text: 'use strict';
  
  //  ---------------------------------------------------------------------------
  
  const Exchange = require ('./base/Exchange');
  const { ExchangeError, ArgumentsRequired, DDoSProtection, InsufficientFunds, InvalidOrder, OrderNotFound, AuthenticationError, BadRequest } = require ('./base/errors');
  
  //  ---------------------------------------------------------------------------
  
  module.exports = class okcoinusd extends Exchange {
      describe () {
          return this.deepExtend (super.describe (), {
              'id': 'okcoinusd',
              'name': 'OKCoin USD',
              'countries': [ 'CN', 'US' ],
              'version': 'v1',
              'rateLimit': 1000, // up to 3000 requests per 5 minutes ≈ 600 requests per minute ≈ 10 requests per second ≈ 100 ms
              'has': {
                  'CORS': false,
                  'fetchOHLCV': true,
                  'fetchOrder': true,
                  'fetchOrders': false,
                  'fetchOpenOrders': true,
                  'fetchClosedOrders': true,
                  'fetchTickers': true,
                  'withdraw': true,
                  'futures': false,
              },
              'extension': '.do', // appended to endpoint URL
              'timeframes': {
                  '1m': '1min',
                  '3m': '3min',
                  '5m': '5min',
                  '15m': '15min',
                  '30m': '30min',
                  '1h': '1hour',
                  '2h': '2hour',
                  '4h': '4hour',
                  '6h': '6hour',
                  '12h': '12hour',
                  '1d': '1day',
                  '3d': '3day',
                  '1w': '1week',
              },
              'api': {
                  'web': {
                      'get': [
                          'futures/pc/market/marketOverview',
                          'spot/markets/index-tickers',
                          'spot/markets/currencies',
                          'spot/markets/products',
                          'spot/markets/tickers',
                          'spot/user-level',
                      ],
                      'post': [
                          'futures/pc/market/futuresCoin',
                      ],
                  },
                  'public': {
                      'get': [
                          'depth',
                          'exchange_rate',
                          'future_depth',
                          'future_estimated_price',
                          'future_hold_amount',
                          'future_index',
                          'future_kline',
                          'future_price_limit',
                          'future_ticker',
                          'future_trades',
                          'kline',
                          'otcs',
                          'ticker',
                          'tickers',
                          'trades',
                      ],
                  },
                  'private': {
                      'post': [
                          'account_records',
                          'batch_trade',
                          'borrow_money',
                          'borrow_order_info',
                          'borrows_info',
                          'cancel_borrow',
                          'cancel_order',
                          'cancel_otc_order',
                          'cancel_withdraw',
                          'funds_transfer',
                          'future_batch_trade',
                          'future_cancel',
                          'future_devolve',
                          'future_explosive',
                          'future_order_info',
                          'future_orders_info',
                          'future_position',
                          'future_position_4fix',
                          'future_trade',
                          'future_trades_history',
                          'future_userinfo',
                          'future_userinfo_4fix',
                          'lend_depth',
                          'order_fee',
                          'order_history',
                          'order_info',
                          'orders_info',
                          'otc_order_history',
                          'otc_order_info',
                          'repayment',
                          'submit_otc_order',
                          'trade',
                          'trade_history',
                          'trade_otc_order',
                          'wallet_info',
                          'withdraw',
                          'withdraw_info',
                          'unrepayments_info',
                          'userinfo',
                      ],
                  },
              },
              'urls': {
                  'logo': 'https://user-images.githubusercontent.com/1294454/27766791-89ffb502-5ee5-11e7-8a5b-c5950b68ac65.jpg',
                  'api': {
                      'web': 'https://www.okcoin.com/v2',
                      'public': 'https://www.okcoin.com/api',
                      'private': 'https://www.okcoin.com',
                  },
                  'www': 'https://www.okcoin.com',
                  'doc': [
                      'https://www.okcoin.com/docs/en/',
                      'https://www.npmjs.com/package/okcoin.com',
                  ],
                  'referral': 'https://www.okcoin.com/account/register?flag=activity&channelId=600001513',
              },
              // these are okcoin.com fees, okex fees are in okex.js
              'fees': {
                  'trading': {
                      'taker': 0.001,
