// 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.

using System;
using System.Linq;
using JetBrains.Annotations;
using osu.Framework.Allocation;
using osu.Framework.Bindables;
using osu.Framework.Graphics;
using osu.Framework.Graphics.Animations;
using osu.Framework.Graphics.Containers;
using osu.Framework.Graphics.Pooling;
using osu.Framework.Input.Bindings;
using osu.Framework.Utils;
using osu.Game.Beatmaps;
using osu.Game.Configuration;
using osu.Game.Rulesets.Catch.Judgements;
using osu.Game.Rulesets.Catch.Objects;
using osu.Game.Rulesets.Catch.Objects.Drawables;
using osu.Game.Rulesets.Catch.Skinning;
using osu.Game.Rulesets.Judgements;
using osu.Game.Skinning;
using osuTK;
using osuTK.Graphics;

namespace osu.Game.Rulesets.Catch.UI
{
    public class Catcher : SkinReloadableDrawable, IKeyBindingHandler<CatchAction>
    {
        /// <summary>
        /// The default colour used to tint hyper-dash fruit, along with the moving catcher, its trail
        /// and end glow/after-image during a hyper-dash.
        /// </summary>
        public static readonly Color4 DEFAULT_HYPER_DASH_COLOUR = Color4.Red;

        /// <summary>
        /// The duration between transitioning to hyper-dash state.
        /// </summary>
        public const double HYPER_DASH_TRANSITION_DURATION = 180;

        /// <summary>
        /// Whether we are hyper-dashing or not.
        /// </summary>
        public bool HyperDashing => hyperDashModifier != 1;

        /// <summary>
        /// The relative space to cover in 1 millisecond. based on 1 game pixel per millisecond as in osu-stable.
        /// </summary>
        public const double BASE_SPEED = 1.0;

        [NotNull]
        private readonly Container trailsTarget;

        private CatcherTrailDisplay trails;

        private readonly Container droppedObjectTarget;

        private readonly Container<CaughtObject> caughtFruitContainer;

        public CatcherAnimationState CurrentState { get; private set; }

        /// <summary>
        /// The width of the catcher which can receive fruit. Equivalent to "catchMargin" in osu-stable.
        /// </summary>
        public const float ALLOWED_CATCH_RANGE = 0.8f;

        /// <summary>
        /// The drawable catcher for <see cref="CurrentState"/>.
        /// </summary>
        internal Drawable CurrentDrawableCatcher => currentCatcher.Drawable;

        private bool dashing;

        public bool Dashing
        {
            get => dashing;
            protected set
            {
                if (value == dashing) return;

                dashing = value;

                updateTrailVisibility();
            }
        }

        /// <summary>
        /// Width of the area that can be used to attempt catches during gameplay.
        /// </summary>
        private readonly float catchWidth;

        private readonly CatcherSprite catcherIdle;
        private readonly CatcherSprite catcherKiai;
        private readonly CatcherSprite catcherFail;

        private CatcherSprite currentCatcher;

        private Color4 hyperDashColour = DEFAULT_HYPER_DASH_COLOUR;
        private Color4 hyperDashEndGlowColour = DEFAULT_HYPER_DASH_COLOUR;

        private int currentDirection;

        private double hyperDashModifier = 1;
        private int hyperDashDirection;
        private float hyperDashTargetPosition;
        private Bindable<bool> hitLighting;

        private readonly DrawablePool<HitExplosion> hitExplosionPool;
        private readonly Container<HitExplosion> hitExplosionContainer;

        private readonly DrawablePool<CaughtFruit> caughtFruitPool;
        private readonly DrawablePool<CaughtBanana> caughtBananaPool;
        private readonly DrawablePool<CaughtDroplet> caughtDropletPool;

        public Catcher([NotNull] Container trailsTarget, [NotNull] Container droppedObjectTarget, BeatmapDifficulty difficulty = null)
        {
            this.trailsTarget = trailsTarget;
            this.droppedObjectTarget = droppedObjectTarget;

            Origin = Anchor.TopCentre;

            Size = new Vector2(CatcherArea.CATCHER_SIZE);
            if (difficulty != null)
                Scale = calculateScale(difficulty);

            catchWidth = CalculateCatchWidth(Scale);

