using System;
using System.Collections;
using System.Collections.Generic;
using System.Collections.Specialized;
using System.Linq;
using System.Windows;
using System.Windows.Input;
using System.Windows.Media;
using MergeHub.Models;

namespace MergeHub.Views.Controls
{
    /// <summary>
    /// 파일 전체의 변경 분포를 세로 막대로 축소해 보여준다(목업 ③ 코드 미니맵).
    /// 클릭하면 그 위치의 줄을 요청한다 - 실제 스크롤은 화면 쪽에서 처리한다.
    /// </summary>
    public sealed class ChangeMiniMap : FrameworkElement
    {
        private const double MinTickHeight = 2.0;

        private static readonly Brush TrackBrush = Freeze(new SolidColorBrush(Color.FromArgb(0x22, 0x80, 0x80, 0x80)));
        private static readonly Pen SelectionPen = Freeze(new Pen(new SolidColorBrush(Color.FromRgb(0x2E, 0x86, 0xDE)), 1.5));

        /// <summary>
        /// 범례·코드 패널과 같은 색을 쓰되, 미니맵은 얇아서 옅은 알파로는 안 보인다.
        /// 그래서 같은 색상값을 불투명하게 올려 쓴다.
        /// </summary>
        private static readonly Brush ChangedBrush = Freeze(new SolidColorBrush(Color.FromRgb(0xE0, 0xA0, 0x20)));
        private static readonly Brush AppliedBrush = Freeze(new SolidColorBrush(Color.FromRgb(0x2E, 0xA0, 0x43)));
        private static readonly Brush EditedBrush = Freeze(new SolidColorBrush(Color.FromRgb(0x9B, 0x59, 0xB6)));
        private static readonly Brush AddedBrush = Freeze(new SolidColorBrush(Color.FromRgb(0x2E, 0x86, 0xDE)));
        private static readonly Brush RemovedBrush = Freeze(new SolidColorBrush(Color.FromRgb(0xD1, 0x4B, 0x4B)));
        private static readonly Brush MovedBrush = Freeze(new SolidColorBrush(Color.FromRgb(0x00, 0xA0, 0xA8)));

        private static Brush BrushFor(LineHighlight highlight) => highlight switch
        {
            LineHighlight.Applied => AppliedBrush,
            LineHighlight.Edited => EditedBrush,
            LineHighlight.Added => AddedBrush,
            LineHighlight.Removed => RemovedBrush,
            LineHighlight.Moved => MovedBrush,
            _ => ChangedBrush
        };

        private INotifyCollectionChanged? _observed;

        public ChangeMiniMap()
        {
            Cursor = Cursors.Hand;
            Width = 14;
            ToolTip = "변경 분포 - 클릭하면 해당 줄로 이동";
        }

        /// <summary>클릭한 지점에 해당하는 줄이 선택되었을 때 발생.</summary>
        public event EventHandler<MergeLine>? LineRequested;

        public static readonly DependencyProperty SourceProperty = DependencyProperty.Register(
            nameof(Source), typeof(IEnumerable), typeof(ChangeMiniMap),
            new FrameworkPropertyMetadata(null, FrameworkPropertyMetadataOptions.AffectsRender, OnSourceChanged));

        public IEnumerable? Source
        {
            get => (IEnumerable?)GetValue(SourceProperty);
            set => SetValue(SourceProperty, value);
        }

        /// <summary>
        /// 줄 내용이 바뀌어도 컬렉션 자체는 그대로라 다시 그릴 계기가 없다.
        /// ViewModel 이 편집할 때마다 이 값을 올려서 갱신을 알린다.
        /// </summary>
        public static readonly DependencyProperty VersionProperty = DependencyProperty.Register(
            nameof(Version), typeof(int), typeof(ChangeMiniMap),
            new FrameworkPropertyMetadata(0, FrameworkPropertyMetadataOptions.AffectsRender));

        public int Version
        {
            get => (int)GetValue(VersionProperty);
            set => SetValue(VersionProperty, value);
        }

        public static readonly DependencyProperty SelectedLineProperty = DependencyProperty.Register(
            nameof(SelectedLine), typeof(MergeLine), typeof(ChangeMiniMap),
            new FrameworkPropertyMetadata(null, FrameworkPropertyMetadataOptions.AffectsRender));

        public MergeLine? SelectedLine
        {
            get => (MergeLine?)GetValue(SelectedLineProperty);
            set => SetValue(SelectedLineProperty, value);
        }

        private static void OnSourceChanged(DependencyObject d, DependencyPropertyChangedEventArgs e)
        {
            if (d is not ChangeMiniMap map) return;

            if (map._observed is not null)
                map._observed.CollectionChanged -= map.OnCollectionChanged;

            map._observed = e.NewValue as INotifyCollectionChanged;

            if (map._observed is not null)
                map._observed.CollectionChanged += map.OnCollectionChanged;

            map.InvalidateVisual();
        }

        private void OnCollectionChanged(object? sender, NotifyCollectionChangedEventArgs e) => InvalidateVisual();

        protected override void OnMouseLeftButtonDown(MouseButtonEventArgs e)
        {
            base.OnMouseLeftButtonDown(e);

            var lines = Snapshot();
            if (lines.Count == 0 || ActualHeight <= 0) return;

            var ratio = Math.Min(1, Math.Max(0, e.GetPosition(this).Y / ActualHeight));
            var index = Math.Min(lines.Count - 1, (int)(ratio * lines.Count));

            LineRequested?.Invoke(this, lines[index]);
            e.Handled = true;
        }

        protected override void OnRender(DrawingContext dc)
        {
            var w = ActualWidth;
            var h = ActualHeight;
            if (w <= 0 || h <= 0) return;

            dc.DrawRectangle(TrackBrush, null, new Rect(0, 0, w, h));

            var lines = Snapshot();
            if (lines.Count == 0) return;

            var step = h / lines.Count;
            var tick = Math.Max(MinTickHeight, step);

            for (var i = 0; i < lines.Count; i++)
            {
                var highlight = lines[i].Highlight;
                if (highlight == LineHighlight.None || highlight == LineHighlight.Ignored) continue;

                // 코드 패널의 줄 배경과 같은 기준을 쓴다.
                // 반영한 줄은 그 즉시 초록으로 바뀌어야 하므로 IsDifferent 가 아니라 Highlight 를 본다.
                dc.DrawRectangle(BrushFor(highlight), null, new Rect(2, i * step, w - 4, tick));
            }

            // 지금 보고 있는 줄 위치
            var selected = SelectedLine;
            if (selected is null) return;

            var selectedIndex = lines.IndexOf(selected);
            if (selectedIndex < 0) return;

            var y = selectedIndex * step + tick / 2;
            dc.DrawLine(SelectionPen, new Point(0, y), new Point(w, y));
        }

        private List<MergeLine> Snapshot()
        {
            if (Source is null) return new List<MergeLine>();
            return Source.OfType<MergeLine>().ToList();
        }

        private static T Freeze<T>(T freezable) where T : Freezable
        {
            freezable.Freeze();
            return freezable;
        }
    }
}