using System;
using System.Diagnostics;
using System.IO;
using System.Drawing;
using System.Drawing.Imaging;
using System.Threading;
using System.Threading.Tasks;
using DesertPaintCodex.Models;
using DesertPaintCodex.Util;

namespace DesertPaintCodex.Services
{
    public class ReactionScannerService
    {
        private enum LogVerbosity
        {
            Low,
            Normal,
            High,
            Excessive
        }

        private const int SwatchHeight    = 24;
        private const int RedBarSpacing   = 32;
        private const int GreenBarSpacing = 42;
        private const int BlueBarSpacing  = 52;

        private const int MinSwatchWidth = 306;
        private const int MaxSwatchWidth = 411;

        private static ReactionScannerService? s_instance;
        public static ReactionScannerService Instance => s_instance ??= new ReactionScannerService();

        private int _swatchHeight    = 0;
        private int _minSwatchWidth  = 0;
        private int _maxSwatchWidth  = 0;
        private int _swatchWidth     = 0;
        private int _redBarSpacing   = 0;
        private int _greenBarSpacing = 0;
        private int _blueBarSpacing  = 0;
        private int _swatchTopBorder    = 0;
        private int _swatchBottomBorder = 0;
        private int _swatchLeftBorder   = 0;
        private int _swatchRightBorder  = 0;
        private int _swatchTestWidth = 0;

        private bool _lockedSwatchWidth = false;

        // Current Status
        public bool IsCaptured { get; private set; }

        private readonly PaintColor _recordedColor = new();
        public PaintColor RecordedColor {
            get => _recordedColor;
            private set => _recordedColor.Set(value);
        }

        private int _pixelMultiplier = 1;

        private bool _firstRun   = true;
        private int _lastSwatchX = -1;
        private int _lastSwatchY = -1;
        private int _screenX     = 0;
        private int _screenY     = 0;

        private Bitmap _targetBitmap;

        private LogVerbosity _logVerbosity = LogVerbosity.Normal;

        private CancellationTokenSource? _canceler;

        public StreamWriter? Log { get; set; }
        
        private void WriteLog(LogVerbosity verbosity, string format, params object[] args)
        {
            // Dumping this to Debug, for now.
            if (verbosity <= _logVerbosity)
            {
                Debug.WriteLine(format, args);
            }
            
            /*
            if ((Log != null) && (verbosity <= _logVerbosity))
            {
                Log.WriteLine(format, args);
            }
            */
        }
        
        public ReactionScannerService()
        {
            RefreshFromSettings();
            Debug.Assert(_targetBitmap != null);
        }

        public void RefreshFromSettings()
        {
            SettingsService.Get(SettingKey.PixelMultiplier, out _pixelMultiplier, Constants.DefaultPixelMultiplier);

            SettingsService.Get(SettingKey.ScreenX, out _screenX, Constants.DefaultScreenX);
            SettingsService.Get(SettingKey.ScreenY, out _screenY, Constants.DefaultScreenY);
            
            SettingsService.Get(SettingKey.ScreenWidth,  out int screenWidth, Constants.DefaultScreenWidth);
            SettingsService.Get(SettingKey.ScreenHeight, out int screenHeight, Constants.DefaultScreenHeight);
            
            _targetBitmap = new Bitmap(screenWidth, screenHeight);

            UpdateSwatchSizes();
        }
        

        private void UpdateSwatchSizes()
        {
            _swatchWidth     = MinSwatchWidth * _pixelMultiplier;
            _swatchHeight    = SwatchHeight    * _pixelMultiplier;
            _redBarSpacing   = RedBarSpacing   * _pixelMultiplier;
            _greenBarSpacing = GreenBarSpacing * _pixelMultiplier;
            _blueBarSpacing  = BlueBarSpacing  * _pixelMultiplier;
            _swatchTopBorder    = 2 * _pixelMultiplier;
            _swatchBottomBorder = 2 * _pixelMultiplier;
            _swatchLeftBorder   = 2 * _pixelMultiplier;
            _swatchRightBorder  = 2 * _pixelMultiplier;
            _minSwatchWidth = MinSwatchWidth * _pixelMultiplier;
            _maxSwatchWidth = MaxSwatchWidth * _pixelMultiplier;
            _swatchTestWidth = (int)(0.1f * MinSwatchWidth * _pixelMultiplier);
        }

        public void CancelScan()
        {
            _canceler?.Cancel();
        }

        private static class ColorMatcher
        {
            public static Color Color;

            public static bool IsMatch(Color otherColor)
            {
                return PixelColor.IsMatch(Color, otherColor);
            }
        }
        
        private bool IsPossibleSwatchSlice(Pixels pixels, int x, int y)
        {
            // 1.) Check if the top pixel is a dark pixel.
            if (!PixelColor.IsDark(pixels.ColorAt(x, y))) return false;
            
