// 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.

#nullable disable

using osuTK;
using osu.Game.Rulesets.Objects.Types;
using System;
using System.Collections.Generic;
using System.IO;
using osu.Game.Beatmaps.Formats;
using osu.Game.Audio;
using System.Linq;
using JetBrains.Annotations;
using osu.Framework.Utils;
using osu.Game.Beatmaps.ControlPoints;
using osu.Game.Beatmaps.Legacy;
using osu.Game.Skinning;
using osu.Game.Utils;
using System.Buffers;

namespace osu.Game.Rulesets.Objects.Legacy
{
    /// <summary>
    /// A HitObjectParser to parse legacy Beatmaps.
    /// </summary>
    public abstract class ConvertHitObjectParser : HitObjectParser
    {
        /// <summary>
        /// The offset to apply to all time values.
        /// </summary>
        protected readonly double Offset;

        /// <summary>
        /// The .osu format (beatmap) version.
        /// </summary>
        protected readonly int FormatVersion;

        protected bool FirstObject { get; private set; } = true;

        protected ConvertHitObjectParser(double offset, int formatVersion)
        {
            Offset = offset;
            FormatVersion = formatVersion;
        }

        public override HitObject Parse(string text)
        {
            string[] split = text.Split(',');

            Vector2 pos =
                FormatVersion >= LegacyBeatmapEncoder.FIRST_LAZER_VERSION
                    ? new Vector2(Parsing.ParseFloat(split[0], Parsing.MAX_COORDINATE_VALUE), Parsing.ParseFloat(split[1], Parsing.MAX_COORDINATE_VALUE))
                    : new Vector2((int)Parsing.ParseFloat(split[0], Parsing.MAX_COORDINATE_VALUE), (int)Parsing.ParseFloat(split[1], Parsing.MAX_COORDINATE_VALUE));

            double startTime = Parsing.ParseDouble(split[2]) + Offset;

            LegacyHitObjectType type = (LegacyHitObjectType)Parsing.ParseInt(split[3]);

            int comboOffset = (int)(type & LegacyHitObjectType.ComboOffset) >> 4;
            type &= ~LegacyHitObjectType.ComboOffset;

            bool combo = type.HasFlag(LegacyHitObjectType.NewCombo);
            type &= ~LegacyHitObjectType.NewCombo;

            var soundType = (LegacyHitSoundType)Parsing.ParseInt(split[4]);
            var bankInfo = new SampleBankInfo();

            HitObject result = null;

            if (type.HasFlag(LegacyHitObjectType.Circle))
            {
                result = CreateHit(pos, combo, comboOffset);

                if (split.Length > 5)
                    readCustomSampleBanks(split[5], bankInfo);
            }
            else if (type.HasFlag(LegacyHitObjectType.Slider))
            {
                double? length = null;

                int repeatCount = Parsing.ParseInt(split[6]);

                if (repeatCount > 9000)
                    throw new FormatException(@"Repeat count is way too high");

                // osu-stable treated the first span of the slider as a repeat, but no repeats are happening
                repeatCount = Math.Max(0, repeatCount - 1);

                if (split.Length > 7)
                {
                    length = Math.Max(0, Parsing.ParseDouble(split[7], Parsing.MAX_COORDINATE_VALUE));
                    if (length == 0)
                        length = null;
                }

                if (split.Length > 10)
                    readCustomSampleBanks(split[10], bankInfo, true);

                // One node for each repeat + the start and end nodes
                int nodes = repeatCount + 2;

                // Populate node sample bank infos with the default hit object sample bank
                var nodeBankInfos = new List<SampleBankInfo>();
                for (int i = 0; i < nodes; i++)
                    nodeBankInfos.Add(bankInfo.Clone());

                // Read any per-node sample banks
                if (split.Length > 9 && split[9].Length > 0)
                {
                    string[] sets = split[9].Split('|');

                    for (int i = 0; i < nodes; i++)
                    {
                        if (i >= sets.Length)
                            break;

                        SampleBankInfo info = nodeBankInfos[i];
                        readCustomSampleBanks(sets[i], info);
                    }
                }

