/// <summary>Gets the URLs from the Link HTTP header, if any.</summary>
/// <param name="source">The source.</param>
/// <returns>The list of URLs.</returns>
/// <remarks>
/// If there are multiple link headers then they are concatenated.
/// <para />
/// Multiple links with the same relation are not filtered out.
/// </remarks>
public static IEnumerable <HeaderLinkUrl> GetLink(this HttpResponseHeaders source)
{
IEnumerable <string> values;
if (source.TryGetValues(StandardHeaders.Links, out values) && (values?.Any() ?? false))
{
foreach (var value in values)
{
if (String.IsNullOrEmpty(value))
{
continue;
}
//Links are separated by commas
var links = value.Split(',');
foreach (var link in links)
{
if (String.IsNullOrEmpty(link))
{
continue;
}
HeaderLinkUrl url;
if (HeaderLinkUrl.TryParse(link, out url))
{
yield return(url);
}
}
;
}
;
}
;
}
/// <summary>Attempts to parse a formatted string to a link URL.</summary>
/// <param name="value">The value to parse.</param>
/// <param name="result">The result.</param>
/// <returns><see langword="true"/> if successful or <see langword="false"/> otherwise.</returns>
/// <remarks>
/// The string is expected to be formatted as required for the LINK header.
/// </remarks>
public static bool TryParse(string value, out HeaderLinkUrl result)
{
result = null;
if (String.IsNullOrEmpty(value))
{
return(false);
}
//Format is <{url}>[; rel="{rel}">
var match = s_re.Match(value);
if (!match.Success)
{
return(false);
}
var str = match.Groups["url"]?.Value;
Uri uri;
if (String.IsNullOrEmpty(str) || !Uri.TryCreate(str, UriKind.Absolute, out uri))
{
return(false);
}
var url = new HeaderLinkUrl(uri);
//Parse the relations, if any
var relationValue = match.Groups["relation"]?.Value;
if (!String.IsNullOrEmpty(relationValue))
{
var relations = relationValue.Split(s_relationDelimiters, StringSplitOptions.RemoveEmptyEntries);
url.Relations.AddRange(relations);
}
;
result = url;
return(true);
}
