// 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.Diagnostics;
using System.Diagnostics.Contracts;
using System.Linq;
using osu.Framework.Bindables;
using osu.Framework.Utils;
using osu.Game.Beatmaps;
using osu.Game.Extensions;
using osu.Game.Online.Spectator;
using osu.Game.Rulesets.Judgements;
using osu.Game.Rulesets.Mods;
using osu.Game.Rulesets.Objects;
using osu.Game.Rulesets.Replays;
using osu.Game.Scoring;
using osu.Framework.Localisation;
using osu.Game.Localisation;

namespace osu.Game.Rulesets.Scoring
{
    public class ScoreProcessor : JudgementProcessor
    {
        private const double max_score = 1000000;

        /// <summary>
        /// Invoked when this <see cref="ScoreProcessor"/> was reset from a replay frame.
        /// </summary>
        public event Action? OnResetFromReplayFrame;

        /// <summary>
        /// The current total score.
        /// </summary>
        public readonly BindableDouble TotalScore = new BindableDouble { MinValue = 0 };

        /// <summary>
        /// The current accuracy.
        /// </summary>
        public readonly BindableDouble Accuracy = new BindableDouble(1) { MinValue = 0, MaxValue = 1 };

        /// <summary>
        /// The current combo.
        /// </summary>
        public readonly BindableInt Combo = new BindableInt();

        /// <summary>
        /// The current selected mods
        /// </summary>
        public readonly Bindable<IReadOnlyList<Mod>> Mods = new Bindable<IReadOnlyList<Mod>>(Array.Empty<Mod>());

        /// <summary>
        /// The current rank.
        /// </summary>
        public readonly Bindable<ScoreRank> Rank = new Bindable<ScoreRank>(ScoreRank.X);

        /// <summary>
        /// The highest combo achieved by this score.
        /// </summary>
        public readonly BindableInt HighestCombo = new BindableInt();

        /// <summary>
        /// The <see cref="ScoringMode"/> used to calculate scores.
        /// </summary>
        public readonly Bindable<ScoringMode> Mode = new Bindable<ScoringMode>();

        /// <summary>
        /// The <see cref="HitEvent"/>s collected during gameplay thus far.
        /// Intended for use with various statistics displays.
        /// </summary>
        public IReadOnlyList<HitEvent> HitEvents => hitEvents;

        /// <summary>
        /// The default portion of <see cref="max_score"/> awarded for hitting <see cref="HitObject"/>s accurately. Defaults to 30%.
        /// </summary>
        protected virtual double DefaultAccuracyPortion => 0.3;

        /// <summary>
        /// The default portion of <see cref="max_score"/> awarded for achieving a high combo. Default to 70%.
        /// </summary>
        protected virtual double DefaultComboPortion => 0.7;

        /// <summary>
        /// An arbitrary multiplier to scale scores in the <see cref="ScoringMode.Classic"/> scoring mode.
        /// </summary>
        protected virtual double ClassicScoreMultiplier => 36;

        private readonly Ruleset ruleset;
        private readonly double accuracyPortion;
        private readonly double comboPortion;

        /// <summary>
        /// Scoring values for a perfect play.
        /// </summary>
        public ScoringValues MaximumScoringValues
        {
            get
            {
                if (!beatmapApplied)
                    throw new InvalidOperationException($"Cannot access maximum scoring values before calling {nameof(ApplyBeatmap)}.");

                return maximumScoringValues;
            }
        }

        private ScoringValues maximumScoringValues;

        /// <summary>
        /// Scoring values for the current play assuming all perfect hits.
        /// </summary>
        /// <remarks>
        /// This is only used to determine the accuracy with respect to the current point in time for an ongoing play session.
        /// </remarks>
        private ScoringValues currentMaximumScoringValues;

        /// <summary>
        /// Scoring values for the current play.
        /// </summary>
        private ScoringValues currentScoringValues;

        /// <summary>
        /// The maximum <see cref="HitResult"/> of a basic (non-tick and non-bonus) hitobject.
        /// Only populated via <see cref="ComputeScore(osu.Game.Rulesets.Scoring.ScoringMode,osu.Game.Scoring.ScoreInfo)"/> or <see cref="ResetFromReplayFrame"/>.
        /// </summary>
        private HitResult? maxBasicResult;

        private bool beatmapApplied;

        private readonly Dictionary<HitResult, int> scoreResultCounts = new Dictionary<HitResult, int>();
        private readonly Dictionary<HitResult, int> maximumResultCounts = new Dictionary<HitResult, int>();

        private readonly List<HitEvent> hitEvents = new List<HitEvent>();
        private HitObject? lastHitObject;

        private double scoreMultiplier = 1;

        public ScoreProcessor(Ruleset ruleset)
        {
            this.ruleset = ruleset;

            accuracyPortion = DefaultAccuracyPortion;
            comboPortion = DefaultComboPortion;

            if (!Precision.AlmostEquals(1.0, accuracyPortion + comboPortion))
                throw new InvalidOperationException($"{nameof(DefaultAccuracyPortion)} + {nameof(DefaultComboPortion)} must equal 1.");

