eth-json-rpc-middleware

import { JsonRpcEngine } from 'json-rpc-engine'; import { createFetchMiddleware, createBlockRefMiddleware, createChainIdMiddleware } from 'eth-json-rpc-middleware'; // Mock RPC service for createFetchMiddleware (required since v18.0.0) const mockRpcService = { provider: { request: async ({ method, params }) => { console.log(`Mock RPC request: ${method} ${JSON.stringify(params)}`); // In a real application, this would forward to an actual RPC endpoint // using a provider from @metamask/network-controller or similar. if (method === 'eth_chainId') return '0x1'; // Mainnet if (method === 'eth_blockNumber') return '0x' + (123456789).toString(16); if (method === 'eth_sendRawTransaction') return '0xmockTxHash'; return null; // Handle other methods as needed }, }, // Other properties like 'currentChainId' might be expected by some versions/integrations }; async function setupAndUseRpcEngine() { const engine = new JsonRpcEngine(); // Add middleware engine.add(createBlockRefMiddleware()); engine.add(createChainIdMiddleware('0x1')); // Example: force chainId to Ethereum Mainnet engine.add(createFetchMiddleware({ rpcService: mockRpcService })); // Example request try { const response = await engine.handle({ id: 1, jsonrpc: '2.0', method: 'eth_blockNumber' }); console.log('eth_blockNumber response:', response.result); const chainIdResponse = await engine.handle({ id: 2, jsonrpc: '2.0', method: 'eth_chainId' }); console.log('eth_chainId response:', chainIdResponse.result); // Example of a request that might pass through the fetch middleware const sendTxResponse = await engine.handle({ id: 3, jsonrpc: '2.0', method: 'eth_sendRawTransaction', params: ['0xmockrawtransactiondata'], }); console.log('eth_sendRawTransaction response:', sendTxResponse.result); } catch (error) { console.error('RPC Error:', error); } } setupAndUseRpcEngine();