(GH-361) More robust 'Link' parser

Source/StrongGrid/Extensions/Internal.cs

@@ -269,10 +269,12 @@ internal static Task<PaginatedResponseWithLinks<T>> AsPaginatedResponseWithLinks
 			var link = response.Message.Headers.GetValue("Link");
 			if (string.IsNullOrEmpty(link))
 			{
-				throw new Exception("The 'Link' header is missing form the response");
+				throw new Exception("The 'Link' header is missing from the response");
 			}
 
-			return response.Message.Content.AsPaginatedResponseWithLinks<T>(link, propertyName, jsonConverter);
+			var paginationLinks = PaginationLinksParser.Parse(link);
+
+			return response.Message.Content.AsPaginatedResponseWithLinks<T>(paginationLinks, propertyName, jsonConverter);
 		}
 
 		/// <summary>Asynchronously retrieve the JSON encoded content and convert it to a 'AsPaginatedResponseWithLinks' object.</summary>
@@ -915,12 +917,12 @@ private static async Task<PaginatedResponse<T>> AsPaginatedResponse<T>(this Http
 		/// <summary>Asynchronously retrieve the JSON encoded content and convert it to a 'PaginatedResponseWithLinks' object.</summary>
 		/// <typeparam name="T">The response model to deserialize into.</typeparam>
 		/// <param name="httpContent">The content.</param>
-		/// <param name="linkHeaderValue">The content of the 'Link' header.</param>
+		/// <param name="paginationLinks">The pagination links.</param>
 		/// <param name="propertyName">The name of the JSON property (or null if not applicable) where the desired data is stored.</param>
 		/// <param name="jsonConverter">Converter that will be used during deserialization.</param>
 		/// <returns>Returns the response body, or <c>null</c> if the response has no body.</returns>
 		/// <exception cref="SendGridException">An error occurred processing the response.</exception>
-		private static async Task<PaginatedResponseWithLinks<T>> AsPaginatedResponseWithLinks<T>(this HttpContent httpContent, string linkHeaderValue, string propertyName, JsonConverter jsonConverter = null)
+		private static async Task<PaginatedResponseWithLinks<T>> AsPaginatedResponseWithLinks<T>(this HttpContent httpContent, IEnumerable<PaginationLink> paginationLinks, string propertyName, JsonConverter jsonConverter = null)
 		{
 			var responseContent = await httpContent.ReadAsStringAsync(null).ConfigureAwait(false);
 
@@ -945,38 +947,12 @@ private static async Task<PaginatedResponseWithLinks<T>> AsPaginatedResponseWith
 				records = JArray.Parse(responseContent).ToObject<T[]>(serializer);
 			}
 
-			var links = linkHeaderValue
-				.Split(new[] { ',' }, StringSplitOptions.RemoveEmptyEntries)
-				.Select(link => link.Split(new[] { ';' }, StringSplitOptions.RemoveEmptyEntries))
-				.Select(linkParts =>
-				{
-					var link = linkParts[0]
-						.Trim()
-						.TrimStart(new[] { '<' })
-						.TrimEnd(new[] { '>' });
-
-					var rel = linkParts[1]
-						.Split(new[] { '=' }, StringSplitOptions.RemoveEmptyEntries)[1]
-						.Trim(new[] { ' ', '"' });
-
-					var pageNum = linkParts[2]
-						.Split(new[] { '=' }, StringSplitOptions.RemoveEmptyEntries)[1]
-						.Trim(new[] { ' ', '"' });
-
-					return new PaginationLink()
-					{
-						Link = link,
-						Rel = rel,
-						PageNumber = int.Parse(pageNum)
-					};
-				});
-
 			var result = new PaginatedResponseWithLinks<T>()
 			{
-				First = links.Single(l => l.Rel == "first"),
-				Previous = links.Single(l => l.Rel == "prev"),
-				Next = links.Single(l => l.Rel == "next"),
-				Last = links.Single(l => l.Rel == "last"),
+				First = paginationLinks.SingleOrDefault(l => l.Relationship == "first"),
+				Previous = paginationLinks.SingleOrDefault(l => l.Relationship == "prev"),
+				Next = paginationLinks.SingleOrDefault(l => l.Relationship == "next"),
+				Last = paginationLinks.SingleOrDefault(l => l.Relationship == "last"),
 				Records = records
 			};
 