                      'maker': 0.0005,
                  },
              },
              'exceptions': {
                  // see https://github.com/okcoin-okex/API-docs-OKEx.com/blob/master/API-For-Spot-EN/Error%20Code%20For%20Spot.md
                  '10000': ExchangeError, // "Required field, can not be null"
                  '10001': DDoSProtection, // "Request frequency too high to exceed the limit allowed"
                  '10005': AuthenticationError, // "'SecretKey' does not exist"
                  '10006': AuthenticationError, // "'Api_key' does not exist"
                  '10007': AuthenticationError, // "Signature does not match"
                  '1002': InsufficientFunds, // "The transaction amount exceed the balance"
                  '1003': InvalidOrder, // "The transaction amount is less than the minimum requirement"
                  '1004': InvalidOrder, // "The transaction amount is less than 0"
                  '1013': InvalidOrder, // no contract type (PR-1101)
                  '1027': InvalidOrder, // createLimitBuyOrder(symbol, 0, 0): Incorrect parameter may exceeded limits
                  '1050': InvalidOrder, // returned when trying to cancel an order that was filled or canceled previously
                  '1217': InvalidOrder, // "Order was sent at ±5% of the current market price. Please resend"
                  '10014': InvalidOrder, // "Order price must be between 0 and 1,000,000"
                  '1009': OrderNotFound, // for spot markets, cancelling closed order
                  '1019': OrderNotFound, // order closed? ("Undo order failed")
                  '1051': OrderNotFound, // for spot markets, cancelling "just closed" order
                  '10009': OrderNotFound, // for spot markets, "Order does not exist"
                  '20015': OrderNotFound, // for future markets
                  '10008': BadRequest, // Illegal URL parameter
                  // todo: sort out below
                  // 10000 Required parameter is empty
                  // 10001 Request frequency too high to exceed the limit allowed
                  // 10002 Authentication failure
                  // 10002 System error
                  // 10003 This connection has requested other user data
                  // 10004 Request failed
                  // 10005 api_key or sign is invalid, 'SecretKey' does not exist
                  // 10006 'Api_key' does not exist
                  // 10007 Signature does not match
                  // 10008 Illegal parameter, Parameter erorr
                  // 10009 Order does not exist
                  // 10010 Insufficient funds
                  // 10011 Amount too low
                  // 10012 Only btc_usd ltc_usd supported
                  // 10013 Only support https request
                  // 10014 Order price must be between 0 and 1,000,000
                  // 10015 Order price differs from current market price too much / Channel subscription temporally not available
                  // 10016 Insufficient coins balance
                  // 10017 API authorization error / WebSocket authorization error
                  // 10018 borrow amount less than lower limit [usd:100,btc:0.1,ltc:1]
                  // 10019 loan agreement not checked
                  // 1002 The transaction amount exceed the balance
                  // 10020 rate cannot exceed 1%
                  // 10021 rate cannot less than 0.01%
                  // 10023 fail to get latest ticker
                  // 10024 balance not sufficient
                  // 10025 quota is full, cannot borrow temporarily
                  // 10026 Loan (including reserved loan) and margin cannot be withdrawn
                  // 10027 Cannot withdraw within 24 hrs of authentication information modification
                  // 10028 Withdrawal amount exceeds daily limit
                  // 10029 Account has unpaid loan, please cancel/pay off the loan before withdraw
                  // 1003 The transaction amount is less than the minimum requirement
                  // 10031 Deposits can only be withdrawn after 6 confirmations
                  // 10032 Please enabled phone/google authenticator
                  // 10033 Fee higher than maximum network transaction fee
                  // 10034 Fee lower than minimum network transaction fee
                  // 10035 Insufficient BTC/LTC
                  // 10036 Withdrawal amount too low
                  // 10037 Trade password not set
                  // 1004 The transaction amount is less than 0
                  // 10040 Withdrawal cancellation fails
                  // 10041 Withdrawal address not exsit or approved
                  // 10042 Admin password error
                  // 10043 Account equity error, withdrawal failure
                  // 10044 fail to cancel borrowing order
                  // 10047 this function is disabled for sub-account
                  // 10048 withdrawal information does not exist
                  // 10049 User can not have more than 50 unfilled small orders (amount<0.15BTC)
                  // 10050 can't cancel more than once
                  // 10051 order completed transaction
                  // 10052 not allowed to withdraw
                  // 10064 after a USD deposit, that portion of assets will not be withdrawable for the next 48 hours
                  // 1007 No trading market information
                  // 1008 No latest market information
                  // 1009 No order
                  // 1010 Different user of the cancelled order and the original order
                  // 10100 User account frozen
                  // 10101 order type is wrong
                  // 10102 incorrect ID
