OpenTween/Api/MicrosoftTranslatorApi.cs

   1 // OpenTween - Client of Twitter
   2 // Copyright (c) 2016 kim_upsilon (@kim_upsilon) <https://upsilo.net/~upsilon/>
   3 // All rights reserved.
   4 //
   5 // This file is part of OpenTween.
   6 //
   7 // This program is free software; you can redistribute it and/or modify it
   8 // under the terms of the GNU General Public License as published by the Free
   9 // Software Foundation; either version 3 of the License, or (at your option)
  10 // any later version.
  11 //
  12 // This program is distributed in the hope that it will be useful, but
  13 // WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
  14 // or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
  15 // for more details.
  16 //
  17 // You should have received a copy of the GNU General Public License along
  18 // with this program. If not, see <http://www.gnu.org/licenses/>, or write to
  19 // the Free Software Foundation, Inc., 51 Franklin Street - Fifth Floor,
  20 // Boston, MA 02110-1301, USA.
  21
  22 using System;
  23 using System.Collections.Generic;
  24 using System.Linq;
  25 using System.Net.Http;
  26 using System.Net.Http.Headers;
  27 using System.Runtime.Serialization.Json;
  28 using System.Text;
  29 using System.Threading.Tasks;
  30 using System.Xml;
  31 using System.Xml.Linq;
  32 using OpenTween.Connection;
  33
  34 namespace OpenTween.Api
  35 {
  36     public class MicrosoftTranslatorApi
  37     {
  38         public static readonly Uri OAuthEndpoint = new Uri("https://datamarket.accesscontrol.windows.net/v2/OAuth2-13");
  39         public static readonly Uri TranslateEndpoint = new Uri("https://api.microsofttranslator.com/v2/Http.svc/Translate");
  40
  41         public string AccessToken { get; internal set; }
  42         public DateTime RefreshAccessTokenAt { get; internal set; }
  43
  44         private HttpClient Http => this.localHttpClient ?? Networking.Http;
  45         private readonly HttpClient localHttpClient;
  46
  47         public MicrosoftTranslatorApi()
  48             : this(null)
  49         {
  50         }
  51
  52         public MicrosoftTranslatorApi(HttpClient http)
  53         {
  54             this.localHttpClient = http;
  55         }
  56
  57         public async Task<string> TranslateAsync(string text, string langTo, string langFrom = null)
  58         {
  59             await this.UpdateAccessTokenIfExpired()
  60                 .ConfigureAwait(false);
  61
  62             var param = new Dictionary<string, string>
  63             {
  64                 ["text"] = text,
  65                 ["to"] = langTo,
  66             };
  67
  68             if (langFrom != null)
  69                 param["from"] = langFrom;
  70
  71             var requestUri = new Uri(TranslateEndpoint, "?" + MyCommon.BuildQueryString(param));
  72
  73             using (var request = new HttpRequestMessage(HttpMethod.Get, requestUri))
  74             {
  75                 request.Headers.Authorization = new AuthenticationHeaderValue("Bearer", this.AccessToken);
  76
  77                 using (var response = await this.Http.SendAsync(request).ConfigureAwait(false))
  78                 {
  79                     return await response.Content.ReadAsStringAsync()
  80                         .ConfigureAwait(false);
  81                 }
  82             }
  83         }
  84
  85         public async Task UpdateAccessTokenIfExpired()
  86         {
  87             if (this.AccessToken != null && this.RefreshAccessTokenAt > DateTime.Now)
  88                 return;
  89
  90             var (accessToken, expiresIn) = await this.GetAccessTokenAsync()
  91                 .ConfigureAwait(false);
  92
  93             this.AccessToken = accessToken;
  94
  95             // expires_in の示す時刻より 30 秒早めに再発行する
  96             this.RefreshAccessTokenAt = DateTime.Now + expiresIn - TimeSpan.FromSeconds(30);
  97         }
  98
  99         internal virtual async Task<(string AccessToken, TimeSpan ExpiresIn)> GetAccessTokenAsync()
 100         {
 101             var param = new Dictionary<string, string>
 102             {
 103                 ["grant_type"] = "client_credentials",
 104                 ["client_id"] = ApplicationSettings.AzureClientId,
 105                 ["client_secret"] = ApplicationSettings.AzureClientSecret,
 106                 ["scope"] = "http://api.microsofttranslator.com",
 107             };
 108
 109             using (var request = new HttpRequestMessage(HttpMethod.Post, OAuthEndpoint))
 110             using (var postContent = new FormUrlEncodedContent(param))
 111             {
 112                 request.Content = postContent;
 113
 114                 using (var response = await this.Http.SendAsync(request).ConfigureAwait(false))
 115                 {
 116                     var responseBytes = await response.Content.ReadAsByteArrayAsync()
 117                         .ConfigureAwait(false);
 118
 119                     return ParseOAuthCredential(responseBytes);
 120                 }
 121             }
 122         }
 123
 124         internal static (string AccessToken, TimeSpan ExpiresIn) ParseOAuthCredential(byte[] responseBytes)
 125         {
 126             using (var jsonReader = JsonReaderWriterFactory.CreateJsonReader(responseBytes, XmlDictionaryReaderQuotas.Max))
 127             {
 128                 var xElm = XElement.Load(jsonReader);
 129
 130                 var tokenTypeElm = xElm.Element("token_type");
 131                 if (tokenTypeElm == null)
 132                     throw new WebApiException("Property `token_type` required");
 133
 134                 var accessTokenElm = xElm.Element("access_token");
 135                 if (accessTokenElm == null)
 136                     throw new WebApiException("Property `access_token` required");
 137
 138                 var expiresInElm = xElm.Element("expires_in");
 139
 140                 int expiresInSeconds;
 141                 if (expiresInElm != null)
 142                 {
 143                     if (!int.TryParse(expiresInElm.Value, out expiresInSeconds))
 144                         throw new WebApiException("Invalid number: expires_in = " + expiresInElm.Value);
 145                 }
 146                 else
 147                 {
 148                     // expires_in が省略された場合は有効期間が不明なので、
 149                     // 次回のリクエスト時は経過時間に関わらずアクセストークンの再発行を行う
 150                     expiresInSeconds = 0;
 151                 }
 152
 153                 return (accessTokenElm.Value, TimeSpan.FromSeconds(expiresInSeconds));
 154             }
 155         }
 156     }
 157 }