<?php

/**
 * @package     MokoJoomBackup
 * @subpackage  com_mokojoombackup
 * @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
 *
 * AJAX step-based backup engine for shared hosting.
 *
 * Each call to runStep() performs one unit of work within the PHP time
 * limit, saves state, and returns. The browser JS fires the next step.
 *
 * This overcomes max_execution_time restrictions on shared hosting
 * where ini_set() and set_time_limit() are disabled.
 */

namespace Joomla\Component\MokoJoomBackup\Administrator\Engine;

defined('_JEXEC') or die;

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

class SteppedBackupEngine
{
	/**
	 * Initialize a new stepped backup session.
	 *
	 * @return  array{session_id: string, phase: string, progress: int, message: string}
	 */
	public function init(int $profileId, string $description = '', string $origin = 'backend'): array
	{
		$db = Factory::getDbo();

		// Load profile
		$query = $db->getQuery(true)
			->select('*')
			->from($db->quoteName('#__mokojoombackup_profiles'))
			->where($db->quoteName('id') . ' = ' . $profileId);
		$db->setQuery($query);
		$profile = $db->loadObject();

		if (!$profile) {
			return ['error' => true, 'message' => 'Profile not found: ' . $profileId];
		}

		// Create session
		$session = SteppedSession::create();
		$session->profileId = $profileId;
		$session->origin    = $origin;
		$session->backupType = $profile->backup_type;

		// Parse profile settings
		$session->excludeDirs   = BackupDirectory::parseNewlineList($profile->exclude_dirs ?? '');
		$session->excludeFiles  = BackupDirectory::parseNewlineList($profile->exclude_files ?? '');
		$session->excludeTables = BackupDirectory::parseNewlineList($profile->exclude_tables ?? '');
		$session->backupDir     = $profile->backup_dir ?: BackupDirectory::PLACEHOLDER;
		$session->remoteStorage = $profile->remote_storage ?? 'none';
		$session->includeMokoRestore = (bool) ($profile->include_mokorestore ?? false);
		$session->remoteKeepLocal  = (bool) ($profile->remote_keep_local ?? true);

		// Resolve placeholders in directory and filename
		$resolver  = new PlaceholderResolver($profile);
		$backupDir = BackupDirectory::resolve($resolver->resolve($session->backupDir));

		if (!BackupDirectory::ensureReady($backupDir)) {
			return ['error' => true, 'message' => 'Cannot create backup directory: ' . $backupDir];
		}

		$now         = date('Y-m-d H:i:s');
		$tag         = $resolver->getTag();
		$nameFormat  = $profile->archive_name_format ?? '[host]_[datetime]_profile[profile_id]';
		$archiveName = $resolver->resolve($nameFormat) . '.zip';

		$session->archivePath = $backupDir . '/' . $archiveName;
		$session->archiveName = $archiveName;
		$session->description = $description ?: ($profile->title . ' — ' . $now);

		// Create backup record
		$record = (object) [
			'profile_id'      => $profileId,
			'description'     => $session->description,
			'status'          => 'running',
			'origin'          => $origin,
			'backup_type'     => $profile->backup_type,
			'archivename'     => $archiveName,
			'absolute_path'   => $session->archivePath,
			'total_size'      => 0,
			'db_size'         => 0,
			'files_count'     => 0,
			'tables_count'    => 0,
			'multipart'       => 0,
			'tag'             => $tag,
			'backupstart'     => $now,
			'backupend'       => '0000-00-00 00:00:00',
			'filesexist'      => 0,
			'remote_filename' => '',
			'log'             => '',
		];

		$db->insertObject('#__mokojoombackup_records', $record, 'id');
		$session->recordId = $record->id;

		// Determine what work needs to be done and estimate steps
		$totalSteps = 1; // init step

		if ($profile->backup_type !== 'files') {
			// Count tables for database phase
			$tables = $this->getSiteTables($session->excludeTables);
			$session->tables = $tables;
			$totalSteps += count($tables); // one step per table
		}

		if ($profile->backup_type !== 'database') {
			// Scan files and split into batches
			$scanner = new FileScanner(JPATH_ROOT, $session->excludeDirs, $session->excludeFiles);
			$allFiles = $scanner->scan();
			$session->filesCount = count($allFiles);
			$session->fileBatches = array_chunk($allFiles, $session->batchSize);
			$totalSteps += count($session->fileBatches); // one step per batch
		}

