LMS (learning platform) on Next.js 16 (App Router), MySQL 8 and Better Auth

import { drizzle } from "drizzle-orm/mysql2";
import mysql from "mysql2/promise";

// ponytail: single module-level pool; the runtime + mysql2's pool handle concurrency,
// so no globalThis singleton dance needed.
const pool = mysql.createPool(process.env.DATABASE_URL!);

export const db = drizzle({ client: pool });

import { boolean, mysqlTable, text, timestamp, varchar } from "drizzle-orm/mysql-core";

export const user = mysqlTable("user", {
  id: varchar("id", { length: 255 }).primaryKey(),
  name: text("name").notNull(),
  email: varchar("email", { length: 255 }).notNull().unique(),
  emailVerified: boolean("email_verified").notNull().default(false),
  image: text("image"),
  createdAt: timestamp("created_at").notNull().defaultNow(),
  updatedAt: timestamp("updated_at").notNull().defaultNow(),
});

export const session = mysqlTable("session", {
  id: varchar("id", { length: 255 }).primaryKey(),
  expiresAt: timestamp("expires_at").notNull(),
  token: varchar("token", { length: 255 }).notNull().unique(),
  createdAt: timestamp("created_at").notNull().defaultNow(),
  updatedAt: timestamp("updated_at").notNull(),
  ipAddress: text("ip_address"),
  userAgent: text("user_agent"),
  userId: varchar("user_id", { length: 255 })
    .notNull()
    .references(() => user.id, { onDelete: "cascade" }),
});

export const account = mysqlTable("account", {
  id: varchar("id", { length: 255 }).primaryKey(),
  accountId: text("account_id").notNull(),
  providerId: text("provider_id").notNull(),
  userId: varchar("user_id", { length: 255 })
    .notNull()
    .references(() => user.id, { onDelete: "cascade" }),
  accessToken: text("access_token"),
  refreshToken: text("refresh_token"),
  idToken: text("id_token"),
  accessTokenExpiresAt: timestamp("access_token_expires_at"),
  refreshTokenExpiresAt: timestamp("refresh_token_expires_at"),
  scope: text("scope"),
  password: text("password"),
  createdAt: timestamp("created_at").notNull().defaultNow(),
  updatedAt: timestamp("updated_at").notNull(),
});

export const verification = mysqlTable("verification", {
  id: varchar("id", { length: 255 }).primaryKey(),
  identifier: text("identifier").notNull(),
  value: text("value").notNull(),
  expiresAt: timestamp("expires_at").notNull(),
  createdAt: timestamp("created_at").notNull().defaultNow(),
  updatedAt: timestamp("updated_at").notNull().defaultNow(),
});

// Better Auth instance (self-hosted, Next.js 16 (App Router)).
import { betterAuth } from "better-auth";
import { drizzleAdapter } from "better-auth/adapters/drizzle";
// Reuse the SAME postgres-js/Drizzle client the db slice exported in
// src/lib/db.ts — Better Auth shares the pooled `DATABASE_URL` connection.
import { db } from "./db";
import * as authSchema from "@/db/auth-schema";

export const auth = betterAuth({
  // Drizzle adapter over the shared client. The schema is passed HERE (not into
  // drizzle()) — it is the only consumer that needs it, so the db client stays
  // schema-less. ponytail: do NOT enable experimental.joins; it is the one option
  // that would make the adapter reach into db._.fullSchema.
  // ponytail: usePlural stays false (the default) — with it true Better Auth would
  // look for `sessions`/`accounts` and could bind to the analytics/ledger app-type tables.
  database: drizzleAdapter(db, { provider: "mysql", schema: authSchema }),
  // ponytail: email+password is the shortest real auth that works out of
  // the box — add socialProviders / plugins here when the app needs them.
  emailAndPassword: { enabled: true },
  secret: process.env.BETTER_AUTH_SECRET,
  baseURL: process.env.BETTER_AUTH_URL,
});

export type Session = typeof auth.$Infer.Session;

