0g-chain/x/auction/keeper/auctions.go
rhuairahrighairigh bc1a6a68e0 bugfix
2020-05-12 01:06:32 +01:00

575 lines
20 KiB
Go

package keeper
import (
"fmt"
"time"
sdk "github.com/cosmos/cosmos-sdk/types"
sdkerrors "github.com/cosmos/cosmos-sdk/types/errors"
"github.com/cosmos/cosmos-sdk/x/supply"
"github.com/kava-labs/kava/x/auction/types"
)
// StartSurplusAuction starts a new surplus (forward) auction.
func (k Keeper) StartSurplusAuction(ctx sdk.Context, seller string, lot sdk.Coin, bidDenom string) (uint64, error) {
auction := types.NewSurplusAuction(
seller,
lot,
bidDenom,
types.DistantFuture,
)
// NOTE: for the duration of the auction the auction module account holds the lot
err := k.supplyKeeper.SendCoinsFromModuleToModule(ctx, seller, types.ModuleName, sdk.NewCoins(lot))
if err != nil {
return 0, err
}
auctionID, err := k.StoreNewAuction(ctx, auction)
if err != nil {
return 0, err
}
ctx.EventManager().EmitEvent(
sdk.NewEvent(
types.EventTypeAuctionStart,
sdk.NewAttribute(types.AttributeKeyAuctionID, fmt.Sprintf("%d", auction.GetID())),
sdk.NewAttribute(types.AttributeKeyAuctionType, auction.GetType()),
sdk.NewAttribute(types.AttributeKeyBid, auction.Bid.String()),
sdk.NewAttribute(types.AttributeKeyLot, auction.Lot.String()),
),
)
return auctionID, nil
}
// StartDebtAuction starts a new debt (reverse) auction.
func (k Keeper) StartDebtAuction(ctx sdk.Context, buyer string, bid sdk.Coin, initialLot sdk.Coin, debt sdk.Coin) (uint64, error) {
auction := types.NewDebtAuction(
buyer,
bid,
initialLot,
types.DistantFuture,
debt,
)
// This auction type mints coins at close. Need to check module account has minting privileges to avoid potential err in endblocker.
macc := k.supplyKeeper.GetModuleAccount(ctx, buyer)
if !macc.HasPermission(supply.Minter) {
panic(fmt.Errorf("module '%s' does not have '%s' permission", buyer, supply.Minter))
}
// NOTE: for the duration of the auction the auction module account holds the debt
err := k.supplyKeeper.SendCoinsFromModuleToModule(ctx, buyer, types.ModuleName, sdk.NewCoins(debt))
if err != nil {
return 0, err
}
auctionID, err := k.StoreNewAuction(ctx, auction)
if err != nil {
return 0, err
}
ctx.EventManager().EmitEvent(
sdk.NewEvent(
types.EventTypeAuctionStart,
sdk.NewAttribute(types.AttributeKeyAuctionID, fmt.Sprintf("%d", auction.GetID())),
sdk.NewAttribute(types.AttributeKeyAuctionType, auction.GetType()),
sdk.NewAttribute(types.AttributeKeyBid, auction.Bid.String()),
sdk.NewAttribute(types.AttributeKeyLot, auction.Lot.String()),
),
)
return auctionID, nil
}
// StartCollateralAuction starts a new collateral (2-phase) auction.
func (k Keeper) StartCollateralAuction(
ctx sdk.Context, seller string, lot, maxBid sdk.Coin,
lotReturnAddrs []sdk.AccAddress, lotReturnWeights []sdk.Int, debt sdk.Coin,
) (uint64, error) {
weightedAddresses, err := types.NewWeightedAddresses(lotReturnAddrs, lotReturnWeights)
if err != nil {
return 0, err
}
auction := types.NewCollateralAuction(
seller,
lot,
types.DistantFuture,
maxBid,
weightedAddresses,
debt,
)
// NOTE: for the duration of the auction the auction module account holds the debt and the lot
err = k.supplyKeeper.SendCoinsFromModuleToModule(ctx, seller, types.ModuleName, sdk.NewCoins(lot))
if err != nil {
return 0, err
}
err = k.supplyKeeper.SendCoinsFromModuleToModule(ctx, seller, types.ModuleName, sdk.NewCoins(debt))
if err != nil {
return 0, err
}
auctionID, err := k.StoreNewAuction(ctx, auction)
if err != nil {
return 0, err
}
ctx.EventManager().EmitEvent(
sdk.NewEvent(
types.EventTypeAuctionStart,
sdk.NewAttribute(types.AttributeKeyAuctionID, fmt.Sprintf("%d", auction.GetID())),
sdk.NewAttribute(types.AttributeKeyAuctionType, auction.GetType()),
sdk.NewAttribute(types.AttributeKeyBid, auction.Bid.String()),
sdk.NewAttribute(types.AttributeKeyLot, auction.Lot.String()),
sdk.NewAttribute(types.AttributeKeyMaxBid, auction.MaxBid.String()),
),
)
return auctionID, nil
}
// PlaceBid places a bid on any auction.
