
            },
            None
        ));
        // not timestamp
        assert!(lockup.is_in_force(
            &Clock {
                epoch: 2,
                unix_timestamp: 0,
                ..Clock::default()
            },
            None
        ));
        // not epoch
        assert!(lockup.is_in_force(
            &Clock {
                epoch: 0,
                unix_timestamp: 2,
                ..Clock::default()
            },
            None
        ));
        // both, no custodian
        assert!(!lockup.is_in_force(
            &Clock {
                epoch: 1,
                unix_timestamp: 1,
                ..Clock::default()
            },
            None
        ));
        // neither, but custodian
        assert!(!lockup.is_in_force(
            &Clock {
                epoch: 0,
                unix_timestamp: 0,
                ..Clock::default()
            },
            Some(&custodian),
        ));
    }

    #[test]
    #[ignore]
    #[should_panic]
    fn test_dbg_stake_minimum_balance() {
        let minimum_balance = Rent::default().minimum_balance(StakeState::size_of());
        panic!(
            "stake minimum_balance: {} lamports, {} SAFE",
            minimum_balance,
            minimum_balance as f64 / solana_sdk::native_token::LAMPORTS_PER_SAFE as f64
        );
    }

    #[test]
    fn test_calculate_lamports_per_byte_year() {
        let rent = Rent::default();
        let data_len = 200u64;
        let rent_exempt_reserve = rent.minimum_balance(data_len as usize);
        assert_eq!(
            calculate_split_rent_exempt_reserve(rent_exempt_reserve, data_len, data_len),
            rent_exempt_reserve
        );

        let larger_data = 4008u64;
        let larger_rent_exempt_reserve = rent.minimum_balance(larger_data as usize);
        assert_eq!(
            calculate_split_rent_exempt_reserve(rent_exempt_reserve, data_len, larger_data),
            larger_rent_exempt_reserve
        );
        assert_eq!(
            calculate_split_rent_exempt_reserve(larger_rent_exempt_reserve, larger_data, data_len),
            rent_exempt_reserve
        );

        let even_larger_data = solana_sdk::system_instruction::MAX_PERMITTED_DATA_LENGTH;
        let even_larger_rent_exempt_reserve = rent.minimum_balance(even_larger_data as usize);
        assert_eq!(
            calculate_split_rent_exempt_reserve(rent_exempt_reserve, data_len, even_larger_data),
            even_larger_rent_exempt_reserve
        );
        assert_eq!(
            calculate_split_rent_exempt_reserve(
                even_larger_rent_exempt_reserve,
                even_larger_data,
                data_len
            ),
            rent_exempt_reserve
        );
    }

    #[test]
    fn test_things_can_merge() {
        let mut transaction_context =
            TransactionContext::new(Vec::new(), Some(Rent::default()), 1, 1);
        let invoke_context = InvokeContext::new_mock(&mut transaction_context, &[]);
        let good_stake = Stake {
            credits_observed: 4242,
            delegation: Delegation {
                voter_pubkey: Pubkey::new_unique(),
                stake: 424242424242,
                activation_epoch: 42,
                ..Delegation::default()
            },
        };

        let identical = good_stake;
        assert!(
            MergeKind::active_stakes_can_merge(&invoke_context, &good_stake, &identical).is_ok()
        );

        let bad_credits_observed = Stake {
            credits_observed: good_stake.credits_observed + 1,
            ..good_stake
        };
        assert!(MergeKind::active_stakes_can_merge(
            &invoke_context,
            &good_stake,
            &bad_credits_observed
        )
        .is_err());

        let good_delegation = good_stake.delegation;
        let different_stake_ok = Delegation {
            stake: good_delegation.stake + 1,
            ..good_delegation
        };
        assert!(MergeKind::active_delegations_can_merge(
            &invoke_context,
            &good_delegation,
            &different_stake_ok
        )
        .is_ok());

        let different_activation_epoch_ok = Delegation {
            activation_epoch: good_delegation.activation_epoch + 1,
            ..good_delegation
        };
        assert!(MergeKind::active_delegations_can_merge(
            &invoke_context,
            &good_delegation,
            &different_activation_epoch_ok
        )
        .is_ok());

