// Copyright (c) 2007-2017 ppy Pty Ltd <contact@ppy.sh>.
// Licensed under the MIT Licence - https://raw.githubusercontent.com/ppy/osu/master/LICENCE

using OpenTK;
using osu.Framework.MathUtils;
using osu.Game.Beatmaps;
using osu.Game.Rulesets.Osu.Objects;
using osu.Game.Rulesets.Osu.Objects.Drawables;
using System;
using System.Collections.Generic;
using System.Diagnostics;
using osu.Framework.Graphics;
using osu.Game.Rulesets.Objects.Types;
using osu.Game.Rulesets.Replays;

namespace osu.Game.Rulesets.Osu
{
    public class OsuAutoReplay : Replay
    {
        private static readonly Vector2 spinner_centre = new Vector2(256, 192);

        private const float spin_radius = 50;

        private readonly Beatmap<OsuHitObject> beatmap;

        public OsuAutoReplay(Beatmap<OsuHitObject> beatmap)
        {
            this.beatmap = beatmap;

            createAutoReplay();
        }

        private class ReplayFrameComparer : IComparer<ReplayFrame>
        {
            public int Compare(ReplayFrame f1, ReplayFrame f2)
            {
                if (f1 == null) throw new NullReferenceException($@"{nameof(f1)} cannot be null");
                if (f2 == null) throw new NullReferenceException($@"{nameof(f2)} cannot be null");

                return f1.Time.CompareTo(f2.Time);
            }
        }

        private static readonly IComparer<ReplayFrame> replay_frame_comparer = new ReplayFrameComparer();

        private int findInsertionIndex(ReplayFrame frame)
        {
            int index = Frames.BinarySearch(frame, replay_frame_comparer);

            if (index < 0)
            {
                index = ~index;
            }
            else
            {
                // Go to the first index which is actually bigger
                while (index < Frames.Count && frame.Time == Frames[index].Time)
                {
                    ++index;
                }
            }

            return index;
        }

        private void addFrameToReplay(ReplayFrame frame) => Frames.Insert(findInsertionIndex(frame), frame);

        private static Vector2 circlePosition(double t, double radius) => new Vector2((float)(Math.Cos(t) * radius), (float)(Math.Sin(t) * radius));

        private double applyModsToTime(double v) => v;
        private double applyModsToRate(double v) => v;

        public bool DelayedMovements; // ModManager.CheckActive(Mods.Relax2);

        private void createAutoReplay()
        {
            int buttonIndex = 0;

            EasingTypes preferredEasing = DelayedMovements ? EasingTypes.InOutCubic : EasingTypes.Out;

            addFrameToReplay(new ReplayFrame(-100000, 256, 500, ReplayButtonState.None));
            addFrameToReplay(new ReplayFrame(beatmap.HitObjects[0].StartTime - 1500, 256, 500, ReplayButtonState.None));
            addFrameToReplay(new ReplayFrame(beatmap.HitObjects[0].StartTime - 1000, 256, 192, ReplayButtonState.None));

            // We are using ApplyModsToRate and not ApplyModsToTime to counteract the speed up / slow down from HalfTime / DoubleTime so that we remain at a constant framerate of 60 fps.
            float frameDelay = (float)applyModsToRate(1000.0 / 60.0);

            // Already superhuman, but still somewhat realistic
            int reactionTime = (int)applyModsToRate(100);


            for (int i = 0; i < beatmap.HitObjects.Count; i++)
            {
                OsuHitObject h = beatmap.HitObjects[i];

                //if (h.EndTime < InputManager.ReplayStartTime)
                //{
                //    h.IsHit = true;
                //    continue;
                //}

                int endDelay = h is Spinner ? 1 : 0;

                if (DelayedMovements && i > 0)
                {
                    OsuHitObject last = beatmap.HitObjects[i - 1];

                    double endTime = (last as IHasEndTime)?.EndTime ?? last.StartTime;

