SaaS on Next.js 16 (App Router), Postgres (Neon) and Auth.js (NextAuth) with Resend

import { drizzle } from "drizzle-orm/postgres-js";
import postgres from "postgres";

// Neon pooled endpoint = PgBouncer transaction mode → prepared statements off.
// ponytail: single module-level client; the serverless runtime + PgBouncer do
// the pooling, so no custom pool/globalThis singleton dance needed.
const client = postgres(process.env.DATABASE_URL!, { prepare: false });

export const db = drizzle({ client });

// === file: src/db/schema.ts ===
import { relations, sql } from "drizzle-orm";
import {
  bigint,
  check,
  index,
  integer,
  pgTable,
  text,
  timestamp,
  unique,
  uuid,
} from "drizzle-orm/pg-core";
// Better Auth owns identity; we only reference its `user` table by id. With Clerk
// the identity-sync mirror occupies this same ./auth-schema slot (src/db/auth-schema.ts).
import { user } from "./auth-schema";

export type MemberRole = "owner" | "admin" | "member";
export type InvitationStatus = "pending" | "accepted" | "revoked";
export type SubscriptionStatus =
  | "trialing"
  | "active"
  | "past_due"
  | "canceled";

/** Tenant boundary: every billable/metered row hangs off an organization. */
export const organizations = pgTable(
  "organizations",
  {
    id: uuid("id").primaryKey().defaultRandom(),
    slug: text("slug").notNull().unique(),
    name: text("name").notNull(),
    createdAt: timestamp("created_at", { withTimezone: true })
      .notNull()
      .defaultNow(),
  },
  (t) => [index("idx_org_slug").on(t.slug)],
);

/** org <-> user join with role. The composite unique is the membership identity. */
export const memberships = pgTable(
  "memberships",
  {
    id: uuid("id").primaryKey().defaultRandom(),
    organizationId: uuid("organization_id")
      .notNull()
      .references(() => organizations.id, { onDelete: "cascade" }),
    // Better Auth's user.id is text — match it, don't recast.
    userId: text("user_id")
      .notNull()
      .references(() => user.id, { onDelete: "cascade" }),
    role: text("role").$type<MemberRole>().notNull().default("member"),
    createdAt: timestamp("created_at", { withTimezone: true })
      .notNull()
      .defaultNow(),
  },
  (t) => [
    unique("memberships_org_user_unique").on(t.organizationId, t.userId),
    index("idx_membership_user").on(t.userId),
    check(
      "memberships_role_check",
      sql`${t.role} in ('owner','admin','member')`,
    ),
  ],
);

/** Pending team invitations — how someone who does NOT yet have an account joins an org.
 *
 * Stores a SHA-256 of the invite token, NEVER the token itself. The raw token exists only in the
 * link that was sent, so a database dump (or a stray token in a log) cannot be replayed into org
 * access. The accept path hashes what it was given and looks up by that hash.
 *
 * Org-scoped like every other tenant table: RLS covers it on Postgres, forOrg on MySQL. It holds
 * an invitee's email address BEFORE they are a member of anything, which is exactly the kind of
 * row that must not be readable across tenants.
 */
export const invitations = pgTable(
  "invitations",
  {
    id: uuid("id").primaryKey().defaultRandom(),
    organizationId: uuid("organization_id")
      .notNull()
      .references(() => organizations.id, { onDelete: "cascade" }),
    email: text("email").notNull(),
    role: text("role").$type<MemberRole>().notNull().default("member"),
    tokenHash: text("token_hash").notNull(),
    status: text("status").$type<InvitationStatus>().notNull().default("pending"),
    // Nullable + ON DELETE SET NULL: the inviter's account going away must not cascade-delete
    // invitations that are still legitimately pending.
    invitedByUserId: text("invited_by_user_id").references(() => user.id, {
      onDelete: "set null",
    }),
    expiresAt: timestamp("expires_at", { withTimezone: true }).notNull(),
    acceptedAt: timestamp("accepted_at", { withTimezone: true }),
    createdAt: timestamp("created_at", { withTimezone: true })
      .notNull()
      .defaultNow(),
  },
  (t) => [
    // The accept path's lookup key: a token must identify at most one invitation.
    unique("invitations_token_hash_unique").on(t.tokenHash),
    // ONE row per (org, email) — re-inviting UPDATEs it rather than accumulating dead rows, which
    // also makes "resend the invite" and "invite again" the same operation instead of two.
    unique("invitations_org_email_unique").on(t.organizationId, t.email),
    index("idx_invitation_org").on(t.organizationId),
    check(
      "invitations_role_check",
      sql`${t.role} in ('owner','admin','member')`,
    ),
    check(
      "invitations_status_check",
      sql`${t.status} in ('pending','accepted','revoked')`,
    ),
  ],
);