                  // 10103 the private otc order's key incorrect
                  // 10106 API key domain not matched
                  // 1011 No documented user
                  // 1013 No order type
                  // 1014 No login
                  // 1015 No market depth information
                  // 1017 Date error
                  // 1018 Order failed
                  // 1019 Undo order failed
                  // 10216 Non-available API / non-public API
                  // 1024 Currency does not exist
                  // 1025 No chart type
                  // 1026 No base currency quantity
                  // 1027 Incorrect parameter may exceeded limits
                  // 1028 Reserved decimal failed
                  // 1029 Preparing
                  // 1030 Account has margin and futures, transactions can not be processed
                  // 1031 Insufficient Transferring Balance
                  // 1032 Transferring Not Allowed
                  // 1035 Password incorrect
                  // 1036 Google Verification code Invalid
                  // 1037 Google Verification code incorrect
                  // 1038 Google Verification replicated
                  // 1039 Message Verification Input exceed the limit
                  // 1040 Message Verification invalid
                  // 1041 Message Verification incorrect
                  // 1042 Wrong Google Verification Input exceed the limit
                  // 1043 Login password cannot be same as the trading password
                  // 1044 Old password incorrect
                  // 1045 2nd Verification Needed
                  // 1046 Please input old password
                  // 1048 Account Blocked
                  // 1050 Orders have been withdrawn or withdrawn
                  // 1051 Order completed
                  // 1201 Account Deleted at 00: 00
                  // 1202 Account Not Exist
                  // 1203 Insufficient Balance
                  // 1204 Invalid currency
                  // 1205 Invalid Account
                  // 1206 Cash Withdrawal Blocked
                  // 1207 Transfer Not Support
                  // 1208 No designated account
                  // 1209 Invalid api
                  // 1216 Market order temporarily suspended. Please send limit order
                  // 1217 Order was sent at ±5% of the current market price. Please resend
                  // 1218 Place order failed. Please try again later
                  // 20001 User does not exist
                  // 20002 Account frozen
                  // 20003 Account frozen due to forced liquidation
                  // 20004 Contract account frozen
                  // 20005 User contract account does not exist
                  // 20006 Required field missing
                  // 20007 Illegal parameter
                  // 20008 Contract account balance is too low
                  // 20009 Contract status error
                  // 20010 Risk rate ratio does not exist
                  // 20011 Risk rate lower than 90%/80% before opening BTC position with 10x/20x leverage. or risk rate lower than 80%/60% before opening LTC position with 10x/20x leverage
                  // 20012 Risk rate lower than 90%/80% after opening BTC position with 10x/20x leverage. or risk rate lower than 80%/60% after opening LTC position with 10x/20x leverage
                  // 20013 Temporally no counter party price
                  // 20014 System error
                  // 20015 Order does not exist
                  // 20016 Close amount bigger than your open positions, liquidation quantity bigger than holding
                  // 20017 Not authorized/illegal operation/illegal order ID
                  // 20018 Order price cannot be more than 103-105% or less than 95-97% of the previous minute price
                  // 20019 IP restricted from accessing the resource
                  // 20020 Secret key does not exist
                  // 20021 Index information does not exist
                  // 20022 Wrong API interface (Cross margin mode shall call cross margin API, fixed margin mode shall call fixed margin API)
                  // 20023 Account in fixed-margin mode
                  // 20024 Signature does not match
                  // 20025 Leverage rate error
                  // 20026 API Permission Error
                  // 20027 no transaction record
                  // 20028 no such contract
                  // 20029 Amount is large than available funds
                  // 20030 Account still has debts
                  // 20038 Due to regulation, this function is not availavle in the country/region your currently reside in.
                  // 20049 Request frequency too high
                  // 20100 request time out
                  // 20101 the format of data is error
                  // 20102 invalid login
                  // 20103 event type error
                  // 20104 subscription type error
                  // 20107 JSON format error
                  // 20115 The quote is not match
                  // 20116 Param not match
                  // 21020 Contracts are being delivered, orders cannot be placed
                  // 21021 Contracts are being settled, contracts cannot be placed
              },
              'options': {
                  'marketBuyPrice': false,
                  'fetchOHLCVWarning': true,
                  'contractTypes': {
                      '1': 'this_week',
                      '2': 'next_week',
                      '4': 'quarter',
                  },
                  'fetchTickersMethod': 'fetch_tickers_from_api',
              },
          });
      }
  
