[Stablestake]: Dynamic Redemption Rate Implementation (#832)

* add redemption rate

* add tests

* fix

* update

* fix

x/stablestake/keeper/begin_blocker.go

@@ -16,6 +16,8 @@ func (k Keeper) BeginBlocker(ctx sdk.Context) {
 	if epochPosition == 0 { // if epoch has passed
 		rate := k.InterestRateComputation(ctx)
 		params.InterestRate = rate
+
+		params.RedemptionRate = k.GetRedemptionRate(ctx)
 		k.SetParams(ctx, params)
 	}
 	k.SetInterest(ctx, uint64(ctx.BlockHeight()), types.InterestBlock{InterestRate: params.InterestRate, BlockTime: ctx.BlockTime().Unix(), BlockHeight: uint64(ctx.BlockHeight())})

x/stablestake/keeper/msg_server_bond.go

@@ -15,6 +15,7 @@ func (k msgServer) Bond(goCtx context.Context, msg *types.MsgBond) (*types.MsgBo
 
 	params := k.GetParams(ctx)
 	creator := sdk.MustAccAddressFromBech32(msg.Creator)
+	redemptionRate := k.GetRedemptionRate(ctx)
 
 	depositDenom := k.GetDepositDenom(ctx)
 	depositCoin := sdk.NewCoin(depositDenom, msg.Amount)
@@ -24,10 +25,11 @@ func (k msgServer) Bond(goCtx context.Context, msg *types.MsgBond) (*types.MsgBo
 	}
 
 	shareDenom := types.GetShareDenom()
-	if params.RedemptionRate.IsZero() {
-		return nil, types.ErrRedemptionRateIsZero
+	// Initial case
+	if redemptionRate.IsZero() {
+		redemptionRate = sdk.OneDec()
 	}
-	shareAmount := sdk.NewDecFromInt(depositCoin.Amount).Quo(params.RedemptionRate).RoundInt()
+	shareAmount := sdk.NewDecFromInt(depositCoin.Amount).Quo(redemptionRate).RoundInt()
 	shareCoins := sdk.NewCoins(sdk.NewCoin(shareDenom, shareAmount))
 
 	err = k.bk.MintCoins(ctx, types.ModuleName, shareCoins)

x/stablestake/keeper/msg_server_unbond.go

@@ -12,6 +12,7 @@ func (k msgServer) Unbond(goCtx context.Context, msg *types.MsgUnbond) (*types.M
 
 	params := k.GetParams(ctx)
 	creator := sdk.MustAccAddressFromBech32(msg.Creator)
+	redemptionRate := k.GetRedemptionRate(ctx)
 
 	shareDenom := types.GetShareDenom()
 
@@ -33,7 +34,7 @@ func (k msgServer) Unbond(goCtx context.Context, msg *types.MsgUnbond) (*types.M
 		return nil, err
 	}
 
-	redemptionAmount := sdk.NewDecFromInt(shareCoin.Amount).Mul(params.RedemptionRate).RoundInt()
+	redemptionAmount := sdk.NewDecFromInt(shareCoin.Amount).Mul(redemptionRate).RoundInt()
 
 	depositDenom := k.GetDepositDenom(ctx)
 	redemptionCoin := sdk.NewCoin(depositDenom, redemptionAmount)

x/stablestake/keeper/msg_server_unbond_test.go

@@ -85,7 +85,8 @@ func (suite *KeeperTestSuite) TestUnbond() {
 			suite.Require().NoError(err)
 
 			params := suite.app.StablestakeKeeper.GetParams(suite.ctx)
-			params.TotalValue = sdk.NewInt(1000_000_000)
+			params.TotalValue = sdk.NewInt(1000_000)
+			params.RedemptionRate = sdk.NewDec(1)
 			suite.app.StablestakeKeeper.SetParams(suite.ctx, params)
 
 			msgServer := keeper.NewMsgServerImpl(suite.app.StablestakeKeeper)

x/stablestake/keeper/params.go

@@ -38,3 +38,14 @@ func (k Keeper) GetDepositDenom(ctx sdk.Context) string {
 	}
 	return entry.Denom
 }
+
+func (k Keeper) GetRedemptionRate(ctx sdk.Context) sdk.Dec {
+	params := k.GetParams(ctx)
+	totalShares := k.bk.GetSupply(ctx, types.GetShareDenom())
+
+	if totalShares.Amount.IsZero() {
+		return sdk.ZeroDec()
+	}
+
+	return params.TotalValue.ToLegacyDec().Quo(totalShares.Amount.ToLegacyDec())
+}

x/stablestake/keeper/params_test.go

@@ -3,7 +3,13 @@ package keeper_test
 import (
 	"testing"
 
