chore: change bridge-tax to be per token (#1212)

# Related Github tickets

- Closes VolumeFi#1815

# Background

We want bridge taxes to be per token, instead of global.

- Change bridge tax setter and getter to include token
- Change bridge tax proposal to include token
- Change query RPC to return all bridge taxes, same as bridge transfer
limits
- Update genesis
- Removed `excluded_token` setting as it doesn't make sense now

# Testing completed

- [x] test coverage exists or has been added/updated
- [x] tested in a private testnet

# Breaking changes

- [x] I have checked my code for breaking changes
- [x] If there are breaking changes, there is a supporting migration.

docs/Skyway-Bridge-Tax.md

@@ -2,26 +2,21 @@
 
 All outbound transactions from the bridge to the target EVM and other chains pay
 a tax on the skyway bridge. This tax is added to the cost of the transfer.
-A governance vote is needed to define the tax rate, as well as a list of tokens
-and addresses that are exempt from the bridge tax.
+A governance vote is needed to define the tax rate for a specific token, as well
+as a list of addresses that are exempt from the bridge tax.
 
 ## Tax Rate
 
 The tax rate must be defined as a non-negative value, with 0 meaning no tax is
-applied.
+applied. This is the ratio of the tax applied on top of the transfer, so a tax
+rate value of 0.2 means a 20% tax.
 
 The tax is added to the cost of the transfer and will stay locked until the
 transfer is finished.
 If the transfer is successful, the taxed amount is burned on the Paloma side.
 If a transfer is canceled before being executed, the full initial amount, plus
 tax, is refunded.
 
-## Excluded Tokens
-
-The governance vote can define a list of tokens that are excluded from the
-bridge tax. Transfers of these tokens will never pay bridge tax and will be
-transferred in the full amount.
-
 ## Exempt Addresses
 
 Similarly, the governance vote can define a list of addresses that are exempt

proto/palomachain/paloma/skyway/bridge_tax.proto

@@ -1,14 +1,17 @@
 syntax = "proto3";
 package palomachain.paloma.skyway;
 
-import "gogoproto/gogo.proto";
 import "cosmos_proto/cosmos.proto";
+import "gogoproto/gogo.proto";
 
 option go_package = "github.com/palomachain/paloma/x/skyway/types";
 
 message BridgeTax {
+  reserved 2;
+  reserved "excluded_tokens";
+
   string rate = 1 [ (cosmos_proto.scalar) = "cosmos.Dec" ];
-  repeated string excluded_tokens = 2;
   repeated bytes exempt_addresses = 3
     [ (gogoproto.casttype) = "github.com/cosmos/cosmos-sdk/types.AccAddress" ];
+  string token = 4;
 }

proto/palomachain/paloma/skyway/bridge_tax_proposal.proto

@@ -6,9 +6,12 @@ import "cosmos_proto/cosmos.proto";
 option go_package = "github.com/palomachain/paloma/x/skyway/types";
 
 message SetBridgeTaxProposal {
+  reserved 4;
+  reserved "excluded_tokens";
+
   string title = 1;
   string description = 2;
   string rate = 3 [ (cosmos_proto.scalar) = "cosmos.Dec" ];
-  repeated string excluded_tokens = 4;
   repeated string exempt_addresses = 5;
+  string token = 6;
 }

proto/palomachain/paloma/skyway/genesis.proto

@@ -15,6 +15,9 @@ option go_package = "github.com/palomachain/paloma/x/skyway/types";
 // GenesisState struct, containing all persistant data required by the Skyway
 // module
 message GenesisState {
+  reserved 11;
+  reserved "bridge_tax";
+
   Params params = 1;
   repeated SkywayNonces skyway_nonces = 2 [ (gogoproto.nullable) = false ];
   repeated OutgoingTxBatch batches = 3 [ (gogoproto.nullable) = false ];
@@ -23,8 +26,8 @@ message GenesisState {
   repeated ERC20ToDenom erc20_to_denoms = 9 [ (gogoproto.nullable) = false ];
   repeated OutgoingTransferTx unbatched_transfers = 10
       [ (gogoproto.nullable) = false ];
-  BridgeTax bridge_tax = 11;
   repeated BridgeTransferLimit bridge_transfer_limits = 12;
+  repeated BridgeTax bridge_taxes = 13;
 }
 
 // SkywayCounters contains the many noces and counters required to maintain the

proto/palomachain/paloma/skyway/query.proto

@@ -46,8 +46,8 @@ service Query {
   rpc GetPendingSendToEth(QueryPendingSendToEth)
       returns (QueryPendingSendToEthResponse) {}
 
