0g-chain/x/incentive/keeper/rewards_borrow.go

package keeper

import (
	"fmt"

	sdk "github.com/cosmos/cosmos-sdk/types"
	sdkerrors "github.com/cosmos/cosmos-sdk/types/errors"

	hardtypes "github.com/kava-labs/kava/x/hard/types"
	"github.com/kava-labs/kava/x/incentive/types"
)

// AccumulateHardBorrowRewards calculates new rewards to distribute this block and updates the global indexes to reflect this.
// The provided rewardPeriod must be valid to avoid panics in calculating time durations.
func (k Keeper) AccumulateHardBorrowRewards(ctx sdk.Context, rewardPeriod types.MultiRewardPeriod) {

	previousAccrualTime, found := k.GetPreviousHardBorrowRewardAccrualTime(ctx, rewardPeriod.CollateralType)
	if !found {
		previousAccrualTime = ctx.BlockTime()
	}

	indexes, found := k.GetHardBorrowRewardIndexes(ctx, rewardPeriod.CollateralType)
	if !found {
		indexes = types.RewardIndexes{}
	}

	acc := types.NewAccumulator(previousAccrualTime, indexes)

	totalSource := k.getHardBorrowTotalSourceShares(ctx, rewardPeriod.CollateralType)

	acc.Accumulate(rewardPeriod, totalSource, ctx.BlockTime())

	k.SetPreviousHardBorrowRewardAccrualTime(ctx, rewardPeriod.CollateralType, acc.PreviousAccumulationTime)
	if len(acc.Indexes) > 0 {
		// the store panics when setting empty or nil indexes
		k.SetHardBorrowRewardIndexes(ctx, rewardPeriod.CollateralType, acc.Indexes)
	}
}

// getHardBorrowTotalSourceShares fetches the sum of all source shares for a borrow reward.
// In the case of hard borrow, this is the total borrowed divided by the borrow interest factor.
// This give the "pre interest" value of the total borrowed.
func (k Keeper) getHardBorrowTotalSourceShares(ctx sdk.Context, denom string) sdk.Dec {
	totalBorrowedCoins, found := k.hardKeeper.GetBorrowedCoins(ctx)
	if !found {
		// assume no coins have been borrowed
		totalBorrowedCoins = sdk.NewCoins()
	}
	totalBorrowed := totalBorrowedCoins.AmountOf(denom)

	interestFactor, found := k.hardKeeper.GetBorrowInterestFactor(ctx, denom)
	if !found {
		// assume nothing has been borrowed so the factor starts at it's default value
		interestFactor = sdk.OneDec()
	}

	// return borrowed/factor to get the "pre interest" value of the current total borrowed
	return totalBorrowed.ToDec().Quo(interestFactor)
}

// InitializeHardBorrowReward initializes the borrow-side of a hard liquidity provider claim
// by creating the claim and setting the borrow reward factor index
func (k Keeper) InitializeHardBorrowReward(ctx sdk.Context, borrow hardtypes.Borrow) {
	claim, found := k.GetHardLiquidityProviderClaim(ctx, borrow.Borrower)
	if !found {
		claim = types.NewHardLiquidityProviderClaim(borrow.Borrower, sdk.Coins{}, nil, nil)
	}

	var borrowRewardIndexes types.MultiRewardIndexes
	for _, coin := range borrow.Amount {
		globalRewardIndexes, found := k.GetHardBorrowRewardIndexes(ctx, coin.Denom)
		if !found {
			globalRewardIndexes = types.RewardIndexes{}
		}
		borrowRewardIndexes = borrowRewardIndexes.With(coin.Denom, globalRewardIndexes)
	}

	claim.BorrowRewardIndexes = borrowRewardIndexes
	k.SetHardLiquidityProviderClaim(ctx, claim)
}

// SynchronizeHardBorrowReward updates the claim object by adding any accumulated rewards
// and updating the reward index value
func (k Keeper) SynchronizeHardBorrowReward(ctx sdk.Context, borrow hardtypes.Borrow) {
	claim, found := k.GetHardLiquidityProviderClaim(ctx, borrow.Borrower)
	if !found {
		return
	}

	for _, coin := range borrow.Amount {
		globalRewardIndexes, found := k.GetHardBorrowRewardIndexes(ctx, coin.Denom)
		if !found {
			// The global factor is only not found if
			// - the borrowed denom has not started accumulating rewards yet (either there is no reward specified in params, or the reward start time hasn't been hit)
			// - OR it was wrongly deleted from state (factors should never be removed while unsynced claims exist)
			// If not found we could either skip this sync, or assume the global factor is zero.
			// Skipping will avoid storing unnecessary factors in the claim for non rewarded denoms.
			// And in the event a global factor is wrongly deleted, it will avoid this function panicking when calculating rewards.
			continue
		}