            InternalChildren = new Drawable[]
            {
                hitExplosionPool = new DrawablePool<HitExplosion>(10),
                caughtFruitPool = new DrawablePool<CaughtFruit>(50),
                caughtBananaPool = new DrawablePool<CaughtBanana>(100),
                // less capacity is needed compared to fruit because droplet is not stacked
                caughtDropletPool = new DrawablePool<CaughtDroplet>(25),
                caughtFruitContainer = new Container<CaughtObject>
                {
                    Anchor = Anchor.TopCentre,
                    Origin = Anchor.BottomCentre,
                },
                catcherIdle = new CatcherSprite(CatcherAnimationState.Idle)
                {
                    Anchor = Anchor.TopCentre,
                    Alpha = 0,
                },
                catcherKiai = new CatcherSprite(CatcherAnimationState.Kiai)
                {
                    Anchor = Anchor.TopCentre,
                    Alpha = 0,
                },
                catcherFail = new CatcherSprite(CatcherAnimationState.Fail)
                {
                    Anchor = Anchor.TopCentre,
                    Alpha = 0,
                },
                hitExplosionContainer = new Container<HitExplosion>
                {
                    Anchor = Anchor.TopCentre,
                    Origin = Anchor.BottomCentre,
                },
            };
        }

        [BackgroundDependencyLoader]
        private void load(OsuConfigManager config)
        {
            hitLighting = config.GetBindable<bool>(OsuSetting.HitLighting);
            trails = new CatcherTrailDisplay(this);

            updateCatcher();
        }

        protected override void LoadComplete()
        {
            base.LoadComplete();

            // don't add in above load as we may potentially modify a parent in an unsafe manner.
            trailsTarget.Add(trails);
        }

        /// <summary>
        /// Creates proxied content to be displayed beneath hitobjects.
        /// </summary>
        public Drawable CreateProxiedContent() => caughtFruitContainer.CreateProxy();

        /// <summary>
        /// Calculates the scale of the catcher based off the provided beatmap difficulty.
        /// </summary>
        private static Vector2 calculateScale(BeatmapDifficulty difficulty) => new Vector2(1.0f - 0.7f * (difficulty.CircleSize - 5) / 5);

        /// <summary>
        /// Calculates the width of the area used for attempting catches in gameplay.
        /// </summary>
        /// <param name="scale">The scale of the catcher.</param>
        internal static float CalculateCatchWidth(Vector2 scale) => CatcherArea.CATCHER_SIZE * Math.Abs(scale.X) * ALLOWED_CATCH_RANGE;

        /// <summary>
        /// Calculates the width of the area used for attempting catches in gameplay.
        /// </summary>
        /// <param name="difficulty">The beatmap difficulty.</param>
        internal static float CalculateCatchWidth(BeatmapDifficulty difficulty) => CalculateCatchWidth(calculateScale(difficulty));

        /// <summary>
        /// Determine if this catcher can catch a <see cref="CatchHitObject"/> in the current position.
        /// </summary>
        public bool CanCatch(CatchHitObject hitObject)
        {
            if (!(hitObject is PalpableCatchHitObject fruit))
                return false;

            var halfCatchWidth = catchWidth * 0.5f;

            // this stuff wil disappear once we move fruit to non-relative coordinate space in the future.
            var catchObjectPosition = fruit.X;
            var catcherPosition = Position.X;

            return catchObjectPosition >= catcherPosition - halfCatchWidth &&
                   catchObjectPosition <= catcherPosition + halfCatchWidth;
        }

        public void OnNewResult(DrawableCatchHitObject drawableObject, JudgementResult result)
        {
            var catchResult = (CatchJudgementResult)result;
            catchResult.CatcherAnimationState = CurrentState;
            catchResult.CatcherHyperDash = HyperDashing;

            if (!(drawableObject is DrawablePalpableHasCatchHitObject palpableObject)) return;

            var hitObject = palpableObject.HitObject;

            if (result.IsHit)
            {
                var positionInStack = computePositionInStack(new Vector2(palpableObject.X - X, 0), palpableObject.DisplayRadius);

                placeCaughtObject(palpableObject, positionInStack);

                if (hitLighting.Value)
                    addLighting(hitObject, positionInStack.X, drawableObject.AccentColour.Value);
            }

            // droplet doesn't affect the catcher state
            if (hitObject is TinyDroplet) return;

            if (result.IsHit && hitObject.HyperDash)
            {
                var target = hitObject.HyperDashTarget;
                var timeDifference = target.StartTime - hitObject.StartTime;
                double positionDifference = target.X - X;
                var velocity = positionDifference / Math.Max(1.0, timeDifference - 1000.0 / 60.0);

                SetHyperDashState(Math.Abs(velocity), target.X);
            }
            else
                SetHyperDashState();

            if (result.IsHit)
                updateState(hitObject.Kiai ? CatcherAnimationState.Kiai : CatcherAnimationState.Idle);
            else if (!(hitObject is Banana))
                updateState(CatcherAnimationState.Fail);
        }

        public void OnRevertResult(DrawableCatchHitObject drawableObject, JudgementResult result)
        {
            var catchResult = (CatchJudgementResult)result;

            if (CurrentState != catchResult.CatcherAnimationState)
                updateState(catchResult.CatcherAnimationState);

            if (HyperDashing != catchResult.CatcherHyperDash)
            {
                if (catchResult.CatcherHyperDash)
                    SetHyperDashState(2);
                else
                    SetHyperDashState();
            }

            caughtFruitContainer.RemoveAll(d => d.HitObject == drawableObject.HitObject);
            droppedObjectTarget.RemoveAll(d => (d as CaughtObject)?.HitObject == drawableObject.HitObject);
            hitExplosionContainer.RemoveAll(d => d.HitObject == drawableObject.HitObject);
        }