            Combo.ValueChanged += combo => HighestCombo.Value = Math.Max(HighestCombo.Value, combo.NewValue);
            Accuracy.ValueChanged += accuracy =>
            {
                Rank.Value = rankFrom(accuracy.NewValue);
                foreach (var mod in Mods.Value.OfType<IApplicableToScoreProcessor>())
                    Rank.Value = mod.AdjustRank(Rank.Value, accuracy.NewValue);
            };

            Mode.ValueChanged += _ => updateScore();
            Mods.ValueChanged += mods =>
            {
                scoreMultiplier = 1;

                foreach (var m in mods.NewValue)
                    scoreMultiplier *= m.ScoreMultiplier;

                updateScore();
            };
        }

        public override void ApplyBeatmap(IBeatmap beatmap)
        {
            base.ApplyBeatmap(beatmap);
            beatmapApplied = true;
        }

        protected sealed override void ApplyResultInternal(JudgementResult result)
        {
            result.ComboAtJudgement = Combo.Value;
            result.HighestComboAtJudgement = HighestCombo.Value;

            if (result.FailedAtJudgement)
                return;

            scoreResultCounts[result.Type] = scoreResultCounts.GetValueOrDefault(result.Type) + 1;

            // Always update the maximum scoring values.
            applyResult(result.Judgement.MaxResult, ref currentMaximumScoringValues);
            currentMaximumScoringValues.MaxCombo += result.Judgement.MaxResult.IncreasesCombo() ? 1 : 0;

            if (!result.Type.IsScorable())
                return;

            if (result.Type.IncreasesCombo())
                Combo.Value++;
            else if (result.Type.BreaksCombo())
                Combo.Value = 0;

            applyResult(result.Type, ref currentScoringValues);
            currentScoringValues.MaxCombo = HighestCombo.Value;

            hitEvents.Add(CreateHitEvent(result));
            lastHitObject = result.HitObject;

            updateScore();
        }

        private static void applyResult(HitResult result, ref ScoringValues scoringValues)
        {
            if (!result.IsScorable())
                return;

            if (result.IsBonus())
                scoringValues.BonusScore += result.IsHit() ? Judgement.ToNumericResult(result) : 0;
            else
                scoringValues.BaseScore += result.IsHit() ? Judgement.ToNumericResult(result) : 0;

            if (result.IsBasic())
                scoringValues.CountBasicHitObjects++;
        }

        /// <summary>
        /// Creates the <see cref="HitEvent"/> that describes a <see cref="JudgementResult"/>.
        /// </summary>
        /// <param name="result">The <see cref="JudgementResult"/> to describe.</param>
        /// <returns>The <see cref="HitEvent"/>.</returns>
        protected virtual HitEvent CreateHitEvent(JudgementResult result)
            => new HitEvent(result.TimeOffset, result.Type, result.HitObject, lastHitObject, null);

        protected sealed override void RevertResultInternal(JudgementResult result)
        {
            Combo.Value = result.ComboAtJudgement;
            HighestCombo.Value = result.HighestComboAtJudgement;

            if (result.FailedAtJudgement)
                return;

            scoreResultCounts[result.Type] = scoreResultCounts.GetValueOrDefault(result.Type) - 1;

            // Always update the maximum scoring values.
            revertResult(result.Judgement.MaxResult, ref currentMaximumScoringValues);
            currentMaximumScoringValues.MaxCombo -= result.Judgement.MaxResult.IncreasesCombo() ? 1 : 0;

            if (!result.Type.IsScorable())
                return;

            revertResult(result.Type, ref currentScoringValues);
            currentScoringValues.MaxCombo = HighestCombo.Value;

            Debug.Assert(hitEvents.Count > 0);
            lastHitObject = hitEvents[^1].LastHitObject;
            hitEvents.RemoveAt(hitEvents.Count - 1);

            updateScore();
        }

        private static void revertResult(HitResult result, ref ScoringValues scoringValues)
        {
            if (!result.IsScorable())
                return;

            if (result.IsBonus())
                scoringValues.BonusScore -= result.IsHit() ? Judgement.ToNumericResult(result) : 0;
            else
                scoringValues.BaseScore -= result.IsHit() ? Judgement.ToNumericResult(result) : 0;

            if (result.IsBasic())
                scoringValues.CountBasicHitObjects--;
        }

        private void updateScore()
        {
            Accuracy.Value = currentMaximumScoringValues.BaseScore > 0 ? currentScoringValues.BaseScore / currentMaximumScoringValues.BaseScore : 1;
            TotalScore.Value = ComputeScore(Mode.Value, currentScoringValues, maximumScoringValues);
        }

