// 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 System;
using System.Collections.Generic;
using System.Diagnostics;
using System.IO;
using System.Linq;
using Newtonsoft.Json;
using osu.Game.Beatmaps;
using osu.Game.Beatmaps.Formats;
using osu.Game.Beatmaps.Legacy;
using osu.Game.Database;
using osu.Game.Extensions;
using osu.Game.IO.Legacy;
using osu.Game.Online.API.Requests.Responses;
using osu.Game.Replays;
using osu.Game.Replays.Legacy;
using osu.Game.Rulesets;
using osu.Game.Rulesets.Mods;
using osu.Game.Rulesets.Replays;
using osu.Game.Rulesets.Scoring;
using osuTK;
using SharpCompress.Compressors.LZMA;

namespace osu.Game.Scoring.Legacy
{
    public abstract class LegacyScoreDecoder
    {
        private IBeatmap currentBeatmap;
        private Ruleset currentRuleset;

        private long beatmapOffset;

        public Score Parse(Stream stream)
        {
            var score = new Score
            {
                Replay = new Replay()
            };

            WorkingBeatmap workingBeatmap;
            ScoreRank? decodedRank = null;

            using (SerializationReader sr = new SerializationReader(stream))
            {
                currentRuleset = GetRuleset(sr.ReadByte());
                var scoreInfo = new ScoreInfo { Ruleset = currentRuleset.RulesetInfo };

                score.ScoreInfo = scoreInfo;

                int version = sr.ReadInt32();

                scoreInfo.IsLegacyScore = version < LegacyScoreEncoder.FIRST_LAZER_VERSION;

                // TotalScoreVersion gets initialised to LATEST_VERSION.
                // In the case where the incoming score has either an osu!stable or old lazer version, we need
                // to mark it with the correct version increment to trigger reprocessing to new standardised scoring.
                //
                // See StandardisedScoreMigrationTools.ShouldMigrateToNewStandardised().
                scoreInfo.TotalScoreVersion = version < 30000002 ? 30000001 : LegacyScoreEncoder.LATEST_VERSION;

                string beatmapHash = sr.ReadString();

                workingBeatmap = GetBeatmap(beatmapHash);

                if (workingBeatmap is DummyWorkingBeatmap)
                    throw new BeatmapNotFoundException(beatmapHash);

                scoreInfo.User = new APIUser { Username = sr.ReadString() };

                // MD5Hash
                sr.ReadString();

                scoreInfo.SetCount300(sr.ReadUInt16());
                scoreInfo.SetCount100(sr.ReadUInt16());
                scoreInfo.SetCount50(sr.ReadUInt16());
                scoreInfo.SetCountGeki(sr.ReadUInt16());
                scoreInfo.SetCountKatu(sr.ReadUInt16());
                scoreInfo.SetCountMiss(sr.ReadUInt16());

                scoreInfo.TotalScore = sr.ReadInt32();
                scoreInfo.MaxCombo = sr.ReadUInt16();

                /* score.Perfect = */
                sr.ReadBoolean();

                scoreInfo.Mods = currentRuleset.ConvertFromLegacyMods((LegacyMods)sr.ReadInt32()).ToArray();

                // lazer replays get a really high version number.
                if (version < LegacyScoreEncoder.FIRST_LAZER_VERSION)
                    scoreInfo.Mods = scoreInfo.Mods.Append(currentRuleset.CreateMod<ModClassic>()).ToArray();

                currentBeatmap = workingBeatmap.GetPlayableBeatmap(currentRuleset.RulesetInfo, scoreInfo.Mods);
                scoreInfo.BeatmapInfo = currentBeatmap.BeatmapInfo;

                // As this is baked into hitobject timing (see `LegacyBeatmapDecoder`) we also need to apply this to replay frame timing.
                beatmapOffset = currentBeatmap.BeatmapVersion < 5 ? LegacyBeatmapDecoder.EARLY_VERSION_TIMING_OFFSET : 0;