/** Append-only record of every privileged action taken inside an organization.
 *
 * Org-scoped like the rest of the tenant surface, and APPEND-ONLY by more than convention: the RLS
 * block REVOKEs UPDATE and DELETE on this table from the application role, so the app physically
 * cannot rewrite its own history even if a future handler tries. A log the app can edit is not
 * evidence of anything, which is the only reason anyone asks for one.
 *
 * `actor_user_id` is nullable with ON DELETE SET NULL: the person who did the thing may later
 * delete their account, and the entry has to survive them — that is the case the log exists for.
 * `action` is a dotted verb ("member.role_changed"), `target` names what it happened to, and
 * `summary` is the sentence a human reads.
 */
export const auditLog = pgTable(
  "audit_log",
  {
    id: uuid("id").primaryKey().defaultRandom(),
    organizationId: uuid("organization_id")
      .notNull()
      .references(() => organizations.id, { onDelete: "cascade" }),
    actorUserId: text("actor_user_id").references(() => user.id, { onDelete: "set null" }),
    /** Dotted verb, e.g. "member.role_changed" — stable enough to filter and alert on. */
    action: text("action").notNull(),
    /** What it happened to: an email, a membership id, an invitation id. Free text on purpose;
     *  the thing referenced is often already deleted by the time anyone reads the entry. */
    target: text("target"),
    /** The sentence a human reads in the UI. Written once, at the moment of the action, when the
     *  context to phrase it well still exists. */
    summary: text("summary").notNull(),
    createdAt: timestamp("created_at", { withTimezone: true })
      .notNull()
      .defaultNow(),
  },
  (t) => [
    // The only query this table serves: one organization's entries, newest first.
    index("idx_audit_org_time").on(t.organizationId, t.createdAt),
  ],
);

/** API keys, for programmatic access to this organization's data.
 *
 * Stores a SHA-256 of the key, NEVER the key. It is shown once, at creation, and cannot be
 * recovered afterwards — the same discipline as `invitations.token_hash`, and for the same reason:
 * a database dump must not be a set of working credentials.
 *
 * `prefix` is the leading, non-secret part of the key, kept in clear so the UI can say WHICH key a
 * row is without being able to reconstruct it. Without it a revoke screen lists indistinguishable
 * rows and nobody dares click anything.
 *
 * `revoked_at` rather than a DELETE: a revoked key's usage rows still reference it, and "this key
 * was disabled on the 3rd" is exactly what someone asks after an incident.
 */
export const apiKeys = pgTable(
  "api_keys",
  {
    id: uuid("id").primaryKey().defaultRandom(),
    organizationId: uuid("organization_id")
      .notNull()
      .references(() => organizations.id, { onDelete: "cascade" }),
    name: text("name").notNull(),
    keyHash: text("key_hash").notNull(),
    prefix: text("prefix").notNull(),
    createdByUserId: text("created_by_user_id").references(() => user.id, { onDelete: "set null" }),
    lastUsedAt: timestamp("last_used_at", { withTimezone: true }),
    revokedAt: timestamp("revoked_at", { withTimezone: true }),
    createdAt: timestamp("created_at", { withTimezone: true })
      .notNull()
      .defaultNow(),
  },
  (t) => [
    // A key must identify at most one row, globally.
    unique("api_keys_hash_unique").on(t.keyHash),
    index("idx_api_keys_org").on(t.organizationId),
  ],
);

/** Catalog of billable plans (seed-managed). priceCents keeps money integer. */
export const plans = pgTable("plans", {
  id: uuid("id").primaryKey().defaultRandom(),
  slug: text("slug").notNull().unique(), // free | pro | scale
  name: text("name").notNull(),
  priceCents: integer("price_cents").notNull().default(0),
  // Monthly included credits; metering checks usage against this.
  monthlyCredits: bigint("monthly_credits", { mode: "number" })
    .notNull()
    .default(0),
});

