<?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
 *
 * JPA (Joomla Pack Archive) unarchiver for importing Akeeba Backup files.
 *
 * JPA Format Structure:
 *   - Header: signature (3 bytes "JPA"), header length, major/minor version
 *   - Entity headers: signature (3 bytes), header length, path length, path,
 *     compression type (0=none, 1=gzip), compressed size, uncompressed size,
 *     permissions, then compressed data
 *
 * Read-only: extracts JPA archives to a staging directory.
 * The RestoreEngine can then restore from the extracted files.
 */

namespace Joomla\Component\MokoSuiteBackup\Administrator\Engine;

defined('_JEXEC') or die;

class JpaUnarchiver
{
	private const JPA_SIGNATURE    = "\x4a\x50\x41";  // "JPA"
	private const ENTITY_SIGNATURE = "\x4a\x50\x46";  // "JPF" — file entity

	private string $archivePath;
	private string $outputDir;
	private int $filesExtracted = 0;

	public function __construct(string $archivePath, string $outputDir)
	{
		$this->archivePath = $archivePath;
		$this->outputDir   = rtrim($outputDir, '/\\');
	}

	/**
	 * Extract a JPA archive to the output directory.
	 *
	 * @return  int  Number of files extracted
	 *
	 * @throws  \RuntimeException  On format errors or extraction failure
	 */
	public function extract(): int
	{
		if (!is_file($this->archivePath) || !is_readable($this->archivePath)) {
			throw new \RuntimeException('JPA file not readable: ' . $this->archivePath);
		}

		$handle = fopen($this->archivePath, 'rb');

		if ($handle === false) {
			throw new \RuntimeException('Cannot open JPA file: ' . $this->archivePath);
		}

		try {
			// Read and validate archive header
			$this->readArchiveHeader($handle);

			// Read entities until EOF
			while (!feof($handle)) {
				$pos = ftell($handle);

				// Try to read entity signature
				$sig = fread($handle, 3);

				if ($sig === false || strlen($sig) < 3) {
					break; // End of archive
				}

				if ($sig === self::ENTITY_SIGNATURE) {
					$this->readFileEntity($handle);
				} else {
					// Unknown entity — try to skip by reading header length
					fseek($handle, $pos + 3);
					$headerLenData = fread($handle, 2);

					if ($headerLenData === false || strlen($headerLenData) < 2) {
						break;
					}

					$headerLen = unpack('v', $headerLenData)[1];
					// Skip remaining header + data
					fseek($handle, $pos + 3 + $headerLen);
				}
			}

			return $this->filesExtracted;
		} finally {
			fclose($handle);
		}
	}

	/**
	 * Read and validate the JPA archive header.
	 */
	private function readArchiveHeader($handle): void
	{
		$signature = fread($handle, 3);

		if ($signature !== self::JPA_SIGNATURE) {
			throw new \RuntimeException('Not a valid JPA archive — invalid signature');
		}

		// Header length (2 bytes, little-endian)
		$headerLenData = fread($handle, 2);

		if ($headerLenData === false || strlen($headerLenData) < 2) {
			throw new \RuntimeException('Truncated JPA header');
		}

		$headerLen = unpack('v', $headerLenData)[1];

		// Version: major (1 byte), minor (1 byte)
		$versionData = fread($handle, 2);

		if ($versionData === false || strlen($versionData) < 2) {
			throw new \RuntimeException('Cannot read JPA version');
		}

		// File count (4 bytes, little-endian)
		$countData = fread($handle, 4);

		if ($countData === false || strlen($countData) < 4) {
			throw new \RuntimeException('Cannot read file count');
		}

		// Skip any remaining header bytes
		$bytesRead = 3 + 2 + 2 + 4; // sig + headerLen + version + count

		if ($headerLen > ($bytesRead - 3)) {
			$remaining = $headerLen - ($bytesRead - 3);

			if ($remaining > 0) {
				fseek($handle, ftell($handle) + $remaining);
			}
		}
	}