// Mount Better Auth on Next's route layer.
import { toNextJsHandler } from "better-auth/next-js";
import { auth } from "@/lib/auth";

export const { GET, POST } = toNextJsHandler(auth);

// Session-protection proxy for Next.js 16 (App Router) (Next 16 renamed middleware.ts → proxy.ts).
// ponytail: getSessionCookie only checks the cookie EXISTS (no DB hit at
// the Edge runtime) — do the real auth.api.getSession() check inside
// protected Server Components / route handlers. This just bounces
// logged-out users before render.
import { NextResponse, type NextRequest } from "next/server";
import { getSessionCookie } from "better-auth/cookies";

export function proxy(request: NextRequest) {
  const sessionCookie = getSessionCookie(request);
  if (!sessionCookie) {
    return NextResponse.redirect(new URL("/sign-in", request.url));
  }
  return NextResponse.next();
}

export const config = {
  // ponytail: guard the SaaS app surface; widen the matcher per app-type.
  matcher: ["/dashboard/:path*", "/settings/:path*"],
};

// === file: src/db/schema.ts ===
import { relations, sql } from "drizzle-orm";
import {
  check,
  index,
  int,
  mysqlTable,
  text,
  timestamp,
  unique,
  varchar,
} from "drizzle-orm/mysql-core";
// Better Auth owns identity; we only reference its `user` table by id.
import { user } from "./auth-schema";

export type CourseStatus = "draft" | "published" | "archived";
export type LessonContentType = "video" | "text" | "quiz";
export type ProgressStatus = "not_started" | "in_progress" | "completed";

/** Catalog root. Each course has one instructor (a Better Auth user). */
export const courses = mysqlTable(
  "courses",
  {
    id: varchar("id", { length: 36 }).primaryKey(),
    slug: varchar("slug", { length: 255 }).notNull().unique(),
    title: text("title").notNull(),
    // Better Auth's user.id is text — match it as varchar(255).
    instructorId: varchar("instructor_id", { length: 255 })
      .notNull()
      .references(() => user.id, { onDelete: "cascade" }),
    status: varchar("status", { length: 32 })
      .$type<CourseStatus>()
      .notNull()
      .default("draft"),
    createdAt: timestamp("created_at").notNull().defaultNow(),
  },
  (t) => [
    index("idx_course_slug").on(t.slug),
    index("idx_course_instructor").on(t.instructorId),
    check(
      "courses_status_check",
      sql`${t.status} in ('draft','published','archived')`,
    ),
  ],
);

/** Ordered sections within a course. position drives curriculum order. */
export const modules = mysqlTable(
  "modules",
  {
    id: varchar("id", { length: 36 }).primaryKey(),
    courseId: varchar("course_id", { length: 36 })
      .notNull()
      .references(() => courses.id, { onDelete: "cascade" }),
    title: text("title").notNull(),
    position: int("position").notNull().default(0),
    createdAt: timestamp("created_at").notNull().defaultNow(),
  },
  (t) => [index("idx_module_course").on(t.courseId, t.position)],
);

/** Leaf content unit. contentType selects how the lesson renders/plays. */
export const lessons = mysqlTable(
  "lessons",
  {
    id: varchar("id", { length: 36 }).primaryKey(),
    moduleId: varchar("module_id", { length: 36 })
      .notNull()
      .references(() => modules.id, { onDelete: "cascade" }),
    title: text("title").notNull(),
    position: int("position").notNull().default(0),
    contentType: varchar("content_type", { length: 32 })
      .$type<LessonContentType>()
      .notNull()
      .default("text"),
    createdAt: timestamp("created_at").notNull().defaultNow(),
  },
  (t) => [
    index("idx_lesson_module").on(t.moduleId, t.position),
    check(
      "lessons_content_type_check",
      sql`${t.contentType} in ('video','text','quiz')`,
    ),
  ],
);

