using System;
using System.Collections.Generic;
using System.Linq;
using System.Security.Cryptography;
using System.Text;
using System.Text.RegularExpressions;

namespace System
{
	public static class StringExtensions
	{
		/// <summary>
		/// 将字符串作为新List的第一个元素
		/// </summary>
		public static IList<string> AsFirstValueOfList(this string source)
		{
			var list = new List<string>();
			list.Add(source);
			return list;
		}

		public static bool IsNullOrEmpty(this string s)
		{
			return string.IsNullOrEmpty(s);
		}

		#region FormatWith:string.Format。后面三个方法，是为了提高效率而加的：比第一种方法效率高
		public static string FormatWith(this string format, params object[] args)
		{
			return string.Format(format, args);
		}

		public static string FormatWith(this string format, object arg0)
		{
			return string.Format(format, arg0);
		}

		public static string FormatWith(this string format, object arg0, object arg1)
		{
			return string.Format(format, arg0, arg1);
		}

		public static string FormatWith(this string format, object arg0, object arg1, object arg2)
		{
			return string.Format(format, arg0, arg1, arg2);
		}
		#endregion

		public static bool IsMatch(this string s, string pattern)
		{
			if (s == null)
				return false;
			else
				return Regex.IsMatch(s, pattern);
		}

		public static string Match(this string s, string pattern)
		{
			if (s == null)
				return "";
			return Regex.Match(s, pattern).Value;
		}

		public static bool IsInt(this string s)
		{
			int i;
			return int.TryParse(s, out i);
		}

		public static int ToInt(this string s)
		{
			return int.Parse(s);
		}

		/// <summary>
		/// 首字母转换成小写
		/// </summary>
		public static string ToCamel(this string s)
		{
			if (s.IsNullOrEmpty())
				return s;
			return s[0].ToString().ToLower() + s.Substring(1);
		}

		/// <summary>
		/// 首字母转换成大写
		/// </summary>
		public static string ToPascal(this string s)
		{
			if (s.IsNullOrEmpty())
				return s;
			return s[0].ToString().ToUpper() + s.Substring(1);
		}

		public static string ToUnicodeString(this byte[] arr)
		{
			return System.Text.Encoding.Unicode.GetString(arr);
		}

		public static byte[] EncodeUnicodePwd(this string password)
		{
			using (var md5 = MD5.Create())
				return md5.ComputeHash(Encoding.Unicode.GetBytes(password));
		}

	}
}