using UnityEngine;
using UnityEngine.EventSystems;
using UnityEngine.UI;

/// <summary>
/// 底部英雄卡片的拖拽：拖到网格格位上放置英雄。
/// 吸附与放置由 FormationManager 负责，卡片只负责拖动表现和回调。
/// </summary>
[RequireComponent(typeof(CanvasGroup))]
public class FormationCardDrag : MonoBehaviour, IBeginDragHandler, IDragHandler, IEndDragHandler
{
    [Header("界面引用")]
    public Image background;
    public Image icon;
    public Text nameText;

    [HideInInspector] public FormationManager manager;
    [HideInInspector] public int heroIndex;

    private RectTransform rectTransform;
    private CanvasGroup canvasGroup;
    private Vector2 homePosition;

    private static readonly Color NormalColor = new Color(0.15f, 0.15f, 0.2f, 0.92f);
    private static readonly Color PlacedColor = new Color(0.18f, 0.18f, 0.22f, 0.45f);

    private void Awake()
    {
        rectTransform = GetComponent<RectTransform>();
        canvasGroup = GetComponent<CanvasGroup>();
        homePosition = rectTransform.anchoredPosition;
    }

    /// <summary>填入名字与头像。</summary>
    public void SetContent(string displayName, Sprite iconSprite)
    {
        if (nameText != null) nameText.text = displayName;
        if (icon != null)
        {
            if (iconSprite != null)
            {
                icon.sprite = iconSprite;
                icon.preserveAspect = true;
                icon.color = Color.white;
            }
            else
            {
                icon.color = new Color(0.4f, 0.4f, 0.45f, 1f);
            }
        }
    }

    /// <summary>已放置的卡片置灰并禁止再次拖拽。</summary>
    public void SetPlaced(bool isPlaced)
    {
        if (background != null) background.color = isPlaced ? PlacedColor : NormalColor;
        canvasGroup.alpha = isPlaced ? 0.55f : 1f;
    }

    public void OnBeginDrag(PointerEventData eventData)
    {
        if (manager == null || !manager.CanDrag(heroIndex))
        {
            return;
        }

        canvasGroup.blocksRaycasts = false;
        rectTransform.position = eventData.position;
        manager.OnCardDragStart(heroIndex);
    }

    public void OnDrag(PointerEventData eventData)
    {
        if (manager == null || !manager.CanDrag(heroIndex))
        {
            return;
        }

        rectTransform.position = eventData.position;
        manager.OnCardDragging(heroIndex, eventData.position);
    }

    public void OnEndDrag(PointerEventData eventData)
    {
        canvasGroup.blocksRaycasts = true;

        if (manager == null || !manager.CanDrag(heroIndex))
        {
            rectTransform.anchoredPosition = homePosition;
            return;
        }

        rectTransform.anchoredPosition = homePosition;
        manager.OnCardDragEnd(heroIndex, eventData.position);
    }
}