-  rpc GetBridgeTax(google.protobuf.Empty) returns (QueryBridgeTaxResponse) {
-    option (google.api.http).get = "/palomachain/paloma/skyway/bridge_tax";
+  rpc GetBridgeTaxes(google.protobuf.Empty) returns (QueryBridgeTaxesResponse) {
+    option (google.api.http).get = "/palomachain/paloma/skyway/bridge_taxes";
   }
 
   rpc GetBridgeTransferLimits(google.protobuf.Empty)
@@ -161,8 +161,8 @@ message QueryPendingSendToEthResponse {
       [ (gogoproto.nullable) = false ];
 }
 
-message QueryBridgeTaxResponse {
-  BridgeTax bridge_tax = 1;
+message QueryBridgeTaxesResponse {
+  repeated BridgeTax bridge_taxes = 1;
 }
 
 message QueryBridgeTransferLimitsResponse {

x/skyway/client/cli/query.go

@@ -336,8 +336,8 @@ func GetCmdQueryParams() *cobra.Command {
 // GetCmdQueryBridgeTax fetches the current Skyway module bridge tax settings
 func GetCmdQueryBridgeTax() *cobra.Command {
 	cmd := &cobra.Command{
-		Use:   "bridge-tax",
-		Short: "Query BridgeTax Settings",
+		Use:   "bridge-taxes",
+		Short: "Query bridge tax settings for all tokens",
 		Args:  cobra.ExactArgs(0),
 		RunE: func(cmd *cobra.Command, args []string) (err error) {
 			clientCtx, err := client.GetClientTxContext(cmd)
@@ -349,7 +349,7 @@ func GetCmdQueryBridgeTax() *cobra.Command {
 
 			params := &emptypb.Empty{}
 
-			res, err := queryClient.GetBridgeTax(cmd.Context(), params)
+			res, err := queryClient.GetBridgeTaxes(cmd.Context(), params)
 			if err != nil {
 				return err
 			}

x/skyway/client/cli/tx_proposal.go

@@ -92,17 +92,18 @@ func CmdSetErc20ToDenom() *cobra.Command {
 
 func CmdSetBridgeTax() *cobra.Command {
 	cmd := &cobra.Command{
-		Use:   "set-bridge-tax [tax-rate]",
-		Short: "Sets the bridge tax rate, and optionally token exceptions and exempt addresses",
-		Long:  "Each outgoing transfer from Paloma will pay a tax. Tax amount is calculated using [tax-rate], which must be non-negative.",
-		Args:  cobra.ExactArgs(1),
+		Use:     "set-bridge-tax [token] [tax-rate]",
+		Short:   "Sets the bridge tax rate for a token, and optional exempt addresses",
+		Long:    "Each outgoing transfer from Paloma will pay a tax. Tax amount is calculated using [tax-rate], which must be non-negative. [tax-rate] is the ratio of tax collected, so for a 20%% tax it must be set to 0.2.",
+		Example: "set-bridge-tax ugrain 0.2",
+		Args:    cobra.ExactArgs(2),
 		RunE: func(cmd *cobra.Command, args []string) error {
 			cliCtx, err := client.GetClientTxContext(cmd)
 			if err != nil {
 				return err
 			}
 
-			rateRaw := args[0]
+			token, rateRaw := args[0], args[1]
 
 			rate, ok := new(big.Rat).SetString(rateRaw)
 			if !ok || rate.Sign() < 0 {
@@ -119,11 +120,6 @@ func CmdSetBridgeTax() *cobra.Command {
 				return err
 			}
 
-			excludedTokens, err := cmd.Flags().GetStringSlice(flagExcludedTokens)
-			if err != nil {
-				return err
-			}
-
 			exemptAddresses, err := cmd.Flags().GetStringSlice(flagExemptAddresses)
 			if err != nil {
 				return err
@@ -132,8 +128,8 @@ func CmdSetBridgeTax() *cobra.Command {
 			prop := &types.SetBridgeTaxProposal{
 				Title:           title,
 				Description:     description,
+				Token:           token,
 				Rate:            rateRaw,
-				ExcludedTokens:  excludedTokens,
 				ExemptAddresses: exemptAddresses,
 			}
 

x/skyway/keeper/batch_test.go

@@ -777,7 +777,7 @@ func TestBridgeTax(t *testing.T) {
 	require.NoError(t, e4)
 
 	// set bridge tax
-	input.SkywayKeeper.SetBridgeTax(ctx, &types.BridgeTax{Rate: "0.02"})
+	input.SkywayKeeper.SetBridgeTax(ctx, &types.BridgeTax{Token: testDenom, Rate: "0.02"})
 
