event-bridger

POC for ClayNation Cardano - EVM event mapping

Logistics summary

• Contract code: src/EventBridger.sol

• Run tests (needed for gas report) with gas report:

forge test --gas-report -vvv

• Deploy contract on Mumbai:

forge script script/EventBridgerDeployer.s.sol:EventBridgerDeployer --broadcast --chain-id 80001 --rpc-url "https://rpc.ankr.com/polygon_mumbai" --legacy

• Verify contract on Mumbai (add your DEPLOYED_CONTRACT_ADDRESS and POLYSCAN_API_KEY):

forge verify-contract --verifier-url https://api-testnet.polygonscan.com/api/ <DEPLOYED_CONTRACT_ADDRESS> src/EventBridger.sol:EventBridger <POLYSCAN_API_KEY>

Contract overview

EventBridger contract has 4 function:

• emitERC721TransferEvent:
  • emits 1 ERC721 Transfer event
• emitERC721TransferEventBatch:
  • emits as many ERC721 Transfer events as passed to it
  • warning, passing a lot here can make the function run out of gas (a few hundred can work)
  • use this when testing
• emitERC1155TransferSingleEvent
  • emits 1 ERC1155 TransferSingle event, possibly useful for an optimization, ignore for now
• emitERC1155TransferBatchEvent
  • emits 1 ERC1155 TransferBatch event, possibly useful for an optimization, ignore for now

Setup project

Clone repo: git clone --recurse-submodules [email protected]:abarbatei/event-bridger.git

If, for some reason, the /lib/ libraries were not installed then you can manually add them via:

forge install foundry-rs/forge-std
forge install OpenZeppelin/openzeppelin-contracts

Copy .env.example as .env and add your deployer private key DEPLOYER_PRIVATE_KEY (warning as to never share this value or commit it in a project)

Testing project

Simply run: forge test

• if you want to run only a specific test file you can use the --match-path argument

forge test --match-path test/EventBridger.t.sol

• if you want to run only a specific test (or matching pattern test) you can use the --match-test argument

forge test --match-test testEmitERC721

• for extra verbosity add -vvv. vs can be 1 (least verbose) or 3 (most verbose)

Gas report

Gas report is only available for tested functions. To see gas report estimations you would need to actually run tests and add the --gas-report argument

Example output from executing forge test --gas-report -vvv:

Running 3 tests for test/EventBridger.t.sol:CounterTest
[PASS] testEmitERC721() (gas: 15261)
[PASS] testEmitERC721BatchManual() (gas: 12246)
[PASS] testEmitERC721Raw() (gas: 9709)
Test result: ok. 3 passed; 0 failed; finished in 709.88µs
| src/EventBridger.sol:EventBridger contract |                 |      |        |      |         |
|--------------------------------------------|-----------------|------|--------|------|---------|
| Deployment Cost                            | Deployment Size |      |        |      |         |
| 531161                                     | 2688            |      |        |      |         |
| Function Name                              | min             | avg  | median | max  | # calls |
| emitERC721TransferEvent                    | 4482            | 4482 | 4482   | 4482 | 2       |
| emitERC721TransferEventBatch               | 5588            | 5588 | 5588   | 5588 | 1       |

Interpreting report

• under Deployment Cost is the gas value to deploy the contract and the next column has the deployed contract bytecode (bytes) size (Deployment Size)
• then 3rd line holds the names of the columns below
• example, there were 2 calls to the EventBridger::emitERC721TransferEvent function and both cost exactly 4482 in both instances

Deploying contract

In foundry/forge, scripts are also written in Solidity. The script/EventBridgerDeployer.s.sol deploys the contract on-chain.

To dry-run test it execute the command: forge script script/EventBridgerDeployer.s.sol:EventBridgerDeployer

To fully deploy on-chain you need the full arguments:

forge script script/EventBridgerDeployer.s.sol:EventBridgerDeployer --broadcast --chain-id <deployment_chain_id> --rpc-url "<what_RPC_url_to_use>"

Example deployment on Mumbai:

forge script script/EventBridgerDeployer.s.sol:EventBridgerDeployer --broadcast --chain-id 80001 --rpc-url "https://rpc.ankr.com/polygon_mumbai" --legacy

Observations

• add --with-gas-price 4607624000 in case forge cannot estimate deployment gas (or whatever value you set it to)
  • or add --legacy (not needed for Polygon)
• more on forge script commands here
• if an error with too many request appear, change the RPC URL with another from chainlist.org

Verifying contract

In order for us as owners to interact with the contract using blockchain explorers (example https://polygonscan.com/) the contract must be verified.

In order to verify it execute the following command:

forge verify-contract --verifier-url <verifier_url> <deployed_contract_address> src/EventBridger.sol:EventBridger <explorer_api_key>

For Mumbai, the verifier URL is: https://api-testnet.polygonscan.com/api/

In order to get an <explorer_api_key> for Mumbai, you need to create an account (free) on https://polygonscan.com/ , generate a key and use the same key on https://mumbai.polygonscan.com/.

<deployed_contract_address> you get from the deployment operation

Example verification on Mumbai (you still need to change the address to your deployed contract address and add a valid polyscan API key)

forge verify-contract --verifier-url https://api-testnet.polygonscan.com/api/ 0xdeadbeefdeadbeefdeadbeefdeadbeef src/EventBridger.sol:EventBridger ABBABABABABABABABAB