using Avalonia;
using Avalonia.Controls;
using Avalonia.Controls.Primitives;
using Avalonia.Interactivity;
using Avalonia.Media;
using Avalonia.Styling;
using AvaloniaEdit;
using AvaloniaEdit.Document;
using AvaloniaEdit.Editing;
using AvaloniaEdit.Rendering;
using AvaloniaEdit.TextMate;
using AvaloniaEdit.Utils;
using System;
using System.Globalization;
using System.IO;
using System.Text;
using TextMateSharp.Grammars;

namespace SourceGit.Views {
    public class CombinedTextDiffPresenter : TextEditor {
        public class LineNumberMargin : AbstractMargin {
            public LineNumberMargin(CombinedTextDiffPresenter editor, bool isOldLine) {
                _editor = editor;
                _isOldLine = isOldLine;
                ClipToBounds = true;
            }

            public override void Render(DrawingContext context) {
                if (_editor.DiffData == null) return;

                var view = TextView;
                if (view != null && view.VisualLinesValid) {
                    var typeface = view.CreateTypeface();
                    foreach (var line in view.VisualLines) {
                        var index = line.FirstDocumentLine.LineNumber;
                        if (index > _editor.DiffData.Lines.Count) break;

                        var info = _editor.DiffData.Lines[index - 1];
                        var lineNumber = _isOldLine ? info.OldLine : info.NewLine;
                        if (string.IsNullOrEmpty(lineNumber)) continue;

                        var y = line.GetTextLineVisualYPosition(line.TextLines[0], VisualYPosition.TextTop) - view.VerticalOffset;
                        var txt = new FormattedText(
                            lineNumber,
                            CultureInfo.CurrentCulture,
                            FlowDirection.LeftToRight,
                            typeface,
                            _editor.FontSize,
                            _editor.Foreground);
                        context.DrawText(txt, new Point(Bounds.Width - txt.Width, y));
                    }
                }
            }

            protected override Size MeasureOverride(Size availableSize) {
                if (_editor.DiffData == null || TextView == null) {
                    return new Size(32, 0);
                } else {
                    var typeface = TextView.CreateTypeface();
                    var test = new FormattedText(
                            $"{_editor.DiffData.MaxLineNumber}",
                            CultureInfo.CurrentCulture,
                            FlowDirection.LeftToRight,
                            typeface,
                            _editor.FontSize,
                            Brushes.White);
                    return new Size(test.Width, 0);
                }
            }

            private CombinedTextDiffPresenter _editor;
            private bool _isOldLine;
        }

        public class VerticalSeperatorMargin : AbstractMargin {
            public VerticalSeperatorMargin(CombinedTextDiffPresenter editor) {
                _editor = editor;
            }

            public override void Render(DrawingContext context) {
                var pen = new Pen(_editor.BorderBrush, 1);
                context.DrawLine(pen, new Point(0, 0), new Point(0, Bounds.Height));
            }

            protected override Size MeasureOverride(Size availableSize) {
                return new Size(1, 0);
            }

            private CombinedTextDiffPresenter _editor = null;
        }

        public class LineBackgroundRenderer : IBackgroundRenderer {
            private static readonly Brush BG_EMPTY = new SolidColorBrush(Color.FromArgb(60, 0, 0, 0));
            private static readonly Brush BG_ADDED = new SolidColorBrush(Color.FromArgb(60, 0, 255, 0));
            private static readonly Brush BG_DELETED = new SolidColorBrush(Color.FromArgb(60, 255, 0, 0));

            public KnownLayer Layer => KnownLayer.Background;

            public LineBackgroundRenderer(CombinedTextDiffPresenter editor) {
                _editor = editor;
            }

            public void Draw(TextView textView, DrawingContext drawingContext) {
                if (_editor.Document == null || !textView.VisualLinesValid) return;

                var width = textView.Bounds.Width;
                foreach (var line in textView.VisualLines) {
                    var index = line.FirstDocumentLine.LineNumber;
                    if (index > _editor.DiffData.Lines.Count) break;

                    var info = _editor.DiffData.Lines[index - 1];
                    var bg = GetBrushByLineType(info.Type);
                    if (bg == null) continue;

