init

.github/workflows/build.yaml

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+name: Build
+
+on:
+  push:
+    #     branches: [ main ]
+    #   pull_request:
+    #     branches: [ main ]
+
+jobs:
+
+  'build-go':
+    name: make build-go
+    runs-on: ubuntu-latest
+    steps:
+
+    - name: Set up Go 1.x
+      uses: actions/setup-go@v2
+      with:
+        go-version: ^1.21
+
+    - name: Check out
+      uses: actions/checkout@v3
+
+    - name: Make build-go
+      run: make build-go
+
+  'build-test-solidity':
+    name: make build-solidity
+    runs-on: ubuntu-latest
+    steps:
+
+    - name: Check out
+      uses: actions/checkout@v3
+      with:
+        submodules: recursive
+
+    - name: Install Foundry
+      uses: foundry-rs/foundry-toolchain@v1
+
+    - name: Make build-solidity
+      run: cd contracts && forge build && forge test

.gitignore

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+.DS_Store
+node_modules
+results
+temp
+.nyc_output
+coverage.json
+*.tsbuildinfo
+**/lcov.info
+
+yarn-error.log
+.yarn/*
+!.yarn/releases
+!.yarn/plugins
+.pnp.*
+
+dist
+artifacts
+cache
+
+packages/contracts-bedrock/deployments/devnetL1
+packages/contracts-bedrock/deployments/anvil
+
+# vim
+*.sw*
+
+# jetbrains
+.idea/
+
+.secrets
+.env
+.env*
+!.env.example
+*.log
+
+.devnet
+
+# Ignore local fuzzing results
+**/testdata/fuzz/
+
+coverage.out
+
+# Ignore bedrock go bindings local output files
+op-bindings/bin
+op-exporter
+
+
+__pycache__
+
+# Ignore echidna artifacts
+crytic-export
+
+# Ignore building artifacts
+build/
+bot
+
+# Ignore the configuration files
+bot.toml

.gitmodules

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+[submodule "contracts/lib/openzeppelin-contracts"]
+	path = contracts/lib/openzeppelin-contracts
+	url = https://github.com/OpenZeppelin/openzeppelin-contracts

Dockerfile

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+FROM --platform=$BUILDPLATFORM golang:1.21.1-alpine3.18 as builder
+
+RUN apk add --no-cache make ca-certificates gcc musl-dev linux-headers git jq bash
+
+COPY ./go.mod /app/go.mod
+COPY ./go.sum /app/go.sum
+
+WORKDIR /app
+
+RUN go mod download
+
+COPY ./core        /app/core
+COPY ./cmd         /app/cmd
+COPY ./Makefile    /app/Makefile
+COPY ./bot.toml    /app/bot.toml
+
+WORKDIR /app/
+
+RUN make build-go
+
+FROM alpine:3.18
+
+COPY --from=builder /app/bot /usr/local/bin
+COPY --from=builder /app/bot.toml /app/bot.toml
+
+WORKDIR /app
+
+CMD ["bot", "run", "--config", "/app/bot.toml"]

Makefile

@@ -0,0 +1,19 @@
+GITCOMMIT := $(shell git rev-parse HEAD)
+GITDATE := $(shell git show -s --format='%ct')
+
+LDFLAGSSTRING +=-X main.GitCommit=$(GITCOMMIT)
+LDFLAGSSTRING +=-X main.GitDate=$(GITDATE)
+LDFLAGS := -ldflags "$(LDFLAGSSTRING)"
+
+build-go:
+	env GO111MODULE=on go build -v $(LDFLAGS) ./cmd/bot
+
+build-solidity:
+	pushd contracts; \
+	forge build; \
+	popd;
+
+.PHONY: \
+	bot  \
+	build-go \
+	build-solidity

