Amazon.S3.Util.AmazonS3Uri.AmazonS3Uri C# (CSharp) Method

        public AmazonS3Uri(Uri uri)
        {
            if (uri == null)
                throw new ArgumentNullException("uri");

            if (string.IsNullOrEmpty(uri.Host))
                throw new ArgumentException("Invalid URI - no hostname present");

            var match = new Regex(EndpointPattern).Match(uri.Host);
            if (!match.Success)
                throw new ArgumentException("Invalid S3 URI - hostname does not appear to be a valid S3 endpoint");

            // for host style urls:
            //   group 0 is bucketname plus 's3' prefix and possible region code
            //   group 1 is bucket name
            //   group 2 will be region or 'amazonaws' if US Classic region
            // for path style urls:
            //   group 0 will be s3 prefix plus possible region code
            //   group 1 will be empty
            //   group 2 will be region or 'amazonaws' if US Classic region
            var bucketNameGroup = match.Groups[1];
            if (string.IsNullOrEmpty(bucketNameGroup.Value))
            {
                // no bucket name in the authority, parse it from the path
                this.IsPathStyle = true;

                // grab the encoded path so we don't run afoul of '/'s in the bucket name
                var path = uri.AbsolutePath;
                if (path.Equals("/"))
                {
                    this.Bucket = null;
                    this.Key = null;
                }
                else
                {
                    var index = path.IndexOf('/', 1);
                    if (index == -1)
                    {
                        // https://s3.amazonaws.com/bucket
                        this.Bucket = Decode(path.Substring(1));
                        this.Key = null;
                    }
                    else if (index == (path.Length - 1))
                    {
                        // https://s3.amazonaws.com/bucket/
                        this.Bucket = Decode(path.Substring(1, index)).TrimEnd('/');
                        this.Key = null;
                    }
                    else
                    {
                        // https://s3.amazonaws.com/bucket/key
                        this.Bucket = Decode(path.Substring(1, index)).TrimEnd('/');
                        this.Key = Decode(path.Substring(index + 1));
                    }
                }
            }
            else
            {
                // bucket name in the host, path is the object key
                this.IsPathStyle = false;

                // remove any trailing '.' from the prefix to get the bucket name
                this.Bucket = bucketNameGroup.Value.TrimEnd('.');
                this.Key = uri.AbsolutePath.Equals("/") ? null : uri.AbsolutePath.Substring(1);
            }

            if (match.Groups.Count > 2)
            {
                // US 'classic' urls will not have a region code in the endpoint
                var regionGroupValue = match.Groups[2].Value;
                if (regionGroupValue.Equals("amazonaws", StringComparison.Ordinal)
                    || regionGroupValue.Equals("external-1", StringComparison.Ordinal))
                    this.Region = RegionEndpoint.USEast1;
                else
                {
                    try
                    {
                        this.Region = RegionEndpoint.GetBySystemName(regionGroupValue);
                    }
                    catch (Amazon.Runtime.AmazonClientException)
                    {
                        // in cases where endpoints such as "s3-accelerate" matches, 
                        // just set the region to null and move on.
                        this.Region = null;
                    }
                }
                    
            }
        }