        let bad_voter = Delegation {
            voter_pubkey: Pubkey::new_unique(),
            ..good_delegation
        };
        assert!(MergeKind::active_delegations_can_merge(
            &invoke_context,
            &good_delegation,
            &bad_voter
        )
        .is_err());

        let bad_warmup_cooldown_rate = Delegation {
            warmup_cooldown_rate: good_delegation.warmup_cooldown_rate + f64::EPSILON,
            ..good_delegation
        };
        assert!(MergeKind::active_delegations_can_merge(
            &invoke_context,
            &good_delegation,
            &bad_warmup_cooldown_rate
        )
        .is_err());
        assert!(MergeKind::active_delegations_can_merge(
            &invoke_context,
            &bad_warmup_cooldown_rate,
            &good_delegation
        )
        .is_err());

        let bad_deactivation_epoch = Delegation {
            deactivation_epoch: 43,
            ..good_delegation
        };
        assert!(MergeKind::active_delegations_can_merge(
            &invoke_context,
            &good_delegation,
            &bad_deactivation_epoch
        )
        .is_err());
        assert!(MergeKind::active_delegations_can_merge(
            &invoke_context,
            &bad_deactivation_epoch,
            &good_delegation
        )
        .is_err());
    }

    #[test]
    fn test_metas_can_merge() {
        let mut transaction_context =
            TransactionContext::new(Vec::new(), Some(Rent::default()), 1, 1);
        let invoke_context = InvokeContext::new_mock(&mut transaction_context, &[]);
        // Identical Metas can merge
        assert!(MergeKind::metas_can_merge(
            &invoke_context,
            &Meta::default(),
            &Meta::default(),
            &Clock::default()
        )
        .is_ok());

        let mismatched_rent_exempt_reserve_ok = Meta {
            rent_exempt_reserve: 42,
            ..Meta::default()
        };
        assert_ne!(
            mismatched_rent_exempt_reserve_ok.rent_exempt_reserve,
            Meta::default().rent_exempt_reserve,
        );
        assert!(MergeKind::metas_can_merge(
            &invoke_context,
            &Meta::default(),
            &mismatched_rent_exempt_reserve_ok,
            &Clock::default()
        )
        .is_ok());
        assert!(MergeKind::metas_can_merge(
            &invoke_context,
            &mismatched_rent_exempt_reserve_ok,
            &Meta::default(),
            &Clock::default()
        )
        .is_ok());

        let mismatched_authorized_fails = Meta {
            authorized: Authorized {
                staker: Pubkey::new_unique(),
                withdrawer: Pubkey::new_unique(),
            },
            ..Meta::default()
        };
        assert_ne!(
            mismatched_authorized_fails.authorized,
            Meta::default().authorized,
        );
        assert!(MergeKind::metas_can_merge(
            &invoke_context,
            &Meta::default(),
            &mismatched_authorized_fails,
            &Clock::default()
        )
        .is_err());
        assert!(MergeKind::metas_can_merge(
            &invoke_context,
            &mismatched_authorized_fails,
            &Meta::default(),
            &Clock::default()
        )
        .is_err());

        let lockup1_timestamp = 42;
        let lockup2_timestamp = 4242;
        let lockup1_epoch = 4;
        let lockup2_epoch = 42;
        let metas_with_lockup1 = Meta {
            lockup: Lockup {
                unix_timestamp: lockup1_timestamp,
                epoch: lockup1_epoch,
                custodian: Pubkey::new_unique(),
            },
            ..Meta::default()
        };
        let metas_with_lockup2 = Meta {
            lockup: Lockup {
                unix_timestamp: lockup2_timestamp,
                epoch: lockup2_epoch,
                custodian: Pubkey::new_unique(),
            },
            ..Meta::default()
        };