 	// mint some voucher first
 	require.NoError(t, input.BankKeeper.MintCoins(ctx, types.ModuleName, allVouchers))

x/skyway/keeper/genesis.go

@@ -137,17 +137,15 @@ func InitGenesis(ctx context.Context, k Keeper, data types.GenesisState) {
 		}
 	}
 
-	if data.BridgeTax != nil {
-		if err := k.SetBridgeTax(ctx, data.BridgeTax); err != nil {
+	for _, tax := range data.BridgeTaxes {
+		if err := k.SetBridgeTax(ctx, tax); err != nil {
 			panic(err)
 		}
 	}
 
-	if data.BridgeTransferLimits != nil {
-		for _, limit := range data.BridgeTransferLimits {
-			if err := k.SetBridgeTransferLimit(ctx, limit); err != nil {
-				panic(err)
-			}
+	for _, limit := range data.BridgeTransferLimits {
+		if err := k.SetBridgeTransferLimit(ctx, limit); err != nil {
+			panic(err)
 		}
 	}
 }
@@ -239,7 +237,7 @@ func ExportGenesis(ctx context.Context, k Keeper) types.GenesisState {
 		unbatchedTxs[i] = v.ToExternal()
 	}
 
-	tax, err := k.BridgeTax(ctx)
+	taxes, err := k.AllBridgeTaxes(ctx)
 	if err != nil && !errors.Is(err, keeperutil.ErrNotFound) {
 		panic(err)
 	}
@@ -257,7 +255,7 @@ func ExportGenesis(ctx context.Context, k Keeper) types.GenesisState {
 		Attestations:         attestations,
 		Erc20ToDenoms:        erc20ToDenoms,
 		UnbatchedTransfers:   unbatchedTxs,
-		BridgeTax:            tax,
+		BridgeTaxes:          taxes,
 		BridgeTransferLimits: limits,
 	}
 }

x/skyway/keeper/genesis_test.go

@@ -146,10 +146,12 @@ func TestGenesis(t *testing.T) {
 
 	genesisState := types.GenesisState{
 		Params: types.DefaultParams(),
-		BridgeTax: &types.BridgeTax{
-			Rate:            "0.02",
-			ExcludedTokens:  []string{"test"},
-			ExemptAddresses: addresses,
+		BridgeTaxes: []*types.BridgeTax{
+			{
+				Rate:            "0.02",
+				Token:           "test",
+				ExemptAddresses: addresses,
+			},
 		},
 		BridgeTransferLimits: []*types.BridgeTransferLimit{
 			{
@@ -167,7 +169,7 @@ func TestGenesis(t *testing.T) {
 	got := ExportGenesis(input.Context, input.SkywayKeeper)
 	require.NotNil(t, got)
 
-	require.Equal(t, genesisState.BridgeTax, got.BridgeTax)
+	require.Equal(t, genesisState.BridgeTaxes, got.BridgeTaxes)
 	require.Equal(t, genesisState.BridgeTransferLimits, got.BridgeTransferLimits)
 }
 
@@ -182,6 +184,6 @@ func TestGenesisEmptyOptionalValues(t *testing.T) {
 	got := ExportGenesis(input.Context, input.SkywayKeeper)
 	require.NotNil(t, got)
 
-	require.Nil(t, got.BridgeTax)
+	require.Empty(t, got.BridgeTaxes)
 	require.Empty(t, got.BridgeTransferLimits)
 }

x/skyway/keeper/governance_proposals.go

@@ -29,7 +29,7 @@ func NewSkywayProposalHandler(k Keeper) govv1beta1types.Handler {
 
 			bridgeTax := &types.BridgeTax{
 				Rate:            c.Rate,
-				ExcludedTokens:  c.ExcludedTokens,
+				Token:           c.Token,
 				ExemptAddresses: addresses,
 			}
 

x/skyway/keeper/grpc_query_get_bridge_tax.go → x/skyway/keeper/grpc_query_get_bridge_taxes.go

@@ -8,18 +8,18 @@ import (
 	"google.golang.org/protobuf/types/known/emptypb"
 )
 
-func (k Keeper) GetBridgeTax(
+func (k Keeper) GetBridgeTaxes(
 	goCtx context.Context,
 	_ *emptypb.Empty,
-) (*types.QueryBridgeTaxResponse, error) {
+) (*types.QueryBridgeTaxesResponse, error) {
 	ctx := sdk.UnwrapSDKContext(goCtx)
 
-	tax, err := k.BridgeTax(ctx)
+	taxes, err := k.AllBridgeTaxes(ctx)
 	if err != nil {
 		return nil, err
 	}
 
-	return &types.QueryBridgeTaxResponse{
-		BridgeTax: tax,
+	return &types.QueryBridgeTaxesResponse{
+		BridgeTaxes: taxes,
 	}, nil
 }