                // Populate node sound types with the default hit object sound type
                var nodeSoundTypes = new List<LegacyHitSoundType>();
                for (int i = 0; i < nodes; i++)
                    nodeSoundTypes.Add(soundType);

                // Read any per-node sound types
                if (split.Length > 8 && split[8].Length > 0)
                {
                    string[] adds = split[8].Split('|');

                    for (int i = 0; i < nodes; i++)
                    {
                        if (i >= adds.Length)
                            break;

                        int.TryParse(adds[i], out int sound);
                        nodeSoundTypes[i] = (LegacyHitSoundType)sound;
                    }
                }

                // Generate the final per-node samples
                var nodeSamples = new List<IList<HitSampleInfo>>(nodes);
                for (int i = 0; i < nodes; i++)
                    nodeSamples.Add(convertSoundType(nodeSoundTypes[i], nodeBankInfos[i]));

                result = CreateSlider(pos, combo, comboOffset, convertPathString(split[5], pos), length, repeatCount, nodeSamples);
            }
            else if (type.HasFlag(LegacyHitObjectType.Spinner))
            {
                double duration = Math.Max(0, Parsing.ParseDouble(split[5]) + Offset - startTime);

                result = CreateSpinner(new Vector2(512, 384) / 2, combo, comboOffset, duration);

                if (split.Length > 6)
                    readCustomSampleBanks(split[6], bankInfo);
            }
            else if (type.HasFlag(LegacyHitObjectType.Hold))
            {
                // Note: Hold is generated by BMS converts

                double endTime = Math.Max(startTime, Parsing.ParseDouble(split[2]));

                if (split.Length > 5 && !string.IsNullOrEmpty(split[5]))
                {
                    string[] ss = split[5].Split(':');
                    endTime = Math.Max(startTime, Parsing.ParseDouble(ss[0]));
                    readCustomSampleBanks(string.Join(':', ss.Skip(1)), bankInfo);
                }

                result = CreateHold(pos, combo, comboOffset, endTime + Offset - startTime);
            }

            if (result == null)
                throw new InvalidDataException($"Unknown hit object type: {split[3]}");

            result.StartTime = startTime;

            if (result.Samples.Count == 0)
                result.Samples = convertSoundType(soundType, bankInfo);

            FirstObject = false;

            return result;
        }

        private void readCustomSampleBanks(string str, SampleBankInfo bankInfo, bool banksOnly = false)
        {
            if (string.IsNullOrEmpty(str))
                return;

            string[] split = str.Split(':');

            var bank = (LegacySampleBank)Parsing.ParseInt(split[0]);
            if (!Enum.IsDefined(bank))
                bank = LegacySampleBank.Normal;

            var addBank = (LegacySampleBank)Parsing.ParseInt(split[1]);
            if (!Enum.IsDefined(addBank))
                addBank = LegacySampleBank.Normal;

            string stringBank = bank.ToString().ToLowerInvariant();
            if (stringBank == @"none")
                stringBank = null;
            string stringAddBank = addBank.ToString().ToLowerInvariant();
            if (stringAddBank == @"none")
                stringAddBank = null;

            bankInfo.BankForNormal = stringBank;
            bankInfo.BankForAdditions = string.IsNullOrEmpty(stringAddBank) ? stringBank : stringAddBank;

            if (banksOnly) return;

            if (split.Length > 2)
                bankInfo.CustomSampleBank = Parsing.ParseInt(split[2]);

            if (split.Length > 3)
                bankInfo.Volume = Math.Max(0, Parsing.ParseInt(split[3]));

            bankInfo.Filename = split.Length > 4 ? split[4] : null;
        }

        private PathType convertPathType(string input)
        {
            switch (input[0])
            {
                default:
                case 'C':
                    return PathType.CATMULL;

                case 'B':
                    if (input.Length > 1 && int.TryParse(input.Substring(1), out int degree) && degree > 0)
                        return PathType.BSpline(degree);

                    return PathType.BEZIER;

                case 'L':
                    return PathType.LINEAR;

                case 'P':
                    return PathType.PERFECT_CURVE;
            }
        }

