﻿namespace HtmlLogger
{
    using Contracts;
    using System;
    using System.Drawing;
    using System.Drawing.Imaging;
    using System.Runtime.InteropServices;

    internal sealed class ScreenCapturer : IScreenCapturer
    {
        /// <summary>
        /// Provides functions to capture the entire screen, or a particular window, and save it to a file.
        /// </summary>
        public ScreenCapturer()
        {
        }

        /// <summary>
        /// Creates an Image object containing a screen shot of the entire desktop
        /// </summary>
        /// <returns></returns>
        public Image CaptureScreen()
        {
            return CaptureWindow(User32.GetDesktopWindow());
        }

        /// <summary>
        /// Creates an Image object containing a screen shot of a specific window
        /// </summary>
        /// <param name="handle">The handle to the window. (In windows forms, this is obtained by the Handle property)</param>
        /// <returns></returns>
        public Image CaptureWindow(IntPtr handle)
        {
            // get te hDC of the target window
            IntPtr hdcSrc = User32.GetWindowDC(handle);

            // get the size
            User32.Rect windowRect = new User32.Rect();
            User32.GetWindowRect(handle, ref windowRect);

            int width = windowRect.Right - windowRect.Left;
            int height = windowRect.Bottom - windowRect.Top;

            //TODO: Magic number! Needs to be debuged, besides the width of taken screenshot is not enough.
            width += 160;
            height += 110;

            // create a device context we can copy to
            IntPtr hdcDest = GDI32.CreateCompatibleDC(hdcSrc);

            // create a bitmap we can copy it to,
            // using GetDeviceCaps to get the width/height
            IntPtr hBitmap = GDI32.CreateCompatibleBitmap(hdcSrc, width, height);

            // select the bitmap object
            IntPtr hOld = GDI32.SelectObject(hdcDest, hBitmap);

            // bitblt over
            GDI32.BitBlt(hdcDest, 0, 0, width, height, hdcSrc, 0, 0, GDI32.SRCCOPY);

            // restore selection
            GDI32.SelectObject(hdcDest, hOld);

            // clean up
            GDI32.DeleteDC(hdcDest);
            User32.ReleaseDC(handle, hdcSrc);

            // get a .NET image object for it
            Image img = Image.FromHbitmap(hBitmap);

            // free up the Bitmap object
            GDI32.DeleteObject(hBitmap);

            return img;
        }

        /// <summary>
        /// Captures a screen shot of a specific window, and saves it to a file
        /// </summary>
        /// <param name="handle"></param>
        /// <param name="filename"></param>
        /// <param name="format"></param>
        public void CaptureWindowToFile(IntPtr handle, string filename, ImageFormat format)
        {
            Image img = CaptureWindow(handle);
            img.Save(filename, format);
        }

        /// <summary>
        /// Captures a screen shot of the entire desktop, and saves it to a file
        /// </summary>
        /// <param name="filename"></param>
        /// <param name="format"></param>
        public void CaptureScreenToFile(string filename, ImageFormat format)
        {
            Image img = CaptureScreen();
            img.Save(filename, format);
        }

        /// <summary>
        /// Helper class containing Gdi32 API functions
        /// </summary>
        private class GDI32
        {
            public const int SRCCOPY = 0x00CC0020; // BitBlt dwRop parameter

            [DllImport("gdi32.dll")]
            public static extern bool BitBlt(IntPtr hObject, int nXDest, int nYDest,
                int nWidth, int nHeight, IntPtr hObjectSource,
                int nXSrc, int nYSrc, int dwRop);

            [DllImport("gdi32.dll")]
            public static extern IntPtr CreateCompatibleBitmap(IntPtr hDC, int nWidth,
                int nHeight);

            [DllImport("gdi32.dll")]
            public static extern IntPtr CreateCompatibleDC(IntPtr hDC);

            [DllImport("gdi32.dll")]
            public static extern bool DeleteDC(IntPtr hDC);

            [DllImport("gdi32.dll")]
            public static extern bool DeleteObject(IntPtr hObject);

            [DllImport("gdi32.dll")]
            public static extern IntPtr SelectObject(IntPtr hDC, IntPtr hObject);
        }

        /// <summary>
        /// Helper class containing User32 API functions
        /// </summary>
        private class User32
        {
            [StructLayout(LayoutKind.Sequential)]
            public struct Rect
            {
                public int Left;
                public int Top;
                public int Right;
                public int Bottom;
            }

            [DllImport("user32.dll")]
            public static extern IntPtr GetDesktopWindow();

            [DllImport("user32.dll")]
            public static extern IntPtr GetForegroundWindow();

            [DllImport("user32.dll")]
            public static extern IntPtr GetWindowDC(IntPtr hWnd);

            [DllImport("user32.dll")]
            public static extern IntPtr ReleaseDC(IntPtr hWnd, IntPtr hDC);

            [DllImport("user32.dll")]
            public static extern IntPtr GetWindowRect(IntPtr hWnd, ref Rect rect);
        }

        public IntPtr GetActiveWindowHandle()
        {
            return User32.GetForegroundWindow();
        }
    }
}