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

/// <summary>
///
/// </summary>
public partial class Utils
{

}

/// <summary>
/// 扩展下Linq,增加一个取随机值方法. wanggangzero@vip.qq.coms
/// </summary>
public static class LinqExt
{
    
    static Random r = new Random(Guid.NewGuid().GetHashCode());  // 随机种子

    /// <summary>
    /// 从集合中随机取一批数据
    /// </summary>
    /// <typeparam name="T"></typeparam>
    /// <param name="source"></param>
    /// <param name="count"></param>
    /// <returns></returns>
    public static IEnumerable<T> Random<T>(this IEnumerable<T> source, int? count = null)
    {
        return count.HasValue ? source.OrderBy(_ => r.Next()).Take(count.Value) : source.OrderBy(_ => r.Next());
    }

    /// <summary>
    /// 仿PHP的implode函数
    /// </summary>
    /// <param name="source"></param>
    /// <param name="glue"></param>
    /// <returns></returns>
    public static string Implode(this IEnumerable<string> source, string glue = "")
    {
        var sb = new StringBuilder();
        var n = source.Count();
        int i = 0;
        source.ToList().ForEach(s => sb.Append((++i < n) ? s + glue : s));
        return sb.ToString();
    }

    public static string[] Explode(this string strSource, string seperator = ""){
        return strSource.Split(new string[] { seperator }, StringSplitOptions.RemoveEmptyEntries);    
    }
}