<?php

/**
 * @package     MokoSuiteBackup
 * @subpackage  com_mokosuitebackup
 * @author      Moko Consulting <hello@mokoconsulting.tech>
 * @copyright   Copyright (C) 2026 Moko Consulting. All rights reserved.
 * @license     GNU General Public License version 3 or later; see LICENSE
 *
 * Pre-flight validation for backup operations.
 *
 * Runs before any backup record is created, catching problems early
 * with clear messages instead of failing mid-backup. Returns a result
 * with errors (blockers) and warnings (informational).
 */

namespace Joomla\Component\MokoSuiteBackup\Administrator\Engine;

defined('_JEXEC') or die;

use Joomla\CMS\Factory;
use Joomla\Component\MokoSuiteBackup\Administrator\Utility\BackupDirectory;

class PreflightCheck
{
	/** @var string[] Fatal issues that prevent backup from starting */
	private array $errors = [];

	/** @var string[] Non-fatal issues the user should know about */
	private array $warnings = [];

	/**
	 * Run all pre-flight checks for a backup profile.
	 *
	 * @param   int  $profileId  Profile to validate
	 *
	 * @return  array{pass: bool, errors: string[], warnings: string[]}
	 */
	public function run(int $profileId): array
	{
		try {
			$db = Factory::getDbo();
		} catch (\Exception $e) {
			$this->errors[] = 'Cannot connect to database: ' . $e->getMessage();

			return $this->result();
		}

		// Load profile
		try {
			$query = $db->getQuery(true)
				->select('*')
				->from($db->quoteName('#__mokosuitebackup_profiles'))
				->where($db->quoteName('id') . ' = ' . (int) $profileId);
			$db->setQuery($query);
			$profile = $db->loadObject();
		} catch (\Exception $e) {
			$this->errors[] = 'Cannot load profile: ' . $e->getMessage();

			return $this->result();
		}

		if (!$profile) {
			$this->errors[] = 'Profile not found: #' . $profileId;

			return $this->result();
		}

		if (!$profile->published) {
			$this->errors[] = 'Profile is unpublished: ' . $profile->title;

			return $this->result();
		}

		$this->checkPhpExtensions($profile);
		$this->checkBackupDirectory($profile);
		$this->checkDiskSpace($profile, $db);
		$this->checkRunningBackup($profile, $db);
		$this->checkExcludedTables($profile, $db);
		$this->checkRemoteCredentials($profile, $db);

		return $this->result();
	}

	/**
	 * Check that required PHP extensions are loaded.
	 */
	private function checkPhpExtensions(object $profile): void
	{
		$required = ['pdo', 'pdo_mysql', 'mbstring'];

		// ZIP is required unless using tar.gz
		$format = $profile->archive_format ?? 'zip';

		if ($format === 'zip') {
			$required[] = 'zip';
		}

		foreach ($required as $ext) {
			if (!extension_loaded($ext)) {
				$this->errors[] = 'Missing required PHP extension: ext-' . $ext;
			}
		}

		if (!empty($profile->ntfy_topic) && !extension_loaded('curl')) {
			$this->warnings[] = 'ext-curl is not loaded — ntfy notifications will not work';
		}
	}

	/**
	 * Check that the backup directory exists and is writable.
	 */
	private function checkBackupDirectory(object $profile): void
	{
		$configuredDir = $profile->backup_dir ?: BackupDirectory::PLACEHOLDER;

		// Resolve placeholders using a temporary resolver
		$resolver   = new PlaceholderResolver($profile);
		$resolvedDir = BackupDirectory::resolve($resolver->resolve($configuredDir));

		if (BackupDirectory::hasPlaceholders($resolvedDir)) {
			$this->warnings[] = 'Backup directory contains unresolved placeholders: ' . $resolvedDir
				. ' — directory cannot be validated until backup runs';

			return;
		}

		if (!is_dir($resolvedDir)) {
			// Try to create it
			if (!@mkdir($resolvedDir, 0755, true)) {
				$lastError = error_get_last();
				$reason    = $lastError['message'] ?? 'unknown reason';
				$this->errors[] = 'Backup directory does not exist and cannot be created: ' . $resolvedDir
					. ' (' . $reason . ')';

				return;
			}
		}

		if (!is_writable($resolvedDir)) {
			$this->errors[] = 'Backup directory is not writable: ' . $resolvedDir;
		}
	}