        /// <summary>
        /// Computes the total score of a given finalised <see cref="ScoreInfo"/>. This should be used when a score is known to be complete.
        /// </summary>
        /// <remarks>
        /// Does not require <see cref="JudgementProcessor.ApplyBeatmap"/> to have been called before use.
        /// </remarks>
        /// <param name="mode">The <see cref="ScoringMode"/> to represent the score as.</param>
        /// <param name="scoreInfo">The <see cref="ScoreInfo"/> to compute the total score of.</param>
        /// <returns>The total score in the given <see cref="ScoringMode"/>.</returns>
        [Pure]
        public double ComputeScore(ScoringMode mode, ScoreInfo scoreInfo)
        {
            if (!ruleset.RulesetInfo.Equals(scoreInfo.Ruleset))
                throw new ArgumentException($"Unexpected score ruleset. Expected \"{ruleset.RulesetInfo.ShortName}\" but was \"{scoreInfo.Ruleset.ShortName}\".");

            ExtractScoringValues(scoreInfo, out var current, out var maximum);

            return ComputeScore(mode, current, maximum);
        }

        /// <summary>
        /// Computes the total score from scoring values.
        /// </summary>
        /// <param name="mode">The <see cref="ScoringMode"/> to represent the score as.</param>
        /// <param name="current">The current scoring values.</param>
        /// <param name="maximum">The maximum scoring values.</param>
        /// <returns>The total score computed from the given scoring values.</returns>
        [Pure]
        public double ComputeScore(ScoringMode mode, ScoringValues current, ScoringValues maximum)
        {
            double accuracyRatio = maximum.BaseScore > 0 ? current.BaseScore / maximum.BaseScore : 1;
            double comboRatio = maximum.MaxCombo > 0 ? (double)current.MaxCombo / maximum.MaxCombo : 1;
            return ComputeScore(mode, accuracyRatio, comboRatio, current.BonusScore, maximum.CountBasicHitObjects);
        }

        /// <summary>
        /// Computes the total score from individual scoring components.
        /// </summary>
        /// <param name="mode">The <see cref="ScoringMode"/> to represent the score as.</param>
        /// <param name="accuracyRatio">The accuracy percentage achieved by the player.</param>
        /// <param name="comboRatio">The portion of the max combo achieved by the player.</param>
        /// <param name="bonusScore">The total bonus score.</param>
        /// <param name="totalBasicHitObjects">The total number of basic (non-tick and non-bonus) hitobjects in the beatmap.</param>
        /// <returns>The total score computed from the given scoring component ratios.</returns>
        [Pure]
        public double ComputeScore(ScoringMode mode, double accuracyRatio, double comboRatio, double bonusScore, int totalBasicHitObjects)
        {
            switch (mode)
            {
                default:
                case ScoringMode.Standardised:
                    double accuracyScore = accuracyPortion * accuracyRatio;
                    double comboScore = comboPortion * comboRatio;
                    return (max_score * (accuracyScore + comboScore) + bonusScore) * scoreMultiplier;

                case ScoringMode.Classic:
                    // This gives a similar feeling to osu!stable scoring (ScoreV1) while keeping classic scoring as only a constant multiple of standardised scoring.
                    // The invariant is important to ensure that scores don't get re-ordered on leaderboards between the two scoring modes.
                    double scaledStandardised = ComputeScore(ScoringMode.Standardised, accuracyRatio, comboRatio, bonusScore, totalBasicHitObjects) / max_score;
                    return Math.Pow(scaledStandardised * Math.Max(1, totalBasicHitObjects), 2) * ClassicScoreMultiplier;
            }
        }

        private ScoreRank rankFrom(double acc)
        {
            if (acc == 1)
                return ScoreRank.X;
            if (acc >= 0.95)
                return ScoreRank.S;
            if (acc >= 0.9)
                return ScoreRank.A;
            if (acc >= 0.8)
                return ScoreRank.B;
            if (acc >= 0.7)
                return ScoreRank.C;

            return ScoreRank.D;
        }

        /// <summary>
        /// Resets this ScoreProcessor to a default state.
        /// </summary>
        /// <param name="storeResults">Whether to store the current state of the <see cref="ScoreProcessor"/> for future use.</param>
        protected override void Reset(bool storeResults)
        {
            base.Reset(storeResults);

            hitEvents.Clear();
            lastHitObject = null;

            if (storeResults)
            {
                maximumScoringValues = currentScoringValues;

                maximumResultCounts.Clear();
                maximumResultCounts.AddRange(scoreResultCounts);
            }

            scoreResultCounts.Clear();

            currentScoringValues = default;
            currentMaximumScoringValues = default;

