class ExtensionVersion

final class ExtensionVersion {
    
    /**
     * The '8.x-' prefix is used on contrib extension version numbers.
     *
     * @var string
     */
    const CORE_PREFIX = '8.x-';
    
    /**
     * The major version.
     *
     * @var string
     */
    protected $majorVersion;
    
    /**
     * The minor version.
     *
     * @var string|null
     */
    protected $minorVersion;
    
    /**
     * The version extra string.
     *
     * For example, if the extension version is '2.0.3-alpha1', then the version
     * extra string is 'alpha1'.
     *
     * @var string|null
     */
    protected $versionExtra;
    
    /**
     * Constructs an extension version object from a version string.
     *
     * @param string $version_string
     *   The version string.
     *
     * @return \Drupal\Core\Extension\ExtensionVersion
     *   The extension version instance.
     */
    public static function createFromVersionString(string $version_string) : ExtensionVersion {
        $original_version = $version_string;
        if (strpos($version_string, static::CORE_PREFIX) === 0 && $version_string !== '8.x-dev') {
            $version_string = preg_replace('/8\\.x-/', '', $version_string, 1);
        }
        else {
            // Ensure the version string has no unsupported core prefixes.
            $dot_x_position = strpos($version_string, '.x-');
            if ($dot_x_position === 1 || $dot_x_position === 2) {
                $after_core_prefix = explode('.x-', $version_string)[1];
                if ($after_core_prefix !== 'dev') {
                    throw new \UnexpectedValueException("Unexpected version core prefix in {$version_string}. The only core prefix expected in \\Drupal\\Core\\Extension\\ExtensionVersion is: 8.x-");
                }
            }
        }
        $version_parts = explode('.', $version_string);
        $major_version = $version_parts[0];
        $version_parts_count = count($version_parts);
        if ($version_parts_count === 2) {
            $minor_version = NULL;
        }
        elseif ($version_parts_count === 3) {
            $minor_version = $version_parts[1];
        }
        $last_part_split = explode('-', $version_parts[count($version_parts) - 1]);
        $version_extra = count($last_part_split) === 1 ? NULL : $last_part_split[1];
        if ($version_parts_count > 3 || $version_parts_count < 2 || !is_numeric($major_version) || $version_parts_count === 3 && !is_numeric($version_parts[1]) || !is_numeric($last_part_split[0]) && $last_part_split !== 'x' && $version_extra !== 'dev') {
            throw new \UnexpectedValueException("Unexpected version number in: {$original_version}");
        }
        return new static($major_version, $minor_version, $version_extra);
    }
    
    /**
     * Constructs an ExtensionVersion object.
     *
     * @param string $major_version
     *   The major version.
     * @param string|null $minor_version
     *   The minor version.
     * @param string|null $version_extra
     *   The extra version string.
     */
    private function __construct(string $major_version, ?string $minor_version, ?string $version_extra) {
        $this->majorVersion = $major_version;
        $this->minorVersion = $minor_version;
        $this->versionExtra = $version_extra;
    }
    
    /**
     * Constructs an ExtensionVersion version object from a support branch.
     *
     * This can be used to determine the major version of the branch.
     * ::getVersionExtra() will always return NULL for branches.
     *
     * @param string $branch
     *   The support branch.
     *
     * @return \Drupal\Core\Extension\ExtensionVersion
     *   The ExtensionVersion instance.
     */
    public static function createFromSupportBranch(string $branch) : ExtensionVersion {
        if (substr($branch, -1) !== '.') {
            throw new \UnexpectedValueException("Invalid support branch: {$branch}");
        }
        return static::createFromVersionString($branch . '0');
    }
    
    /**
     * Gets the major version.
     *
     * @return string
     *   The major version.
     */
    public function getMajorVersion() : string {
        return $this->majorVersion;
    }
    
    /**
     * Gets the minor version.
     *
     * @return string|null
     *   The minor version.
     */
    public function getMinorVersion() : ?string {
        return $this->minorVersion;
    }
    
    /**
     * Gets the version extra string at the end of the version number.
     *
     * @return string|null
     *   The version extra string if available, or otherwise NULL.
     */
    public function getVersionExtra() : ?string {
        return $this->versionExtra;
    }

}