#region License Information (GPL v3)

/*
    ShareX - A program that allows you to take screenshots and share any file type
    Copyright (c) 2007-2023 ShareX Team

    This program is free software; you can redistribute it and/or
    modify it under the terms of the GNU General Public License
    as published by the Free Software Foundation; either version 2
    of the License, or (at your option) any later version.

    This program is distributed in the hope that it will be useful,
    but WITHOUT ANY WARRANTY; without even the implied warranty of
    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
    GNU General Public License for more details.

    You should have received a copy of the GNU General Public License
    along with this program; if not, write to the Free Software
    Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301, USA.

    Optionally you can also view the license at <http://www.gnu.org/licenses/>.
*/

#endregion License Information (GPL v3)

using ShareX.HelpersLib;
using System;
using System.Collections.Generic;
using System.Diagnostics;
using System.Drawing;
using System.Drawing.Imaging;
using System.Runtime.InteropServices;
using System.Threading.Tasks;

namespace ShareX.ScreenCaptureLib
{
    internal class ScrollingCaptureManager : IDisposable
    {
        public ScrollingCaptureOptions Options { get; private set; }
        public Bitmap Result { get; private set; }
        public bool IsCapturing { get; private set; }

        private List<Bitmap> images = new List<Bitmap>();
        private bool stopRequested;
        private int bestMatchCount, bestMatchIndex, currentScrollCount;
        private WindowInfo selectedWindow;
        private Rectangle selectedRectangle;

        public ScrollingCaptureManager(ScrollingCaptureOptions options)
        {
            Options = options;
        }

        public void Dispose()
        {
            if (images != null)
            {
                foreach (Bitmap bmp in images)
                {
                    bmp?.Dispose();
                }

                images.Clear();
            }

            if (Result != null)
            {
                Result.Dispose();
                Result = null;
            }
        }

        private void Reset()
        {
            IsCapturing = false;
            stopRequested = false;
            bestMatchCount = 0;
            bestMatchIndex = 0;
            currentScrollCount = 0;

            Dispose();
        }

        public async Task StartCapture()
        {
            if (!IsCapturing && selectedWindow != null)
            {
                Reset();

                IsCapturing = true;

                selectedWindow.Activate();

                await Task.Delay(Options.StartDelay);

                InputHelpers.SendKeyPress(VirtualKeyCode.HOME);
                NativeMethods.SendMessage(selectedWindow.Handle, (int)WindowsMessages.VSCROLL, (int)ScrollBarCommands.SB_TOP, 0);

                Stopwatch timer = new Stopwatch();

                do
                {
                    int delay = Options.ScrollDelay - (int)timer.ElapsedMilliseconds;

                    if (delay > 0)
                    {
                        await Task.Delay(delay);
                    }

                    if (stopRequested)
                    {
                        break;
                    }

                    Screenshot screenshot = new Screenshot()
                    {
                        CaptureCursor = false
                    };

                    Bitmap bmp = screenshot.CaptureRectangle(selectedRectangle);

                    if (bmp != null)
                    {
                        images.Add(bmp);
                    }

                    InputHelpers.SendMouseWheel(-120 * 2);
                    currentScrollCount++;
                    timer.Restart();

                    if (images.Count > 0)
                    {
                        Result = await CombineImagesAsync(Result, images[images.Count - 1]);
                    }
                }
                while (!stopRequested && currentScrollCount <= Options.MaximumScrollCount && !IsScrollReachedBottom(selectedWindow.Handle));

                IsCapturing = false;
            }
        }

        public void StopCapture()
        {
            if (IsCapturing)
            {
                stopRequested = true;
            }
        }

        public bool SelectWindow()
        {
            return RegionCaptureTasks.GetRectangleRegion(out selectedRectangle, out selectedWindow, new RegionCaptureOptions());
        }

        private bool IsScrollReachedBottom(IntPtr handle)
        {
            SCROLLINFO scrollInfo = new SCROLLINFO();
            scrollInfo.cbSize = (uint)Marshal.SizeOf(scrollInfo);
            scrollInfo.fMask = (uint)(ScrollInfoMask.SIF_RANGE | ScrollInfoMask.SIF_PAGE | ScrollInfoMask.SIF_TRACKPOS);

