✨ provider.getFeeData (#202)

* Add gas estimation

* Update getFeeData call

package.json

@@ -30,13 +30,13 @@
       "name": "JsonRpcProvider",
       "path": "src/index.ts",
       "import": "{ JsonRpcProvider }",
-      "limit": "20.24kb"
+      "limit": "20.32kb"
     },
     {
       "name": "Contract",
       "path": "src/index.ts",
       "import": "{ Contract }",
-      "limit": "15.87kb"
+      "limit": "15.38kb"
     }
   ],
   "scripts": {

readme.md

@@ -91,6 +91,7 @@
   - [`getBlock`](#getblock)
   - [`getBlockNumber`](#getblocknumber)
   - [`getCode`](#getcode)
+  - [`getFeeData`](#getfeedata)
   - [`getGasPrice`](#getgasprice)
   - [`getLogs`](#getlogs)
   - [`getNetwork`](#getnetwork)
@@ -1195,6 +1196,34 @@ await jsonRpcProvider().getCode(
 
   <br/>
 
+#### [`getFeeData`](https://eeth.dev/docs/api/classes/JsonRpcProvider#getfeedata)
+
+```typescript
+provider.getFeeData(): Promise<FeeData>
+```
+
+  <details>
+  <summary>View Example</summary>
+
+```js
+import { JsonRpcProvider } from 'essential-eth';
+const provider = new JsonRpcProvider('RPC URL HERE' /* Try Infura or POKT */);
+```
+
+```javascript
+await provider.getFeeData();
+// {
+//   gasPrice: { TinyBig: "14184772639" },
+//   lastBaseFeePerGas: { TinyBig: "14038523098" },
+//   maxFeePerGas: { TinyBig: "29577046196" },
+//   maxPriorityFeePerGas: { TinyBig: "1500000000" }
+// }
+```
+
+  </details>
+
+  <br/>
+
 #### [`getGasPrice`](https://eeth.dev/docs/api/classes/JsonRpcProvider#getgasprice)
 
 ```typescript

src/providers/BaseProvider.ts

@@ -9,6 +9,7 @@ import { logger } from '../logger/logger';
 import type { TinyBig } from '../shared/tiny-big/tiny-big';
 import { tinyBig } from '../shared/tiny-big/tiny-big';
 import type { BlockResponse, BlockTag, RPCBlock } from '../types/Block.types';
+import type { FeeData } from '../types/FeeData.types';
 import type { Filter, FilterByBlockHash } from '../types/Filter.types';
 import type { Network } from '../types/Network.types';
 import type {
@@ -455,6 +456,49 @@ export abstract class BaseProvider {
     return tinyBig(hexToDecimal(gasUsed));
   }
 
+  /**
+   * Returns the current recommended FeeData to use in a transaction.
+   * For an EIP-1559 transaction, the maxFeePerGas and maxPriorityFeePerGas should be used.
+   * For legacy transactions and networks which do not support EIP-1559, the gasPrice should be used.Returns an estimate of the amount of gas that would be required to submit transaction to the network.
+   *
+   * * [Identical](/docs/api#isd) to [`ethers.provider.getFeeData`](https://docs.ethers.org/v5/api/providers/provider/#Provider-getFeeData) in ethers.js
+   *
+   * @returns an object with gas estimates for the network currently
+   * @example
+   * ```javascript
+   * await provider.getFeeData();
+   * // {
+   * //   gasPrice: { TinyBig: "14184772639" },
+   * //   lastBaseFeePerGas: { TinyBig: "14038523098" },
+   * //   maxFeePerGas: { TinyBig: "29577046196" },
+   * //   maxPriorityFeePerGas: { TinyBig: "1500000000" }
+   * // }
+   * ```
+   */
+  public async getFeeData(): Promise<FeeData> {
+    const [block, gasPrice] = await Promise.all([
+      this.getBlock('latest'),
+      this.getGasPrice(),
+    ]);
+
+    let lastBaseFeePerGas = null,
+      maxFeePerGas = null,
+      maxPriorityFeePerGas = null;
+
+    if (block && block.baseFeePerGas) {
+      // We may want to compute this more accurately in the future,
+      // using the formula "check if the base fee is correct".
+      // See: https://eips.ethereum.org/EIPS/eip-1559
+      lastBaseFeePerGas = block.baseFeePerGas;
+      maxPriorityFeePerGas = tinyBig('1500000000');
+      maxFeePerGas = tinyBig(
+        block.baseFeePerGas.mul(2).add(maxPriorityFeePerGas),
+      );
+    }
+
+    return { lastBaseFeePerGas, maxFeePerGas, maxPriorityFeePerGas, gasPrice };
+  }
+
   /**
    * Returns transaction receipt event logs that match a specified filter.
    * May return `[]` if parameters are too broad, even if logs exist.

src/providers/test/json-rpc-provider/get-fee-data.test.ts

@@ -0,0 +1,35 @@
+import { StaticJsonRpcProvider } from '@ethersproject/providers';
+import { JsonRpcProvider } from '../../JsonRpcProvider';
+import { rpcUrls } from './../rpc-urls';
+
+const rpcUrl = rpcUrls.mainnet;
+
+const essentialEthProvider = new JsonRpcProvider(rpcUrl);
+const ethersProvider = new StaticJsonRpcProvider(rpcUrl);
+describe('provider.getFeeData', () => {
+  it('should match ethers.js', async () => {
+    const [ethersFeeData, eeFeeData] = await Promise.all([
+      ethersProvider.getFeeData(),
+      essentialEthProvider.getFeeData(),
+    ]);
+    expect(eeFeeData.gasPrice.toString()).toBe(
+      // @ts-ignore
+      ethersFeeData?.gasPrice.toString(),
+    );
+    // @ts-ignore
+    expect(eeFeeData.lastBaseFeePerGas.toString()).toBe(
+      // @ts-ignore
+      ethersFeeData?.lastBaseFeePerGas.toString(),
+    );
+    // @ts-ignore
+    expect(eeFeeData.maxFeePerGas.toString()).toBe(
+      // @ts-ignore
+      ethersFeeData?.maxFeePerGas.toString(),
+    );
+    // @ts-ignore
+    expect(eeFeeData.maxPriorityFeePerGas.toString()).toBe(
+      // @ts-ignore
+      ethersFeeData?.maxPriorityFeePerGas.toString(),
+    );
+  });
+});

src/types/FeeData.types.ts

@@ -0,0 +1,8 @@
+import type { TinyBig } from '../shared/tiny-big/tiny-big';
+
+export interface FeeData {
+  gasPrice: TinyBig;
+  lastBaseFeePerGas: TinyBig | null;
+  maxFeePerGas: TinyBig | null;
+  maxPriorityFeePerGas: TinyBig | null;
+}