<?php

declare(strict_types=1);

class SimpleUpdater
{
    private string $manifestUrl;
    private string $workDir;
    private string $backupDir;
    private string $currentVersion;
    private string $appRoot;
    private string $userAgent;
    /** @var string[] */
    private array $preservePaths;
    /** @var string[] */
    private array $requiredPackagePaths;

    /**
     * @param array{
     *     manifest_url?: string,
     *     work_dir?: string,
     *     backup_dir?: string,
     *     current_version?: string,
     *     app_root?: string,
     *     user_agent?: string,
     *     preserve_paths?: string[],
     *     required_package_paths?: string[]
     * } $config
     */
    public function __construct(array $config)
    {
        $this->manifestUrl = trim((string) ($config["manifest_url"] ?? ""));
        $this->workDir = rtrim((string) ($config["work_dir"] ?? ""), "/\\");
        $this->backupDir = rtrim((string) ($config["backup_dir"] ?? ""), "/\\");
        $this->currentVersion = trim((string) ($config["current_version"] ?? ""));
        $this->appRoot = rtrim((string) ($config["app_root"] ?? ""), "/\\");
        $this->userAgent = trim((string) ($config["user_agent"] ?? "Simple-PHP-Updater"));
        if ($this->userAgent === "") {
            $this->userAgent = "Simple-PHP-Updater";
        }
        $this->preservePaths = $this->normalizePathList($config["preserve_paths"] ?? null);
        if ($this->preservePaths === []) {
            $this->preservePaths = ["config.php", "data/", ".git/"];
        }
        $this->requiredPackagePaths = $this->normalizePathList($config["required_package_paths"] ?? null);
        if ($this->requiredPackagePaths === []) {
            $this->requiredPackagePaths = ["index.php", "admin/", "includes/"];
        }

        if ($this->workDir === "") {
            throw new InvalidArgumentException("Updater work directory is not configured.");
        }
        if ($this->backupDir === "") {
            throw new InvalidArgumentException("Updater backup directory is not configured.");
        }
        if ($this->currentVersion === "") {
            throw new InvalidArgumentException("Current application version is not configured.");
        }
        if ($this->appRoot === "" || !is_dir($this->appRoot)) {
            throw new InvalidArgumentException("Application root cannot be resolved.");
        }
    }

    public function getManifestUrl(): string
    {
        return $this->manifestUrl;
    }

    public function getCurrentVersion(): string
    {
        return $this->currentVersion;
    }

    public function fetchManifest(): array
    {
        if ($this->manifestUrl === "") {
            throw new RuntimeException("UPDATE_MANIFEST_URL is not configured.");
        }

        $body = $this->httpGet($this->manifestUrl, 15);
        $manifest = json_decode($body, true);
        if (!is_array($manifest)) {
            throw new RuntimeException("Manifest response is not valid JSON.");
        }

        $version = trim((string) ($manifest["version"] ?? $manifest["latest"] ?? ""));
        $packageUrl = trim((string) ($manifest["package_url"] ?? ""));
        $sha256 = strtolower(trim((string) ($manifest["sha256"] ?? "")));
        $size = isset($manifest["size"]) ? (int) $manifest["size"] : 0;
        $publishedAt = trim((string) ($manifest["published_at"] ?? ""));

        if (!self::isVersion($version)) {
            throw new RuntimeException("Manifest version is invalid.");
        }
        if (!filter_var($packageUrl, FILTER_VALIDATE_URL)) {
            throw new RuntimeException("Manifest package URL is invalid.");
        }
        if (!preg_match('/^[a-f0-9]{64}$/', $sha256)) {
            throw new RuntimeException("Manifest checksum is invalid.");
        }

        return [
            "version" => $version,
            "package_url" => $packageUrl,
            "sha256" => $sha256,
            "size" => $size,
            "published_at" => $publishedAt,
        ];
    }

    public function updateAvailable(array $manifest): bool
    {
        return version_compare(
            self::versionToCompare((string) ($manifest["version"] ?? "")),
            self::versionToCompare($this->currentVersion),
            ">",
        );
    }

    public function deploy(array $manifest): array
    {
        $version = (string) ($manifest["version"] ?? "");
        if (!self::isVersion($version)) {
            throw new RuntimeException("Manifest version is invalid.");
        }

        $runId = date("Ymd-His");
        $workDir = $this->workDir . DIRECTORY_SEPARATOR . $runId;
        $stageDir = $workDir . DIRECTORY_SEPARATOR . "stage";
        $zipFile = $workDir . DIRECTORY_SEPARATOR . "package.zip";
        $backupDir = $this->backupDir .
            DIRECTORY_SEPARATOR .
            $runId .
            "-" .
            $version;

        try {
            self::ensureDirectory($workDir);
            $this->downloadPackage($manifest, $zipFile);
            $this->extractPackage($zipFile, $stageDir);
            $result = $this->copyWithBackup($stageDir, $backupDir);
        } finally {
            self::removeDirectory($workDir);
        }

