#nullable enable

using System;
using TMPro;
using UnityEngine;
using UnityEngine.EventSystems;
using UnityEngine.UI;

namespace ReplacedPerson.Runtime
{
    [RequireComponent(typeof(RectTransform), typeof(Button))]
    public sealed class ReplacedCardDragHandler : MonoBehaviour, IBeginDragHandler, IDragHandler, IEndDragHandler
    {
        private Canvas? _canvas;
        private RectTransform? _ghost;
        private ReplacedCardMotion? _motion;
        private Action<Vector2>? _dropAction;
        private Vector2 _dragStart;
        private bool _hasDragStart;

        public void Configure(Action<Vector2> dropAction)
        {
            _dropAction = dropAction;
        }

        public void OnBeginDrag(PointerEventData eventData)
        {
            CleanupGhost();
            _dragStart = eventData.position;
            _hasDragStart = true;
            _canvas = GetComponentInParent<Canvas>()?.rootCanvas;
            if (_canvas == null) return;
            _motion = GetComponent<ReplacedCardMotion>();
            _motion?.SetDragging(true);
            _ghost = CreateGhost(_canvas.transform);
            UpdateGhostPosition(eventData);
        }

        public void OnDrag(PointerEventData eventData)
        {
            UpdateGhostPosition(eventData);
        }

        public void OnEndDrag(PointerEventData eventData)
        {
            var moved = _hasDragStart && (eventData.position - _dragStart).sqrMagnitude >= 100f;
            _motion?.SetDragging(false);
            _motion = null;
            CleanupGhost();
            _hasDragStart = false;
            if (moved && _dropAction != null) _dropAction(eventData.position);
            else GetComponent<Button>().onClick.Invoke();
        }

        private RectTransform CreateGhost(Transform canvasRoot)
        {
            var sourceRect = (RectTransform)transform;
            var sourceImage = GetComponent<Image>();
            var sourceLabel = transform.Find("Label")?.GetComponent<TMP_Text>();
            var ghostObject = new GameObject("CardDragGhost", typeof(RectTransform), typeof(CanvasRenderer), typeof(Image), typeof(CanvasGroup));
            var ghostRect = ghostObject.GetComponent<RectTransform>();
            ghostRect.SetParent(canvasRoot, false);
            ghostRect.anchorMin = ghostRect.anchorMax = new Vector2(.5f, .5f);
            ghostRect.pivot = sourceRect.pivot;
            ghostRect.sizeDelta = sourceRect.rect.size;
            ghostRect.localScale = Vector3.one * 1.06f;
            ghostRect.SetAsLastSibling();

            var ghostImage = ghostObject.GetComponent<Image>();
            ghostImage.sprite = sourceImage.sprite;
            ghostImage.type = sourceImage.type;
            ghostImage.color = sourceImage.color;
            ghostImage.material = sourceImage.material;
            ghostImage.raycastTarget = false;
            var group = ghostObject.GetComponent<CanvasGroup>();
            group.alpha = .94f;
            group.blocksRaycasts = false;
            group.interactable = false;

            if (sourceLabel != null)
            {
                var labelObject = new GameObject("Label", typeof(RectTransform), typeof(CanvasRenderer), typeof(TextMeshProUGUI));
                var labelRect = labelObject.GetComponent<RectTransform>();
                labelRect.SetParent(ghostRect, false);
                labelRect.anchorMin = Vector2.zero;
                labelRect.anchorMax = Vector2.one;
                labelRect.offsetMin = new Vector2(8, 4);
                labelRect.offsetMax = new Vector2(-8, -4);
                var label = labelObject.GetComponent<TextMeshProUGUI>();
                label.font = sourceLabel.font;
                label.fontSize = sourceLabel.fontSize;
                label.alignment = sourceLabel.alignment;
                label.color = sourceLabel.color;
                label.text = sourceLabel.text;
                label.enableWordWrapping = sourceLabel.enableWordWrapping;
                label.raycastTarget = false;
            }
            return ghostRect;
        }

        private void UpdateGhostPosition(PointerEventData eventData)
        {
            if (_ghost == null || _canvas == null) return;
            var canvasRect = (RectTransform)_canvas.transform;
            var camera = _canvas.renderMode == RenderMode.ScreenSpaceOverlay ? null : _canvas.worldCamera;
            if (RectTransformUtility.ScreenPointToLocalPointInRectangle(canvasRect, eventData.position, camera, out var localPoint))
                _ghost.anchoredPosition = localPoint;
        }

        private void OnDisable()
        {
            _motion?.SetDragging(false);
            _motion = null;
            _hasDragStart = false;
            CleanupGhost();
        }

        private void CleanupGhost()
        {
            if (_ghost != null) Destroy(_ghost.gameObject);
            _ghost = null;
            _canvas = null;
        }
    }
}