session.ts

import { cookieHeader } from "./helpers.ts";
import type { Session, SessionOptions, SessionStorage } from "./types.ts";

export class MemorySessionStorage implements SessionStorage {
  #store: Map<string, [Record<string, unknown>, number]> = new Map();

  get(sid: string): Promise<Record<string, unknown> | undefined> {
    const [data, expires] = this.#store.get(sid) ?? [undefined, 0];
    if (expires > 0 && Date.now() > expires) {
      this.#store.delete(sid);
      return Promise.resolve(undefined);
    }
    return Promise.resolve(data);
  }

  set(sid: string, data: Record<string, unknown>, expires: number): Promise<void> {
    this.#store.set(sid, [data, expires]);
    return Promise.resolve();
  }

  delete(sid: string): Promise<void> {
    this.#store.delete(sid);
    return Promise.resolve();
  }
}

const defaultSessionStorage = new MemorySessionStorage();

export class SessionImpl<StoreType extends Record<string, unknown>> implements Session<StoreType> {
  #id: string;
  #options: SessionOptions;
  #store: StoreType | undefined;
  #storage: SessionStorage;

  constructor(id: string, options: SessionOptions = {}) {
    this.#id = id;
    this.#options = options;
    this.#storage = options.storage ?? defaultSessionStorage;
  }

  get id(): string {
    return this.#id;
  }

  get store(): StoreType | undefined {
    return this.#store;
  }

  async init(): Promise<void> {
    this.#store = (await this.#storage.get(this.#id)) as StoreType | undefined;
  }

  async update(
    store: StoreType | ((prev: StoreType | undefined) => StoreType),
  ): Promise<void> {
    if (typeof store !== "object" && typeof store !== "function") {
      throw new Error("store must be a valid object or a function");
    }

    let nextStore: StoreType | undefined;
    if (typeof store === "function") {
      nextStore = store(this.#store);
    } else {
      nextStore = store;
    }

    // save the new store
    await this.#storage.set(this.#id, nextStore, Date.now() + 1000 * (this.#options.maxAge ?? 1800));
    this.#store = nextStore;
  }

  async end(): Promise<void> {
    if (!this.#store) {
      await this.#storage.delete(this.#id);
    }
    this.#store = undefined;
  }

  redirect(url: string | URL): Response {
    const cookie = cookieHeader(
      this.#options.cookie?.name ?? "session",
      this.#id,
      {
        ...this.#options.cookie,
        expires: new Date(this.#store === undefined ? 0 : Date.now() + 1000 * (this.#options.maxAge ?? 1800)),
      },
    );
    return new Response("", {
      status: 302,
      headers: { "Set-Cookie": cookie, "Location": url.toString() },
    });
  }
}