        /// <summary>
        /// Converts a given point string into a set of path control points.
        /// </summary>
        /// <remarks>
        /// A point string takes the form: X|1:1|2:2|2:2|3:3|Y|1:1|2:2.
        /// This has three segments:
        /// <list type="number">
        ///     <item>
        ///         <description>X: { (1,1), (2,2) } (implicit segment)</description>
        ///     </item>
        ///     <item>
        ///         <description>X: { (2,2), (3,3) } (implicit segment)</description>
        ///     </item>
        ///     <item>
        ///         <description>Y: { (3,3), (1,1), (2, 2) } (explicit segment)</description>
        ///     </item>
        /// </list>
        /// </remarks>
        /// <param name="pointString">The point string.</param>
        /// <param name="offset">The positional offset to apply to the control points.</param>
        /// <returns>All control points in the resultant path.</returns>
        private PathControlPoint[] convertPathString(string pointString, Vector2 offset)
        {
            // This code takes on the responsibility of handling explicit segments of the path ("X" & "Y" from above). Implicit segments are handled by calls to convertPoints().
            string[] pointStringSplit = pointString.Split('|');

            var pointsBuffer = ArrayPool<Vector2>.Shared.Rent(pointStringSplit.Length);
            var segmentsBuffer = ArrayPool<(PathType Type, int StartIndex)>.Shared.Rent(pointStringSplit.Length);
            int currentPointsIndex = 0;
            int currentSegmentsIndex = 0;

            try
            {
                foreach (string s in pointStringSplit)
                {
                    if (char.IsLetter(s[0]))
                    {
                        // The start of a new segment(indicated by having an alpha character at position 0).
                        var pathType = convertPathType(s);
                        segmentsBuffer[currentSegmentsIndex++] = (pathType, currentPointsIndex);

                        // First segment is prepended by an extra zero point
                        if (currentPointsIndex == 0)
                            pointsBuffer[currentPointsIndex++] = Vector2.Zero;
                    }
                    else
                    {
                        pointsBuffer[currentPointsIndex++] = readPoint(s, offset);
                    }
                }

                int pointsCount = currentPointsIndex;
                int segmentsCount = currentSegmentsIndex;
                var controlPoints = new List<ArraySegment<PathControlPoint>>(pointsCount);
                var allPoints = new ArraySegment<Vector2>(pointsBuffer, 0, pointsCount);

                for (int i = 0; i < segmentsCount; i++)
                {
                    if (i < segmentsCount - 1)
                    {
                        int startIndex = segmentsBuffer[i].StartIndex;
                        int endIndex = segmentsBuffer[i + 1].StartIndex;
                        controlPoints.AddRange(convertPoints(segmentsBuffer[i].Type, allPoints.Slice(startIndex, endIndex - startIndex), pointsBuffer[endIndex]));
                    }
                    else
                    {
                        int startIndex = segmentsBuffer[i].StartIndex;
                        controlPoints.AddRange(convertPoints(segmentsBuffer[i].Type, allPoints.Slice(startIndex), null));
                    }
                }

                return mergeControlPointsLists(controlPoints);
            }
            finally
            {
                ArrayPool<Vector2>.Shared.Return(pointsBuffer);
                ArrayPool<(PathType, int)>.Shared.Return(segmentsBuffer);
            }

            static Vector2 readPoint(string value, Vector2 startPos)
            {
                string[] vertexSplit = value.Split(':');

                Vector2 pos = new Vector2((int)Parsing.ParseDouble(vertexSplit[0], Parsing.MAX_COORDINATE_VALUE), (int)Parsing.ParseDouble(vertexSplit[1], Parsing.MAX_COORDINATE_VALUE)) - startPos;
                return pos;
            }
        }

        /// <summary>
        /// Converts a given point list into a set of path segments.
        /// </summary>
        /// <param name="type">The path type of the point list.</param>
        /// <param name="points">The point list.</param>
        /// <param name="endPoint">Any extra endpoint to consider as part of the points. This will NOT be returned.</param>
        /// <returns>The set of points contained by <paramref name="points"/> as one or more segments of the path.</returns>
        private IEnumerable<ArraySegment<PathControlPoint>> convertPoints(PathType type, ArraySegment<Vector2> points, Vector2? endPoint)
        {
            var vertices = new PathControlPoint[points.Count];