Source/StrongGrid/Models/PaginationLink.cs

@@ -1,3 +1,6 @@
+using System;
+using System.Collections.Generic;
+
 namespace StrongGrid.Models
 {
 	/// <summary>
@@ -6,21 +9,36 @@ namespace StrongGrid.Models
 	public class PaginationLink
 	{
 		/// <summary>
-		/// Gets or sets the uri to the page.
+		/// Gets or sets the uri.
 		/// </summary>
-		public string Link { get; set; }
+		public Uri Link { get; set; }
 
 		/// <summary>
-		/// Gets or sets the value describing the pagination link.
+		/// Gets or sets the relationship.
+		/// </summary>
+		public string Relationship { get; set; }
+
+		/// <summary>
+		/// Gets or sets the relationship.
 		/// </summary>
 		/// <remarks>
-		/// There are 4 possible values: first, prev, next and last.
+		/// 'Rev' is obviously short for something but I can't figure out what it stands for????
 		/// </remarks>
-		public string Rel { get; set; }
+		public string Rev { get; set; }
+
+		/// <summary>
+		/// Gets or sets the title.
+		/// </summary>
+		public string Title { get; set; }
+
+		/// <summary>
+		/// Gets or sets the anchor.
+		/// </summary>
+		public Uri Anchor { get; set; }
 
 		/// <summary>
-		/// Gets or sets the page number.
+		/// Gets or sets the extensions.
 		/// </summary>
-		public int PageNumber { get; set; }
+		public IEnumerable<KeyValuePair<string, string>> Extensions { get; set; }
 	}
 }

Source/StrongGrid/Utilities/PaginationLinksParser.cs

@@ -0,0 +1,64 @@
+using StrongGrid.Models;
+using System;
+using System.Collections.Generic;
+using System.Linq;
+
+namespace StrongGrid.Utilities
+{
+	/// <summary>
+	/// Parser for pagination links.
+	/// </summary>
+	/// <remarks>
+	/// This parser attempts to respect the HTTP 1.1 'Link' rules defined in <see cref="https://tools.ietf.org/html/rfc2068#section-19.6.2.4">RFC 2068</see>.
+	/// </remarks>
+	public static class PaginationLinksParser
+	{
+		private static readonly string[] _wellKnownLinkParts = new[] { "rel", "rev", "title", "anchor" };
+
+		/// <summary>
+		/// Parse the content of the link response header.
+		/// </summary>
+		/// <param name="linkHeaderContent">The content of the link header.</param>
+		/// <returns>An array of <see cref="PaginationLink"/>.</returns>
+		public static PaginationLink[] Parse(string linkHeaderContent)
+		{
+			var paginationLinks = linkHeaderContent
+				.Split(new[] { ',' }, StringSplitOptions.RemoveEmptyEntries)
+				.Select(link => link.Split(new[] { ';' }, StringSplitOptions.RemoveEmptyEntries))
+				.Select(linkParts =>
+				{
+					var dict = new Dictionary<string, string>();
+					foreach (var linkPart in linkParts.Skip(1))
+					{
+						var parts = linkPart.Split(new[] { '=' }, StringSplitOptions.RemoveEmptyEntries);
+						var partName = parts[0].Trim();
+						var partValue = parts[1].Trim(new[] { ' ', '"' });
+
+						dict.Add(partName, partValue);
+					}
+
+					var link = linkParts[0].Trim().TrimStart(new[] { '<' }).TrimEnd(new[] { '>' }).Trim();
+					dict.TryGetValue("rel", out string rel);
+					dict.TryGetValue("rev", out string rev);
+					dict.TryGetValue("title", out string title);
+					dict.TryGetValue("anchor", out string anchor);
+
+					var extensions = dict
+						.Where(item => !_wellKnownLinkParts.Contains(item.Key))
+						.ToArray();
+
+					return new PaginationLink()
+					{
+						Link = !string.IsNullOrEmpty(link) ? new Uri(link) : null,
+						Relationship = rel,
+						Rev = rev,
+						Title = title,
+						Anchor = !string.IsNullOrEmpty(anchor) ? new Uri(anchor) : null,
+						Extensions = extensions
+					};
+				});
+
+			return paginationLinks.ToArray();
+		}
+	}
+}