/** One active subscription per org. Mirrors the billing provider's state. */
export const subscriptions = pgTable(
  "subscriptions",
  {
    id: uuid("id").primaryKey().defaultRandom(),
    organizationId: uuid("organization_id")
      .notNull()
      .references(() => organizations.id, { onDelete: "cascade" }),
    planId: uuid("plan_id")
      .notNull()
      .references(() => plans.id),
    status: text("status")
      .$type<SubscriptionStatus>()
      .notNull()
      .default("trialing"),
    // The generic billing-sync contract every webhook provider (Polar/Stripe/LemonSqueezy)
    // needs: the provider's subscription id as a UNIQUE idempotency key, plus the last
    // event timestamp as an out-of-order/staleness guard. The billing fragment maps a
    // provider's events onto these — it does NOT redeclare this table (compose, not duplicate).
    providerSubId: text("provider_sub_id").unique(),
    providerEventAt: timestamp("provider_event_at", { withTimezone: true }),
    currentPeriodEnd: timestamp("current_period_end", { withTimezone: true }),
    createdAt: timestamp("created_at", { withTimezone: true })
      .notNull()
      .defaultNow(),
  },
  (t) => [
    // One live subscription per org (the metering layer reads exactly one).
    unique("subscriptions_org_unique").on(t.organizationId),
    index("idx_sub_status").on(t.status),
    check(
      "subscriptions_status_check",
      sql`${t.status} in ('trialing','active','past_due','canceled')`,
    ),
  ],
);

/** Append-only credit/token meter. Roll up by org+window for quota + billing. */
export const apiUsage = pgTable(
  "api_usage",
  {
    id: uuid("id").primaryKey().defaultRandom(),
    organizationId: uuid("organization_id")
      .notNull()
      .references(() => organizations.id, { onDelete: "cascade" }),
    // Who/what spent — opaque key id, nullable for org-level system calls.
    apiKeyId: text("api_key_id"),
    creditsUsed: bigint("credits_used", { mode: "number" }).notNull(),
    createdAt: timestamp("created_at", { withTimezone: true })
      .notNull()
      .defaultNow(),
  },
  (t) => [
    // Drives the "credits used this period" rollup query.
    index("idx_usage_org_time").on(t.organizationId, t.createdAt),
  ],
);

export const organizationsRelations = relations(organizations, ({ many }) => ({
  memberships: many(memberships),
  invitations: many(invitations),
  subscriptions: many(subscriptions),
  usage: many(apiUsage),
  auditLog: many(auditLog),
  apiKeys: many(apiKeys),
}));

export const apiKeysRelations = relations(apiKeys, ({ one }) => ({
  organization: one(organizations, {
    fields: [apiKeys.organizationId],
    references: [organizations.id],
  }),
}));

export const auditLogRelations = relations(auditLog, ({ one }) => ({
  organization: one(organizations, {
    fields: [auditLog.organizationId],
    references: [organizations.id],
  }),
  actor: one(user, { fields: [auditLog.actorUserId], references: [user.id] }),
}));

export const invitationsRelations = relations(invitations, ({ one }) => ({
  organization: one(organizations, {
    fields: [invitations.organizationId],
    references: [organizations.id],
  }),
  invitedBy: one(user, {
    fields: [invitations.invitedByUserId],
    references: [user.id],
  }),
}));

export const membershipsRelations = relations(memberships, ({ one }) => ({
  organization: one(organizations, {
    fields: [memberships.organizationId],
    references: [organizations.id],
  }),
  user: one(user, { fields: [memberships.userId], references: [user.id] }),
}));

export const subscriptionsRelations = relations(subscriptions, ({ one }) => ({
  organization: one(organizations, {
    fields: [subscriptions.organizationId],
    references: [organizations.id],
  }),
  plan: one(plans, {
    fields: [subscriptions.planId],
    references: [plans.id],
  }),
}));

export const apiUsageRelations = relations(apiUsage, ({ one }) => ({
  organization: one(organizations, {
    fields: [apiUsage.organizationId],
    references: [organizations.id],
  }),
}));

import { and, eq, isNull, lt, or } from "drizzle-orm";
import { subscriptions } from "@/db/schema";

export type PolarSubscriptionEvent = {
  type: string;
  data: {
    id: string;
    status: string;
    currentPeriodEnd: string | null;
    modifiedAt: string;
    metadata: { organizationId: string; planId: string };
  };
};

const STATUS_MAP: Record<string, "trialing" | "active" | "past_due" | "canceled"> = {
  trialing: "trialing",
  active: "active",
  past_due: "past_due",
  unpaid: "past_due",
  canceled: "canceled",
  revoked: "canceled",
};