README.md

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+# opbnb-bridge-bot
+
+## Description
+
+The opbnb-bridge-bot project primarily maintains a Layer2 contract named `L2StandardBridgeBot`. This contract, when called, initiates withdrawal transactions and collects a fixed fee for every withdrawals. The project promises that after the withdrawal transaction has can be proven and finalized after the required time window, a third-party account would complete the corresponding L1 proven withdrawal transactions and L1 finalized withdrawal transactions, thus completing the entire withdrawal process.
+
+## Motivation
+
+![image](./assets/optimism-withdraw-flow.png)
+
+A withdrawal request must be completed in three steps:
+
+1. Send a L2 initiating transaction
+2. Send the L1 proven transaction after the proposer submits the next L2 output root
+3. Send L1 finalized transaction after the challenge window has passed
+
+Completing these three steps might not be a good user experience. Firstly, users need to send 3 transactions; secondly, they need to wait 2 periods before sending the next transaction.
+
+### See also
+
+- opBNB testnet bridge: https://opbnb-testnet-bridge.bnbchain.org
+
+- withdrawal example: https://testnet.opbnbscan.com/tx/0xadb6b8d8bffb4dc7177ef1e27e202035f0861a71521c3cdff66a4aeb4464e501
+
+## Design Principle and Working Mechanism
+
+This project consists of an on-chain contract [`contracts/src/L2StandardBridgeBot.sol`](contracts/src/L2StandardBridgeBot.sol) and [an off-chain bot](./cmd/bot/run.go#L67-L68).
+
+The `L2StandardBridgeBot` contract provides a `withdrawTo` function, which charges a fixed fee for every execution and then forwards the call to the `L2StandardBridge.withdraw`.
+
+The off-chain bot watches the `L2StandardBridgeBot.WithdrawTo` events and based on these events, re-constructs the corresponding withdrawals. We name these withdrawals as **bot-delegated withdrawals**. As time go out of the bot-delegated withdrawal's proven and finalized time window, our bot will send proven and finalized transactions to complete the entire withdrawal process.
+
+references
+- contracts
+    - [L2StandardBridge.sol](https://github.com/bnb-chain/opbnb/blob/v0.2.2/packages/contracts-bedrock/contracts/L2/L2StandardBridge.sol#L105-L129) which concludes the `withdrawTo` function.
+      - opBNB Mainnet [address](https://opbnbscan.com/address/0x4200000000000000000000000000000000000010).
+      - opBNB Testnet [address](https://testnet.opbnbscan.com/address/0x4200000000000000000000000000000000000010)
+    - [OptimismPortal.sol](https://github.com/bnb-chain/opbnb/blob/v0.2.2/packages/contracts-bedrock/contracts/L1/OptimismPortal.sol) which concludes the `proveWithdrawalTransaction` and `finalizeWithdrawalTransaction` functions.
+      - BSC Mainnet [address](https://bscscan.com/address/0x1876EA7702C0ad0C6A2ae6036DE7733edfBca519).
+      - BSC Testnet [address](https://testnet.bscscan.com/address/0x4386c8abf2009ac0c263462da568dd9d46e52a31)
+- [opbnb bridge](https://opbnb-bridge.bnbchain.org)
+- [tutorial](https://github.com/ethereum-optimism/optimism-tutorial/blob/main/cross-dom-bridge-erc20/README.md) of interacting with bridge with js-sdk.
+
+## User Guide
+
+### Getting Started at opBNB testnet
+
+1. Prepare a PostgreSQL database
+
+```
+docker-compose up -d
+```
+
+2. Compile the off-chain bot and output the artifact to `./bot`
+
+```
+make build-go
+```
+
+3. Run the off-chain bot
+
+```
+OPBNB_BRIDGE_BOT_PRIVKEY=<bot privkey> ./bot --config ./bot.toml
+```
+
+### Deploy and Use Contracts
+
+1. Compile the contract using `forge`
+
+```
+make build-solidity
+```
+
+2. Deploy contract
+
+```
+cd contracts
+
+export DELEGATE_FEE=1000000000000000
+forge create \
+    --rpc-url $OPBNB_TESTNET \
+    --private-key $OP_DEPLOYER_PRIVKEY \
+    src/L2StandardBridgeBot.sol:L2StandardBridgeBot --constructor-args $OP_DEPLOYER_ADDRESS $DELEGATE_FEE
+```
+
+3. Withdraw via the deployed contract
+
+```
+export DELEGATE_FEE=1000000000000000
+export amount=2000000000000001
+export contract_addr=<deployed contract address>
+
+cast send --rpc-url $OPBNB_TESTNET \
+          --private-key $OP_DEPLOYER_PRIVKEY \
+          --value $(($DELEGATE_FEE + $amount)) \
+          $contract_addr \
+          $(cast calldata 'withdrawTo( address _l2Token, address _to, uint256 _amount, uint32 _minGasLimit, bytes calldata _extraData)' 0xDeadDeAddeAddEAddeadDEaDDEAdDeaDDeAD0000 $OP_DEPLOYER_ADDRESS $amount 150469 "")
+```
+
+## License
+
+MIT

