C# Parse Link Header

c-sharp-parse-linkheader.cs

public class LinkHeader
{
    public string FirstLink { get; set; }
    public string PrevLink { get; set; }
    public string NextLink { get; set; }
    public string LastLink { get; set; }

    public static LinkHeader LinksFromHeader(string linkHeaderStr)
    {
        LinkHeader linkHeader = null;

        if (!string.IsNullOrWhiteSpace(linkHeaderStr))
        {
            string[] linkStrings = linkHeaderStr.Split(',');

            if (linkStrings != null && linkStrings.Any())
            {
                linkHeader = new LinkHeader();

                foreach (string linkString in linkStrings)
                {
                    var relMatch = Regex.Match(linkString, "(?<=rel=\").+?(?=\")", RegexOptions.IgnoreCase);
                    var linkMatch = Regex.Match(linkString, "(?<=<).+?(?=>)", RegexOptions.IgnoreCase);

                    if (relMatch.Success && linkMatch.Success)
                    {
                        string rel = relMatch.Value.ToUpper();
                        string link = linkMatch.Value;

                        switch (rel)
                        {
                            case "FIRST":
                                linkHeader.FirstLink = link;
                                break;
                            case "PREV":
                                linkHeader.PrevLink = link;
                                break;
                            case "NEXT":
                                linkHeader.NextLink = link;
                                break;
                            case "LAST":
                                linkHeader.LastLink = link;
                                break;
                        }
                    }
                }
            }
        }

        return linkHeader;
    }
}

Thank You!

Thanks!

thanks

@Knazys, @caiolouro, @iesen -- most welcome :)

Awesome work, many thanks.

Thanks!

Made an F# version:

module Http =
    type LinkHeader = {
        First : string option
        Last : string option
        Next : string option
        Previous : string option
    }
        with
            static member Empty =
                {
                    First = None
                    Last = None
                    Next = None
                    Previous = None
                }
    module LinkHeader =
        open System.Text.RegularExpressions
        let parse (linkHeader : string) =
            let linksStrings = linkHeader.Split(',')
            let linkHeader = LinkHeader.Empty
            let findLink (linkString : string) =
                let relMatch = Regex.Match(linkString, "(?<=rel=\").+?(?=\")", RegexOptions.IgnoreCase)
                let linkMatch = Regex.Match(linkString, "(?<=<).+?(?=>)", RegexOptions.IgnoreCase)
                if relMatch.Success && linkMatch.Success then
                    Some (relMatch.Value.ToUpper(), linkMatch.Value)
                else
                    None
            (linkHeader,linksStrings)
            ||> Array.fold (fun lh ls ->
                match findLink ls with
                | Some("FIRST", l) ->
                    { lh with First = Option.ofObj l}
                | Some("PREV", l) ->
                    { lh with Previous = Option.ofObj l}
                | Some("NEXT", l) ->
                    { lh with Next = Option.ofObj l}
                | Some("LAST", l) ->
                    { lh with Last = Option.ofObj l}
                | _ ->
                    lh
            )

Yasssss @TheAngryByrd!

I added the following ctor.

    public static LinkHeader LinksFromHeader(HttpResponseMessage httpResponseMessage)
    {
      if (httpResponseMessage.Headers.Contains("Link"))
      {
        return CreateInstance(httpResponseMessage.Headers.GetValues("Link").FirstOrDefault());
      }

      return null;
    }

I am using it to loop though and build a list of GitHub Pull Requests.

      var jsonList = new List<string>();
      var url = $"{repo.Url}/pulls?state=closed&base=develop";
      do
      {
        HttpResponseMessage response = httpClient.GetAsync(url).Result;

        var linkHeader = LinkHeader.LinksFromHeader(response);

        using (StreamReader stream = new StreamReader(response.Content.ReadAsStreamAsync().Result))
        {
          jsonList.Add(stream.ReadToEnd());
        }

        url = linkHeader.NextLink;

      } while (url != null);

      return jsonList;

Full Source: https://gist.github.com/Digitalroot/e9ca35596664fccd13494cf2da975aa2

Many thanks Pim! It Works!

Note that this breaks if the URL's themselves have commas in them. A more robust solution is here: https://stackoverflow.com/a/72034960

Works great, thanks!

Is there a JS/TS equivalent to this? If not, could someone please help me with writing this?