Drizzle ORMでスキーマとドメインモデルをどう対応させるか

// db/schema.ts
import { sqliteTable, text, integer } from 'drizzle-orm/sqlite-core';

export const customers = sqliteTable('customers', {
  id: text('id').primaryKey(),
  name: text('name').notNull(),
  email: text('email').notNull(),
  tier: text('tier', { enum: ['standard', 'premium', 'vip'] })
    .notNull()
    .default('standard'),
  createdAt: integer('created_at', { mode: 'timestamp' }).notNull(),
});

// domain/customer.ts
import type { customers } from '../db/schema';

type CustomerRow = typeof customers.$inferSelect;

export class Customer {
  private constructor(
    public readonly id: string,
    public readonly name: string,
    public readonly email: string,
    public readonly tier: 'standard' | 'premium' | 'vip'
  ) {}

  static fromRow(row: CustomerRow): Customer {
    return new Customer(row.id, row.name, row.email, row.tier);
  }

  canUpgradeToVip(totalPurchaseAmount: number): boolean {
    return this.tier === 'premium' && totalPurchaseAmount >= 500_000;
  }
}

// application/upgradeCustomer.ts
import { db } from '../db/client';
import { customers } from '../db/schema';
import { eq } from 'drizzle-orm';
import { Customer } from '../domain/customer';

export async function tryUpgradeToVip(customerId: string, totalPurchaseAmount: number) {
  const row = await db.query.customers.findFirst({ where: eq(customers.id, customerId) });
  if (!row) throw new Error('customer not found');

  const customer = Customer.fromRow(row);
  if (!customer.canUpgradeToVip(totalPurchaseAmount)) {
    return { upgraded: false as const };
  }

  await db.update(customers).set({ tier: 'vip' }).where(eq(customers.id, customerId));
  return { upgraded: true as const };
}