// Copyright (c) 2007-2018 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 osu.Framework.MathUtils;
using osu.Game.Beatmaps;
using osu.Game.Rulesets.Catch.Objects;
using osu.Game.Rulesets.Catch.UI;
using osu.Game.Rulesets.Replays;
using osu.Game.Users;

namespace osu.Game.Rulesets.Catch.Replays
{
    internal class CatchAutoGenerator : AutoGenerator<CatchHitObject>
    {
        public const double RELEASE_DELAY = 20;

        public CatchAutoGenerator(Beatmap<CatchHitObject> beatmap)
            : base(beatmap)
        {
            Replay = new Replay { User = new User { Username = @"Autoplay" } };
        }

        protected Replay Replay;

        public override Replay Generate()
        {
            // todo: add support for HT DT
            const double dash_speed = CatcherArea.Catcher.BASE_SPEED;
            const double movement_speed = dash_speed / 2;
            float lastPosition = 0.5f;
            double lastTime = 0;

            // Todo: Realistically this shouldn't be needed, but the first frame is skipped with the way replays are currently handled
            Replay.Frames.Add(new CatchReplayFrame(-100000, lastPosition));

            void moveToNext(CatchHitObject h)
            {
                float positionChange = Math.Abs(lastPosition - h.X);
                double timeAvailable = h.StartTime - lastTime;

                //So we can either make it there without a dash or not.
                double speedRequired = positionChange / timeAvailable;

                bool dashRequired = speedRequired > movement_speed && h.StartTime != 0;

                // todo: get correct catcher size, based on difficulty CS.
                const float catcher_width_half = CatcherArea.CATCHER_SIZE / CatchPlayfield.BASE_WIDTH * 0.3f * 0.5f;

                if (lastPosition - catcher_width_half < h.X && lastPosition + catcher_width_half > h.X)
                {
                    //we are already in the correct range.
                    lastTime = h.StartTime;
                    Replay.Frames.Add(new CatchReplayFrame(h.StartTime, lastPosition));
                    return;
                }

                if (h is BananaShower.Banana)
                {
                    // auto bananas unrealistically warp to catch 100% combo.
                    Replay.Frames.Add(new CatchReplayFrame(h.StartTime, h.X));
                }
                else if (h.HyperDash)
                {
                    Replay.Frames.Add(new CatchReplayFrame(h.StartTime - timeAvailable, lastPosition, true));
                    Replay.Frames.Add(new CatchReplayFrame(h.StartTime, h.X));
                }
                else if (dashRequired)
                {
                    //we do a movement in two parts - the dash part then the normal part...
                    double timeAtNormalSpeed = positionChange / movement_speed;
                    double timeWeNeedToSave = timeAtNormalSpeed - timeAvailable;
                    double timeAtDashSpeed = timeWeNeedToSave / 2;

                    float midPosition = (float)Interpolation.Lerp(lastPosition, h.X, (float)timeAtDashSpeed / timeAvailable);

                    //dash movement
                    Replay.Frames.Add(new CatchReplayFrame(h.StartTime - timeAvailable + 1, lastPosition, true));
                    Replay.Frames.Add(new CatchReplayFrame(h.StartTime - timeAvailable + timeAtDashSpeed, midPosition));
                    Replay.Frames.Add(new CatchReplayFrame(h.StartTime, h.X));
                }
                else
                {
                    double timeBefore = positionChange / movement_speed;

                    Replay.Frames.Add(new CatchReplayFrame(h.StartTime - timeBefore, lastPosition, true));
                    Replay.Frames.Add(new CatchReplayFrame(h.StartTime, h.X));
                }

                lastTime = h.StartTime;
                lastPosition = h.X;
            }

            foreach (var obj in Beatmap.HitObjects)
            {
                switch (obj)
                {
                    case Fruit _:
                        moveToNext(obj);
                        break;
                }

                foreach (var nestedObj in obj.NestedHitObjects.Cast<CatchHitObject>())
                {
                    switch (nestedObj)
                    {
                        case BananaShower.Banana _:
                        case TinyDroplet _:
                        case Droplet _:
                            moveToNext(nestedObj);
                            break;
                    }
                }
            }

            return Replay;
        }
    }
}