using System;
using System.Drawing;
using System.Linq;
using System.Windows.Forms;

namespace Widow
{
    public partial class DrawOverlayForm : Form
    {
        public event EventHandler<WindowDrawnEventArgs> WindowDrawn;
        #region Public Enums, Properties and Fields

        public bool IsMouseDown { get; set; }

        public Point StartLocation { get; set; }

        public Point StopLocation { get; set; }

        public SolidBrush DrawBrush { get; }

        public SolidBrush FormBrush { get; }

        #endregion

        #region Private Delegates, Events, Enums, Properties, Indexers and Fields

        private Point CurrentLocation { get; set; }

        private volatile Bitmap _bitmap;

        #endregion

        #region Constructors, Destructors and Finalizers

        public DrawOverlayForm()
        {
            InitializeComponent();

            DrawBrush = new SolidBrush(Color.LightBlue);
            FormBrush = new SolidBrush(Color.White);
        }

        #endregion

        #region Event Handlers

        private void DrawOverlayForm_MouseDown(object sender, MouseEventArgs e)
        {
            IsMouseDown = true;
            StartLocation = e.Location;
        }

        private void DrawOverlayForm_MouseUp(object sender, MouseEventArgs e)
        {
            IsMouseDown = false;
            StopLocation = e.Location;

            var left = Math.Min(StartLocation.X, StopLocation.X);
            var top = Math.Min(StartLocation.Y, StopLocation.Y);
            var width = Math.Abs(StopLocation.X - StartLocation.X);
            var height = Math.Abs(StopLocation.Y - StartLocation.Y);

            WindowDrawn?.Invoke(this, new WindowDrawnEventArgs(left, top, width, height));

            Close();
        }

        private void DrawOverlayForm_MouseMove(object sender, MouseEventArgs e)
        {
            CurrentLocation = e.Location;

            if (!IsMouseDown)
            {
                return;
            }

            var selection = new Rectangle(
                Math.Min(StartLocation.X, CurrentLocation.X),
                Math.Min(StartLocation.Y, CurrentLocation.Y),
                Math.Abs(StartLocation.X - CurrentLocation.X),
                Math.Abs(StartLocation.Y - CurrentLocation.Y));

            _bitmap = new Bitmap(Width, Height);

            using (var canvas = Graphics.FromImage(_bitmap))
            {
                canvas.Clear(Color.White);
                canvas.FillRectangle(DrawBrush, selection);
            }

            Invalidate();
            Update();
        }

        private void DrawOverlayForm_Paint(object sender, PaintEventArgs e)
        {
            if (_bitmap == null)
            {
                return;
            }

            var graphics = e.Graphics;

            graphics.DrawImage(_bitmap, Location.X, Location.Y, Width, Height);

            _bitmap?.Dispose();
            _bitmap = null;
        }

        #endregion
    }
}