Add basic online API support.

osu.Game/Online/API/OAuth.cs

@@ -0,0 +1,162 @@
+//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.Diagnostics;
+using osu.Framework.IO.Network;
+
+namespace osu.Game.Online.API
+{
+    internal class OAuth
+    {
+        private readonly string clientId;
+        private readonly string clientSecret;
+        private readonly string endpoint;
+
+        public OAuthToken Token;
+
+        internal OAuth(string clientId, string clientSecret, string endpoint)
+        {
+            Debug.Assert(clientId != null);
+            Debug.Assert(clientSecret != null);
+            Debug.Assert(endpoint != null);
+
+            this.clientId = clientId;
+            this.clientSecret = clientSecret;
+            this.endpoint = endpoint;
+        }
+
+        internal bool AuthenticateWithLogin(string username, string password)
+        {
+            var req = new AccessTokenRequestPassword(username, password)
+            {
+                Url = $@"{endpoint}/oauth/access_token",
+                Method = HttpMethod.POST,
+                ClientId = clientId,
+                ClientSecret = clientSecret
+            };
+
+            try
+            {
+                req.BlockingPerform();
+            }
+            catch
+            {
+                return false;
+            }
+
+            Token = req.ResponseObject;
+            return true;
+        }
+
+        internal bool AuthenticateWithRefresh(string refresh)
+        {
+            try
+            {
+                var req = new AccessTokenRequestRefresh(refresh)
+                {
+                    Url = $@"{endpoint}/oauth/access_token",
+                    Method = HttpMethod.POST,
+                    ClientId = clientId,
+                    ClientSecret = clientSecret
+                };
+                req.BlockingPerform();
+
+                Token = req.ResponseObject;
+                return true;
+            }
+            catch (Exception e)
+            {
+                //todo: potentially only kill the refresh token on certain exception types.
+                Token = null;
+                return false;
+            }
+        }
+
+        /// <summary>
+        /// Should be run before any API request to make sure we have a valid key.
+        /// </summary>
+        private bool ensureAccessToken()
+        {
+            //todo: we need to mutex this to ensure only one authentication request is running at a time.
+
+            //If we already have a valid access token, let's use it.
+            if (accessTokenValid) return true;
+
+            //If not, let's try using our refresh token to request a new access token.
+            if (!string.IsNullOrEmpty(Token?.RefreshToken))
+                AuthenticateWithRefresh(Token.RefreshToken);
+
+            return accessTokenValid;
+        }
+
+        private bool accessTokenValid => Token?.IsValid ?? false;
+
+        internal bool HasValidAccessToken => RequestAccessToken() != null;
+
+        internal string RequestAccessToken()
+        {
+            if (!ensureAccessToken()) return null;
+
+            return Token.AccessToken;
+        }
+
+        internal void Clear()
+        {
+            Token = null;
+        }
+
+        private class AccessTokenRequestRefresh : AccessTokenRequest
+        {
+            internal readonly string RefreshToken;
+
+            internal AccessTokenRequestRefresh(string refreshToken)
+            {
+                RefreshToken = refreshToken;
+                GrantType = @"refresh_token";
+            }
+
+            protected override void PrePerform()
+            {
+                Parameters[@"refresh_token"] = RefreshToken;
+                base.PrePerform();
+            }
+        }
+
+        private class AccessTokenRequestPassword : AccessTokenRequest
+        {
+            internal readonly string Username;
+            internal readonly string Password;
+
+            internal AccessTokenRequestPassword(string username, string password)
+            {
+                Username = username;
+                Password = password;
+                GrantType = @"password";
+            }
+
+            protected override void PrePerform()
+            {
+                Parameters[@"username"] = Username;
+                Parameters[@"password"] = Password;
+                base.PrePerform();
+            }
+        }
+
+        private class AccessTokenRequest : JsonWebRequest<OAuthToken>
+        {
+            protected string GrantType;
+
+            internal string ClientId;
+            internal string ClientSecret;
+
+            protected override void PrePerform()
+            {
+                Parameters[@"grant_type"] = GrantType;
+                Parameters[@"client_id"] = ClientId;
+                Parameters[@"client_secret"] = ClientSecret;
+                base.PrePerform();
+            }
+        }
+    }
+}