<?php
// Status report to the Manage server.
//
// There is no cron on this host, so the heartbeat rides along with admin page
// loads: throttled on admin/settings.php via manageHeartbeatSendIfDue(), and
// unthrottled right after a backup or an update, when the reported values have
// just changed.
//
// The response doubles as a cheap update check, which is why the server
// dashboard stays current without polling the shop.

declare(strict_types=1);

function manageHeartbeatPayload(): array
{
    $lastBackupAt = '';
    $pendingMigrations = 0;

    try {
        $backups = manageBackupList();
        if ($backups !== []) {
            $lastBackupAt = (string) ($backups[0]['created_at'] ?? '');
        }
    } catch (Throwable $exception) {
        // A broken backup index must not stop the heartbeat; the server simply
        // keeps its previous value.
        manageClientLog('WARNING', 'Heartbeat could not read backup index', [
            'error' => $exception->getMessage(),
        ]);
    }

    try {
        $pendingMigrations = count(manageUpdatePendingMigrations());
    } catch (Throwable $exception) {
        manageClientLog('WARNING', 'Heartbeat could not read migrations', [
            'error' => $exception->getMessage(),
        ]);
    }

    $diskFree = 0;
    $free = @disk_free_space(manageClientAppRoot());
    if (is_float($free) || is_int($free)) {
        $diskFree = (int) $free;
    }

    return [
        'version' => manageClientVersion(),
        'php_version' => PHP_VERSION,
        'disk_free' => $diskFree,
        'pending_migrations' => $pendingMigrations,
        'last_backup_at' => $lastBackupAt,
    ];
}

/**
 * Sends the heartbeat.
 *
 * @return array{success: bool, latest: string, update_available: bool, server_time: string}
 */
function manageHeartbeatSend(): array
{
    $decoded = manageClientRequestJson(
        'POST',
        'heartbeat.php',
        manageHeartbeatPayload(),
        (int) MANAGE_HTTP_TIMEOUT
    );

    manageWriteJson((string) MANAGE_HEARTBEAT_STATE, [
        'sent_at' => date(DATE_ATOM),
        'latest' => (string) ($decoded['latest'] ?? ''),
        'update_available' => !empty($decoded['update_available']),
    ]);

    return [
        'success' => !empty($decoded['success']),
        'latest' => (string) ($decoded['latest'] ?? ''),
        'update_available' => !empty($decoded['update_available']),
        'server_time' => (string) ($decoded['server_time'] ?? ''),
    ];
}

/**
 * Heartbeat that never throws. For call sites inside a page render, where an
 * unreachable server must not surface as an error.
 */
function manageHeartbeatSendQuietly(): ?array
{
    if (!manageClientConfigured()) {
        return null;
    }

    try {
        return manageHeartbeatSend();
    } catch (Throwable $exception) {
        manageClientLog('WARNING', 'Heartbeat failed', ['error' => $exception->getMessage()]);

        return null;
    }
}

function manageHeartbeatLastSentAt(): int
{
    $timestamp = strtotime((string) (manageReadJson((string) MANAGE_HEARTBEAT_STATE)['sent_at'] ?? ''));

    return $timestamp === false ? 0 : $timestamp;
}

/**
 * Sends a heartbeat at most once per hour, so opening the settings page
 * repeatedly does not mean one HTTP round trip per render. Never throws.
 */
function manageHeartbeatSendIfDue(int $intervalSeconds = 3600): ?array
{
    if (time() - manageHeartbeatLastSentAt() < max(1, $intervalSeconds)) {
        return null;
    }

    return manageHeartbeatSendQuietly();
}