Onchain Offchain Programming Model

If you've followed along from the previous tutorial, you'll have deployed a simple contract which outlines two onchain and offchain functions for a Suapp on SUAVE. It should look like this:

// SPDX-License-Identifier: Unlicense
pragma solidity ^0.8.8;

contract MyFirstSuapp { 
    function onchain() public {}

    function offchain() public pure returns (bytes memory) {
        /* This is where you will write all your compute-heavy,
        off-chain logic to be done in a Kettle */
        return abi.encodeWithSelector(this.onchain.selector);
    }
}

We'd now like to interact with our deployed contract. The spell tool we used to deploy the contract can also be used to send confidential compute requests. Using the address your contract was deployed to, you can use spell to call any function you like.

In this case, we'll get our contract to run "offchain" computation (even though we have yet to define exactly what that should be). From the root of your suapp directory we first created, run:

suave-geth spell conf-request <your_contract_address> 'offchain()'

If you built suave-geth from source, you may need to specify the full path:

./<path_to_suave-geth>/build/bin/suave-geth spell conf-request <your_contract_address> 'offchain()'

It should print a result like this to your console:

INFO [03-26|10:21:30.148] Running with local devchain settings 
INFO [03-26|10:21:30.148] Contract at address 0xFcdbc6055c5C36dBc326F308ed74fA8cB00771a6 
INFO [03-26|10:21:30.148] Sending offchain confidential compute request kettle=0xB5fEAfbDD752ad52Afb7e1bD2E40432A485bBB7F
INFO [03-26|10:21:30.153] Hash of the result onchain transaction   hash=0xa38ef6d191f273056ec967f1308752ed48a45376b059c43be3b5d2f47ef5f25f
INFO [03-26|10:21:30.153] Waiting for the transaction to be mined... 
INFO [03-26|10:21:30.256] Transaction mined                        status=1 blockNum=6

As our offchain() function doesn't do anything yet, there isn't much to see here. That said, you have already deployed your first contract, and sent your first confidential request to it! We are well on the way to building our first functional SUAPP and understanding a new paradigm for public blockchains...

Try to Extend Your Contract

Now, for a Suapp which defines something like an orderflow auction, we want our offchain component to emit information about user trades for searchers to construct backruns, as well as information about successful backruns merged with user trades for builders to construct blocks.

So, let's try add an event and see if we can emit it from our offchain() function:

// SPDX-License-Identifier: Unlicense
// SPDX-License-Identifier: Unlicense
pragma solidity ^0.8.8;

contract MyFirstSuapp { 
    event OffchainEvent(uint256 num);

    function onchain() public {}

    function offchain() public returns (bytes memory) {
        emit OffchainEvent(1);
        emit OffchainEvent(2);

        return abi.encodeWithSelector(this.onchain.selector);
    }
}

Now, let's compile and redeploy this contract, and then cast the same spell as we did above to see what happens:

forge build

suave-geth spell deploy MyFirstSuapp.sol:MyFirstSuapp

suave-geth spell conf-request <your_new_contract_address> 'offchain()'

The logs printed to your console should still look the same:

INFO [03-26|10:30:27.896] Running with local devchain settings 
INFO [03-26|10:30:27.896] Contract at address 0xB6BbB7dccc69CDc5BCE294aeBeD89684b339E3e4 
INFO [03-26|10:30:27.896] Sending offchain confidential compute request kettle=0xB5fEAfbDD752ad52Afb7e1bD2E40432A485bBB7F
INFO [03-26|10:30:27.900] Hash of the result onchain transaction   hash=0x3e884e80e455bca7fe0438529729e74e7592c5a2766c811e5751e14e3f98d82a
INFO [03-26|10:30:27.900] Waiting for the transaction to be mined... 
INFO [03-26|10:30:28.004] Transaction mined                        status=1 blockNum=8

What's going on here? Well, we can't emit the results of offchain computation directly onchain, because that leaks whatever happened in the computation, which is precisely what we want to avoid doing.

Using SUAVE-STD

If we want the relevant part of the results of our offchain computation to result in things happening onchain, we need to be a little more clever with how we write our contracts.

In order to make this easy, we maintain a useful library called SUAVE-STD which enables you to do anything from emitting logs (like we're trying to do in this tutorial), to making arbitrary http calls, using Chat GPT in your contracts, encoding and decoding JSON, RLP encoding/decoding transactions, and doing various other commonly useful things.

First, you'll need to add and commit the changes you've made already before we can install SUAVE-STD:

git add . && git commit -m "my first suapp"

Now you can install our friendly helper library in your suapp directory:

forge install flashbots/suave-std

You can import the basic Suapp.sol contract from the SUAVE-STD library to help with emitting logs. This comes along with a modifier called emitOffchainLogs which will enable you to emit any logs specified in offchain functions from the onchain function selected in the return statement. To see this in action, modify MyFirstSuapp.sol to look like this:

// SPDX-License-Identifier: Unlicense
pragma solidity ^0.8.13;

import "suave-std/Suapp.sol";

contract MyFirstSuapp is Suapp { 
    event OffchainEvent(uint256 num);

    function onchain() public emitOffchainLogs {}

    function offchain() public returns (bytes memory) {
        emit OffchainEvent(1);
        emit OffchainEvent(2);

        return abi.encodeWithSelector(this.onchain.selector);
    }
}

You'll need to compile, redeploy and cast another spell to your new contract:

forge build

suave-geth spell deploy MyFirstSuapp.sol:MyFirstSuapp

suave-geth spell conf-request <your_new_contract_address> 'offchain()'

Now, you should see a result like this printed to your console:

INFO [03-26|10:48:38.628] Running with local devchain settings 
INFO [03-26|10:48:38.628] Contract at address 0x2D09719D6f4fA3AAe6b43328eB150a6902491713 
INFO [03-26|10:48:38.628] Sending offchain confidential compute request kettle=0xB5fEAfbDD752ad52Afb7e1bD2E40432A485bBB7F
INFO [03-26|10:48:38.633] Hash of the result onchain transaction   hash=0x25965c7866aa81489c0de0ae9928c3f3e7d9e8f85288aca1c9839e672a5bf009
INFO [03-26|10:48:38.633] Waiting for the transaction to be mined... 
INFO [03-26|10:48:38.736] Transaction mined                        status=1 blockNum=10
INFO [03-26|10:48:38.753] Logs emitted in the onchain transaction  numLogs=2
INFO [03-26|10:48:38.753] Log emitted                              name=OffchainEvent(uint256) num=1
INFO [03-26|10:48:38.753] Log emitted                              name=OffchainEvent(uint256) num=2

Congratulations! You have deployed a contract, sent it various confidential requests, and begun learning how to use SUAVE-STD to handle the requirements of programming Suapps with both onchain and offchain components! 💃

Onchain Offchain Programming Model

Try to Extend Your Contract​

Using SUAVE-STD​

Try to Extend Your Contract

Using SUAVE-STD