3 - X-Talk Flow Cross Chain Contract

Getting to Know the X-Talk Cross-Chain Swap Demo Template:

This guide will walk you through the basics of a demo template that simplifies cross-chain swaps.

You can find the contract's code in the l1x-contracts directory, shown below:

exa -T -L 1 ./l1x-contracts
	./l1x-contracts
	├── source_registry
	└── xtalk_swap_flow

The purpose of this demo template is to make cross-chain swaps less complicated for you. We will explain how it works in a step-by-step manner. Let's dive in!

Step 1: Setting Up Your Environment

• 1.1. Create an empty folder for this demonstration:

   $ mkdir -p $HOME/l1x-home/l1x-demo-home/

• 1.2. Change your current directory to the newly created folder:

  $ cd $HOME/l1x-home/l1x-demo-home/

Step 2: Download the Demo Template

• 2.1. Make sure you can access the l1x-forge tool from your command line. If you don't have l1x-forge installed, follow the instructions in Step 2: Checking the L1X Tool before proceeding.

• 2.2. Use the l1x-forge command to create a new project workspace. We'll name it l1x_demo03_cross_chain_swap and use the template l1x-cross-chain-swap:

  $ l1x-forge new --name l1x_demo03_cross_chain_swap --template l1x-cross-chain-swap

• 2.3. After running the command, you'll receive a confirmation message indicating the successful creation of the "l1x_demo02_erc20_cross_call" contract:

  Created contract l1x_demo03_cross_chain_swap

• 2.4. Your workspace will now be populated with content from the template.

   	$ exa -T -L 1 ./l1x_demo03_cross_chain_swap
   		./l1x_demo03_cross_chain_swap
   		├── Cargo.lock
   		├── Cargo.toml
   		├── devbox-services-devnode.log
   		├── devbox.json
   		├── devbox.lock
   		├── devnet-services-dc.yml
   		├── l1x-conf
   		├── l1x-contracts
   		├── process-compose-devnode.yaml
   		├── README.md
   		├── rust-toolchain.toml
   		└── rustfmt.toml

Step 3: Starting with Workspace Workflow Script Commands

• 3.1. Introduction to Devbox Shell and Workflow Commands

  If you're new to the l1x-sde template workspace, it's a good idea to familiarize yourself with the basics of the devbox shell and workflow commands. This will help you get started more smoothly. You can review the following links for an overview:

  • Step 4: Understanding Configuration Files and Default Settings

  • Step 5: Getting Started with the Devbox Shell

• 3.2. Default Commands to Begin With

  To start using the workspace, there are some default commands you can use:

  • Activate the Shell: To access the devbox shell, simply enter the following command in your terminal:

  $ devbox shell

  • List Default Commands: To see a list of the built-in default commands available in the devbox shell, you can use the following command:

    	(devbox)$ devbox run -l | sort
    	* 01_init_setup
    	* 01_teardown_setup
    	* 02_check_chain_state
    	* 02_check_devnet_db_state
    	* 02_prune_devnode
    	* 02_start_devnode
    	* 02_stop_devnode
    	* 03_00_start_monitor_services_cmd
    	* 03_01_start_monitor_services_leader
    	* 03_02_start_monitor_services_regular1
    	* 03_03_start_monitor_services_regular2
    	* 03_04_stop_monitor_services
    	* 04_01_start_monitor_signer_node
    	* 10_00_compile_ebpf_cmd
    	* 10_01_compile_ebpf
    	* 11_clean_logs
    	* 11_clean_objs
    	* 18_cli_ro_call_cmd
    	* 18_cli_ro_get_sources_from_registry
    	* 18_cli_sub_txn_register_source_registry
    	* 40_cli_deploy_ebpf
    	* 40_cli_deploy_ebpf_cmd
    	* 41_cli_init_ebpf
    	* 41_cli_init_ebpf_cmd
    	* 60_forge_install_ebpf_cmd_force_deploy
    	* 61_forge_install_ebpf_cmd_reuse_deploy
    	* 80_00_forge_install_ebpf_all
    	* 80_01_forge_install_ebpf_source_registry
    	* 80_02_forge_install_ebpf_xtalk_swap_flow
    	Available scripts:

• Initialize the Workspace: To prepare your workspace for building and testing, run:

   (devbox)$ devbox run 01_init_setup

Now you have all the necessary tools and packages to work with the demo template workspace.