                /* score.HpGraphString = */
                sr.ReadString();

                scoreInfo.Date = sr.ReadDateTime();

                byte[] compressedReplay = sr.ReadByteArray();

                if (version >= 20140721)
                    scoreInfo.LegacyOnlineID = sr.ReadInt64();
                else if (version >= 20121008)
                    scoreInfo.LegacyOnlineID = sr.ReadInt32();

                if (scoreInfo.LegacyOnlineID == 0)
                    scoreInfo.LegacyOnlineID = -1;

                byte[] compressedScoreInfo = null;

                if (version >= 30000001)
                    compressedScoreInfo = sr.ReadByteArray();

                if (compressedReplay?.Length > 0)
                    readCompressedData(compressedReplay, reader => readLegacyReplay(score.Replay, reader));

                if (compressedScoreInfo?.Length > 0)
                {
                    readCompressedData(compressedScoreInfo, reader =>
                    {
                        LegacyReplaySoloScoreInfo readScore = JsonConvert.DeserializeObject<LegacyReplaySoloScoreInfo>(reader.ReadToEnd());

                        Debug.Assert(readScore != null);

                        score.ScoreInfo.OnlineID = readScore.OnlineID;
                        score.ScoreInfo.Statistics = readScore.Statistics;
                        score.ScoreInfo.MaximumStatistics = readScore.MaximumStatistics;
                        score.ScoreInfo.Mods = readScore.Mods.Select(m => m.ToMod(currentRuleset)).ToArray();
                        score.ScoreInfo.ClientVersion = readScore.ClientVersion;
                        decodedRank = readScore.Rank;
                        if (readScore.UserID > 1)
                            score.ScoreInfo.RealmUser.OnlineID = readScore.UserID;

                        if (readScore.TotalScoreWithoutMods is long totalScoreWithoutMods)
                            score.ScoreInfo.TotalScoreWithoutMods = totalScoreWithoutMods;
                        else
                            PopulateTotalScoreWithoutMods(score.ScoreInfo);

                        score.ScoreInfo.Pauses.AddRange(readScore.Pauses);
                    });
                }
            }

            PopulateMaximumStatistics(score.ScoreInfo, workingBeatmap);

            if (score.ScoreInfo.IsLegacyScore)
                score.ScoreInfo.LegacyTotalScore = score.ScoreInfo.TotalScore;

            StandardisedScoreMigrationTools.UpdateFromLegacy(score.ScoreInfo, workingBeatmap);

            if (decodedRank != null)
                score.ScoreInfo.Rank = decodedRank.Value;

            // before returning for database import, we must restore the database-sourced BeatmapInfo.
            // if not, the clone operation in GetPlayableBeatmap will cause a dereference and subsequent database exception.
            score.ScoreInfo.BeatmapInfo = workingBeatmap.BeatmapInfo;
            score.ScoreInfo.BeatmapHash = workingBeatmap.BeatmapInfo.Hash;

            return score;
        }

        private void readCompressedData(byte[] data, Action<StreamReader> readFunc)
        {
            using (var replayInStream = new MemoryStream(data))
            {
                byte[] properties = new byte[5];
                if (replayInStream.Read(properties, 0, 5) != 5)
                    throw new IOException("input .lzma is too short");

                long outSize = 0;

                for (int i = 0; i < 8; i++)
                {
                    int v = replayInStream.ReadByte();
                    if (v < 0)
                        throw new IOException("Can't Read 1");

                    outSize |= (long)(byte)v << (8 * i);
                }

                long compressedSize = replayInStream.Length - replayInStream.Position;

                using (var lzma = LzmaStream.Create(properties, replayInStream, compressedSize, outSize))
                using (var reader = new StreamReader(lzma))
                    readFunc(reader);
            }
        }

        /// <summary>
        /// Populates the <see cref="ScoreInfo.MaximumStatistics"/> for a given <see cref="ScoreInfo"/>.
        /// </summary>
        /// <param name="score">The score to populate the statistics of.</param>
        /// <param name="workingBeatmap">The corresponding <see cref="WorkingBeatmap"/>.</param>
        public static void PopulateMaximumStatistics(ScoreInfo score, WorkingBeatmap workingBeatmap)
        {
            Debug.Assert(score.BeatmapInfo != null);

            if (score.MaximumStatistics.Select(kvp => kvp.Value).Sum() > 0)
                return;

            var ruleset = score.Ruleset.Detach();
            var rulesetInstance = ruleset.CreateInstance();
            var scoreProcessor = rulesetInstance.CreateScoreProcessor();