            // 2.) grab the swatch color 2 down from top border
            ColorMatcher.Color = pixels.ColorAt(x, y + _swatchTopBorder);

            // Scan the column from 2 below the top to 3 above the bottom to ensure the color matches
            for (int i = 2; i < (_swatchHeight - 3); ++i)
            {
                if (!pixels.DoesPixelMatch(x, y + i, ColorMatcher.IsMatch)) return false;
            }

            return true;
        }

        private bool IsPossibleSwatchUpperLeft(Pixels pixels, int x, int y)
        {
            bool result = true;

            int swatchSolidWidth   = _swatchWidth  - _swatchLeftBorder - _swatchRightBorder;
            int swatchSolidHeight  = _swatchHeight - _swatchTopBorder - _swatchBottomBorder;
            int swatchSolidLeftX   = x + _swatchLeftBorder;
            int swatchSolidTopY    = y + _swatchTopBorder;
            int swatchSolidRightX  = swatchSolidLeftX + swatchSolidWidth - 1;
            int swatchSolidBottomY = swatchSolidTopY + swatchSolidHeight - 1;
            
            Color swatchColor = pixels.ColorAt(swatchSolidLeftX, swatchSolidTopY);
            ColorMatcher.Color = swatchColor;

            // Check the other 3 corners of the swatch size for color match
            Color testColor = Color.Black;
            bool upperRightResult = pixels.DoesPixelMatch(swatchSolidRightX, swatchSolidTopY, ColorMatcher.IsMatch);
            if (!upperRightResult)
            {
                testColor = pixels.ColorAt(swatchSolidRightX, swatchSolidTopY);
                WriteLog(LogVerbosity.Excessive, "Upper-right mismatch for {8}, {9} - found {0},{1},{2} at {3}, {4} expected {5},{6},{7}", testColor.R, testColor.G, testColor.B, swatchSolidRightX, swatchSolidTopY, swatchColor.R, swatchColor.G, swatchColor.B, x, y);
            }
            bool lowerLeftResult = pixels.DoesPixelMatch(swatchSolidLeftX, swatchSolidBottomY, ColorMatcher.IsMatch);
            if (!lowerLeftResult)
            {
                testColor = pixels.ColorAt(swatchSolidLeftX, swatchSolidBottomY);
                WriteLog(LogVerbosity.Excessive, "Lower-left mismatch for {8}, {9} - found {0},{1},{2} at {3}, {4} expected {5},{6},{7}", testColor.R, testColor.G, testColor.B, swatchSolidLeftX, swatchSolidBottomY, swatchColor.R, swatchColor.G, swatchColor.B, x, y);
            }
            bool lowerRightResult = pixels.DoesPixelMatch(swatchSolidRightX, swatchSolidBottomY, ColorMatcher.IsMatch);
            if (!lowerRightResult)
            {
                testColor = pixels.ColorAt(swatchSolidRightX, swatchSolidBottomY);
                WriteLog(LogVerbosity.Excessive, "Lower-right mismatch for {8}, {9} - found {0},{1},{2} at {3}, {4} expected {5},{6},{7}", testColor.R, testColor.G, testColor.B, swatchSolidRightX, swatchSolidBottomY, swatchColor.R, swatchColor.G, swatchColor.B, x, y);
            }

            result &= upperRightResult;
            result &= lowerLeftResult;
            result &= lowerRightResult;
            if (!result)
            {
                // Box corners test failed
                WriteLog(LogVerbosity.High, "Failed to find left edge for potential swatch of color {2}, {3}, {4} at {0}, {1}", x, y, swatchColor.R, swatchColor.G, swatchColor.B);
                return false;
            }
            
