using System;
using System.Collections.Generic;
using System.Drawing;
using System.Drawing.Imaging;
using System.IO;
using System.Runtime.Versioning;
using System.Text;

namespace VOL.Core.Utilities
{
    public static class VierificationCode
    {
        private static readonly string[] _chars = new string[] { "0", "1", "2", "3", "4", "5", "6", "7", "8", "9", "a", "b", "c", "d", "e", "f", "g", "h", "i", "j", "k", "l", "m", "n", "p", "q", "r", "s", "t", "u", "v", "w", "x", "y", "z", "A", "B", "C", "D", "E", "F", "G", "H", "I", "J", "K", "L", "M", "N", "P", "P", "Q", "R", "S", "T", "U", "V", "W", "X", "Y", "Z" };
        public static string RandomText()
        {
            string code = "";//产生的随机数
            int temp = -1;
            Random rand = new Random();
            for (int i = 1; i < 5; i++)
            {
                if (temp != -1)
                {
                    rand = new Random(i * temp * unchecked((int)DateTime.Now.Ticks));
                }
                int t = rand.Next(61);
                if (temp != -1 && temp == t)
                {
                    return RandomText();
                }
                temp = t;
                code += _chars[t];
            }
            return code;
        }

        [SupportedOSPlatform("Windows")]
        [Obsolete("仅在 Windows 上支持 System.Drawing.Common,具体请参考：https://docs.microsoft.com/zh-cn/dotnet/core/compatibility/core-libraries/6.0/system-drawing-common-windows-only")]
        public static string CreateBase64Imgage(string code)
        {
            Random random = new Random();
            //验证码颜色集合
            Color[] c = { Color.Black, Color.Red, Color.DarkBlue, Color.Green, Color.Orange, Color.Brown, Color.DarkCyan, Color.Purple };
            //验证码字体集合
            string[] fonts = { "Verdana", "Microsoft Sans Serif", "Comic Sans MS", "Arial", "宋体" };

            using var img = new Bitmap((int)code.Length * 18, 32);
            using var g = Graphics.FromImage(img);
            g.Clear(Color.White);//背景设为白色

            //在随机位置画背景点
            for (int i = 0; i < 100; i++)
            {
                int x = random.Next(img.Width);
                int y = random.Next(img.Height);
                g.DrawRectangle(new Pen(Color.LightGray, 0), x, y, 1, 1);
            }
            //验证码绘制在g中
            for (int i = 0; i < code.Length; i++)
            {
                int cindex = random.Next(7);//随机颜色索引值
                int findex = random.Next(5);//随机字体索引值
                Font f = new Font(fonts[findex], 15, FontStyle.Bold);//字体
                Brush b = new SolidBrush(c[cindex]);//颜色
                int ii = 4;
                if ((i + 1) % 2 == 0)//控制验证码不在同一高度
                {
                    ii = 2;
                }
                g.DrawString(code.Substring(i, 1), f, b, 3 + (i * 12), ii);//绘制一个验证字符
            }
            using (MemoryStream stream = new MemoryStream())
            {
                img.Save(stream, ImageFormat.Jpeg);
                byte[] b = stream.ToArray();
                return Convert.ToBase64String(stream.ToArray());
            }
        }
    }
}