From cd3b0be5edf616db302b3f838fdfd3ae8c24d84e Mon Sep 17 00:00:00 2001
From: Thomas Nguy <81727899+thomas-nguy@users.noreply.github.com>
Date: Fri, 15 Oct 2021 17:59:26 +0900
Subject: [PATCH] rpc, feemarket: store base fee in event (#673)

* store base fee in event

* update changelog
---
 CHANGELOG.md                               |  1 +
 rpc/ethereum/backend/backend.go            | 20 +++++++++--------
 rpc/ethereum/namespaces/eth/filters/api.go | 12 ++++-------
 rpc/ethereum/types/utils.go                | 25 ++++++++++++++++++++++
 x/feemarket/keeper/abci.go                 | 12 ++++++++++-
 x/feemarket/keeper/eip1559.go              |  7 +++---
 x/feemarket/keeper/keeper.go               |  4 ++--
 x/feemarket/types/events.go                |  8 +++++++
 x/feemarket/types/params.go                |  4 ++++
 9 files changed, 70 insertions(+), 23 deletions(-)
 create mode 100644 x/feemarket/types/events.go

diff --git a/CHANGELOG.md b/CHANGELOG.md
index c6329375..a8832269 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -44,6 +44,7 @@ Ref: https://keepachangelog.com/en/1.0.0/
 
 ### Features
 
+* (rpc, evm) [tharsis#673](https://github.com/tharsis/ethermint/pull/673) Use tendermint events to store fee market basefee.
 * (rpc) [tharsis#624](https://github.com/tharsis/ethermint/pull/624) Implement new JSON-RPC endpoints from latest geth version
 * (evm) [tharsis#662](https://github.com/tharsis/ethermint/pull/662) Disable basefee for non london blocks
 
diff --git a/rpc/ethereum/backend/backend.go b/rpc/ethereum/backend/backend.go
index e7edc2d3..3dfbaa00 100644
--- a/rpc/ethereum/backend/backend.go
+++ b/rpc/ethereum/backend/backend.go
@@ -826,22 +826,24 @@ func (e *EVMBackend) BaseFee(height int64) (*big.Int, error) {
 		return nil, nil
 	}
 
-	res, err := e.queryClient.FeeMarket.BaseFee(types.ContextWithHeight(height), &feemarkettypes.QueryBaseFeeRequest{})
+	blockRes, err := e.clientCtx.Client.BlockResults(e.ctx, &height)
 	if err != nil {
 		return nil, err
 	}
 
-	if res.BaseFee != nil {
+	baseFee := types.BaseFeeFromEvents(blockRes.EndBlockEvents)
+	if baseFee != nil {
+		return baseFee, nil
+	}
+
+	// If we cannot find in events, we tried to get it from the state.
+	// It will return feemarket.baseFee if london is activated but feemarket is not enable
+	res, err := e.queryClient.FeeMarket.BaseFee(types.ContextWithHeight(height), &feemarkettypes.QueryBaseFeeRequest{})
+	if err == nil && res.BaseFee != nil {
 		return res.BaseFee.BigInt(), nil
 	}
 
-	resParams, err := e.queryClient.FeeMarket.Params(types.ContextWithHeight(height), &feemarkettypes.QueryParamsRequest{})
-	if err != nil {
-		return nil, err
-	}
-
-	baseFee := big.NewInt(resParams.Params.InitialBaseFee)
-	return baseFee, nil
+	return nil, nil
 }
 
 // GetFilteredBlocks returns the block height list match the given bloom filters.
diff --git a/rpc/ethereum/namespaces/eth/filters/api.go b/rpc/ethereum/namespaces/eth/filters/api.go
index 2922b603..19303321 100644
--- a/rpc/ethereum/namespaces/eth/filters/api.go
+++ b/rpc/ethereum/namespaces/eth/filters/api.go
@@ -3,7 +3,6 @@ package filters
 import (
 	"context"
 	"fmt"
-	"math/big"
 	"sync"
 	"time"
 
@@ -18,7 +17,6 @@ import (
 	"github.com/ethereum/go-ethereum/common"
 	ethtypes "github.com/ethereum/go-ethereum/core/types"
 	"github.com/ethereum/go-ethereum/eth/filters"
-	"github.com/ethereum/go-ethereum/params"
 	"github.com/ethereum/go-ethereum/rpc"
 
 	evmtypes "github.com/tharsis/ethermint/x/evm/types"
@@ -239,9 +237,6 @@ func (api *PublicFilterAPI) NewBlockFilter() rpc.ID {
 		return rpc.ID(fmt.Sprintf("error creating block filter: %s", err.Error()))
 	}
 
