// 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.Collections.Generic;
using osu.Game.Rulesets.Difficulty.Preprocessing;
using osu.Game.Rulesets.Taiko.Difficulty.Utils;

namespace osu.Game.Rulesets.Taiko.Difficulty.Preprocessing.Rhythm.Data
{
    /// <summary>
    /// Represents a group of <see cref="TaikoDifficultyHitObject"/>s with no rhythm variation.
    /// </summary>
    public class SameRhythmGroupedHitObjects : IHasInterval
    {
        public List<TaikoDifficultyHitObject> Children { get; private set; }

        public TaikoDifficultyHitObject FirstHitObject => Children[0];

        public SameRhythmGroupedHitObjects? Previous;

        /// <summary>
        /// <see cref="DifficultyHitObject.StartTime"/> of the first hit object.
        /// </summary>
        public double StartTime => Children[0].StartTime;

        /// <summary>
        /// The interval between the first and final hit object within this group.
        /// </summary>
        public double Duration => Children[^1].StartTime - Children[0].StartTime;

        /// <summary>
        /// The interval in ms of each hit object in this <see cref="SameRhythmGroupedHitObjects"/>. This is only defined if there is
        /// more than two hit objects in this <see cref="SameRhythmGroupedHitObjects"/>.
        /// </summary>
        public double? HitObjectInterval;

        /// <summary>
        /// The ratio of <see cref="HitObjectInterval"/> between this and the previous <see cref="SameRhythmGroupedHitObjects"/>. In the
        /// case where one or both of the <see cref="HitObjectInterval"/> is undefined, this will have a value of 1.
        /// </summary>
        public double HitObjectIntervalRatio;

        /// <inheritdoc/>
        public double Interval { get; private set; }

        public SameRhythmGroupedHitObjects(SameRhythmGroupedHitObjects? previous, List<TaikoDifficultyHitObject> children)
        {
            Previous = previous;
            Children = children;

            // Calculate the average interval between hitobjects, or null if there are fewer than two
            HitObjectInterval = Children.Count < 2 ? null : Duration / (Children.Count - 1);

            // Calculate the ratio between this group's interval and the previous group's interval
            HitObjectIntervalRatio = Previous?.HitObjectInterval != null && HitObjectInterval != null
                ? HitObjectInterval.Value / Previous.HitObjectInterval.Value
                : 1;

            // Calculate the interval from the previous group's start time
            Interval = Previous != null ? StartTime - Previous.StartTime : double.PositiveInfinity;
        }
    }
}