func (k Keeper) PlaceBid(ctx sdk.Context, auctionID uint64, bidder sdk.AccAddress, newAmount sdk.Coin) error {
auction, found := k.GetAuction(ctx, auctionID)
if !found {
return sdkerrors.Wrapf(types.ErrAuctionNotFound, "%d", auctionID)
}
// validation common to all auctions
if ctx.BlockTime().After(auction.GetEndTime()) {
return sdkerrors.Wrapf(types.ErrAuctionHasExpired, "%d", auctionID)
}
// move coins and return updated auction
var (
err error
updatedAuction types.Auction
)
switch a := auction.(type) {
case types.SurplusAuction:
updatedAuction, err = k.PlaceBidSurplus(ctx, a, bidder, newAmount)
case types.DebtAuction:
updatedAuction, err = k.PlaceBidDebt(ctx, a, bidder, newAmount)
case types.CollateralAuction:
if !a.IsReversePhase() {
updatedAuction, err = k.PlaceForwardBidCollateral(ctx, a, bidder, newAmount)
} else {
updatedAuction, err = k.PlaceReverseBidCollateral(ctx, a, bidder, newAmount)
}
default:
err = sdkerrors.Wrap(types.ErrUnrecognizedAuctionType, auction.GetType())
}
if err != nil {
return err
}
k.SetAuction(ctx, updatedAuction)
return nil
}
// PlaceBidSurplus places a forward bid on a surplus auction, moving coins and returning the updated auction.
func (k Keeper) PlaceBidSurplus(ctx sdk.Context, a types.SurplusAuction, bidder sdk.AccAddress, bid sdk.Coin) (types.SurplusAuction, error) {
// Validate new bid
if bid.Denom != a.Bid.Denom {
return a, sdkerrors.Wrapf(types.ErrInvalidBidDenom, "%s ≠ %s)", bid.Denom, a.Bid.Denom)
}
minNewBidAmt := a.Bid.Amount.Add( // new bids must be some % greater than old bid, and at least 1 larger to avoid replacing an old bid at no cost
sdk.MaxInt(
sdk.NewInt(1),
sdk.NewDecFromInt(a.Bid.Amount).Mul(k.GetParams(ctx).IncrementSurplus).RoundInt(),
),
)
if bid.Amount.LT(minNewBidAmt) {
return a, sdkerrors.Wrapf(types.ErrBidTooSmall, "%s ≤ %s%s", bid, minNewBidAmt, a.Bid.Denom)
}
// New bidder pays back old bidder
// Catch edge cases of a bidder replacing their own bid, or the amount being zero (sending zero coins produces meaningless send events).
if !bidder.Equals(a.Bidder) && !a.Bid.IsZero() {
err := k.supplyKeeper.SendCoinsFromAccountToModule(ctx, bidder, types.ModuleName, sdk.NewCoins(a.Bid))
if err != nil {
return a, err
}
err = k.supplyKeeper.SendCoinsFromModuleToAccount(ctx, types.ModuleName, a.Bidder, sdk.NewCoins(a.Bid))
if err != nil {
return a, err
}
}
// Increase in bid is burned
err := k.supplyKeeper.SendCoinsFromAccountToModule(ctx, bidder, a.Initiator, sdk.NewCoins(bid.Sub(a.Bid)))
if err != nil {
return a, err
}
err = k.supplyKeeper.BurnCoins(ctx, a.Initiator, sdk.NewCoins(bid.Sub(a.Bid)))
if err != nil {
return a, err
}
// Update Auction
a.Bidder = bidder
a.Bid = bid
if !a.HasReceivedBids {
a.MaxEndTime = ctx.BlockTime().Add(k.GetParams(ctx).MaxAuctionDuration) // set maximum ending time on receipt of first bid
}
a.EndTime = earliestTime(ctx.BlockTime().Add(k.GetParams(ctx).BidDuration), a.MaxEndTime) // increment timeout, up to MaxEndTime
a.HasReceivedBids = true
ctx.EventManager().EmitEvent(
sdk.NewEvent(
types.EventTypeAuctionBid,
sdk.NewAttribute(types.AttributeKeyAuctionID, fmt.Sprintf("%d", a.ID)),
sdk.NewAttribute(types.AttributeKeyBidder, a.Bidder.String()),
sdk.NewAttribute(types.AttributeKeyBid, a.Bid.String()),
sdk.NewAttribute(types.AttributeKeyEndTime, fmt.Sprintf("%d", a.EndTime.Unix())),
),
)
return a, nil
}
// PlaceForwardBidCollateral places a forward bid on a collateral auction, moving coins and returning the updated auction.
