// Copyright (c) ppy Pty Ltd <contact@ppy.sh>. Licensed under the MIT Licence.
// See the LICENCE file in the repository root for full licence text.

using System;
using System.Collections.Generic;
using System.Diagnostics;
using osu.Framework.Allocation;
using osu.Framework.Extensions.Color4Extensions;
using osu.Framework.Graphics;
using osu.Framework.Graphics.Containers;
using osu.Framework.Graphics.Shapes;
using osu.Framework.Layout;
using osu.Game.Rulesets.Osu.Scoring;
using osuTK;
using osuTK.Graphics;

namespace osu.Game.Rulesets.Osu.Statistics
{
    public class Heatmap : CompositeDrawable
    {
        /// <summary>
        /// Size of the inner circle containing the "hit" points, relative to the size of this <see cref="Heatmap"/>.
        /// All other points outside of the inner circle are "miss" points.
        /// </summary>
        private const float inner_portion = 0.8f;

        private const float rotation = 45;
        private const float point_size = 4;

        private readonly IReadOnlyList<HitOffset> offsets;
        private Container<HitPoint> allPoints;

        private readonly LayoutValue sizeLayout = new LayoutValue(Invalidation.DrawSize);

        public Heatmap(IReadOnlyList<HitOffset> offsets)
        {
            this.offsets = offsets;

            AddLayout(sizeLayout);
        }

        [BackgroundDependencyLoader]
        private void load()
        {
            InternalChild = new Container
            {
                Anchor = Anchor.Centre,
                Origin = Anchor.Centre,
                RelativeSizeAxes = Axes.Both,
                FillMode = FillMode.Fit,
                Children = new Drawable[]
                {
                    new CircularContainer
                    {
                        Anchor = Anchor.Centre,
                        Origin = Anchor.Centre,
                        RelativeSizeAxes = Axes.Both,
                        Size = new Vector2(inner_portion),
                        Masking = true,
                        BorderThickness = 2f,
                        BorderColour = Color4.White,
                        Child = new Box
                        {
                            RelativeSizeAxes = Axes.Both,
                            Colour = Color4Extensions.FromHex("#202624")
                        }
                    },
                    new Container
                    {
                        RelativeSizeAxes = Axes.Both,
                        Masking = true,
                        Children = new Drawable[]
                        {
                            new Box
                            {
                                Anchor = Anchor.Centre,
                                Origin = Anchor.Centre,
                                RelativeSizeAxes = Axes.Y,
                                Height = 2, // We're rotating along a diagonal - we don't really care how big this is.
                                Width = 1f,
                                Rotation = -rotation,
                                Alpha = 0.3f,
                            },
                            new Box
                            {
                                Anchor = Anchor.Centre,
                                Origin = Anchor.Centre,
                                RelativeSizeAxes = Axes.Y,
                                Height = 2, // We're rotating along a diagonal - we don't really care how big this is.
                                Width = 1f,
                                Rotation = rotation
                            },
                            new Box
                            {
                                Anchor = Anchor.TopRight,
                                Origin = Anchor.TopRight,
                                Width = 10,
                                Height = 2f,
                            },
                            new Box
                            {
                                Anchor = Anchor.TopRight,
                                Origin = Anchor.TopRight,
                                Y = -1,
                                Width = 2f,
                                Height = 10,
                            }
                        }
                    },
                    allPoints = new Container<HitPoint>
                    {
                        RelativeSizeAxes = Axes.Both
                    }
                }
            };
        }

        protected override void Update()
        {
            base.Update();
            validateHitPoints();
        }

        private void validateHitPoints()
        {
            if (sizeLayout.IsValid)
                return;

            allPoints.Clear();

            // Since the content is fit, both dimensions should have the same size.
            float size = allPoints.DrawSize.X;

            Vector2 centre = new Vector2(size / 2);
            int rows = (int)Math.Ceiling(size / point_size);
            int cols = (int)Math.Ceiling(size / point_size);

            for (int r = 0; r < rows; r++)
            {
                for (int c = 0; c < cols; c++)
                {
                    Vector2 pos = new Vector2(c * point_size, r * point_size);
                    HitPointType pointType = HitPointType.Hit;

                    if (Vector2.Distance(pos, centre) > size * inner_portion / 2)
                        pointType = HitPointType.Miss;

                    allPoints.Add(new HitPoint(pos, pointType)
                    {
                        Size = new Vector2(point_size),
                        Colour = pointType == HitPointType.Hit ? new Color4(102, 255, 204, 255) : new Color4(255, 102, 102, 255)
                    });
                }
            }

            foreach (var o in offsets)
                AddPoint(o.Position1, o.Position2, o.HitPosition, o.Radius);

            sizeLayout.Validate();
        }

        protected void AddPoint(Vector2 start, Vector2 end, Vector2 hitPoint, float radius)
        {
            if (allPoints.Count == 0)
                return;

            double angle1 = Math.Atan2(end.Y - hitPoint.Y, hitPoint.X - end.X); // Angle between the end point and the hit point.
            double angle2 = Math.Atan2(end.Y - start.Y, start.X - end.X); // Angle between the end point and the start point.
            double finalAngle = angle2 - angle1; // Angle between start, end, and hit points.

            float normalisedDistance = Vector2.Distance(hitPoint, end) / radius;

            // Since the content is fit, both dimensions should have the same size.
            float size = allPoints.DrawSize.X;

            // Find the most relevant hit point.
            double minDist = double.PositiveInfinity;
            HitPoint point = null;

            foreach (var p in allPoints)
            {
                Vector2 localCentre = new Vector2(size / 2);
                float localRadius = localCentre.X * inner_portion * normalisedDistance;
                double localAngle = finalAngle + 3 * Math.PI / 4;
                Vector2 localPoint = localCentre + localRadius * new Vector2((float)Math.Cos(localAngle), (float)Math.Sin(localAngle));

                float dist = Vector2.Distance(p.DrawPosition + p.DrawSize / 2, localPoint);

                if (dist < minDist)
                {
                    minDist = dist;
                    point = p;
                }
            }

            Debug.Assert(point != null);
            point.Increment();
        }

        private class HitPoint : Circle
        {
            private readonly HitPointType pointType;

            public HitPoint(Vector2 position, HitPointType pointType)
            {
                this.pointType = pointType;

                Position = position;
                Alpha = 0;
            }

            public void Increment()
            {
                if (Alpha < 1)
                    Alpha += 0.1f;
                else if (pointType == HitPointType.Hit)
                    Colour = ((Color4)Colour).Lighten(0.1f);
            }
        }

        private enum HitPointType
        {
            Hit,
            Miss
        }
    }
}