Add wei support in bank keeper (#386)

## Describe your changes and provide context
Add two new bank keeper functions that allow sub-usei (i.e. wei)
sending, where 1 usei = 10^12 wei:
```
SendCoinsAndWei(ctx sdk.Context, from sdk.AccAddress, to sdk.AccAddress, customEscrow sdk.AccAddress, denom string, amt sdk.Int, wei sdk.Int) error
GetWeiBalance(ctx sdk.Context, addr sdk.AccAddress) sdk.Int
```
Any usei that is split as a result of wei sending will be stored in an
escrow account, which can either be one that's specified by the caller
or a default global escrow module account.

## Testing performed to validate your change
unit test & local integration with sei-chain

x/bank/keeper/keeper_test.go

@@ -76,6 +76,7 @@ func (suite *IntegrationTestSuite) initKeepersWithmAccPerms(blockedAddrs map[str
 	appCodec := simapp.MakeTestEncodingConfig().Marshaler
 
 	maccPerms[holder] = nil
+	maccPerms[types.WeiEscrowName] = nil
 	maccPerms[authtypes.Burner] = []string{authtypes.Burner}
 	maccPerms[authtypes.Minter] = []string{authtypes.Minter}
 	maccPerms[multiPerm] = []string{authtypes.Burner, authtypes.Minter, authtypes.Staking}
@@ -108,6 +109,55 @@ func (suite *IntegrationTestSuite) SetupTest() {
 	suite.queryClient = queryClient
 }
 
+func (suite *IntegrationTestSuite) TestSendCoinsAndWei() {
+	ctx := suite.ctx
+	require := suite.Require()
+	authKeeper, keeper := suite.initKeepersWithmAccPerms(make(map[string]bool))
+	amt := sdk.NewCoins(sdk.NewCoin(sdk.DefaultBondDenom, sdk.NewInt(100)))
+	require.NoError(keeper.MintCoins(ctx, authtypes.Minter, amt))
+	addr1 := sdk.AccAddress([]byte("addr1_______________"))
+	addr2 := sdk.AccAddress([]byte("addr2_______________"))
+	addr3 := sdk.AccAddress([]byte("addr3_______________"))
+	require.NoError(keeper.SendCoinsFromModuleToAccount(ctx, authtypes.Minter, addr1, amt))
+	// should no-op if sending zero
+	require.NoError(keeper.SendCoinsAndWei(ctx, addr1, addr2, nil, sdk.DefaultBondDenom, sdk.ZeroInt(), sdk.ZeroInt()))
+	require.Equal(sdk.ZeroInt(), keeper.GetWeiBalance(ctx, addr1))
+	require.Equal(sdk.ZeroInt(), keeper.GetWeiBalance(ctx, addr2))
+	require.Equal(sdk.NewInt(100), keeper.GetBalance(ctx, addr1, sdk.DefaultBondDenom).Amount)
+	require.Equal(sdk.ZeroInt(), keeper.GetBalance(ctx, addr2, sdk.DefaultBondDenom).Amount)
+	require.Equal(sdk.ZeroInt(), keeper.GetBalance(ctx, authKeeper.GetModuleAddress(types.WeiEscrowName), sdk.DefaultBondDenom).Amount)
+	// should just do usei send if wei is zero
+	require.NoError(keeper.SendCoinsAndWei(ctx, addr1, addr3, nil, sdk.DefaultBondDenom, sdk.NewInt(50), sdk.ZeroInt()))
+	require.Equal(sdk.ZeroInt(), keeper.GetWeiBalance(ctx, addr1))
+	require.Equal(sdk.ZeroInt(), keeper.GetWeiBalance(ctx, addr3))
+	require.Equal(sdk.NewInt(50), keeper.GetBalance(ctx, addr1, sdk.DefaultBondDenom).Amount)
+	require.Equal(sdk.NewInt(50), keeper.GetBalance(ctx, addr3, sdk.DefaultBondDenom).Amount)
+	require.Equal(sdk.ZeroInt(), keeper.GetBalance(ctx, authKeeper.GetModuleAddress(types.WeiEscrowName), sdk.DefaultBondDenom).Amount)
+	// should return error if wei amount overflows
+	require.Error(keeper.SendCoinsAndWei(ctx, addr1, addr2, nil, sdk.DefaultBondDenom, sdk.ZeroInt(), sdk.NewInt(1_000_000_000_000)))
+	// sender gets escrowed one usei, recipient does not get redeemed
+	require.NoError(keeper.SendCoinsAndWei(ctx, addr1, addr2, nil, sdk.DefaultBondDenom, sdk.NewInt(1), sdk.NewInt(1)))
+	require.Equal(sdk.NewInt(999_999_999_999), keeper.GetWeiBalance(ctx, addr1))
+	require.Equal(sdk.OneInt(), keeper.GetWeiBalance(ctx, addr2))
+	require.Equal(sdk.NewInt(48), keeper.GetBalance(ctx, addr1, sdk.DefaultBondDenom).Amount)
+	require.Equal(sdk.OneInt(), keeper.GetBalance(ctx, addr2, sdk.DefaultBondDenom).Amount)
+	require.Equal(sdk.OneInt(), keeper.GetBalance(ctx, authKeeper.GetModuleAddress(types.WeiEscrowName), sdk.DefaultBondDenom).Amount)
+	// sender does not get escrowed due to sufficient wei balance, recipient does not get redeemed
+	require.NoError(keeper.SendCoinsAndWei(ctx, addr1, addr3, nil, sdk.DefaultBondDenom, sdk.NewInt(1), sdk.NewInt(999_999_999_999)))
+	require.Equal(sdk.ZeroInt(), keeper.GetWeiBalance(ctx, addr1))
+	require.Equal(sdk.NewInt(999_999_999_999), keeper.GetWeiBalance(ctx, addr3))
+	require.Equal(sdk.NewInt(47), keeper.GetBalance(ctx, addr1, sdk.DefaultBondDenom).Amount)
+	require.Equal(sdk.NewInt(51), keeper.GetBalance(ctx, addr3, sdk.DefaultBondDenom).Amount)
+	require.Equal(sdk.OneInt(), keeper.GetBalance(ctx, authKeeper.GetModuleAddress(types.WeiEscrowName), sdk.DefaultBondDenom).Amount)
+	// sender gets escrowed and recipient gets redeemed
+	require.NoError(keeper.SendCoinsAndWei(ctx, addr1, addr3, nil, sdk.DefaultBondDenom, sdk.NewInt(1), sdk.NewInt(2)))
+	require.Equal(sdk.NewInt(999_999_999_998), keeper.GetWeiBalance(ctx, addr1))
+	require.Equal(sdk.NewInt(1), keeper.GetWeiBalance(ctx, addr3))
+	require.Equal(sdk.NewInt(45), keeper.GetBalance(ctx, addr1, sdk.DefaultBondDenom).Amount)
+	require.Equal(sdk.NewInt(53), keeper.GetBalance(ctx, addr3, sdk.DefaultBondDenom).Amount)
+	require.Equal(sdk.OneInt(), keeper.GetBalance(ctx, authKeeper.GetModuleAddress(types.WeiEscrowName), sdk.DefaultBondDenom).Amount)
+}
+
 func (suite *IntegrationTestSuite) TestSupply() {
 	ctx := suite.ctx
 