Step 4: Building Smart Contracts

Now, let's guide you through the process of building the smart contracts.

• 4.1 Compiling the Contract for l1x-vm

To compile the l1x_evm_cross_contract contract, simply use this command:

(devbox)$ devbox run 10_01_compile_ebpf

Running this command will compile the contract for you and save the compiled files in the ./l1x-artifacts folder automatically.

After executing the command, you'll discover the following files in the ./l1x-artifacts folder:

```shell
	exa -T -L 1 ./l1x-artifacts
		./l1x-artifacts
		├── source_registry.base64
		├── source_registry.ll
		├── source_registry.o
		├── source_registry.versioned.ll
		├── source_registry.wasm
		├── xtalk_swap_flow.base64
		├── xtalk_swap_flow.ll
		├── xtalk_swap_flow.o
		├── xtalk_swap_flow.versioned.ll
		└── xtalk_swap_flow.wasm
```

That's it! We've successfully completed the steps for building smart contracts.

Step 5: Setting Up Local Development Network Services

In this step, we will walk you through the process of configuring local development l1x-chain network.

• 5.1 Choose the Chain Type: To begin, select the "L1X_CFG_CHAIN_TYPE": "local_devnet" option. Next, open a new terminal and activate the devbox shell:

  $ devbox shell

• 5.2 Start the Devnode Services: While in the devbox shell, run the following command:

  (devbox)$ devbox run 02_start_devnode

• 5.3 Wait for Services to Initialize: After executing the previous command, please wait for approximately 160 seconds. During this time, the services will start up and become operational. You will also observe the L1X node beginning to produce blocks.

• 5.4 Verify DevNet Service Status: To ensure that everything is running smoothly, use the following command to check the service status:

  (devbox)$ devbox run 02_check_chain_state

  

  (devbox)$ devbox run 02_check_devnet_db_state

  

• 5.5 Troubleshooting: Occasionally, we might encounter a problem where the l1x-node-client server and the cassandra DB service do not sync properly, as indicated by the state shown in the image below.

• To fix this issue and get your setup back on track, follow these simple steps:

  (devbox)$ devbox run 02_stop_devnode
  (devbox)$ devbox run 02_prune_devnode
  (devbox)$ devbox run 02_start_devnode

These commands will help reset and restart the necessary components. Your setup should work smoothly after completing these steps.

Step 6: Deploying and Creating an Instance From a Compiled Contract

• 6.1: Deploying and Creating a Contract Instance for source_registry.o and xtalk_swap_flow.o on l1x-vm

  To deploy and create a contract instance for source_registry.o and xtalk_swap_flow.o on l1x-vm, you can use the following command:

  (devbox)$ devbox run 80_00_forge_install_ebpf_all

• 6.2: Understanding Traces

  When deploying and creating contract instances, it's important to note the following information from traces, will be helpful for debugging:

  • The payload used for deploying and the deployed address for the source_registry.o contract.

  

  • The payload used for creating an instance and the instance address for the source_registry.o contract.

  

• The payload used for deploying and the deployed address for the xtalk_swap_flow.o contract.

• The payload used for creating an instance and the instance address for the xtalk_swap_flow.o contract.

• 6.3: Contract Address Registry

The addresses for deployed contracts and their instances are automatically updated in the configuration file l1x-conf/config-contract-address-registry.yaml. This registry keeps track of contract addresses.

