// Copyright © 2017 Paddy Xu
// 
// This file is part of QuickLook program.
// 
// 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 3 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, see <http://www.gnu.org/licenses/>.

using System;
using System.ComponentModel;
using System.Diagnostics;
using System.Runtime.CompilerServices;
using System.Threading;
using System.Threading.Tasks;
using System.Windows;
using System.Windows.Controls;
using System.Windows.Input;
using System.Windows.Media;
using System.Windows.Media.Imaging;
using System.Windows.Threading;
using QuickLook.Annotations;
using QuickLook.Helpers;

namespace QuickLook.Plugin.ImageViewer
{
    /// <summary>
    ///     Interaction logic for ImagePanel.xaml
    /// </summary>
    public partial class ImagePanel : UserControl, INotifyPropertyChanged, IDisposable
    {
        private Visibility _backgroundVisibility = Visibility.Visible;
        private Point? _dragInitPos;
        private Uri _imageSource;
        private DateTime _lastZoomTime = DateTime.MinValue;
        private double _maxZoomFactor = 3d;
        private double _minZoomFactor = 0.1d;
        private BitmapScalingMode _renderMode = BitmapScalingMode.HighQuality;
        private BitmapSource _source;
        private double _zoomFactor = 1d;

        private bool _zoomToFit = true;
        private double _zoomToFitFactor;

        public ImagePanel()
        {
            InitializeComponent();

            var scale = DpiHelper.GetCurrentScaleFactor();
            backgroundBrush.Viewport = new Rect(new Size(
                backgroundBrush.ImageSource.Width / scale.Horizontal,
                backgroundBrush.ImageSource.Height / scale.Vertical));

            SizeChanged += ImagePanel_SizeChanged;

            viewPanel.PreviewMouseWheel += ViewPanel_PreviewMouseWheel;
            viewPanel.MouseLeftButtonDown += ViewPanel_MouseLeftButtonDown;
            viewPanel.MouseMove += ViewPanel_MouseMove;

            viewPanel.ManipulationInertiaStarting += ViewPanel_ManipulationInertiaStarting;
            viewPanel.ManipulationStarting += ViewPanel_ManipulationStarting;
            viewPanel.ManipulationDelta += ViewPanel_ManipulationDelta;
        }

        public BitmapScalingMode RenderMode
        {
            get => _renderMode;
            set
            {
                _renderMode = value;
                OnPropertyChanged();
            }
        }

        public bool ZoomToFit
        {
            get => _zoomToFit;
            set
            {
                _zoomToFit = value;
                OnPropertyChanged();
            }
        }

        public Visibility BackgroundVisibility
        {
            get => _backgroundVisibility;
            set
            {
                _backgroundVisibility = value;
                OnPropertyChanged();
            }
        }

        public double MinZoomFactor
        {
            get => _minZoomFactor;
            set
            {
                _minZoomFactor = value;
                OnPropertyChanged();
            }
        }

        public double MaxZoomFactor
        {
            get => _maxZoomFactor;
            set
            {
                _maxZoomFactor = value;
                OnPropertyChanged();
            }
        }

        public double ZoomToFitFactor
        {
            get => _zoomToFitFactor;
            private set
            {
                _zoomToFitFactor = value;
                OnPropertyChanged();
            }
        }

        public double ZoomFactor
        {
            get => _zoomFactor;
            private set
            {
                _zoomFactor = value;
                OnPropertyChanged();
            }
        }

        public Uri ImageUriSource
        {
            get => _imageSource;
            set
            {
                _imageSource = value;
                OnPropertyChanged();
            }
        }

        public BitmapSource Source
        {
            get => _source;
            set
            {
                _source = value;
                OnPropertyChanged();

                if (ImageUriSource == null)
                    viewPanelImage.Source = _source;
            }
        }

        public void Dispose()
        {
            viewPanelImage?.Dispose();
            viewPanelImage = null;
        }

        public event PropertyChangedEventHandler PropertyChanged;

        public event EventHandler<int> ImageScrolled;
        public event EventHandler DelayedReRender;

        private void ImagePanel_SizeChanged(object sender, SizeChangedEventArgs e)
        {
            if (ZoomToFit)
                DoZoomToFit();
        }

        private void ViewPanel_ManipulationInertiaStarting(object sender, ManipulationInertiaStartingEventArgs e)
        {
            e.TranslationBehavior = new InertiaTranslationBehavior
            {
                InitialVelocity = e.InitialVelocities.LinearVelocity,
                DesiredDeceleration = 10.0 * 96.0 / (1000.0 * 1000.0)
            };
        }

        private void ViewPanel_ManipulationStarting(object sender, ManipulationStartingEventArgs e)
        {
            e.ManipulationContainer = viewPanel;
            e.Mode = ManipulationModes.Scale | ManipulationModes.Translate;
        }

        private void ViewPanel_ManipulationDelta(object sender, ManipulationDeltaEventArgs e)
        {
            var delta = e.DeltaManipulation;

            var newZoom = ZoomFactor + ZoomFactor * (delta.Scale.X - 1);