                    //Make the cursor stay at a hitObject as long as possible (mainly for autopilot).
                    if (h.StartTime - h.HitWindowFor(OsuScoreResult.Miss) > endTime + h.HitWindowFor(OsuScoreResult.Hit50) + 50)
                    {
                        if (!(last is Spinner) && h.StartTime - endTime < 1000) addFrameToReplay(new ReplayFrame(endTime + h.HitWindowFor(OsuScoreResult.Hit50), last.EndPosition.X, last.EndPosition.Y, ReplayButtonState.None));
                        if (!(h is Spinner)) addFrameToReplay(new ReplayFrame(h.StartTime - h.HitWindowFor(OsuScoreResult.Miss), h.Position.X, h.Position.Y, ReplayButtonState.None));
                    }
                    else if (h.StartTime - h.HitWindowFor(OsuScoreResult.Hit50) > endTime + h.HitWindowFor(OsuScoreResult.Hit50) + 50)
                    {
                        if (!(last is Spinner) && h.StartTime - endTime < 1000) addFrameToReplay(new ReplayFrame(endTime + h.HitWindowFor(OsuScoreResult.Hit50), last.EndPosition.X, last.EndPosition.Y, ReplayButtonState.None));
                        if (!(h is Spinner)) addFrameToReplay(new ReplayFrame(h.StartTime - h.HitWindowFor(OsuScoreResult.Hit50), h.Position.X, h.Position.Y, ReplayButtonState.None));
                    }
                    else if (h.StartTime - h.HitWindowFor(OsuScoreResult.Hit100) > endTime + h.HitWindowFor(OsuScoreResult.Hit100) + 50)
                    {
                        if (!(last is Spinner) && h.StartTime - endTime < 1000) addFrameToReplay(new ReplayFrame(endTime + h.HitWindowFor(OsuScoreResult.Hit100), last.EndPosition.X, last.EndPosition.Y, ReplayButtonState.None));
                        if (!(h is Spinner)) addFrameToReplay(new ReplayFrame(h.StartTime - h.HitWindowFor(OsuScoreResult.Hit100), h.Position.X, h.Position.Y, ReplayButtonState.None));
                    }
                }


                Vector2 targetPosition = h.Position;
                EasingTypes easing = preferredEasing;
                float spinnerDirection = -1;

                if (h is Spinner)
                {
                    targetPosition.X = Frames[Frames.Count - 1].MouseX;
                    targetPosition.Y = Frames[Frames.Count - 1].MouseY;

                    Vector2 difference = spinner_centre - targetPosition;

                    float differenceLength = difference.Length;
                    float newLength = (float)Math.Sqrt(differenceLength * differenceLength - spin_radius * spin_radius);

                    if (differenceLength > spin_radius)
                    {
                        float angle = (float)Math.Asin(spin_radius / differenceLength);

                        if (angle > 0)
                        {
                            spinnerDirection = -1;
                        }
                        else
                        {
                            spinnerDirection = 1;
                        }

                        difference.X = difference.X * (float)Math.Cos(angle) - difference.Y * (float)Math.Sin(angle);
                        difference.Y = difference.X * (float)Math.Sin(angle) + difference.Y * (float)Math.Cos(angle);

                        difference.Normalize();
                        difference *= newLength;

                        targetPosition += difference;

                        easing = EasingTypes.In;
                    }
                    else if (difference.Length > 0)
                    {
                        targetPosition = spinner_centre - difference * (spin_radius / difference.Length);
                    }
                    else
                    {
                        targetPosition = spinner_centre + new Vector2(0, -spin_radius);
                    }
                }


                // Do some nice easing for cursor movements
                if (Frames.Count > 0)
                {
                    ReplayFrame lastFrame = Frames[Frames.Count - 1];

                    // Wait until Auto could "see and react" to the next note.
                    double waitTime = h.StartTime - Math.Max(0.0, DrawableOsuHitObject.TIME_PREEMPT - reactionTime);
                    if (waitTime > lastFrame.Time)
                    {
                        lastFrame = new ReplayFrame(waitTime, lastFrame.MouseX, lastFrame.MouseY, lastFrame.ButtonState);
                        addFrameToReplay(lastFrame);
                    }

                    Vector2 lastPosition = new Vector2(lastFrame.MouseX, lastFrame.MouseY);

                    double timeDifference = applyModsToTime(h.StartTime - lastFrame.Time);

                    // Only "snap" to hitcircles if they are far enough apart. As the time between hitcircles gets shorter the snapping threshold goes up.
                    if (timeDifference > 0 && // Sanity checks
                        ((lastPosition - targetPosition).Length > h.Radius * (1.5 + 100.0 / timeDifference) || // Either the distance is big enough
                        timeDifference >= 266)) // ... or the beats are slow enough to tap anyway.
                    {
                        // Perform eased movement
                        for (double time = lastFrame.Time + frameDelay; time < h.StartTime; time += frameDelay)
                        {
                            Vector2 currentPosition = Interpolation.ValueAt(time, lastPosition, targetPosition, lastFrame.Time, h.StartTime, easing);
                            addFrameToReplay(new ReplayFrame((int)time, currentPosition.X, currentPosition.Y, lastFrame.ButtonState));
                        }

