feat: epoched reward distribution part 2 - send

When fees are sent to vbank at the epoch, calculate a rate for
distributing them to exhaust the reward pool by theend of the epoch.

golang/cosmos/proto/agoric/vbank/genesis.proto

@@ -2,10 +2,13 @@ syntax = "proto3";
 package agoric.vbank;
 
 import "gogoproto/gogo.proto";
+import "agoric/vbank/vbank.proto";
 
 option go_package = "github.com/Agoric/agoric-sdk/golang/cosmos/x/vbank/types";
 
 message GenesisState {
     option (gogoproto.equal) = false;
 
+    // parms defines all the parameters of the module.
+    Params params = 1 [(gogoproto.nullable) = false];
 }

golang/cosmos/proto/agoric/vbank/vbank.proto

@@ -0,0 +1,31 @@
+syntax = "proto3";
+package agoric.vbank;
+
+import "gogoproto/gogo.proto"; 
+import "cosmos/base/v1beta1/coin.proto";
+
+option go_package = "github.com/Agoric/agoric-sdk/golang/cosmos/x/vbank/types";
+
+message Params {
+    option (gogoproto.equal) = true;
+
+    // feeEpochDurationBlocks is the length of a fee epoch, in blocks.
+    // A value of zero has the same meaning as a value of one:
+    // the full fee buffer should be distributed immediately.
+    int64 feeEpochDurationBlocks = 1;
+}
+
+message State {
+    option (gogoproto.equal) = true;
+
+    // rewardPool is the current balance of rewards in the module account.
+    // NOTE: Tracking manually since there is no bank call for getting a
+    // module account balance by name.
+    repeated cosmos.base.v1beta1.Coin rewardPool = 1
+        [(gogoproto.nullable) = false, (gogoproto.castrepeated) = "github.com/cosmos/cosmos-sdk/types.Coins"];
+
+    // rewardRate is the amount of reward, if available, to send to the
+    // fee collector module on every block.
+    repeated cosmos.base.v1beta1.Coin rewardRate = 2
+        [(gogoproto.nullable) = false, (gogoproto.castrepeated) = "github.com/cosmos/cosmos-sdk/types.Coins"];
+}

golang/cosmos/third_party/proto/cosmos/base/v1beta1/coin.proto

@@ -0,0 +1,40 @@
+syntax = "proto3";
+package cosmos.base.v1beta1;
+
+import "gogoproto/gogo.proto";
+
+option go_package                       = "github.com/cosmos/cosmos-sdk/types";
+option (gogoproto.goproto_stringer_all) = false;
+option (gogoproto.stringer_all)         = false;
+
+// Coin defines a token with a denomination and an amount.
+//
+// NOTE: The amount field is an Int which implements the custom method
+// signatures required by gogoproto.
+message Coin {
+  option (gogoproto.equal) = true;
+
+  string denom  = 1;
+  string amount = 2 [(gogoproto.customtype) = "Int", (gogoproto.nullable) = false];
+}
+
+// DecCoin defines a token with a denomination and a decimal amount.
+//
+// NOTE: The amount field is an Dec which implements the custom method
+// signatures required by gogoproto.
+message DecCoin {
+  option (gogoproto.equal) = true;
+
+  string denom  = 1;
+  string amount = 2 [(gogoproto.customtype) = "Dec", (gogoproto.nullable) = false];
+}
+
+// IntProto defines a Protobuf wrapper around an Int object.
+message IntProto {
+  string int = 1 [(gogoproto.customtype) = "Int", (gogoproto.nullable) = false];
+}
+
+// DecProto defines a Protobuf wrapper around a Dec object.
+message DecProto {
+  string dec = 1 [(gogoproto.customtype) = "Dec", (gogoproto.nullable) = false];
+}

golang/cosmos/x/vbank/README.md

@@ -12,7 +12,7 @@ entirely at the ERTP level.
 ## Parameters
 
 - `feeCollectorName`: the module which handles fee distribution to stakers.
-- `feeEpochDuration`: the duration (in seconds) over which fees should be given to the fee collector.
+- `feeEpochDurationBlocks`: the duration (in blocks) over which fees should be given to the fee collector.
 
 ## State
 

golang/cosmos/x/vbank/keeper/keeper.go

@@ -7,7 +7,9 @@ import (
 	"github.com/Agoric/agoric-sdk/golang/cosmos/x/vbank/types"
 )
 
-const genesis string = "genesis"
+const genesisKey string = "genesis"
+const paramsKey string = "params"
+const stateKey string = "state"
 