		$totalSteps += 1; // finalize step
		$totalSteps += ($session->remoteStorage !== 'none') ? 1 : 0; // upload step

		$session->totalSteps = $totalSteps;
		$session->currentStep = 1;
		$session->phase = ($profile->backup_type !== 'files') ? 'database' : 'files';
		$session->log('Backup initialized: ' . $session->description);
		$session->log('Total steps: ' . $totalSteps . ' (tables: ' . count($session->tables) . ', file batches: ' . count($session->fileBatches) . ')');
		$session->statusMessage = 'Initialized — starting backup...';
		$session->save();

		return [
			'session_id' => $session->sessionId,
			'phase'      => $session->phase,
			'progress'   => $session->getProgress(),
			'message'    => $session->statusMessage,
		];
	}

	/**
	 * Run the next step of a backup session.
	 *
	 * @return  array{session_id: string, phase: string, progress: int, message: string, done?: bool}
	 */
	public function runStep(string $sessionId): array
	{
		$session = SteppedSession::load($sessionId);

		if (!$session) {
			return ['error' => true, 'message' => 'Session not found: ' . $sessionId];
		}

		try {
			switch ($session->phase) {
				case 'database':
					$this->stepDatabase($session);
					break;

				case 'files':
					$this->stepFiles($session);
					break;

				case 'finalize':
					$this->stepFinalize($session);
					break;

				case 'upload':
					$this->stepUpload($session);
					break;

				case 'complete':
					$session->destroy();

					return [
						'session_id' => $sessionId,
						'phase'      => 'complete',
						'progress'   => 100,
						'message'    => 'Backup complete: ' . $session->archiveName,
						'done'       => true,
					];
			}

			$session->save();

			return [
				'session_id' => $sessionId,
				'phase'      => $session->phase,
				'progress'   => $session->getProgress(),
				'message'    => $session->statusMessage,
				'done'       => $session->phase === 'complete',
			];
		} catch (\Throwable $e) {
			$session->log('FATAL: ' . $e->getMessage());
			$this->failRecord($session, $e->getMessage());
			$session->destroy();

			return ['error' => true, 'message' => 'Backup failed: ' . $e->getMessage()];
		}
	}

	/**
	 * Database phase: dump one table per step.
	 */
	private function stepDatabase(SteppedSession $session): void
	{
		if ($session->tableIndex >= count($session->tables)) {
			// Database phase complete, move to files or finalize
			$session->phase = ($session->backupType !== 'database') ? 'files' : 'finalize';
			$session->tablesCount = $session->tableIndex;
			$session->log('Database dump complete: ' . $session->tablesCount . ' tables');

			return;
		}

		$table = $session->tables[$session->tableIndex];
		$db    = Factory::getDbo();

		// Dump this single table
		$dumper = new DatabaseDumper([]);
		$sql    = $this->dumpSingleTable($db, $table);

		// Append to a temp SQL file that will be added to ZIP in finalize
		$sqlFile = $session->archivePath . '.sql';
		$flags   = $session->tableIndex === 0 ? 0 : FILE_APPEND;

		if ($session->tableIndex === 0) {
			$header = "-- MokoJoomBackup Database Dump\n"
				. "-- Generated: " . date('Y-m-d H:i:s') . "\n"
				. "-- Prefix: " . $db->getPrefix() . "\n\n"
				. "SET SQL_MODE = \"NO_AUTO_VALUE_ON_ZERO\";\n"
				. "SET time_zone = \"+00:00\";\n\n";
			if (file_put_contents($sqlFile, $header) === false) {
			throw new \RuntimeException('Cannot write SQL dump: ' . $sqlFile);
		}
			$flags = FILE_APPEND;
		}

		if (file_put_contents($sqlFile, $sql, $flags) === false) {
			throw new \RuntimeException('Cannot write SQL dump: ' . $sqlFile);
		}
		$session->dbSize += strlen($sql);

		$session->tableIndex++;
		$session->currentStep++;
		$session->statusMessage = 'Dumping table ' . $session->tableIndex . '/' . count($session->tables) . ': ' . $table;
		$session->log('Dumped table: ' . $table);
	}