func (k Keeper) PlaceForwardBidCollateral(ctx sdk.Context, a types.CollateralAuction, bidder sdk.AccAddress, bid sdk.Coin) (types.CollateralAuction, error) {
// Validate new bid
if bid.Denom != a.Bid.Denom {
return a, sdkerrors.Wrapf(types.ErrInvalidBidDenom, "%s ≠ %s", bid.Denom, a.Bid.Denom)
}
if a.IsReversePhase() {
panic("cannot place forward bid on auction in reverse phase")
}
minNewBidAmt := a.Bid.Amount.Add( // new bids must be some % greater than old bid, and at least 1 larger to avoid replacing an old bid at no cost
sdk.MaxInt(
sdk.NewInt(1),
sdk.NewDecFromInt(a.Bid.Amount).Mul(k.GetParams(ctx).IncrementCollateral).RoundInt(),
),
)
minNewBidAmt = sdk.MinInt(minNewBidAmt, a.MaxBid.Amount) // allow new bids to hit MaxBid even though it may be less than the increment %
if bid.Amount.LT(minNewBidAmt) {
return a, sdkerrors.Wrapf(types.ErrBidTooSmall, "%s ≤ %s%s", bid, minNewBidAmt, a.Bid.Denom)
}
if a.MaxBid.IsLT(bid) {
return a, sdkerrors.Wrapf(types.ErrBidTooLarge, "%s > %s", bid, a.MaxBid)
}
// New bidder pays back old bidder
// Catch edge cases of a bidder replacing their own bid, and the amount being zero (sending zero coins produces meaningless send events).
if !bidder.Equals(a.Bidder) && !a.Bid.IsZero() {
err := k.supplyKeeper.SendCoinsFromAccountToModule(ctx, bidder, types.ModuleName, sdk.NewCoins(a.Bid))
if err != nil {
return a, err
}
err = k.supplyKeeper.SendCoinsFromModuleToAccount(ctx, types.ModuleName, a.Bidder, sdk.NewCoins(a.Bid))
if err != nil {
return a, err
}
}
// Increase in bid sent to auction initiator
bidIncrement := bid.Sub(a.Bid)
err := k.supplyKeeper.SendCoinsFromAccountToModule(ctx, bidder, a.Initiator, sdk.NewCoins(bidIncrement))
if err != nil {
return a, err
}
// Debt coins are sent to liquidator (until there is no CorrespondingDebt left). Amount sent is equal to bidIncrement (or whatever is left if < bidIncrement).
if a.CorrespondingDebt.IsPositive() {
debtAmountToReturn := sdk.MinInt(bidIncrement.Amount, a.CorrespondingDebt.Amount)
debtToReturn := sdk.NewCoin(a.CorrespondingDebt.Denom, debtAmountToReturn)
err = k.supplyKeeper.SendCoinsFromModuleToModule(ctx, types.ModuleName, a.Initiator, sdk.NewCoins(debtToReturn))
if err != nil {
return a, err
}
a.CorrespondingDebt = a.CorrespondingDebt.Sub(debtToReturn) // debtToReturn will always be ≤ a.CorrespondingDebt from the MinInt above
}
// Update Auction
a.Bidder = bidder
a.Bid = bid
if !a.HasReceivedBids {
a.MaxEndTime = ctx.BlockTime().Add(k.GetParams(ctx).MaxAuctionDuration) // set maximum ending time on receipt of first bid
}
a.EndTime = earliestTime(ctx.BlockTime().Add(k.GetParams(ctx).BidDuration), a.MaxEndTime) // increment timeout, up to MaxEndTime
a.HasReceivedBids = true
ctx.EventManager().EmitEvent(
sdk.NewEvent(
types.EventTypeAuctionBid,
sdk.NewAttribute(types.AttributeKeyAuctionID, fmt.Sprintf("%d", a.ID)),
sdk.NewAttribute(types.AttributeKeyBidder, a.Bidder.String()),
sdk.NewAttribute(types.AttributeKeyBid, a.Bid.String()),
sdk.NewAttribute(types.AttributeKeyEndTime, fmt.Sprintf("%d", a.EndTime.Unix())),
),
)
return a, nil
}
// PlaceReverseBidCollateral places a reverse bid on a collateral auction, moving coins and returning the updated auction.
