using System.Text;

namespace DS.WMS.Core.Application.Dtos
{
    /// <summary>
    /// 可将指定金额的数字转换为人民币大写
    /// </summary>
    public sealed class Money
    {
        const string Yuan = "元";                        // “元”，可以改为“圆”、“卢布”之类
        const string Jiao = "角";                        // “角”，可以改为“拾”
        const string Fen = "分";                        // “分”，可以改为“美分”之类
        const string Digit = "零壹贰叁肆伍陆柒捌玖";      // 大写数字
        bool isAllZero = true;                        // 片段内是否全零
        bool isPreZero = true;                        // 低一位数字是否是零
        bool Overflow = false;                       // 溢出标志
        long money100;                                   // 金额*100，即以“分”为单位的金额
        long value;                                      // money100的绝对值
        StringBuilder sb = new StringBuilder();         // 大写金额字符串，逆序
                                                        // 只读属性: "零元"
        readonly string[] Unit = [Yuan, "万", "亿", "万", "亿亿"];

        public string ZeroString { get { return Digit[0] + Yuan; } }

        /// <summary>
        /// 初始化
        /// </summary>
        /// <param name="value"></param>
        public Money(double value) : this(Convert.ToDecimal(value))
        {
        }

        /// <summary>
        /// 初始化
        /// </summary>
        /// <param name="value"></param>
        public Money(decimal value)
        {
            try { money100 = (long)(value * 100m); }
            catch { Overflow = true; }

            if (money100 == long.MinValue)
                Overflow = true;
        }

        /// <summary>
        /// 返回汉字大写金额
        /// </summary>
        /// <returns>大写金额字符串</returns>
        /// <exception cref="OverflowException">金额超出范围</exception>
        public override string ToString()
        {
            if (Overflow) throw new OverflowException("金额超出范围");
            if (money100 == 0) return ZeroString;

            value = Math.Abs(money100);
            ParseSection(true);
            for (int i = 0; i < Unit.Length && value > 0; i++)
            {
                if (isPreZero && !isAllZero) sb.Append(Digit[0]);
                if (i == 4 && sb.ToString().EndsWith(Unit[2]))
                    sb.Remove(sb.Length - Unit[2].Length, Unit[2].Length);
                sb.Append(Unit[i]);
                ParseSection(false);
                if ((i % 2) == 1 && isAllZero)
                    sb.Remove(sb.Length - Unit[i].Length, Unit[i].Length);
            }
            if (money100 < 0) sb.Append("负");

            var str = Reverse();
            if (money100 % 100 == 0)
                str += "整";

            return str;
        }

        // 解析“片段”: “角分(2位)”或“万以内的一段(4位)”
        void ParseSection(bool isJiaoFen)
        {
            string[] Unit = isJiaoFen ?
              new string[] { Fen, Jiao } :
              new string[] { "", "拾", "佰", "仟" };
            isAllZero = true;
            for (int i = 0; i < Unit.Length && value > 0; i++)
            {
                int d = (int)(value % 10);
                if (d != 0)
                {
                    if (isPreZero && !isAllZero) sb.Append(Digit[0]);
                    sb.AppendFormat("{0}{1}", Unit[i], Digit[d]);
                    isAllZero = false;
                }
                isPreZero = (d == 0);
                value /= 10;
            }
        }

        // 反转字符串
        string Reverse()
        {
            StringBuilder sbReversed = new StringBuilder();
            for (int i = sb.Length - 1; i >= 0; i--)
                sbReversed.Append(sb[i]);
            return sbReversed.ToString();
        }
    }
}