common: add viem client common functions (#1299)

packages/daimo-common/src/index.ts

@@ -27,3 +27,4 @@ export * from "./chain";
 export * from "./retryBackoff";
 export * from "./cctp";
 export * from "./sendPair";
+export * from "./viemClient";

packages/daimo-common/src/viemClient.ts

@@ -0,0 +1,64 @@
+import { extractChain, Chain } from "viem";
+import {
+  mainnet,
+  sepolia,
+  base,
+  optimism,
+  polygon,
+  baseSepolia,
+  arbitrum,
+  arbitrumSepolia,
+  optimismSepolia,
+  avalanche,
+  avalancheFuji,
+} from "viem/chains";
+
+/** Retrieve the Viem chain config for a given chainId. */
+export function getViemChainById(chainId: number): Chain {
+  if (!supportedChainIds.includes(chainId))
+    throw new Error(`Unsupported chainId ${chainId}`);
+
+  return extractChain({
+    chains: [
+      mainnet,
+      sepolia,
+      polygon,
+      arbitrum,
+      arbitrumSepolia,
+      base,
+      baseSepolia,
+      optimism,
+      optimismSepolia,
+      avalanche,
+      avalancheFuji,
+    ],
+    id: chainId as any,
+  });
+}
+
+/** Get the RPC URL for a given chainId. */
+export function getAlchemyTransportUrl(chainId: number, alchemyApiKey: string) {
+  const network = alchemyChainNames[chainId];
+  if (!network) {
+    throw new Error(`Invalid chainId: ${chainId}`);
+  }
+  const alchemyRpcUrl = `https://${network}.g.alchemy.com/v2/${alchemyApiKey}`;
+  return alchemyRpcUrl;
+}
+
+/**
+ * Mapping of chainID to Alchemy network name for RPC URLs.
+ * Note: Avax is not supported by Alchemy, nor do we support it.
+ */
+const alchemyChainNames: Record<number, string> = {
+  [mainnet.id]: "eth-mainnet",
+  [sepolia.id]: "eth-sepolia",
+  [polygon.id]: "polygon-mainnet",
+  [arbitrum.id]: "arb-mainnet",
+  [arbitrumSepolia.id]: "arb-sepolia",
+  [base.id]: "base-mainnet",
+  [baseSepolia.id]: "base-sepolia",
+  [optimism.id]: "opt-mainnet",
+  [optimismSepolia.id]: "opt-sepolia",
+};
+const supportedChainIds = Object.keys(alchemyChainNames).map(Number);