feat: enable fallback rpc provider

packages/arb-token-bridge-ui/src/util/rpc/alchemy.ts

@@ -0,0 +1,37 @@
+import { ChainId } from '../networks'
+
+export function getAlchemyRpcUrl(chainId: ChainId): string | null {
+  const alchemyKey = process.env.NEXT_PUBLIC_ALCHEMY_KEY!
+
+  switch (chainId) {
+    // L1 Mainnet
+    case ChainId.Ethereum:
+      return `https://eth-mainnet.g.alchemy.com/v2/${alchemyKey}`
+
+    // L1 Testnet
+    case ChainId.Sepolia:
+      return `https://eth-sepolia.g.alchemy.com/v2/${alchemyKey}`
+    case ChainId.Holesky:
+      return `https://eth-holesky.g.alchemy.com/v2/${alchemyKey}`
+
+    // L2 Mainnet
+    case ChainId.ArbitrumOne:
+      return `https://arb-mainnet.g.alchemy.com/v2/${alchemyKey}`
+    case ChainId.ArbitrumNova:
+      return null
+    case ChainId.Base:
+      return `https://base-mainnet.g.alchemy.com/v2/${alchemyKey}`
+
+    // L2 Testnet
+    case ChainId.ArbitrumSepolia:
+      return `https://arb-sepolia.g.alchemy.com/v2/${alchemyKey}`
+    case ChainId.BaseSepolia:
+      return `https://base-sepolia.g.alchemy.com/v2/${alchemyKey}`
+
+    // Local
+    case ChainId.Local:
+    case ChainId.ArbitrumLocal:
+    case ChainId.L3Local:
+      return null
+  }
+}

packages/arb-token-bridge-ui/src/util/rpc/getRpcUrl.ts

@@ -0,0 +1,22 @@
+import { ChainId } from '../networks'
+
+import { getInfuraRpcUrl } from './infura'
+import { getAlchemyRpcUrl } from './alchemy'
+
+type RpcProvider = 'infura' | 'alchemy'
+
+function getRpcProvider(): RpcProvider {
+  const rpcProviderFromEnv = process.env.NEXT_PUBLIC_RPC_PROVIDER
+  return (rpcProviderFromEnv?.toLowerCase() as RpcProvider) || 'infura' // the || is intentional to handle empty strings
+}
+
+export function getRpcUrl(chainId: ChainId): string | null {
+  const rpcProvider = getRpcProvider()
+
+  switch (rpcProvider) {
+    case 'infura':
+      return getInfuraRpcUrl(chainId)
+    case 'alchemy':
+      return getAlchemyRpcUrl(chainId)
+  }
+}

packages/arb-token-bridge-ui/src/util/rpc/infura.ts

@@ -0,0 +1,57 @@
+import { ChainId } from '../networks'
+
+export function getInfuraKey(chainId: ChainId) {
+  const defaultInfuraKey = process.env.NEXT_PUBLIC_INFURA_KEY
+
+  switch (chainId) {
+    case ChainId.Ethereum:
+      return process.env.NEXT_PUBLIC_INFURA_KEY_ETHEREUM || defaultInfuraKey
+    case ChainId.Sepolia:
+      return process.env.NEXT_PUBLIC_INFURA_KEY_SEPOLIA || defaultInfuraKey
+    case ChainId.ArbitrumOne:
+      return process.env.NEXT_PUBLIC_INFURA_KEY_ARBITRUM_ONE || defaultInfuraKey
+    case ChainId.Base:
+      return process.env.NEXT_PUBLIC_INFURA_KEY_BASE || defaultInfuraKey
+    case ChainId.ArbitrumSepolia:
+      return (
+        process.env.NEXT_PUBLIC_INFURA_KEY_ARBITRUM_SEPOLIA || defaultInfuraKey
+      )
+    case ChainId.BaseSepolia:
+      return process.env.NEXT_PUBLIC_INFURA_KEY_BASE_SEPOLIA || defaultInfuraKey
+
+    default:
+      return defaultInfuraKey
+  }
+}
+
+export function getInfuraRpcUrl(chainId: ChainId): string | null {
+  const infuraKey = getInfuraKey(chainId)
+
+  switch (chainId) {
+    // L1 Mainnet
+    case ChainId.Ethereum:
+      return `https://mainnet.infura.io/v3/${infuraKey}`
+    // L1 Testnet
+    case ChainId.Sepolia:
+      return `https://sepolia.infura.io/v3/${infuraKey}`
+    case ChainId.Holesky:
+      return null
+    // L2 Mainnet
+    case ChainId.ArbitrumNova:
+      return null
+    case ChainId.ArbitrumOne:
+      return `https://arbitrum-mainnet.infura.io/v3/${infuraKey}`
+    case ChainId.Base:
+      // L2 Testnet
+      return `https://base-mainnet.infura.io/v3/${infuraKey}`
+    case ChainId.ArbitrumSepolia:
+      return `https://arbitrum-sepolia.infura.io/v3/${infuraKey}`
+    case ChainId.BaseSepolia:
+      return `https://base-sepolia.infura.io/v3/${infuraKey}`
+    // Local
+    case ChainId.Local:
+    case ChainId.ArbitrumLocal:
+    case ChainId.L3Local:
+      return null
+  }
+}