• 6.4: Updating JSON Payload with New Instance Addresses

Update the following JSON payload with new instance addresses, before proceeding:

```shell
l1x-conf/scripts/012-01-uc-event-registry-register-new-source.json
l1x-conf/scripts/012-02-uc-event-registry-get-source-from.json
```

Section 7: Updating Configuration for Event Listener Monitoring Service via the source_registry.o Contract

• 7.1: Updating the source_registry.o Contract:

1. Update the configuration file for the payload.

The Source Registry has to be updated about information of external Source chain. In this demonstration, it is the Liquidity pool contract deployed on the Ethereum chain at the address `0xDa4140B906044aCFb1aF3b34C94A2803D90e96aA`, along with the instance address of `xtalk_swap_flow.o` and the events to be filtered. This information gets used by L2 layer Event Listener monitoring services.

To make this update, manually edit the payload file located at `l1x-conf/scripts/012-01-uc-event-registry-register-new-source.json`.

1. Run the following command to execute the transaction:

(devbox)$ devbox run 18_cli_sub_txn_register_source_registry

Check the trace log for the following information, which indicates that the transaction has been successfully executed:

1. Run the following command to confirm the updates to the source registry transaction status:

```shell
(devbox)$ devbox run 18_cli_ro_get_sources_from_registry
```

Section 8: Starting L1X L2 Monitoring Services

To start L1X L2 monitoring services, follow each steps in a new devbox shell terminal:

• 8.1: Start the Event Listener "Leader" Service:

   (devbox)$ devbox run 18_cli_ro_get_sources_from_registry

• 8.2: Start the Event Listener "Regular" Service:

   (devbox)$ devbox run 03_02_start_monitor_services_regular1

• 8.3: Understanding Traces:

The trace prints show that the Leader node has discovered peers and begun fetching new blocks from the source Ethereum chain.

• 8.4: Launch the Signer Node Service:

   (devbox)$ devbox run 04_01_start_monitor_signer_node

The trace prints show that the Signer node has started fetching new blocks from the L1X L1 layer.

Section 9: Starting the ERC20 Token Swap

To start the ERC20 Token Swap, follow these steps:

• 9.1: Get Some Test Tokens for Your Wallet

Request some test tokens for your Metamask wallet from the L1X team.

• 9.2: Start the Token Swap on the Source Liquidity Pool Contract

Here's how you can do it:

• Go to the Goerli Testnet Explorer and search for the LP contract at this address: 0xDa4140B906044aCFb1aF3b34C94A2803D90e96aA

• Make sure you are on the correct page before proceeding with the InitiateSwap transaction.

• Connect your web3 wallet (we recommend using MetaMask) and select the account that has the test tokens from the L1X team.

• Execute the InitiateSwap transaction. In this demonstration, use the following arguments when making the InitiateSwap transaction call:

Sender Address: 0x4603e703309Cd6C0b8bada1e724312242ef36ECb
Amount: 100
Network: optimism
Receiver Address: 0x853f409f60D477b5e4ECdfF2f2094D4670AFA0A1
Amount: 100
Destination Address: 0xc31beb2a223435a38141Ee15C157672A9fA2997D

• Wait for the InitiateSwap transaction to complete.

• 9.3: Confirm the Swap

To confirm the swap, follow these steps:

• Find the transaction hash for the swap executed on the Destination Liquidity Pool deployed in Optimism Goerli Testnet. You can locate this in the transaction receipt, which is available in the trace prints of the Signer Node monitoring service.

• Visit Goerli Optimism Testnet Explorer and search for this transaction hash to confirm that your swap was successful.

• Open the contract at the address 0x44436a43330122a61a4877e51ba54084d5bd0ac6 and verify that the tokens have been successfully transferred to the destination address.

Congratulations! You've successfully completed the ERC20 Token Swap process. We hope this guide has been helpful in getting you through it smoothly. If you have any questions or run into any issues, feel free to reach out to our L1X team for assistance. Happy swapping!