                    var y = line.GetTextLineVisualYPosition(line.TextLines[0], VisualYPosition.TextTop) - textView.VerticalOffset;
                    drawingContext.DrawRectangle(bg, null, new Rect(0, y, width, line.Height));
                }
            }

            private IBrush GetBrushByLineType(Models.TextDiffLineType type) {
                switch (type) {
                case Models.TextDiffLineType.None: return BG_EMPTY;
                case Models.TextDiffLineType.Added: return BG_ADDED;
                case Models.TextDiffLineType.Deleted: return BG_DELETED;
                default: return null;
                }
            }

            private CombinedTextDiffPresenter _editor = null;
        }

        public class LineStyleTransformer : DocumentColorizingTransformer {
            private static readonly Brush HL_ADDED = new SolidColorBrush(Color.FromArgb(90, 0, 255, 0));
            private static readonly Brush HL_DELETED = new SolidColorBrush(Color.FromArgb(80, 255, 0, 0));

            public LineStyleTransformer(CombinedTextDiffPresenter editor, IBrush indicatorFG) {
                _editor = editor;
                _indicatorFG = indicatorFG;

                var font = App.Current.FindResource("JetBrainsMonoItalic") as FontFamily;
                _indicatorTypeface = new Typeface(font, FontStyle.Italic, FontWeight.Regular);
            }

            protected override void ColorizeLine(DocumentLine line) {
                var idx = line.LineNumber;
                if (idx > _editor.DiffData.Lines.Count) return;

                var info = _editor.DiffData.Lines[idx - 1];
                if (info.Type == Models.TextDiffLineType.Indicator) {
                    ChangeLinePart(line.Offset, line.EndOffset, v => {
                        v.TextRunProperties.SetForegroundBrush(_indicatorFG);
                        v.TextRunProperties.SetTypeface(_indicatorTypeface);
                    });

                    return;
                }

                if (info.Highlights.Count > 0) {
                    var bg = info.Type == Models.TextDiffLineType.Added ? HL_ADDED : HL_DELETED;
                    foreach (var highlight in info.Highlights) {
                        ChangeLinePart(line.Offset + highlight.Start, line.Offset + highlight.Start + highlight.Count, v => {
                            v.TextRunProperties.SetBackgroundBrush(bg);
                        });
                    }
                }
            }

            private CombinedTextDiffPresenter _editor;
            private IBrush _indicatorFG = Brushes.DarkGray;
            private Typeface _indicatorTypeface = Typeface.Default;
        }

        public static readonly StyledProperty<Models.TextDiff> DiffDataProperty =
            AvaloniaProperty.Register<CombinedTextDiffPresenter, Models.TextDiff>(nameof(DiffData));

        public Models.TextDiff DiffData {
            get => GetValue(DiffDataProperty);
            set => SetValue(DiffDataProperty, value);
        }

        public static readonly StyledProperty<IBrush> SecondaryFGProperty =
            AvaloniaProperty.Register<CombinedTextDiffPresenter, IBrush>(nameof(SecondaryFG), Brushes.Gray);

        public IBrush SecondaryFG {
            get => GetValue(SecondaryFGProperty);
            set => SetValue(SecondaryFGProperty, value);
        }

        protected override Type StyleKeyOverride => typeof(TextEditor);

        public CombinedTextDiffPresenter() : base(new TextArea(), new TextDocument()) {
            IsReadOnly = true;
            ShowLineNumbers = false;
            WordWrap = false;
        }

        protected override void OnLoaded(RoutedEventArgs e) {
            base.OnLoaded(e);

            TextArea.LeftMargins.Add(new LineNumberMargin(this, true) { Margin = new Thickness(8, 0) });
            TextArea.LeftMargins.Add(new VerticalSeperatorMargin(this));
            TextArea.LeftMargins.Add(new LineNumberMargin(this, false) { Margin = new Thickness(8, 0) });
            TextArea.LeftMargins.Add(new VerticalSeperatorMargin(this));

            TextArea.TextView.Margin = new Thickness(4, 0);
            TextArea.TextView.BackgroundRenderers.Add(new LineBackgroundRenderer(this));
            TextArea.TextView.LineTransformers.Add(new LineStyleTransformer(this, SecondaryFG));
            TextArea.TextView.ContextRequested += OnTextViewContextRequested;

            if (App.Current?.ActualThemeVariant == ThemeVariant.Dark) {
                _registryOptions = new RegistryOptions(ThemeName.DarkPlus);
            } else {
                _registryOptions = new RegistryOptions(ThemeName.LightPlus);
            }