+	"cosmossdk.io/math"
+	"github.com/cometbft/cometbft/crypto/ed25519"
+	sdk "github.com/cosmos/cosmos-sdk/types"
+	minttypes "github.com/cosmos/cosmos-sdk/x/mint/types"
 	testkeeper "github.com/elys-network/elys/testutil/keeper"
+	ptypes "github.com/elys-network/elys/x/parameter/types"
+	"github.com/elys-network/elys/x/stablestake/keeper"
 	"github.com/elys-network/elys/x/stablestake/types"
 	"github.com/stretchr/testify/require"
 )
@@ -16,3 +22,65 @@ func TestGetParams(t *testing.T) {
 
 	require.EqualValues(t, params, k.GetParams(ctx))
 }
+
+func (suite *KeeperTestSuite) TestGetRedemptionRate() {
+	for _, tc := range []struct {
+		desc              string
+		senderInitBalance sdk.Coins
+		bondAmount        math.Int
+		expSenderBalance  sdk.Coins
+		expSenderCommit   sdk.Coin
+		expPass           bool
+	}{
+		{
+			desc:              "successful bonding process, redemption should be set",
+			senderInitBalance: sdk.Coins{sdk.NewInt64Coin(ptypes.BaseCurrency, 1000000)},
+			bondAmount:        sdk.NewInt(10000),
+			expSenderBalance:  sdk.Coins{sdk.NewInt64Coin(ptypes.BaseCurrency, 990000)}.Sort(),
+			expSenderCommit:   sdk.NewInt64Coin(types.GetShareDenom(), 10000),
+			expPass:           true,
+		},
+		{
+			desc:              "lack of balance, redemption should not be set",
+			senderInitBalance: sdk.Coins{sdk.NewInt64Coin(ptypes.BaseCurrency, 1000000)},
+			bondAmount:        sdk.NewInt(10000000000000),
+			expSenderBalance:  sdk.Coins{sdk.NewInt64Coin(ptypes.BaseCurrency, 1000000)},
+			expSenderCommit:   sdk.Coin{},
+			expPass:           false,
+		},
+	} {
+		suite.Run(tc.desc, func() {
+			suite.SetupTest()
+
+			// bootstrap accounts
+			sender := sdk.AccAddress(ed25519.GenPrivKey().PubKey().Address())
+
+			// bootstrap balances
+			err := suite.app.BankKeeper.MintCoins(suite.ctx, minttypes.ModuleName, tc.senderInitBalance)
+			suite.Require().NoError(err)
+			err = suite.app.BankKeeper.SendCoinsFromModuleToAccount(suite.ctx, minttypes.ModuleName, sender, tc.senderInitBalance)
+			suite.Require().NoError(err)
+
+			msgServer := keeper.NewMsgServerImpl(suite.app.StablestakeKeeper)
+			_, err = msgServer.Bond(
+				sdk.WrapSDKContext(suite.ctx),
+				&types.MsgBond{
+					Creator: sender.String(),
+					Amount:  tc.bondAmount,
+				})
+			if !tc.expPass {
+				suite.Require().Error(err)
+
+				// Check redemption rate
+				rate := suite.app.StablestakeKeeper.GetRedemptionRate(suite.ctx)
+				suite.Require().Equal(sdk.ZeroDec(), rate)
+			} else {
+				suite.Require().NoError(err)
+
+				// Check redemption rate
+				rate := suite.app.StablestakeKeeper.GetRedemptionRate(suite.ctx)
+				suite.Require().Equal(sdk.NewDec(1), rate)
+			}
+		})
+	}
+}

x/stablestake/types/expected_keepers.go

@@ -16,6 +16,7 @@ type AccountKeeper interface {
 // BankKeeper defines the expected interface needed to retrieve account balances.
 type BankKeeper interface {
 	GetBalance(ctx sdk.Context, addr sdk.AccAddress, denom string) sdk.Coin
+	GetSupply(ctx sdk.Context, denom string) sdk.Coin
 	MintCoins(ctx sdk.Context, moduleName string, amt sdk.Coins) error
 	BurnCoins(ctx sdk.Context, name string, amt sdk.Coins) error
 	SendCoinsFromModuleToAccount(ctx sdk.Context, senderModule string, recipientAddr sdk.AccAddress, amt sdk.Coins) error