/// <remarks>
/// Based on the C# sample from: https://developers.google.com/maps/documentation/business/webservices
/// </remarks>
internal Uri Sign(Uri uri)
{
if (uri == null)
{
throw new ArgumentNullException(nameof(uri));
}
if (ClientId == null)
{
throw new ArgumentNullException("userID");
}
if (string.IsNullOrWhiteSpace(SigningKey))
{
throw new ArgumentException("Invalid signing key.");
}
if (!ClientId.StartsWith("gme-"))
{
throw new ArgumentException("A user ID must start with 'gme-'.");
}
var urlSegmentToSign = uri.LocalPath + uri.Query + "&client=" + ClientId;
if (!string.IsNullOrWhiteSpace(Channel))
{
urlSegmentToSign += "&channel=" + Channel;
}
byte[] privateKey = FromBase64UrlString(SigningKey);
byte[] signature;
using (var algorithm = new HMACSHA1(privateKey))
{
signature = algorithm.ComputeHash(Encoding.ASCII.GetBytes(urlSegmentToSign));
}
return(new Uri(uri.Scheme + "://" + uri.Host + urlSegmentToSign + "&signature=" + ToBase64UrlString(signature)));
}