// Idempotent + CONCURRENCY-safe sync of a Polar subscription. The staleness guard
// lives in the UPDATE's WHERE clause, so Postgres' row lock serializes concurrent
// retries (a stale/older event matches no row); brand-new rows insert with
// onConflictDoNothing (race-safe). Returns changed=true only on a real advance, so
// callers can guard side effects (emails) against Polar's duplicate deliveries.
export async function recordPolarEvent(
  // ponytail: loosely typed Drizzle client so the emitted core stays portable
  // across the app's exact client type.
  db: any,
  event: PolarSubscriptionEvent,
): Promise<{ changed: boolean }> {
  const sub = event.data;
  const status = STATUS_MAP[sub.status];
  if (!status) return { changed: false }; // unknown status — ignore, don't default
  const eventAt = new Date(sub.modifiedAt);
  const currentPeriodEnd = sub.currentPeriodEnd ? new Date(sub.currentPeriodEnd) : null;

  // Guarded UPDATE: applies only when our event is strictly newer than what's stored.
  // No TOCTOU — the comparison is in the WHERE, evaluated under the row lock.
  const updated = await db
    .update(subscriptions)
    .set({ status, currentPeriodEnd, providerEventAt: eventAt })
    .where(
      and(
        eq(subscriptions.providerSubId, sub.id),
        or(isNull(subscriptions.providerEventAt), lt(subscriptions.providerEventAt, eventAt)),
      ),
    )
    .returning({ id: subscriptions.id });
  if (updated.length > 0) return { changed: true };

  // No row updated: the row exists but our event is stale (guard rejected it), or it
  // doesn't exist yet. If it exists, this is a stale/duplicate delivery — ignore.
  const [existing] = await db
    .select({ id: subscriptions.id })
    .from(subscriptions)
    .where(eq(subscriptions.providerSubId, sub.id))
    .limit(1);
  if (existing) return { changed: false };

  const inserted = await db
    .insert(subscriptions)
    .values({
      organizationId: sub.metadata.organizationId,
      planId: sub.metadata.planId,
      status,
      currentPeriodEnd,
      providerSubId: sub.id,
      providerEventAt: eventAt,
    })
    .onConflictDoNothing({ target: subscriptions.providerSubId })
    .returning({ id: subscriptions.id });

  return { changed: inserted.length > 0 };
}

-- IMPORTANT: RLS is bypassed by the table owner (unless FORCEd) and ALWAYS by
-- BYPASSRLS / superuser roles. Neon's default neondb_owner role has BYPASSRLS, so
-- connecting your app as neondb_owner makes RLS SILENTLY INERT. Create a dedicated
-- non-BYPASSRLS role and point your app's DATABASE_URL at it:
DO $$ BEGIN
  IF NOT EXISTS (SELECT FROM pg_roles WHERE rolname = 'app_tenant') THEN
    CREATE ROLE app_tenant NOLOGIN NOBYPASSRLS;
  END IF;
END $$;
-- Grant LOGIN + a password OUT OF BAND (never in committed SQL), then point DATABASE_URL at it:
--   ALTER ROLE app_tenant LOGIN PASSWORD '<generated>';
GRANT USAGE ON SCHEMA public TO app_tenant;
GRANT SELECT, INSERT, UPDATE, DELETE ON ALL TABLES IN SCHEMA public TO app_tenant;
-- Future tables stay covered (the one-time GRANT above only sees today's tables):
ALTER DEFAULT PRIVILEGES IN SCHEMA public GRANT SELECT, INSERT, UPDATE, DELETE ON TABLES TO app_tenant;

-- Tenant isolation via Row-Level Security (FORCE = even the table owner is bound). The shared `plans` catalog is intentionally left open.

ALTER TABLE organizations ENABLE ROW LEVEL SECURITY;
ALTER TABLE organizations FORCE ROW LEVEL SECURITY;
CREATE POLICY organizations_tenant_isolation ON organizations
  USING (id = current_setting('app.current_org_id', true)::uuid)
  WITH CHECK (id = current_setting('app.current_org_id', true)::uuid);

ALTER TABLE memberships ENABLE ROW LEVEL SECURITY;
ALTER TABLE memberships FORCE ROW LEVEL SECURITY;
CREATE POLICY memberships_tenant_isolation ON memberships
  USING (organization_id = current_setting('app.current_org_id', true)::uuid)
  WITH CHECK (organization_id = current_setting('app.current_org_id', true)::uuid);

