using System;
using System.Drawing;
using System.Drawing.Drawing2D;
using System.Drawing.Imaging;
using System.IO;
using System.Runtime.InteropServices;

namespace TimerApp
{
    public static class IconGenerator
    {
        [DllImport("user32.dll", SetLastError = true)]
        private static extern bool DestroyIcon(IntPtr hIcon);

        public static Icon GenerateClockIcon(int size = 64)
        {
            if (size < 16)
                size = 16;

            using (Bitmap bmp = new Bitmap(size, size))
            using (Graphics g = Graphics.FromImage(bmp))
            {
                g.SmoothingMode = SmoothingMode.AntiAlias;
                g.Clear(Color.Transparent);

                DrawClock(g, size);

                IntPtr hIcon = bmp.GetHicon();
                try
                {
                    using Icon icon = Icon.FromHandle(hIcon);
                    return (Icon)icon.Clone();
                }
                finally
                {
                    DestroyIcon(hIcon);
                }
            }
        }

        public static void WriteClockIco(string filePath, int size = 256)
        {
            byte[] icoBytes = CreateClockIcoBytes(size);
            File.WriteAllBytes(filePath, icoBytes);
        }

        private static byte[] CreateClockIcoBytes(int size)
        {
            if (size <= 0)
                size = 256;
            if (size > 256)
                size = 256;
            if (size < 16)
                size = 16;

            byte[] pngBytes;
            using (Bitmap bmp = new Bitmap(size, size))
            using (Graphics g = Graphics.FromImage(bmp))
            {
                g.SmoothingMode = SmoothingMode.AntiAlias;
                g.Clear(Color.Transparent);
                DrawClock(g, size);

                using var ms = new MemoryStream();
                bmp.Save(ms, ImageFormat.Png);
                pngBytes = ms.ToArray();
            }

            using var icoStream = new MemoryStream(6 + 16 + pngBytes.Length);
            using (var bw = new BinaryWriter(icoStream, System.Text.Encoding.UTF8, leaveOpen: true))
            {
                bw.Write((ushort)0);
                bw.Write((ushort)1);
                bw.Write((ushort)1);

                bw.Write((byte)(size == 256 ? 0 : size));
                bw.Write((byte)(size == 256 ? 0 : size));
                bw.Write((byte)0);
                bw.Write((byte)0);
                bw.Write((ushort)1);
                bw.Write((ushort)32);
                bw.Write((uint)pngBytes.Length);
                bw.Write((uint)(6 + 16));
            }

            icoStream.Write(pngBytes, 0, pngBytes.Length);
            return icoStream.ToArray();
        }

        private static void DrawClock(Graphics g, int size)
        {
            int margin = Math.Max(2, size / 16);
            int clockSize = size - margin * 2;
            Rectangle rect = new Rectangle(margin, margin, clockSize, clockSize);

            using (Brush earBrush = new SolidBrush(Color.White))
            {
                g.FillPie(earBrush, 0, 0, size / 2, size / 2, 200, 50);
                g.FillPie(earBrush, size / 2, 0, size / 2, size / 2, 290, 50);
            }

            using (Pen pen = new Pen(Color.White, Math.Max(2, size / 16)))
            {
                g.DrawEllipse(pen, rect);
            }

            Point center = new Point(size / 2, size / 2);
            using (Pen handPen = new Pen(Color.LightGreen, Math.Max(2, size / 22)))
            {
                handPen.EndCap = LineCap.Round;
                g.DrawLine(handPen, center, new Point(center.X + Math.Max(2, size * 10 / 64), center.Y - Math.Max(2, size * 10 / 64)));
                g.DrawLine(handPen, center, new Point(center.X, center.Y - Math.Max(3, size * 18 / 64)));
            }
        }
    }
}