		userRewardIndexes, found := claim.BorrowRewardIndexes.Get(coin.Denom)
		if !found {
			// Normally the reward indexes should always be found.
			// But if a denom was not rewarded then becomes rewarded (ie a reward period is added to params), then the indexes will be missing from claims for that borrowed denom.
			// So given the reward period was just added, assume the starting value for any global reward indexes, which is an empty slice.
			userRewardIndexes = types.RewardIndexes{}
		}

		newRewards, err := k.CalculateRewards(userRewardIndexes, globalRewardIndexes, coin.Amount.ToDec())
		if err != nil {
			// Global reward factors should never decrease, as it would lead to a negative update to claim.Rewards.
			// This panics if a global reward factor decreases or disappears between the old and new indexes.
			panic(fmt.Sprintf("corrupted global reward indexes found: %v", err))
		}

		claim.Reward = claim.Reward.Add(newRewards...)
		claim.BorrowRewardIndexes = claim.BorrowRewardIndexes.With(coin.Denom, globalRewardIndexes)
	}
	k.SetHardLiquidityProviderClaim(ctx, claim)
}

// UpdateHardBorrowIndexDenoms adds any new borrow denoms to the claim's borrow reward index
func (k Keeper) UpdateHardBorrowIndexDenoms(ctx sdk.Context, borrow hardtypes.Borrow) {
	claim, found := k.GetHardLiquidityProviderClaim(ctx, borrow.Borrower)
	if !found {
		claim = types.NewHardLiquidityProviderClaim(borrow.Borrower, sdk.Coins{}, nil, nil)
	}

	borrowDenoms := getDenoms(borrow.Amount)
	borrowRewardIndexDenoms := claim.BorrowRewardIndexes.GetCollateralTypes()

	borrowRewardIndexes := claim.BorrowRewardIndexes

	// Create a new multi-reward index in the claim for every new borrow denom
	uniqueBorrowDenoms := setDifference(borrowDenoms, borrowRewardIndexDenoms)

	for _, denom := range uniqueBorrowDenoms {
		globalBorrowRewardIndexes, found := k.GetHardBorrowRewardIndexes(ctx, denom)
		if !found {
			globalBorrowRewardIndexes = types.RewardIndexes{}
		}
		borrowRewardIndexes = borrowRewardIndexes.With(denom, globalBorrowRewardIndexes)
	}

	// Delete multi-reward index from claim if the collateral type is no longer borrowed
	uniqueBorrowRewardDenoms := setDifference(borrowRewardIndexDenoms, borrowDenoms)

	for _, denom := range uniqueBorrowRewardDenoms {
		borrowRewardIndexes = borrowRewardIndexes.RemoveRewardIndex(denom)
	}

	claim.BorrowRewardIndexes = borrowRewardIndexes
	k.SetHardLiquidityProviderClaim(ctx, claim)
}

// CalculateRewards computes how much rewards should have accrued to a reward source (eg a user's hard borrowed btc amount)
// between two index values.
//
// oldIndex is normally the index stored on a claim, newIndex the current global value, and sourceShares a hard borrowed/supplied amount.
//
// It returns an error if newIndexes does not contain all CollateralTypes from oldIndexes, or if any value of oldIndex.RewardFactor > newIndex.RewardFactor.
// This should never happen, as it would mean that a global reward index has decreased in value, or that a global reward index has been deleted from state.
func (k Keeper) CalculateRewards(oldIndexes, newIndexes types.RewardIndexes, sourceShares sdk.Dec) (sdk.Coins, error) {
	// check for missing CollateralType's
	for _, oldIndex := range oldIndexes {
		if newIndex, found := newIndexes.Get(oldIndex.CollateralType); !found {
			return nil, sdkerrors.Wrapf(types.ErrDecreasingRewardFactor, "old: %v, new: %v", oldIndex, newIndex)
		}
	}
	var reward sdk.Coins
	for _, newIndex := range newIndexes {
		oldFactor, found := oldIndexes.Get(newIndex.CollateralType)
		if !found {
			oldFactor = sdk.ZeroDec()
		}

		rewardAmount, err := k.CalculateSingleReward(oldFactor, newIndex.RewardFactor, sourceShares)
		if err != nil {
			return nil, err
		}

		reward = reward.Add(
			sdk.NewCoin(newIndex.CollateralType, rewardAmount),
		)
	}
	return reward, nil
}

// CalculateSingleReward computes how much rewards should have accrued to a reward source (eg a user's btcb-a cdp principal)
// between two index values.
//
// oldIndex is normally the index stored on a claim, newIndex the current global value, and sourceShares a cdp principal amount.
//
// Returns an error if oldIndex > newIndex. This should never happen, as it would mean that a global reward index has decreased in value,
// or that a global reward index has been deleted from state.
func (k Keeper) CalculateSingleReward(oldIndex, newIndex, sourceShares sdk.Dec) (sdk.Int, error) {
	increase := newIndex.Sub(oldIndex)
	if increase.IsNegative() {
		return sdk.Int{}, sdkerrors.Wrapf(types.ErrDecreasingRewardFactor, "old: %v, new: %v", oldIndex, newIndex)
	}
	reward := increase.Mul(sourceShares).RoundInt()
	return reward, nil
}