<?php
/**
 * Shaarli (application) utilities
 */
class ApplicationUtils
{
    private static $GIT_URL = 'https://raw.githubusercontent.com/shaarli/Shaarli';
    private static $GIT_BRANCH = 'master';
    private static $VERSION_FILE = 'shaarli_version.php';
    private static $VERSION_START_TAG = '<?php /* ';
    private static $VERSION_END_TAG = ' */ ?>';

    /**
     * Gets the latest version code from the Git repository
     *
     * The code is read from the raw content of the version file on the Git server.
     *
     * @return mixed the version code from the repository if available, else 'false'
     */
    public static function getLatestGitVersionCode($url, $timeout=2)
    {
        list($headers, $data) = get_http_url($url, $timeout);

        if (strpos($headers[0], '200 OK') === false) {
            error_log('Failed to retrieve ' . $url);
            return false;
        }

        return str_replace(
            array(self::$VERSION_START_TAG, self::$VERSION_END_TAG, PHP_EOL),
            array('', '', ''),
            $data
        );
    }

    /**
     * Checks if a new Shaarli version has been published on the Git repository
     *
     * Updates checks are run periodically, according to the following criteria:
     * - the update checks are enabled (install, global config);
     * - the user is logged in (or this is an open instance);
     * - the last check is older than a given interval;
     * - the check is non-blocking if the HTTPS connection to Git fails;
     * - in case of failure, the update file's modification date is updated,
     *   to avoid intempestive connection attempts.
     *
     * @param string $currentVersion the current version code
     * @param string $updateFile     the file where to store the latest version code
     * @param int    $checkInterval  the minimum interval between update checks (in seconds
     * @param bool   $enableCheck    whether to check for new versions
     * @param bool   $isLoggedIn     whether the user is logged in
     *
     * @return mixed the new version code if available and greater, else 'false'
     */
    public static function checkUpdate(
        $currentVersion, $updateFile, $checkInterval, $enableCheck, $isLoggedIn)
    {
        if (! $isLoggedIn) {
            // Do not check versions for visitors
            return false;
        }

        if (empty($enableCheck)) {
            // Do not check if the user doesn't want to
            return false;
        }

        if (is_file($updateFile) && (filemtime($updateFile) > time() - $checkInterval)) {
            // Shaarli has checked for updates recently - skip HTTP query
            $latestKnownVersion = file_get_contents($updateFile);

            if (version_compare($latestKnownVersion, $currentVersion) == 1) {
                return $latestKnownVersion;
            }
            return false;
        }

        // Late Static Binding allows overriding within tests
        // See http://php.net/manual/en/language.oop5.late-static-bindings.php
        $latestVersion = static::getLatestGitVersionCode(
            self::$GIT_URL . '/' . self::$GIT_BRANCH . '/' . self::$VERSION_FILE
        );

        if (! $latestVersion) {
            // Only update the file's modification date
            file_put_contents($updateFile, $currentVersion);
            return false;
        }

        // Update the file's content and modification date
        file_put_contents($updateFile, $latestVersion);

        if (version_compare($latestVersion, $currentVersion) == 1) {
            return $latestVersion;
        }

        return false;
    }

    /**
     * Checks the PHP version to ensure Shaarli can run
     *
     * @param string $minVersion minimum PHP required version
     * @param string $curVersion current PHP version (use PHP_VERSION)
     *
     * @throws Exception the PHP version is not supported
     */
    public static function checkPHPVersion($minVersion, $curVersion)
    {
        if (version_compare($curVersion, $minVersion) < 0) {
            throw new Exception(
                'Your PHP version is obsolete!'
                .' Shaarli requires at least PHP '.$minVersion.', and thus cannot run.'
                .' Your PHP version has known security vulnerabilities and should be'
                .' updated as soon as possible.'
            );
        }
    }

    /**
     * Checks Shaarli has the proper access permissions to its resources
     *
     * @param array $globalConfig The $GLOBALS['config'] array
     *
     * @return array A list of the detected configuration issues
     */
    public static function checkResourcePermissions($globalConfig)
    {
        $errors = array();

        // Check script and template directories are readable
        foreach (array(
            'application',
            'inc',
            'plugins',
            $globalConfig['RAINTPL_TPL']
        ) as $path) {
            if (! is_readable(realpath($path))) {
                $errors[] = '"'.$path.'" directory is not readable';
            }
        }

        // Check cache and data directories are readable and writeable
        foreach (array(
            $globalConfig['CACHEDIR'],
            $globalConfig['DATADIR'],
            $globalConfig['PAGECACHE'],
            $globalConfig['RAINTPL_TMP']
        ) as $path) {
            if (! is_readable(realpath($path))) {
                $errors[] = '"'.$path.'" directory is not readable';
            }
            if (! is_writable(realpath($path))) {
                $errors[] = '"'.$path.'" directory is not writable';
            }
        }

        // Check configuration files are readable and writeable
        foreach (array(
            $globalConfig['CONFIG_FILE'],
            $globalConfig['DATASTORE'],
            $globalConfig['IPBANS_FILENAME'],
            $globalConfig['LOG_FILE'],
            $globalConfig['UPDATECHECK_FILENAME']
        ) as $path) {
            if (! is_file(realpath($path))) {
                # the file may not exist yet
                continue;
            }

            if (! is_readable(realpath($path))) {
                $errors[] = '"'.$path.'" file is not readable';
            }
            if (! is_writable(realpath($path))) {
                $errors[] = '"'.$path.'" file is not writable';
            }
        }

        return $errors;
    }
}