# 🌍 Transaction Simulator

Transaction Simulator integrates seamlessly with Tatum SDK to provide transaction simulation capabilities for EVM-based blockchains.

## 📖 Description

The Transaction Simulator is designed to bolster the efficiency and security of blockchain transactions. It offers crucial capabilities such as:

- Simulating native currency transfers.
- Simulating ERC20 token transfers.

By leveraging these simulations, developers can:

1. **Estimate Fees Accurately:** One of the primary challenges in sending blockchain transactions is determining an optimal gas fee that ensures quick confirmation without overpaying. By simulating a transaction before sending it, developers can get a precise estimate of the gas fee, saving costs and improving user experience.

2. **Enhance Safety:** Simulating transactions allows developers to anticipate and catch potential errors or vulnerabilities in transaction logic. By identifying these issues in a simulated call, developers can prevent costly mistakes when deploying actual transactions.

3. **Optimize Transaction Parameters:** Beyond just estimating fees, simulating transactions can help developers fine-tune other parameters, such as gas limit, to optimize transaction performance.

It is built upon popular packages like `ethers`, ensuring a robust, reliable, and secure foundation for all simulation activities.

## 🚀 Quick Start

1. **Installation**

   Firstly, ensure that the `@tatumio/transaction-simulator` package is set as a dependency within your project. Next, import the Transaction Simulator extension:

   ```typescript
   import { TransactionSimulator } from '@tatumio/transaction-simulator';
   ```

2. **Initialization**

   Create an instance of Tatum SDK passing `TransactionSimulator` as one of extensions.

   ```typescript
   const tatumSdk = await TatumSDK.init<Ethereum>({
        network: Network.ETHEREUM,
        configureExtensions: [
            TransactionSimulator,
        ]
    })
   ```

## 🛠️ How to Use

The Transaction Simulator provides methods to simulate native and ERC20 token transfers on EVM-based blockchains. Below is a guide on how to utilize these functionalities:

### Native Transfers:

1. **Define Your Payload**:
   Begin by creating a `Transfer` object. This object will encapsulate all the required parameters for your native transaction.

    ```typescript
    const transferPayload: Transfer = {
      to: '0x0Ae9E7437092BB7E7Bd6Eccf0eF1ad05591f5B47',
      from: '0xDce92f40cAdDE2C4e3EA78b8892c540e6bFe2f81',
      gas: '0x5208', // optional
      gasPrice: '0x4BA1C7B8C', //optional
      value: 1000, // example amount to send in wei
    };
    ```

2. **Call `simulateTransfer`**:
   Pass the defined payload to the `simulateTransfer` method.

    ```typescript
    const simulationResult = await tatumSdk.extension(TransactionSimulator).simulateTransfer(transferPayload);
    ```

   This method simulates the transaction, estimates the fees, and returns the expected result of the transaction.

3. **Check simulation results**:

   ```json
   {
     "transactionDetails": {
       "from": "0xDce92f40cAdDE2C4e3EA78b8892c540e6bFe2f81",
       "to": "0x0Ae9E7437092BB7E7Bd6Eccf0eF1ad05591f5B47",
       "value": 10000,
       "gasLimit": 21000,
       "gasPrice": 20302297996
     },
     "status": "success",
     "balanceChanges": {
       "0xDce92f40cAdDE2C4e3EA78b8892c540e6bFe2f81": {
         "from": 243323659206289750000,
         "to": 243323232858031850000
       },
       "0x0Ae9E7437092BB7E7Bd6Eccf0eF1ad05591f5B47": {
         "from": 8951104779026672,
         "to": 8951104779036672
       }
     }
   }
   ```

### ERC20 Token Transfers:

1. **Define Your Token Transfer Payload**:
   To simulate an ERC20 token transfer, you will use the `TokenTransfer` object.

    ```typescript
    const tokenTransferPayload: TokenTransfer = {
      to: 'recipient_address',
      from: 'sender_address',
      gas: '0xB411', // optional
      gasPrice: '0x4B16C370A', //optional
      value: 500, // example token amount to send
      tokenContractAddress: 'your_erc20_token_contract_address'
    };
    ```

2. **Call `simulateTransferErc20`**:
   With your `TokenTransfer` payload ready, pass it to the `simulateTransferErc20` method.

    ```typescript
    const tokenSimulationResult = await tatumSdk.extension(TransactionSimulator).simulateTransferErc20(tokenTransferPayload);
    ```

   This method fetches token details, simulates the transaction, and returns an estimation of the transaction's outcome along with the necessary gas fees.

3. **Check simulation results**:

   ```json
   {
     "transactionDetails": {
       "from": "0xDce92f40cAdDE2C4e3EA78b8892c540e6bFe2f81",
       "to": "0xaf758da9f7bdaa7590175193388e9c99427cc2d2",
       "tokenContractAddress": "0xdac17f958d2ee523a2206206994597c13d831ec7",
       "data": "0xa9059cbb000000000000000000000000af758da9f7bdaa7590175193388e9c99427cc2d2000000000000000000000000000000000000000000000000000000001908b100",
       "gasLimit": 46097,
       "gasPrice": 20156528394
     },
     "status": "success",
     "balanceChanges": {
       "0xDce92f40cAdDE2C4e3EA78b8892c540e6bFe2f81": {
         "from": 243656557299636170000,
         "to": 243655628144146780000
       }
     },
     "tokenTransfers": {
       "0xdac17f958d2ee523a2206206994597c13d831ec7": {
         "name": "TetherUSD",
         "symbol": "USDT",
         "decimals": 6,
         "0xDce92f40cAdDE2C4e3EA78b8892c540e6bFe2f81": {
           "from": 2387468.080258,
           "to": 2387048.080258
         },
         "0xaf758da9f7bdaa7590175193388e9c99427cc2d2": {
           "from": 422.304,
           "to": 842.304
         }
       }
     }
   }
   ```

By using the above methods, you can efficiently predict the behavior and costs of your transactions before actually broadcasting them, ensuring optimized and error-free transactions.

### Gas Price Estimation:

   - Methods accept `gasPrice` as a parameter. If you don't provide it, the gas price will be estimated using the `eth_gasPrice` method.
   - Methods accept `gas` as a parameter. If you don't provide it, the gas limit will be estimated using the `eth_estimateGas` method.


## 🔗🔗 Supported Networks

```typescript
Network.ARBITRUM_ONE,
Network.AVALANCHE_C,
Network.CELO,
Network.CELO_ALFAJORES,
Network.CHILIZ,
Network.ETHEREUM,
Network.ETHEREUM_SEPOLIA,
Network.ETHEREUM_GOERLI,
Network.ETHEREUM_HOLESKY,
Network.ETHEREUM_CLASSIC,
Network.POLYGON,
Network.POLYGON_MUMBAI,
Network.BINANCE_SMART_CHAIN,
Network.BINANCE_SMART_CHAIN_TESTNET,
Network.OPTIMISM,
Network.OPTIMISM_TESTNET
```