// 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;
using System.Linq;
using OpenTK;
using osu.Game.Audio;
using osu.Game.Beatmaps;
using osu.Game.Beatmaps.Timing;
using osu.Game.Rulesets.Mania.MathUtils;
using osu.Game.Rulesets.Mania.Objects;
using osu.Game.Rulesets.Objects;
using osu.Game.Rulesets.Objects.Types;

namespace osu.Game.Rulesets.Mania.Beatmaps.Patterns.Legacy
{
    internal class HitObjectPatternGenerator : PatternGenerator
    {
        public PatternType StairType { get; private set; }

        private readonly PatternType convertType;

        public HitObjectPatternGenerator(FastRandom random, HitObject hitObject, Beatmap beatmap, Pattern previousPattern, double previousTime, Vector2 previousPosition, double density, PatternType lastStair)
            : base(random, hitObject, beatmap, previousPattern)
        {
            StairType = lastStair;

            ControlPoint overridePoint;
            ControlPoint controlPoint = beatmap.TimingInfo.TimingPointAt(hitObject.StartTime, out overridePoint);

            var positionData = hitObject as IHasPosition;

            float positionSeparation = ((positionData?.Position ?? Vector2.Zero) - previousPosition).Length;
            double timeSeparation = hitObject.StartTime - previousTime;

            double beatLength = controlPoint.BeatLength;
            bool kiai = (overridePoint ?? controlPoint).KiaiMode;

            if (timeSeparation <= 125)
            {
                // More than 120 BPM
                convertType |= PatternType.ForceNotStack;
            }

            if (timeSeparation <= 80)
            {
                // More than 187 BPM
                convertType |= PatternType.ForceNotStack | PatternType.KeepSingle;
            }
            else if (timeSeparation <= 95)
            {
                // More than 157 BPM
                convertType |= PatternType.ForceNotStack | PatternType.KeepSingle | lastStair;
            }
            else if (timeSeparation <= 105)
            {
                // More than 140 BPM
                convertType |= PatternType.ForceNotStack | PatternType.LowProbability;
            }
            else if (timeSeparation <= 125)
            {
                // More than 120 BPM
                convertType |= PatternType.ForceNotStack;
            }
            else if (timeSeparation <= 135 && positionSeparation < 20)
            {
                // More than 111 BPM stream
                convertType |= PatternType.Cycle | PatternType.KeepSingle;
            }
            else if (timeSeparation <= 150 & positionSeparation < 20)
            {
                // More than 100 BPM stream
                convertType |= PatternType.ForceStack | PatternType.LowProbability;
            }
            else if (positionSeparation < 20 && density >= beatLength / 2.5)
            {
                // Low density stream
                convertType |= PatternType.Reverse | PatternType.LowProbability;
            }
            else if (density < beatLength / 2.5 || kiai)
            {
                // High density
            }
            else
                convertType |= PatternType.LowProbability;
        }

        public override Pattern Generate()
        {
            int lastColumn = PreviousPattern.HitObjects.First().Column;

            if ((convertType & PatternType.Reverse) > 0 && PreviousPattern.HitObjects.Any())
            {
                // Generate a new pattern by copying the last hit objects in reverse-column order
                var pattern = new Pattern();

                for (int i = RandomStart; i < AvailableColumns; i++)
                    if (PreviousPattern.ColumnHasObject(i))
                        addToPattern(pattern, RandomStart + AvailableColumns - i - 1);

                return pattern;
            }

            if ((convertType & PatternType.Cycle) > 0 && PreviousPattern.HitObjects.Count() == 1
                // If we convert to 7K + 1, let's not overload the special key
                && (AvailableColumns != 8 || lastColumn != 0)
                // Make sure the last column was not the centre column
                && (AvailableColumns % 2 == 0 || lastColumn != AvailableColumns / 2))
            {
                // Generate a new pattern by cycling backwards (similar to Reverse but for only one hit object)
                var pattern = new Pattern();

                int column = RandomStart + AvailableColumns - lastColumn - 1;
                addToPattern(pattern, column);

                return pattern;
            }

            if ((convertType & PatternType.ForceStack) > 0 && PreviousPattern.HitObjects.Any())
            {
                // Generate a new pattern by placing on the already filled columns
                var pattern = new Pattern();

                for (int i = RandomStart; i < AvailableColumns; i++)
                    if (PreviousPattern.ColumnHasObject(i))
                        addToPattern(pattern, i);

                return pattern;
            }

            if ((convertType & PatternType.Stair) > 0 && PreviousPattern.HitObjects.Count() == 1)
            {
                // Generate a new pattern by placing on the next column, cycling back to the start if there is no "next"
                var pattern = new Pattern();

                int targetColumn = lastColumn + 1;
                if (targetColumn == AvailableColumns)
                {
                    targetColumn = RandomStart;
                    StairType = PatternType.ReverseStair;
                }