func (k Keeper) PlaceReverseBidCollateral(ctx sdk.Context, a types.CollateralAuction, bidder sdk.AccAddress, lot sdk.Coin) (types.CollateralAuction, error) {
// Validate new bid
if lot.Denom != a.Lot.Denom {
return a, sdkerrors.Wrapf(types.ErrInvalidLotDenom, lot.Denom, a.Lot.Denom)
}
if !a.IsReversePhase() {
panic("cannot place reverse bid on auction in forward phase")
}
maxNewLotAmt := a.Lot.Amount.Sub( // new lot must be some % less than old lot, and at least 1 smaller to avoid replacing an old bid at no cost
sdk.MaxInt(
sdk.NewInt(1),
sdk.NewDecFromInt(a.Lot.Amount).Mul(k.GetParams(ctx).IncrementCollateral).RoundInt(),
),
)
if lot.Amount.GT(maxNewLotAmt) {
return a, sdkerrors.Wrapf(types.ErrLotTooLarge, "%s > %s%s", lot, maxNewLotAmt, a.Lot.Denom)
}
if lot.IsNegative() {
return a, sdkerrors.Wrapf(types.ErrLotTooSmall, "%s ≤ %s%s", lot, sdk.ZeroInt(), a.Lot.Denom)
}
// New bidder pays back old bidder
// Catch edge cases of a bidder replacing their own bid
if !bidder.Equals(a.Bidder) {
err := k.supplyKeeper.SendCoinsFromAccountToModule(ctx, bidder, types.ModuleName, sdk.NewCoins(a.Bid))
if err != nil {
return a, err
}
err = k.supplyKeeper.SendCoinsFromModuleToAccount(ctx, types.ModuleName, a.Bidder, sdk.NewCoins(a.Bid))
if err != nil {
return a, err
}
}
// Decrease in lot is sent to weighted addresses (normally the CDP depositors)
// Note: splitting an integer amount across weighted buckets results in small errors.
lotPayouts, err := splitCoinIntoWeightedBuckets(a.Lot.Sub(lot), a.LotReturns.Weights)
if err != nil {
return a, err
}
for i, payout := range lotPayouts {
// if the payout amount is 0, don't send 0 coins
if !payout.IsPositive() {
continue
}
err = k.supplyKeeper.SendCoinsFromModuleToAccount(ctx, types.ModuleName, a.LotReturns.Addresses[i], sdk.NewCoins(payout))
if err != nil {
return a, err
}
}
// Update Auction
a.Bidder = bidder
a.Lot = lot
if !a.HasReceivedBids {
a.MaxEndTime = ctx.BlockTime().Add(k.GetParams(ctx).MaxAuctionDuration) // set maximum ending time on receipt of first bid
}
a.EndTime = earliestTime(ctx.BlockTime().Add(k.GetParams(ctx).BidDuration), a.MaxEndTime) // increment timeout, up to MaxEndTime
a.HasReceivedBids = true
ctx.EventManager().EmitEvent(
sdk.NewEvent(
types.EventTypeAuctionBid,
sdk.NewAttribute(types.AttributeKeyAuctionID, fmt.Sprintf("%d", a.ID)),
sdk.NewAttribute(types.AttributeKeyBidder, a.Bidder.String()),
sdk.NewAttribute(types.AttributeKeyLot, a.Lot.String()),
sdk.NewAttribute(types.AttributeKeyEndTime, fmt.Sprintf("%d", a.EndTime.Unix())),
),
)
return a, nil
}
// PlaceBidDebt places a reverse bid on a debt auction, moving coins and returning the updated auction.