      async fetchMarkets (params = {}) {
          // TODO: they have a new fee schedule as of Feb 7
          // the new fees are progressive and depend on 30-day traded volume
          // the following is the worst case
          const result = [];
          const spotResponse = await this.webGetSpotMarketsProducts ();
          //
          //     {
          //         "code": 0,
          //         "data": [
          //             {
          //                 "baseCurrency":0,
          //                 "brokerId":0,
          //                 "callAuctionOrCallNoCancelAuction":false,
          //                 "callNoCancelSwitchTime":{},
          //                 "collect":"0",
          //                 "continuousSwitchTime":{},
          //                 "groupId":1,
          //                 "isMarginOpen":true,
          //                 "listDisplay":0,
          //                 "marginRiskPreRatio":1.2,
          //                 "marginRiskRatio":1.1,
          //                 "marketFrom":118,
          //                 "maxMarginLeverage":5,
          //                 "maxPriceDigit":1,
          //                 "maxSizeDigit":8,
          //                 "mergeTypes":"0.1,1,10",
          //                 "minTradeSize":0.00100000,
          //                 "online":1,
          //                 "productId":20,
          //                 "quoteCurrency":7,
          //                 "quoteIncrement":"0.1",
          //                 "quotePrecision":2,
          //                 "sort":30038,
          //                 "symbol":"btc_usdt",
          //                 "tradingMode":3
          //             },
          //         ]
          //     }
          //
          const spotMarkets = this.safeValue (spotResponse, 'data', []);
          let markets = spotMarkets;
          if (this.has['futures']) {
              const futuresResponse = await this.webPostFuturesPcMarketFuturesCoin ();
              //
              //     {
              //         "msg":"success",
              //         "code":0,
              //         "detailMsg":"",
              //         "data": [
              //             {
              //                 "symbolId":0,
              //                 "symbol":"f_usd_btc",
              //                 "iceSingleAvgMinAmount":2,
              //                 "minTradeSize":1,
              //                 "iceSingleAvgMaxAmount":500,
              //                 "contractDepthLevel":["0.01","0.2"],
              //                 "dealAllMaxAmount":999,
              //                 "maxSizeDigit":4,
              //                 "contracts":[
              //                     { "marketFrom":34, "id":201905240000034, "type":1, "desc":"BTC0524" },
              //                     { "marketFrom":13, "id":201905310000013, "type":2, "desc":"BTC0531" },
              //                     { "marketFrom":12, "id":201906280000012, "type":4, "desc":"BTC0628" },
              //                 ],
              //                 "maxPriceDigit":2,
              //                 "nativeRate":1,
              //                 "quote":"usd",
              //                 "nativeCurrency":"usd",
              //                 "nativeCurrencyMark":"$",
              //                 "contractSymbol":0,
              //                 "unitAmount":100.00,
              //                 "symbolMark":"฿",
              //                 "symbolDesc":"BTC"
              //             },
              //         ]
              //     }
              //
              const futuresMarkets = this.safeValue (futuresResponse, 'data', []);
              markets = this.arrayConcat (spotMarkets, futuresMarkets);
          }
          for (let i = 0; i < markets.length; i++) {
              const market = markets[i];
              const id = this.safeString (market, 'symbol');
              let symbol = undefined;
              let base = undefined;
              let quote = undefined;
              let baseId = undefined;
              let quoteId = undefined;
              let baseNumericId = undefined;
              let quoteNumericId = undefined;
              let lowercaseId = undefined;
              let uppercaseBaseId = undefined;
              let uppercaseQuoteId = undefined;
              const precision = {
                  'amount': this.safeInteger (market, 'maxSizeDigit'),
                  'price': this.safeInteger (market, 'maxPriceDigit'),
              };
              const minAmount = this.safeFloat (market, 'minTradeSize');
              const minPrice = Math.pow (10, -precision['price']);
              let contracts = this.safeValue (market, 'contracts');
              if (contracts === undefined) {
                  // spot markets
                  lowercaseId = id;
                  const parts = id.split ('_');
                  baseId = parts[0];
                  quoteId = parts[1];
                  baseNumericId = this.safeInteger (market, 'baseCurrency');
                  quoteNumericId = this.safeInteger (market, 'quoteCurrency');
                  uppercaseBaseId = baseId.toUpperCase ();
                  uppercaseQuoteId = quoteId.toUpperCase ();
                  base = this.commonCurrencyCode (uppercaseBaseId);
                  quote = this.commonCurrencyCode (uppercaseQuoteId);
                  contracts = [{}];
              } else {
                  // futures markets
                  quoteId = this.safeString (market, 'quote');
                  uppercaseBaseId = this.safeString (market, 'symbolDesc');
                  uppercaseQuoteId = quoteId.toUpperCase ();
                  baseId = uppercaseBaseId.toLowerCase ();
                  lowercaseId = baseId + '_' + quoteId;
                  base = this.commonCurrencyCode (uppercaseBaseId);
                  quote = this.commonCurrencyCode (uppercaseQuoteId);
              }
              for (let k = 0; k < contracts.length; k++) {
                  const contract = contracts[k];
                  let type = this.safeString (contract, 'type', 'spot');
                  let contractType = undefined;
                  let spot = true;
                  let future = false;
                  let active = true;
                  if (type === 'spot') {
                      symbol = base + '/' + quote;
                      active = market['online'] !== 0;
                  } else {
                      const contractId = this.safeString (contract, 'id');
                      symbol = base + '-' + quote + '-' + contractId.slice (2, 8);
                      contractType = this.safeString (this.options['contractTypes'], type);
                      type = 'future';
                      spot = false;
                      future = true;
                  }
                  const fees = this.safeValue2 (this.fees, type, 'trading', {});
                  result.push (this.extend (fees, {
                      'id': id,
                      'lowercaseId': lowercaseId,
                      'contractType': contractType,
                      'symbol': symbol,
                      'base': base,
                      'quote': quote,
                      'baseId': baseId,
                      'quoteId': quoteId,
                      'baseNumericId': baseNumericId,
                      'quoteNumericId': quoteNumericId,
                      'info': market,
                      'type': 'spot',
                      'spot': spot,
                      'future': future,
                      'active': active,
                      'precision': precision,
                      'limits': {
                          'amount': {
                              'min': minAmount,
                              'max': undefined,
                          },
                          'price': {
                              'min': minPrice,
                              'max': undefined,
                          },
                          'cost': {
                              'min': minAmount * minPrice,
                              'max': undefined,
                          },
                      },
                  }));
              }
          }
          return result;
      }
  
