Encapsulate gasfee API (#21)

go.mod

@@ -1,6 +1,6 @@
 module github.com/DeBankDeFi/etherlib
 
-go 1.17
+go 1.22
 
 require (
 	github.com/ethereum/go-ethereum v1.13.14

pkg/gasfeesvc/README.md

@@ -0,0 +1,12 @@
+## 说明
+
+为方便查阅各个链的 gas fee 预估实现, 以及避免每条链一个分支, 所有链的 gas fee 预估实现都在 `pkg/gasfeesvc/` 目录下, 节点代码引用此包时使用条件编译决定要编译哪条链的实现代码.
+
+若新链与现有某条链的实现一直, 可以直接复用现有实现, 但是在实现顶部一定要添加对应链的 build tag. 这将作为后续查询某个实现已被用于哪些链的依据, 防止修改某个实现意外影响其它链.
+
+比如, op 的 gas fee 预估逻辑也适用于 base, 则 `op.go` 实现文件顶部一定要同时包含 op base 两个 build tag, 且关系为或.
+
+```
+//go:build op || base
+// +build op base
+```

pkg/gasfeesvc/common.go

@@ -0,0 +1,17 @@
+package gasfeesvc
+
+type EstimatedGasFee struct {
+	MaxPriorityFeePerGas float64 `json:"maxPriorityFeePerGas"`
+	MaxFeePerGas         float64 `json:"maxFeePerGas"`
+}
+
+type SuggestedGasFees struct {
+	BaseBlock                  int64                       `json:"baseBlock"`
+	NextBaseFee                float64                     `json:"nextBaseFee"`
+	GasUsedRatio               []float64                   `json:"gasUsedRatio"`
+	HistoricalBaseFees         []float64                   `json:"historicalBaseFees,omitempty"`
+	HistoricalRewards          []float64                   `json:"historicalRewards,omitempty"`
+	RegulatedHistoricalRewards []float64                   `json:"regulatedHistoricalRewards,omitempty"`
+	StdDevThreshold            float64                     `json:"stdDevThreshold,omitempty"`
+	EstimatedGasFees           map[string]*EstimatedGasFee `json:"estimatedGasFees"`
+}

pkg/gasfeesvc/eth.go

@@ -0,0 +1,88 @@
+//go:build eth
+// +build eth
+
+package gasfeesvc
+
+import (
+	"context"
+	"math"
+	"math/big"
+	"sort"
+
+	"github.com/ethereum/go-ethereum/rpc"
+	"github.com/gonum/stat"
+)
+
+type FeeHistory func(ctx context.Context, blocks uint64, lastBlock *rpc.BlockNumber, rewardPercentiles []float64) (*big.Int, [][]*big.Int, []*big.Int, []float64, error)
+
+func SuggestGasFees(ctx context.Context, lastBlock *rpc.BlockNumber, feeHistory FeeHistory) (*SuggestedGasFees, error) {
+	// query the past 10 blocks
+	blocks := 10
+	stdDevThreshold := 1.0
+	baseFeeIncreateRatio := []float64{1.0, 1.45, 2.35} // metamask is: 1, 1.43, 2.3
+	tipFeePercentiles := []float64{0.1, 0.5, 0.9}
+	levels := []string{"normal", "fast", "instant"}
+
+	// firstly we get all percentiles, we will do preprocessing on the returned data and pickup 3 percentiles as the normal, fast, instant levels
+	rewardPercentiles := []float64{}
+	for i := range 100 {
+		rewardPercentiles = append(rewardPercentiles, float64(i))
+	}
+
+	if lastBlock == nil {
+		lastBlock = new(rpc.BlockNumber)
+		*lastBlock = rpc.LatestBlockNumber
+	}
+	oldest, rewards, baseFees, gasUsedRatios, err := feeHistory(ctx, uint64(blocks), lastBlock, rewardPercentiles)
+	if err != nil {
+		return nil, err
+	}
+
+	// pre process the original data from the Oracle
+	// 1. convert the original data unit "wei" to "gwei"
+	// 2. remove the exceptional rewards that deviate too much from the mean
+	results := &SuggestedGasFees{
+		BaseBlock:        oldest.Int64() + int64(blocks) - 1,
+		GasUsedRatio:     gasUsedRatios,
+		StdDevThreshold:  stdDevThreshold,
+		EstimatedGasFees: make(map[string]*EstimatedGasFee, 3),
+	}
+	for _, baseFee := range baseFees {
+		if bf, accuracy := new(big.Float).SetInt(baseFee).Float64(); accuracy == 0 {
+			results.HistoricalBaseFees = append(results.HistoricalBaseFees, bf/1_000_000_000)
+			results.NextBaseFee = bf / 1_000_000_000 // set the next block's base fee here too
+		}
+	}
+	for _, rewardsIn1Blk := range rewards {
+		for _, txReward := range rewardsIn1Blk {
+			if rwd, accuracy := new(big.Float).SetInt(txReward).Float64(); accuracy == 0 {
+				results.HistoricalRewards = append(results.HistoricalRewards, rwd/1_000_000_000)
+			}
+		}
+	}
+
+	// remove the rewards that 1x from the Standard Deviation
+	mean, stdDev := stat.MeanStdDev(results.HistoricalRewards, nil)
+	regulated := []float64{}
+	for _, num := range results.HistoricalRewards {
+		if math.Abs(num-mean) <= stdDevThreshold*stdDev {
+			regulated = append(regulated, num)
+		}
+	}
+	sort.Float64s(regulated)
+	results.RegulatedHistoricalRewards = regulated
+
+	for i, level := range levels {
+		percentile := tipFeePercentiles[i]
+		baseFeeRatio := baseFeeIncreateRatio[i]
+
+		idx := int(percentile * float64(len(regulated)))
+		tip := regulated[idx]
+
+		results.EstimatedGasFees[level] = &EstimatedGasFee{
+			MaxPriorityFeePerGas: tip,
+			MaxFeePerGas:         results.NextBaseFee*baseFeeRatio + tip,
+		}
+	}
+	return results, nil
+}

pkg/gasfeesvc/op.go

@@ -0,0 +1,4 @@
+//go:build op || base
+// +build op base
+
+package gasfeesvc