            // Find the right side of the swatch, if necessary.
            if (!_lockedSwatchWidth)
            {
                int xCutoff = Math.Min(x + _maxSwatchWidth - _swatchRightBorder, _targetBitmap.Width);
                int newRight = swatchSolidRightX;
                for (int px = swatchSolidRightX; px < xCutoff; px++)
                {
                    if (pixels.DoesPixelMatch(px, swatchSolidTopY, ColorMatcher.IsMatch) &&
                        pixels.DoesPixelMatch(px, swatchSolidBottomY, ColorMatcher.IsMatch))
                    {
                        newRight = px;
                    }
                    else break;
                }

                swatchSolidRightX = newRight;
                _swatchWidth = swatchSolidRightX + _swatchRightBorder - x + _pixelMultiplier;
                WriteLog(LogVerbosity.High, "Setting new swatch width of {0}.", _swatchWidth);
            }

            // scan down the right and left sides
            for (int yOff = _pixelMultiplier; yOff < (swatchSolidHeight - _pixelMultiplier); ++yOff)
            {
                result &= pixels.DoesPixelMatch(swatchSolidLeftX, swatchSolidTopY + yOff, ColorMatcher.IsMatch);
                if (!result)
                {
                    testColor = pixels.ColorAt(swatchSolidLeftX, swatchSolidTopY + yOff);
                    break;
                }
                result &= pixels.DoesPixelMatch(swatchSolidRightX, swatchSolidTopY + yOff, ColorMatcher.IsMatch);
                if (!result)
                {
                    testColor = pixels.ColorAt(swatchSolidRightX, swatchSolidTopY + yOff);
                    break;
                }
            }
            if (!result)
            {
                WriteLog(LogVerbosity.Normal, "Failed to find left/right edges for potential swatch of color {2}, {3}, {4} at ({0}, {1}) [failed color = {5},{6},{7}]", x, y, swatchColor.R, swatchColor.G, swatchColor.B, testColor.R, testColor.G, testColor.B);
                return false;
            }
            for (int xOff = _pixelMultiplier; xOff < (swatchSolidWidth - _pixelMultiplier); ++xOff)
            {
                result &= pixels.DoesPixelMatch(swatchSolidLeftX + xOff, swatchSolidTopY, ColorMatcher.IsMatch);
                if (!result)
                {
                    testColor = pixels.ColorAt(swatchSolidLeftX + xOff, swatchSolidTopY);
                    break;
                }
                result &= pixels.DoesPixelMatch(swatchSolidLeftX + xOff, swatchSolidBottomY, ColorMatcher.IsMatch);
                if (!result)
                {
                    testColor = pixels.ColorAt(swatchSolidLeftX + xOff, swatchSolidBottomY);
                    break;
                }
            }
            if (!result)
            {
                WriteLog(LogVerbosity.Normal, "Failed to match upper/lower edges for potential swatch of color {2}, {3}, {4} at ({0}, {1}) [failed color = {5},{6},{7}]", x, y, swatchColor.R, swatchColor.G, swatchColor.B, testColor.R, testColor.G, testColor.B);
                return false;
            }


            // test the left edge for dark pixels -- the bottom-most pixel is bright now
            int i = 0;
            for (i = _pixelMultiplier; result && i < _swatchHeight - _pixelMultiplier; ++i)
            {
                result &= pixels.DoesPixelMatch(x, y + i, PixelColor.IsDark);
                if (!result) break;
            }
            if (!result)
            {
                // No dark border on the left side
                WriteLog(LogVerbosity.Normal, "Failed to find left border for potential swatch of color {2}, {3}, {4} at {0}, {1}", x, y, swatchColor.R, swatchColor.G, swatchColor.B);
                return false;
            }

            // test the dark top border and for background above and below the swatch
            bool borderError = false;
            int bgErrorCount = 0;
            for (i = 0; result && (i < _swatchWidth - _pixelMultiplier); ++i)
            {
                bool isBorder = pixels.DoesPixelMatch(x + i, y, PixelColor.IsDark);
                result &= isBorder;
                if (!isBorder)
                {
                    WriteLog(LogVerbosity.Normal, "Probable swatch at {0},{1} failed upper border test at {2},{3}", x, y, x + i, y);
                    borderError = true;
                }

                // Checking along the top of the swatch for background
                // The row just above is shaded, so check 2 above
                if (y > 1)
                {
                    bool isUiBackground = pixels.DoesPixelMatch(x + i, y - _swatchTopBorder, PixelColor.IsUiBackground);
                    bgErrorCount += isUiBackground ? 0 : 1;

                }
                else
                {
                    ++bgErrorCount;
                }