            // Parse into control points.
            for (int i = 0; i < points.Count; i++)
                vertices[i] = new PathControlPoint { Position = points[i] };

            // Edge-case rules (to match stable).
            if (type == PathType.PERFECT_CURVE)
            {
                int endPointLength = endPoint == null ? 0 : 1;

                if (vertices.Length + endPointLength != 3)
                    type = PathType.BEZIER;
                else if (isLinear(points[0], points[1], endPoint ?? points[2]))
                {
                    // osu-stable special-cased colinear perfect curves to a linear path
                    type = PathType.LINEAR;
                }
            }

            // The first control point must have a definite type.
            vertices[0].Type = type;

            // A path can have multiple implicit segments of the same type if there are two sequential control points with the same position.
            // To handle such cases, this code may return multiple path segments with the final control point in each segment having a non-null type.
            // For the point string X|1:1|2:2|2:2|3:3, this code returns the segments:
            // X: { (1,1), (2, 2) }
            // X: { (3, 3) }
            // Note: (2, 2) is not returned in the second segments, as it is implicit in the path.
            int startIndex = 0;
            int endIndex = 0;

            while (++endIndex < vertices.Length)
            {
                // Keep incrementing while an implicit segment doesn't need to be started.
                if (vertices[endIndex].Position != vertices[endIndex - 1].Position)
                    continue;

                // Legacy CATMULL sliders don't support multiple segments, so adjacent CATMULL segments should be treated as a single one.
                // Importantly, this is not applied to the first control point, which may duplicate the slider path's position
                // resulting in a duplicate (0,0) control point in the resultant list.
                if (type == PathType.CATMULL && endIndex > 1 && FormatVersion < LegacyBeatmapEncoder.FIRST_LAZER_VERSION)
                    continue;

                // The last control point of each segment is not allowed to start a new implicit segment.
                if (endIndex == vertices.Length - 1)
                    continue;

                // Force a type on the last point, and return the current control point set as a segment.
                vertices[endIndex - 1].Type = type;
                yield return new ArraySegment<PathControlPoint>(vertices, startIndex, endIndex - startIndex);

                // Skip the current control point - as it's the same as the one that's just been returned.
                startIndex = endIndex + 1;
            }

            if (startIndex < endIndex)
                yield return new ArraySegment<PathControlPoint>(vertices, startIndex, endIndex - startIndex);

            static bool isLinear(Vector2 p0, Vector2 p1, Vector2 p2)
                => Precision.AlmostEquals(0, (p1.Y - p0.Y) * (p2.X - p0.X)
                                             - (p1.X - p0.X) * (p2.Y - p0.Y));
        }

        private PathControlPoint[] mergeControlPointsLists(List<ArraySegment<PathControlPoint>> controlPointList)
        {
            int totalCount = 0;

            foreach (var arr in controlPointList)
                totalCount += arr.Count;

            var mergedArray = new PathControlPoint[totalCount];
            int copyIndex = 0;

            foreach (var arr in controlPointList)
            {
                arr.AsSpan().CopyTo(mergedArray.AsSpan(copyIndex));
                copyIndex += arr.Count;
            }

            return mergedArray;
        }

        /// <summary>
        /// Creates a legacy Hit-type hit object.
        /// </summary>
        /// <param name="position">The position of the hit object.</param>
        /// <param name="newCombo">Whether the hit object creates a new combo.</param>
        /// <param name="comboOffset">When starting a new combo, the offset of the new combo relative to the current one.</param>
        /// <returns>The hit object.</returns>
        protected abstract HitObject CreateHit(Vector2 position, bool newCombo, int comboOffset);

        /// <summary>
        /// Creats a legacy Slider-type hit object.
        /// </summary>
        /// <param name="position">The position of the hit object.</param>
        /// <param name="newCombo">Whether the hit object creates a new combo.</param>
        /// <param name="comboOffset">When starting a new combo, the offset of the new combo relative to the current one.</param>
        /// <param name="controlPoints">The slider control points.</param>
        /// <param name="length">The slider length.</param>
        /// <param name="repeatCount">The slider repeat count.</param>
        /// <param name="nodeSamples">The samples to be played when the slider nodes are hit. This includes the head and tail of the slider.</param>
        /// <returns>The hit object.</returns>
        protected abstract HitObject CreateSlider(Vector2 position, bool newCombo, int comboOffset, PathControlPoint[] controlPoints, double? length, int repeatCount,
                                                  IList<IList<HitSampleInfo>> nodeSamples);