x/bank/keeper/send.go

@@ -1,7 +1,10 @@
 package keeper
 
 import (
+	"errors"
+
 	"github.com/cosmos/cosmos-sdk/codec"
+	"github.com/cosmos/cosmos-sdk/store/prefix"
 	"github.com/cosmos/cosmos-sdk/telemetry"
 	sdk "github.com/cosmos/cosmos-sdk/types"
 	sdkerrors "github.com/cosmos/cosmos-sdk/types/errors"
@@ -17,6 +20,7 @@ type SendKeeper interface {
 	InputOutputCoins(ctx sdk.Context, inputs []types.Input, outputs []types.Output) error
 	SendCoins(ctx sdk.Context, fromAddr sdk.AccAddress, toAddr sdk.AccAddress, amt sdk.Coins) error
 	SendCoinsWithoutAccCreation(ctx sdk.Context, fromAddr sdk.AccAddress, toAddr sdk.AccAddress, amt sdk.Coins) error
+	SendCoinsAndWei(ctx sdk.Context, from sdk.AccAddress, to sdk.AccAddress, customEscrow sdk.AccAddress, denom string, amt sdk.Int, wei sdk.Int) error
 
 	GetParams(ctx sdk.Context) types.Params
 	SetParams(ctx sdk.Context, params types.Params)
@@ -28,6 +32,7 @@ type SendKeeper interface {
 }
 
 var _ SendKeeper = (*BaseSendKeeper)(nil)
+var MaxWeiBalance sdk.Int = sdk.NewInt(1_000_000_000_000)
 
 // BaseSendKeeper only allows transfers between accounts without the possibility of
 // creating coins. It implements the SendKeeper interface.
@@ -275,6 +280,20 @@ func (k BaseSendKeeper) setBalance(ctx sdk.Context, addr sdk.AccAddress, balance
 	return nil
 }
 
