// 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.Game.Beatmaps;
using osu.Game.Rulesets.Difficulty;
using osu.Game.Rulesets.Difficulty.Preprocessing;
using osu.Game.Rulesets.Difficulty.Skills;
using osu.Game.Rulesets.Mania.Beatmaps;
using osu.Game.Rulesets.Mania.Difficulty.Preprocessing;
using osu.Game.Rulesets.Mania.Difficulty.Skills;
using osu.Game.Rulesets.Mania.MathUtils;
using osu.Game.Rulesets.Mania.Mods;
using osu.Game.Rulesets.Mania.Objects;
using osu.Game.Rulesets.Mania.Scoring;
using osu.Game.Rulesets.Mods;
using osu.Game.Rulesets.Objects;
using osu.Game.Rulesets.Scoring;

namespace osu.Game.Rulesets.Mania.Difficulty
{
    public class ManiaDifficultyCalculator : DifficultyCalculator
    {
        private const double star_scaling_factor = 0.018;

        private readonly bool isForCurrentRuleset;

        public ManiaDifficultyCalculator(Ruleset ruleset, WorkingBeatmap beatmap)
            : base(ruleset, beatmap)
        {
            isForCurrentRuleset = beatmap.BeatmapInfo.Ruleset.Equals(ruleset.RulesetInfo);
        }

        protected override DifficultyAttributes CreateDifficultyAttributes(IBeatmap beatmap, Mod[] mods, Skill[] skills, double clockRate)
        {
            if (beatmap.HitObjects.Count == 0)
                return new ManiaDifficultyAttributes { Mods = mods, Skills = skills };

            HitWindows hitWindows = new ManiaHitWindows();
            hitWindows.SetDifficulty(beatmap.BeatmapInfo.BaseDifficulty.OverallDifficulty);

            return new ManiaDifficultyAttributes
            {
                StarRating = skills[0].DifficultyValue() * star_scaling_factor,
                Mods = mods,
                // Todo: This int cast is temporary to achieve 1:1 results with osu!stable, and should be removed in the future
                GreatHitWindow = (int)(hitWindows.WindowFor(HitResult.Great)) / clockRate,
                MaxCombo = beatmap.HitObjects.Sum(h => h is HoldNote ? 2 : 1),
                Skills = skills
            };
        }

        protected override IEnumerable<DifficultyHitObject> CreateDifficultyHitObjects(IBeatmap beatmap, double clockRate)
        {
            var sortedObjects = beatmap.HitObjects.ToArray();

            LegacySortHelper<HitObject>.Sort(sortedObjects, Comparer<HitObject>.Create((a, b) => (int)Math.Round(a.StartTime) - (int)Math.Round(b.StartTime)));

            for (int i = 1; i < sortedObjects.Length; i++)
                yield return new ManiaDifficultyHitObject(sortedObjects[i], sortedObjects[i - 1], clockRate);
        }

        // Sorting is done in CreateDifficultyHitObjects, since the full list of hitobjects is required.
        protected override IEnumerable<DifficultyHitObject> SortObjects(IEnumerable<DifficultyHitObject> input) => input;

        protected override Skill[] CreateSkills(IBeatmap beatmap) => new Skill[]
        {
            new Strain(((ManiaBeatmap)beatmap).TotalColumns)
        };

        protected override Mod[] DifficultyAdjustmentMods
        {
            get
            {
                var mods = new Mod[]
                {
                    new ManiaModDoubleTime(),
                    new ManiaModHalfTime(),
                    new ManiaModEasy(),
                    new ManiaModHardRock(),
                };

                if (isForCurrentRuleset)
                    return mods;

                // if we are a convert, we can be played in any key mod.
                return mods.Concat(new Mod[]
                {
                    new ManiaModKey1(),
                    new ManiaModKey2(),
                    new ManiaModKey3(),
                    new ManiaModKey4(),
                    new ManiaModKey5(),
                    new ManiaModKey6(),
                    new ManiaModKey7(),
                    new ManiaModKey8(),
                    new ManiaModKey9(),
                }).ToArray();
            }
        }
    }
}