	/**
	 * Files phase: add one batch of files to ZIP per step.
	 */
	private function stepFiles(SteppedSession $session): void
	{
		if ($session->batchIndex >= count($session->fileBatches)) {
			$session->phase = 'finalize';
			$session->log('Files phase complete: ' . $session->filesCount . ' files in ' . count($session->fileBatches) . ' batches');

			return;
		}

		$batch = $session->fileBatches[$session->batchIndex];
		$zip   = new \ZipArchive();
		$mode  = $session->batchIndex === 0
			? (\ZipArchive::CREATE | \ZipArchive::OVERWRITE)
			: \ZipArchive::CREATE;

		if ($zip->open($session->archivePath, $mode) !== true) {
			throw new \RuntimeException('Cannot open archive for writing');
		}

		$added = 0;

		foreach ($batch as $relativePath) {
			$fullPath = JPATH_ROOT . '/' . $relativePath;

			if (is_file($fullPath) && is_readable($fullPath)) {
				$zip->addFile($fullPath, $relativePath);
				$added++;
			}
		}

		$zip->close();

		$session->batchIndex++;
		$session->currentStep++;
		$batchNum = $session->batchIndex;
		$totalBatches = count($session->fileBatches);
		$session->statusMessage = "Adding files batch {$batchNum}/{$totalBatches} ({$added} files)";
		$session->log("Files batch {$batchNum}: {$added} files added");
	}

	/**
	 * Finalize phase: add database.sql to ZIP, apply MokoRestore wrapper.
	 */
	private function stepFinalize(SteppedSession $session): void
	{
		$zip = new \ZipArchive();

		if ($zip->open($session->archivePath, \ZipArchive::CREATE) !== true) {
			throw new \RuntimeException('Cannot open archive for finalization');
		}

		// Add database dump if it exists
		$sqlFile = $session->archivePath . '.sql';

		if (is_file($sqlFile)) {
			$zip->addFile($sqlFile, 'database.sql');
		}

		$zip->close();

		// Clean up temp SQL file
		if (is_file($sqlFile) && !@unlink($sqlFile)) {
			error_log('MokoJoomBackup: Could not delete temp SQL file: ' . $sqlFile);
		}

		$totalSize = file_exists($session->archivePath) ? filesize($session->archivePath) : 0;

		// MokoRestore wrapper
		if ($session->includeMokoRestore) {
			$session->log('Wrapping with MokoRestore script...');
			$mokoRestorePath = $session->archivePath . '.mokorestore.zip';
			MokoRestore::wrap($session->archivePath, $mokoRestorePath);
			@unlink($session->archivePath);
			rename($mokoRestorePath, $session->archivePath);
			$totalSize = filesize($session->archivePath);
			$session->log('MokoRestore archive created');
		}

		// Update record
		$db = Factory::getDbo();
		$sizeHuman = number_format($totalSize / 1048576, 2) . ' MB';

		$update = (object) [
			'id'          => $session->recordId,
			'total_size'  => $totalSize,
			'db_size'     => $session->dbSize,
			'files_count' => $session->filesCount,
			'tables_count' => $session->tablesCount,
			'filesexist'  => 1,
		];

		$db->updateObject('#__mokojoombackup_records', $update, 'id');

		$session->currentStep++;
		$session->phase = ($session->remoteStorage !== 'none') ? 'upload' : 'complete';
		$session->statusMessage = 'Archive finalized: ' . $sizeHuman;
		$session->log('Archive finalized: ' . $sizeHuman);

		if ($session->phase === 'complete') {
			$this->completeRecord($session);
		}
	}

	/**
	 * Upload phase: send archive to remote storage.
	 */
	private function stepUpload(SteppedSession $session): void
	{
		$db = Factory::getDbo();

		// Reload profile for remote settings
		$query = $db->getQuery(true)
			->select('*')
			->from($db->quoteName('#__mokojoombackup_profiles'))
			->where($db->quoteName('id') . ' = ' . $session->profileId);
		$db->setQuery($query);
		$profile = $db->loadObject();

		$uploader = match ($session->remoteStorage) {
			'ftp'          => new FtpUploader($profile),
			'google_drive' => new GoogleDriveUploader($profile),
			's3'           => new S3Uploader($profile),
			default        => throw new \InvalidArgumentException('Unknown storage: ' . $session->remoteStorage),
		};

		$session->log('Starting remote upload (' . $session->remoteStorage . ')...');
		$result = $uploader->upload($session->archivePath, $session->archiveName);