        /// <summary>
        /// Set hyper-dash state.
        /// </summary>
        /// <param name="modifier">The speed multiplier. If this is less or equals to 1, this catcher will be non-hyper-dashing state.</param>
        /// <param name="targetPosition">When this catcher crosses this position, this catcher ends hyper-dashing.</param>
        public void SetHyperDashState(double modifier = 1, float targetPosition = -1)
        {
            var wasHyperDashing = HyperDashing;

            if (modifier <= 1 || X == targetPosition)
            {
                hyperDashModifier = 1;
                hyperDashDirection = 0;

                if (wasHyperDashing)
                    runHyperDashStateTransition(false);
            }
            else
            {
                hyperDashModifier = modifier;
                hyperDashDirection = Math.Sign(targetPosition - X);
                hyperDashTargetPosition = targetPosition;

                if (!wasHyperDashing)
                {
                    trails.DisplayEndGlow();
                    runHyperDashStateTransition(true);
                }
            }
        }

        public void UpdatePosition(float position)
        {
            position = Math.Clamp(position, 0, CatchPlayfield.WIDTH);

            if (position == X)
                return;

            Scale = new Vector2(Math.Abs(Scale.X) * (position > X ? 1 : -1), Scale.Y);
            X = position;
        }

        public bool OnPressed(CatchAction action)
        {
            switch (action)
            {
                case CatchAction.MoveLeft:
                    currentDirection--;
                    return true;

                case CatchAction.MoveRight:
                    currentDirection++;
                    return true;

                case CatchAction.Dash:
                    Dashing = true;
                    return true;
            }

            return false;
        }

        public void OnReleased(CatchAction action)
        {
            switch (action)
            {
                case CatchAction.MoveLeft:
                    currentDirection++;
                    break;

                case CatchAction.MoveRight:
                    currentDirection--;
                    break;

                case CatchAction.Dash:
                    Dashing = false;
                    break;
            }
        }

        /// <summary>
        /// Drop any fruit off the plate.
        /// </summary>
        public void Drop() => clearPlate(DroppedObjectAnimation.Drop);

        /// <summary>
        /// Explode all fruit off the plate.
        /// </summary>
        public void Explode() => clearPlate(DroppedObjectAnimation.Explode);

        private void runHyperDashStateTransition(bool hyperDashing)
        {
            updateTrailVisibility();

            if (hyperDashing)
            {
                this.FadeColour(hyperDashColour, HYPER_DASH_TRANSITION_DURATION, Easing.OutQuint);
                this.FadeTo(0.2f, HYPER_DASH_TRANSITION_DURATION, Easing.OutQuint);
            }
            else
            {
                this.FadeColour(Color4.White, HYPER_DASH_TRANSITION_DURATION, Easing.OutQuint);
                this.FadeTo(1f, HYPER_DASH_TRANSITION_DURATION, Easing.OutQuint);
            }
        }

        private void updateTrailVisibility() => trails.DisplayTrail = Dashing || HyperDashing;

        protected override void SkinChanged(ISkinSource skin, bool allowFallback)
        {
            base.SkinChanged(skin, allowFallback);

            hyperDashColour =
                skin.GetConfig<CatchSkinColour, Color4>(CatchSkinColour.HyperDash)?.Value ??
                DEFAULT_HYPER_DASH_COLOUR;

            hyperDashEndGlowColour =
                skin.GetConfig<CatchSkinColour, Color4>(CatchSkinColour.HyperDashAfterImage)?.Value ??
                hyperDashColour;

            trails.HyperDashTrailsColour = hyperDashColour;
            trails.EndGlowSpritesColour = hyperDashEndGlowColour;

            runHyperDashStateTransition(HyperDashing);
        }

        protected override void Update()
        {
            base.Update();

            if (currentDirection == 0) return;

            var direction = Math.Sign(currentDirection);

            var dashModifier = Dashing ? 1 : 0.5;
            var speed = BASE_SPEED * dashModifier * hyperDashModifier;

            UpdatePosition((float)(X + direction * Clock.ElapsedFrameTime * speed));