        // Mismatched lockups fail when both in force
        assert_ne!(metas_with_lockup1.lockup, Meta::default().lockup);
        assert!(MergeKind::metas_can_merge(
            &invoke_context,
            &metas_with_lockup1,
            &metas_with_lockup2,
            &Clock::default()
        )
        .is_err());
        assert!(MergeKind::metas_can_merge(
            &invoke_context,
            &metas_with_lockup2,
            &metas_with_lockup1,
            &Clock::default()
        )
        .is_err());

        let clock = Clock {
            epoch: lockup1_epoch + 1,
            unix_timestamp: lockup1_timestamp + 1,
            ..Clock::default()
        };

        // Mismatched lockups fail when either in force
        assert_ne!(metas_with_lockup1.lockup, Meta::default().lockup);
        assert!(MergeKind::metas_can_merge(
            &invoke_context,
            &metas_with_lockup1,
            &metas_with_lockup2,
            &clock
        )
        .is_err());
        assert!(MergeKind::metas_can_merge(
            &invoke_context,
            &metas_with_lockup2,
            &metas_with_lockup1,
            &clock
        )
        .is_err());

        let clock = Clock {
            epoch: lockup2_epoch + 1,
            unix_timestamp: lockup2_timestamp + 1,
            ..Clock::default()
        };

        // Mismatched lockups succeed when both expired
        assert_ne!(metas_with_lockup1.lockup, Meta::default().lockup);
        assert!(MergeKind::metas_can_merge(
            &invoke_context,
            &metas_with_lockup1,
            &metas_with_lockup2,
            &clock
        )
        .is_ok());
        assert!(MergeKind::metas_can_merge(
            &invoke_context,
            &metas_with_lockup2,
            &metas_with_lockup1,
            &clock
        )
        .is_ok());
    }

    #[test]
    fn test_merge_kind_get_if_mergeable() {
        let mut transaction_context =
            TransactionContext::new(Vec::new(), Some(Rent::default()), 1, 1);
        let invoke_context = InvokeContext::new_mock(&mut transaction_context, &[]);
        let authority_pubkey = Pubkey::new_unique();
        let initial_lamports = 4242424242;
        let rent = Rent::default();
        let rent_exempt_reserve = rent.minimum_balance(StakeState::size_of());
        let stake_lamports = rent_exempt_reserve + initial_lamports;

        let meta = Meta {
            rent_exempt_reserve,
            ..Meta::auto(&authority_pubkey)
        };
        let mut stake_account = AccountSharedData::new_data_with_space(
            stake_lamports,
            &StakeState::Uninitialized,
            StakeState::size_of(),
            &id(),
        )
        .expect("stake_account");
        let mut clock = Clock::default();
        let mut stake_history = StakeHistory::default();

        // Uninitialized state fails
        assert_eq!(
            MergeKind::get_if_mergeable(
                &invoke_context,
                &stake_account.state().unwrap(),
                stake_account.lamports(),
                &clock,
                &stake_history
            )
            .unwrap_err(),
            InstructionError::InvalidAccountData
        );

        // RewardsPool state fails
        stake_account.set_state(&StakeState::RewardsPool).unwrap();
        assert_eq!(
            MergeKind::get_if_mergeable(
                &invoke_context,
                &stake_account.state().unwrap(),
                stake_account.lamports(),
                &clock,
                &stake_history
            )
            .unwrap_err(),
            InstructionError::InvalidAccountData
        );

        // Initialized state succeeds
        stake_account
            .set_state(&StakeState::Initialized(meta))
            .unwrap();
        assert_eq!(
            MergeKind::get_if_mergeable(
                &invoke_context,
                &stake_account.state().unwrap(),
                stake_account.lamports(),
                &clock,
                &stake_history
            )
            .unwrap(),
            MergeKind::Inactive(meta, stake_lamports)
        );

        clock.epoch = 0;
        let mut effective = 2 * initial_lamports;
        let mut activating = 0;
        let mut deactivating = 0;
        stake_history.add(
            clock.epoch,
            StakeHistoryEntry {
                effective,
                activating,
                deactivating,
            },
        );

        clock.epoch += 1;
        activating = initial_lamports;
        stake_history.add(
            clock.epoch,
            StakeHistoryEntry {
                effective,
                activating,
                deactivating,
            },
        );

        let stake = Stake {
            delegation: Delegation {
                stake: initial_lamports,
                activation_epoch: 1,
                deactivation_epoch: 5,
                ..Delegation::default()
            },
            ..Stake::default()
        };
        stake_account
            .set_state(&StakeState::Stake(meta, stake))
            .unwrap();
        // activation_epoch succeeds
        assert_eq!(
            MergeKind::get_if_mergeable(
                &invoke_context,
                &stake_account.state().unwrap(),
                stake_account.lamports(),
                &clock,
                &stake_history
            )
            .unwrap(),
            MergeKind::ActivationEpoch(meta, stake),
        );

