using System;
using System.Collections.Generic;
using System.Drawing;
using System.Drawing.Drawing2D;
using System.Drawing.Imaging;
using System.IO;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Web;

namespace Pcb.Common
{
    /// <summary>
    /// 生成验证码的类
    /// 
    /// @2015.6.15
    /// 参考: http://www.cnblogs.com/jianjialin/archive/2009/12/16/1625780.html
    /// </summary>
    public class ValidateCode
    {
        public ValidateCode()
        {
        }

        /// <summary>
        /// 验证码的最大长度
        /// </summary>
        public int MaxLength
        {
            get { return 10; }
        }

        /// <summary>
        /// 验证码的最小长度
        /// </summary>
        public int MinLength
        {
            get { return 1; }
        }

        /// <summary>
        /// 生成验证码
        /// </summary>
        /// <param name="length">指定验证码的长度</param>
        /// <returns></returns>
        public string CreateValidateCode(int length)
        {
            var randMembers = new int[length];
            var validateNums = new int[length];
            var validateNumberStr = "";
            //生成起始序列值
            var seekSeek = unchecked((int) DateTime.Now.Ticks);
            var seekRand = new Random(seekSeek);
            var beginSeek = (int) seekRand.Next(0, Int32.MaxValue - length*10000);
            var seeks = new int[length];
            for (var i = 0; i < length; i++)
            {
                beginSeek += 10000;
                seeks[i] = beginSeek;
            }
            //生成随机数字
            for (var i = 0; i < length; i++)
            {
                var rand = new Random(seeks[i]);
                var pownum = 1*(int) Math.Pow(10, length);
                randMembers[i] = rand.Next(pownum, Int32.MaxValue);
            }
            //抽取随机数字
            for (var i = 0; i < length; i++)
            {
                var numStr = randMembers[i].ToString();
                var numLength = numStr.Length;
                var rand = new Random();
                var numPosition = rand.Next(0, numLength - 1);
                validateNums[i] = int.Parse(numStr.Substring(numPosition, 1));
            }
            //生成验证码
            for (var i = 0; i < length; i++)
            {
                validateNumberStr += validateNums[i].ToString();
            }
            return validateNumberStr;
        }

        /// <summary>
        /// 得到验证码图片的长度
        /// </summary>
        /// <param name="validateNumLength">验证码的长度</param>
        /// <returns></returns>
        public static int GetImageWidth(int validateNumLength)
        {
            return (int) (validateNumLength*12.0);
        }

        /// <summary>
        /// 得到验证码的高度
        /// </summary>
        /// <returns></returns>
        public static double GetImageHeight()
        {
            return 22.5;
        }
    }
}