XUnity.AutoTranslator/src/XUnity.AutoTranslator.Plugin.Core/Web/BaiduTranslateEndpoint.cs

using System;
using System.Collections.Generic;
using System.IO;
using System.Net;
using System.Security.Cryptography;
using System.Text;
using SimpleJSON;
using UnityEngine;
using XUnity.AutoTranslator.Plugin.Core.Configuration;
using XUnity.AutoTranslator.Plugin.Core.Constants;
using XUnity.AutoTranslator.Plugin.Core.Extensions;

namespace XUnity.AutoTranslator.Plugin.Core.Web
{
   public class BaiduTranslateEndpoint : KnownHttpEndpoint
   {
      private static readonly string HttpServicePointTemplateUrl = "http://api.fanyi.baidu.com/api/trans/vip/translate?q={0}&from={1}&to={2}&appid={3}&salt={4}&sign={5}";

      private static readonly MD5 HashMD5 = MD5.Create();

      public BaiduTranslateEndpoint()
      {
         ServicePointManager.ServerCertificateValidationCallback += Security.AlwaysAllowByHosts( "api.fanyi.baidu.com" );
      }

      private static string CreateMD5( string input )
      {
         byte[] inputBytes = Encoding.UTF8.GetBytes( input );
         byte[] hashBytes = HashMD5.ComputeHash( inputBytes );

         StringBuilder sb = new StringBuilder();
         for( int i = 0 ; i < hashBytes.Length ; i++ )
         {
            sb.Append( hashBytes[ i ].ToString( "X2" ) );
         }
         return sb.ToString().ToLower();
      }

      public override void ApplyHeaders( WebHeaderCollection headers )
      {
         headers[ HttpRequestHeader.UserAgent ] = Settings.GetUserAgent( "Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/70.0.3538.102 Safari/537.36" );
         headers[ HttpRequestHeader.AcceptCharset ] = "UTF-8";
      }

      public override bool TryExtractTranslated( string result, out string translated )
      {
         try
         {
            if( result.StartsWith( "{\"error" ) )
            {
               translated = null;
               return false;
            }


            var obj = JSON.Parse( result );
            var lineBuilder = new StringBuilder( result.Length );

            foreach( JSONNode entry in obj.AsObject[ "trans_result" ].AsArray )
            {
               var token = entry.AsObject[ "dst" ].ToString();
               token = token.Substring( 1, token.Length - 2 ).UnescapeJson();

               if( !lineBuilder.EndsWithWhitespaceOrNewline() ) lineBuilder.Append( "\n" );

               lineBuilder.Append( token );
            }

            translated = lineBuilder.ToString();

            var success = !string.IsNullOrEmpty( translated );
            return success;
         }
         catch( Exception )
         {
            translated = null;
            return false;
         }
      }

      public override string GetServiceUrl( string untranslatedText, string from, string to )
      {
         string salt = DateTime.UtcNow.Millisecond.ToString();
         var md5 = CreateMD5( Settings.BaiduAppId + untranslatedText + salt + Settings.BaiduAppSecret );

         return string.Format( HttpServicePointTemplateUrl, WWW.EscapeURL( untranslatedText ), from, to, Settings.BaiduAppId, salt, md5 );
      }
   }
}