<?php
/**
 * Admin JSON API for building a gallery's ZIP archive on demand.
 *
 * The archive normally rebuilds itself in the background (worker.php), but the
 * photographer sometimes wants it *now* — before sending the link out — and
 * wants to watch it happen. This drives the same archive_run_slice() the worker
 * uses, one slice per request, with assets/archive.js looping until it reports
 * finished. Every request therefore stays a few seconds under the host's 60 s
 * cap no matter how large the gallery is.
 *
 * Fields: slug, action (start | step | cancel | delete).
 */
require dirname(__DIR__) . '/app/bootstrap.php';

if (!auth_check()) {
    json_response(['error' => 'Not authenticated'], 401);
}
if ($_SERVER['REQUEST_METHOD'] !== 'POST') {
    json_response(['error' => 'POST only'], 405);
}
csrf_verify();

// Release the session lock before the slow S3 leg, exactly as the uploader
// does: PHP holds it for the whole request, and the admin would otherwise not
// be able to load another page while a build is running.
session_write_close();

@set_time_limit(0);   // honoured on some hosts; the slice budget is the real cap

$slug = (string)($_POST['slug'] ?? '');
$gallery = gallery_load($slug);
if ($gallery === null) {
    json_response(['error' => 'Unknown gallery'], 404);
}

$startedAt = microtime(true);

// One build at a time site-wide, shared with the background worker — otherwise
// a manual rebuild and a background one would fight over the same state file.
// Wait a little rather than failing instantly: the worker holds the lock through
// short sleeps while a gallery settles, and an admin who asked for this should
// not lose a race to one of them.
$lock = archive_lock(15);
if ($lock === null) {
    json_response(['error' => 'A background rebuild is running. It will finish on its own — or try again in a moment.'], 409);
}

// Whatever the wait above cost comes out of the slice, so the whole request
// still fits inside one step_seconds and cannot drift towards the 60 s cap.
$budget = max(5.0, (float)config('archive.step_seconds', 25) - (microtime(true) - $startedAt));

switch ((string)($_POST['action'] ?? '')) {
    case 'start':
        archive_abort($slug);   // discard any half-finished attempt
        json_response(archive_run_slice($slug, $budget));

    case 'step':
        json_response(archive_run_slice($slug, $budget));

    case 'cancel':
        archive_abort($slug);
        json_response(['ok' => true]);

    case 'delete':
        archive_delete($slug);
        json_response(['ok' => true]);

    default:
        json_response(['error' => 'Unknown action'], 400);
}