Add eth_blobBaseFee RPC endpoint (#3436)

* Add blob base fee

* client: remove unused variables in blobBaseFee test

---------

Co-authored-by: Gabriel Rocheleau <contact@rockwaterweb.com>

packages/client/src/rpc/modules/eth.ts

@@ -452,6 +452,12 @@ export class Eth {
         [validators.rewardPercentiles],
       ]
     )
+
+    this.blobBaseFee = middleware(
+      callWithStackTrace(this.blobBaseFee.bind(this), this._rpcDebug),
+      0,
+      []
+    )
   }
 
   /**
@@ -1317,4 +1323,13 @@ export class Eth {
       reward: rewards.map((r) => r.map(bigIntToHex)),
     }
   }
+
+  /**
+   *
+   * @returns the blob base fee for the next/pending block in wei
+   */
+  async blobBaseFee() {
+    const headBlock = await this._chain.getCanonicalHeadHeader()
+    return bigIntToHex(headBlock.calcNextBlobGasPrice())
+  }
 }

packages/client/test/rpc/eth/blobBaseFee.spec.ts

@@ -0,0 +1,121 @@
+import { Hardfork } from '@ethereumjs/common'
+import { TransactionFactory } from '@ethereumjs/tx'
+import {
+  Address,
+  BIGINT_0,
+  BIGINT_256,
+  blobsToCommitments,
+  commitmentsToVersionedHashes,
+  getBlobs,
+  hexToBytes,
+} from '@ethereumjs/util'
+import { loadKZG } from 'kzg-wasm'
+import { assert, describe, it } from 'vitest'
+
+import genesisJSON from '../../testdata/geth-genesis/eip4844.json'
+import { getRpcClient, setupChain } from '../helpers.js'
+
+import type { Chain } from '../../../src/blockchain/chain.js'
+import type { VMExecution } from '../../../src/execution/vmexecution.js'
+const method = 'eth_blobBaseFee'
+
+const privateKey = hexToBytes('0x45a915e4d060149eb4365960e6a7a45f334393093061116b197e3240065ff2d8')
+const accountAddress = Address.fromPrivateKey(privateKey)
+const produceBlockWith4844Tx = async (
+  execution: VMExecution,
+  chain: Chain,
+  blobsCount: number[]
+) => {
+  const kzg = await loadKZG()
+  // 4844 sample blob
+  const sampleBlob = getBlobs('hello world')
+  const commitment = blobsToCommitments(kzg, sampleBlob)
+  const blobVersionedHash = commitmentsToVersionedHashes(commitment)
+
+  const { vm } = execution
+  const account = await vm.stateManager.getAccount(accountAddress)
+  let nonce = account?.nonce ?? BIGINT_0
+  const parentBlock = await chain.getCanonicalHeadBlock()
+  const vmCopy = await vm.shallowCopy()
+  // Set block's gas used to max
+  const blockBuilder = await vmCopy.buildBlock({
+    parentBlock,
+    headerData: {
+      timestamp: parentBlock.header.timestamp + BigInt(1),
+    },
+    blockOpts: {
+      calcDifficultyFromHeader: parentBlock.header,
+      putBlockIntoBlockchain: false,
+    },
+  })
+  for (let i = 0; i < blobsCount.length; i++) {
+    const blobVersionedHashes = []
+    const blobs = []
+    const kzgCommitments = []
+    const to = Address.zero()
+    if (blobsCount[i] > 0) {
+      for (let blob = 0; blob < blobsCount[i]; blob++) {
+        blobVersionedHashes.push(...blobVersionedHash)
+        blobs.push(...sampleBlob)
+        kzgCommitments.push(...commitment)
+      }
+    }
+    await blockBuilder.addTransaction(
+      TransactionFactory.fromTxData(
+        {
+          type: 3,
+          gasLimit: 21000,
+          maxFeePerGas: 0xffffffff,
+          maxPriorityFeePerGas: BIGINT_256,
+          nonce,
+          to,
+          blobVersionedHashes,
+          blobs,
+          kzgCommitments,
+          maxFeePerBlobGas: BigInt(1000),
+        },
+        { common: vmCopy.common }
+      ).sign(privateKey)
+    )
+    nonce++
+  }
+
+  const block = await blockBuilder.build()
+  await chain.putBlocks([block], true)
+  await execution.run()
+}
+
+describe(method, () => {
+  it('call', async () => {
+    const kzg = await loadKZG()
+    const { server } = await setupChain(genesisJSON, 'post-merge', {
+      engine: true,
+      hardfork: Hardfork.Cancun,
+      customCrypto: {
+        kzg,
+      },
+    })
+
+    const rpc = getRpcClient(server)
+    const res = await rpc.request(method, [])
+    assert.equal(res.result, '0x1')
+  })
+
+  it('call with more realistic blockchain', async () => {
+    const kzg = await loadKZG()
+    const { server, execution, chain } = await setupChain(genesisJSON, 'post-merge', {
+      engine: true,
+      hardfork: Hardfork.Cancun,
+      customCrypto: {
+        kzg,
+      },
+    })
+
+    for (let i = 0; i < 10; i++) {
+      await produceBlockWith4844Tx(execution, chain, [6])
+    }
+    const rpc = getRpcClient(server)
+    const res = await rpc.request(method, [])
+    assert.equal(res.result, '0x3')
+  })
+})