                // Checking along the bottom of the swatch for background
                if (y < pixels.Height)
                {
                    bool isUiBackground = pixels.DoesPixelMatch(x + i, y + _swatchHeight, PixelColor.IsUiBackground);
                    bgErrorCount += isUiBackground ? 0 : 1;
                }
                else
                {
                    ++bgErrorCount;
                }
            }

            result &= (bgErrorCount < (_swatchWidth / 20)); // allow up to 5% error rate checking for background texture, because this seems to be inconsistent
            if (!result && ((i > (_swatchWidth * 0.8)) || (bgErrorCount >= (_swatchWidth / 20))))
            {
                if (!borderError && (bgErrorCount < _swatchWidth))
                {
                    WriteLog(LogVerbosity.Normal, "Found a potential swatch candidate of width {0} at {1},{2} that had {3} failures matching background color", i, x, y, bgErrorCount);
                }
            }

            return result;
        }

        private bool TestPosition(int x, int y, Pixels pixels, ref PaintColor reactedColor)
        {
            // Check 4 corners of solid area and left/right solid bar areas
            bool foundSwatch = IsPossibleSwatchUpperLeft(pixels, x, y);
            if (foundSwatch)
            {
                WriteLog(LogVerbosity.Normal, "Found probable swatch at {0},{1} - checking border slices", x, y);
                int borderXOffset = 0;
                for (borderXOffset = _swatchLeftBorder; foundSwatch && (borderXOffset < _swatchTestWidth); ++borderXOffset)
                {
                    foundSwatch &= IsPossibleSwatchSlice(pixels, x + borderXOffset, y);
                    if (!foundSwatch)
                    {
                        WriteLog(LogVerbosity.Normal, "Failed slice test at {0},{1}", x + borderXOffset, y);
                        break;
                    }
                    foundSwatch &= IsPossibleSwatchSlice(pixels, x + _swatchWidth - borderXOffset, y);
                    if (!foundSwatch)
                    {
                        WriteLog(LogVerbosity.Normal, "Failed slice test at {0},{1}", x + _swatchWidth - borderXOffset, y);
                        break;
                    }
                }
            }

            if (!foundSwatch)
            {
                if (!_lockedSwatchWidth)
                {
                    // Reset our guess at swatch width.
                    _swatchWidth = MinSwatchWidth;
                }
                return false;
            }
            
            // WE FOUND THE SWATCH!
            // Now we know where the color bars are.
            _lockedSwatchWidth = true;
            int redPixelCount = pixels.LengthOfColorAt(x, y + _redBarSpacing, PixelColor.IsRed);
            reactedColor.Red = (byte)Math.Round(redPixelCount * 255f / _swatchWidth);

            int greenPixelCount = pixels.LengthOfColorAt(x, y + _greenBarSpacing, PixelColor.IsGreen);
            reactedColor.Green = (byte)Math.Round(greenPixelCount * 255f / _swatchWidth);

            int bluePixelCount = pixels.LengthOfColorAt(x, y + _blueBarSpacing, PixelColor.IsBlue);
            reactedColor.Blue = (byte)Math.Round(bluePixelCount * 255f / _swatchWidth);
            WriteLog(LogVerbosity.Low, "Found the color swatch at {0}, {1}. Color={2} Red={3}px Green={4}px Blue={5}px", x, y, reactedColor, redPixelCount, greenPixelCount, bluePixelCount);
            return true;
        }

        public async Task<bool> CaptureReactionAsync(IProgress<float> progress)
        {
            _canceler = new CancellationTokenSource(); // You can't re-use these, sadly.
            return await Task.Run(() => CaptureReaction(progress, _canceler.Token));
        }

        private bool CaptureReaction(IProgress<float> progress, CancellationToken cancellToken)
        {
            PaintColor reactedColor = new();
            IsCaptured = false;
            _recordedColor.Clear();

            using (var g = Graphics.FromImage(_targetBitmap))
            {
                Debug.WriteLine("Scan starting at [" + _screenX + ", " + _screenY + "]");
                g.CopyFromScreen(_screenX, _screenY, 0, 0, _targetBitmap.Size, CopyPixelOperation.SourceCopy);
            }
            
            // _targetBitmap.Save(Path.Combine(ProfileManager.CurrentProfile?.Directory ?? "", "screenshot.png"), ImageFormat.Png);

            Pixels pixels = new(_targetBitmap, _pixelMultiplier);

            IsCaptured = false;
            if (!_firstRun)
            {
                // If this is not the first run, let's check the last location, to see if the UI is still there.
                if (TestPosition(_lastSwatchX, _lastSwatchY, pixels, ref reactedColor))
                {
                    IsCaptured = true;
                    RecordedColor = reactedColor;
                    return true;
                }
                