	/**
	 * Check available disk space against the last backup size + 20% buffer.
	 * Skipped if no previous backup exists for this profile.
	 */
	private function checkDiskSpace(object $profile, object $db): void
	{
		$configuredDir = $profile->backup_dir ?: BackupDirectory::PLACEHOLDER;
		$resolver      = new PlaceholderResolver($profile);
		$resolvedDir   = BackupDirectory::resolve($resolver->resolve($configuredDir));

		if (BackupDirectory::hasPlaceholders($resolvedDir) || !is_dir($resolvedDir)) {
			return;
		}

		// Find last successful backup size for this profile
		$query = $db->getQuery(true)
			->select($db->quoteName('total_size'))
			->from($db->quoteName('#__mokosuitebackup_records'))
			->where($db->quoteName('profile_id') . ' = ' . (int) $profile->id)
			->where($db->quoteName('status') . ' IN (' . implode(',', array_map([$db, 'quote'], ['complete', 'warning'])) . ')')
			->where($db->quoteName('total_size') . ' > 0')
			->order($db->quoteName('backupstart') . ' DESC');
		$db->setQuery($query, 0, 1);
		$lastSize = (int) $db->loadResult();

		if ($lastSize === 0) {
			// No previous backup — skip disk space check
			return;
		}

		$requiredBytes = (int) ($lastSize * 1.2); // 20% buffer
		$freeBytes     = @disk_free_space($resolvedDir);

		if ($freeBytes === false) {
			$this->warnings[] = 'Could not determine free disk space for: ' . $resolvedDir;

			return;
		}

		if ($freeBytes < $requiredBytes) {
			$freeMB    = number_format($freeBytes / 1048576, 1);
			$neededMB  = number_format($requiredBytes / 1048576, 1);

			$this->warnings[] = 'Low disk space: ' . $freeMB . ' MB free, estimated ' . $neededMB . ' MB needed'
				. ' (based on last backup + 20% buffer)';
		}
	}

	private const STALE_TIMEOUT_MINUTES = 30;

	/**
	 * Check if another backup is already running for this profile.
	 *
	 * Backups running longer than STALE_TIMEOUT_MINUTES are automatically
	 * marked as failed so they don't permanently block future runs.
	 */
	private function checkRunningBackup(object $profile, object $db): void
	{
		$query = $db->getQuery(true)
			->select($db->quoteName(['id', 'backupstart', 'absolute_path']))
			->from($db->quoteName('#__mokosuitebackup_records'))
			->where($db->quoteName('profile_id') . ' = ' . (int) $profile->id)
			->where($db->quoteName('status') . ' = ' . $db->quote('running'));
		$db->setQuery($query);
		$rows = $db->loadObjectList();

		if (empty($rows)) {
			return;
		}

		$cutoff     = time() - (self::STALE_TIMEOUT_MINUTES * 60);
		$stillAlive = 0;

		foreach ($rows as $row) {
			$started = strtotime($row->backupstart);

			if ($started !== false && $started < $cutoff) {
				$update = $db->getQuery(true)
					->update($db->quoteName('#__mokosuitebackup_records'))
					->set($db->quoteName('status') . ' = ' . $db->quote('fail'))
					->set($db->quoteName('backupend') . ' = ' . $db->quote(date('Y-m-d H:i:s')))
					->where($db->quoteName('id') . ' = ' . (int) $row->id);
				$db->setQuery($update);
				$db->execute();

				if (!empty($row->absolute_path) && is_file($row->absolute_path)) {
					@unlink($row->absolute_path);
				}

