<?php

/**
 * This file is part of the Nette Framework (https://nette.org)
 * Copyright (c) 2004 David Grudl (https://davidgrudl.com)
 */

declare(strict_types=1);

namespace Nette\Http;

use Nette;


/**
 * Provides access to session sections as well as session settings and management methods.
 */
class Session
{
	use Nette\SmartObject;

	/** Default file lifetime */
	private const DEFAULT_FILE_LIFETIME = 3 * Nette\Utils\DateTime::HOUR;

	/** @var array default configuration */
	private const SECURITY_OPTIONS = [
		'referer_check' => '',    // must be disabled because PHP implementation is invalid
		'use_cookies' => 1,       // must be enabled to prevent Session Hijacking and Fixation
		'use_only_cookies' => 1,  // must be enabled to prevent Session Fixation
		'use_trans_sid' => 0,     // must be disabled to prevent Session Hijacking and Fixation
		'use_strict_mode' => 1,   // must be enabled to prevent Session Fixation
		'cookie_httponly' => true, // must be enabled to prevent Session Hijacking
	];

	/** @var bool  has been session ID regenerated? */
	private $regenerated = false;

	/** @var bool  has been session started by Nette? */
	private $started = false;

	/** @var array default configuration */
	private $options = [
		'cookie_lifetime' => 0,   // until the browser is closed
		'gc_maxlifetime' => self::DEFAULT_FILE_LIFETIME, // 3 hours
	];

	/** @var IRequest */
	private $request;

	/** @var IResponse */
	private $response;

	/** @var \SessionHandlerInterface */
	private $handler;

	/** @var bool */
	private $readAndClose = false;


	public function __construct(IRequest $request, IResponse $response)
	{
		$this->request = $request;
		$this->response = $response;
		$this->options['cookie_path'] = &$this->response->cookiePath;
		$this->options['cookie_domain'] = &$this->response->cookieDomain;
		$this->options['cookie_secure'] = &$this->response->cookieSecure;
	}


	/**
	 * Starts and initializes session data.
	 * @throws Nette\InvalidStateException
	 */
	public function start(): void
	{
		if (session_status() === PHP_SESSION_ACTIVE) {
			if (!$this->started) {
				$this->configure(self::SECURITY_OPTIONS);
				$this->initialize();
			}
			return;
		}

		$this->configure(self::SECURITY_OPTIONS + $this->options);

		if (!session_id()) { // session is started for first time
			$id = $this->request->getCookie(session_name());
			$id = is_string($id) && preg_match('#^[0-9a-zA-Z,-]{22,256}$#Di', $id)
				? $id
				: session_create_id();
			session_id($id); // causes resend of a cookie
		}

		try {
			// session_start returns false on failure only sometimes
			Nette\Utils\Callback::invokeSafe('session_start', [['read_and_close' => $this->readAndClose]], function (string $message) use (&$e): void {
				$e = new Nette\InvalidStateException($message);
			});
		} catch (\Exception $e) {
		}

		if ($e) {
			@session_write_close(); // this is needed
			throw $e;
		}

		$this->initialize();
	}


	private function initialize(): void
	{
		$this->started = true;

		/* structure:
			__NF: Data, Meta, Time
				DATA: section->variable = data
				META: section->variable = Timestamp
		*/
		$nf = &$_SESSION['__NF'];

		if (!is_array($nf)) {
			$nf = [];
		}

		// regenerate empty session
		if (empty($nf['Time'])) {
			$nf['Time'] = time();
			if ($this->request->getCookie(session_name())) { // ensures that the session was created in strict mode (see use_strict_mode)
				$this->regenerateId();
			}
		}

		// expire section variables
		$now = time();
		foreach ($nf['META'] ?? [] as $section => $metadata) {
			foreach ($metadata ?? [] as $variable => $value) {
				if (!empty($value['T']) && $now > $value['T']) {
					if ($variable === '') { // expire whole section
						unset($nf['META'][$section], $nf['DATA'][$section]);
						continue 2;
					}
					unset($nf['META'][$section][$variable], $nf['DATA'][$section][$variable]);
				}
			}
		}

		register_shutdown_function([$this, 'clean']);
	}


	/**
	 * Has been session started?
	 */
	public function isStarted(): bool
	{
		return $this->started && session_status() === PHP_SESSION_ACTIVE;
	}


	/**
	 * Ends the current session and store session data.
	 */
	public function close(): void
	{
		if (session_status() === PHP_SESSION_ACTIVE) {
			$this->clean();
			session_write_close();
			$this->started = false;
		}
	}


