using System;
using System.Text;

namespace Znyc.Recruitment.Admin.Commons
{
    /// <summary>
    /// 过滤表情符号帮助类
    /// </summary>
    public class EmojiFilterHelper
    {
        /// <summary>
        /// 检测是否有emoji字符
        /// </summary>
        /// <param name="source"></param>
        /// <returns>一旦含有就抛出</returns>
        public static Boolean ContainsEmoji(string source)
        {
            char[] item = source.ToCharArray();
            for (int i = 0; i < source.Length; i++)
            {
                if (IsEmojiCharacter(item[i]))
                    return true; //do nothing，判断到了这里表明，确认有表情字符
            }
            return false;
        }

        private static Boolean IsEmojiCharacter(char codePoint)
        {
            return (codePoint == 0x0) ||
                    (codePoint == 0x9) ||
                    (codePoint == 0xA) ||
                    (codePoint == 0xD) ||
                    ((codePoint >= 0x20) && (codePoint <= 0xD7FF)) ||
                    ((codePoint >= 0xE000) && (codePoint <= 0xFFFD)) ||
                    ((codePoint >= 0x10000) && (codePoint <= 0x10FFFF));
        }

        /// <summary>
        ///  过滤emoji 或者 其他非文字类型的字符
        /// </summary>
        /// <param name="source"></param>
        /// <returns></returns>
        public static String FilterEmoji(string source)
        {
            if (!ContainsEmoji(source))
                return source;//如果不包含，直接返回
            //到这里铁定包含
            StringBuilder buf = null;
            char[] item = source.ToCharArray();
            for (int i = 0; i < source.Length; i++)
            {
                char codePoint = item[i];
                if (IsEmojiCharacter(codePoint))
                {
                    if (buf == null)
                        buf = new StringBuilder(source.Length);
                    buf.Append(codePoint);
                }
            }
            if (buf == null)
                return source;//如果没有找到 emoji表情，则返回源字符串
            else
            {
                if (buf.Length == source.Length)
                {
                    buf = null;//这里的意义在于尽可能少的toString，因为会重新生成字符串
                    return source;
                }
                else
                    return buf.ToString();
            }

        }

    }
}