/**
 * Persistence.js
 * Handles asynchronous saving and loading using IndexedDB.
 */
const DB_NAME = "AetherShardsDB";
const STORE_NAME = "Runs";
const VERSION = 1;

export class Persistence {
  constructor() {
    this.db = null;
  }

  async init() {
    return new Promise((resolve, reject) => {
      const request = indexedDB.open(DB_NAME, VERSION);

      request.onerror = (e) => reject("DB Error: " + e.target.error);

      request.onupgradeneeded = (e) => {
        const db = e.target.result;
        if (!db.objectStoreNames.contains(STORE_NAME)) {
          db.createObjectStore(STORE_NAME, { keyPath: "id" });
        }
      };

      request.onsuccess = (e) => {
        this.db = e.target.result;
        resolve();
      };
    });
  }

  async saveRun(runData) {
    if (!this.db) await this.init();
    return new Promise((resolve, reject) => {
      const tx = this.db.transaction([STORE_NAME], "readwrite");
      const store = tx.objectStore(STORE_NAME);
      // Always use ID 'active_run' for the single active session
      runData.id = "active_run";
      const req = store.put(runData);

      req.onsuccess = () => resolve();
      req.onerror = () => reject(req.error);
    });
  }

  async loadRun() {
    if (!this.db) await this.init();
    return new Promise((resolve, reject) => {
      const tx = this.db.transaction([STORE_NAME], "readonly");
      const store = tx.objectStore(STORE_NAME);
      const req = store.get("active_run");

      req.onsuccess = () => resolve(req.result);
      req.onerror = () => reject(req.error);
    });
  }

  async clearRun() {
    if (!this.db) await this.init();
    return new Promise((resolve, reject) => {
      const tx = this.db.transaction([STORE_NAME], "readwrite");
      const store = tx.objectStore(STORE_NAME);
      const req = store.delete("active_run");

      req.onsuccess = () => resolve();
      req.onerror = () => reject(req.error);
    });
  }
}