/** course <-> student join. The composite unique is the enrollment identity. */
export const enrollments = mysqlTable(
  "enrollments",
  {
    id: varchar("id", { length: 36 }).primaryKey(),
    courseId: varchar("course_id", { length: 36 })
      .notNull()
      .references(() => courses.id, { onDelete: "cascade" }),
    studentId: varchar("student_id", { length: 255 })
      .notNull()
      .references(() => user.id, { onDelete: "cascade" }),
    enrolledAt: timestamp("enrolled_at").notNull().defaultNow(),
  },
  (t) => [
    unique("enrollments_course_student_unique").on(t.courseId, t.studentId),
    // Drives the learner's "my courses" list.
    index("idx_enrollment_student").on(t.studentId),
  ],
);

/** Per-lesson learner state. The composite unique is one row per student+lesson. */
export const lessonProgress = mysqlTable(
  "lesson_progress",
  {
    id: varchar("id", { length: 36 }).primaryKey(),
    lessonId: varchar("lesson_id", { length: 36 })
      .notNull()
      .references(() => lessons.id, { onDelete: "cascade" }),
    studentId: varchar("student_id", { length: 255 })
      .notNull()
      .references(() => user.id, { onDelete: "cascade" }),
    status: varchar("status", { length: 32 })
      .$type<ProgressStatus>()
      .notNull()
      .default("not_started"),
    completedAt: timestamp("completed_at"),
  },
  (t) => [
    unique("lesson_progress_student_lesson_unique").on(
      t.studentId,
      t.lessonId,
    ),
    // Drives the per-learner progress lookup (student + lesson).
    index("idx_progress_student_lesson").on(t.studentId, t.lessonId),
    check(
      "lesson_progress_status_check",
      sql`${t.status} in ('not_started','in_progress','completed')`,
    ),
  ],
);

export const coursesRelations = relations(courses, ({ one, many }) => ({
  instructor: one(user, {
    fields: [courses.instructorId],
    references: [user.id],
  }),
  modules: many(modules),
  enrollments: many(enrollments),
}));

export const modulesRelations = relations(modules, ({ one, many }) => ({
  course: one(courses, {
    fields: [modules.courseId],
    references: [courses.id],
  }),
  lessons: many(lessons),
}));

export const lessonsRelations = relations(lessons, ({ one, many }) => ({
  module: one(modules, {
    fields: [lessons.moduleId],
    references: [modules.id],
  }),
  progress: many(lessonProgress),
}));

export const enrollmentsRelations = relations(enrollments, ({ one }) => ({
  course: one(courses, {
    fields: [enrollments.courseId],
    references: [courses.id],
  }),
  student: one(user, {
    fields: [enrollments.studentId],
    references: [user.id],
  }),
}));

export const lessonProgressRelations = relations(lessonProgress, ({ one }) => ({
  lesson: one(lessons, {
    fields: [lessonProgress.lessonId],
    references: [lessons.id],
  }),
  student: one(user, {
    fields: [lessonProgress.studentId],
    references: [user.id],
  }),
}));

import { drizzle } from "drizzle-orm/mysql2";
import mysql from "mysql2/promise";

// Serverless: a small pool per short-lived instance — many instances × a big pool exhausts MySQL.
export const pool = mysql.createPool({ uri: process.env.DATABASE_URL!, connectionLimit: 2 });
export const db = drizzle({ client: pool });

import { drizzle } from "drizzle-orm/mysql2";
import mysql from "mysql2/promise";

// Long-running process: a real, reused pool (mysql2 manages idle recycling).
export const pool = mysql.createPool({ uri: process.env.DATABASE_URL!, connectionLimit: 10 });
export const db = drizzle({ client: pool });

import { drizzle } from "drizzle-orm/planetscale-serverless";
import { Client } from "@planetscale/database";

// Edge/Workers have NO TCP sockets, so mysql2 cannot run here. PlanetScale's HTTP driver
// speaks MySQL over fetch — the client that works on Workers (the MySQL analog of Neon's HTTP driver).
const client = new Client({ url: process.env.DATABASE_URL! });
export const db = drizzle({ client });