func (k Keeper) PlaceBidDebt(ctx sdk.Context, a types.DebtAuction, bidder sdk.AccAddress, lot sdk.Coin) (types.DebtAuction, error) {
// Validate new bid
if lot.Denom != a.Lot.Denom {
return a, sdkerrors.Wrapf(types.ErrInvalidLotDenom, lot.Denom, a.Lot.Denom)
}
maxNewLotAmt := a.Lot.Amount.Sub( // new lot must be some % less than old lot, and at least 1 smaller to avoid replacing an old bid at no cost
sdk.MaxInt(
sdk.NewInt(1),
sdk.NewDecFromInt(a.Lot.Amount).Mul(k.GetParams(ctx).IncrementDebt).RoundInt(),
),
)
if lot.Amount.GT(maxNewLotAmt) {
return a, sdkerrors.Wrapf(types.ErrLotTooLarge, "%s > %s%s", lot, maxNewLotAmt, a.Lot.Denom)
}
if lot.IsNegative() {
return a, sdkerrors.Wrapf(types.ErrLotTooSmall, "%s ≤ %s%s", lot, sdk.ZeroInt(), a.Lot.Denom)
}
// New bidder pays back old bidder
// Catch edge cases of a bidder replacing their own bid
if !bidder.Equals(a.Bidder) {
err := k.supplyKeeper.SendCoinsFromAccountToModule(ctx, bidder, types.ModuleName, sdk.NewCoins(a.Bid))
if err != nil {
return a, err
}
err = k.supplyKeeper.SendCoinsFromModuleToAccount(ctx, types.ModuleName, a.Bidder, sdk.NewCoins(a.Bid))
if err != nil {
return a, err
}
}
// Debt coins are sent to liquidator the first time a bid is placed. Amount sent is equal to min of Bid and amount of debt.
if a.Bidder.Equals(supply.NewModuleAddress(a.Initiator)) {
debtAmountToReturn := sdk.MinInt(a.Bid.Amount, a.CorrespondingDebt.Amount)
debtToReturn := sdk.NewCoin(a.CorrespondingDebt.Denom, debtAmountToReturn)
err := k.supplyKeeper.SendCoinsFromModuleToModule(ctx, types.ModuleName, a.Initiator, sdk.NewCoins(debtToReturn))
if err != nil {
return a, err
}
a.CorrespondingDebt = a.CorrespondingDebt.Sub(debtToReturn) // debtToReturn will always be ≤ a.CorrespondingDebt from the MinInt above
}
// Update Auction
a.Bidder = bidder
a.Lot = lot
if !a.HasReceivedBids {
a.MaxEndTime = ctx.BlockTime().Add(k.GetParams(ctx).MaxAuctionDuration) // set maximum ending time on receipt of first bid
}
a.EndTime = earliestTime(ctx.BlockTime().Add(k.GetParams(ctx).BidDuration), a.MaxEndTime) // increment timeout, up to MaxEndTime
a.HasReceivedBids = true
ctx.EventManager().EmitEvent(
sdk.NewEvent(
types.EventTypeAuctionBid,
sdk.NewAttribute(types.AttributeKeyAuctionID, fmt.Sprintf("%d", a.ID)),
sdk.NewAttribute(types.AttributeKeyBidder, a.Bidder.String()),
sdk.NewAttribute(types.AttributeKeyLot, a.Lot.String()),
sdk.NewAttribute(types.AttributeKeyEndTime, fmt.Sprintf("%d", a.EndTime.Unix())),
),
)
return a, nil
}
// CloseAuction closes an auction and distributes funds to the highest bidder.
