/**
 * session.js
 * ----------
 * Page-load session restore.
 *
 * On every page load — including hard browser reloads (Ctrl+Shift+R) and
 * opening the app in a new tab — asks the server whether a job is active,
 * fetches its full snapshot, and reconnects the live SSE stream if needed.
 *
 * This does NOT depend on sessionStorage surviving the reload (though
 * sessionStorage is still written as a fast secondary hint).
 *
 * Exports
 * -------
 *   tryRestoreSession()  — call once at startup
 */

import { announce } from './state.js';
import { applySnapshot, startProgressStream } from './stream.js';
import { showResults } from './progress.js';

/**
 * Query the server for active/recent jobs and restore the UI if one is found.
 *
 * Strategy:
 *   1. GET /api/compress/active  — find the most recent running job (or any job)
 *   2. GET /api/compress/status/<id>  — fetch the full snapshot
 *   3. applySnapshot() to rebuild all progress bars
 *   4. If still running: re-attach the SSE stream
 *   5. If done/cancelled: show the results card
 */
export async function tryRestoreSession() {
  try {
    const activeResp = await fetch('/api/compress/active');
    if (!activeResp.ok) return;

    const { jobs } = await activeResp.json();
    if (!jobs.length) return;

    // Prefer the most recent running job; fall back to any job
    const candidate = jobs.find(j => j.status === 'running') || jobs[0];

    const snapResp = await fetch(`/api/compress/status/${candidate.job_id}`);
    if (!snapResp.ok) return;

    const snap = await snapResp.json();
    applySnapshot(snap);
    announce('Active compression job restored.');

    if (snap.status === 'running') {
      startProgressStream(snap.job_id, snap.files);
    } else if (snap.status === 'done' || snap.status === 'cancelled') {
      showResults(snap.status);
      sessionStorage.removeItem('vp-job-id');
    }
  } catch {
    // Server unreachable or no jobs — start fresh, no action needed
  }
}