Fintech ledger on React Router v8, 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, React Router v8).
import { betterAuth } from "better-auth";
import { drizzleAdapter } from "better-auth/adapters/drizzle";
// Reuse the SAME postgres-js/Drizzle client the db slice exported in
// app/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;

// Better Auth mounted as a React Router resource route (a route module with NO
// default component). auth.handler is framework-agnostic — (Request) => Response —
// so the GET loader and the POST/etc. action both delegate straight to it. The
// `$` splat catches every /api/auth/* sub-path Better Auth routes internally.
import type { LoaderFunctionArgs, ActionFunctionArgs } from "react-router";
import { auth } from "@/lib/auth";

export function loader({ request }: LoaderFunctionArgs) {
  return auth.handler(request);
}

export function action({ request }: ActionFunctionArgs) {
  return auth.handler(request);
}

// Session gate — the RR7 replacement for Next's Edge proxy. Protected loaders
// call `await requireAuth(request)`. Unlike the proxy's cookie-existence check,
// this does the REAL server-side validation via auth.api.getSession, then throws
// a redirect Response (React Router short-circuits the loader on a thrown Response)
// to bounce logged-out users before the protected data ever loads.
import { redirect } from "react-router";
import { auth } from "@/lib/auth";

export async function requireAuth(request: Request) {
  const session = await auth.api.getSession({ headers: request.headers });
  if (!session) {
    throw redirect("/sign-in");
  }
  return session;
}

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

export const accounts = mysqlTable(
  "accounts",
  {
    id: varchar("id", { length: 36 }).primaryKey(),
    ownerId: varchar("owner_id", { length: 255 }).notNull().references(() => user.id, { onDelete: "cascade" }),
    name: text("name").notNull(),
    type: varchar("type", { length: 32 }).notNull(),
    currency: text("currency").notNull().default("USD"),
    createdAt: timestamp("created_at").notNull().defaultNow(),
  },
  (t) => [
    index("idx_account_owner").on(t.ownerId),
    check("accounts_type_check", sql`${t.type} in ('asset','liability','equity','revenue','expense')`),
  ],
);

export const journalEntries = mysqlTable(
  "journal_entries",
  {
    id: varchar("id", { length: 36 }).primaryKey(),
    creatorId: varchar("creator_id", { length: 255 }).notNull().references(() => user.id, { onDelete: "cascade" }),
    description: text("description").notNull(),
    postedAt: timestamp("posted_at").notNull().defaultNow(),
  },
  (t) => [index("idx_entry_posted").on(t.postedAt)],
);

// Double-entry: each entry has >= 2 lines; debits must equal credits (enforced in app).
export const journalLines = mysqlTable(
  "journal_lines",
  {
    id: varchar("id", { length: 36 }).primaryKey(),
    entryId: varchar("entry_id", { length: 36 }).notNull().references(() => journalEntries.id, { onDelete: "cascade" }),
    accountId: varchar("account_id", { length: 36 }).notNull().references(() => accounts.id, { onDelete: "cascade" }),
    direction: varchar("direction", { length: 32 }).notNull(),
    amountCents: bigint("amount_cents", { mode: "number" }).notNull(),
  },
  (t) => [
    index("idx_line_account").on(t.accountId),
    index("idx_line_entry").on(t.entryId),
    check("journal_lines_direction_check", sql`${t.direction} in ('debit','credit')`),
  ],
);

export const accountsRelations = relations(accounts, ({ one, many }) => ({
  owner: one(user, { fields: [accounts.ownerId], references: [user.id] }),
  lines: many(journalLines),
}));
export const journalEntriesRelations = relations(journalEntries, ({ one, many }) => ({
  creator: one(user, { fields: [journalEntries.creatorId], references: [user.id] }),
  lines: many(journalLines),
}));
export const journalLinesRelations = relations(journalLines, ({ one }) => ({
  entry: one(journalEntries, { fields: [journalLines.entryId], references: [journalEntries.id] }),
  account: one(accounts, { fields: [journalLines.accountId], references: [accounts.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 });