        // all paritially activated, transient epochs fail
        loop {
            clock.epoch += 1;
            let delta =
                activating.min((effective as f64 * stake.delegation.warmup_cooldown_rate) as u64);
            effective += delta;
            activating -= delta;
            stake_history.add(
                clock.epoch,
                StakeHistoryEntry {
                    effective,
                    activating,
                    deactivating,
                },
            );
            if activating == 0 {
                break;
            }
            assert_eq!(
                MergeKind::get_if_mergeable(
                    &invoke_context,
                    &stake_account.state().unwrap(),
                    stake_account.lamports(),
                    &clock,
                    &stake_history
                )
                .unwrap_err(),
                InstructionError::from(StakeError::MergeTransientStake),
            );
        }

        // all epochs for which we're fully active succeed
        while clock.epoch < stake.delegation.deactivation_epoch - 1 {
            clock.epoch += 1;
            stake_history.add(
                clock.epoch,
                StakeHistoryEntry {
                    effective,
                    activating,
                    deactivating,
                },
            );
            assert_eq!(
                MergeKind::get_if_mergeable(
                    &invoke_context,
                    &stake_account.state().unwrap(),
                    stake_account.lamports(),
                    &clock,
                    &stake_history
                )
                .unwrap(),
                MergeKind::FullyActive(meta, stake),
            );
        }

        clock.epoch += 1;
        deactivating = stake.delegation.stake;
        stake_history.add(
            clock.epoch,
            StakeHistoryEntry {
                effective,
                activating,
                deactivating,
            },
        );
        // deactivation epoch fails, fully transient/deactivating
        assert_eq!(
            MergeKind::get_if_mergeable(
                &invoke_context,
                &stake_account.state().unwrap(),
                stake_account.lamports(),
                &clock,
                &stake_history
            )
            .unwrap_err(),
            InstructionError::from(StakeError::MergeTransientStake),
        );

        // all transient, deactivating epochs fail
        loop {
            clock.epoch += 1;
            let delta =
                deactivating.min((effective as f64 * stake.delegation.warmup_cooldown_rate) as u64);
            effective -= delta;
            deactivating -= delta;
            stake_history.add(
                clock.epoch,
                StakeHistoryEntry {
                    effective,
                    activating,
                    deactivating,
                },
            );
            if deactivating == 0 {
                break;
            }
            assert_eq!(
                MergeKind::get_if_mergeable(
                    &invoke_context,
                    &stake_account.state().unwrap(),
                    stake_account.lamports(),
                    &clock,
                    &stake_history
                )
                .unwrap_err(),
                InstructionError::from(StakeError::MergeTransientStake),
            );
        }

        // first fully-deactivated epoch succeeds
        assert_eq!(
            MergeKind::get_if_mergeable(
                &invoke_context,
                &stake_account.state().unwrap(),
                stake_account.lamports(),
                &clock,
                &stake_history
            )
            .unwrap(),
            MergeKind::Inactive(meta, stake_lamports),
        );
    }