            _textMate = this.InstallTextMate(_registryOptions);
            UpdateGrammar();
        }

        protected override void OnUnloaded(RoutedEventArgs e) {
            base.OnUnloaded(e);

            TextArea.LeftMargins.Clear();
            TextArea.TextView.BackgroundRenderers.Clear();
            TextArea.TextView.LineTransformers.Clear();
            TextArea.TextView.ContextRequested -= OnTextViewContextRequested;
            _registryOptions = null;
            _textMate.Dispose();
            _textMate = null;
            GC.Collect();
        }

        private void OnTextViewContextRequested(object sender, ContextRequestedEventArgs e) {
            var selected = SelectedText;
            if (string.IsNullOrEmpty(selected)) return;

            var icon = new Avalonia.Controls.Shapes.Path();
            icon.Width = 10;
            icon.Height = 10;
            icon.Stretch = Stretch.Uniform;
            icon.Data = App.Current?.FindResource("Icons.Copy") as StreamGeometry;

            var copy = new MenuItem();
            copy.Header = App.Text("Copy");
            copy.Icon = icon;
            copy.Click += (o, ev) => {
                App.CopyText(selected);
                ev.Handled = true;
            };

            var menu = new ContextMenu();
            menu.Items.Add(copy);
            menu.Open(TextArea.TextView);
            e.Handled = true;
        }

        protected override void OnPropertyChanged(AvaloniaPropertyChangedEventArgs change) {
            base.OnPropertyChanged(change);

            if (change.Property == DiffDataProperty) {
                if (DiffData != null) {
                    var builder = new StringBuilder();
                    foreach (var line in DiffData.Lines) {
                        builder.AppendLine(line.Content);
                    }

                    UpdateGrammar();
                    Text = builder.ToString();                    
                } else {
                    Text = string.Empty;
                }
            } else if (change.Property.Name == "ActualThemeVariant" && change.NewValue != null && _textMate != null) {
                if (App.Current?.ActualThemeVariant == ThemeVariant.Dark) {
                    _textMate.SetTheme(_registryOptions.LoadTheme(ThemeName.DarkPlus));
                } else {
                    _textMate.SetTheme(_registryOptions.LoadTheme(ThemeName.LightPlus));
                }
            }
        }

        private void UpdateGrammar() {
            if (_textMate == null || DiffData == null) return;

            var ext = Path.GetExtension(DiffData.File);
            if (ext == ".h") {
                _textMate.SetGrammar(_registryOptions.GetScopeByLanguageId("cpp"));
            } else {
                _textMate.SetGrammar(_registryOptions.GetScopeByExtension(ext));
            }
        }

        private RegistryOptions _registryOptions;
        private TextMate.Installation _textMate;
    }

    public class SingleSideTextDiffPresenter : TextEditor {
        public class LineNumberMargin : AbstractMargin {
            public LineNumberMargin(SingleSideTextDiffPresenter editor) {
                _editor = editor;
                ClipToBounds = true;
            }

            public override void Render(DrawingContext context) {
                if (_editor.DiffData == null) return;

                var view = TextView;
                if (view != null && view.VisualLinesValid) {
                    var typeface = view.CreateTypeface();
                    var infos = _editor.IsOld ? _editor.DiffData.Old : _editor.DiffData.New;
                    foreach (var line in view.VisualLines) {
                        var index = line.FirstDocumentLine.LineNumber;
                        if (index > infos.Count) break;

                        var info = infos[index - 1];
                        var lineNumber = _editor.IsOld ? info.OldLine : info.NewLine;
                        if (string.IsNullOrEmpty(lineNumber)) continue;

