<?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errors[] = 'Profile is unpublished: ' .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);

		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;
			}
		}

		// curl is only needed for remote upload and ntfy notifications
		$needsCurl = ($profile->remote_storage ?? 'none') !== 'none'
			|| !empty($profile->ntfy_topic);

		if ($needsCurl && !extension_loaded('curl')) {
			$this->warnings[] = 'ext-curl is not loaded — remote upload and 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') . ' = ' . $db->quote('complete'))
			->where($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)';
		}
	}

	/**
	 * Check if another backup is already running for this profile.
	 */
	private function checkRunningBackup(object $profile, object $db): void
	{
		$query = $db->getQuery(true)
			->select('COUNT(*)')
			->from($db->quoteName('#__mokosuitebackup_records'))
			->where($db->quoteName('profile_id') . ' = ' . (int) $profile->id)
			->where($db->quoteName('status') . ' = ' . $db->quote('running'));
		$db->setQuery($query);
		$running = (int) $db->loadResult();

		if ($running > 0) {
			$this->errors[] = 'Another backup is already running for profile: ' . $profile->title
				. ' — wait for it to finish or delete the stale record';
		}
	}

	/**
	 * 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 storage credentials are minimally configured.
	 * Does not test the actual connection (too slow for preflight).
	 */
	private function checkRemoteCredentials(object $profile): void
	{
		$remote = $profile->remote_storage ?? 'none';

		if ($remote === 'none') {
			return;
		}

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

				if (empty($profile->ftp_username)) {
					$this->warnings[] = 'FTP username is not configured — remote upload will fail';
				}

				break;

			case 's3':
				if (empty($profile->s3_bucket)) {
					$this->warnings[] = 'S3 bucket is not configured — remote upload will fail';
				}

				if (empty($profile->s3_access_key) || empty($profile->s3_secret_key)) {
					$this->warnings[] = 'S3 credentials are not configured — remote upload will fail';
				}

				break;

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

				if (empty($profile->sftp_username)) {
					$this->warnings[] = 'SFTP username is not configured — remote upload will fail';
				}

				if (empty($profile->sftp_key_data) && empty($profile->sftp_password)) {
					$this->warnings[] = 'SFTP requires either a private key or password — remote upload will fail';
				}

				break;

			case 'google_drive':
				if (empty($profile->gdrive_client_id) || empty($profile->gdrive_client_secret)) {
					$this->warnings[] = 'Google Drive OAuth credentials are not configured — remote upload will fail';
				}

				if (empty($profile->gdrive_refresh_token)) {
					$this->warnings[] = 'Google Drive refresh token is missing — remote upload will fail';
				}

				break;
		}
	}

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