viem
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JavaScript
import * as AbiConstructor from 'ox/AbiConstructor';
import * as AbiFunction from 'ox/AbiFunction';
import { parseAccount } from '../../accounts/utils/parseAccount.js';
import { ethAddress, zeroAddress } from '../../constants/address.js';
import { deploylessCallViaBytecodeBytecode } from '../../constants/contracts.js';
import { BaseError } from '../../errors/base.js';
import { encodeFunctionData, } from '../../utils/abi/encodeFunctionData.js';
import { hexToBigInt } from '../../utils/index.js';
import { createAccessList, } from './createAccessList.js';
import { simulateBlocks, } from './simulateBlocks.js';
const getBalanceCode = '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';
/**
* Simulates execution of a batch of calls.
*
* @param client - Client to use
* @param parameters - {@link SimulateCallsParameters}
* @returns Results. {@link SimulateCallsReturnType}
*
* @example
* ```ts
* import { createPublicClient, http, parseEther } from 'viem'
* import { mainnet } from 'viem/chains'
* import { simulateCalls } from 'viem/actions'
*
* const client = createPublicClient({
* chain: mainnet,
* transport: http(),
* })
*
* const result = await simulateCalls(client, {
* account: '0x5a0b54d5dc17e482fe8b0bdca5320161b95fb929',
* calls: [{
* {
* data: '0xdeadbeef',
* to: '0x70997970c51812dc3a010c7d01b50e0d17dc79c8',
* },
* {
* to: '0x70997970c51812dc3a010c7d01b50e0d17dc79c8',
* value: parseEther('1'),
* },
* ]
* })
* ```
*/
export async function simulateCalls(client, parameters) {
const { blockNumber, blockTag, calls, stateOverrides, traceAssetChanges, traceTransfers, validation, } = parameters;
const account = parameters.account
? parseAccount(parameters.account)
: undefined;
if (traceAssetChanges && !account)
throw new BaseError('`account` is required when `traceAssetChanges` is true');
// Derive bytecode to extract ETH balance via a contract call.
const getBalanceData = account
? AbiConstructor.encode(AbiConstructor.from('constructor(bytes, bytes)'), {
bytecode: deploylessCallViaBytecodeBytecode,
args: [
getBalanceCode,
AbiFunction.encodeData(AbiFunction.from('function getBalance(address)'), [account.address]),
],
})
: undefined;
// Fetch ERC20/721 addresses that were "touched" from the calls.
const assetAddresses = traceAssetChanges
? await Promise.all(parameters.calls.map(async (call) => {
if (!call.data && !call.abi)
return;
const { accessList } = await createAccessList(client, {
account: account.address,
...call,
data: call.abi ? encodeFunctionData(call) : call.data,
});
return accessList.map(({ address, storageKeys }) => storageKeys.length > 0 ? address : null);
})).then((x) => x.flat().filter(Boolean))
: [];
const resultsStateOverrides = stateOverrides?.map((override) => {
if (override.address === account?.address)
return {
...override,
nonce: 0,
};
return override;
});
const blocks = await simulateBlocks(client, {
blockNumber,
blockTag: blockTag,
blocks: [
...(traceAssetChanges
? [
// ETH pre balances
{
calls: [{ data: getBalanceData }],
stateOverrides,
},
// Asset pre balances
{
calls: assetAddresses.map((address, i) => ({
abi: [
AbiFunction.from('function balanceOf(address) returns (uint256)'),
],
functionName: 'balanceOf',
args: [account.address],
to: address,
from: zeroAddress,
nonce: i,
})),
stateOverrides: [
{
address: zeroAddress,
nonce: 0,
},
],
},
]
: []),
{
calls: [...calls, {}].map((call, index) => ({
...call,
from: account?.address,
nonce: index,
})),
stateOverrides: resultsStateOverrides,
},
...(traceAssetChanges
? [
// ETH post balances
{
calls: [{ data: getBalanceData }],
},
// Asset post balances
{
calls: assetAddresses.map((address, i) => ({
abi: [
AbiFunction.from('function balanceOf(address) returns (uint256)'),
],
functionName: 'balanceOf',
args: [account.address],
to: address,
from: zeroAddress,
nonce: i,
})),
stateOverrides: [
{
address: zeroAddress,
nonce: 0,
},
],
},
// Decimals
{
calls: assetAddresses.map((address, i) => ({
to: address,
abi: [
AbiFunction.from('function decimals() returns (uint256)'),
],
functionName: 'decimals',
from: zeroAddress,
nonce: i,
})),
stateOverrides: [
{
address: zeroAddress,
nonce: 0,
},
],
},
// Token URI
{
calls: assetAddresses.map((address, i) => ({
to: address,
abi: [
AbiFunction.from('function tokenURI(uint256) returns (string)'),
],
functionName: 'tokenURI',
args: [0n],
from: zeroAddress,
nonce: i,
})),
stateOverrides: [
{
address: zeroAddress,
nonce: 0,
},
],
},
// Symbols
{
calls: assetAddresses.map((address, i) => ({
to: address,
abi: [AbiFunction.from('function symbol() returns (string)')],
functionName: 'symbol',
from: zeroAddress,
nonce: i,
})),
stateOverrides: [
{
address: zeroAddress,
nonce: 0,
},
],
},
]
: []),
],
traceTransfers,
validation,
});
const block_results = traceAssetChanges ? blocks[2] : blocks[0];
const [block_ethPre, block_assetsPre, , block_ethPost, block_assetsPost, block_decimals, block_tokenURI, block_symbols,] = traceAssetChanges ? blocks : [];
// Extract call results from the simulation.
const { calls: block_calls, ...block } = block_results;
const results = block_calls.slice(0, -1) ?? [];
// Extract pre-execution ETH and asset balances.
const ethPre = block_ethPre?.calls ?? [];
const assetsPre = block_assetsPre?.calls ?? [];
const balancesPre = [...ethPre, ...assetsPre].map((call) => call.status === 'success' ? hexToBigInt(call.data) : null);
// Extract post-execution ETH and asset balances.
const ethPost = block_ethPost?.calls ?? [];
const assetsPost = block_assetsPost?.calls ?? [];
const balancesPost = [...ethPost, ...assetsPost].map((call) => call.status === 'success' ? hexToBigInt(call.data) : null);
// Extract asset symbols & decimals.
const decimals = (block_decimals?.calls ?? []).map((x) => x.status === 'success' ? x.result : null);
const symbols = (block_symbols?.calls ?? []).map((x) => x.status === 'success' ? x.result : null);
const tokenURI = (block_tokenURI?.calls ?? []).map((x) => x.status === 'success' ? x.result : null);
const changes = [];
for (const [i, balancePost] of balancesPost.entries()) {
const balancePre = balancesPre[i];
if (typeof balancePost !== 'bigint')
continue;
if (typeof balancePre !== 'bigint')
continue;
const decimals_ = decimals[i - 1];
const symbol_ = symbols[i - 1];
const tokenURI_ = tokenURI[i - 1];
const token = (() => {
if (i === 0)
return {
address: ethAddress,
decimals: 18,
symbol: 'ETH',
};
return {
address: assetAddresses[i - 1],
decimals: tokenURI_ || decimals_ ? Number(decimals_ ?? 1) : undefined,
symbol: symbol_ ?? undefined,
};
})();
if (changes.some((change) => change.token.address === token.address))
continue;
changes.push({
token,
value: {
pre: balancePre,
post: balancePost,
diff: balancePost - balancePre,
},
});
}
return {
assetChanges: changes,
block,
results,
};
}
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