/// <summary>
/// Returns a collection of web links from the given HttpWebResponse if they are present in the header. If not, null is returned.
/// </summary>
/// <param name="webResponse"></param>
public static WebLinksCollection GetWebLinks(this HttpWebResponse webResponse)
{
if (!webResponse.Headers.AllKeys.Contains("Link"))
{
return(null);
}
return(WebLinksCollection.Parse(webResponse.Headers["Link"]));
}
/// <summary>
/// Parses the given weblink header and returns a list of WebLink objects
/// </summary>
/// <param name="webLinkHeader"></param>
/// <returns></returns>
public static WebLinksCollection Parse(string webLinkHeader)
{
// Validate the parameters
if (webLinkHeader == null)
{
throw new ArgumentNullException(nameof(webLinkHeader));
}
var attributeNameBuilder = new StringBuilder();
// Parse the data
var collection = new WebLinksCollection();
var webLinkParts = webLinkHeader.Split(',');
for (var i = 0; i < webLinkParts.Length; i++)
{
var webLink = new WebLink();
var part = webLinkParts[i].Trim();
// Simple validation
if ((!part.StartsWith("<") || !part.Contains(">")))
{
if (string.IsNullOrWhiteSpace(part))
{
continue;
}
else
{
throw new WebLinksParserException();
}
}
// Parse the URL
var urlEndIndex = part.IndexOf('>') - 1;
webLink.Url = part.Substring(1, urlEndIndex);
attributeNameBuilder.Clear();
for (var n = urlEndIndex + 3; n < part.Length; n++)
{
var c = part[n];
// These characters should not be present here
if (c == '"' || c == '<' || c == '>' || c == ',')
{
throw new WebLinksParserException();
}
if (c != '=')
{
attributeNameBuilder.Append(c);
continue;
}
// Clean up and validate the name
var name = attributeNameBuilder.ToString();
attributeNameBuilder.Clear();
name = name.Trim();
foreach (var nameChar in name)
{
if (char.IsWhiteSpace(nameChar))
{
throw new WebLinksParserException();
}
}
// Read the value
string value = "";
while (n < part.Length)
{
n++;
if (char.IsWhiteSpace(part[n]))
{
continue;
}
else if (part[n] == '"')
{
// Read the value
var valueEndIndex = part.IndexOf('"', n + 1);
value = part.Substring(n + 1, valueEndIndex - n - 1);
// Advance the original loop
n = valueEndIndex;
break;
}
}
// Construct an attribute
webLink.AddAttribute(name, value);
}
collection.Add(webLink);
}
return(collection);
}