    #[test]
    fn test_merge_kind_merge() {
        let mut transaction_context =
            TransactionContext::new(Vec::new(), Some(Rent::default()), 1, 1);
        let invoke_context = InvokeContext::new_mock(&mut transaction_context, &[]);
        let clock = Clock::default();
        let lamports = 424242;
        let meta = Meta {
            rent_exempt_reserve: 42,
            ..Meta::default()
        };
        let stake = Stake {
            delegation: Delegation {
                stake: 4242,
                ..Delegation::default()
            },
            ..Stake::default()
        };
        let inactive = MergeKind::Inactive(Meta::default(), lamports);
        let activation_epoch = MergeKind::ActivationEpoch(meta, stake);
        let fully_active = MergeKind::FullyActive(meta, stake);

        assert_eq!(
            inactive
                .clone()
                .merge(&invoke_context, inactive.clone(), &clock)
                .unwrap(),
            None
        );
        assert_eq!(
            inactive
                .clone()
                .merge(&invoke_context, activation_epoch.clone(), &clock)
                .unwrap(),
            None
        );
        assert!(inactive
            .clone()
            .merge(&invoke_context, fully_active.clone(), &clock)
            .is_err());
        assert!(activation_epoch
            .clone()
            .merge(&invoke_context, fully_active.clone(), &clock)
            .is_err());
        assert!(fully_active
            .clone()
            .merge(&invoke_context, inactive.clone(), &clock)
            .is_err());
        assert!(fully_active
            .clone()
            .merge(&invoke_context, activation_epoch.clone(), &clock)
            .is_err());

        let new_state = activation_epoch
            .clone()
            .merge(&invoke_context, inactive, &clock)
            .unwrap()
            .unwrap();
        let delegation = new_state.delegation().unwrap();
        assert_eq!(delegation.stake, stake.delegation.stake + lamports);

        let new_state = activation_epoch
            .clone()
            .merge(&invoke_context, activation_epoch, &clock)
            .unwrap()
            .unwrap();
        let delegation = new_state.delegation().unwrap();
        assert_eq!(
            delegation.stake,
            2 * stake.delegation.stake + meta.rent_exempt_reserve
        );

        let new_state = fully_active
            .clone()
            .merge(&invoke_context, fully_active, &clock)
            .unwrap()
            .unwrap();
        let delegation = new_state.delegation().unwrap();
        assert_eq!(delegation.stake, 2 * stake.delegation.stake);
    }

    #[test]
    fn test_active_stake_merge() {
        let mut transaction_context = create_mock_tx_context();
        let invoke_context = InvokeContext::new_mock(&mut transaction_context, &[]);
        let clock = Clock::default();
        let delegation_a = 4_242_424_242u64;
        let delegation_b = 6_200_000_000u64;
        let credits_a = 124_521_000u64;
        let rent_exempt_reserve = 227_000_000u64;
        let meta = Meta {
            rent_exempt_reserve,
            ..Meta::default()
        };
        let stake_a = Stake {
            delegation: Delegation {
                stake: delegation_a,
                ..Delegation::default()
            },
            credits_observed: credits_a,
        };
        let stake_b = Stake {
            delegation: Delegation {
                stake: delegation_b,
                ..Delegation::default()
            },
            credits_observed: credits_a,
        };

        // activating stake merge, match credits observed
        let activation_epoch_a = MergeKind::ActivationEpoch(meta, stake_a);
        let activation_epoch_b = MergeKind::ActivationEpoch(meta, stake_b);
        let new_stake = activation_epoch_a
            .merge(&invoke_context, activation_epoch_b, &clock)
            .unwrap()
            .unwrap()
            .stake()
            .unwrap();
        assert_eq!(new_stake.credits_observed, credits_a);
        assert_eq!(
            new_stake.delegation.stake,
            delegation_a + delegation_b + rent_exempt_reserve
        );

        // active stake merge, match credits observed
        let fully_active_a = MergeKind::FullyActive(meta, stake_a);
        let fully_active_b = MergeKind::FullyActive(meta, stake_b);
        let new_stake = fully_active_a
            .merge(&invoke_context, fully_active_b, &clock)
            .unwrap()
            .unwrap()
            .stake()
            .unwrap();
        assert_eq!(new_stake.credits_observed, credits_a);
        assert_eq!(new_stake.delegation.stake, delegation_a + delegation_b);