            // Populate the maximum statistics.
            HitResult maxBasicResult = rulesetInstance.GetHitResultsForDisplay()
                                                      .Select(h => h.result)
                                                      .Where(h => h.IsBasic()).MaxBy(scoreProcessor.GetBaseScoreForResult);

            foreach ((HitResult result, int count) in score.Statistics)
            {
                switch (result)
                {
                    case HitResult.LargeTickHit:
                    case HitResult.LargeTickMiss:
                        score.MaximumStatistics[HitResult.LargeTickHit] = score.MaximumStatistics.GetValueOrDefault(HitResult.LargeTickHit) + count;
                        break;

                    case HitResult.SmallTickHit:
                    case HitResult.SmallTickMiss:
                        score.MaximumStatistics[HitResult.SmallTickHit] = score.MaximumStatistics.GetValueOrDefault(HitResult.SmallTickHit) + count;
                        break;

                    case HitResult.IgnoreHit:
                    case HitResult.IgnoreMiss:
                    case HitResult.SmallBonus:
                    case HitResult.LargeBonus:
                        break;

                    default:
                        score.MaximumStatistics[maxBasicResult] = score.MaximumStatistics.GetValueOrDefault(maxBasicResult) + count;
                        break;
                }
            }

            if (!score.IsLegacyScore)
                return;

#pragma warning disable CS0618
            // In osu! and osu!mania, some judgements affect combo but aren't stored to scores.
            // A special hit result is used to pad out the combo value to match, based on the max combo from the difficulty attributes.
            var calculator = rulesetInstance.CreateDifficultyCalculator(workingBeatmap);
            var attributes = calculator.Calculate(score.Mods);

            int maxComboFromStatistics = score.MaximumStatistics.Where(kvp => kvp.Key.AffectsCombo()).Select(kvp => kvp.Value).DefaultIfEmpty(0).Sum();
            if (attributes.MaxCombo > maxComboFromStatistics)
                score.MaximumStatistics[HitResult.LegacyComboIncrease] = attributes.MaxCombo - maxComboFromStatistics;
#pragma warning restore CS0618
        }

        public static void PopulateTotalScoreWithoutMods(ScoreInfo score)
        {
            Debug.Assert(score.BeatmapInfo != null);

            var ruleset = score.Ruleset.CreateInstance();
            var scoreMultiplierCalculator = ruleset.CreateScoreMultiplierCalculator(new ScoreMultiplierContext(score.BeatmapInfo.Difficulty, score));
            double modMultiplier = scoreMultiplierCalculator.CalculateFor(score.Mods);

            score.TotalScoreWithoutMods = (long)Math.Round(score.TotalScore / modMultiplier);
        }

        private void readLegacyReplay(Replay replay, StreamReader reader)
        {
            long lastTime = beatmapOffset;
            var legacyFrames = new List<LegacyReplayFrame>();

            string[] frames = reader.ReadToEnd().Split(',');

            for (int i = 0; i < frames.Length; i++)
            {
                string[] split = frames[i].Split('|');

                if (split.Length < 4)
                    continue;

                if (split[0] == "-12345")
                {
                    // Todo: The seed is provided in split[3], which we'll need to use at some point
                    continue;
                }

                // In mania, mouseX encodes the pressed keys in the lower 20 bits
                int mouseXParseLimit = currentRuleset.RulesetInfo.OnlineID == 3 ? (1 << 20) - 1 : Parsing.MAX_COORDINATE_VALUE;