      calculateFee (symbol, type, side, amount, price, takerOrMaker = 'taker', params = {}) {
          const market = this.markets[symbol];
          let key = 'quote';
          const rate = market[takerOrMaker];
          let cost = parseFloat (this.costToPrecision (symbol, amount * rate));
          if (side === 'sell') {
              cost *= price;
          } else {
              key = 'base';
          }
          return {
              'type': takerOrMaker,
              'currency': market[key],
              'rate': rate,
              'cost': parseFloat (this.feeToPrecision (symbol, cost)),
          };
      }
  
      async fetchTickersFromApi (symbols = undefined, params = {}) {
          await this.loadMarkets ();
          const request = {};
          const response = await this.publicGetTickers (this.extend (request, params));
          const tickers = response['tickers'];
          let timestamp = this.safeInteger (response, 'date');
          if (timestamp !== undefined) {
              timestamp *= 1000;
          }
          const result = {};
          for (let i = 0; i < tickers.length; i++) {
              let ticker = tickers[i];
              ticker = this.parseTicker (this.extend (tickers[i], { 'timestamp': timestamp }));
              const symbol = ticker['symbol'];
              result[symbol] = ticker;
          }
          return result;
      }
  
      async fetchTickersFromWeb (symbols = undefined, params = {}) {
          await this.loadMarkets ();
          const request = {};
          const response = await this.webGetSpotMarketsTickers (this.extend (request, params));
          const tickers = this.safeValue (response, 'data');
          const result = {};
          for (let i = 0; i < tickers.length; i++) {
              const ticker = this.parseTicker (tickers[i]);
              const symbol = ticker['symbol'];
              result[symbol] = ticker;
          }
          return result;
      }
  
      async fetchTickers (symbols = undefined, params = {}) {
          const method = this.options['fetchTickersMethod'];
          return await this[method] (symbols, params);
      }
  
      async fetchOrderBook (symbol = undefined, limit = undefined, params = {}) {
          await this.loadMarkets ();
          const market = this.market (symbol);
          const method = market['future'] ? 'publicGetFutureDepth' : 'publicGetDepth';
          const request = this.createRequest (market, params);
          if (limit !== undefined) {
              request['size'] = limit;
          }
          const response = await this[method] (request);
          return this.parseOrderBook (response);
      }
  
      parseTicker (ticker, market = undefined) {
          //
          //     {              buy:   "48.777300",
          //                 change:   "-1.244500",
          //       changePercentage:   "-2.47%",
          //                  close:   "49.064000",
          //            createdDate:    1531704852254,
          //             currencyId:    527,
          //                dayHigh:   "51.012500",
          //                 dayLow:   "48.124200",
          //                   high:   "51.012500",
          //                inflows:   "0",
          //                   last:   "49.064000",
          //                    low:   "48.124200",
          //             marketFrom:    627,
          //                   name: {  },
          //                   open:   "50.308500",
          //               outflows:   "0",
          //              productId:    527,
          //                   sell:   "49.064000",
          //                 symbol:   "zec_okb",
          //                 volume:   "1049.092535"   }
          //
          const timestamp = this.safeInteger2 (ticker, 'timestamp', 'createdDate');
          let symbol = undefined;
          if (market === undefined) {
              if ('symbol' in ticker) {
                  const marketId = ticker['symbol'];
                  if (marketId in this.markets_by_id) {
                      market = this.markets_by_id[marketId];
                  } else {
                      const [ baseId, quoteId ] = ticker['symbol'].split ('_');
                      let base = baseId.toUpperCase ();
                      let quote = quoteId.toUpperCase ();
                      base = this.commonCurrencyCode (base);
                      quote = this.commonCurrencyCode (quote);
                      symbol = base + '/' + quote;
                  }
              }
          }
          if (market !== undefined) {
              symbol = market['symbol'];
          }
          const last = this.safeFloat (ticker, 'last');
          const open = this.safeFloat (ticker, 'open');
          const change = this.safeFloat (ticker, 'change');
          const percentage = this.safeFloat (ticker, 'changePercentage');
          return {
              'symbol': symbol,
              'timestamp': timestamp,
              'datetime': this.iso8601 (timestamp),
              'high': this.safeFloat (ticker, 'high'),
              'low': this.safeFloat (ticker, 'low'),
              'bid': this.safeFloat (ticker, 'buy'),
              'bidVolume': undefined,
              'ask': this.safeFloat (ticker, 'sell'),
              'askVolume': undefined,
              'vwap': undefined,
              'open': open,
              'close': last,
              'last': last,
              'previousClose': undefined,
              'change': change,
              'percentage': percentage,
              'average': undefined,
              'baseVolume': this.safeFloat2 (ticker, 'vol', 'volume'),
              'quoteVolume': undefined,
              'info': ticker,
          };
      }
  
      async fetchTicker (symbol = undefined, params = {}) {
          await this.loadMarkets ();
          const market = this.market (symbol);
          const method = market['future'] ? 'publicGetFutureTicker' : 'publicGetTicker';
          const request = this.createRequest (market, params);
          const response = await this[method] (request);
          let ticker = this.safeValue (response, 'ticker');
          if (ticker === undefined) {
              throw new ExchangeError (this.id + ' fetchTicker returned an empty response: ' + this.json (response));
          }
          let timestamp = this.safeInteger (response, 'date');
          if (timestamp !== undefined) {
              timestamp *= 1000;
              ticker = this.extend (ticker, { 'timestamp': timestamp });
          }
          return this.parseTicker (ticker, market);
      }
  
      parseTrade (trade, market = undefined) {
          let symbol = undefined;
          if (market) {
              symbol = market['symbol'];
          }
          const timestamp = this.safeInteger (trade, 'date_ms');
          return {
              'info': trade,
              'timestamp': timestamp,
              'datetime': this.iso8601 (timestamp),
              'symbol': symbol,
              'id': this.safeString (trade, 'tid'),
              'order': undefined,
              'type': undefined,
              'side': trade['type'],
              'price': this.safeFloat (trade, 'price'),
              'amount': this.safeFloat (trade, 'amount'),
          };
      }
  