                        var y = line.GetTextLineVisualYPosition(line.TextLines[0], VisualYPosition.TextTop) - view.VerticalOffset;
                        var txt = new FormattedText(
                            lineNumber,
                            CultureInfo.CurrentCulture,
                            FlowDirection.LeftToRight,
                            typeface,
                            _editor.FontSize,
                            _editor.Foreground);
                        context.DrawText(txt, new Point(Bounds.Width - txt.Width, y));
                    }
                }
            }

            protected override Size MeasureOverride(Size availableSize) {
                if (_editor.DiffData == null || TextView == null) {
                    return new Size(32, 0);
                } else {
                    var typeface = TextView.CreateTypeface();
                    var test = new FormattedText(
                            $"{_editor.DiffData.MaxLineNumber}",
                            CultureInfo.CurrentCulture,
                            FlowDirection.LeftToRight,
                            typeface,
                            _editor.FontSize,
                            Brushes.White);
                    return new Size(test.Width, 0);
                }
            }

            private SingleSideTextDiffPresenter _editor;
        }

        public class VerticalSeperatorMargin : AbstractMargin {
            public VerticalSeperatorMargin(SingleSideTextDiffPresenter editor) {
                _editor = editor;
            }

            public override void Render(DrawingContext context) {
                var pen = new Pen(_editor.BorderBrush, 1);
                context.DrawLine(pen, new Point(0, 0), new Point(0, Bounds.Height));
            }

            protected override Size MeasureOverride(Size availableSize) {
                return new Size(1, 0);
            }

            private SingleSideTextDiffPresenter _editor = null;
        }

        public class LineBackgroundRenderer : IBackgroundRenderer {
            private static readonly Brush BG_EMPTY = new SolidColorBrush(Color.FromArgb(60, 0, 0, 0));
            private static readonly Brush BG_ADDED = new SolidColorBrush(Color.FromArgb(60, 0, 255, 0));
            private static readonly Brush BG_DELETED = new SolidColorBrush(Color.FromArgb(60, 255, 0, 0));

            public KnownLayer Layer => KnownLayer.Background;

            public LineBackgroundRenderer(SingleSideTextDiffPresenter editor) {
                _editor = editor;
            }

            public void Draw(TextView textView, DrawingContext drawingContext) {
                if (_editor.Document == null || !textView.VisualLinesValid) return;

                var width = textView.Bounds.Width;
                var infos = _editor.IsOld ? _editor.DiffData.Old : _editor.DiffData.New;
                foreach (var line in textView.VisualLines) {
                    var index = line.FirstDocumentLine.LineNumber;
                    if (index > infos.Count) break;

                    var info = infos[index - 1];
                    var bg = GetBrushByLineType(info.Type);
                    if (bg == null) continue;

                    var y = line.GetTextLineVisualYPosition(line.TextLines[0], VisualYPosition.TextTop) - textView.VerticalOffset;
                    drawingContext.DrawRectangle(bg, null, new Rect(0, y, width, line.Height));
                }
            }

            private IBrush GetBrushByLineType(Models.TextDiffLineType type) {
                switch (type) {
                case Models.TextDiffLineType.None: return BG_EMPTY;
                case Models.TextDiffLineType.Added: return BG_ADDED;
                case Models.TextDiffLineType.Deleted: return BG_DELETED;
                default: return null;
                }
            }

            private SingleSideTextDiffPresenter _editor = null;
        }

        public class LineStyleTransformer : DocumentColorizingTransformer {
            private static readonly Brush HL_ADDED = new SolidColorBrush(Color.FromArgb(90, 0, 255, 0));
            private static readonly Brush HL_DELETED = new SolidColorBrush(Color.FromArgb(80, 255, 0, 0));

            public LineStyleTransformer(SingleSideTextDiffPresenter editor, IBrush indicatorFG) {
                _editor = editor;
                _indicatorFG = indicatorFG;

                var font = App.Current.FindResource("JetBrainsMonoItalic") as FontFamily;
                _indicatorTypeface = new Typeface(font, FontStyle.Italic, FontWeight.Regular);
            }

            protected override void ColorizeLine(DocumentLine line) {
                var infos = _editor.IsOld ? _editor.DiffData.Old : _editor.DiffData.New;
                var idx = line.LineNumber;
                if (idx > infos.Count) return;

                var info = infos[idx - 1];
                if (info.Type == Models.TextDiffLineType.Indicator) {
                    ChangeLinePart(line.Offset, line.EndOffset, v => {
                        v.TextRunProperties.SetForegroundBrush(_indicatorFG);
                        v.TextRunProperties.SetTypeface(_indicatorTypeface);
                    });

