How can I retrieve the baseFeePerGas value for historical blocks on Astar?

Question

I want to calculate fees for historical EIP-1559 transactions on Astar EVM. For this, I need to use the GasPrice formula:

GasPrice = BaseFee + MaxPriorityFeePerGas < MaxFeePerGas ? 
        BaseFee + MaxPriorityFeePerGas : 
        MaxFeePerGas;

MaxPriorityFeePerGas and MaxFeePerGas values are available in transaction data and are set by the user but BaseFee value is not. As far as I know this value is set by the system and is dynamic. Is there a way to retrieve this BaseFee value for historical blocks? Is this information stored in the blockchain and can it be read directly?

Solution:

In order to get baseFee value using the Ethereum API see @gluneau answer.

When it comes to the Substrate API: In the Astar blockchain, there exists a BaseFee pallet, which stores the baseFee value for each block. We can access its storage to fetch the baseFee value for any specific block.

For instance, with the Substrate Sidecar API, we can use the following path to obtain the baseFeePerGas value for block number 1300000:

/pallets/base-fee/storage/BaseFeePerGas?at=1300000

Answer 1

Here is a method to get historical baseFeePerGas

const { ethers } = require("ethers");

async function getBaseFee(blockNumber) {
    const rpc = "https://evm.astar.network"
    let provider = new ethers.providers.JsonRpcProvider(rpc);
    let block = await provider.getBlock(blockNumber);
    return block.baseFeePerGas;
}

let blockNumber = 1300000;  // replace with the block number you're interested in
getBaseFee(blockNumber)
    .then(baseFee => console.log(`Base fee for block ${blockNumber}: ${baseFee}`))
    .catch(err => console.log(err));

I've made also a replit you can play with.