      async fetchTrades (symbol, since = undefined, limit = undefined, params = {}) {
          await this.loadMarkets ();
          const market = this.market (symbol);
          const method = market['future'] ? 'publicGetFutureTrades' : 'publicGetTrades';
          const request = this.createRequest (market, params);
          const response = await this[method] (request);
          return this.parseTrades (response, market, since, limit);
      }
  
      parseOHLCV (ohlcv, market = undefined, timeframe = '1m', since = undefined, limit = undefined) {
          const numElements = ohlcv.length;
          const volumeIndex = (numElements > 6) ? 6 : 5;
          return [
              ohlcv[0], // timestamp
              parseFloat (ohlcv[1]), // Open
              parseFloat (ohlcv[2]), // High
              parseFloat (ohlcv[3]), // Low
              parseFloat (ohlcv[4]), // Close
              // parseFloat (ohlcv[5]), // quote volume
              // parseFloat (ohlcv[6]), // base volume
              parseFloat (ohlcv[volumeIndex]), // okex will return base volume in the 7th element for future markets
          ];
      }
  
      async fetchOHLCV (symbol, timeframe = '1m', since = undefined, limit = undefined, params = {}) {
          await this.loadMarkets ();
          const market = this.market (symbol);
          const method = market['future'] ? 'publicGetFutureKline' : 'publicGetKline';
          const request = this.createRequest (market, {
              'type': this.timeframes[timeframe],
              // 'since': since === undefined ? this.milliseconds () - 86400000 : since,  // default last 24h
          });
          if (since !== undefined) {
              request['since'] = this.milliseconds () - 86400000; // default last 24h
          }
          if (limit !== undefined) {
              if (this.options['fetchOHLCVWarning']) {
                  throw new ExchangeError (this.id + ' fetchOHLCV counts "limit" candles from current time backwards, therefore the "limit" argument for ' + this.id + ' is disabled. Set ' + this.id + '.options["fetchOHLCVWarning"] = false to suppress this warning message.');
              }
              request['size'] = parseInt (limit); // max is 1440 candles
          }
          const response = await this[method] (this.extend (request, params));
          return this.parseOHLCVs (response, market, timeframe, since, limit);
      }
  
      async fetchBalance (params = {}) {
          await this.loadMarkets ();
          const response = await this.privatePostUserinfo (params);
          const info = this.safeValue (response, 'info', {});
          const balances = this.safeValue (info, 'funds', {});
          const result = { 'info': response };
          let ids = Object.keys (balances['free']);
          let usedField = 'freezed';
          // wtf, okex?
          // https://github.com/okcoin-okex/API-docs-OKEx.com/commit/01cf9dd57b1f984a8737ef76a037d4d3795d2ac7
          if (!(usedField in balances)) {
              usedField = 'holds';
          }
          const usedKeys = Object.keys (balances[usedField]);
          ids = this.arrayConcat (ids, usedKeys);
          for (let i = 0; i < ids.length; i++) {
              const id = ids[i];
              let code = id.toUpperCase ();
              if (id in this.currencies_by_id) {
                  code = this.currencies_by_id[id]['code'];
              } else {
                  code = this.commonCurrencyCode (code);
              }
              const account = this.account ();
              account['free'] = this.safeFloat (balances['free'], id, 0.0);
              account['used'] = this.safeFloat (balances[usedField], id, 0.0);
              account['total'] = this.sum (account['free'], account['used']);
              result[code] = account;
          }
          return this.parseBalance (result);
      }
  
      async createOrder (symbol, type, side, amount, price = undefined, params = {}) {
          await this.loadMarkets ();
          const market = this.market (symbol);
          const method = market['future'] ? 'privatePostFutureTrade' : 'privatePostTrade';
          const orderSide = (type === 'market') ? (side + '_market') : side;
          const isMarketBuy = ((market['spot']) && (type === 'market') && (side === 'buy') && (!this.options['marketBuyPrice']));
          const orderPrice = isMarketBuy ? this.safeFloat (params, 'cost') : price;
          const request = this.createRequest (market, {
              'type': orderSide,
              'amount': amount,
              'price': orderPrice,
          });
          if (market['future']) {
              request['match_price'] = 0; // match best counter party price? 0 or 1, ignores price if 1
              request['lever_rate'] = 10; // leverage rate value: 10 or 20 (10 by default)
          } else if (type === 'market' && side === 'buy' && !request['price']) {
              if (this.options['marketBuyPrice']) {
                  // eslint-disable-next-line quotes
                  throw new ExchangeError (this.id + " market buy orders require a price argument (the amount you want to spend or the cost of the order) when this.options['marketBuyPrice'] is true.");
              } else {
                  // eslint-disable-next-line quotes
                  throw new ExchangeError (this.id + " market buy orders require an additional cost parameter, cost = price * amount. If you want to pass the cost of the market order (the amount you want to spend) in the price argument (the default " + this.id + " behaviour), set this.options['marketBuyPrice'] = true. It will effectively suppress this warning exception as well.");
              }
          }
          params = this.omit (params, 'cost');
          const response = await this[method] (this.extend (request, params));
          const timestamp = this.milliseconds ();
          return {
              'info': response,
              'id': this.safeString (response, 'order_id'),
              'timestamp': timestamp,
              'datetime': this.iso8601 (timestamp),
              'lastTradeTimestamp': undefined,
              'status': undefined,
              'symbol': symbol,
              'type': type,
              'side': side,
              'price': price,
              'amount': amount,
              'filled': undefined,
              'remaining': undefined,
              'cost': undefined,
              'trades': undefined,
              'fee': undefined,
          };
      }
  