                addToPattern(pattern, targetColumn);
                return pattern;
            }

            if ((convertType & PatternType.ReverseStair) > 0 && PreviousPattern.HitObjects.Count() == 1)
            {
                // Generate a new pattern by placing on the previous column, cycling back to the end if there is no "previous"
                var pattern = new Pattern();

                int targetColumn = lastColumn - 1;
                if (targetColumn == RandomStart - 1)
                {
                    targetColumn = AvailableColumns - 1;
                    StairType = PatternType.Stair;
                }

                addToPattern(pattern, targetColumn);
                return pattern;
            }

            if ((convertType & PatternType.KeepSingle) > 0)
                return generateRandomNotes(1);

            if ((convertType & PatternType.Mirror) > 0)
            {
                if (ConversionDifficulty > 6.5)
                    return generateRandomPatternWithMirrored(0.12, 0.38, 0.12);
                if (ConversionDifficulty > 4)
                    return generateRandomPatternWithMirrored(0.12, 0.17, 0);
                return generateRandomPatternWithMirrored(0.12, 0, 0);
            }

            if (ConversionDifficulty > 6.5)
            {
                if ((convertType & PatternType.LowProbability) > 0)
                    return generateRandomPattern(0.78, 0.42, 0, 0);
                return generateRandomPattern(1, 0.62, 0, 0);
            }

            if (ConversionDifficulty > 4)
            {
                if ((convertType & PatternType.LowProbability) > 0)
                    return generateRandomPattern(0.35, 0.08, 0, 0);
                return generateRandomPattern(0.52, 0.15, 0, 0);
            }

            if (ConversionDifficulty > 2)
            {
                if ((convertType & PatternType.LowProbability) > 0)
                    return generateRandomPattern(0.18, 0, 0, 0);
                return generateRandomPattern(0.45, 0, 0, 0);
            }

            return generateRandomPattern(0, 0, 0, 0);
        }

        /// <summary>
        /// Generates random notes.
        /// <para>
        /// This will generate as many as it can up to <paramref name="noteCount"/>, accounting for
        /// any stacks if <see cref="convertType"/> is forcing no stacks.
        /// </para>
        /// </summary>
        /// <param name="noteCount">The amount of notes to generate.</param>
        /// <returns>The <see cref="Pattern"/> containing the hit objects.</returns>
        private Pattern generateRandomNotes(int noteCount)
        {
            var pattern = new Pattern();

            bool allowStacking = (convertType & PatternType.ForceNotStack) == 0;

            if (!allowStacking)
                noteCount = Math.Min(noteCount, AvailableColumns - RandomStart - PreviousPattern.ColumnWithObjects);

            int nextColumn = GetColumn((HitObject as IHasXPosition)?.X ?? 0, true);
            for (int i = 0; i < noteCount; i++)
            {
                while (pattern.ColumnHasObject(nextColumn) || PreviousPattern.ColumnHasObject(nextColumn) && !allowStacking)
                {
                    if ((convertType & PatternType.Gathered) > 0)
                    {
                        nextColumn++;
                        if (nextColumn == AvailableColumns)
                            nextColumn = RandomStart;
                    }
                    else
                        nextColumn = Random.Next(RandomStart, AvailableColumns);
                }

                addToPattern(pattern, nextColumn);
            }

            return pattern;
        }

        /// <summary>
        /// Whether this hit object can generate a note in the special column.
        /// </summary>
        private bool hasSpecialColumn => HitObject.Samples.Any(s => s.Name == SampleInfo.HIT_CLAP) && HitObject.Samples.Any(s => s.Name == SampleInfo.HIT_FINISH);

        /// <summary>
        /// Generates a random pattern.
        /// </summary>
        /// <param name="p2">Probability for 2 notes to be generated.</param>
        /// <param name="p3">Probability for 3 notes to be generated.</param>
        /// <param name="p4">Probability for 4 notes to be generated.</param>
        /// <param name="p5">Probability for 5 notes to be generated.</param>
        /// <returns>The <see cref="Pattern"/> containing the hit objects.</returns>
        private Pattern generateRandomPattern(double p2, double p3, double p4, double p5)
        {
            var pattern = new Pattern();

            pattern.Add(generateRandomNotes(getRandomNoteCount(p2, p3, p4, p5)));

            if (RandomStart > 0 && hasSpecialColumn)
                addToPattern(pattern, 0);

            return pattern;
        }

        /// <summary>
        /// Generates a random pattern which has both normal and mirrored notes.
        /// </summary>
        /// <param name="centreProbability">The probability for a note to be added to the centre column.</param>
        /// <param name="p2">Probability for 2 notes to be generated.</param>
        /// <param name="p3">Probability for 3 notes to be generated.</param>
        /// <returns>The <see cref="Pattern"/> containing the hit objects.</returns>
        private Pattern generateRandomPatternWithMirrored(double centreProbability, double p2, double p3)
        {
            var pattern = new Pattern();

