// 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.Linq;
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.Game.Graphics;
using osu.Game.Graphics.Sprites;
using osu.Game.Rulesets.Scoring;

namespace osu.Game.Screens.Ranking.Statistics
{
    /// <summary>
    /// A graph which displays the distribution of hit timing in a series of <see cref="HitEvent"/>s.
    /// </summary>
    public class HitEventTimingDistributionGraph : CompositeDrawable
    {
        /// <summary>
        /// The number of bins on each side of the timing distribution.
        /// </summary>
        private const int timing_distribution_bins = 50;

        /// <summary>
        /// The total number of bins in the timing distribution, including bins on both sides and the centre bin at 0.
        /// </summary>
        private const int total_timing_distribution_bins = timing_distribution_bins * 2 + 1;

        /// <summary>
        /// The centre bin, with a timing distribution very close to/at 0.
        /// </summary>
        private const int timing_distribution_centre_bin_index = timing_distribution_bins;

        /// <summary>
        /// The number of data points shown on each side of the axis below the graph.
        /// </summary>
        private const float axis_points = 5;

        private readonly IReadOnlyList<HitEvent> hitEvents;

        /// <summary>
        /// Creates a new <see cref="HitEventTimingDistributionGraph"/>.
        /// </summary>
        /// <param name="hitEvents">The <see cref="HitEvent"/>s to display the timing distribution of.</param>
        public HitEventTimingDistributionGraph(IReadOnlyList<HitEvent> hitEvents)
        {
            this.hitEvents = hitEvents.Where(e => !(e.HitObject.HitWindows is HitWindows.EmptyHitWindows) && e.Result.IsHit()).ToList();
        }

        [BackgroundDependencyLoader]
        private void load()
        {
            if (hitEvents == null || hitEvents.Count == 0)
                return;

            int[] bins = new int[total_timing_distribution_bins];

            double binSize = Math.Ceiling(hitEvents.Max(e => Math.Abs(e.TimeOffset)) / timing_distribution_bins);

            // Prevent div-by-0 by enforcing a minimum bin size
            binSize = Math.Max(1, binSize);

            bool roundUp = true;

            foreach (var e in hitEvents)
            {
                double binOffset = e.TimeOffset / binSize;

                // .NET's round midpoint handling doesn't provide a behaviour that works amazingly for display
                // purposes here. We want midpoint rounding to roughly distribute evenly to each adjacent bucket
                // so the easiest way is to cycle between downwards and upwards rounding as we process events.
                if (Math.Abs(binOffset - (int)binOffset) == 0.5)
                {
                    binOffset = (int)binOffset + Math.Sign(binOffset) * (roundUp ? 1 : 0);
                    roundUp = !roundUp;
                }

                bins[timing_distribution_centre_bin_index + (int)Math.Round(binOffset, MidpointRounding.AwayFromZero)]++;
            }

            int maxCount = bins.Max();
            var bars = new Drawable[total_timing_distribution_bins];
            for (int i = 0; i < bars.Length; i++)
                bars[i] = new Bar { Height = Math.Max(0.05f, (float)bins[i] / maxCount) };

            Container axisFlow;

            InternalChild = new GridContainer
            {
                Anchor = Anchor.Centre,
                Origin = Anchor.Centre,
                RelativeSizeAxes = Axes.Both,
                Width = 0.8f,
                Content = new[]
                {
                    new Drawable[]
                    {
                        new GridContainer
                        {
                            RelativeSizeAxes = Axes.Both,
                            Content = new[] { bars }
                        }
                    },
                    new Drawable[]
                    {
                        axisFlow = new Container
                        {
                            RelativeSizeAxes = Axes.X,
                            AutoSizeAxes = Axes.Y
                        }
                    },
                },
                RowDimensions = new[]
                {
                    new Dimension(),
                    new Dimension(GridSizeMode.AutoSize),
                }
            };

            // Our axis will contain one centre element + 5 points on each side, each with a value depending on the number of bins * bin size.
            double maxValue = timing_distribution_bins * binSize;
            double axisValueStep = maxValue / axis_points;

            axisFlow.Add(new OsuSpriteText
            {
                Anchor = Anchor.Centre,
                Origin = Anchor.Centre,
                Text = "0",
                Font = OsuFont.GetFont(size: 12, weight: FontWeight.SemiBold)
            });

            for (int i = 1; i <= axis_points; i++)
            {
                double axisValue = i * axisValueStep;
                float position = (float)(axisValue / maxValue);
                float alpha = 1f - position * 0.8f;

                axisFlow.Add(new OsuSpriteText
                {
                    Anchor = Anchor.Centre,
                    Origin = Anchor.Centre,
                    RelativePositionAxes = Axes.X,
                    X = -position / 2,
                    Alpha = alpha,
                    Text = axisValue.ToString("-0"),
                    Font = OsuFont.GetFont(size: 12, weight: FontWeight.SemiBold)
                });

                axisFlow.Add(new OsuSpriteText
                {
                    Anchor = Anchor.Centre,
                    Origin = Anchor.Centre,
                    RelativePositionAxes = Axes.X,
                    X = position / 2,
                    Alpha = alpha,
                    Text = axisValue.ToString("+0"),
                    Font = OsuFont.GetFont(size: 12, weight: FontWeight.SemiBold)
                });
            }
        }

        private class Bar : CompositeDrawable
        {
            public Bar()
            {
                Anchor = Anchor.BottomCentre;
                Origin = Anchor.BottomCentre;

                RelativeSizeAxes = Axes.Both;

                Padding = new MarginPadding { Horizontal = 1 };

                InternalChild = new Circle
                {
                    RelativeSizeAxes = Axes.Both,
                    Colour = Color4Extensions.FromHex("#66FFCC")
                };
            }
        }
    }
}