bot.toml

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+[rpcs]
+l1-rpc = 
+l2-rpc = 
+
+[db]
+host = "0.0.0.0"
+port = 5434
+user = "db_username"
+password = "db_password"
+name = "db_name"
+
+[l1-contracts]
+address-manager                 = "0x1111111111111111111111111111111111111111"
+system-config                   = "0x406ac857817708eaf4ca3a82317ef4ae3d1ea23b"
+optimism-portal                 = "0x4386c8abf2009ac0c263462da568dd9d46e52a31"
+l2-output-oracle                = "0xff2394bb843012562f4349c6632a0ecb92fc8810"
+l1-cross-domain-messenger       = "0xd506952e78eecd5d4424b1990a0c99b1568e7c2c"
+l1-standard-bridge              = "0x1111111111111111111111111111111111111111"
+# l1-erc721-bridge                = "0x17e1454015bfb3377c75be7b6d47b236fd2ddbe7"
+l1-erc721-bridge                = "0x1111111111111111111111111111111111111111"
+
+[misc]
+l2-standard-bridge-bot = "0x4c3171982cd7f62690f4d6e086b91f434b97332f"
+propose-time-window = 60
+challenge-time-window = 60

cmd/bot/main.go

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+package main
+
+import (
+	"context"
+	"os"
+
+	oplog "github.com/ethereum-optimism/optimism/op-service/log"
+	"github.com/ethereum-optimism/optimism/op-service/opio"
+	"github.com/ethereum/go-ethereum/log"
+	"github.com/ethereum/go-ethereum/params"
+	"github.com/urfave/cli/v2"
+)
+
+var (
+	ConfigFlag = &cli.StringFlag{
+		Name:    "config",
+		Value:   "./bot.toml",
+		Aliases: []string{"c"},
+		Usage:   "path to config file",
+		EnvVars: []string{"BOT_CONFIG"},
+	}
+)
+
+var (
+	GitCommit = ""
+	GitDate   = ""
+)
+
+func main() {
+	// This is the most root context, used to propagate
+	// cancellations to all spawned application-level goroutines
+	ctx, cancel := context.WithCancel(context.Background())
+	go func() {
+		opio.BlockOnInterrupts()
+		cancel()
+	}()
+
+	oplog.SetupDefaults()
+	app := newCli(GitCommit, GitDate)
+	if err := app.RunContext(ctx, os.Args); err != nil {
+		log.Error("application failed", "err", err)
+		os.Exit(1)
+	}
+}
+
+func newCli(GitCommit string, GitDate string) *cli.App {
+	flags := []cli.Flag{ConfigFlag}
+	flags = append(flags, oplog.CLIFlags("OPBNB_BRIDGE_BOT")...)
+	return &cli.App{
+		Name:                 "opbnb-bridge-bot",
+		Version:              params.VersionWithCommit(GitCommit, GitDate),
+		Description:          "opbnb-bridge-bot",
+		EnableBashCompletion: true,
+		Commands: []*cli.Command{
+			{
+				Name:        "run",
+				Flags:       flags,
+				Description: "Runs the indexing service",
+				Action:      runCommand,
+			},
+			{
+				Name:        "version",
+				Description: "print version",
+				Action: func(ctx *cli.Context) error {
+					cli.ShowVersion(ctx)
+					return nil
+				},
+			},
+		},
+	}
+}