Add basic online API support.

osu.Game/Online/API/OAuthToken.cs

@@ -0,0 +1,65 @@
+//Copyright (c) 2007-2016 ppy Pty Ltd <contact@ppy.sh>.
+//Licensed under the MIT Licence - https://raw.githubusercontent.com/ppy/osu/master/LICENCE
+
+using System;
+using System.Globalization;
+using Newtonsoft.Json;
+
+namespace osu.Game.Online.API
+{
+    [Serializable]
+    internal class OAuthToken
+    {
+        /// <summary>
+        /// OAuth 2.0 access token.
+        /// </summary>
+        [JsonProperty(@"access_token")]
+        public string AccessToken;
+
+        [JsonProperty(@"expires_in")]
+        public long ExpiresIn
+        {
+            get
+            {
+                return AccessTokenExpiry - DateTime.Now.ToUnixTimestamp();
+            }
+
+            set
+            {
+                AccessTokenExpiry = DateTime.Now.AddSeconds(value).ToUnixTimestamp();
+            }
+        }
+
+        public bool IsValid => !string.IsNullOrEmpty(AccessToken) && ExpiresIn > 30;
+
+        public long AccessTokenExpiry;
+
+        /// <summary>
+        /// OAuth 2.0 refresh token.
+        /// </summary>
+        [JsonProperty(@"refresh_token")]
+        public string RefreshToken;
+
+        public override string ToString() => $@"{AccessToken}/{AccessTokenExpiry.ToString(NumberFormatInfo.InvariantInfo)}/{RefreshToken}";
+
+        public static OAuthToken Parse(string value)
+        {
+            try
+            {
+                string[] parts = value.Split('/');
+                return new OAuthToken()
+                {
+                    AccessToken = parts[0],
+                    AccessTokenExpiry = long.Parse(parts[1], NumberFormatInfo.InvariantInfo),
+                    RefreshToken = parts[2]
+                };
+            }
+            catch
+            {
+
+            }
+
+            return null;
+        }
+    }
+}