import { ensureFileSync } from "@std/fs";

const REFRESH_EVENT = "bm:refresh-store";

type StoreValue = string | number | boolean;

/**
 * A no-dep, lightweight, simple store for storing data in a JSON file.
 * usage:
 * ```ts
 * import { BearMetalStore } from "@bearmetal/store";
 *
 * const store = new BearMetalStore();
 *
 * store.set("key", "value");
 *
 * console.log(store.get("key"));
 *
 * store.close();
 * ```
 *
 * It's recommended to use the `using` syntax to ensure the store is disposed
 * of when it's no longer needed.
 * ```ts
 * using store = new BearMetalStore();
 *
 * store.set("key", "value");
 *
 * console.log(store.get("key"));
 * ```
 */
export class BearMetalStore {
  private store: Record<string, string | number | boolean> = {};
  private storePath: string;

  /**
   * @description The name of the event that is dispatched when the store is updated.
   */
  public readonly EVENT_NAME: string;

  constructor(storePath?: string) {
    this.storePath = storePath || Deno.env.get("BEAR_METAL_STORE_PATH") ||
      "./BearMetal/store.json";

    ensureFileSync(this.storePath);
    this.EVENT_NAME = REFRESH_EVENT + this.storePath;
    this.readIn();

    globalThis.addEventListener(this.EVENT_NAME, this.readIn);
  }

  /**
   * @param key
   * @returns The value stored at the key, or undefined if the key doesn't exist.
   */
  public get<T = StoreValue>(key: string): T {
    return this.store[key] as T;
  }

  /**
   * @description Sets the value of the key to the value.
   * @param key
   * @param value
   */
  public set(key: string, value: StoreValue): void {
    this.store[key] = value;
    this.writeOut();
  }

  /**
   * @description Deletes the key and its value.
   * @param key
   */
  public delete(key: string): void {
    delete this.store[key];
    this.writeOut();
  }

  private readIn = () => {
    this.store = JSON.parse(Deno.readTextFileSync(this.storePath) || "{}");
  };

  private writeOut() {
    Deno.writeTextFileSync(this.storePath, JSON.stringify(this.store));
    globalThis.dispatchEvent(new CustomEvent(this.EVENT_NAME));
  }

  [Symbol.dispose]() {
    this.writeOut();
    globalThis.removeEventListener(this.EVENT_NAME, this.readIn);
  }

  /**
   * @description Closes the store and disposes of the event listener.
   */
  public close() {
    this[Symbol.dispose]();
  }
}