func (k Keeper) CloseAuction(ctx sdk.Context, auctionID uint64) error {
auction, found := k.GetAuction(ctx, auctionID)
if !found {
return sdkerrors.Wrapf(types.ErrAuctionNotFound, "%d", auctionID)
}
if ctx.BlockTime().Before(auction.GetEndTime()) {
return sdkerrors.Wrapf(types.ErrAuctionHasNotExpired, "block time %s, auction end time %s", ctx.BlockTime().UTC(), auction.GetEndTime().UTC())
}
// payout to the last bidder
switch auc := auction.(type) {
case types.SurplusAuction:
if err := k.PayoutSurplusAuction(ctx, auc); err != nil {
return err
}
case types.DebtAuction:
if err := k.PayoutDebtAuction(ctx, auc); err != nil {
return err
}
case types.CollateralAuction:
if err := k.PayoutCollateralAuction(ctx, auc); err != nil {
return err
}
default:
return sdkerrors.Wrap(types.ErrUnrecognizedAuctionType, auc.GetType())
}
k.DeleteAuction(ctx, auctionID)
ctx.EventManager().EmitEvent(
sdk.NewEvent(
types.EventTypeAuctionClose,
sdk.NewAttribute(types.AttributeKeyAuctionID, fmt.Sprintf("%d", auction.GetID())),
sdk.NewAttribute(types.AttributeKeyCloseBlock, fmt.Sprintf("%d", ctx.BlockHeight())),
),
)
return nil
}
// PayoutDebtAuction pays out the proceeds for a debt auction, first minting the coins.
func (k Keeper) PayoutDebtAuction(ctx sdk.Context, a types.DebtAuction) error {
// create the coins that are needed to pay off the debt
err := k.supplyKeeper.MintCoins(ctx, a.Initiator, sdk.NewCoins(a.Lot))
if err != nil {
panic(fmt.Errorf("could not mint coins: %w", err))
}
// send the new coins from the initiator module to the bidder
err = k.supplyKeeper.SendCoinsFromModuleToAccount(ctx, a.Initiator, a.Bidder, sdk.NewCoins(a.Lot))
if err != nil {
return err
}
// if there is remaining debt, return it to the calling module to manage
if a.CorrespondingDebt.IsPositive() {
err = k.supplyKeeper.SendCoinsFromModuleToModule(ctx, types.ModuleName, a.Initiator, sdk.NewCoins(a.CorrespondingDebt))
if err != nil {
return err
}
}
return nil
}
// PayoutSurplusAuction pays out the proceeds for a surplus auction.
func (k Keeper) PayoutSurplusAuction(ctx sdk.Context, a types.SurplusAuction) error {
// Send the tokens from the auction module account where they are being managed to the bidder who won the auction
err := k.supplyKeeper.SendCoinsFromModuleToAccount(ctx, types.ModuleName, a.Bidder, sdk.NewCoins(a.Lot))
if err != nil {
return err
}
return nil
}
// PayoutCollateralAuction pays out the proceeds for a collateral auction.
func (k Keeper) PayoutCollateralAuction(ctx sdk.Context, a types.CollateralAuction) error {
// Send the tokens from the auction module account where they are being managed to the bidder who won the auction
err := k.supplyKeeper.SendCoinsFromModuleToAccount(ctx, types.ModuleName, a.Bidder, sdk.NewCoins(a.Lot))
if err != nil {
return err
}
// if there is remaining debt after the auction, send it back to the initiating module for management
if a.CorrespondingDebt.IsPositive() {
err = k.supplyKeeper.SendCoinsFromModuleToModule(ctx, types.ModuleName, a.Initiator, sdk.NewCoins(a.CorrespondingDebt))
if err != nil {
return err
}
}
return nil
}
// CloseExpiredAuctions finds all auctions that are past (or at) their ending times and closes them, paying out to the highest bidder.
func (k Keeper) CloseExpiredAuctions(ctx sdk.Context) error {
var expiredAuctions []uint64
k.IterateAuctionsByTime(ctx, ctx.BlockTime(), func(id uint64) bool {
expiredAuctions = append(expiredAuctions, id)
return false
})
// Note: iteration and auction closing are in separate loops as db should not be modified during iteration // TODO is this correct? gov modifies during iteration
for _, id := range expiredAuctions {
if err := k.CloseAuction(ctx, id); err != nil {
return err
}
}
return nil
}
// earliestTime returns the earliest of two times.
func earliestTime(t1, t2 time.Time) time.Time {
if t1.Before(t2) {
return t1
}
return t2 // also returned if times are equal
}
// splitCoinIntoWeightedBuckets divides up some amount of coins according to some weights.
func splitCoinIntoWeightedBuckets(coin sdk.Coin, buckets []sdk.Int) ([]sdk.Coin, error) {
amounts := splitIntIntoWeightedBuckets(coin.Amount, buckets)
result := make([]sdk.Coin, len(amounts))
for i, a := range amounts {
result[i] = sdk.NewCoin(coin.Denom, a)
}
return result, nil
}