Yes, use api for it

nestjs as a api

and communicate using fetch requests

problem is my signIn callback is working fine returning jwt and refresh token from backend, but I cannot connect it to jwt callback, jwt callback is taking googleProvider jwt token... credentials provider works fine, and I'm using refresh token strategy on my backend

can I know in which function are you getting an error?

from async jwt function in callback, token.backendTokens.expiresIn this variable, it is saying that is undefined...
my sign in function returns { user, backendTokens } which is holding user and tokens from backend, but it doesn't seem to be passed in jwt()

If it is undefined, have you used console.log in the backend before sending the request to check it? and have you made sure expiresIn is in string?

yes everything works fine

await callback(user, account, profile);
this function is returning everything from backend normally how it should be

it returns this object example:

 {
  user: {
    id: 'clqzxn1lw0000n3hm2arqby0g',
    firstName: 'hello',
    lastName: 'hello',
    password: '',
    email: 'hello@gmail.com',
    emailVerified: null,
    phone: null,
    image: 'hehe'
  },
  backendTokens: {
    accessToken: 'eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9.eyJpYXQiOjE3MDQ0NDkzNTgsImV4cCI6MTcwNDQ0OTM3OH0.AK4vrzEuND9OsruMiOWME6qNCkFjmYvaa-IwPNHelJ0',
    refreshToken: 'eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9.eyJpYXQiOjE3MDQ0NDkzNTgsImV4cCI6MTcwNTA1NDE1OH0.u82pfwGacZBCTYYV657S8DkoAb80LC-zwxeAjZv7ZGI',
    expiresIn: 1704449378239
  }
}

on frontend, try printing the raw response.

if (!token.backendTokens?.expiresIn || new Date().getTime() < token.backendTokens?.expiresIn) return token;

maybe try this, since the backendTokens only available after the refreshToken function?

is there any good next auth tutorials that include oauth and custom backend?

what does the endpoint of /auth/login return?

https://www.youtube.com/watch?v=cDWytA0V2kI
this maybe

I tried to modify callback removed sign in function, only left jwt function, on first login when I click on login with google, token gets stored in cookies and it persists user as logged, but backendUser from backend call gets deleted in the process and user and account fields get undefined

async jwt({ token, user, account, profile }: any) {
            console.log('user', user);
            console.log('account', account);
            if (account?.provider === 'credentials') {
                console.log('user from credentials:', user);
                if (user) return { ...token, ...user };
                if (new Date().getTime() < token.backendTokens.expiresIn) return token;
            } else {
                const backendUser = await callback(user, account, profile);
                console.log('user from oauth:', backendUser);
                if (backendUser)
                    return { token: { ...backendUser.backendTokens }, user: { ...backendUser.user } };

                if (new Date().getTime() < backendUser.backendTokens.expiresIn) return token;
            }

            return await refreshToken(token);
        },

I don't know is it just me but it's really hard to make a good authentication and I always had problems, can't find a really good solution anywhere

that's a really good solution but not for oauth

the jwt callback should return the token object

if you can return the refreshToken from this endpoint /auth/login, then the refreshToken will be avaliable in the token object on jwt callback

async authorize(credentials, req) {
    if (!credentials?.email || !credentials?.password) return null;
    const { email, password } = credentials;
    const res = await fetch(process.env.NEXT_PUBLIC_BACKEND_API + '/auth/login', {
        method: 'POST',
        body: JSON.stringify({
            email: email,
            password
        }),
        headers: {
            'Content-Type': 'application/json'
        }
    });
    if (res.status == 401) {
        console.log(res.statusText);

        return null;
    }
    const user = await res.json();
    const tokens = await fetchToken(user);
    return {...user, ...tokens};
}

like this

credentials provider work fine with this code, it persist user and data is fetched normally, problem is GoogleAuth

async jwt({ token, user, account }: any) {
        if (account['provider'] === 'google') return token;
    if (user) return { ...token, ...user };

    if (new Date().getTime() < token.backendTokens.expiresIn) return token;

    return await refreshToken(token);
},

how about this?

it would work but it's not connected with my backend, when user logs in with google I want to save user on my backend, and persist user from my backend if you get me

what error you get with google auth?

thanks brother, I'll take a look