/// <summary>
/// 定义命令基类
/// </summary>
public class CommandBase
{
   protected POS _POS;
   
   /// <summary>
   /// 执行命令
   /// </summary>
   public virtual void Execute() { }
}

/// <summary>
/// NULL Object 模式
/// </summary>
public class CommandNull : CommandBase
{
   public override void Execute()
   {
      MessageBox.Show("输入非法命令！");
   }
}

/// <summary>
/// 输入货品, 检测输入的命令是货品编号
/// </summary>
public class CommandInputStock : CommandBase
{
   private Stock _stock;
   
   public CommandInputStock(POS pos, Stock stock)
   {
      _POS = pos;
      _stock = stock;
   }
   
   public override void Execute()
   {
      _POS.InputStock(_stock);
   }
}

/// <summary>
/// 收银命令,进入收银状态
/// </summary>
public class CommandSetReceiveMode : CommandBase
{
   public CommandSetReceiveMode(POS pos)
   {
      _POS = pos;
   }
   
   public override void Execute()
   {
      _POS.SetReceiveMode();
   }
}

/// <summary>
/// 输入收银金额
/// </summary>
public class CommandReceiveMoney : CommandBase
{
   private decimal _money = 0;
   
   public CommandReceiveMoney(POS pos, decimal money)
   {
      _POS = pos;
      _money = money;
   }
   
   public override void Execute()
   {
      _POS.ReceiveMoney(_money);
   }
}

// 来源:www.CSFramework.com, C/S结构框架学习网

/// <summary>
/// 打印小票命令
/// </summary>
public class CommandPrintBill : CommandBase
{
   public CommandPrintBill(POS pos)
   {
      _POS = pos;
   }
   
   public override void Execute()
   {
      _POS.PrintBill();
   }
}


// 来源:www.CSFramework.com, C/S结构框架学习网

/// <summary>
/// 收银/结帐命令
/// </summary>
public class CommandCheckOut : CommandBase
{
   public CommandCheckOut(POS pos)
   {
      _POS = pos;
   }
   
   public override void Execute()
   {
      _POS.CheckOut();
   }
}

// 来源:www.CSFramework.com, C/S结构框架学习网

/// <summary>
/// 取消当前交易
/// </summary>
public class CommandCancelTransaction : CommandBase
{
   public CommandCancelTransaction(POS pos)
   {
      _POS = pos;
   }
   
   public override void Execute()
   {
      if (DialogResult.Yes == MessageBox.Show("要取消交易吗?", "确认程序", MessageBoxButtons.YesNo))
      {
         _POS.Reset();
      }
   }
}

/// <summary>
/// 退出系统命令
/// </summary>
public class CommandExit : CommandBase
{
   public CommandExit(POS pos)
   {
      _POS = pos;
   }
   
   public override void Execute()
   {
      if (DialogResult.Yes == MessageBox.Show("要退出系统吗?", "确认程序", MessageBoxButtons.YesNo))
      {
         Application.Exit();
      }
   }
}

/// <summary>
/// 由收银台输入货品编号，返回Stock实体对象。
/// 这里可以从SQL Server取数。
/// </summary>
public class POS
{
   private ucMonitor _Monitor; //收银显示屏
   private IList _StockList = new ArrayList(); //货品列表
   
   private decimal _ReceivedMoney = 0; //客户支付(现金或借记卡)的金额
   private decimal _ReceivableTotal = 0;//客户应付金额
   
   private bool _ReceiveMode = false;
   public bool IsReceiveMode { get { return _ReceiveMode; } }
   
   public POS(ucMonitor monitor)
   {
      _Monitor = monitor;
      
      this.Reset();
   }
   
   /// <summary>
   /// 重设收银台
   /// </summary>
   public void Reset()
   {
      _ReceiveMode = false;
      _ReceivedMoney = 0;
      _ReceivableTotal = 0;
      _StockList.Clear();
      _Monitor.ShowWelcome();
      _Monitor.ShowStatus(PosMode.InputStock);
   }
   
   /// <summary>
   /// 检测输入命令
   /// </summary>
   public CommandBase ParseCommand(string commandString)
   {
      //首长检查输入的命令是否货品编号
      Stock stock = this.GetStock(commandString);
      
      if (stock != null)
      return new CommandInputStock(this, stock);
      else
      return CommandFactory.CreateCommand(this, commandString);
   }
   
   //测试用.可创建两个货品对象
   private Stock GetStock(string code)
   {
      code = code.ToUpper();
      if (code == "VC".ToUpper())
      return new Stock("Vit.C", decimal.Parse("5.8"));
      else if (code == "PP".ToUpper())
      return new Stock("Panicilin", decimal.Parse("15.20"));
      else
      return null;
   }
   
   // 这里可以从SQL Server取数。
   private static Stock GetStockFromSQL(string code)
   {
      //连接SQL Server.查询记录，返回Datarow,将Datarow 转换为Stock
      return null;
   }
   
   /// <summary>
   /// 输入货品
   /// </summary>
   /// <param name="stock"></param>
   public void InputStock(Stock stock)
   {
      _StockList.Add(stock);
      
      //累加应收金额
      _ReceivableTotal = stock.Price;
      
      _Monitor.ShowCurrentStock(stock);
   }
   
   /// <summary>
   /// 结帐
   /// </summary>
   public void CheckOut()
   {
      if (_ReceivedMoney > 0 || _ReceivableTotal > 0)
      {
         if (_ReceivedMoney >= _ReceivableTotal)
         {
            this.PrintBill();//打印小票
            this.Reset(); //处理下一位客户
            MessageBox.Show("打印完毕，处理下一位客户。");
         }
         else
         {
            MessageBox.Show("金额不足，不能结帐....");
         }
      }
      else
      {
         MessageBox.Show("大哥，没有输入货品，不能结帐！");
      }
   }
   
   /// <summary>
   /// 打印小票
   /// </summary>
   public void PrintBill()
   {
      string msg = string.Format("总共{0}个货品\r\n\r\n正在打印小票...", _StockList.Count);
      MessageBox.Show(msg);
   }
   
   /// <summary>
   /// 设置收银模式
   /// </summary>
   public void SetReceiveMode()
   {
      _ReceiveMode = true;
      _Monitor.ShowStatus(PosMode.CheckBill);
   }
   
   /// <summary>
   /// 收款
   /// </summary>
   /// <param name="money"></param>
   public void ReceiveMoney(decimal money)
   {
      _ReceivedMoney = money;
      _Monitor.ShowReceive(money);
   }
}

// 来源:www.CSFramework.com, C/S结构框架学习网