<?php

declare(strict_types=1);

namespace SimpleSAML\Utils;

use SimpleSAML\Configuration;
use SimpleSAML\Error;

/**
 * System-related utility methods.
 *
 * @package SimpleSAMLphp
 */

class System
{
    public const WINDOWS = 1;
    public const LINUX = 2;
    public const OSX = 3;
    public const HPUX = 4;
    public const UNIX = 5;
    public const BSD = 6;
    public const IRIX = 7;
    public const SUNOS = 8;


    /**
     * This function returns the Operating System we are running on.
     *
     * @return int|false A predefined constant identifying the OS we are running on.
     *                   False if we are unable to determine it.
     *
     */
    public function getOS()
    {
        if (stristr(PHP_OS, 'LINUX')) {
            return self::LINUX;
        }
        if (stristr(PHP_OS, 'DARWIN')) {
            return self::OSX;
        }
        if (stristr(PHP_OS, 'WIN')) {
            return self::WINDOWS;
        }
        if (stristr(PHP_OS, 'BSD')) {
            return self::BSD;
        }
        if (stristr(PHP_OS, 'UNIX')) {
            return self::UNIX;
        }
        if (stristr(PHP_OS, 'HP-UX')) {
            return self::HPUX;
        }
        if (stristr(PHP_OS, 'IRIX')) {
            return self::IRIX;
        }
        if (stristr(PHP_OS, 'SUNOS')) {
            return self::SUNOS;
        }
        return false;
    }


    /**
     * This function retrieves the path to a directory where temporary files can be saved.
     *
     * @return string Path to a temporary directory, without a trailing directory separator.
     * @throws Error\Exception If the temporary directory cannot be created or it exists and cannot be written
     * to by the current user.
     *
     */
    public function getTempDir(): string
    {
        $globalConfig = Configuration::getInstance();

        $tempDir = rtrim(
            $globalConfig->getOptionalString(
                'tempdir',
                sys_get_temp_dir() . DIRECTORY_SEPARATOR . 'simplesaml'
            ),
            DIRECTORY_SEPARATOR
        );

        /**
         * If the temporary directory does not exist then attempt to create it. If the temporary directory
         * already exists then verify the current user can write to it. Otherwise, throw an error.
         */
        if (!is_dir($tempDir)) {
            if (!mkdir($tempDir, 0700, true)) {
                $error = error_get_last();
                throw new Error\Exception(
                    'Error creating temporary directory "' . $tempDir . '": ' .
                    (is_array($error) ? $error['message'] : 'no error available')
                );
            }
        } elseif (!is_writable($tempDir)) {
            throw new Error\Exception(sprintf(
                'Temporary directory "%s" cannot be written to by the current user "%s".',
                $tempDir,
                get_current_user(),
            ));
        }

        return $tempDir;
    }


    /**
     * Resolve a (possibly) relative path from the given base path.
     *
     * A path which starts with a stream wrapper pattern (e.g. s3://) will not be touched
     * and returned as is - regardless of the value given as base path.
     * If it starts with a '/' it is assumed to be absolute, all others are assumed to be
     * relative. The default base path is the root of the SimpleSAMLphp installation.
     *
     * @param string      $path The path we should resolve.
     * @param string|null $base The base path, where we should search for $path from. Default value is the root of the
     *     SimpleSAMLphp installation.
     *
     * @return string An absolute path referring to $path.
     *
     */
    public function resolvePath(string $path, string $base = null): string
    {
        if ($base === null) {
            $config = Configuration::getInstance();
            $base = $config->getBaseDir();
        }

        // normalise directory separator
        $base = str_replace('\\', '/', $base);
        $path = str_replace('\\', '/', $path);

        // remove trailing slashes
        $base = rtrim($base, '/');
        $path = rtrim($path, '/');

        // check for absolute path
        if (substr($path, 0, 1) === '/') {
            // absolute path. */
            $ret = '/';
        } elseif ($this->pathContainsDriveLetter($path)) {
            $ret = '';
        } else {
            // path relative to base
            $ret = $base;
        }

        if ($this->pathContainsStreamWrapper($path)) {
            $ret = $path;
        } else {
            $path = explode('/', $path);
            foreach ($path as $d) {
                if ($d === '.') {
                    continue;
                } elseif ($d === '..') {
                    $ret = dirname($ret);
                } else {
                    if ($ret && substr($ret, -1) !== '/') {
                        $ret .= '/';
                    }
                    $ret .= $d;
                }
            }
        }

        return $ret;
    }


    /**
     * Atomically write a file.
     *
     * This is a helper function for writing data atomically to a file. It does this by writing the file data to a
     * temporary file, then renaming it to the required file name.
     *
     * @param string $filename The path to the file we want to write to.
     * @param string $data The data we should write to the file.
     * @param int    $mode The permissions to apply to the file. Defaults to 0600.
     *
     *
     * @throws \InvalidArgumentException If any of the input parameters doesn't have the proper types.
     * @throws Error\Exception If the file cannot be saved, permissions cannot be changed or it is not
     *     possible to write to the target file.
     *
     */
    public function writeFile(string $filename, string $data, int $mode = 0600): void
    {
        $tmpFile = $this->getTempDir() . DIRECTORY_SEPARATOR . rand();

        $res = @file_put_contents($tmpFile, $data);
        if ($res === false) {
            /** @var array|null $error */
            $error = error_get_last();
            throw new Error\Exception(
                'Error saving file "' . $tmpFile . '": ' .
                (is_array($error) ? $error['message'] : 'no error available')
            );
        }

        if ($this->getOS() !== self::WINDOWS) {
            if (!chmod($tmpFile, $mode)) {
                unlink($tmpFile);
                /** @var array|null $error */
                $error = error_get_last();
                throw new Error\Exception(
                    'Error changing file mode of "' . $tmpFile . '": ' .
                    (is_array($error) ? $error['message'] : 'no error available')
                );
            }
        }

        if (!rename($tmpFile, $filename)) {
            unlink($tmpFile);
            /** @var array|null $error */
            $error = error_get_last();
            throw new Error\Exception(
                'Error moving "' . $tmpFile . '" to "' . $filename . '": ' .
                (is_array($error) ? $error['message'] : 'no error available')
            );
        }

        if (function_exists('opcache_invalidate')) {
            opcache_invalidate($filename);
        }
    }


    /**
     * Check if the supplied path is an absolute path.
     *
     * @param string $path
     *
     * @return bool
     */
    public function isAbsolutePath(string $path): bool
    {
        return (0 === strpos($path, '/') || $this->pathContainsDriveLetter($path));
    }


    /**
     * Check if the supplied path contains a Windows-style drive letter.
     *
     * @param string $path
     *
     * @return bool
     */
    private function pathContainsDriveLetter(string $path): bool
    {
        $letterAsciiValue = ord(strtoupper(substr($path, 0, 1)));
        return substr($path, 1, 1) === ':'
                && $letterAsciiValue >= 65 && $letterAsciiValue <= 90;
    }

    /**
     * Check if the supplied path contains a stream wrapper
     * @param string $path
     * @return bool
     */
    private function pathContainsStreamWrapper(string $path): bool
    {
        return preg_match('/^[\w\d]*:\/{2}/', $path) === 1;
    }
}
