1 files changed, 65 insertions, 0 deletions
diff --git a/src/DotNetOpenId/Extensions/AliasManager.cs b/src/DotNetOpenId/Extensions/AliasManager.cs
new file mode 100644
index 0000000..70aca3c
--- /dev/null
+++ b/src/DotNetOpenId/Extensions/AliasManager.cs
@@ -0,0 +1,65 @@
+using System;
+using System.Collections.Generic;
+using System.Text;
+using System.Diagnostics;
+using System.Globalization;
+
+namespace DotNetOpenId.Extensions {
+	class AliasManager {
+		readonly string aliasFormat = "alias{0}";
+		/// <summary>
+		/// Tracks extension Type URIs and aliases assigned to them.
+		/// </summary>
+		Dictionary<string, string> typeUriToAliasMap = new Dictionary<string, string>();
+		/// <summary>
+		/// Tracks extension aliases and Type URIs assigned to them.
+		/// </summary>
+		Dictionary<string, string> aliasToTypeUriMap = new Dictionary<string, string>();
+
+		/// <summary>
+		/// Gets an alias assigned for a given Type URI.  A new alias is assigned if necessary.
+		/// </summary>
+		public string GetAlias(string typeUri) {
+			if (string.IsNullOrEmpty(typeUri)) throw new ArgumentNullException("typeUri");
+			string alias;
+			if (typeUriToAliasMap.TryGetValue(typeUri, out alias))
+				return alias;
+			else
+				return assignNewAlias(typeUri);
+		}
+
+		/// <summary>
+		/// Sets an alias and the value that will be returned by <see cref="ResolveAlias"/>.
+		/// </summary>
+		public void SetAlias(string alias, string typeUri) {
+			if (string.IsNullOrEmpty(alias)) throw new ArgumentNullException("alias");
+			if (string.IsNullOrEmpty(typeUri)) throw new ArgumentNullException("typeUri");
+			aliasToTypeUriMap.Add(alias, typeUri);
+			typeUriToAliasMap.Add(typeUri, alias);
+		}
+
+		/// <summary>
+		/// Gets the Type Uri encoded by a given alias.
+		/// </summary>
+		public string ResolveAlias(string alias) {
+			if (string.IsNullOrEmpty(alias)) throw new ArgumentNullException("alias");
+			string typeUri;
+			if (!aliasToTypeUriMap.TryGetValue(alias, out typeUri))
+				throw new ArgumentOutOfRangeException("alias");
+			return typeUri;
+		}
+
+		public IEnumerable<string> Aliases {
+			get { return aliasToTypeUriMap.Keys; }
+		}
+
+		string assignNewAlias(string typeUri) {
+			Debug.Assert(!string.IsNullOrEmpty(typeUri));
+			Debug.Assert(!typeUriToAliasMap.ContainsKey(typeUri));
+			string alias = string.Format(CultureInfo.InvariantCulture, aliasFormat, typeUriToAliasMap.Count + 1);
+			typeUriToAliasMap.Add(typeUri, alias);
+			aliasToTypeUriMap.Add(alias, typeUri);
+			return alias;
+		}
+	}
+}