            bool addToCentre;
            int noteCount = getRandomNoteCountMirrored(centreProbability, p2, p3, out addToCentre);

            int columnLimit = (AvailableColumns % 2 == 0 ? AvailableColumns : AvailableColumns - 1) / 2;
            int nextColumn = Random.Next(RandomStart, columnLimit);
            for (int i = 0; i < noteCount; i++)
            {
                while (pattern.ColumnHasObject(nextColumn))
                    nextColumn = Random.Next(RandomStart, columnLimit);

                // Add normal note
                addToPattern(pattern, nextColumn);
                // Add mirrored note
                addToPattern(pattern, RandomStart + AvailableColumns - nextColumn - 1);
            }

            if (addToCentre)
                addToPattern(pattern, AvailableColumns / 2);

            if (RandomStart > 0 && hasSpecialColumn)
                addToPattern(pattern, 0);

            return pattern;
        }

        /// <summary>
        /// Generates a count of notes to be generated from a list of probabilities.
        /// </summary>
        /// <param name="p2">Probability for 2 notes to be generated.</param>
        /// <param name="p3">Probability for 3 notes to be generated.</param>
        /// <param name="p4">Probability for 4 notes to be generated.</param>
        /// <param name="p5">Probability for 5 notes to be generated.</param>
        /// <returns>The amount of notes to be generated.</returns>
        private int getRandomNoteCount(double p2, double p3, double p4, double p5)
        {
            switch (AvailableColumns)
            {
                case 2:
                    p2 = 0;
                    p3 = 0;
                    p4 = 0;
                    p5 = 0;
                    break;
                case 3:
                    p2 = Math.Max(p2, 0.1);
                    p3 = 0;
                    p4 = 0;
                    p5 = 0;
                    break;
                case 4:
                    p2 = Math.Max(p2, 0.23);
                    p3 = Math.Max(p3, 0.04);
                    p4 = 0;
                    p5 = 0;
                    break;
                case 5:
                    p3 = Math.Max(p3, 0.15);
                    p4 = Math.Max(p4, 0.03);
                    p5 = 0;
                    break;
            }

            if (HitObject.Samples.Any(s => s.Name == SampleInfo.HIT_CLAP))
                p2 = 1;

            return GetRandomNoteCount(p2, p3, p4, p5);
        }

        /// <summary>
        /// Generates a count of notes to be generated from a list of probabilities.
        /// </summary>
        /// <param name="centreProbability">The probability for a note to be added to the centre column.</param>
        /// <param name="p2">Probability for 2 notes to be generated.</param>
        /// <param name="p3">Probability for 3 notes to be generated.</param>
        /// <param name="addToCentre">Whether to add a note to the centre column.</param>
        /// <returns>The amount of notes to be generated. The note to be added to the centre column will NOT be part of this count.</returns>
        private int getRandomNoteCountMirrored(double centreProbability, double p2, double p3, out bool addToCentre)
        {
            addToCentre = false;

            if ((convertType & PatternType.ForceNotStack) > 0)
                return getRandomNoteCount(p2 / 2, p2, (p2 + p3) / 2, p3);

            switch (AvailableColumns)
            {
                case 2:
                    centreProbability = 0;
                    p2 = 0;
                    p3 = 0;
                    break;
                case 3:
                    centreProbability = Math.Max(centreProbability, 0.03);
                    p2 = Math.Max(p2, 0.1);
                    p3 = 0;
                    break;
                case 4:
                    centreProbability = 0;
                    p2 = Math.Max(p2 * 2, 0.2);
                    p3 = 0;
                    break;
                case 5:
                    centreProbability = Math.Max(centreProbability, 0.03);
                    p3 = 0;
                    break;
                case 6:
                    centreProbability = 0;
                    p2 = Math.Max(p2 * 2, 0.5);
                    p3 = Math.Max(p3 * 2, 0.15);
                    break;
            }

            double centreVal = Random.NextDouble();
            int noteCount = GetRandomNoteCount(p2, p3);

            addToCentre = AvailableColumns % 2 != 0 && noteCount != 3 && centreVal > 1 - centreProbability;
            return noteCount;
        }

        /// <summary>
        /// Constructs and adds a note to a pattern.
        /// </summary>
        /// <param name="pattern">The pattern to add to.</param>
        /// <param name="column">The column to add the note to.</param>
        private void addToPattern(Pattern pattern, int column)
        {
            pattern.Add(new Note
            {
                StartTime = HitObject.StartTime,
                Samples = HitObject.Samples,
                Column = column
            });
        }
    }
}