/// <summary>
/// Create a new response.
/// </summary>
/// <param name="code">Response status code</param>
/// <param name="reason">Reason to why the status code was used.</param>
/// <returns>A Created response.</returns>
/// <exception cref="InvalidOperationException">Provisional responses is only valid for INVITE method.</exception>
public IResponse CreateResponse(StatusCode code, string reason)
{
if (StatusCodeHelper.Is1xx(code) && Method != "INVITE")
{
throw new InvalidOperationException("Provisional responses is only valid for INVITE method.");
}
var response = new Response(SipVersion, code, reason);
// When a 100 (Trying) response is generated, any Timestamp header field
// present in the request MUST be copied into this 100 (Trying)
// response. If there is a delay in generating the response, the UAS
// SHOULD add a delay value into the Timestamp value in the response.
// This value MUST contain the difference between the time of sending of
// the response and receipt of the request, measured in seconds.
if (StatusCodeHelper.Is1xx(code) && Headers["Timestamp"] != null)
{
response.Headers.Add("Timestamp", Headers["Timestamp"]);
}
// The From field of the response MUST equal the From header field of
// the request. The Call-ID header field of the response MUST equal the
// Call-ID header field of the request. The CSeq header field of the
// response MUST equal the CSeq field of the request. The Via header
// field values in the response MUST equal the Via header field values
// in the request and MUST maintain the same ordering.
response.From = From;
response.CallId = CallId;
response.CSeq = CSeq;
response.Via = (Via)Via.Clone();
// If a request contained a To tag in the request, the To header field
// in the response MUST equal that of the request. However, if the To
// header field in the request did not contain a tag, the URI in the To
// header field in the response MUST equal the URI in the To header
// field; additionally, the UAS MUST add a tag to the To header field in
// the response (with the exception of the 100 (Trying) response, in
// which a tag MAY be present). This serves to identify the UAS that is
// responding, possibly resulting in a component of a dialog ID. The
// same tag MUST be used for all responses to that request, both final
// and provisional (again excepting the 100 (Trying)). Procedures for
// the generation of tags are defined in Section 19.3.
response.To = To;
if (To.Parameters["tag"] != null)
{
// RFC3261 Section 17.2.1:
// The 100 (Trying) response is constructed
// according to the procedures in Section 8.2.6, except that the
// insertion of tags in the To header field of the response (when none
// was present in the request) is downgraded from MAY to SHOULD NOT.
if (!StatusCodeHelper.Is1xx(code))
{
response.To.Parameters.Add("tag", Guid.NewGuid().ToString().Replace("-", string.Empty));
}
}
return(response);
}