                    return;
                }

                if (info.Highlights.Count > 0) {
                    var bg = info.Type == Models.TextDiffLineType.Added ? HL_ADDED : HL_DELETED;
                    foreach (var highlight in info.Highlights) {
                        ChangeLinePart(line.Offset + highlight.Start, line.Offset + highlight.Start + highlight.Count, v => {
                            v.TextRunProperties.SetBackgroundBrush(bg);
                        });
                    }
                }
            }

            private SingleSideTextDiffPresenter _editor;
            private IBrush _indicatorFG = Brushes.DarkGray;
            private Typeface _indicatorTypeface = Typeface.Default;
        }

        public static readonly StyledProperty<bool> IsOldProperty =
            AvaloniaProperty.Register<SingleSideTextDiffPresenter, bool>(nameof(IsOld));

        public bool IsOld {
            get => GetValue(IsOldProperty);
            set => SetValue(IsOldProperty, value);
        }

        public static readonly StyledProperty<ViewModels.TwoSideTextDiff> DiffDataProperty =
            AvaloniaProperty.Register<SingleSideTextDiffPresenter, ViewModels.TwoSideTextDiff>(nameof(DiffData));

        public ViewModels.TwoSideTextDiff DiffData {
            get => GetValue(DiffDataProperty);
            set => SetValue(DiffDataProperty, value);
        }

        public static readonly StyledProperty<IBrush> SecondaryFGProperty =
            AvaloniaProperty.Register<SingleSideTextDiffPresenter, IBrush>(nameof(SecondaryFG), Brushes.Gray);

        public IBrush SecondaryFG {
            get => GetValue(SecondaryFGProperty);
            set => SetValue(SecondaryFGProperty, value);
        }

        public static readonly StyledProperty<Vector> SyncScrollOffsetProperty =
            AvaloniaProperty.Register<SingleSideTextDiffPresenter, Vector>(nameof(SyncScrollOffset));

        public Vector SyncScrollOffset {
            get => GetValue(SyncScrollOffsetProperty);
            set => SetValue(SyncScrollOffsetProperty, value);
        }

        protected override Type StyleKeyOverride => typeof(TextEditor);

        public SingleSideTextDiffPresenter() : base(new TextArea(), new TextDocument()) {
            IsReadOnly = true;
            ShowLineNumbers = false;
            WordWrap = false;            
        }

        protected override void OnLoaded(RoutedEventArgs e) {
            base.OnLoaded(e);

            TextArea.LeftMargins.Add(new LineNumberMargin(this) { Margin = new Thickness(8, 0) });
            TextArea.LeftMargins.Add(new VerticalSeperatorMargin(this));
            TextArea.TextView.Margin = new Thickness(4, 0);
            TextArea.TextView.BackgroundRenderers.Add(new LineBackgroundRenderer(this));
            TextArea.TextView.LineTransformers.Add(new LineStyleTransformer(this, SecondaryFG));
            TextArea.TextView.ContextRequested += OnTextViewContextRequested;
            TextArea.TextView.ScrollOffsetChanged += OnTextViewScrollOffsetChanged;

            if (App.Current?.ActualThemeVariant == ThemeVariant.Dark) {
                _registryOptions = new RegistryOptions(ThemeName.DarkPlus);
            } else {
                _registryOptions = new RegistryOptions(ThemeName.LightPlus);
            }

            _textMate = this.InstallTextMate(_registryOptions);
            UpdateGrammar();
        }

        protected override void OnUnloaded(RoutedEventArgs e) {
            base.OnUnloaded(e);