	/**
	 * Read a single file entity and extract it.
	 */
	private function readFileEntity($handle): void
	{
		// Entity header length (2 bytes)
		$headerLenData = fread($handle, 2);

		if ($headerLenData === false || strlen($headerLenData) < 2) {
			return;
		}

		$headerLen = unpack('v', $headerLenData)[1];

		// Path length (2 bytes)
		$pathLenData = fread($handle, 2);

		if ($pathLenData === false || strlen($pathLenData) < 2) {
			return;
		}

		$pathLen = unpack('v', $pathLenData)[1];

		// Path (variable)
		$path = fread($handle, $pathLen);

		if ($path === false || strlen($path) < $pathLen) {
			return;
		}

		// Compression type (1 byte): 0 = none, 1 = gzip
		$compTypeData = fread($handle, 1);
		$compType     = ord($compTypeData);

		// Compressed size (4 bytes)
		$compSizeData = fread($handle, 4);
		$compSize     = unpack('V', $compSizeData)[1];

		// Uncompressed size (4 bytes)
		$uncompSizeData = fread($handle, 4);
		$uncompSize     = unpack('V', $uncompSizeData)[1];

		// Permissions (4 bytes)
		$permsData = fread($handle, 4);
		$perms     = unpack('V', $permsData)[1];

		// Skip any remaining header bytes
		$entityHeaderRead = 2 + 2 + $pathLen + 1 + 4 + 4 + 4;
		$entityHeaderTotal = $headerLen;

		if ($entityHeaderTotal > $entityHeaderRead) {
			fseek($handle, ftell($handle) + ($entityHeaderTotal - $entityHeaderRead));
		}

		// Read compressed data
		$data = '';

		if ($compSize > 0) {
			$data = fread($handle, $compSize);

			if ($data === false || strlen($data) < $compSize) {
				return;
			}
		}

		// Path traversal protection: reject absolute paths and directory traversal
		if (str_starts_with($path, '/') || str_starts_with($path, '\\') || str_contains($path, '..')) {
			return; // skip malicious entry
		}

		// Is this a directory?
		if (substr($path, -1) === '/' || $uncompSize === 0 && $compSize === 0) {
			$dirPath = $this->outputDir . '/' . $path;

			if (!is_dir($dirPath)) {
				mkdir($dirPath, 0755, true);
			}

			return;
		}

		// Decompress if needed
		if ($compType === 1 && !empty($data)) {
			$data = @gzinflate($data);

			if ($data === false) {
				throw new \RuntimeException('Failed to decompress file: ' . $path);
			}
		}

		// Write file
		$fullPath  = $this->outputDir . '/' . $path;

		// Verify resolved path stays within output directory
		$realOutput = realpath($this->outputDir);

		if ($realOutput !== false) {
			$parentDir = dirname($fullPath);

			if (!is_dir($parentDir)) {
				mkdir($parentDir, 0755, true);
			}

			$realDest = realpath($parentDir);

			if ($realDest === false || !str_starts_with($realDest, $realOutput)) {
				return; // path escapes staging directory
			}
		}

		$parentDir = dirname($fullPath);

		if (!is_dir($parentDir)) {
			mkdir($parentDir, 0755, true);
		}

		file_put_contents($fullPath, $data);

		// Set permissions (only if reasonable)
		if ($perms > 0 && $perms <= 0777) {
			@chmod($fullPath, $perms);
		}

		$this->filesExtracted++;
	}

	/**
	 * Check if a file appears to be a JPA archive.
	 */
	public static function isJpaFile(string $path): bool
	{
		if (!is_file($path) || !is_readable($path)) {
			return false;
		}

		$handle = fopen($path, 'rb');

		if ($handle === false) {
			return false;
		}

		$sig = fread($handle, 3);
		fclose($handle);

		return $sig === self::JPA_SIGNATURE;
	}
}