        $removedBackups = $this->cleanupOldBackups($backupDir);

        return [
            "backup_dir" => $backupDir,
            "copied" => $result["copied"],
            "backed_up" => $result["backed_up"],
            "removed_backups" => $removedBackups,
            "skipped" => $result["skipped"],
        ];
    }

    public static function versionToCompare(string $version): string
    {
        return ltrim(trim($version), "vV");
    }

    public static function isVersion(string $version): bool
    {
        return preg_match('/^v\d+\.\d+\.\d+$/', $version) === 1;
    }

    public static function ensureDirectory(string $dir): void
    {
        if (!is_dir($dir) && !mkdir($dir, 02775, true) && !is_dir($dir)) {
            throw new RuntimeException("Directory cannot be created: " . $dir);
        }

        @chmod($dir, 02775);
    }

    public static function removeDirectory(string $dir): void
    {
        if (!is_dir($dir)) {
            return;
        }

        $items = new RecursiveIteratorIterator(
            new RecursiveDirectoryIterator($dir, FilesystemIterator::SKIP_DOTS),
            RecursiveIteratorIterator::CHILD_FIRST,
        );

        foreach ($items as $item) {
            if ($item->isDir()) {
                rmdir($item->getPathname());
            } else {
                unlink($item->getPathname());
            }
        }

        rmdir($dir);
    }

    private function httpGet(string $url, int $timeout): string
    {
        if (!filter_var($url, FILTER_VALIDATE_URL)) {
            throw new RuntimeException("Invalid URL: " . $url);
        }

        $context = stream_context_create([
            "http" => [
                "method" => "GET",
                "timeout" => $timeout,
                "ignore_errors" => true,
                "header" => "User-Agent: " . $this->userAgent . "\r\n",
            ],
        ]);

        $body = @file_get_contents($url, false, $context);
        $status = 0;
        $responseHeaders = function_exists("http_get_last_response_headers")
            ? http_get_last_response_headers()
            : [];
        if (is_array($responseHeaders)) {
            foreach ($responseHeaders as $header) {
                if (preg_match('/^HTTP\/\S+\s+(\d+)/', $header, $matches)) {
                    $status = (int) $matches[1];
                }
            }
        }

        if ($body === false || ($status >= 400 && $status < 600)) {
            throw new RuntimeException(
                "HTTP request failed" . ($status > 0 ? " with status " . $status : "") . ".",
            );
        }

        return $body;
    }

    private function downloadPackage(array $manifest, string $targetFile): void
    {
        self::ensureDirectory(dirname($targetFile));

        $data = $this->httpGet((string) $manifest["package_url"], 120);
        if ($data === "") {
            throw new RuntimeException("Downloaded package is empty.");
        }

        if (file_put_contents($targetFile, $data, LOCK_EX) === false) {
            throw new RuntimeException("Downloaded package cannot be written.");
        }

        if ((int) $manifest["size"] > 0 && filesize($targetFile) !== (int) $manifest["size"]) {
            unlink($targetFile);
            throw new RuntimeException("Downloaded package size mismatch.");
        }

        $actualHash = strtolower(hash_file("sha256", $targetFile) ?: "");
        if ($actualHash !== (string) $manifest["sha256"]) {
            unlink($targetFile);
            throw new RuntimeException("Package checksum mismatch.");
        }
    }

    private function extractPackage(string $zipFile, string $stageDir): void
    {
        if (!class_exists("ZipArchive")) {
            throw new RuntimeException("PHP ZipArchive extension is not available.");
        }

        self::removeDirectory($stageDir);
        self::ensureDirectory($stageDir);

        $zip = new ZipArchive();
        if ($zip->open($zipFile) !== true) {
            throw new RuntimeException("Downloaded package is not a readable ZIP file.");
        }

        $hasRequiredPath = false;
        for ($i = 0; $i < $zip->numFiles; $i++) {
            $name = (string) $zip->getNameIndex($i);
            if (!$this->validateZipEntry($name)) {
                $zip->close();
                throw new RuntimeException("ZIP contains an unsafe path: " . $name);
            }

            if ($this->matchesAnyConfiguredPath($name, $this->requiredPackagePaths)) {
                $hasRequiredPath = true;
            }
        }

        if (!$hasRequiredPath) {
            $zip->close();
            throw new RuntimeException("ZIP does not look like an app-root release package.");
        }

        if (!$zip->extractTo($stageDir)) {
            $zip->close();
            throw new RuntimeException("ZIP package cannot be extracted.");
        }

