feat: add wallet provider foundation

src/wallet/injected.ts

@@ -0,0 +1,39 @@
+import { requestWalletNonce, verifyWalletSignature } from "./api";
+
+export type EthereumProvider = {
+  request: <T = unknown>(args: {
+    method: string;
+    params?: unknown[];
+  }) => Promise<T>;
+};
+
+export function getInjectedEthereum(): EthereumProvider | null {
+  if (typeof window === "undefined") return null;
+  const maybeWindow = window as typeof window & { ethereum?: EthereumProvider };
+  return maybeWindow.ethereum ?? null;
+}
+
+export async function signInWithInjectedWallet(): Promise<{
+  token: string;
+  wallet: string;
+}> {
+  const ethereum = getInjectedEthereum();
+  if (!ethereum) throw new Error("No injected wallet found");
+
+  const accounts = await ethereum.request<string[]>({
+    method: "eth_requestAccounts",
+  });
+  const address = accounts[0];
+  if (!address) throw new Error("No wallet account returned");
+
+  const nonce = await requestWalletNonce(address);
+  const signature = await ethereum.request<string>({
+    method: "personal_sign",
+    params: [nonce.message, address],
+  });
+  return verifyWalletSignature({
+    address,
+    message: nonce.message,
+    signature,
+  });
+}