fix(auth): migrate from next-auth to better-auth (#1453)

lib/auth.ts

@@ -0,0 +1,58 @@
+import { compare, genSaltSync, hashSync } from "bcrypt-ts";
+import { betterAuth } from "better-auth";
+import { drizzleAdapter } from "better-auth/adapters/drizzle";
+import { nextCookies } from "better-auth/next-js";
+import { anonymous } from "better-auth/plugins";
+import { drizzle } from "drizzle-orm/postgres-js";
+import { headers } from "next/headers";
+import postgres from "postgres";
+import { account, session, user, verification } from "./db/schema";
+
+// biome-ignore lint: Forbidden non-null assertion.
+const client = postgres(process.env.POSTGRES_URL!);
+const db = drizzle(client);
+
+export const auth = betterAuth({
+  basePath: "/api/auth",
+  baseURL: process.env.BETTER_AUTH_URL,
+  database: drizzleAdapter(db, {
+    provider: "pg",
+    schema: { user, session, account, verification },
+  }),
+  emailAndPassword: {
+    enabled: true,
+    password: {
+      hash: async (password) => hashSync(password, genSaltSync(10)),
+      verify: async ({ hash, password }) => compare(password, hash),
+    },
+  },
+  ...(process.env.VERCEL_CLIENT_ID && process.env.VERCEL_CLIENT_SECRET
+    ? {
+        socialProviders: {
+          vercel: {
+            clientId: process.env.VERCEL_CLIENT_ID,
+            clientSecret: process.env.VERCEL_CLIENT_SECRET,
+          },
+        },
+      }
+    : {}),
+  advanced: {
+    database: {
+      generateId: () => crypto.randomUUID(),
+    },
+  },
+  plugins: [anonymous(), nextCookies()],
+});
+
+export type UserType = "guest" | "regular";
+
+export function getUserType(user: Record<string, unknown>): UserType {
+  return (user as { isAnonymous?: boolean }).isAnonymous ? "guest" : "regular";
+}
+
+export async function getSession() {
+  return auth.api.getSession({ headers: await headers() });
+}
+
+export type AuthSession = Awaited<ReturnType<typeof getSession>>;
+export type AuthUser = NonNullable<AuthSession>["user"];