                _firstRun = true;
            }

            SettingsService.Get("Log.Verbosity", out var verbosityIdx, 1);
            _logVerbosity = (LogVerbosity)verbosityIdx;
            
            int patchTestSize = ((_swatchHeight - _swatchTopBorder - _swatchBottomBorder) / 2) - 1;

            SettingsService.Get("ScanArea.Min.X", out var startX, 0);
            SettingsService.Get("ScanArea.Min.Y", out var startY, 0);
            SettingsService.Get("ScanArea.Max.X", out var endX,   _targetBitmap.Width);
            SettingsService.Get("ScanArea.Max.Y", out var endY,   _targetBitmap.Height);
            
            startX = Math.Max(2, Math.Min(startX, _targetBitmap.Width - 2));
            startY = Math.Max(2, Math.Min(startY, _targetBitmap.Height - 2));
            endX = Math.Min(_targetBitmap.Width  - 2, Math.Max(2, endX)) - _minSwatchWidth; //  + patchTestSize;
            endY = Math.Min(_targetBitmap.Height - 2, Math.Max(2, endY)) - (_blueBarSpacing + 10); // + patchTestSize;

            Debug.WriteLine("startX: " + startX + " endX: " + endX + " startY: " + startY + " endY: " + endY + " with patch test size of " + patchTestSize);
            
            int xSpan = endX - startX;
            int ySpan = endY - startY;
            int total = xSpan * ySpan;

            for (int roughX = startX; roughX < endX ; roughX += patchTestSize)
            {
                int xMark = roughX - startX;
                
                for (int roughY = startY; roughY < endY; roughY += patchTestSize)
                {
                    progress.Report((float)((xMark * ySpan) + (roughY - startY)) / total);

                    cancellToken.ThrowIfCancellationRequested();

                    if (!pixels.IsSolidPatchAt(roughX, roughY, patchTestSize, patchTestSize)) continue;
                    Color patchColor = pixels.ColorAt(roughX, roughY);

                    WriteLog(LogVerbosity.Excessive, "Found a solid patch of {2},{3},{4} at {0}, {1}", roughX, roughY, patchColor.R, patchColor.G, patchColor.B);
                    for (int x = Math.Max(0, roughX - patchTestSize - _swatchLeftBorder + _pixelMultiplier); x < roughX; ++x)
                    {
                        for (int y = Math.Max(0, roughY - patchTestSize - _swatchTopBorder + _pixelMultiplier); y < roughY; ++y)
                        {
                            WriteLog(LogVerbosity.Excessive, "Searching for potential swatch at {0},{1} after found square at {2},{3}", x, y, roughX, roughY);
                            
                            if (!TestPosition(x, y, pixels, ref reactedColor)) continue;
                            
                            RecordedColor = reactedColor;
                            _lastSwatchX  = x;
                            _lastSwatchY  = y;
                            _firstRun     = false;
                            IsCaptured    = true;
                            return true;
                        }
                    }
                    WriteLog(LogVerbosity.Excessive, "False-positive patch of color {0},{1},{2} at {3},{4}", patchColor.R, patchColor.G, patchColor.B, roughX, roughY);
                }
            }
            return false;
        }


        public static Reaction Calculate3WayReaction(PlayerProfile profile, PaintColor expectedColor, PaintColor reactedColor, Reagent reagent0, Reagent reagent1, Reagent reagent2)
        {
            // A 3-reagent reaction.
            Reaction? reaction1 = profile.FindReaction(reagent0, reagent1);
            Reaction? reaction2 = profile.FindReaction(reagent0, reagent2);

            Debug.Assert(reaction1 != null);
            Debug.Assert(reaction2 != null);

            int r = reactedColor.Red   - expectedColor.Red   - reaction1.Red   - reaction2.Red;
            int g = reactedColor.Green - expectedColor.Green - reaction1.Green - reaction2.Green;
            int b = reactedColor.Blue  - expectedColor.Blue  - reaction1.Blue  - reaction2.Blue;
            
            return new Reaction(r, g, b);
        }
        
        public static Reaction CalculateReaction(PaintColor expectedColor, PaintColor reactedColor)
        {
            // A 2-reagent reaction.
            int r = reactedColor.Red   - expectedColor.Red;
            int g = reactedColor.Green - expectedColor.Green;
            int b = reactedColor.Blue  - expectedColor.Blue;
            return new Reaction(r, g, b);
        }
    }
}