-	// TODO: use events to get the base fee amount
-	baseFee := big.NewInt(params.InitialBaseFee)
-
 	api.filters[headerSub.ID()] = &filter{typ: filters.BlocksSubscription, deadline: time.NewTimer(deadline), hashes: []common.Hash{}, s: headerSub}
 
 	go func(headersCh <-chan coretypes.ResultEvent, errCh <-chan error) {
@@ -263,6 +258,8 @@ func (api *PublicFilterAPI) NewBlockFilter() rpc.ID {
 					continue
 				}
 
+				baseFee := types.BaseFeeFromEvents(data.ResultEndBlock.Events)
+
 				header := types.EthHeaderFromTendermint(data.Header, baseFee)
 				api.filtersMu.Lock()
 				if f, found := api.filters[headerSub.ID()]; found {
@@ -296,9 +293,6 @@ func (api *PublicFilterAPI) NewHeads(ctx context.Context) (*rpc.Subscription, er
 		return &rpc.Subscription{}, err
 	}
 
-	// TODO: use events to get the base fee amount
-	baseFee := big.NewInt(params.InitialBaseFee)
-
 	go func(headersCh <-chan coretypes.ResultEvent) {
 		defer cancelSubs()
 
@@ -316,6 +310,8 @@ func (api *PublicFilterAPI) NewHeads(ctx context.Context) (*rpc.Subscription, er
 					continue
 				}
 
+				baseFee := types.BaseFeeFromEvents(data.ResultEndBlock.Events)
+
 				header := types.EthHeaderFromTendermint(data.Header, baseFee)
 				err = notifier.Notify(rpcSub.ID, header)
 				if err != nil {
diff --git a/rpc/ethereum/types/utils.go b/rpc/ethereum/types/utils.go
index c2ebd41d..7cbaf2fc 100644
--- a/rpc/ethereum/types/utils.go
+++ b/rpc/ethereum/types/utils.go
@@ -1,11 +1,15 @@
 package types
 
 import (
+	"bytes"
 	"context"
 	"encoding/hex"
 	"fmt"
 	"math/big"
 
+	abci "github.com/tendermint/tendermint/abci/types"
+	feemarkettypes "github.com/tharsis/ethermint/x/feemarket/types"
+
 	tmbytes "github.com/tendermint/tendermint/libs/bytes"
 	tmtypes "github.com/tendermint/tendermint/types"
 
@@ -244,3 +248,24 @@ func NewRPCTransaction(
 	}
 	return result, nil
 }
+
+// BaseFeeFromEvents parses the feemarket basefee from cosmos events
+func BaseFeeFromEvents(events []abci.Event) *big.Int {
+	for _, event := range events {
+		if event.Type != feemarkettypes.EventTypeFeeMarket {
+			continue
+		}
+
+		for _, attr := range event.Attributes {
+			if bytes.Equal(attr.Key, []byte(feemarkettypes.AttributeKeyBaseFee)) {
+				result, success := new(big.Int).SetString(string(attr.Value), 10)
+				if success {
+					return result
+				}
+
+				return nil
+			}
+		}
+	}
+	return nil
+}
diff --git a/x/feemarket/keeper/abci.go b/x/feemarket/keeper/abci.go
index 8c709072..8c99b6f2 100644
--- a/x/feemarket/keeper/abci.go
+++ b/x/feemarket/keeper/abci.go
@@ -4,6 +4,7 @@ import (
 	"fmt"
 
 	abci "github.com/tendermint/tendermint/abci/types"
+	"github.com/tharsis/ethermint/x/feemarket/types"
 
 	sdk "github.com/cosmos/cosmos-sdk/types"
 )
@@ -13,13 +14,22 @@ import (
 // an empty slice.
 func (k *Keeper) EndBlock(ctx sdk.Context, req abci.RequestEndBlock) {
 	baseFee := k.CalculateBaseFee(ctx)
+
+	// return immediately if base fee is nil
 	if baseFee == nil {
 		return
 	}
 