+func (k BaseSendKeeper) setWeiBalance(ctx sdk.Context, addr sdk.AccAddress, amt sdk.Int) error {
+	store := prefix.NewStore(ctx.KVStore(k.storeKey), types.WeiBalancesPrefix)
+	if amt.IsZero() {
+		store.Delete(addr)
+		return nil
+	}
+	val, err := amt.Marshal()
+	if err != nil {
+		return err
+	}
+	store.Set(addr, val)
+	return nil
+}
+
 // IsSendEnabledCoins checks the coins provide and returns an ErrSendDisabled if
 // any of the coins are not configured for sending.  Returns nil if sending is enabled
 // for all provided coin
@@ -297,3 +316,61 @@ func (k BaseSendKeeper) IsSendEnabledCoin(ctx sdk.Context, coin sdk.Coin) bool {
 func (k BaseSendKeeper) BlockedAddr(addr sdk.AccAddress) bool {
 	return k.blockedAddrs[addr.String()]
 }
+
+func (k BaseSendKeeper) SendCoinsAndWei(ctx sdk.Context, from sdk.AccAddress, to sdk.AccAddress, customEscrow sdk.AccAddress, denom string, amt sdk.Int, wei sdk.Int) error {
+	if wei.Equal(sdk.ZeroInt()) {
+		if amt.Equal(sdk.ZeroInt()) {
+			return nil
+		}
+		return k.SendCoinsWithoutAccCreation(ctx, from, to, sdk.NewCoins(sdk.NewCoin(denom, amt)))
+	}
+	if wei.GTE(MaxWeiBalance) {
+		return errors.New("cannot send more than 10^12 wei")
+	}
+	escrow := customEscrow
+	if escrow == nil {
+		escrow = k.ak.GetModuleAddress(types.WeiEscrowName)
+	}
+	currentWeiBalanceFrom := k.GetWeiBalance(ctx, from)
+	postWeiBalanceFrom := currentWeiBalanceFrom.Sub(wei)
+	if postWeiBalanceFrom.GTE(sdk.ZeroInt()) {
+		if err := k.setWeiBalance(ctx, from, postWeiBalanceFrom); err != nil {
+			return err
+		}
+	} else {
+		if err := k.setWeiBalance(ctx, from, MaxWeiBalance.Add(postWeiBalanceFrom)); err != nil {
+			// postWeiBalanceFrom is negative
+			return err
+		}
+		// need to send one sei to escrow because wei balance is insufficient
+		if err := k.SendCoinsWithoutAccCreation(ctx, from, escrow, sdk.NewCoins(sdk.NewCoin(denom, sdk.OneInt()))); err != nil {
+			return err
+		}
+	}
+	currentWeiBalanceTo := k.GetWeiBalance(ctx, to)
+	postWeiBalanceTo := currentWeiBalanceTo.Add(wei)
+	if postWeiBalanceTo.LT(MaxWeiBalance) {
+		if err := k.setWeiBalance(ctx, to, postWeiBalanceTo); err != nil {
+			return err
+		}
+	} else {
+		if err := k.setWeiBalance(ctx, to, postWeiBalanceTo.Sub(MaxWeiBalance)); err != nil {
+			return err
+		}
+		// need to redeem one sei from escrow because wei balance overflowed
+		one := sdk.NewCoins(sdk.NewCoin(denom, sdk.OneInt()))
+		if err := k.SendCoinsWithoutAccCreation(ctx, escrow, to, one); err != nil {
+			if sdkerrors.ErrInsufficientFunds.Is(err) && customEscrow != nil {
+				// custom escrow does not have enough balance to redeem. Try the global escrow instead
+				if err := k.SendCoinsWithoutAccCreation(ctx, k.ak.GetModuleAddress(types.WeiEscrowName), to, one); err != nil {
+					return err
+				}
+			}
+			return err
+		}
+	}
+	if amt.GT(sdk.ZeroInt()) {
+		return k.SendCoinsWithoutAccCreation(ctx, from, to, sdk.NewCoins(sdk.NewCoin(denom, amt)))
+	}
+	return nil
+}

x/bank/keeper/view.go

@@ -26,6 +26,7 @@ type ViewKeeper interface {
 	GetBalance(ctx sdk.Context, addr sdk.AccAddress, denom string) sdk.Coin
 	LockedCoins(ctx sdk.Context, addr sdk.AccAddress) sdk.Coins
 	SpendableCoins(ctx sdk.Context, addr sdk.AccAddress) sdk.Coins
+	GetWeiBalance(ctx sdk.Context, addr sdk.AccAddress) sdk.Int
 
 	IterateAccountBalances(ctx sdk.Context, addr sdk.AccAddress, cb func(coin sdk.Coin) (stop bool))
 	IterateAllBalances(ctx sdk.Context, cb func(address sdk.AccAddress, coin sdk.Coin) (stop bool))
@@ -232,3 +233,17 @@ func (k BaseViewKeeper) getAccountStore(ctx sdk.Context, addr sdk.AccAddress) pr
 
 	return prefix.NewStore(store, types.CreateAccountBalancesPrefix(addr))
 }
+
+func (k BaseViewKeeper) GetWeiBalance(ctx sdk.Context, addr sdk.AccAddress) sdk.Int {
+	store := prefix.NewStore(ctx.KVStore(k.storeKey), types.WeiBalancesPrefix)
+	val := store.Get(addr)
+	if val == nil {
+		return sdk.ZeroInt()
+	}
+	res := new(sdk.Int)
+	if err := res.Unmarshal(val); err != nil {
+		// should never happen
+		panic(err)
+	}
+	return *res
+}

x/bank/types/key.go

@@ -21,10 +21,13 @@ const (
 
 	// QuerierRoute defines the module's query routing key
 	QuerierRoute = ModuleName
+
+	WeiEscrowName = "weiescrow"
 )
 
 // KVStore keys
 var (
+	WeiBalancesPrefix = []byte{0x04}
 	// BalancesPrefix is the prefix for the account balances store. We use a byte
 	// (instead of `[]byte("balances")` to save some disk space).
 	DeferredCachePrefix = []byte{0x03}