using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using UnityEngine;
using UnityEngine.EventSystems;
using UnityEngine.UI;

namespace RimWorldAnimationStudio
{
    public class KeyframeSlider : Slider, IPointerClickHandler, IBeginDragHandler, IEndDragHandler
    {
        public int keyframeID;
        public AnimationTimeline timeline;
        public Transform ghostSliders;
        public Slider ghostSliderPrefab;
        public Image handleImage;
        public GameObject soundIcon;
        public int maxGhosts = 4;

        public KeyframeSlider linkedSlider;
        public PawnKeyframe pivotKeyframe;
        public int linkedOffset;

        private PawnAnimationClip clip { get { return Workspace.GetPawnAnimationClip(actorID); } }
        private PawnKeyframe keyframe { get { return Workspace.GetPawnKeyframe(keyframeID); } }

        private int actorID;
        private float dragTimeStart = -1f;
        private int dragTickStart = -1;

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

            onValueChanged.AddListener(delegate (float value) { OnValueChanged(); });
        }

        public void Initialize(AnimationTimeline timeline, int actorID, int keyframeID)
        {
            this.timeline = timeline;
            this.actorID = actorID;
            this.keyframeID = keyframeID;

            maxValue = Workspace.StageWindowSize;
            value = keyframe.atTick.Value;
        }

        public void OnValueChanged()
        {
            keyframe.atTick = (int)value;
            clip.BuildSimpleCurves();

            timeline.InitiateUpdateOfGhostFrames();
        }  

        // Ghost sliders are non-interactable slider handle
        public void UpdateGhostFrames()
        {
            if (maxGhosts == 0)
            { return; }

            int requiredGhosts = GetGhostFramesRequired();
            int currentGhostCount = ghostSliders.childCount;

            for (int i = 0; i < Mathf.Max(requiredGhosts, currentGhostCount); i++)
            {
                if (clip == null || keyframe == null) continue;

                int targetTick = (int)(i * clip.duration + keyframe.atTick);

                if (ghostSliders.childCount <= i)
                { Instantiate(ghostSliderPrefab, ghostSliders); }

                GameObject ghostSliderObject = ghostSliders.GetChild(i).gameObject;
                ghostSliderObject.SetActive(i < requiredGhosts);

                Slider ghostSlider = ghostSliderObject.GetComponent<Slider>();
                ghostSlider.maxValue = Workspace.StageWindowSize;
                ghostSlider.value = targetTick;
 
                if (targetTick > ghostSlider.maxValue) 
                { ghostSlider.gameObject.SetActive(false); }
            }
        }

        public int GetGhostFramesRequired()
        {
            if (Workspace.animationDef.AnimationStages[Workspace.StageID].IsLooping == false)
            { return 0; }

            if (clip.duration <= 1)
            { return 0; }

            return Math.Min(Mathf.CeilToInt((float)Workspace.StageWindowSize / clip.duration), maxGhosts);
        }

        public void OnPointerClick(PointerEventData eventData)
        {
            Workspace.ActorID = actorID;
            
            if (Input.GetKey(KeyCode.LeftControl) || Input.GetKey(KeyCode.LeftCommand))
            { Workspace.keyframeID.Add(keyframeID); }

            else if (Workspace.keyframeID.NullOrEmpty() || Workspace.keyframeID.Contains(keyframeID) == false)
            { Workspace.keyframeID = new List<int> { keyframeID }; }

            if (eventData.clickCount >= 2)
            { Workspace.StageTick = keyframe.atTick.Value; }
        }

        public void OnBeginDrag(PointerEventData eventData)
        {
            Workspace.ActorID = actorID;
            dragTimeStart = Time.unscaledTime;
            dragTickStart = keyframe.atTick.Value;

            if (Workspace.keyframeID.NullOrEmpty() || Workspace.keyframeID.Contains(keyframeID) == false)
            { Workspace.keyframeID = new List<int> { keyframeID }; }

            List<PawnKeyframe> selectedKeyframes = Workspace.GetPawnKeyframesByID(Workspace.keyframeID).Except(new List<PawnKeyframe>() { keyframe })?.ToList();

            // Link other selected keyframes to the movement of this one
            if (selectedKeyframes.NotNullOrEmpty())
            {
                pivotKeyframe = keyframe.atTick <= selectedKeyframes.Min(x => x.atTick) ?
                    selectedKeyframes.FirstOrDefault(x => x.atTick >= selectedKeyframes.Max(y => y.atTick)) :
                    selectedKeyframes.FirstOrDefault(x => x.atTick <= selectedKeyframes.Min(y => y.atTick)); 

                foreach (PawnKeyframe selectedKeyframe in selectedKeyframes)
                {
                    KeyframeSlider unlinkedSlider = selectedKeyframe.GetKeyframeSlider();

                    if (unlinkedSlider != null)
                    {
                        if (Workspace.stretchKeyframes && unlinkedSlider.keyframe.atTick == pivotKeyframe.atTick) continue;