            Zoom(newZoom);

            viewPanel.ScrollToHorizontalOffset(viewPanel.HorizontalOffset - delta.Translation.X);
            viewPanel.ScrollToVerticalOffset(viewPanel.VerticalOffset - delta.Translation.Y);

            e.Handled = true;
        }

        private void ViewPanel_MouseLeftButtonDown(object sender, MouseButtonEventArgs e)
        {
            e.MouseDevice.Capture(viewPanel);

            _dragInitPos = e.GetPosition(viewPanel);
            var temp = _dragInitPos.Value; // Point is a type value
            temp.Offset(viewPanel.HorizontalOffset, viewPanel.VerticalOffset);
            _dragInitPos = temp;
        }

        private void ViewPanel_MouseMove(object sender, MouseEventArgs e)
        {
            if (!_dragInitPos.HasValue)
                return;

            if (e.LeftButton == MouseButtonState.Released)
            {
                e.MouseDevice.Capture(null);

                _dragInitPos = null;
                return;
            }

            e.Handled = true;

            var delta = _dragInitPos.Value - e.GetPosition(viewPanel);

            viewPanel.ScrollToHorizontalOffset(delta.X);
            viewPanel.ScrollToVerticalOffset(delta.Y);
        }

        private void ViewPanel_PreviewMouseWheel(object sender, MouseWheelEventArgs e)
        {
            e.Handled = true;

            if ((Keyboard.Modifiers & ModifierKeys.Control) == 0)
            {
                // normal scroll
                viewPanel.ScrollToVerticalOffset(viewPanel.VerticalOffset - e.Delta);

                ImageScrolled?.Invoke(this, e.Delta);

                return;
            }

            // zoom
            var newZoom = ZoomFactor + ZoomFactor * e.Delta / 120 * 0.1;

            Zoom(newZoom);
        }

        public Size GetScrollSize()
        {
            return new Size(viewPanel.ScrollableWidth, viewPanel.ScrollableHeight);
        }

        public Point GetScrollPosition()
        {
            return new Point(viewPanel.HorizontalOffset, viewPanel.VerticalOffset);
        }

        public void SetScrollPosition(Point point)
        {
            viewPanel.ScrollToHorizontalOffset(point.X);
            viewPanel.ScrollToVerticalOffset(point.Y);
        }

        public void DoZoomToFit()
        {
            if (viewPanelImage.Source == null)
                return;

            var factor = Math.Min(viewPanel.ActualWidth / viewPanelImage.Source.Width,
                viewPanel.ActualHeight / viewPanelImage.Source.Height);

            ZoomToFitFactor = factor;

            Zoom(factor);
        }

        public void ResetZoom()
        {
            Zoom(1d, true);
        }

        public void Zoom(double factor, bool suppressEvent = false)
        {
            if (viewPanelImage.Source == null)
                return;

            if (ZoomFactor < ZoomToFitFactor && factor > ZoomToFitFactor
                || ZoomFactor > ZoomToFitFactor && factor < ZoomToFitFactor)
            {
                factor = ZoomToFitFactor;
                ZoomToFit = true;
            }

            factor = Math.Max(factor, MinZoomFactor);
            factor = Math.Min(factor, MaxZoomFactor);

            ZoomFactor = factor;

            var position = ZoomToFit
                ? new Point(viewPanelImage.Source.Width / 2, viewPanelImage.Source.Height / 2)
                : Mouse.GetPosition(viewPanelImage);

            viewPanelImage.LayoutTransform = new ScaleTransform(factor, factor);

            viewPanel.InvalidateMeasure();

            // critical for calcuating offset
            viewPanel.ScrollToHorizontalOffset(0);
            viewPanel.ScrollToVerticalOffset(0);
            UpdateLayout();

            var offset = viewPanelImage.TranslatePoint(position, viewPanel) - Mouse.GetPosition(viewPanel);
            viewPanel.ScrollToHorizontalOffset(offset.X);
            viewPanel.ScrollToVerticalOffset(offset.Y);
            UpdateLayout();

            if (!suppressEvent)
                ProcessDelayed();
        }

        private void ProcessDelayed()
        {
            _lastZoomTime = DateTime.Now;

            Task.Delay(500).ContinueWith(t =>
            {
                if (DateTime.Now - _lastZoomTime < TimeSpan.FromSeconds(0.5))
                    return;

                Debug.WriteLine($"ProcessDelayed fired: {Thread.CurrentThread.ManagedThreadId}");

                Dispatcher.BeginInvoke(new Action(() => DelayedReRender?.Invoke(this, new EventArgs())),
                    DispatcherPriority.Background);
            });
        }

        [NotifyPropertyChangedInvocator]
        protected virtual void OnPropertyChanged([CallerMemberName] string propertyName = null)
        {
            PropertyChanged?.Invoke(this, new PropertyChangedEventArgs(propertyName));
        }

        public void ScrollToTop()
        {
            viewPanel.ScrollToTop();
        }

        public void ScrollToBottom()
        {
            viewPanel.ScrollToBottom();
        }
    }
}