​
Next Auth

Cascade is based on T3 app meaning that it uses NextAuth.js under the hood. Docs are here.
This documentation is a brief overview of what is put on top of NextAuth.js to make it work with Cascade. We will focus on interesting parts! We extend the Session object with some additional types to make it work with Cascade. We need to add role and planId to the user object. 

declare module "next-auth" {
  interface Session extends DefaultSession {
    user: {
      id: string;
      planId: string | null;
      role: Role;
    } & DefaultSession["user"];
  }
In callbacks we need to fetch the user from the database and add the role and planId to the session object. This is done to make sure that whenever you are working with Session from NextAuth.js you have all the necessary information about the user. 
  callbacks: {
    session: async ({ session, user }) => {
      const dbUser = await db.user.findUnique({
        where: {
          id: user.id,
        },
      });
      return {
        ...session,
        user: {
          ...session.user,
          id: user.id,
          planId: dbUser?.planId ?? null,
          role: dbUser?.role,
        },
      };
    },
  },

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External services

This section mentions something about Emails
This section mentions something about Error Tracking
This section mentions something about Background jobs
Next Auth is a great entrypoint for other services we need to use for our SaaS. For example, here we use events to manage the following:
  • Sentry - to connect user to the Sentry error tracking, so we could easily debug it.
  • Trigger.dev - to trigger a background job to send a notification when a new user signs up
  • Loops - to send a welcome email to the new users.
  events: {
    async signIn({ user, isNewUser }) {
      Sentry.setUser({ id: user.id, name: user.name, email: user.email ?? "" });
      if (isNewUser) {
        if (isTriggerEnabled) {
          await slackNewUserNotification.invoke({
            user: {
              name: user.name ?? "unknown",
              email: user.email ?? undefined,
              id: user.id,
            },
          });
        }
        if (loops && user.email) {
          await loops.sendEvent(
            {
              email: user.email,
            },
            "cascade_sign_up",
            {
              ...(user.name && { name: user.name }),
              email: user.email,
            },
          );
        }
      }
    },
    signOut() {
      Sentry.setUser(null);
    },
  },

​
Providers

Cascade comes with Discord & Google providers out of the box. You can easily add more providers by following the NextAuth.js documentation. 
providers: [
    DiscordProvider({
      clientId: env.DISCORD_CLIENT_ID!,
      clientSecret: env.DISCORD_CLIENT_SECRET!,
    }),
    GoogleProvider({
      clientId: env.GOOGLE_CLIENT_ID!,
      clientSecret: env.GOOGLE_CLIENT_SECRET!,
    }),

    /**
     * ...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
     */
  ],