From afb8e18efa8e0cb15b29ed53cbda0f94bc092bd8 Mon Sep 17 00:00:00 2001
From: Cho Young-Hwi <cyh76507707@gmail.com>
Date: Sat, 14 Mar 2026 13:16:43 +0000
Subject: [PATCH] [#205] Add shared RPC client with chain selection and
 fallback transport

- Create lib/rpc.ts: public client using NEXT_PUBLIC_CHAIN_ID to select
  Base or Base Sepolia, with fallback from NEXT_PUBLIC_RPC_URL to default RPC
- Update lib/viem.ts to re-export from lib/rpc.ts for backward compatibility
- Aligned with wagmi config (same env vars, same chain selection logic)

Fixes #205

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
---
 lib/rpc.ts  | 22 ++++++++++++++++++++++
 lib/viem.ts | 15 +++------------
 2 files changed, 25 insertions(+), 12 deletions(-)
 create mode 100644 lib/rpc.ts

diff --git a/lib/rpc.ts b/lib/rpc.ts
new file mode 100644
index 00000000..df6a9d5a
--- /dev/null
+++ b/lib/rpc.ts
@@ -0,0 +1,22 @@
+import { createPublicClient, http, fallback } from "viem";
+import { base, baseSepolia } from "viem/chains";
+
+const chainId = Number(process.env.NEXT_PUBLIC_CHAIN_ID || "84532");
+const chain = chainId === 8453 ? base : baseSepolia;
+
+const customRpc = process.env.NEXT_PUBLIC_RPC_URL;
+
+const transport = customRpc
+  ? fallback([http(customRpc), http()])
+  : http();
+
+/**
+ * Shared public client for reading from Base (or Base Sepolia).
+ *
+ * Chain is selected via NEXT_PUBLIC_CHAIN_ID (default: 84532 / Base Sepolia).
+ * Uses NEXT_PUBLIC_RPC_URL with a fallback to the chain's default public RPC.
+ */
+export const publicClient = createPublicClient({
+  chain,
+  transport,
+});
diff --git a/lib/viem.ts b/lib/viem.ts
index cfb41c1c..9fca585f 100644
--- a/lib/viem.ts
+++ b/lib/viem.ts
@@ -1,12 +1,3 @@
-import { createPublicClient, http } from "viem";
-import { base } from "viem/chains";
-
-/**
- * Public client for reading from Base.
- *
- * Uses the default Base RPC. Override via BASE_RPC_URL env var.
- */
-export const publicClient = createPublicClient({
-  chain: base,
-  transport: http(process.env.BASE_RPC_URL || undefined),
-});
+// Re-export from lib/rpc.ts — this file exists for backward compatibility.
+// New code should import from "lib/rpc" directly.
+export { publicClient } from "./rpc";