                        buttonIndex = 0;
                    }
                    else
                    {
                        buttonIndex++;
                    }
                }

                ReplayButtonState button = buttonIndex % 2 == 0 ? ReplayButtonState.Left1 : ReplayButtonState.Right1;

                double hEndTime = (h as IHasEndTime)?.EndTime ?? h.StartTime;

                ReplayFrame newFrame = new ReplayFrame(h.StartTime, targetPosition.X, targetPosition.Y, button);
                ReplayFrame endFrame = new ReplayFrame(hEndTime + endDelay, h.EndPosition.X, h.EndPosition.Y, ReplayButtonState.None);

                // Decrement because we want the previous frame, not the next one
                int index = findInsertionIndex(newFrame) - 1;

                // Do we have a previous frame? No need to check for < replay.Count since we decremented!
                if (index >= 0)
                {
                    ReplayFrame previousFrame = Frames[index];
                    var previousButton = previousFrame.ButtonState;

                    // If a button is already held, then we simply alternate
                    if (previousButton != ReplayButtonState.None)
                    {
                        Debug.Assert(previousButton != (ReplayButtonState.Left1 | ReplayButtonState.Right1));

                        // Force alternation if we have the same button. Otherwise we can just keep the naturally to us assigned button.
                        if (previousButton == button)
                        {
                            button = (ReplayButtonState.Left1 | ReplayButtonState.Right1) & ~button;
                            newFrame.ButtonState = button;
                        }

                        // We always follow the most recent slider / spinner, so remove any other frames that occur while it exists.
                        int endIndex = findInsertionIndex(endFrame);

                        if (index < Frames.Count - 1)
                            Frames.RemoveRange(index + 1, Math.Max(0, endIndex - (index + 1)));

                        // After alternating we need to keep holding the other button in the future rather than the previous one.
                        for (int j = index + 1; j < Frames.Count; ++j)
                        {
                            // Don't affect frames which stop pressing a button!
                            if (j < Frames.Count - 1 || Frames[j].ButtonState == previousButton)
                                Frames[j].ButtonState = button;
                        }
                    }
                }

                addFrameToReplay(newFrame);

                // We add intermediate frames for spinning / following a slider here.
                if (h is Spinner)
                {
                    Spinner s = h as Spinner;

                    Vector2 difference = targetPosition - spinner_centre;

                    float radius = difference.Length;
                    float angle = radius == 0 ? 0 : (float)Math.Atan2(difference.Y, difference.X);

                    double t;

                    for (double j = h.StartTime + frameDelay; j < s.EndTime; j += frameDelay)
                    {
                        t = applyModsToTime(j - h.StartTime) * spinnerDirection;

                        Vector2 pos = spinner_centre + circlePosition(t / 20 + angle, spin_radius);
                        addFrameToReplay(new ReplayFrame((int)j, pos.X, pos.Y, button));
                    }

                    t = applyModsToTime(s.EndTime - h.StartTime) * spinnerDirection;
                    Vector2 endPosition = spinner_centre + circlePosition(t / 20 + angle, spin_radius);

                    addFrameToReplay(new ReplayFrame(s.EndTime, endPosition.X, endPosition.Y, button));

                    endFrame.MouseX = endPosition.X;
                    endFrame.MouseY = endPosition.Y;
                }
                else if (h is Slider)
                {
                    Slider s = h as Slider;

                    for (double j = frameDelay; j < s.Duration; j += frameDelay)
                    {
                        Vector2 pos = s.PositionAt(j / s.Duration);
                        addFrameToReplay(new ReplayFrame(h.StartTime + j, pos.X, pos.Y, button));
                    }

                    addFrameToReplay(new ReplayFrame(s.EndTime, s.EndPosition.X, s.EndPosition.Y, button));
                }

                // We only want to let go of our button if we are at the end of the current replay. Otherwise something is still going on after us so we need to keep the button pressed!
                if (Frames[Frames.Count - 1].Time <= endFrame.Time)
                    addFrameToReplay(endFrame);
            }

            //Player.currentScore.Replay = InputManager.ReplayScore.Replay;
            //Player.currentScore.PlayerName = "osu!";
        }
    }
}