private static WebSubDiscoveredUrls ParseWebLinkHeader(WebSubDiscoveredUrls webSubDiscovery, string linkHeader)
{
string inputString = linkHeader;
int inputPos = 0;
Token nextToken = new Token {
Type = TokenType.None
};
while (true)
{
try
{
nextToken = ReadToken(inputString, ref inputPos);
if (nextToken.Type == TokenType.Url)
{
webSubDiscovery = ParseWebLinkHeaderValue(webSubDiscovery, inputString, ref inputPos, ref nextToken);
}
else if (nextToken.Type == TokenType.EOF)
{
break;
}
else
{
ThrowFormatException(String.Format("Unexpected token '{0}' (expected URL)", nextToken.Type), inputString, inputPos);
}
if (nextToken.Type == TokenType.Comma)
{
continue;
}
else if (nextToken.Type == TokenType.EOF)
{
break;
}
else
{
ThrowFormatException(String.Format("Unexpected token '{0}' (expected comma)", nextToken.Type), inputString, inputPos);
}
}
catch (FormatException)
{
while (nextToken.Type != TokenType.Comma && nextToken.Type != TokenType.EOF)
{
try
{
nextToken = ReadToken(inputString, ref inputPos);
}
catch (FormatException)
{ }
}
}
}
return(webSubDiscovery);
}
public static WebSubDiscoveredUrls ParseWebLinkHeaders(IEnumerable <string> linkHeaders)
{
WebSubDiscoveredUrls webSubDiscovery = new WebSubDiscoveredUrls();
foreach (string linkHeader in linkHeaders)
{
webSubDiscovery = ParseWebLinkHeader(webSubDiscovery, linkHeader);
}
return(webSubDiscovery);
}
private static WebSubDiscoveredUrls ParseWebLinkHeaderValue(WebSubDiscoveredUrls webSubDiscovery, string inputString, ref int inputPos, ref Token nextToken)
{
string url = nextToken.Value;
string rel = null;
nextToken = ReadToken(inputString, ref inputPos);
while (nextToken.Type == TokenType.Semicolon)
{
try
{
nextToken = ReadToken(inputString, ref inputPos);
var(id, value) = ParseParameter(inputString, ref inputPos, ref nextToken);
if (id == "rel" && rel == null)
{
rel = value;
}
}
catch (FormatException)
{
while (nextToken.Type != TokenType.Semicolon && nextToken.Type != TokenType.Comma && nextToken.Type != TokenType.EOF)
{
try
{
nextToken = ReadToken(inputString, ref inputPos);
}
catch (FormatException)
{
}
}
}
}
if (rel == HUB_RELATION)
{
webSubDiscovery.AddHub(url);
}
else if (rel == TOPIC_RELATION)
{
if (!String.IsNullOrWhiteSpace(webSubDiscovery.Topic))
{
throw new WebSubDiscoveryException("Multiple canonical URLs for the topic have been found.");
}
webSubDiscovery.Topic = url;
}
return(webSubDiscovery);
}
public async Task <WebSubDiscoveredUrls> DiscoverAsync(string requestUri, CancellationToken cancellationToken)
{
HttpResponseMessage discoveryResponse = await _httpClient.GetAsync(requestUri, HttpCompletionOption.ResponseHeadersRead, cancellationToken);
if (discoveryResponse.StatusCode == HttpStatusCode.OK)
{
if (discoveryResponse.Headers.Contains(LINK_HEADER))
{
WebSubDiscoveredUrls webSubDiscovery = WebLinkParser.ParseWebLinkHeaders(discoveryResponse.Headers.GetValues(LINK_HEADER));
if (RequiredUrlsIdentified(webSubDiscovery))
{
return(webSubDiscovery);
}
}
}
throw new WebSubDiscoveryException("The discovery mechanism haven't identified required URLs.", discoveryResponse);
}
private static bool RequiredUrlsIdentified(WebSubDiscoveredUrls webSubDiscovery)
{
return(!String.IsNullOrWhiteSpace(webSubDiscovery.Topic) && (webSubDiscovery.Hubs != null) && (webSubDiscovery.Hubs.Any()));
}