<?php

declare(strict_types=1);

namespace Evomedien\Vitec\Service;

use TYPO3\CMS\Core\Cache\CacheManager;
use TYPO3\CMS\Core\Core\Environment;
use TYPO3\CMS\Core\Exception\SiteNotFoundException;
use TYPO3\CMS\Core\Site\SiteFinder;
use TYPO3\CMS\Core\Utility\GeneralUtility;

/**
 * Keeps the SSR routing flag file in sync with the site setting
 * "vitec.ssr.enabled" (Site Set switch, editable in the backend under
 * Site Management > Settings).
 *
 * The flag file is what public/.htaccess checks per request (RewriteCond
 * ... -f): if it exists, page requests are proxied to the SSR node on the
 * Solr VPS; if not, the SPA fallback serves _frontend/index.html as
 * before. TYPO3 itself never routes differently - the flag only steers
 * Apache, which is why a plain file is used: zero runtime cost in the
 * hot path and trivially inspectable on the server.
 *
 * Saving site settings in the TYPO3 v14 backend fires NO event (core
 * SiteWriter::writeSettings dispatches nothing, checked 2026-11-09), so
 * the sync runs self-healingly from the SyncSsrFlag middleware on every
 * frontend and backend request - a mismatch costs one file operation
 * once, agreement costs a file_exists(). The vitec:ssr-flag CLI command
 * offers the same sync plus a status view.
 */
final class SsrFlagService
{
    public function __construct(private readonly SiteFinder $siteFinder)
    {
    }

    public function getFlagPath(): string
    {
        return Environment::getVarPath() . '/vitec-ssr-on.flag';
    }

    /**
     * True as soon as ANY site enables the setting (there is only the
     * "vitec" site; iterating keeps us independent of the identifier).
     */
    public function isEnabledInSettings(): bool
    {
        try {
            foreach ($this->siteFinder->getAllSites() as $site) {
                if ((bool)$site->getSettings()->get('vitec.ssr.enabled', false)) {
                    return true;
                }
            }
        } catch (SiteNotFoundException) {
            // No sites configured - treat as disabled.
        }
        return false;
    }

    public function isFlagSet(): bool
    {
        return is_file($this->getFlagPath());
    }

    /**
     * Creates or removes the flag file so it matches the setting.
     *
     * @return bool|null The new state if something changed, null if the
     *                   flag already matched the setting.
     */
    public function sync(): ?bool
    {
        $desired = $this->isEnabledInSettings();
        if ($desired === $this->isFlagSet()) {
            return null;
        }
        if ($desired) {
            file_put_contents(
                $this->getFlagPath(),
                "SSR routing is ON (site setting vitec.ssr.enabled).\n"
                . "Managed by SsrFlagService - do not create/delete manually,\n"
                . "flip the switch in Site Management > Settings instead.\n"
                . 'Last sync: ' . date('c') . "\n"
            );
            // Fresh ON: whatever the node cached while the switch was OFF
            // is stale by definition - drop its whole page cache once.
            \TYPO3\CMS\Core\Utility\GeneralUtility::makeInstance(\Evomedien\Vitec\Service\SsrPurgeService::class)
                ->purgeQuietly(['*'], 'switch-on');
        } else {
            @unlink($this->getFlagPath());
        }
        return $desired;
    }

    /**
     * Auto-failover (vitec:ssr-health): turns SSR delivery hard OFF.
     *
     * Removing only the flag file would not stick - the self-healing
     * SyncSsrFlag middleware recreates it from the still-true site setting
     * on the very next request. So the setting itself is flipped to false
     * in config/sites/<identifier>/settings.yaml (the file the backend
     * settings editor writes, flat dotted keys), caches are flushed so the
     * compiled site settings forget the old value, and only then the flag
     * is removed. Re-enabling is deliberately manual (backend switch or
     * settings.yaml + cache flush).
     */
    public function disableSsr(): void
    {
        $changed = false;
        foreach ($this->siteFinder->getAllSites() as $site) {
            $file = Environment::getConfigPath() . '/sites/' . $site->getIdentifier() . '/settings.yaml';
            if (!is_file($file)) {
                continue;
            }
            $yaml = (string)file_get_contents($file);
            $new = preg_replace('/^(vitec\.ssr\.enabled\s*:).*$/m', '$1 false', $yaml, 1, $count);
            if ($new !== null && $count > 0 && $new !== $yaml) {
                if (file_put_contents($file, $new) === false) {
                    throw new \RuntimeException('Could not write ' . $file, 1762800001);
                }
                $changed = true;
            }
        }
        if (!$changed && $this->isEnabledInSettings()) {
            throw new \RuntimeException(
                'vitec.ssr.enabled not found in any config/sites/*/settings.yaml - cannot disable it, '
                . 'and the SyncSsrFlag middleware would recreate the flag from the setting',
                1762800002
            );
        }
        if ($changed) {
            GeneralUtility::makeInstance(CacheManager::class)->flushCaches();
        }
        @unlink($this->getFlagPath());
    }

    /**
     * Sync variant for the request hot path: never lets an IO hiccup
     * (read-only FS, concurrent unlink ...) break request handling.
     */
    public function syncQuietly(): void
    {
        try {
            $this->sync();
        } catch (\Throwable) {
            // Intentionally silent - next request retries.
        }
    }
}