	/**
	 * Destroys all data registered to a session.
	 */
	public function destroy(): void
	{
		if (!session_status() === PHP_SESSION_ACTIVE) {
			throw new Nette\InvalidStateException('Session is not started.');
		}

		session_destroy();
		$_SESSION = null;
		$this->started = false;
		if (!$this->response->isSent()) {
			$params = session_get_cookie_params();
			$this->response->deleteCookie(session_name(), $params['path'], $params['domain'], $params['secure']);
		}
	}


	/**
	 * Does session exists for the current request?
	 */
	public function exists(): bool
	{
		return session_status() === PHP_SESSION_ACTIVE || $this->request->getCookie($this->getName()) !== null;
	}


	/**
	 * Regenerates the session ID.
	 * @throws Nette\InvalidStateException
	 */
	public function regenerateId(): void
	{
		if ($this->regenerated) {
			return;
		}
		if (session_status() === PHP_SESSION_ACTIVE) {
			if (headers_sent($file, $line)) {
				throw new Nette\InvalidStateException('Cannot regenerate session ID after HTTP headers have been sent' . ($file ? " (output started at $file:$line)." : '.'));
			}
			session_regenerate_id(true);
		} else {
			session_id(session_create_id());
		}
		$this->regenerated = true;
	}


	/**
	 * Returns the current session ID. Don't make dependencies, can be changed for each request.
	 */
	public function getId(): string
	{
		return session_id();
	}


	/**
	 * Sets the session name to a specified one.
	 * @return static
	 */
	public function setName(string $name)
	{
		if (!preg_match('#[^0-9.][^.]*$#DA', $name)) {
			throw new Nette\InvalidArgumentException('Session name cannot contain dot.');
		}

		session_name($name);
		return $this->setOptions([
			'name' => $name,
		]);
	}


	/**
	 * Gets the session name.
	 */
	public function getName(): string
	{
		return $this->options['name'] ?? session_name();
	}


	/********************* sections management ****************d*g**/


	/**
	 * Returns specified session section.
	 * @throws Nette\InvalidArgumentException
	 */
	public function getSection(string $section, string $class = SessionSection::class): SessionSection
	{
		return new $class($this, $section);
	}


	/**
	 * Checks if a session section exist and is not empty.
	 */
	public function hasSection(string $section): bool
	{
		if ($this->exists() && !$this->started) {
			$this->start();
		}

		return !empty($_SESSION['__NF']['DATA'][$section]);
	}


	/**
	 * Iteration over all sections.
	 */
	public function getIterator(): \Iterator
	{
		if ($this->exists() && !$this->started) {
			$this->start();
		}

		return new \ArrayIterator(array_keys($_SESSION['__NF']['DATA'] ?? []));
	}


	/**
	 * Cleans and minimizes meta structures. This method is called automatically on shutdown, do not call it directly.
	 * @internal
	 */
	public function clean(): void
	{
		if (!session_status() === PHP_SESSION_ACTIVE || empty($_SESSION)) {
			return;
		}

		$nf = &$_SESSION['__NF'];
		foreach ($nf['META'] ?? [] as $name => $foo) {
			if (empty($nf['META'][$name])) {
				unset($nf['META'][$name]);
			}
		}
	}


	/********************* configuration ****************d*g**/


	/**
	 * Sets session options.
	 * @return static
	 * @throws Nette\NotSupportedException
	 * @throws Nette\InvalidStateException
	 */
	public function setOptions(array $options)
	{
		$normalized = [];
		foreach ($options as $key => $value) {
			if (!strncmp($key, 'session.', 8)) { // back compatibility
				$key = substr($key, 8);
			}
			$key = strtolower(preg_replace('#(.)(?=[A-Z])#', '$1_', $key)); // camelCase -> snake_case
			$normalized[$key] = $value;
		}
		if (!empty($normalized['read_and_close'])) {
			if (session_status() === PHP_SESSION_ACTIVE) {
				throw new Nette\InvalidStateException('Cannot configure "read_and_close" for already started session.');
			}
			$this->readAndClose = (bool) $normalized['read_and_close'];
			unset($normalized['read_and_close']);
		}
		if (session_status() === PHP_SESSION_ACTIVE) {
			$this->configure($normalized);
		}
		$this->options = $normalized + $this->options;
		if (!empty($normalized['auto_start'])) {
			$this->start();
		}
		return $this;
	}


	/**
	 * Returns all session options.
	 */
	public function getOptions(): array
	{
		return $this->options;
	}