                // the legacy replay format as defined by stable expects frame delta times
                // ('delta time' here meaning the amount of time between consecutive frames)
                // to be integral and does not allow fractional values.
                // one particular reason why this matters is that integral deltas
                // avoid nasty floating point traps like accumulation error from summation or round-off error.
                // however, there was a period in lazer's lifetime wherein lazer emitted replays
                // with fractional (float) frame deltas, up until https://github.com/ppy/osu/pull/12583.
                // despite the fact that gameplay mechanics changed multiple times since
                // and the replay isn't going to play back anywhere near accurately anyway,
                // no mistakes are ever forgiven, thus this attempts to parse the delta as an integer once,
                // and if that fails, tries again as float.
                // notably this cannot just be `(int)Parsing.ParseFloat(split[0])`, because that can lose information
                // (`float` numbers have 24 bits of significand precision, which is not enough to accurately represent every possible value of `int`).
                int diff;
                if (!int.TryParse(split[0], out diff))
                    diff = (int)Math.Round(Parsing.ParseFloat(split[0]));

                float mouseX = Parsing.ParseFloat(split[1], mouseXParseLimit);
                float mouseY = Parsing.ParseFloat(split[2], Parsing.MAX_COORDINATE_VALUE);

                lastTime += diff;

                legacyFrames.Add(new LegacyReplayFrame(lastTime,
                    mouseX,
                    mouseY,
                    (ReplayButtonState)Parsing.ParseInt(split[3])));
            }

            // https://github.com/peppy/osu-stable-reference/blob/e53980dd76857ee899f66ce519ba1597e7874f28/osu!/GameModes/Play/ReplayWatcher.cs#L62-L67
            if (legacyFrames.Count >= 2 && legacyFrames[1].Time < legacyFrames[0].Time)
            {
                legacyFrames[1].Time = legacyFrames[0].Time;
                legacyFrames[0].Time = 0;
            }

            // https://github.com/peppy/osu-stable-reference/blob/e53980dd76857ee899f66ce519ba1597e7874f28/osu!/GameModes/Play/ReplayWatcher.cs#L69-L71
            if (legacyFrames.Count >= 3 && legacyFrames[0].Time > legacyFrames[2].Time)
                legacyFrames[0].Time = legacyFrames[1].Time = legacyFrames[2].Time;

            // at the start of the replay, stable places two replay frames, at time 0 and SkipBoundary - 1, respectively.
            // both frames use a position of (256, -500).
            // ignore these frames as they serve no real purpose (and can even mislead ruleset-specific handlers - see mania)
            if (legacyFrames.Count >= 2 && legacyFrames[1].Position == new Vector2(256, -500))
                legacyFrames.RemoveAt(1);

            if (legacyFrames.Count >= 1 && legacyFrames[0].Position == new Vector2(256, -500))
                legacyFrames.RemoveAt(0);

            ReplayFrame currentFrame = null;

            foreach (var legacyFrame in legacyFrames)
            {
                // never allow backwards time traversal in relation to the current frame.
                // this handles frames with negative delta.
                // this doesn't match stable 100% as stable will do something similar to adding an interpolated "intermediate frame"
                // at the point wherein time flow changes from backwards to forwards, but it'll do for now.
                if (currentFrame != null && legacyFrame.Time < currentFrame.Time)
                    continue;

                replay.Frames.Add(currentFrame = convertFrame(legacyFrame, currentFrame));
            }
        }

        private ReplayFrame convertFrame(LegacyReplayFrame currentFrame, ReplayFrame lastFrame)
        {
            var convertible = currentRuleset.CreateConvertibleReplayFrame();
            if (convertible == null)
                throw new InvalidOperationException($"Legacy replay cannot be converted for the ruleset: {currentRuleset.Description}");

            convertible.FromLegacy(currentFrame, currentBeatmap, lastFrame);

            var frame = (ReplayFrame)convertible;
            frame.Time = currentFrame.Time;

            return frame;
        }

        /// <summary>
        /// Retrieves the <see cref="Ruleset"/> for a specific id.
        /// </summary>
        /// <param name="rulesetId">The id.</param>
        /// <returns>The <see cref="Ruleset"/>.</returns>
        protected abstract Ruleset GetRuleset(int rulesetId);

        /// <summary>
        /// Retrieves the <see cref="WorkingBeatmap"/> corresponding to an MD5 hash.
        /// </summary>
        /// <param name="md5Hash">The MD5 hash.</param>
        /// <returns>The <see cref="WorkingBeatmap"/>.</returns>
        protected abstract WorkingBeatmap GetBeatmap(string md5Hash);

        public class BeatmapNotFoundException : Exception
        {
            public string Hash { get; }

            public BeatmapNotFoundException(string hash)
            {
                Hash = hash;
            }
        }
    }
}
