add trade stream to LBank (#741)

Author: vslee

src/ExchangeSharp/API/Exchanges/LBank/ExchangeLBankAPI.cs

@@ -39,6 +39,8 @@ public class ExchangeLBankAPI : ExchangeAPI
 		/// </summary>
 		public override string BaseUrl { get; set; } = "https://api.lbank.info/v1";
 
+		public override string BaseUrlWebSocket { get; set; } = "wss://www.lbkex.net/ws/V2/";
+
 		/// <summary>
 		/// Gets the name of the API.
 		/// </summary>
@@ -539,6 +541,63 @@ private List<ExchangeWithdrawalResponse> ParseWithdrawListResponse(JToken withdr
 
 		#endregion PARSERS PrivateAPI
 
+		#region Websockets
+		protected override async Task<IWebSocket> OnGetTradesWebSocketAsync(Func<KeyValuePair<string, ExchangeTrade>, Task> callback, params string[] marketSymbols)
+		{
+			if (marketSymbols == null || marketSymbols.Length == 0)
+			{
+				marketSymbols = (await GetMarketSymbolsAsync()).ToArray();
+			}
+			return await ConnectPublicWebSocketAsync("", async (_socket, msg) =>
+			{
+				/* {
+					 "trade":{
+						 "volume":6.3607,
+						 "amount":77148.9303,
+						 "price":12129,
+						 "direction":"sell",
+						 "TS":"2019-06-28T19:55:49.460"
+					 },
+					 "type":"trade",
+					 "pair":"btc_usdt",
+					 "SERVER":"V2",
+					 "TS":"2019-06-28T19:55:49.466"
+					}*/
+				JToken token = JToken.Parse(msg.ToStringFromUTF8());
+				if (token["status"].ToStringInvariant() == "error")
+				{
+					if (token["message"].ToStringInvariant().Contains("Invalid order pairs"))
+					{
+						// ignore, bc invalid order pairs are normal in LBank
+					}
+					else throw new APIException(token["message"].ToStringInvariant());
+				}
+				else if (token["type"].ToStringInvariant() == "trade")
+				{
+					var trade = token["trade"].ParseTrade("amount", "price", "direction", "TS", TimestampType.Iso8601China, null);
+					string marketSymbol = token["pair"].ToStringInvariant();
+					await callback(new KeyValuePair<string, ExchangeTrade>(marketSymbol, trade));
+				}
+			}, async (_socket) =>
+			{ /* {
+					"action":"subscribe",
+					"subscribe":"trade",
+					"pair":"eth_btc"
+				  }*/
+				foreach (var marketSymbol in marketSymbols)
+				{
+					var subscribeRequest = new
+					{
+						action = "subscribe",
+						subscribe = "trade",
+						pair = marketSymbol,
+					};
+					await _socket.SendMessageAsync(subscribeRequest);
+				}
+			});
+		}
+		#endregion
+
 		#region HELPERS
 
 		protected override async Task ProcessRequestAsync(IHttpWebRequest request, Dictionary<string, object> payload)

src/ExchangeSharp/Utility/CryptoUtility.cs

@@ -38,6 +38,8 @@ public static class CryptoUtility
         internal static readonly DateTime UnixEpochLocal = new DateTime(1970, 1, 1, 0, 0, 0, 0, DateTimeKind.Local);
         internal static readonly Encoding Utf8EncodingNoPrefix = new UTF8Encoding(false, true);
 		static bool isWindows = System.Runtime.InteropServices.RuntimeInformation.IsOSPlatform(OSPlatform.Windows);
+		static string chinaZoneId = isWindows ? "China Standard Time" : "Asia/Shanghai";
+		static TimeZoneInfo chinaZone = TimeZoneInfo.FindSystemTimeZoneById(chinaZoneId);
 		static string koreanZoneId = isWindows ? "Korea Standard Time" : "Asia/Seoul";
 		static TimeZoneInfo koreaZone = TimeZoneInfo.FindSystemTimeZoneById(koreanZoneId);
 
@@ -188,7 +190,7 @@ public enum SourceTimeZone
 		{
 			/// <summary> time zone is specifically specified in string </summary>
 			AsSpecified,
-			Local, Korea, UTC
+			Local, China, Korea, UTC,
 		}
         /// <summary>
         /// Convert object to a UTC DateTime
@@ -215,6 +217,8 @@ public static DateTime ToDateTimeInvariant(this object obj, SourceTimeZone sourc
 					throw new NotImplementedException(); // TODO: implement this when needed
 				case SourceTimeZone.Local:
 					return DateTime.SpecifyKind(dt, DateTimeKind.Local).ToUniversalTime(); // convert to UTC
+				case SourceTimeZone.China:
+					return TimeZoneInfo.ConvertTime(dt, chinaZone, TimeZoneInfo.Utc); // convert to UTC
 				case SourceTimeZone.Korea:
 					return TimeZoneInfo.ConvertTime(dt, koreaZone, TimeZoneInfo.Utc); // convert to UTC
 				case SourceTimeZone.UTC:
@@ -693,6 +697,9 @@ public static DateTime ParseTimestamp(object value, TimestampType type)
 				case TimestampType.Iso8601Local:
 					return value.ToDateTimeInvariant(SourceTimeZone.Local);
 
+				case TimestampType.Iso8601China:
+					return value.ToDateTimeInvariant(SourceTimeZone.China);
+
 				case TimestampType.Iso8601Korea:
 					return value.ToDateTimeInvariant(SourceTimeZone.Korea);
 
@@ -1481,6 +1488,11 @@ public enum TimestampType
 		/// </summary>
 		Iso8601Local,
 
+		/// <summary>
+		/// ISO 8601 in china Standard Time
+		/// </summary>
+		Iso8601China,
+
 		/// <summary>
 		/// ISO 8601 in Korea Standard Time
 		/// </summary>