            // Correct overshooting.
            if ((hyperDashDirection > 0 && hyperDashTargetPosition < X) ||
                (hyperDashDirection < 0 && hyperDashTargetPosition > X))
            {
                X = hyperDashTargetPosition;
                SetHyperDashState();
            }
        }

        private void updateCatcher()
        {
            currentCatcher?.Hide();

            switch (CurrentState)
            {
                default:
                    currentCatcher = catcherIdle;
                    break;

                case CatcherAnimationState.Fail:
                    currentCatcher = catcherFail;
                    break;

                case CatcherAnimationState.Kiai:
                    currentCatcher = catcherKiai;
                    break;
            }

            currentCatcher.Show();
            (currentCatcher.Drawable as IFramedAnimation)?.GotoFrame(0);
        }

        private void updateState(CatcherAnimationState state)
        {
            if (CurrentState == state)
                return;

            CurrentState = state;
            updateCatcher();
        }

        private void placeCaughtObject(DrawablePalpableHasCatchHitObject drawableObject, Vector2 position)
        {
            var caughtObject = getCaughtObject(drawableObject.HitObject);

            if (caughtObject == null) return;

            caughtObject.CopyFrom(drawableObject);
            caughtObject.Anchor = Anchor.TopCentre;
            caughtObject.Position = position;
            caughtObject.Scale /= 2;

            caughtFruitContainer.Add(caughtObject);

            if (!caughtObject.StaysOnPlate)
                removeFromPlate(caughtObject, DroppedObjectAnimation.Explode);
        }

        private Vector2 computePositionInStack(Vector2 position, float displayRadius)
        {
            const float radius_div_2 = CatchHitObject.OBJECT_RADIUS / 2;
            const float allowance = 10;

            while (caughtFruitContainer.Any(f => Vector2Extensions.Distance(f.Position, position) < (displayRadius + radius_div_2) / (allowance / 2)))
            {
                float diff = (displayRadius + radius_div_2) / allowance;

                position.X += (RNG.NextSingle() - 0.5f) * diff * 2;
                position.Y -= RNG.NextSingle() * diff;
            }

            position.X = Math.Clamp(position.X, -CatcherArea.CATCHER_SIZE / 2, CatcherArea.CATCHER_SIZE / 2);

            return position;
        }

        private void addLighting(CatchHitObject hitObject, float x, Color4 colour)
        {
            HitExplosion hitExplosion = hitExplosionPool.Get();
            hitExplosion.HitObject = hitObject;
            hitExplosion.X = x;
            hitExplosion.Scale = new Vector2(hitObject.Scale);
            hitExplosion.ObjectColour = colour;
            hitExplosionContainer.Add(hitExplosion);
        }

        private CaughtObject getCaughtObject(PalpableCatchHitObject source)
        {
            switch (source)
            {
                case Fruit _:
                    return caughtFruitPool.Get();

                case Banana _:
                    return caughtBananaPool.Get();

                case Droplet _:
                    return caughtDropletPool.Get();

                default:
                    return null;
            }
        }

        private CaughtObject getDroppedObject(CaughtObject caughtObject)
        {
            var droppedObject = getCaughtObject(caughtObject.HitObject);

            droppedObject.CopyFrom(caughtObject);
            droppedObject.Anchor = Anchor.TopLeft;
            droppedObject.Position = caughtFruitContainer.ToSpaceOfOtherDrawable(caughtObject.DrawPosition, droppedObjectTarget);

            return droppedObject;
        }

        private void clearPlate(DroppedObjectAnimation animation)
        {
            var caughtObjects = caughtFruitContainer.Children.ToArray();
            var droppedObjects = caughtObjects.Select(getDroppedObject).ToArray();

            caughtFruitContainer.Clear(false);

            droppedObjectTarget.AddRange(droppedObjects);

            foreach (var droppedObject in droppedObjects)
                applyDropAnimation(droppedObject, animation);
        }

        private void removeFromPlate(CaughtObject caughtObject, DroppedObjectAnimation animation)
        {
            var droppedObject = getDroppedObject(caughtObject);

            if (!caughtFruitContainer.Remove(caughtObject))
                throw new InvalidOperationException("Can only drop a caught object on the plate");

            droppedObjectTarget.Add(droppedObject);

            applyDropAnimation(droppedObject, animation);
        }

        private void applyDropAnimation(Drawable d, DroppedObjectAnimation animation)
        {
            switch (animation)
            {
                case DroppedObjectAnimation.Drop:
                    d.MoveToY(d.Y + 75, 750, Easing.InSine);
                    d.FadeOut(750);
                    break;

                case DroppedObjectAnimation.Explode:
                    var originalX = droppedObjectTarget.ToSpaceOfOtherDrawable(d.DrawPosition, caughtFruitContainer).X * Scale.X;
                    d.MoveToY(d.Y - 50, 250, Easing.OutSine).Then().MoveToY(d.Y + 50, 500, Easing.InSine);
                    d.MoveToX(d.X + originalX * 6, 1000);
                    d.FadeOut(750);
                    break;
            }

            d.Expire();
        }

        private enum DroppedObjectAnimation
        {
            Drop,
            Explode
        }
    }
}