ALTER TABLE invitations ENABLE ROW LEVEL SECURITY;
ALTER TABLE invitations FORCE ROW LEVEL SECURITY;
CREATE POLICY invitations_tenant_isolation ON invitations
  USING (organization_id = current_setting('app.current_org_id', true)::uuid)
  WITH CHECK (organization_id = current_setting('app.current_org_id', true)::uuid);

ALTER TABLE audit_log ENABLE ROW LEVEL SECURITY;
ALTER TABLE audit_log FORCE ROW LEVEL SECURITY;
CREATE POLICY audit_log_tenant_isolation ON audit_log
  USING (organization_id = current_setting('app.current_org_id', true)::uuid)
  WITH CHECK (organization_id = current_setting('app.current_org_id', true)::uuid);

ALTER TABLE api_keys ENABLE ROW LEVEL SECURITY;
ALTER TABLE api_keys FORCE ROW LEVEL SECURITY;
CREATE POLICY api_keys_tenant_isolation ON api_keys
  USING (organization_id = current_setting('app.current_org_id', true)::uuid)
  WITH CHECK (organization_id = current_setting('app.current_org_id', true)::uuid);

ALTER TABLE subscriptions ENABLE ROW LEVEL SECURITY;
ALTER TABLE subscriptions FORCE ROW LEVEL SECURITY;
CREATE POLICY subscriptions_tenant_isolation ON subscriptions
  USING (organization_id = current_setting('app.current_org_id', true)::uuid)
  WITH CHECK (organization_id = current_setting('app.current_org_id', true)::uuid);

ALTER TABLE api_usage ENABLE ROW LEVEL SECURITY;
ALTER TABLE api_usage FORCE ROW LEVEL SECURITY;
CREATE POLICY api_usage_tenant_isolation ON api_usage
  USING (organization_id = current_setting('app.current_org_id', true)::uuid)
  WITH CHECK (organization_id = current_setting('app.current_org_id', true)::uuid);

-- The audit log is append-only. RLS above scopes it per tenant; this is the
-- other half, and it is enforced by the database rather than by everyone remembering: the app role
-- may INSERT entries and SELECT its own organization's, and physically cannot rewrite or erase
-- them. A log the app can edit is not evidence of anything, which is the only reason anyone asks
-- for one. Must run AFTER the broader GRANT in the role setup above, which this narrows.
REVOKE UPDATE, DELETE ON audit_log FROM app_tenant;

import { drizzle } from "drizzle-orm/postgres-js";
import postgres from "postgres";

// Serverless: one connection per (short-lived) instance; Neon's pooler multiplexes.
export const sql = postgres(process.env.DATABASE_URL!, { prepare: false, max: 1 });
export const db = drizzle(sql);

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interface WelcomeEmailProps {
  name: string;
  ctaUrl: string;
  unsubscribeUrl: string;
}

export default function WelcomeEmail({ name, ctaUrl, unsubscribeUrl }: WelcomeEmailProps) {
  return (
    <Html lang="en">
      <Head>
        <title>Welcome aboard</title>
        <meta charSet="utf-8" />
      </Head>
      <Preview>You're in — here's how to get started.</Preview>
      <Body style={main}>
        <Container style={container}>
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          <Section style={buttonWrap}>
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          </Section>
          <Hr style={hr} />
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          </Text>
        </Container>
      </Body>
    </Html>
  );
}

WelcomeEmail.PreviewProps = { name: "Ada", ctaUrl: "https://example.com/action", unsubscribeUrl: "https://example.com/unsubscribe" } satisfies WelcomeEmailProps;

const main = { backgroundColor: "#f4f4f5", fontFamily: "-apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, sans-serif", padding: "32px 0" };
const container = { backgroundColor: "#ffffff", margin: "0 auto", padding: "32px", maxWidth: "480px", borderRadius: "8px" };
const heading = { color: "#111827", fontSize: "22px", fontWeight: 700, margin: "0 0 16px" };
const paragraph = { color: "#374151", fontSize: "15px", lineHeight: "24px", margin: "0 0 16px" };
const buttonWrap = { margin: "24px 0" };
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const hr = { borderColor: "#e5e7eb", margin: "24px 0" };
const footer = { color: "#4b5563", fontSize: "12px", lineHeight: "18px", margin: "0 0 4px" };
const footerLink = { color: "#4b5563", textDecoration: "underline" };