Create T3 App (Next JS) + App Router で Google ログインを設定する

import {
  getServerSession,
  type DefaultSession,
  type NextAuthOptions,
  type Account,
} from "next-auth";
import { type JWT } from "next-auth/jwt";
import GoogleProvider from "next-auth/providers/google";

import { env } from "~/env.mjs";

/**
 * Module augmentation for `next-auth` types. Allows us to add custom properties to the `session`
 * object and keep type safety.
 *
 * @see https://next-auth.js.org/getting-started/typescript#module-augmentation
 */
declare module "next-auth" {
  interface Session extends DefaultSession {
    user: {
      id: string;
      // ...other properties
      // role: UserRole;
    } & DefaultSession["user"];
    accessToken?: string;
    accessTokenExpires?: string;
    refreshToken?: string;
    idToken?: string;
    error?: string;
  }
}

const GOOGLE_AUTHORIZATION_URL =
  "https://accounts.google.com/o/oauth2/v2/auth?" +
  new URLSearchParams({
    prompt: "consent",
    access_type: "offline",
    response_type: "code",
  }).toString();

/**
 * Takes a token, and returns a new token with updated
 * `accessToken` and `accessTokenExpires`. If an error occurs,
 * returns the old token and an error property
 */
async function refreshToken(token: JWT): Promise<JWT> {
  try {
    const url =
      "https://oauth2.googleapis.com/token?" +
      new URLSearchParams({
        client_id: process.env.GOOGLE_CLIENT_ID ?? "",
        client_secret: process.env.GOOGLE_CLIENT_SECRET ?? "",
        grant_type: "refresh_token",
        refresh_token: (token.refreshToken ?? "") as string,
      }).toString();

    const response = await fetch(url, {
      headers: {
        "Content-Type": "application/x-www-form-urlencoded",
      },
      method: "POST",
    });

    const refreshedTokens = await response.json() as Account;

    if (!response.ok) {
      throw refreshedTokens;
    }

    return {
      ...token,
      accessToken: refreshedTokens.access_token,
      accessTokenExpires: Date.now() + (refreshedTokens.expires_in as number) * 1000,
      refreshToken: refreshedTokens.refresh_token ?? token.refreshToken, // Fall back to old refresh token
    };
  } catch (error) {
    console.error(error);

    return {
      ...token,
      error: "RefreshAccessTokenError",
    };
  }
}


/**
 * Options for NextAuth.js used to configure adapters, providers, callbacks, etc.
 *
 * @see https://next-auth.js.org/configuration/options
 */
export const authOptions: NextAuthOptions = {
  callbacks: {
    jwt: ({ token, user, account }) => {
        if (account && user) {
          return {
            accessToken: account.access_token,
            accessTokenExpires: Date.now() + (account.expires_in as number) * 1000,
            refreshToken: account.refresh_token,
            idToken: account.id_token,
            user,
          }
        }

        // Return previous token if the access token has not expired yet
        if (Date.now() < (token.accessTokenExpires as number)) {
          return token
        }

        // Access token has expired, try to update it
        return refreshToken(token);
    },
    session: ({ session, token }) => ({
      ...session,
      user: {
        ...session.user,
        id: token.sub,
      },
      idToken: token.idToken,
    }),
  },
  providers: [
    GoogleProvider({
      clientId: env.GOOGLE_CLIENT_ID,
      clientSecret: env.GOOGLE_CLIENT_SECRET,
      authorization: GOOGLE_AUTHORIZATION_URL,
    }),
    /**
     * ...add more providers here.
     *
     * Most other providers require a bit more work than the Discord provider. For example, the
     * GitHub provider requires you to add the `refresh_token_expires_in` field to the Account
     * model. Refer to the NextAuth.js docs for the provider you want to use. Example:
     *
     * @see https://next-auth.js.org/providers/github
     */
  ],
  secret: process.env.NEXTAUTH_SECRET,
};

/**
 * Wrapper for `getServerSession` so that you don't need to import the `authOptions` in every file.
 *
 * @see https://next-auth.js.org/configuration/nextjs
 */
export const getServerAuthSession = () => getServerSession(authOptions);