Koa sessions

koa-session.ts

export interface Context<Data> extends Koa.DefaultContext {
  session: Session<Data>;
}

export class Session<Data> {
  protected static cookieName = "sessId" as const;
  protected static httpOnly = true as const;
  protected static maxAge = 1000 * 60 * 2;
  protected static sameSite = "lax" as const;

  #id: string;
  #prisma: PrismaClient;
  #context: Context<Data>;

  constructor(prisma: PrismaClient, context: Context<Data>) {
    this.#prisma = prisma;
    this.#context = context;
    this.#id = this.#context.cookies.get(Session.cookieName) || nanoid();
  }

  /** Get session data */
  public async get() {
    await this.#prisma.session.deleteMany({
      where: { expiresAt: { lte: new Date() } },
    });

    const session = await this.#prisma.session.findUnique({
      where: { id: this.#id },
    });

    if (!session) return {};

    const data = session.data as Data;
    const expiresAt = new Date(Date.now() + Session.maxAge);

    await this.#prisma.session.update({
      where: { id: this.#id },
      data: { expiresAt },
    });

    return data;
  }

  /** Updates session data and returns a copy */
  public async set(data: Jsonify<Data>) {
    const expiresAt = new Date(Date.now() + Session.maxAge);

    const session = await this.#prisma.session.upsert({
      where: { id: this.#id },
      create: { id: this.#id, data, expiresAt },
      update: { id: this.#id, data, expiresAt },
    });

    this.#context.cookies.set(Session.cookieName, this.#id, {
      httpOnly: Session.httpOnly,
      maxAge: Session.maxAge,
      sameSite: Session.sameSite,
    });

    return session.data as Data;
  }
}