feat: add getGasPrice rpc provider method (starknet-io#1056)

* feat: add getGasPrice rpc provider method

* fix: rpc method name and test function

* fix: change rpc provide method helper
- change the helper method of `getL1GasPrice()` from `getBlockWithTxs()` to `getBlockWithTxHashes()`

* fix: change test name to getL1GasPrice

__tests__/rpcProvider.test.ts

@@ -73,6 +73,11 @@ describeIfRpc('RPCProvider', () => {
     expect(typeof blockNumber).toBe('number');
   });
 
+  test('getL1GasPrice', async () => {
+    const gasPrice = await rpcProvider.getL1GasPrice('latest');
+    expect(typeof gasPrice).toBe('string');
+  });
+
   test('getStateUpdate', async () => {
     const stateUpdate = await rpcProvider.getBlockStateUpdate('latest');
     expect(stateUpdate).toMatchSchemaRef('StateUpdateResponse');

src/provider/interface.ts

@@ -78,6 +78,14 @@ export abstract class ProviderInterface {
     blockIdentifier?: BlockIdentifier
   ): Promise<ContractClassResponse>;
 
+  /**
+   * Gets the price of l1 gas in the block
+   *
+   * @param blockIdentifier block identifier
+   * @returns gas price of the block
+   */
+  public abstract getL1GasPrice(blockIdentifier: BlockIdentifier): Promise<string>;
+
   /**
    * Returns the contract class hash in the given block for the contract deployed at the given address
    *

src/provider/rpc.ts

@@ -100,6 +100,12 @@ export class RpcProvider implements ProviderInterface {
     return this.channel.getBlockWithTxs(blockIdentifier);
   }
 
+  public async getL1GasPrice(blockIdentifier?: BlockIdentifier) {
+    return this.channel
+      .getBlockWithTxHashes(blockIdentifier)
+      .then(this.responseParser.parseL1GasPriceResponse);
+  }
+
   public async getBlockWithReceipts(blockIdentifier?: BlockIdentifier) {
     if (this.channel instanceof RPC06.RpcChannel)
       throw new LibraryError('Unsupported method for RPC version');

src/utils/responseParser/rpc.ts

@@ -20,6 +20,8 @@ import { toBigInt } from '../num';
 import { isString } from '../shortString';
 import { estimateFeeToBounds, estimatedFeeToMaxFee } from '../stark';
 import { ResponseParser } from '.';
+import { isString } from '../shortString';
+
 
 export class RPCResponseParser
   implements
@@ -121,4 +123,8 @@ export class RPCResponseParser
       abi: isString(res.abi) ? JSON.parse(res.abi) : res.abi,
     };
   }
+
+  public parseL1GasPriceResponse(res: BlockWithTxHashes): string {
+    return res.l1_gas_price.price_in_wei;
+  }
 }