      async cancelOrder (id, symbol = undefined, params = {}) {
          if (symbol === undefined) {
              throw new ArgumentsRequired (this.id + ' cancelOrder() requires a symbol argument');
          }
          await this.loadMarkets ();
          const market = this.market (symbol);
          const method = market['future'] ? 'privatePostFutureCancel' : 'privatePostCancelOrder';
          const request = this.createRequest (market, {
              'order_id': id,
          });
          const response = await this[method] (this.extend (request, params));
          return response;
      }
  
      parseOrderStatus (status) {
          const statuses = {
              '-1': 'canceled',
              '0': 'open',
              '1': 'open',
              '2': 'closed',
              '3': 'open',
              '4': 'canceled',
          };
          return this.safeValue (statuses, status, status);
      }
  
      parseOrderSide (side) {
          if (side === 1) {
              return 'buy'; // open long position
          } else if (side === 2) {
              return 'sell'; // open short position
          } else if (side === 3) {
              return 'sell'; // liquidate long position
          } else if (side === 4) {
              return 'buy'; // liquidate short position
          }
          return side;
      }
  
      parseOrder (order, market = undefined) {
          let side = undefined;
          let type = undefined;
          if ('type' in order) {
              if ((order['type'] === 'buy') || (order['type'] === 'sell')) {
                  side = order['type'];
                  type = 'limit';
              } else if (order['type'] === 'buy_market') {
                  side = 'buy';
                  type = 'market';
              } else if (order['type'] === 'sell_market') {
                  side = 'sell';
                  type = 'market';
              } else {
                  side = this.parseOrderSide (order['type']);
                  if (('contract_name' in order) || ('lever_rate' in order)) {
                      type = 'margin';
                  }
              }
          }
          const status = this.parseOrderStatus (this.safeString (order, 'status'));
          let symbol = undefined;
          if (market === undefined) {
              const marketId = this.safeString (order, 'symbol');
              if (marketId in this.markets_by_id) {
                  market = this.markets_by_id[marketId];
              }
          }
          if (market) {
              symbol = market['symbol'];
          }
          const createDateField = this.getCreateDateField ();
          const timestamp = this.safeInteger (order, createDateField);
          let amount = this.safeFloat (order, 'amount');
          const filled = this.safeFloat (order, 'deal_amount');
          amount = Math.max (amount, filled);
          let remaining = Math.max (0, amount - filled);
          if (type === 'market') {
              remaining = 0;
          }
          let average = this.safeFloat (order, 'avg_price');
          // https://github.com/ccxt/ccxt/issues/2452
          average = this.safeFloat (order, 'price_avg', average);
          const cost = average * filled;
          return {
              'info': order,
              'id': this.safeString (order, 'order_id'),
              'timestamp': timestamp,
              'datetime': this.iso8601 (timestamp),
              'lastTradeTimestamp': undefined,
              'symbol': symbol,
              'type': type,
              'side': side,
              'price': this.safeFloat (order, 'price'),
              'average': average,
              'cost': cost,
              'amount': amount,
              'filled': filled,
              'remaining': remaining,
              'status': status,
              'fee': undefined,
          };
      }
  
      getCreateDateField () {
          // needed for derived exchanges
          // allcoin typo create_data instead of create_date
          return 'create_date';
      }
  
      getOrdersField () {
          // needed for derived exchanges
          // allcoin typo order instead of orders (expected based on their API docs)
          return 'orders';
      }
  
      async fetchOrder (id, symbol = undefined, params = {}) {
          if (symbol === undefined) {
              throw new ExchangeError (this.id + ' fetchOrder requires a symbol argument');
          }
          await this.loadMarkets ();
          const market = this.market (symbol);
          const method = market['future'] ? 'privatePostFutureOrderInfo' : 'privatePostOrderInfo';
          const request = this.createRequest (market, {
              'order_id': id,
              // 'status': 0, // 0 for unfilled orders, 1 for filled orders
              // 'current_page': 1, // current page number
              // 'page_length': 200, // number of orders returned per page, maximum 200
          });
          const response = await this[method] (this.extend (request, params));
          const ordersField = this.getOrdersField ();
          const numOrders = response[ordersField].length;
          if (numOrders > 0) {
              return this.parseOrder (response[ordersField][0]);
          }
          throw new OrderNotFound (this.id + ' order ' + id + ' not found');
      }
  
