Set up the environment

Prerequisites

Before you start, complete the following prerequisites:

Install Foundry by running this command:

curl -L https://foundry.paradigm.xyz | bash \ 
foundryup

Set up a Warden account on a local chain. Note down your private key.
Make sure the chain is running. You can start it by running wardend start in a separate terminal window.

1. Create a Foundry project

Create a new directory and initialize a new Foundry project:

mkdir warden-http-examples
cd warden-http-examples
forge init

2. Create interfaces

Create interfaces for interacting with the x/async precompile:

Create an src/interfaces directory:
```
mkdir -p src/interfaces
```

In the new directory, create a file IAsync.sol:

warden-http-examples/src/interfaces/IAsync.sol
// SPDX-License-Identifier: UNLICENSED
pragma solidity ^0.8.25;

address constant IASYNC_PRECOMPILE_ADDRESS = 0x0000000000000000000000000000000000000903;   
IAsync constant IASYNC_CONTRACT = IAsync(IASYNC_PRECOMPILE_ADDRESS);

struct FutureResponse {
    uint64 id;
    bytes output;
    string error;
}

struct FutureResult {
    FutureResponse result;
}

struct FutureByIdResponse {
    FutureResult futureResponse;
}

interface IAsync {
    function addFuture(string calldata handler, bytes calldata input, address callback) external returns (uint64);
    function futureById(uint64 id) external view returns (FutureByIdResponse memory);
}

tip

To learn more about the interface for interacting with x/async, see Interact with x/async.

Next, create a second interface, Http.sol:

warden-http-examples/src/interfaces/Http.sol
// SPDX-License-Identifier: UNLICENSED
pragma solidity ^0.8.25;

struct Request {
    string url;
    string method;
    string body;
    string[] headers;
}

struct Response {
    uint256 status;
    bytes body;
    string[] headers;
}

3. Configure Foundry

Update your foundry.toml file to use the Paris EVM version, which is required for Warden:

[profile.default]
src = "src"
out = "out"
libs = ["lib"]
evm_version = "paris"

4. Set environment variables

Set your private key and the RPC URL as environmental variables:

export PRIVATE_KEY=your-private-key
export RPC_URL=http://localhost:8545

Now you're ready to start creating smart contracts that make HTTP requests!

Next steps

To implement simple HTTP requests to different APIs, follow this guide: Implement HTTP requests.

Prerequisites​

1. Create a Foundry project​

2. Create interfaces​

3. Configure Foundry​

4. Set environment variables​

Next steps​