                        unlinkedSlider.linkedSlider = this;
                        unlinkedSlider.linkedOffset = unlinkedSlider.keyframe.atTick.Value - keyframe.atTick.Value;
                    }
                }
            }
        }

        public override void OnDrag(PointerEventData eventData)
        {
            Workspace.ActorID = actorID;

            // The first keyframe can't be moved
            if (keyframe.atTick == Constants.minTick)
            { value = Constants.minTick; return; }

            // Sticky drag
            if (Time.unscaledTime - dragTimeStart < 0.05f) return;

            interactable = true;
            base.OnDrag(eventData);

            // Snap to nearest keyframe (on another timeline)
            int targetTick = Workspace.FindClosestKeyFrameAtTick(keyframe.atTick.Value, Mathf.CeilToInt(Workspace.StageWindowSize * 0.01f), actorID);
            if (Input.GetKey(KeyCode.LeftShift) && Workspace.DoesPawnKeyframeExistAtTick(Workspace.StageID, actorID, targetTick) == false)
            { value = (float)targetTick; }

            // Prevent other frames from being moved to the first keyframe
            if (value == Constants.minTick)
            { value = Constants.minTick + 1; }
        }

        public void OnEndDrag(PointerEventData eventData)
        {
            if (keyframe.atTick == Constants.minTick)
            { value = Constants.minTick; return; }

            List<PawnKeyframe> keyframesToCheck = Workspace.GetAllPawnKeyframesAtTick(actorID, keyframe.atTick.Value);
            if (keyframesToCheck.NotNullOrEmpty())
            {
                foreach (PawnKeyframe _keyframe in keyframesToCheck)
                {
                    if (_keyframe != keyframe)
                    { Workspace.GetAnimationClipThatOwnsKeyframe(_keyframe.keyframeID).RemovePawnKeyframe(_keyframe.keyframeID); }
                }
            }

            foreach (Selectable selectable in Selectable.allSelectablesArray)
            {
                if (selectable is KeyframeSlider)
                {
                    KeyframeSlider linkedSlider = selectable.GetComponent<KeyframeSlider>();
                    PawnKeyframe linkedKeyframe = linkedSlider.keyframe;

                    if (linkedSlider.linkedSlider != null)
                    {
                        keyframesToCheck = Workspace.GetAllPawnKeyframesAtTick(actorID, linkedKeyframe.atTick.Value);

                        if (keyframesToCheck.NotNullOrEmpty() && keyframesToCheck.Count > 1)
                        {
                            foreach (PawnKeyframe _keyframe in keyframesToCheck)
                            {
                                if (_keyframe.keyframeID != linkedKeyframe.keyframeID)
                                { Workspace.GetAnimationClipThatOwnsKeyframe(_keyframe.keyframeID).RemovePawnKeyframe(_keyframe.keyframeID); }
                            }
                        }
                    }

                    linkedSlider.linkedSlider = null;
                    linkedSlider.pivotKeyframe = null;
                }
            }

            interactable = false;

            Workspace.RecordEvent("Keyframe move");
        }

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

            if (keyframe == null) return;

            // Update outdated values
            if (Workspace.keyframeID.NullOrEmpty() || Workspace.keyframeID.Contains(keyframeID) == false)
            { linkedSlider = null; }

            else if (Workspace.stretchKeyframes && linkedSlider != null)
            { value = Mathf.CeilToInt(linkedSlider.keyframe.atTick.Value + linkedOffset * linkedSlider.ScaledOffsetFromPivot()); }

            else if (Workspace.stretchKeyframes == false && linkedSlider != null)
            { value = Mathf.Clamp(linkedSlider.keyframe.atTick.Value + linkedOffset, Constants.minTick + 1, Workspace.StageWindowSize); }

            else if (keyframe.atTick.Value != value)
            { value = keyframe.atTick.Value; }

            // Update key color
            if (keyframe.atTick.HasValue && Workspace.keyframeID.Contains(keyframeID) && Workspace.StageTick == keyframe.atTick.Value)
            { handleImage.color = Constants.ColorPurple; }

            else if (Workspace.keyframeID.Contains(keyframeID))
            { handleImage.color = Constants.ColorCyan; }

            else if (Workspace.StageTick == keyframe.atTick.Value)
            { handleImage.color = Constants.ColorPink; }

            else
            { handleImage.color = Constants.ColorGrey; }

            // Show sound symbol
            string soundDef = Workspace.GetPawnKeyframe(keyframeID)?.SoundEffect;
            soundIcon.SetActive(soundDef != null && soundDef != "" && soundDef != "None");
        }

        public float ScaledOffsetFromPivot()
        {
            if (dragTickStart == pivotKeyframe.atTick.Value) return 0f;

            return (float)(keyframe.atTick.Value - pivotKeyframe.atTick.Value) / (dragTickStart - pivotKeyframe.atTick.Value);
        }

        public bool IsPivotKeyframe(PawnKeyframe otherKeyframe)
        {
            return pivotKeyframe == otherKeyframe;
        }
    }
}