public static TokenCredentialOptions ParseAuthenticationString()

in src/Microsoft.Azure.WebJobs.Logging.ApplicationInsights/TokenCredentialOptions.cs [39:107]
57 lines of code
13 McCabe index (conditional complexity)

        public static TokenCredentialOptions ParseAuthenticationString(string applicationInsightsAuthenticationString)
        {
            if (string.IsNullOrWhiteSpace(applicationInsightsAuthenticationString))
            {
                throw new ArgumentNullException(nameof(applicationInsightsAuthenticationString), "Authentication string cannot be null or empty.");
            }

            var tokenCredentialOptions = new TokenCredentialOptions();
            bool isValidConfiguration = false;
            foreach ((int, int) split in Tokenize(applicationInsightsAuthenticationString))
            {
                (int start, int length) = split;

                // Trim whitespace from start
                while (length > 0 && char.IsWhiteSpace(applicationInsightsAuthenticationString[start]))
                {
                    start++;
                    length--;
                }

                // Ignore (allow) empty tokens.
                if (length == 0)
                {
                    continue;
                }

                // Find key-value separator.
                int indexOfEquals = applicationInsightsAuthenticationString.IndexOf('=', start, length);
                if (indexOfEquals < 0)
                {
                    continue;
                }

                // Extract key
                int keyLength = indexOfEquals - start;
                string key = applicationInsightsAuthenticationString.Substring(start, keyLength).TrimEnd();
                if (key.Length == 0)
                {
                    // Key is blank
                    continue;
                }

                if (key.Equals(AuthAuthorizationKey, StringComparison.OrdinalIgnoreCase))
                {
                    if (!applicationInsightsAuthenticationString.Substring(indexOfEquals + 1, length - keyLength - 1).Trim().Equals(AuthToken, StringComparison.OrdinalIgnoreCase))
                    { 
                        throw new InvalidCredentialException("Credential supplied is not valid for the authorization mechanism being used in ApplicationInsights.");
                    }
                    isValidConfiguration = true;
                    continue;
                }
                if (key.Equals(AuthClientIdKey, StringComparison.OrdinalIgnoreCase))
                {
                    string clientId = applicationInsightsAuthenticationString.Substring(indexOfEquals + 1, length - keyLength - 1).Trim();
                    if (!Guid.TryParse(clientId, out Guid clientIdGuid))
                    {
                        throw new FormatException($"The Application Insights AuthenticationString {AuthClientIdKey} is not a valid GUID.");
                    }
                    tokenCredentialOptions.ClientId = clientId;
                    continue;
                }
            }     
            // Throw if the Authorization key is not present in the authentication string
            if (!isValidConfiguration)
            {
                throw new InvalidCredentialException("Authorization key is missing in the authentication string for ApplicationInsights.");
            }
            return tokenCredentialOptions;
        }