        /// <summary>
        /// Creates a legacy Spinner-type hit object.
        /// </summary>
        /// <param name="position">The position of the hit object.</param>
        /// <param name="newCombo">Whether the hit object creates a new combo.</param>
        /// <param name="comboOffset">When starting a new combo, the offset of the new combo relative to the current one.</param>
        /// <param name="duration">The spinner duration.</param>
        /// <returns>The hit object.</returns>
        protected abstract HitObject CreateSpinner(Vector2 position, bool newCombo, int comboOffset, double duration);

        /// <summary>
        /// Creates a legacy Hold-type hit object.
        /// </summary>
        /// <param name="position">The position of the hit object.</param>
        /// <param name="newCombo">Whether the hit object creates a new combo.</param>
        /// <param name="comboOffset">When starting a new combo, the offset of the new combo relative to the current one.</param>
        /// <param name="duration">The hold duration.</param>
        protected abstract HitObject CreateHold(Vector2 position, bool newCombo, int comboOffset, double duration);

        private List<HitSampleInfo> convertSoundType(LegacyHitSoundType type, SampleBankInfo bankInfo)
        {
            var soundTypes = new List<HitSampleInfo>();

            if (string.IsNullOrEmpty(bankInfo.Filename))
            {
                soundTypes.Add(new LegacyHitSampleInfo(HitSampleInfo.HIT_NORMAL, bankInfo.BankForNormal, bankInfo.Volume, bankInfo.CustomSampleBank,
                    // if the sound type doesn't have the Normal flag set, attach it anyway as a layered sample.
                    // None also counts as a normal non-layered sample: https://osu.ppy.sh/help/wiki/osu!_File_Formats/Osu_(file_format)#hitsounds
                    type != LegacyHitSoundType.None && !type.HasFlag(LegacyHitSoundType.Normal)));
            }
            else
            {
                // Todo: This should set the normal SampleInfo if the specified sample file isn't found, but that's a pretty edge-case scenario
                soundTypes.Add(new FileHitSampleInfo(bankInfo.Filename, bankInfo.Volume));
            }

            if (type.HasFlag(LegacyHitSoundType.Finish))
                soundTypes.Add(new LegacyHitSampleInfo(HitSampleInfo.HIT_FINISH, bankInfo.BankForAdditions, bankInfo.Volume, bankInfo.CustomSampleBank));

            if (type.HasFlag(LegacyHitSoundType.Whistle))
                soundTypes.Add(new LegacyHitSampleInfo(HitSampleInfo.HIT_WHISTLE, bankInfo.BankForAdditions, bankInfo.Volume, bankInfo.CustomSampleBank));

            if (type.HasFlag(LegacyHitSoundType.Clap))
                soundTypes.Add(new LegacyHitSampleInfo(HitSampleInfo.HIT_CLAP, bankInfo.BankForAdditions, bankInfo.Volume, bankInfo.CustomSampleBank));

            return soundTypes;
        }

        private class SampleBankInfo
        {
            /// <summary>
            /// An optional overriding filename which causes all bank/sample specifications to be ignored.
            /// </summary>
            public string Filename;

            /// <summary>
            /// The bank identifier to use for the base ("hitnormal") sample.
            /// Transferred to <see cref="HitSampleInfo.Bank"/> when appropriate.
            /// </summary>
            [CanBeNull]
            public string BankForNormal;

            /// <summary>
            /// The bank identifier to use for additions ("hitwhistle", "hitfinish", "hitclap").
            /// Transferred to <see cref="HitSampleInfo.Bank"/> when appropriate.
            /// </summary>
            [CanBeNull]
            public string BankForAdditions;

            /// <summary>
            /// Hit sample volume (0-100).
            /// See <see cref="HitSampleInfo.Volume"/>.
            /// </summary>
            public int Volume;

