using System;
using System.Collections.Generic;
using System.Text;

namespace XCode
{
    /// <summary>逗号连接表达式</summary>
    public class ConcatExpression : Expression
    {
        #region 属性
        /// <summary>内置字符串</summary>
        public StringBuilder Builder { get; set; } = new StringBuilder();
        #endregion

        #region 构造
        /// <summary>实例化</summary>
        public ConcatExpression() { }

        /// <summary>实例化</summary>
        /// <param name="exp"></param>
        public ConcatExpression(String exp) { Builder.Append(exp + ""); }
        #endregion

        #region 方法
        /// <summary>增加</summary>
        /// <param name="exp"></param>
        /// <returns></returns>
        public ConcatExpression And(String exp)
        {
            if (String.IsNullOrEmpty(exp)) return this;

            Builder.Separate(",").Append(exp);

            return this;
        }

        /// <summary>已重载。</summary>
        /// <param name="needBracket">外部是否需要括号。如果外部要求括号，而内部又有Or，则加上括号</param>
        /// <param name="ps">参数字典</param>
        /// <returns></returns>
        public override String GetString(Boolean needBracket, IDictionary<String, Object> ps)
        {
            if (Builder == null || Builder.Length <= 0) return null;

            return Builder.ToString();
        }
        #endregion

        #region 重载运算符
        /// <summary>重载运算符实现And操作，同时通过布尔型支持AndIf</summary>
        /// <param name="exp"></param>
        /// <param name="value">数值</param>
        /// <returns></returns>
        public static ConcatExpression operator &(ConcatExpression exp, String value)
        {
            if (value == null) return exp;

            exp.And(value);

            return exp;
        }
        #endregion
    }
}