// Copyright (c) 2007-2017 ppy Pty Ltd <contact@ppy.sh>.
// Licensed under the MIT Licence - https://raw.githubusercontent.com/ppy/osu/master/LICENCE

using System.Collections.Generic;
using OpenTK.Input;
using osu.Framework.Configuration;
using osu.Framework.Graphics;
using osu.Framework.Graphics.Transforms;
using osu.Framework.Input;
using osu.Framework.Lists;
using osu.Framework.MathUtils;
using osu.Game.Rulesets.Objects.Drawables;
using osu.Game.Rulesets.Timing;

namespace osu.Game.Rulesets.UI
{
    /// <summary>
    /// A type of <see cref="Playfield"/> specialized towards scrolling <see cref="DrawableHitObject"/>s.
    /// </summary>
    public class ScrollingPlayfield : Playfield
    {
        /// <summary>
        /// The default span of time visible by the length of the scrolling axes.
        /// This is clamped between <see cref="time_span_min"/> and <see cref="time_span_max"/>.
        /// </summary>
        private const double time_span_default = 1500;
        /// <summary>
        /// The minimum span of time that may be visible by the length of the scrolling axes.
        /// </summary>
        private const double time_span_min = 50;
        /// <summary>
        /// The maximum span of time that may be visible by the length of the scrolling axes.
        /// </summary>
        private const double time_span_max = 10000;
        /// <summary>
        /// The step increase/decrease of the span of time visible by the length of the scrolling axes.
        /// </summary>
        private const double time_span_step = 50;

        /// <summary>
        /// The span of time that is visible by the length of the scrolling axes.
        /// For example, only hit objects with start time less than or equal to 1000 will be visible with <see cref="VisibleTimeRange"/> = 1000.
        /// </summary>
        public readonly BindableDouble VisibleTimeRange = new BindableDouble(time_span_default)
        {
            Default = time_span_default,
            MinValue = time_span_min,
            MaxValue = time_span_max
        };

        /// <summary>
        /// The container that contains the <see cref="SpeedAdjustmentContainer"/>s and <see cref="DrawableHitObject"/>s.
        /// </summary>
        public new readonly ScrollingHitObjectContainer HitObjects;

        /// <summary>
        /// Creates a new <see cref="ScrollingPlayfield"/>.
        /// </summary>
        /// <param name="scrollingAxes">The axes on which <see cref="DrawableHitObject"/>s in this container should scroll.</param>
        /// <param name="customWidth">Whether we want our internal coordinate system to be scaled to a specified width</param>
        protected ScrollingPlayfield(Direction scrollingDirection, float? customWidth = null)
            : base(customWidth)
        {
            base.HitObjects = HitObjects = new ScrollingHitObjectContainer(scrollingDirection) { RelativeSizeAxes = Axes.Both };
            HitObjects.TimeRange.BindTo(VisibleTimeRange);
        }

        private List<ScrollingPlayfield> nestedPlayfields;
        /// <summary>
        /// All the <see cref="ScrollingPlayfield"/>s nested inside this playfield.
        /// </summary>
        public IEnumerable<ScrollingPlayfield> NestedPlayfields => nestedPlayfields;

        /// <summary>
        /// Adds a <see cref="ScrollingPlayfield"/> to this playfield. The nested <see cref="ScrollingPlayfield"/>
        /// will be given all of the same speed adjustments as this playfield.
        /// </summary>
        /// <param name="otherPlayfield">The <see cref="ScrollingPlayfield"/> to add.</param>
        protected void AddNested(ScrollingPlayfield otherPlayfield)
        {
            if (nestedPlayfields == null)
                nestedPlayfields = new List<ScrollingPlayfield>();

            nestedPlayfields.Add(otherPlayfield);
        }

        protected override bool OnKeyDown(InputState state, KeyDownEventArgs args)
        {
            if (state.Keyboard.ControlPressed)
            {
                switch (args.Key)
                {
                    case Key.Minus:
                        transformVisibleTimeRangeTo(VisibleTimeRange + time_span_step, 200, Easing.OutQuint);
                        break;
                    case Key.Plus:
                        transformVisibleTimeRangeTo(VisibleTimeRange - time_span_step, 200, Easing.OutQuint);
                        break;
                }
            }

            return false;
        }

        private void transformVisibleTimeRangeTo(double newTimeRange, double duration = 0, Easing easing = Easing.None)
        {
            this.TransformTo(this.PopulateTransform(new TransformVisibleTimeRange(), newTimeRange, duration, easing));
        }

        private class TransformVisibleTimeRange : Transform<double, ScrollingPlayfield>
        {
            private double valueAt(double time)
            {
                if (time < StartTime) return StartValue;
                if (time >= EndTime) return EndValue;

                return Interpolation.ValueAt(time, StartValue, EndValue, StartTime, EndTime, Easing);
            }

            public override string TargetMember => "VisibleTimeRange.Value";

            protected override void Apply(ScrollingPlayfield d, double time) => d.VisibleTimeRange.Value = valueAt(time);
            protected override void ReadIntoStartValue(ScrollingPlayfield d) => StartValue = d.VisibleTimeRange.Value;
        }

        public class ScrollingHitObjectContainer : HitObjectContainer
        {
            public readonly BindableDouble TimeRange = new BindableDouble
            {
                MinValue = 0,
                MaxValue = double.MaxValue
            };

            public readonly SortedList<MultiplierControlPoint> ControlPoints = new SortedList<MultiplierControlPoint>();

            private readonly Direction scrollingDirection;

            public ScrollingHitObjectContainer(Direction scrollingDirection)
            {
                this.scrollingDirection = scrollingDirection;

                RelativeSizeAxes = Axes.Both;
            }

            protected override void UpdateAfterChildren()
            {
                base.UpdateAfterChildren();

                var currentMultiplier = controlPointAt(Time.Current);

                foreach (var obj in AliveObjects)
                {
                    var relativePosition = (Time.Current - obj.HitObject.StartTime) / (TimeRange / currentMultiplier.Multiplier);

                    // Todo: We may need to consider scale here
                    var finalPosition = (float)relativePosition * DrawSize;

                    switch (scrollingDirection)
                    {
                        case Direction.Horizontal:
                            obj.X = finalPosition.X;
                            break;
                        case Direction.Vertical:
                            obj.Y = finalPosition.Y;
                            break;
                    }
                }
            }

            private readonly MultiplierControlPoint searchingPoint = new MultiplierControlPoint();
            private MultiplierControlPoint controlPointAt(double time)
            {
                if (ControlPoints.Count == 0)
                    return new MultiplierControlPoint(double.MinValue);

                if (time < ControlPoints[0].StartTime)
                    return ControlPoints[0];

                searchingPoint.StartTime = time;

                int index = ControlPoints.BinarySearch(searchingPoint);
                if (index < 0)
                    index = ~index - 1;

                return ControlPoints[index];
            }
        }
    }
}