using System.Drawing;
using System.Drawing.Drawing2D;
using System.Drawing.Imaging;
using System.Security.Cryptography;
using System.Text;

namespace MilliSim.Services.Infrastructure;

public interface ICaptchaService
{
    (string CaptchaId, string Svg) GenerateCaptcha();
    bool ValidateCaptcha(string captchaId, string code);
}

public class CaptchaService : ICaptchaService
{
    private static readonly Dictionary<string, (string Code, DateTime Expire)> _store = new();
    private static readonly object _lock = new();
    private static readonly char[] _chars = "ABCDEFGHJKLMNPQRSTUVWXYZ23456789".ToCharArray();

    public (string CaptchaId, string Svg) GenerateCaptcha()
    {
        var code = new string(Enumerable.Range(0, 4).Select(_ => _chars[RandomNumberGenerator.GetInt32(_chars.Length)]).ToArray());
        var captchaId = Guid.NewGuid().ToString("N");

        lock (_lock)
        {
            _store[captchaId] = (code, DateTime.Now.AddMinutes(5));
            // 清理过期
            var expired = _store.Where(x => x.Value.Expire < DateTime.Now).Select(x => x.Key).ToList();
            foreach (var key in expired) _store.Remove(key);
        }

        var svg = DrawSvg(code);
        return (captchaId, svg);
    }

    public bool ValidateCaptcha(string captchaId, string code)
    {
        if (string.IsNullOrEmpty(captchaId) || string.IsNullOrEmpty(code))
            return false;

        lock (_lock)
        {
            if (!_store.TryGetValue(captchaId, out var item))
                return false;

            _store.Remove(captchaId);

            if (item.Expire < DateTime.Now)
                return false;

            return string.Equals(item.Code, code, StringComparison.OrdinalIgnoreCase);
        }
    }

    private static string DrawSvg(string code)
    {
        var random = new Random();
        var width = 120;
        var height = 40;
        var sb = new StringBuilder();

        sb.Append($"<svg xmlns=\"http://www.w3.org/2000/svg\" width=\"{width}\" height=\"{height}\">");

        // 背景
        sb.Append($"<rect width=\"{width}\" height=\"{height}\" fill=\"#E6F4FF\"/>");

        // 干扰线
        for (var i = 0; i < 4; i++)
        {
            var x1 = random.Next(width);
            var y1 = random.Next(height);
            var x2 = random.Next(width);
            var y2 = random.Next(height);
            var color = GetRandomColor(random);
            sb.Append($"<line x1=\"{x1}\" y1=\"{y1}\" x2=\"{x2}\" y2=\"{y2}\" stroke=\"{color}\" stroke-width=\"1\" opacity=\"0.5\"/>");
        }

        // 干扰点
        for (var i = 0; i < 20; i++)
        {
            var x = random.Next(width);
            var y = random.Next(height);
            var color = GetRandomColor(random);
            sb.Append($"<circle cx=\"{x}\" cy=\"{y}\" r=\"1\" fill=\"{color}\" opacity=\"0.5\"/>");
        }

        // 文字
        var colors = new[] { "#0958D9", "#1677FF", "#52C41A", "#722ED1", "#FA8C16" };
        for (var i = 0; i < code.Length; i++)
        {
            var x = 15 + i * 25;
            var y = 28 + random.Next(-3, 4);
            var angle = random.Next(-15, 16);
            var color = colors[random.Next(colors.Length)];
            var fontSize = random.Next(22, 28);
            sb.Append($"<text x=\"{x}\" y=\"{y}\" font-size=\"{fontSize}\" font-family=\"Arial\" font-weight=\"bold\" fill=\"{color}\" transform=\"rotate({angle} {x} {y})\">{code[i]}</text>");
        }

        sb.Append("</svg>");
        return sb.ToString();
    }

    private static string GetRandomColor(Random random)
    {
        var colors = new[] { "#0958D9", "#1677FF", "#52C41A", "#722ED1", "#FA8C16", "#13C2C2" };
        return colors[random.Next(colors.Length)];
    }
}