UrlSegmentApiVersionStripMiddleware

/// <summary>
/// Rewrite URL API version segment if it exists
/// </summary>
public class UrlSegmentApiVersionStripMiddleware {
    private static readonly string DEFAULT_API_VERSION_PREFIX = "v";

    private readonly string _apiVersionVersion;
    private readonly RequestDelegate _next;


    /// <summary>
    /// Constructor
    /// </summary>
    /// <param name="next">Next request delegate</param>
    /// <param name="apiVersionPrefix">API version prefix (optional)</param>
    public UrlSegmentApiVersionStripMiddleware(RequestDelegate next, string apiVersionPrefix = null) {
        if (next == null) {
            throw new ArgumentNullException(nameof(next));
        }
        _apiVersionVersion = Regex.Escape(apiVersionPrefix ?? DEFAULT_API_VERSION_PREFIX);
        _next = next;
    }

    public Task InvokeAsync(HttpContext httpContext) {
        // https://github.com/Microsoft/aspnet-api-versioning/wiki/Version-Format
        // [Version Group.]<Major>.<Minor>[-Status]
        // <Version Group>[.<Major>[.Minor]][-Status]
        var urlSegmentApiVersionRegexes = new Regex[] {
            new Regex($@"{_apiVersionVersion}(?<apiVersion>(?:(?<group>\d{4}-\d{2}-\d{2})\.)?(?<major>\d+)(?:\.(?<minor>\d+))?(?:-(?<status>\w+))?)/?$"),
            new Regex($@"{_apiVersionVersion}(?<apiVersion>(?<group>\d{4}-\d{2}-\d{2})(?:(?:\.(?<major>\d+)(?:\.(?<minor>\d+))))?(?:-(?<status>\w+))?)  /?$"),
        };
        var uri = new Uri(httpContext.Request.Path.ToUriComponent());
        var apiVersionSegment = uri.Segments
            .Where(segment => urlSegmentApiVersionRegexes.Any(regex => regex.Match(segment).Success))
            .FirstOrDefault();
        if (apiVersionSegment != null) {
            var newPath = string.Join("", uri.Segments.Where(segment => segment != apiVersionSegment));
            httpContext.Request.Path = new PathString(newPath);
            var match = urlSegmentApiVersionRegexes.Select(regex => regex.Match(apiVersionSegment))
                .Where(regex => regex.Success)
                .First();
            var rawApiVersion = match.Groups["apiVersion"].Value;
            var feature = httpContext.Features.Get<IApiVersioningFeature>();
            feature.RawRequestedApiVersion = rawApiVersion;
        }
        return _next(httpContext);
    }
}