From ea8023d4dc75a1556e9402f189eb8a945b22788c Mon Sep 17 00:00:00 2001
From: lmittmann <lmittmann@users.noreply.github.com>
Date: Thu, 3 Apr 2025 09:39:05 +0200
Subject: [PATCH 1/2] init

---
 cmd/trace/main.go | 162 ++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 162 insertions(+)
 create mode 100644 cmd/trace/main.go

diff --git a/cmd/trace/main.go b/cmd/trace/main.go
new file mode 100644
index 0000000..5891d0d
--- /dev/null
+++ b/cmd/trace/main.go
@@ -0,0 +1,162 @@
+package main
+
+import (
+	"flag"
+	"fmt"
+	"math/big"
+	"os"
+
+	"github.com/ethereum/go-ethereum/common"
+	"github.com/ethereum/go-ethereum/core/tracing"
+	"github.com/ethereum/go-ethereum/core/types"
+	"github.com/ethereum/go-ethereum/params"
+	"github.com/lmittmann/w3"
+	"github.com/lmittmann/w3/module/eth"
+	"github.com/lmittmann/w3/w3types"
+	"github.com/lmittmann/w3/w3vm"
+	"github.com/lmittmann/w3/w3vm/hooks"
+)
+
+var chainConfigs = map[uint64]*params.ChainConfig{
+	1: params.MainnetChainConfig,
+}
+
+func main() {
+	if err := run(flag.CommandLine, os.Args[1:]); err != nil {
+		fmt.Fprintf(os.Stderr, "error: %s\n", err)
+		os.Exit(1)
+	}
+}
+
+func run(fs *flag.FlagSet, args []string) error {
+	var (
+		rpcURL            string
+		displayOps        bool
+		displayStaticcall bool
+		overrideIndex     int
+		decodeABI         bool
+	)
+	// parse flags
+	fs.StringVar(&rpcURL, "rpc", "http://localhost:8545", "RPC endpoint")
+	fs.BoolVar(&displayOps, "ops", false, "Display opcodes")
+	fs.BoolVar(&displayStaticcall, "staticcall", false, "Display STATICCALL's")
+	fs.IntVar(&overrideIndex, "i", -1, "Override transaction index")
+	fs.BoolVar(&decodeABI, "abi", false, "Decode ABI")
+	fs.Usage = func() {
+		fmt.Fprintln(fs.Output(), "usage: trace [flags] [tx]")
+		flag.PrintDefaults()
+	}
+	fs.Parse(args)
+
+	// parse args
+	if flag.NArg() != 1 {
+		flag.Usage()
+		return fmt.Errorf("missing tx hash")
+	}
+	txHash := common.HexToHash(flag.Arg(0))
+
+	// connect to RPC endpoint
+	client, err := w3.Dial(rpcURL)
+	if err != nil {
+		return fmt.Errorf("failed to connect to RPC endpoint: %w", err)
+	}
+
+	// populate overrides
+	o := overrides{}
+	if overrideIndex >= 0 {
+		o.Index = &overrideIndex
+	}
+
+	tracer := hooks.NewCallTracer(os.Stdout, &hooks.CallTracerOptions{
+		ShowOp:         func(op byte, pc uint64, addr common.Address) bool { return displayOps },
+		ShowStaticcall: displayStaticcall,
+		DecodeABI:      decodeABI,
+	})
+
+	if err := execTrace(client, txHash, o, tracer); err != nil {
+		return fmt.Errorf("failed to execute trace: %w", err)
+	}
+	return nil
+}
+
+func execTrace(client *w3.Client, txHash common.Hash, o overrides, tracer *tracing.Hooks) error {
+	// fetch tx and its receipt
+	var (
+		tx      *types.Transaction
+		receipt *types.Receipt
+		chainID uint64
+	)
+	if err := client.Call(
+		eth.Tx(txHash).Returns(&tx),
+		eth.TxReceipt(txHash).Returns(&receipt),
+		eth.ChainID().Returns(&chainID),
+	); err != nil {
+		return fmt.Errorf("fetch tx and receipt: %w", err)
+	}
+
+	// fetch block
+	var block *types.Block
+	if err := client.Call(
+		eth.BlockByNumber(receipt.BlockNumber).Returns(&block),
+	); err != nil {
+		return fmt.Errorf("fetch block: %w", err)
+	}
+
+	config := chainConfigs[chainID]
+	signer := types.MakeSigner(config, block.Number(), block.Time())
+
+	// prepare fetcher and chain
+	fetcher := w3vm.NewRPCFetcher(client, new(big.Int).Sub(receipt.BlockNumber, w3.Big1))
+	vm, err := w3vm.New(
+		w3vm.WithFetcher(fetcher),
+		w3vm.WithHeader(block.Header()),
+		w3vm.WithChainConfig(config),
+	)
+	if err != nil {
+		return fmt.Errorf("create vm: %w", err)
+	}
+
+	// index of the last tx to apply before the target tx (if -1 then apply none)
+	prestateEndIndex := int(receipt.TransactionIndex)
+	if o.Index != nil && *o.Index < prestateEndIndex {
+		prestateEndIndex = *o.Index
+	}
+
+	// prefetch state asynchronously
+	var prefetch []chan struct{}
+	if prestateEndIndex > 0 {
+		prefetch = make([]chan struct{}, prestateEndIndex)
+	}
+
+	for i := range prestateEndIndex {
+		tx := block.Transactions()[i]
+		prefetch[i] = make(chan struct{})
+		go func(tx *types.Transaction, ch chan struct{}) {
+			tempVM, _ := w3vm.New(
+				w3vm.WithFetcher(fetcher),
+				w3vm.WithHeader(block.Header()),
+				w3vm.WithChainConfig(config),
+			)
+			msg := new(w3types.Message).MustSetTx(tx, signer)
+			tempVM.Apply(msg)
+
+			close(ch) // signal that the tx has been prefetched
+		}(tx, prefetch[i])
+	}
+
+	// apply all prestate txs
+	for i := range prestateEndIndex {
+		<-prefetch[i]
+		msg := new(w3types.Message).MustSetTx(block.Transactions()[i], signer)
+		vm.Apply(msg)
+	}
+	// apply target tx
+	_, err = vm.ApplyTx(tx, tracer)
+
+	return err
+}
+
+// overrides stores overrides for the tx execution.
+type overrides struct {
+	Index *int // transaction index in the block
+}

From ee3c31b5071930bd2489ecc68efb070e8d319426 Mon Sep 17 00:00:00 2001
From: lmittmann <lmittmann@users.noreply.github.com>
Date: Thu, 3 Apr 2025 09:40:35 +0200
Subject: [PATCH 2/2] add README

---
 cmd/trace/README.md | 9 +++++++++
 1 file changed, 9 insertions(+)
 create mode 100644 cmd/trace/README.md

diff --git a/cmd/trace/README.md b/cmd/trace/README.md
new file mode 100644
index 0000000..6f1cf4b
--- /dev/null
+++ b/cmd/trace/README.md
@@ -0,0 +1,9 @@
+# trace
+
+`trace` is a CLI tool for tracing Ethereum transactions.
+
+```
+go install github.com/lmittmann/w3/cmd/trace@feat/trace-cli
+```
+
+## Usage