Drill 20: Improve it — Databases with Postgres

import { Pool } from 'pg'

const pool = new Pool({
  connectionString: process.env.DATABASE_URL,
  max: 10,
})

type Course = {
  id: string
  title: string
  minutes: number
}

async function findCourse(id: string): Promise<Course | null> {
  const result = await pool.query<Course>(
    'select id, title, minutes from courses where id = $1',
    [id],
  )
  return result.rows[0] ?? null
}

async function createCourse(course: Course): Promise<Course> {
  const client = await pool.connect()
  try {
    await client.query('begin')
    await client.query(
      'insert into courses (id, title, minutes) values ($1, $2, $3)',
      [course.id, course.title, course.minutes],
    )
    await client.query('commit')
    return course
  } catch (error) {
    await client.query('rollback')
    throw error
  } finally {
    client.release()
  }
}