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

using osu.Game.Beatmaps;
using osu.Game.Rulesets.Objects;
using osu.Game.Rulesets.Objects.Types;
using osu.Game.Rulesets.Taiko.Objects;
using System;
using System.Collections.Generic;
using System.Linq;
using osu.Game.Database;
using osu.Game.IO.Serialization;
using osu.Game.Audio;
using osu.Game.Rulesets.Beatmaps;

namespace osu.Game.Rulesets.Taiko.Beatmaps
{
    internal class TaikoBeatmapConverter : BeatmapConverter<TaikoHitObject>
    {
        /// <summary>
        /// osu! is generally slower than taiko, so a factor is added to increase
        /// speed. This must be used everywhere slider length or beat length is used.
        /// </summary>
        private const float legacy_velocity_multiplier = 1.4f;

        /// <summary>
        /// Because swells are easier in taiko than spinners are in osu!,
        /// legacy taiko multiplies a factor when converting the number of required hits.
        /// </summary>
        private const float swell_hit_multiplier = 1.65f;

        /// <summary>
        /// Base osu! slider scoring distance.
        /// </summary>
        private const float osu_base_scoring_distance = 100;

        /// <summary>
        /// Drum roll distance that results in a duration of 1 speed-adjusted beat length.
        /// </summary>
        private const float taiko_base_distance = 100;

        protected override IEnumerable<Type> ValidConversionTypes { get; } = new[] { typeof(HitObject) };

        protected override Beatmap<TaikoHitObject> ConvertBeatmap(Beatmap original)
        {
            // Rewrite the beatmap info to add the slider velocity multiplier
            BeatmapInfo info = original.BeatmapInfo.DeepClone();
            info.Difficulty.SliderMultiplier *= legacy_velocity_multiplier;

            Beatmap<TaikoHitObject> converted = base.ConvertBeatmap(original);

            // Post processing step to transform hit objects with the same start time into strong hits
            converted.HitObjects = converted.HitObjects.GroupBy(t => t.StartTime).Select(x =>
            {
                TaikoHitObject first = x.First();
                if (x.Skip(1).Any())
                    first.IsStrong = true;
                return first;
            }).ToList();

            return converted;
        }

        protected override IEnumerable<TaikoHitObject> ConvertHitObject(HitObject obj, Beatmap beatmap)
        {
            var distanceData = obj as IHasDistance;
            var repeatsData = obj as IHasRepeats;
            var endTimeData = obj as IHasEndTime;
            var curveData = obj as IHasCurve;

            // Old osu! used hit sounding to determine various hit type information
            SampleInfoList samples = obj.Samples;

            bool strong = samples.Any(s => s.Name == SampleInfo.HIT_FINISH);

            if (distanceData != null)
            {
                int repeats = repeatsData?.RepeatCount ?? 1;

                double speedAdjustment = beatmap.TimingInfo.SpeedMultiplierAt(obj.StartTime);
                double speedAdjustedBeatLength = beatmap.TimingInfo.BeatLengthAt(obj.StartTime) * speedAdjustment;

                // The true distance, accounting for any repeats. This ends up being the drum roll distance later
                double distance = distanceData.Distance * repeats * legacy_velocity_multiplier;

                // The velocity of the taiko hit object - calculated as the velocity of a drum roll
                double taikoVelocity = taiko_base_distance * beatmap.BeatmapInfo.Difficulty.SliderMultiplier * legacy_velocity_multiplier / speedAdjustedBeatLength;
                // The duration of the taiko hit object
                double taikoDuration = distance / taikoVelocity;

                // For some reason, old osu! always uses speedAdjustment to determine the taiko velocity, but
                // only uses it to determine osu! velocity if beatmap version < 8. Let's account for that here.
                if (beatmap.BeatmapInfo.BeatmapVersion >= 8)
                    speedAdjustedBeatLength /= speedAdjustment;

                // The velocity of the osu! hit object - calculated as the velocity of a slider
                double osuVelocity = osu_base_scoring_distance * beatmap.BeatmapInfo.Difficulty.SliderMultiplier * legacy_velocity_multiplier / speedAdjustedBeatLength;
                // The duration of the osu! hit object
                double osuDuration = distance / osuVelocity;

                // If the drum roll is to be split into hit circles, assume the ticks are 1/8 spaced within the duration of one beat
                double tickSpacing = Math.Min(speedAdjustedBeatLength / beatmap.BeatmapInfo.Difficulty.SliderTickRate, taikoDuration / repeats);

                if (tickSpacing > 0 && osuDuration < 2 * speedAdjustedBeatLength)
                {
                    List<SampleInfoList> allSamples = curveData != null ? curveData.RepeatSamples : new List<SampleInfoList>(new[] { samples });

                    int i = 0;
                    for (double j = obj.StartTime; j <= obj.StartTime + taikoDuration + tickSpacing / 8; j += tickSpacing)
                    {
                        SampleInfoList currentSamples = allSamples[i];
                        bool isRim = currentSamples.Any(s => s.Name == SampleInfo.HIT_CLAP || s.Name == SampleInfo.HIT_WHISTLE);
                        strong = currentSamples.Any(s => s.Name == SampleInfo.HIT_FINISH);

                        if (isRim)
                        {
                            yield return new RimHit
                            {
                                StartTime = j,
                                Samples = currentSamples,
                                IsStrong = strong
                            };
                        }
                        else
                        {
                            yield return new CentreHit
                            {
                                StartTime = j,
                                Samples = currentSamples,
                                IsStrong = strong,
                            };
                        }

                        i = (i + 1) % allSamples.Count;
                    }
                }
                else
                {
                    yield return new DrumRoll
                    {
                        StartTime = obj.StartTime,
                        Samples = obj.Samples,
                        IsStrong = strong,
                        Duration = taikoDuration,
                        TickRate = beatmap.BeatmapInfo.Difficulty.SliderTickRate == 3 ? 3 : 4,
                    };
                }
            }
            else if (endTimeData != null)
            {
                double hitMultiplier = BeatmapDifficulty.DifficultyRange(beatmap.BeatmapInfo.Difficulty.OverallDifficulty, 3, 5, 7.5) * swell_hit_multiplier;

                yield return new Swell
                {
                    StartTime = obj.StartTime,
                    Samples = obj.Samples,
                    IsStrong = strong,
                    Duration = endTimeData.Duration,
                    RequiredHits = (int)Math.Max(1, endTimeData.Duration / 1000 * hitMultiplier),
                };
            }
            else
            {
                bool isRim = samples.Any(s => s.Name == SampleInfo.HIT_CLAP || s.Name == SampleInfo.HIT_WHISTLE);

                if (isRim)
                {
                    yield return new RimHit
                    {
                        StartTime = obj.StartTime,
                        Samples = obj.Samples,
                        IsStrong = strong,
                    };
                }
                else
                {
                    yield return new CentreHit
                    {
                        StartTime = obj.StartTime,
                        Samples = obj.Samples,
                        IsStrong = strong,
                    };
                }
            }
        }
    }
}