        $zip->close();
    }

    private function validateZipEntry(string $entry): bool
    {
        $entry = str_replace("\\", "/", $entry);
        $normalized = trim($entry, "/");

        if (
            $normalized === "" ||
            str_contains($entry, "\0") ||
            str_starts_with($entry, "/") ||
            preg_match('/^[A-Za-z]:\//', $entry)
        ) {
            return false;
        }

        foreach (explode("/", $normalized) as $segment) {
            if ($segment === "" || $segment === "." || $segment === "..") {
                return false;
            }
        }

        return true;
    }

    private function copyWithBackup(string $stageDir, string $backupDir): array
    {
        self::ensureDirectory($backupDir);

        $copied = 0;
        $backedUp = 0;
        $skipped = 0;

        $items = new RecursiveIteratorIterator(
            new RecursiveDirectoryIterator($stageDir, FilesystemIterator::SKIP_DOTS),
            RecursiveIteratorIterator::SELF_FIRST,
        );

        foreach ($items as $item) {
            $relativePath = $this->relativePath($item->getPathname(), $stageDir);
            if ($this->shouldPreservePath($relativePath)) {
                $skipped++;
                continue;
            }

            $targetPath = $this->appRoot . DIRECTORY_SEPARATOR . $relativePath;

            if ($item->isDir()) {
                self::ensureDirectory($targetPath);
                continue;
            }

            self::ensureDirectory(dirname($targetPath));

            if (file_exists($targetPath)) {
                $backupPath = $backupDir . DIRECTORY_SEPARATOR . $relativePath;
                self::ensureDirectory(dirname($backupPath));
                if (!copy($targetPath, $backupPath)) {
                    throw new RuntimeException("Cannot back up file: " . $relativePath);
                }
                $backedUp++;
            }

            if (!copy($item->getPathname(), $targetPath)) {
                throw new RuntimeException("Cannot deploy file: " . $relativePath);
            }

            @chmod($targetPath, fileperms($item->getPathname()) & 0777);
            $copied++;
        }

        return [
            "copied" => $copied,
            "backed_up" => $backedUp,
            "skipped" => $skipped,
        ];
    }

    private function cleanupOldBackups(string $keepBackupDir): int
    {
        if (!is_dir($this->backupDir)) {
            return 0;
        }

        $keepRealPath = realpath($keepBackupDir);
        $backupRootRealPath = realpath($this->backupDir);
        if ($keepRealPath === false || $backupRootRealPath === false) {
            return 0;
        }

        $removed = 0;
        $items = new DirectoryIterator($backupRootRealPath);
        foreach ($items as $item) {
            if ($item->isDot() || !$item->isDir()) {
                continue;
            }

            $path = $item->getPathname();
            if (realpath($path) === $keepRealPath) {
                continue;
            }

            self::removeDirectory($path);
            if (is_dir($path)) {
                throw new RuntimeException("Old backup directory could not be removed: " . $path);
            }
            $removed++;
        }

        return $removed;
    }

    private function shouldPreservePath(string $relativePath): bool
    {
        return $this->matchesAnyConfiguredPath($relativePath, $this->preservePaths);
    }

    private function matchesAnyConfiguredPath(string $path, array $configuredPaths): bool
    {
        $path = trim(str_replace("\\", "/", $path), "/");
        if ($path === "") {
            return true;
        }

        foreach ($configuredPaths as $configuredPath) {
            $configuredPath = str_replace("\\", "/", $configuredPath);
            $isDirectoryMatch = str_ends_with($configuredPath, "/");
            $configuredPath = trim($configuredPath, "/");
            if ($configuredPath === "") {
                continue;
            }

            if ($path === $configuredPath) {
                return true;
            }

            if (($isDirectoryMatch || !str_contains($configuredPath, ".")) &&
                str_starts_with($path, $configuredPath . "/")
            ) {
                return true;
            }
        }

        return false;
    }

    private function relativePath(string $path, string $baseDir): string
    {
        return ltrim(str_replace("\\", "/", substr($path, strlen($baseDir))), "/");
    }

    /**
     * @param mixed $paths
     * @return string[]
     */
    private function normalizePathList($paths): array
    {
        if (!is_array($paths)) {
            return [];
        }

        $normalized = [];
        foreach ($paths as $path) {
            $path = trim(str_replace("\\", "/", (string) $path));
            if ($path !== "") {
                $normalized[] = $path;
            }
        }

        return $normalized;
    }
}