using IwbZero.Expr;
using IwbZero.ToolCommon.StringModel;

namespace IwbZero.ExprFunctions.Functions
{
    /// <summary>
    /// Sub字符串
    /// </summary>
    public class FunSubStr:IIwbFunction
    {
        public string Invoke(ExprObject exprObj)
        {
            string text = "";
            ExprObject child = exprObj.GetChild(0);
            if (child != null)
            {
                text = child.Expr;
                child = exprObj.GetChild(2);
                if (child != null)
                {
                    int num = child.Expr.ValI();
                    int num2 = text.Length;
                    string text2 = "L";
                    child = exprObj.GetChild(4);
                    if (child != null)
                    {
                        num2 = child.Expr.ValI();
                        if (num2 == 0)
                        {
                            var  text3 = child.Expr.ToUpper();
                            text2 = text3 == "R" ? "R" : "L";
                        }
                    }
                    var child2 = exprObj.GetChild(6);
                    if (child2 != null)
                    {
                        text2 = child2.Expr.ToUpper();
                    }
                    if (num < 0)
                    {
                        num = 0;
                    }
                    if (num < text.Length)
                    {
                        if (text2 == "R")
                        {
                            text = text.Substring(0, text.Length - num);
                            if (child2 == null)
                            {
                                return text;
                            }
                            num = text.Length - num2;
                            if (num < 0)
                            {
                                num = 0;
                            }
                        }
                        if (num2 + num > text.Length)
                        {
                            num2 = text.Length - num;
                        }
                        text = text.Substring(num, num2);
                    }
                    else
                    {
                        text = "";
                    }
                }
            }
            return text;
        }
    }
}