		$remoteFilename = '';

		if ($result['success']) {
			$remoteFilename = $result['remote_path'] ?? $session->archiveName;
			$session->log('Remote upload complete: ' . $result['message']);

			if (!$session->remoteKeepLocal && is_file($session->archivePath)) {
				@unlink($session->archivePath);
				$session->log('Local copy removed');
			}
		} else {
			$session->log('WARNING: Remote upload failed: ' . $result['message']);
		}

		// Update record with remote filename
		$update = (object) [
			'id'              => $session->recordId,
			'remote_filename' => $remoteFilename,
			'filesexist'      => is_file($session->archivePath) ? 1 : 0,
		];

		$db->updateObject('#__mokojoombackup_records', $update, 'id');

		$session->currentStep++;
		$session->phase = 'complete';
		$session->statusMessage = 'Backup complete';
		$this->completeRecord($session);
	}

	/**
	 * Mark the backup record as complete.
	 */
	private function completeRecord(SteppedSession $session): void
	{
		$db         = Factory::getDbo();
		$logContent = implode("\n", $session->log);

		// Write log file alongside the archive
		$logPath = BackupDirectory::logPathFromArchive($session->archivePath);
		if (@file_put_contents($logPath, $logContent) === false) {
			error_log('MokoJoomBackup: Could not write log file: ' . $logPath);
		}

		$update = (object) [
			'id'        => $session->recordId,
			'status'    => 'complete',
			'backupend' => date('Y-m-d H:i:s'),
			'log'       => $logContent,
		];

		$db->updateObject('#__mokojoombackup_records', $update, 'id');
	}

	/**
	 * Mark the backup record as failed.
	 */
	private function failRecord(SteppedSession $session, string $error): void
	{
		$db     = Factory::getDbo();
		$update = (object) [
			'id'        => $session->recordId,
			'status'    => 'fail',
			'backupend' => date('Y-m-d H:i:s'),
			'log'       => implode("\n", $session->log),
		];

		$db->updateObject('#__mokojoombackup_records', $update, 'id');
	}

	/**
	 * Dump a single table to SQL string.
	 */
	private function dumpSingleTable(object $db, string $table): string
	{
		$output = [];
		$output[] = '-- --------------------------------------------------------';
		$output[] = '-- Table: ' . $table;
		$output[] = '-- --------------------------------------------------------';
		$output[] = '';

		// CREATE TABLE
		$db->setQuery('SHOW CREATE TABLE ' . $db->quoteName($table));
		$createRow = $db->loadRow();

		if (!$createRow || empty($createRow[1])) {
			return '';
		}

		$output[] = 'DROP TABLE IF EXISTS ' . $db->quoteName($table) . ';';
		$output[] = $createRow[1] . ';';
		$output[] = '';

		// Data in chunks
		$db->setQuery('SELECT COUNT(*) FROM ' . $db->quoteName($table));
		$rowCount = (int) $db->loadResult();

		if ($rowCount === 0) {
			$output[] = '-- (empty table)';
			$output[] = '';

			return implode("\n", $output);
		}

		$chunkSize = 500;

		for ($offset = 0; $offset < $rowCount; $offset += $chunkSize) {
			$db->setQuery(
				$db->getQuery(true)->select('*')->from($db->quoteName($table)),
				$offset,
				$chunkSize
			);
			$rows = $db->loadAssocList();

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

			foreach ($rows as $row) {
				$values = [];

				foreach ($row as $value) {
					$values[] = $value === null ? 'NULL' : $db->quote($value);
				}

				$columns = array_map([$db, 'quoteName'], array_keys($row));
				$output[] = 'INSERT INTO ' . $db->quoteName($table)
					. ' (' . implode(', ', $columns) . ')'
					. ' VALUES (' . implode(', ', $values) . ');';
			}
		}

		$output[] = '';

		return implode("\n", $output);
	}

	/**
	 * Get site tables (with prefix), excluding filtered tables.
	 */
	private function getSiteTables(array $excludeTables): array
	{
		$db     = Factory::getDbo();
		$prefix = $db->getPrefix();
		$tables = [];

		foreach ($db->getTableList() as $table) {
			if (!str_starts_with($table, $prefix)) {
				continue;
			}

			$abstractName = '#__' . substr($table, strlen($prefix));

			$excluded = false;

			foreach ($excludeTables as $pattern) {
				if ($pattern === $abstractName || $pattern === $table) {
					$excluded = true;

					break;
				}
			}

			if (!$excluded) {
				$tables[] = $table;
			}
		}

		return $tables;
	}

}