				$this->warnings[] = 'Auto-cancelled stalled backup #' . $row->id
					. ' (started ' . $row->backupstart . ', exceeded '
					. self::STALE_TIMEOUT_MINUTES . ' min timeout)';
			} else {
				$stillAlive++;
			}
		}

		if ($stillAlive > 0) {
			$this->errors[] = 'Another backup is already running for profile: ' . $profile->title
				. ' — wait for it to finish or use Cancel Stalled from the Backup Records toolbar';
		}
	}

	/**
	 * Check that excluded tables actually exist in the database.
	 * Missing tables are warnings, not errors — the profile may have
	 * been copied from another site or a table may have been removed.
	 */
	private function checkExcludedTables(object $profile, object $db): void
	{
		$excludeRaw = BackupDirectory::parseNewlineList($profile->exclude_tables ?? '');

		if (empty($excludeRaw)) {
			return;
		}

		$prefix    = $db->getPrefix();
		$allTables = array_flip($db->getTableList());

		foreach ($excludeRaw as $entry) {
			// Strip :data-only / :structure-only suffixes
			$tableName = preg_replace('/:(?:data-only|structure-only)$/', '', $entry);

			// Resolve #__ prefix to real prefix
			$realName = str_replace('#__', $prefix, $tableName);

			if (!isset($allTables[$realName])) {
				$this->warnings[] = 'Excluded table does not exist: ' . $tableName
					. ' — it will be silently skipped during backup';
			}
		}
	}

	/**
	 * Check that remote destination credentials are minimally configured.
	 * Does not test the actual connection (too slow for preflight).
	 */
	private function checkRemoteCredentials(object $profile, object $db): void
	{
		$query = $db->getQuery(true)
			->select('*')
			->from($db->quoteName('#__mokosuitebackup_remotes'))
			->where($db->quoteName('profile_id') . ' = ' . (int) $profile->id)
			->where($db->quoteName('enabled') . ' = 1');
		$db->setQuery($query);
		$remotes = $db->loadObjectList();

		if (empty($remotes)) {
			return;
		}

		foreach ($remotes as $remote) {
			$params = json_decode($remote->params, true) ?: [];
			$label  = $remote->title ?: ('Remote #' . $remote->id);

			switch ($remote->type) {
				case 'ftp':
					if (empty($params['host'])) {
						$this->warnings[] = $label . ': FTP host is not configured — upload will fail';
					}

					if (empty($params['username'])) {
						$this->warnings[] = $label . ': FTP username is not configured — upload will fail';
					}

					break;

				case 's3':
					if (empty($params['bucket'])) {
						$this->warnings[] = $label . ': S3 bucket is not configured — upload will fail';
					}

					if (empty($params['access_key']) || empty($params['secret_key'])) {
						$this->warnings[] = $label . ': S3 credentials are not configured — upload will fail';
					}

					break;

				case 'sftp':
					if (empty($params['host'])) {
						$this->warnings[] = $label . ': SFTP host is not configured — upload will fail';
					}

					if (empty($params['username'])) {
						$this->warnings[] = $label . ': SFTP username is not configured — upload will fail';
					}

					if (empty($params['key_data']) && empty($params['password'])) {
						$this->warnings[] = $label . ': SFTP requires either a private key or password — upload will fail';
					}

					break;

				case 'google_drive':
					if (empty($params['client_id']) || empty($params['client_secret'])) {
						$this->warnings[] = $label . ': Google Drive OAuth credentials are not configured — upload will fail';
					}

					if (empty($params['refresh_token'])) {
						$this->warnings[] = $label . ': Google Drive refresh token is missing — upload will fail';
					}

					break;
			}
		}
	}

	/**
	 * Build the result array.
	 */
	private function result(): array
	{
		return [
			'pass'     => empty($this->errors),
			'errors'   => $this->errors,
			'warnings' => $this->warnings,
		];
	}
}