// 入力パラメータ
input double ATR_Multiplier = 1.5;    // ATR乗数係数
input int    ATR_Period = 7;          // ATR期間

// グローバル変数
int atrHandle;  // ATRインジケーターハンドル

//+------------------------------------------------------------------+
//| Expert initialization function                                   |
//+------------------------------------------------------------------+
int OnInit()
  {
   // ATRインジケーターハンドルを取得
   atrHandle = iATR(_Symbol, _Period, ATR_Period);
   if(atrHandle == INVALID_HANDLE)
     {
      Print("Failed to create ATR handle");
      return(INIT_FAILED);
     }
   return(INIT_SUCCEEDED);
  }

//+------------------------------------------------------------------+
//| Expert deinitialization function                                 |
//+------------------------------------------------------------------+
void OnDeinit(const int reason)
  {
   // インジケーターハンドルの解放
   if(atrHandle != INVALID_HANDLE)
      IndicatorRelease(atrHandle);
  }

//+------------------------------------------------------------------+
//| Expert tick function                                             |
//+------------------------------------------------------------------+
void OnTick()
  {
   // ポジションがあるか確認
   bool hasPosition = false;
   for(int i = PositionsTotal()-1; i >= 0; i--)
     {
      if(PositionGetSymbol(i) == _Symbol)
        {
         hasPosition = true;
         ulong ticket = PositionGetInteger(POSITION_TICKET);
         ENUM_POSITION_TYPE posType = (ENUM_POSITION_TYPE)PositionGetInteger(POSITION_TYPE);
         TrailStop(ticket, posType);
        }
     }
  }

//+------------------------------------------------------------------+
//| トレーリングストップを実行                                       |
//+------------------------------------------------------------------+
void TrailStop(ulong ticket, ENUM_POSITION_TYPE positionType)
  {
   double atr[1];
   if(CopyBuffer(atrHandle, 0, 0, 1, atr) <= 0)
     {
      Print("Failed to get ATR value: ", GetLastError());
      return;
     }
   
   double newStop = 0;
   double currentStop = PositionGetDouble(POSITION_SL);
   double ask = SymbolInfoDouble(_Symbol, SYMBOL_ASK);
   double bid = SymbolInfoDouble(_Symbol, SYMBOL_BID);
   
   if(positionType == POSITION_TYPE_BUY)
     {
      newStop = bid - (atr[0] * ATR_Multiplier);
      newStop = NormalizeDouble(newStop, _Digits);
      
      // 現在のストップロスより有利な場合のみ更新
      if(newStop > currentStop || currentStop == 0)
         ModifyStopLoss(ticket, newStop);
     }
   else if(positionType == POSITION_TYPE_SELL)
     {
      newStop = ask + (atr[0] * ATR_Multiplier);
      newStop = NormalizeDouble(newStop, _Digits);
      
      // 現在のストップロスより有利な場合のみ更新
      if(newStop < currentStop || currentStop == 0)
         ModifyStopLoss(ticket, newStop);
     }
  }

//+------------------------------------------------------------------+
//| ストップロスを変更                                               |
//+------------------------------------------------------------------+
void ModifyStopLoss(ulong ticket, double newStop)
  {
   MqlTradeRequest request = {};
   request.action       = TRADE_ACTION_SLTP;
   request.position    = ticket;
   request.symbol      = _Symbol;
   request.sl          = newStop;
   request.tp          = PositionGetDouble(POSITION_TP);
   
   MqlTradeResult result = {};
   if(OrderSend(request, result))
     {
      Print("Stop loss updated to ", newStop);
     }
  }
//+------------------------------------------------------------------+