            if (NativeMethods.GetScrollInfo(handle, (int)SBOrientation.SB_VERT, ref scrollInfo))
            {
                return scrollInfo.nMax == scrollInfo.nTrackPos + scrollInfo.nPage - 1;
            }

            return IsLastTwoImagesSame();
        }

        private bool IsLastTwoImagesSame()
        {
            bool result = false;

            if (images.Count > 1)
            {
                result = ImageHelpers.CompareImages(images[images.Count - 1], images[images.Count - 2]);

                if (result)
                {
                    Bitmap last = images[images.Count - 1];
                    images.Remove(last);
                    last.Dispose();
                }
            }

            return result;
        }

        private async Task<Bitmap> CombineImagesAsync(Bitmap result, Bitmap currentImage)
        {
            return await Task.Run(() => CombineImages(result, currentImage));
        }

        private Bitmap CombineImages(Bitmap result, Bitmap currentImage)
        {
            if (result == null)
            {
                return (Bitmap)currentImage.Clone();
            }

            int matchCount = 0;
            int matchIndex = 0;
            int matchLimit = currentImage.Height / 2;
            int ignoreSideOffset = Math.Max(50, currentImage.Width / 20);

            if (currentImage.Width < ignoreSideOffset * 3)
            {
                ignoreSideOffset = 0;
            }

            Rectangle rect = new Rectangle(ignoreSideOffset, result.Height - currentImage.Height, currentImage.Width - ignoreSideOffset * 2, currentImage.Height);

            BitmapData bdResult = result.LockBits(new Rectangle(0, 0, result.Width, result.Height), ImageLockMode.ReadOnly, PixelFormat.Format32bppArgb);
            BitmapData bdCurrentImage = currentImage.LockBits(new Rectangle(0, 0, currentImage.Width, currentImage.Height), ImageLockMode.ReadOnly, PixelFormat.Format32bppArgb);
            int stride = bdResult.Stride;
            int pixelSize = stride / result.Width;
            IntPtr resultScan0 = bdResult.Scan0 + pixelSize * ignoreSideOffset;
            IntPtr currentImageScan0 = bdCurrentImage.Scan0 + pixelSize * ignoreSideOffset;
            int rectBottom = rect.Bottom - 1;
            int compareLength = pixelSize * rect.Width;

            for (int currentImageY = currentImage.Height - 1; currentImageY >= 0 && matchCount < matchLimit; currentImageY--)
            {
                int currentMatchCount = 0;

                for (int y = 0; currentImageY - y >= 0 && currentMatchCount < matchLimit; y++)
                {
                    if (NativeMethods.memcmp(resultScan0 + ((rectBottom - y) * stride), currentImageScan0 + ((currentImageY - y) * stride), compareLength) == 0)
                    {
                        currentMatchCount++;
                    }
                    else
                    {
                        break;
                    }
                }

                if (currentMatchCount > matchCount)
                {
                    matchCount = currentMatchCount;
                    matchIndex = currentImageY;
                }
            }

            result.UnlockBits(bdResult);
            currentImage.UnlockBits(bdCurrentImage);

            if (matchCount == 0 && bestMatchCount > 0)
            {
                matchCount = bestMatchCount;
                matchIndex = bestMatchIndex;
            }

            if (matchCount > 0)
            {
                int matchHeight = currentImage.Height - matchIndex - 1;

                if (matchHeight > 0)
                {
                    if (matchCount > bestMatchCount)
                    {
                        bestMatchCount = matchCount;
                        bestMatchIndex = matchIndex;
                    }

                    Bitmap newResult = new Bitmap(result.Width, result.Height + matchHeight);

                    using (Graphics g = Graphics.FromImage(newResult))
                    {
                        g.DrawImage(result, new Rectangle(0, 0, result.Width, result.Height),
                            new Rectangle(0, 0, result.Width, result.Height), GraphicsUnit.Pixel);
                        g.DrawImage(currentImage, new Rectangle(0, result.Height, currentImage.Width, matchHeight),
                            new Rectangle(0, matchIndex + 1, currentImage.Width, matchHeight), GraphicsUnit.Pixel);
                    }

                    result.Dispose();
                    result = newResult;
                }
            }

            return result;
        }
    }
}