            TextArea.LeftMargins.Clear();
            TextArea.TextView.BackgroundRenderers.Clear();
            TextArea.TextView.LineTransformers.Clear();
            TextArea.TextView.ContextRequested -= OnTextViewContextRequested;
            TextArea.TextView.ScrollOffsetChanged -= OnTextViewScrollOffsetChanged;
            _registryOptions = null;
            _textMate.Dispose();
            _textMate = null;
            GC.Collect();
        }

        private void OnTextViewScrollOffsetChanged(object sender, EventArgs e) {
            SyncScrollOffset = TextArea.TextView.ScrollOffset;
        }

        private void OnTextViewContextRequested(object sender, ContextRequestedEventArgs e) {
            var selected = SelectedText;
            if (string.IsNullOrEmpty(selected)) return;

            var icon = new Avalonia.Controls.Shapes.Path();
            icon.Width = 10;
            icon.Height = 10;
            icon.Stretch = Stretch.Uniform;
            icon.Data = App.Current?.FindResource("Icons.Copy") as StreamGeometry;

            var copy = new MenuItem();
            copy.Header = App.Text("Copy");
            copy.Icon = icon;
            copy.Click += (o, ev) => {
                App.CopyText(selected);
                ev.Handled = true;
            };

            var menu = new ContextMenu();
            menu.Items.Add(copy);
            menu.Open(TextArea.TextView);
            e.Handled = true;
        }

        protected override void OnPropertyChanged(AvaloniaPropertyChangedEventArgs change) {
            base.OnPropertyChanged(change);

            if (change.Property == DiffDataProperty) {
                if (DiffData != null) {
                    var builder = new StringBuilder();
                    if (IsOld) {
                        foreach (var line in DiffData.Old) {
                            builder.AppendLine(line.Content);
                        }
                    } else {
                        foreach (var line in DiffData.New) {
                            builder.AppendLine(line.Content);
                        }
                    }

                    UpdateGrammar();
                    Text = builder.ToString();
                } else {
                    Text = string.Empty;
                }
            } else if (change.Property == SyncScrollOffsetProperty) {
                if (TextArea.TextView.ScrollOffset != SyncScrollOffset) {
                    IScrollable scrollable = TextArea.TextView;
                    scrollable.Offset = SyncScrollOffset;
                }
            } else if (change.Property.Name == "ActualThemeVariant" && change.NewValue != null && _textMate != null) {
                if (App.Current?.ActualThemeVariant == ThemeVariant.Dark) {
                    _textMate.SetTheme(_registryOptions.LoadTheme(ThemeName.DarkPlus));
                } else {
                    _textMate.SetTheme(_registryOptions.LoadTheme(ThemeName.LightPlus));
                }
            }
        }

        private void UpdateGrammar() {
            if (_textMate == null || DiffData == null) return;

            var ext = Path.GetExtension(DiffData.File);
            if (ext == ".h") {
                _textMate.SetGrammar(_registryOptions.GetScopeByLanguageId("cpp"));
            } else {
                _textMate.SetGrammar(_registryOptions.GetScopeByExtension(ext));
            }
        }

        private RegistryOptions _registryOptions;
        private TextMate.Installation _textMate;
    }

    public partial class TextDiffView : UserControl {
        public static readonly StyledProperty<Models.TextDiff> TextDiffProperty =
            AvaloniaProperty.Register<TextDiffView, Models.TextDiff>(nameof(TextDiff), null);

        public Models.TextDiff TextDiff {
            get => GetValue(TextDiffProperty);
            set => SetValue(TextDiffProperty, value);
        }

        public static readonly StyledProperty<bool> UseCombinedProperty =
            AvaloniaProperty.Register<TextDiffView, bool>(nameof(UseCombined), false);

        public bool UseCombined {
            get => GetValue(UseCombinedProperty);
            set => SetValue(UseCombinedProperty, value);
        }

        public static readonly StyledProperty<Vector> SyncScrollOffsetProperty =
            AvaloniaProperty.Register<TextDiffView, Vector>(nameof(SyncScrollOffset), Vector.Zero);

        public Vector SyncScrollOffset {
            get => GetValue(SyncScrollOffsetProperty);
            set => SetValue(SyncScrollOffsetProperty, value);
        }

        public TextDiffView() {
            InitializeComponent();
        }

        protected override void OnPropertyChanged(AvaloniaPropertyChangedEventArgs change) {
            base.OnPropertyChanged(change);

            if (change.Property == TextDiffProperty || change.Property == UseCombinedProperty) {
                if (TextDiff == null) {
                    Content = null;
                } else if (UseCombined) {
                    Content = new ViewModels.TwoSideTextDiff(TextDiff);
                } else {
                    Content = TextDiff;
                }
            }
        }
    }
}