      async fetchOrders (symbol = undefined, since = undefined, limit = undefined, params = {}) {
          if (symbol === undefined) {
              throw new ExchangeError (this.id + ' fetchOrders requires a symbol argument');
          }
          await this.loadMarkets ();
          const market = this.market (symbol);
          let method = market['future'] ? 'privatePostFutureOrdersInfo' : 'privatePost';
          let request = this.createRequest (market);
          const order_id_in_params = ('order_id' in params);
          if (market['future']) {
              if (!order_id_in_params) {
                  throw new ExchangeError (this.id + ' fetchOrders() requires order_id param for futures market ' + symbol + ' (a string of one or more order ids, comma-separated)');
              }
          } else {
              const status = ('type' in params) ? params['type'] : params['status'];
              if (typeof status === 'undefined') {
                  const name = order_id_in_params ? 'type' : 'status';
                  throw new ExchangeError (this.id + ' fetchOrders() requires ' + name + ' param for spot market ' + symbol + ' (0 - for unfilled orders, 1 - for filled/canceled orders)');
              }
              if (order_id_in_params) {
                  method += 'OrdersInfo';
                  request = this.extend (request, {
                      'type': status,
                      'order_id': params['order_id'],
                  });
              } else {
                  method += 'OrderHistory';
                  request = this.extend (request, {
                      'status': status,
                      'current_page': 1, // current page number
                      'page_length': 200, // number of orders returned per page, maximum 200
                  });
              }
              params = this.omit (params, [ 'type', 'status' ]);
          }
          const response = await this[method] (this.extend (request, params));
          const ordersField = this.getOrdersField ();
          return this.parseOrders (response[ordersField], market, since, limit);
      }
  
      async fetchOpenOrders (symbol = undefined, since = undefined, limit = undefined, params = {}) {
          const request = {
              'status': 0, // 0 for unfilled orders, 1 for filled orders
          };
          return await this.fetchOrders (symbol, since, limit, this.extend (request, params));
      }
  
      async fetchClosedOrders (symbol = undefined, since = undefined, limit = undefined, params = {}) {
          const request = {
              'status': 1, // 0 for unfilled orders, 1 for filled orders
          };
          return await this.fetchOrders (symbol, since, limit, this.extend (request, params));
      }
  
      async withdraw (code, amount, address, tag = undefined, params = {}) {
          this.checkAddress (address);
          await this.loadMarkets ();
          const currency = this.currency (code);
          // if (amount < 0.01)
          //     throw new ExchangeError (this.id + ' withdraw() requires amount > 0.01');
          // for some reason they require to supply a pair of currencies for withdrawing one currency
          const currencyId = currency['id'] + '_usd';
          if (tag) {
              address = address + ':' + tag;
          }
          const request = {
              'symbol': currencyId,
              'withdraw_address': address,
              'withdraw_amount': amount,
              'target': 'address', // or 'okcn', 'okcom', 'okex'
          };
          let query = params;
          if ('chargefee' in query) {
              request['chargefee'] = query['chargefee'];
              query = this.omit (query, 'chargefee');
          } else {
              throw new ExchangeError (this.id + ' withdraw() requires a `chargefee` parameter');
          }
          if (this.password) {
              request['trade_pwd'] = this.password;
          } else if ('password' in query) {
              request['trade_pwd'] = query['password'];
              query = this.omit (query, 'password');
          } else if ('trade_pwd' in query) {
              request['trade_pwd'] = query['trade_pwd'];
              query = this.omit (query, 'trade_pwd');
          }
          const passwordInRequest = ('trade_pwd' in request);
          if (!passwordInRequest) {
              throw new ExchangeError (this.id + ' withdraw() requires this.password set on the exchange instance or a password / trade_pwd parameter');
          }
          const response = await this.privatePostWithdraw (this.extend (request, query));
          return {
              'info': response,
              'id': this.safeString (response, 'withdraw_id'),
          };
      }
  
      sign (path, api = 'public', method = 'GET', params = {}, headers = undefined, body = undefined) {
          let url = '/';
          if (api !== 'web') {
              url += this.version + '/';
          }
          url += path;
          if (api !== 'web') {
              url += this.extension;
          }
          if (api === 'private') {
              this.checkRequiredCredentials ();
              const query = this.keysort (this.extend ({
                  'api_key': this.apiKey,
              }, params));
              // secret key must be at the end of query
              const queryString = this.rawencode (query) + '&secret_key=' + this.secret;
              query['sign'] = this.hash (this.encode (queryString)).toUpperCase ();
              body = this.urlencode (query);
              headers = { 'Content-Type': 'application/x-www-form-urlencoded' };
          } else {
              if (Object.keys (params).length) {
                  url += '?' + this.urlencode (params);
              }
          }
          url = this.urls['api'][api] + url;
          return { 'url': url, 'method': method, 'body': body, 'headers': headers };
      }
  
      createRequest (market, params = {}) {
          if (market['future']) {
              return this.deepExtend ({
                  'symbol': market['lowercaseId'],
                  'contract_type': market['contractType'],
              });
          }
          return this.deepExtend ({
              'symbol': market['id'],
          }, params);
      }
  
      handleErrors (code, reason, url, method, headers, body, response) {
          if (response === undefined) {
              return; // fallback to default error handler
          }
          if ('error_code' in response) {
              const error = this.safeString (response, 'error_code');
              const message = this.id + ' ' + this.json (response);
              if (error in this.exceptions) {
                  const ExceptionClass = this.exceptions[error];
                  throw new ExceptionClass (message);
              } else {
                  throw new ExchangeError (message);
              }
          }
          if ('result' in response) {
              if (!response['result']) {
                  throw new ExchangeError (this.id + ' ' + this.json (response));
              }
          }
      }
  };
  