            TotalScore.Value = 0;
            Accuracy.Value = 1;
            Combo.Value = 0;
            Rank.Disabled = false;
            Rank.Value = ScoreRank.X;
            HighestCombo.Value = 0;
        }

        /// <summary>
        /// Retrieve a score populated with data for the current play this processor is responsible for.
        /// </summary>
        public virtual void PopulateScore(ScoreInfo score)
        {
            score.Combo = Combo.Value;
            score.MaxCombo = HighestCombo.Value;
            score.Accuracy = Accuracy.Value;
            score.Rank = Rank.Value;
            score.HitEvents = hitEvents;

            foreach (var result in HitResultExtensions.ALL_TYPES)
                score.Statistics[result] = scoreResultCounts.GetValueOrDefault(result);

            foreach (var result in HitResultExtensions.ALL_TYPES)
                score.MaximumStatistics[result] = maximumResultCounts.GetValueOrDefault(result);

            // Populate total score after everything else.
            score.TotalScore = (long)Math.Round(ComputeScore(ScoringMode.Standardised, score));
        }

        /// <summary>
        /// Populates a failed score, marking it with the <see cref="ScoreRank.F"/> rank.
        /// </summary>
        public void FailScore(ScoreInfo score)
        {
            if (Rank.Value == ScoreRank.F)
                return;

            score.Passed = false;
            Rank.Value = ScoreRank.F;

            PopulateScore(score);
        }

        public override void ResetFromReplayFrame(ReplayFrame frame)
        {
            base.ResetFromReplayFrame(frame);

            if (frame.Header == null)
                return;

            extractScoringValues(frame.Header.Statistics, out var current, out var maximum);
            currentScoringValues.BaseScore = current.BaseScore;
            currentScoringValues.MaxCombo = frame.Header.MaxCombo;
            currentMaximumScoringValues.BaseScore = maximum.BaseScore;
            currentMaximumScoringValues.MaxCombo = maximum.MaxCombo;

            Combo.Value = frame.Header.Combo;
            HighestCombo.Value = frame.Header.MaxCombo;

            scoreResultCounts.Clear();
            scoreResultCounts.AddRange(frame.Header.Statistics);

            updateScore();

            OnResetFromReplayFrame?.Invoke();
        }

        #region ScoringValue extraction

        /// <summary>
        /// Applies a best-effort extraction of hit statistics into <see cref="ScoringValues"/>.
        /// </summary>
        /// <remarks>
        /// This method is useful in a variety of situations, with a few drawbacks that need to be considered:
        /// <list type="bullet">
        ///     <item>The maximum <see cref="ScoringValues.BonusScore"/> will always be 0.</item>
        ///     <item>The current and maximum <see cref="ScoringValues.CountBasicHitObjects"/> will always be the same value.</item>
        /// </list>
        /// Consumers are expected to more accurately fill in the above values through external means.
        /// <para>
        /// <b>Ensure</b> to fill in the maximum <see cref="ScoringValues.CountBasicHitObjects"/> for use in
        /// <see cref="ComputeScore(osu.Game.Rulesets.Scoring.ScoringMode,osu.Game.Scoring.ScoringValues,osu.Game.Scoring.ScoringValues)"/>.
        /// </para>
        /// </remarks>
        /// <param name="scoreInfo">The score to extract scoring values from.</param>
        /// <param name="current">The "current" scoring values, representing the hit statistics as they appear.</param>
        /// <param name="maximum">The "maximum" scoring values, representing the hit statistics as if the maximum hit result was attained each time.</param>
        [Pure]
        internal void ExtractScoringValues(ScoreInfo scoreInfo, out ScoringValues current, out ScoringValues maximum)
        {
            extractScoringValues(scoreInfo.Statistics, out current, out maximum);
            current.MaxCombo = scoreInfo.MaxCombo;

            if (scoreInfo.MaximumStatistics.Count > 0)
                extractScoringValues(scoreInfo.MaximumStatistics, out _, out maximum);
        }