            /// <summary>
            /// The index of the custom sample bank. Is only used if 2 or above for "reasons".
            /// This will add a suffix to lookups, allowing extended bank lookups (ie. "normal-hitnormal-2").
            /// See <see cref="HitSampleInfo.Suffix"/>.
            /// </summary>
            public int CustomSampleBank;

            public SampleBankInfo Clone() => (SampleBankInfo)MemberwiseClone();
        }

#nullable enable

        public class LegacyHitSampleInfo : HitSampleInfo, IEquatable<LegacyHitSampleInfo>
        {
            public readonly int CustomSampleBank;

            /// <summary>
            /// Whether this hit sample is layered.
            /// </summary>
            /// <remarks>
            /// Layered hit samples are automatically added in all modes (except osu!mania), but can be disabled
            /// using the <see cref="SkinConfiguration.LegacySetting.LayeredHitSounds"/> skin config option.
            /// </remarks>
            public readonly bool IsLayered;

            /// <summary>
            /// Whether a bank was specified locally to the relevant hitobject.
            /// If <c>false</c>, a bank will be retrieved from the closest control point.
            /// </summary>
            public bool BankSpecified;

            public LegacyHitSampleInfo(string name, string? bank = null, int volume = 0, int customSampleBank = 0, bool isLayered = false)
                : base(name, bank ?? SampleControlPoint.DEFAULT_BANK, customSampleBank >= 2 ? customSampleBank.ToString() : null, volume)
            {
                CustomSampleBank = customSampleBank;
                BankSpecified = !string.IsNullOrEmpty(bank);
                IsLayered = isLayered;
            }

            public sealed override HitSampleInfo With(Optional<string> newName = default, Optional<string> newBank = default, Optional<string?> newSuffix = default, Optional<int> newVolume = default)
                => With(newName, newBank, newVolume);

            public virtual LegacyHitSampleInfo With(Optional<string> newName = default, Optional<string> newBank = default, Optional<int> newVolume = default,
                                                    Optional<int> newCustomSampleBank = default,
                                                    Optional<bool> newIsLayered = default)
                => new LegacyHitSampleInfo(newName.GetOr(Name), newBank.GetOr(Bank), newVolume.GetOr(Volume), newCustomSampleBank.GetOr(CustomSampleBank), newIsLayered.GetOr(IsLayered));

            public bool Equals(LegacyHitSampleInfo? other)
                // The additions to equality checks here are *required* to ensure that pooling works correctly.
                // Of note, `IsLayered` may cause the usage of `SampleVirtual` instead of an actual sample (in cases playback is not required).
                // Removing it would cause samples which may actually require playback to potentially source for a `SampleVirtual` sample pool.
                => base.Equals(other) && CustomSampleBank == other.CustomSampleBank && IsLayered == other.IsLayered;

            public override bool Equals(object? obj)
                => obj is LegacyHitSampleInfo other && Equals(other);

            public override int GetHashCode() => HashCode.Combine(base.GetHashCode(), CustomSampleBank, IsLayered);
        }

        private class FileHitSampleInfo : LegacyHitSampleInfo, IEquatable<FileHitSampleInfo>
        {
            public readonly string Filename;

            public FileHitSampleInfo(string filename, int volume)
                // Force CSS=1 to make sure that the LegacyBeatmapSkin does not fall back to the user skin.
                // Note that this does not change the lookup names, as they are overridden locally.
                : base(string.Empty, customSampleBank: 1, volume: volume)
            {
                Filename = filename;
            }

            public override IEnumerable<string> LookupNames => new[]
            {
                Filename,
                Path.ChangeExtension(Filename, null)
            };

            public sealed override LegacyHitSampleInfo With(Optional<string> newName = default, Optional<string> newBank = default, Optional<int> newVolume = default,
                                                            Optional<int> newCustomSampleBank = default,
                                                            Optional<bool> newIsLayered = default)
                => new FileHitSampleInfo(Filename, newVolume.GetOr(Volume));

            public bool Equals(FileHitSampleInfo? other)
                => base.Equals(other) && Filename == other.Filename;

            public override bool Equals(object? obj)
                => obj is FileHitSampleInfo other && Equals(other);

            public override int GetHashCode() => HashCode.Combine(base.GetHashCode(), Filename);
        }
    }
}