adds StateManager wrapper for reading at past state roots

reading the confirmed balance (for any confirmation range) for an account will
require reading from the state trie at a past state root

adds a wrapper function, withStateRoot, to temporarily set the state root of the
stateManager, execute a handler function to read from the stateManager at that
root, and finally restore the root to its current value

defines getAccount and getBalance on the IronfishEvm using withStateRoot

some RPC methods, like eth_getAccount and eth_getBalance, will require this
functionality

Author: Hugh Cunningham

ironfish/src/evm/evm.test.ts

@@ -3,6 +3,7 @@
  * file, You can obtain one at https://mozilla.org/MPL/2.0/. */
 import { LegacyTransaction } from '@ethereumjs/tx'
 import { Account as EthAccount, Address } from '@ethereumjs/util'
+import { generateKey } from '@ironfish/rust-nodejs'
 import { Assert } from '../assert'
 import { createNodeTest, useAccountFixture } from '../testUtilities'
 import { EvmStateEncoding, HexStringEncoding } from './database'
@@ -66,4 +67,48 @@ describe('IronfishEvm', () => {
       expect(dbSizeAfter).toEqual(dbSizeBefore)
     })
   })
+
+  describe('getBalance', () => {
+    const nodeTest = createNodeTest()
+
+    it('fetches the account balance at the current state root', async () => {
+      const key = generateKey()
+
+      const address = Address.fromPrivateKey(Buffer.from(key.spendingKey, 'hex'))
+
+      const { node } = nodeTest
+
+      await node.chain.blockchainDb.stateManager.checkpoint()
+      await node.chain.blockchainDb.stateManager.putAccount(address, new EthAccount(0n, 10n))
+      await node.chain.blockchainDb.stateManager.commit()
+
+      const balance = await node.chain.evm.getBalance(address)
+
+      expect(balance).toEqual(10n)
+    })
+
+    it('fetches the account balance at the past state roots', async () => {
+      const key = generateKey()
+
+      const address = Address.fromPrivateKey(Buffer.from(key.spendingKey, 'hex'))
+
+      const { node } = nodeTest
+
+      await node.chain.blockchainDb.stateManager.checkpoint()
+      await node.chain.blockchainDb.stateManager.putAccount(address, new EthAccount(0n, 10n))
+      await node.chain.blockchainDb.stateManager.commit()
+
+      const stateRoot = await node.chain.blockchainDb.stateManager.getStateRoot()
+
+      await node.chain.blockchainDb.stateManager.checkpoint()
+      await node.chain.blockchainDb.stateManager.putAccount(address, new EthAccount(0n, 20n))
+      await node.chain.blockchainDb.stateManager.commit()
+
+      const pastBalance = await node.chain.evm.getBalance(address, stateRoot)
+      expect(pastBalance).toEqual(10n)
+
+      const currentBalance = await node.chain.evm.getBalance(address)
+      expect(currentBalance).toEqual(20n)
+    })
+  })
 })

ironfish/src/evm/evm.ts

@@ -3,7 +3,7 @@
  * file, You can obtain one at https://mozilla.org/MPL/2.0/. */
 import { Block } from '@ethereumjs/block'
 import { EVM, Log } from '@ethereumjs/evm'
-import { Address, hexToBytes } from '@ethereumjs/util'
+import { Account, Address, hexToBytes } from '@ethereumjs/util'
 import { RunTxOpts, RunTxResult, VM } from '@ethereumjs/vm'
 import ContractArtifact from '@ironfish/ironfish-contracts'
 import { Asset, generateKeyFromPrivateKey } from '@ironfish/rust-nodejs'
@@ -153,6 +153,17 @@ export class IronfishEvm {
 
     return asset.id()
   }
+
+  async getAccount(address: Address, stateRoot?: Uint8Array): Promise<Account | undefined> {
+    return this.blockchainDb.stateManager.withStateRoot(stateRoot, async () => {
+      return this.blockchainDb.stateManager.getAccount(address)
+    })
+  }
+
+  async getBalance(address: Address, stateRoot?: Uint8Array): Promise<bigint | undefined> {
+    const account = await this.getAccount(address, stateRoot)
+    return account?.balance
+  }
 }
 
 export type EvmShield = {

ironfish/src/evm/stateManager.ts

@@ -26,4 +26,21 @@ export class IronfishStateManager extends DefaultStateManager {
       common: this.common,
     })
   }
+
+  async withStateRoot<TResult>(
+    stateRoot: Uint8Array | undefined,
+    handler: () => Promise<TResult>,
+  ): Promise<TResult> {
+    const currentRoot = await this.getStateRoot()
+
+    if (stateRoot) {
+      await this.setStateRoot(stateRoot)
+    }
+
+    try {
+      return handler()
+    } finally {
+      await this.setStateRoot(currentRoot)
+    }
+  }
 }