	/**
	 * Configures session environment.
	 */
	private function configure(array $config): void
	{
		$special = ['cache_expire' => 1, 'cache_limiter' => 1, 'save_path' => 1, 'name' => 1];
		$cookie = $origCookie = session_get_cookie_params();
		$allowed = ini_get_all('session', false) + ['session.cookie_samesite' => 1]; // for PHP < 7.3

		foreach ($config as $key => $value) {
			if (!isset($allowed["session.$key"])) {
				$hint = substr((string) Nette\Utils\ObjectHelpers::getSuggestion(array_keys($allowed), "session.$key"), 8);
				[$altKey, $altHint] = array_map(function ($s) {
					return preg_replace_callback('#_(.)#', function ($m) { return strtoupper($m[1]); }, $s); // snake_case -> camelCase
				}, [$key, (string) $hint]);
				throw new Nette\InvalidStateException("Invalid session configuration option '$key' or '$altKey'" . ($hint ? ", did you mean '$hint' or '$altHint'?" : '.'));

			} elseif ($value === null || ini_get("session.$key") == $value) { // intentionally ==
				continue;

			} elseif (strncmp($key, 'cookie_', 7) === 0) {
				$cookie[substr($key, 7)] = $value;

			} else {
				if (session_status() === PHP_SESSION_ACTIVE) {
					throw new Nette\InvalidStateException("Unable to set 'session.$key' to value '$value' when session has been started" . ($this->started ? '.' : ' by session.auto_start or session_start().'));
				}
				if (isset($special[$key])) {
					$key = "session_$key";
					$key($value);

				} elseif (function_exists('ini_set')) {
					ini_set("session.$key", (string) $value);

				} elseif (ini_get("session.$key") != $value) { // intentionally !=
					throw new Nette\NotSupportedException("Unable to set 'session.$key' to '$value' because function ini_set() is disabled.");
				}
			}
		}

		if ($cookie !== $origCookie) {
			if (PHP_VERSION_ID >= 70300) {
				@session_set_cookie_params($cookie); // @ may trigger warning when session is active since PHP 7.2
			} else {
				@session_set_cookie_params( // @ may trigger warning when session is active since PHP 7.2
					$cookie['lifetime'],
					$cookie['path'] . (isset($cookie['samesite']) ? '; SameSite=' . $cookie['samesite'] : ''),
					$cookie['domain'],
					$cookie['secure'],
					$cookie['httponly']
				);
			}
			if (session_status() === PHP_SESSION_ACTIVE) {
				$this->sendCookie();
			}
		}

		if ($this->handler) {
			session_set_save_handler($this->handler);
		}
	}


	/**
	 * Sets the amount of time (like '20 minutes') allowed between requests before the session will be terminated,
	 * null means "until the browser is closed".
	 * @return static
	 */
	public function setExpiration(?string $time)
	{
		if (empty($time)) {
			return $this->setOptions([
				'gc_maxlifetime' => self::DEFAULT_FILE_LIFETIME,
				'cookie_lifetime' => 0,
			]);

		} else {
			$time = Nette\Utils\DateTime::from($time)->format('U') - time();
			return $this->setOptions([
				'gc_maxlifetime' => $time,
				'cookie_lifetime' => $time,
			]);
		}
	}


	/**
	 * Sets the session cookie parameters.
	 * @return static
	 */
	public function setCookieParameters(string $path, string $domain = null, bool $secure = null, string $samesite = null)
	{
		return $this->setOptions([
			'cookie_path' => $path,
			'cookie_domain' => $domain,
			'cookie_secure' => $secure,
			'cookie_samesite' => $samesite,
		]);
	}


	/**
	 * @deprecated
	 */
	public function getCookieParameters(): array
	{
		return session_get_cookie_params();
	}


	/**
	 * Sets path of the directory used to save session data.
	 * @return static
	 */
	public function setSavePath(string $path)
	{
		return $this->setOptions([
			'save_path' => $path,
		]);
	}


	/**
	 * Sets user session handler.
	 * @return static
	 */
	public function setHandler(\SessionHandlerInterface $handler)
	{
		if ($this->started) {
			throw new Nette\InvalidStateException('Unable to set handler when session has been started.');
		}
		$this->handler = $handler;
		return $this;
	}


	/**
	 * Sends the session cookies.
	 */
	private function sendCookie(): void
	{
		$cookie = session_get_cookie_params();
		$this->response->setCookie(
			session_name(), session_id(),
			$cookie['lifetime'] ? $cookie['lifetime'] + time() : 0,
			$cookie['path'], $cookie['domain'], $cookie['secure'], $cookie['httponly'], $cookie['samesite'] ?? null
		);
	}
}