        /// <summary>
        /// Applies a best-effort extraction of hit statistics into <see cref="ScoringValues"/>.
        /// </summary>
        /// <remarks>
        /// This method is useful in a variety of situations, with a few drawbacks that need to be considered:
        /// <list type="bullet">
        ///     <item>The maximum <see cref="ScoringValues.BonusScore"/> will always be 0.</item>
        ///     <item>The current and maximum <see cref="ScoringValues.CountBasicHitObjects"/> will always be the same value.</item>
        /// </list>
        /// Consumers are expected to more accurately fill in the above values through external means.
        /// <para>
        /// <b>Ensure</b> to fill in the maximum <see cref="ScoringValues.CountBasicHitObjects"/> for use in
        /// <see cref="ComputeScore(osu.Game.Rulesets.Scoring.ScoringMode,osu.Game.Scoring.ScoringValues,osu.Game.Scoring.ScoringValues)"/>.
        /// </para>
        /// </remarks>
        /// <param name="header">The replay frame header to extract scoring values from.</param>
        /// <param name="current">The "current" scoring values, representing the hit statistics as they appear.</param>
        /// <param name="maximum">The "maximum" scoring values, representing the hit statistics as if the maximum hit result was attained each time.</param>
        [Pure]
        internal void ExtractScoringValues(FrameHeader header, out ScoringValues current, out ScoringValues maximum)
        {
            extractScoringValues(header.Statistics, out current, out maximum);
            current.MaxCombo = header.MaxCombo;
        }

        /// <summary>
        /// Applies a best-effort extraction of hit statistics into <see cref="ScoringValues"/>.
        /// </summary>
        /// <remarks>
        /// This method is useful in a variety of situations, with a few drawbacks that need to be considered:
        /// <list type="bullet">
        ///     <item>The current <see cref="ScoringValues.MaxCombo"/> will always be 0.</item>
        ///     <item>The maximum <see cref="ScoringValues.BonusScore"/> will always be 0.</item>
        ///     <item>The current and maximum <see cref="ScoringValues.CountBasicHitObjects"/> will always be the same value.</item>
        /// </list>
        /// Consumers are expected to more accurately fill in the above values (especially the current <see cref="ScoringValues.MaxCombo"/>) via external means (e.g. <see cref="ScoreInfo"/>).
        /// </remarks>
        /// <param name="statistics">The hit statistics to extract scoring values from.</param>
        /// <param name="current">The "current" scoring values, representing the hit statistics as they appear.</param>
        /// <param name="maximum">The "maximum" scoring values, representing the hit statistics as if the maximum hit result was attained each time.</param>
        [Pure]
        private void extractScoringValues(IReadOnlyDictionary<HitResult, int> statistics, out ScoringValues current, out ScoringValues maximum)
        {
            current = default;
            maximum = default;

            foreach ((HitResult result, int count) in statistics)
            {
                if (!result.IsScorable())
                    continue;

                if (result.IsBonus())
                    current.BonusScore += count * Judgement.ToNumericResult(result);

                if (result.AffectsAccuracy())
                {
                    // The maximum result of this judgement if it wasn't a miss.
                    // E.g. For a GOOD judgement, the max result is either GREAT/PERFECT depending on which one the ruleset uses (osu!: GREAT, osu!mania: PERFECT).
                    HitResult maxResult;

                    switch (result)
                    {
                        case HitResult.LargeTickHit:
                        case HitResult.LargeTickMiss:
                            maxResult = HitResult.LargeTickHit;
                            break;

                        case HitResult.SmallTickHit:
                        case HitResult.SmallTickMiss:
                            maxResult = HitResult.SmallTickHit;
                            break;

                        default:
                            maxResult = maxBasicResult ??= ruleset.GetHitResults().OrderByDescending(kvp => Judgement.ToNumericResult(kvp.result)).First().result;
                            break;
                    }

                    current.BaseScore += count * Judgement.ToNumericResult(result);
                    maximum.BaseScore += count * Judgement.ToNumericResult(maxResult);
                }

                if (result.AffectsCombo())
                    maximum.MaxCombo += count;

                if (result.IsBasic())
                {
                    current.CountBasicHitObjects += count;
                    maximum.CountBasicHitObjects += count;
                }
            }
        }

        #endregion

        protected override void Dispose(bool isDisposing)
        {
            base.Dispose(isDisposing);
            hitEvents.Clear();
        }
    }

    public enum ScoringMode
    {
        [LocalisableDescription(typeof(GameplaySettingsStrings), nameof(GameplaySettingsStrings.StandardisedScoreDisplay))]
        Standardised,

        [LocalisableDescription(typeof(GameplaySettingsStrings), nameof(GameplaySettingsStrings.ClassicScoreDisplay))]
        Classic
    }
}