-	// only set base fee if the NoBaseFee param is false
 	k.SetBaseFee(ctx, baseFee)
 
+	// Store current base fee in event
+	ctx.EventManager().EmitEvents(sdk.Events{
+		sdk.NewEvent(
+			types.EventTypeFeeMarket,
+			sdk.NewAttribute(types.AttributeKeyBaseFee, baseFee.String()),
+		),
+	})
+
 	if ctx.BlockGasMeter() == nil {
 		k.Logger(ctx).Error("block gas meter is nil when setting block gas used")
 		return
diff --git a/x/feemarket/keeper/eip1559.go b/x/feemarket/keeper/eip1559.go
index 0ce9faef..68261c9b 100644
--- a/x/feemarket/keeper/eip1559.go
+++ b/x/feemarket/keeper/eip1559.go
@@ -10,20 +10,21 @@ import (
 )
 
 // CalculateBaseFee calculates the base fee for the current block. This is only calculated once per
-// block during EndBlock. If the NoBaseFee parameter is enabled, this function returns nil.
+// block during EndBlock. If the NoBaseFee parameter is enabled or below activation height, this function returns nil.
 // NOTE: This code is inspired from the go-ethereum EIP1559 implementation and adapted to Cosmos SDK-based
 // chains. For the canonical code refer to: https://github.com/ethereum/go-ethereum/blob/master/consensus/misc/eip1559.go
 func (k Keeper) CalculateBaseFee(ctx sdk.Context) *big.Int {
 	params := k.GetParams(ctx)
 
-	if params.NoBaseFee {
+	// Ignore the calculation if not enable
+	if !params.IsBaseFeeEnabled(ctx.BlockHeight()) {
 		return nil
 	}
 
 	consParams := ctx.ConsensusParams()
 
 	// If the current block is the first EIP-1559 block, return the InitialBaseFee.
-	if ctx.BlockHeight() <= params.EnableHeight {
+	if ctx.BlockHeight() == params.EnableHeight {
 		return new(big.Int).SetInt64(params.InitialBaseFee)
 	}
 
diff --git a/x/feemarket/keeper/keeper.go b/x/feemarket/keeper/keeper.go
index 43d130b8..a01867f4 100644
--- a/x/feemarket/keeper/keeper.go
+++ b/x/feemarket/keeper/keeper.go
@@ -71,7 +71,7 @@ func (k Keeper) SetBlockGasUsed(ctx sdk.Context, gas uint64) {
 // Required by EIP1559 base fee calculation.
 // ----------------------------------------------------------------------------
 
-// GetBlockGasUsed returns the last block gas used value from the store.
+// GetLastBaseFee returns the last base fee value from the store.
 func (k Keeper) GetBaseFee(ctx sdk.Context) *big.Int {
 	store := ctx.KVStore(k.storeKey)
 	bz := store.Get(types.KeyPrefixBaseFee)
@@ -82,7 +82,7 @@ func (k Keeper) GetBaseFee(ctx sdk.Context) *big.Int {
 	return new(big.Int).SetBytes(bz)
 }
 
-// SetBlockGasUsed gets the current block gas consumed to the store.
+// SetBaseFee set the last base fee value to the store.
 // CONTRACT: this should be only called during EndBlock.
 func (k Keeper) SetBaseFee(ctx sdk.Context, baseFee *big.Int) {
 	store := ctx.KVStore(k.storeKey)
diff --git a/x/feemarket/types/events.go b/x/feemarket/types/events.go
new file mode 100644
index 00000000..e673e988
--- /dev/null
+++ b/x/feemarket/types/events.go
@@ -0,0 +1,8 @@
+package types
+
+// feemarket module events
+const (
+	EventTypeFeeMarket = "fee_market"
+
+	AttributeKeyBaseFee = "base_fee"
+)
diff --git a/x/feemarket/types/params.go b/x/feemarket/types/params.go
index 7ef53311..a6ff3f00 100644
--- a/x/feemarket/types/params.go
+++ b/x/feemarket/types/params.go
@@ -80,6 +80,10 @@ func (p Params) Validate() error {
 	return nil
 }
 
+func (p *Params) IsBaseFeeEnabled(height int64) bool {
+	return !p.NoBaseFee && height >= p.EnableHeight
+}
+
 func validateBool(i interface{}) error {
 	_, ok := i.(bool)
 	if !ok {