 // Keeper maintains the link to data storage and exposes getter/setter methods for the various parts of the state machine
 type Keeper struct {
@@ -16,7 +18,6 @@ type Keeper struct {
 
 	bankKeeper       types.BankKeeper
 	feeCollectorName string
-
 	// CallToController dispatches a message to the controlling process
 	CallToController func(ctx sdk.Context, str string) (string, error)
 }
@@ -40,15 +41,19 @@ func NewKeeper(
 
 func (k Keeper) GetGenesis(ctx sdk.Context) types.GenesisState {
 	store := ctx.KVStore(k.storeKey)
-	bz := store.Get([]byte(genesis))
+	bz := store.Get([]byte(genesisKey))
 	var gs types.GenesisState
 	k.cdc.MustUnmarshalLengthPrefixed(bz, &gs)
 	return gs
 }
 
 func (k Keeper) SetGenesis(ctx sdk.Context, data types.GenesisState) {
 	store := ctx.KVStore(k.storeKey)
-	store.Set([]byte(genesis), k.cdc.MustMarshalLengthPrefixed(&data))
+	store.Set([]byte(genesisKey), k.cdc.MustMarshalLengthPrefixed(&data))
+	params := types.Params{
+		FeeEpochDurationBlocks: data.GetParams().FeeEpochDurationBlocks,
+	}
+	k.SetParams(ctx, params)
 }
 
 func (k Keeper) GetBalance(ctx sdk.Context, addr sdk.AccAddress, denom string) sdk.Coin {
@@ -64,9 +69,6 @@ func (k Keeper) StoreFeeCoins(ctx sdk.Context, amt sdk.Coins) error {
 }
 
 func (k Keeper) SendCoinsToFeeCollector(ctx sdk.Context, amt sdk.Coins) error {
-	if err := k.bankKeeper.MintCoins(ctx, types.ModuleName, amt); err != nil {
-		return err
-	}
 	return k.bankKeeper.SendCoinsFromModuleToModule(ctx, types.ModuleName, k.feeCollectorName, amt)
 }
 
@@ -83,3 +85,31 @@ func (k Keeper) GrabCoins(ctx sdk.Context, addr sdk.AccAddress, amt sdk.Coins) e
 	}
 	return k.bankKeeper.BurnCoins(ctx, types.ModuleName, amt)
 }
+
+func (k Keeper) GetParams(ctx sdk.Context) types.Params {
+	store := ctx.KVStore(k.storeKey)
+	bz := store.Get([]byte(paramsKey))
+	params := types.Params{}
+	k.cdc.MustUnmarshal(bz, &params)
+	return params
+}
+
+func (k Keeper) SetParams(ctx sdk.Context, params types.Params) {
+	store := ctx.KVStore(k.storeKey)
+	bz := k.cdc.MustMarshal(&params)
+	store.Set([]byte(paramsKey), bz)
+}
+
+func (k Keeper) GetState(ctx sdk.Context) types.State {
+	store := ctx.KVStore(k.storeKey)
+	bz := store.Get([]byte(stateKey))
+	state := types.State{}
+	k.cdc.MustUnmarshal(bz, &state)
+	return state
+}
+
+func (k Keeper) SetState(ctx sdk.Context, state types.State) {
+	store := ctx.KVStore(k.storeKey)
+	bz := k.cdc.MustMarshal(&state)
+	store.Set([]byte(stateKey), bz)
+}

golang/cosmos/x/vbank/module.go

@@ -3,6 +3,7 @@ package vbank
 import (
 	"encoding/json"
 	stdlog "log"
+	"strings"
 
 	"github.com/gorilla/mux"
 	"github.com/grpc-ecosystem/grpc-gateway/runtime"
@@ -25,6 +26,32 @@ var (
 	_ module.AppModuleBasic = AppModuleBasic{}
 )
 
+// minCoins returns the minimum of each denomination.
+// The input coins should be sorted.
+func minCoins(a, b sdk.Coins) sdk.Coins {
+	min := make([]sdk.Coin, 0)
+	for indexA, indexB := 0, 0; indexA < len(a) && indexB < len(b); {
+		coinA, coinB := a[indexA], b[indexB]
+		switch strings.Compare(coinA.Denom, coinB.Denom) {
+		case -1: // A < B
+			indexA++
+		case 0: // A == B
+			minCoin := coinA
+			if coinB.IsLT(minCoin) {
+				minCoin = coinB
+			}
+			if !minCoin.IsZero() {
+				min = append(min, minCoin)
+			}
+			indexA++
+			indexB++
+		case 1: // A > B
+			indexB++
+		}
+	}
+	return sdk.NewCoins(min...)
+}
+
 // app module Basics object
 type AppModuleBasic struct {
 	cdc codec.Codec
@@ -167,6 +194,15 @@ func (am AppModule) EndBlock(ctx sdk.Context, req abci.RequestEndBlock) []abci.V
 		}
 	}
 
+	// Distribute rewards.
+	state := am.keeper.GetState(ctx)
+	xfer := minCoins(state.RewardRate, state.RewardPool)
+	if !xfer.IsZero() {
+		am.keeper.SendCoinsToFeeCollector(ctx, xfer)
+		state.RewardPool = state.RewardPool.Sub(xfer)
+		am.keeper.SetState(ctx, state)
+	}
+
 	return []abci.ValidatorUpdate{}
 }