        // activating stake merge, unmatched credits observed
        let credits_b = 125_124_521u64;
        let stake_b = Stake {
            delegation: Delegation {
                stake: delegation_b,
                ..Delegation::default()
            },
            credits_observed: credits_b,
        };
        let activation_epoch_a = MergeKind::ActivationEpoch(meta, stake_a);
        let activation_epoch_b = MergeKind::ActivationEpoch(meta, stake_b);
        let new_stake = activation_epoch_a
            .merge(&invoke_context, activation_epoch_b, &clock)
            .unwrap()
            .unwrap()
            .stake()
            .unwrap();
        assert_eq!(
            new_stake.credits_observed,
            (credits_a * delegation_a + credits_b * (delegation_b + rent_exempt_reserve))
                / (delegation_a + delegation_b + rent_exempt_reserve)
                + 1
        );
        assert_eq!(
            new_stake.delegation.stake,
            delegation_a + delegation_b + rent_exempt_reserve
        );

        // active stake merge, unmatched credits observed
        let fully_active_a = MergeKind::FullyActive(meta, stake_a);
        let fully_active_b = MergeKind::FullyActive(meta, stake_b);
        let new_stake = fully_active_a
            .merge(&invoke_context, fully_active_b, &clock)
            .unwrap()
            .unwrap()
            .stake()
            .unwrap();
        assert_eq!(
            new_stake.credits_observed,
            (credits_a * delegation_a + credits_b * delegation_b) / (delegation_a + delegation_b)
                + 1
        );
        assert_eq!(new_stake.delegation.stake, delegation_a + delegation_b);

        // active stake merge, unmatched credits observed, no need to ceiling the calculation
        let delegation = 1_000_000u64;
        let credits_a = 200_000_000u64;
        let credits_b = 100_000_000u64;
        let rent_exempt_reserve = 227_000_000u64;
        let meta = Meta {
            rent_exempt_reserve,
            ..Meta::default()
        };
        let stake_a = Stake {
            delegation: Delegation {
                stake: delegation,
                ..Delegation::default()
            },
            credits_observed: credits_a,
        };
        let stake_b = Stake {
            delegation: Delegation {
                stake: delegation,
                ..Delegation::default()
            },
            credits_observed: credits_b,
        };
        let fully_active_a = MergeKind::FullyActive(meta, stake_a);
        let fully_active_b = MergeKind::FullyActive(meta, stake_b);
        let new_stake = fully_active_a
            .merge(&invoke_context, fully_active_b, &clock)
            .unwrap()
            .unwrap()
            .stake()
            .unwrap();
        assert_eq!(
            new_stake.credits_observed,
            (credits_a * delegation + credits_b * delegation) / (delegation + delegation)
        );
        assert_eq!(new_stake.delegation.stake, delegation * 2);
    }

    prop_compose! {
        pub fn sum_within(max: u64)(total in 1..max)
            (intermediate in 1..total, total in Just(total))
            -> (u64, u64) {
                (intermediate, total - intermediate)
        }
    }

    proptest! {
        #[test]
        fn test_stake_weighted_credits_observed(
            (credits_a, credits_b) in sum_within(u64::MAX),
            (delegation_a, delegation_b) in sum_within(u64::MAX),
        ) {
            let stake = Stake {
                delegation: Delegation {
                    stake: delegation_a,
                    ..Delegation::default()
                },
                credits_observed: credits_a
            };
            let credits_observed = stake_weighted_credits_observed(
                &stake,
                delegation_b,
                credits_b,
            ).unwrap();

            // calculated credits observed should always be between the credits of a and b
            if credits_a < credits_b {
                assert!(credits_a < credits_observed);
                assert!(credits_observed <= credits_b);
            } else {
                assert!(credits_b <= credits_observed);
                assert!(credits_observed <= credits_a);
            }

            // the difference of the combined weighted credits and the separate weighted credits
            // should be 1 or 0
            let weighted_credits_total = credits_observed as u128 * (delegation_a + delegation_b) as u128;
            let weighted_credits_a = credits_a as u128 * delegation_a as u128;
            let weighted_credits_b = credits_b as u128 * delegation_b as u128;
            let raw_diff = weighted_credits_total - (weighted_credits_a + weighted_credits_b);
            let credits_observed_diff = raw_diff / (delegation_a + delegation_b) as u128;
            assert!(credits_observed_diff <= 1);
        }
    }
}