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

/// <summary>
/// 英雄卡片拖动组件（布阵阶段使用）。
/// 拖动时在场景里生成一个半透明的英雄"幽灵"跟随指针，并吸附到最近的部署格位；
/// 松手后把该卡对应的英雄登记到格位上，卡片进入"已使用"状态。
/// </summary>
public class HeroCardDrag : MonoBehaviour, IBeginDragHandler, IDragHandler, IEndDragHandler
{
    [Header("配置（由 DefenseGameFlowController 注入）")]
    public int cardIndex;               // 卡片序号，0 起
    public GameObject heroPrefab;       // 对应英雄 Prefab
    public CharacterData characterData; // 角色数据

    [Header("幽灵外观")]
    [Range(0.1f, 1f)] public float ghostAlpha = 0.55f;

    private Canvas canvas;
    private CanvasGroup canvasGroup;
    private GameObject ghost;
    private Material ghostHiddenMaterial;

    private bool dragging;
    private int currentCell = -1;

    private const float PlacedCardAlpha = 0.35f;

    private void Awake()
    {
        canvas = GetComponentInParent<Canvas>();
        canvasGroup = GetComponent<CanvasGroup>();
        if (canvasGroup == null)
        {
            canvasGroup = gameObject.AddComponent<CanvasGroup>();
        }
    }

    /// <summary>由流程控制器注入卡片配置。</summary>
    public void Setup(int index, GameObject prefab, CharacterData data)
    {
        cardIndex = index;
        heroPrefab = prefab;
        characterData = data;
        SetPlaced(false);
    }

    /// <summary>标记该卡是否已经放下去了（已放置的卡片变暗且不能再拖）。</summary>
    public void SetPlaced(bool placed)
    {
        if (canvasGroup != null)
        {
            canvasGroup.alpha = placed ? PlacedCardAlpha : 1f;
        }
    }

    public void OnBeginDrag(PointerEventData eventData)
    {
        var flow = DefenseGameFlowController.Instance;
        if (flow == null || !flow.IsDeployPhase) return;
        if (flow.IsCardPlaced(cardIndex)) return;   // 已经放置过了
        if (heroPrefab == null) return;

        dragging = true;
        currentCell = -1;

        if (canvasGroup != null)
        {
            canvasGroup.alpha = 0.5f;
            canvasGroup.blocksRaycasts = false;
        }

        CreateGhost();
        FollowPointer(eventData.position);
    }

    public void OnDrag(PointerEventData eventData)
    {
        if (!dragging) return;
        FollowPointer(eventData.position);
    }

    public void OnEndDrag(PointerEventData eventData)
    {
        if (!dragging) return;
        dragging = false;

        if (canvasGroup != null)
        {
            canvasGroup.alpha = 1f;
            canvasGroup.blocksRaycasts = true;
        }

        if (DeployHighlight.Instance != null) DeployHighlight.Instance.Hide();

        int cell = currentCell;
        currentCell = -1;

        DestroyGhost();

        if (cell >= 0)
        {
            var flow = DefenseGameFlowController.Instance;
            if (flow != null && flow.PlaceHeroFromCard(cardIndex, cell))
            {
                SetPlaced(true);
            }
        }
    }

    // ── 幽灵 ────────────────────────────────────────────────

    private void CreateGhost()
    {
        ghost = Instantiate(heroPrefab);
        ghost.name = "Ghost_" + heroPrefab.name;

        // 只保留外观：关掉所有逻辑组件与碰撞体
        foreach (var behaviour in ghost.GetComponentsInChildren<Behaviour>(true))
        {
            if (behaviour is Animator) continue;   // 保留 Animator 让它做待机动作
            behaviour.enabled = false;
        }
        foreach (var collider in ghost.GetComponentsInChildren<Collider>(true))
        {
            collider.enabled = false;
        }
        foreach (var rb in ghost.GetComponentsInChildren<Rigidbody>(true))
        {
            rb.isKinematic = true;
            rb.detectCollisions = false;
        }

        // Animator 不能带动根位移，否则幽灵会自己漂走
        foreach (var animator in ghost.GetComponentsInChildren<Animator>(true))
        {
            animator.applyRootMotion = false;
        }

        // 血条 UI 是 WorldHealthBar.Awake 生成的，幽灵不需要
        var healthBar = ghost.transform.Find("WorldHealthBar");
        if (healthBar != null)
        {
            Destroy(healthBar.gameObject);
        }

        BuildGhostMaterials();
    }

    private void BuildGhostMaterials()
    {
        if (ghostHiddenMaterial == null)
        {
            var hiddenShader = Shader.Find("Sprites/Default") ?? Shader.Find("Unlit/Color");
            ghostHiddenMaterial = new Material(hiddenShader);
            ghostHiddenMaterial.name = "GhostHidden";
            ghostHiddenMaterial.color = new Color(1f, 1f, 1f, 0f);
        }

        var bodyShader = Shader.Find("Standard");

        foreach (var renderer in ghost.GetComponentsInChildren<Renderer>(true))
        {
            var source = renderer.sharedMaterials;
            var result = new Material[source.Length];

            for (int i = 0; i < source.Length; i++)
            {
                // 第 0 个材质是本体，做成半透明；其余（描边等附加材质）隐藏掉
                if (i == 0 && source[i] != null && bodyShader != null)
                {
                    result[i] = MakeTransparent(source[i], ghostAlpha, bodyShader);
                }
                else
                {
                    result[i] = ghostHiddenMaterial;
                }
            }

            renderer.sharedMaterials = result;
            renderer.shadowCastingMode = UnityEngine.Rendering.ShadowCastingMode.Off;
        }
    }

    private static Material MakeTransparent(Material source, float alpha, Shader standard)
    {
        var mat = new Material(source);
        mat.name = source.name + "_Ghost";

        // 统一用 Standard 的透明混合模式，保证任何贴图都能变成半透明
        if (mat.shader != standard)
        {
            var mainTex = mat.HasProperty("_MainTex") ? mat.GetTexture("_MainTex") : null;
            var color = mat.HasProperty("_Color") ? mat.GetColor("_Color") : Color.white;
            mat.shader = standard;
            if (mainTex != null) mat.SetTexture("_MainTex", mainTex);
            mat.SetColor("_Color", color);
        }

        if (mat.HasProperty("_Mode"))
        {
            mat.SetFloat("_Mode", 3f); // Transparent
            mat.SetInt("_SrcBlend", (int)UnityEngine.Rendering.BlendMode.SrcAlpha);
            mat.SetInt("_DstBlend", (int)UnityEngine.Rendering.BlendMode.OneMinusSrcAlpha);
            mat.SetInt("_ZWrite", 0);
            mat.DisableKeyword("_ALPHATEST_ON");
            mat.EnableKeyword("_ALPHABLEND_ON");
            mat.DisableKeyword("_ALPHAPREMULTIPLY_ON");
            mat.renderQueue = 3000;
        }

        if (mat.HasProperty("_Color"))
        {
            var c = mat.GetColor("_Color");
            c.a = alpha;
            mat.SetColor("_Color", c);
        }

        return mat;
    }

    private void FollowPointer(Vector2 screenPosition)
    {
        if (ghost == null) return;

        var cam = Camera.main;
        if (cam == null) return;

        var ray = cam.ScreenPointToRay(screenPosition);
        var ground = new Plane(Vector3.up, new Vector3(0f, DeployGrid.UnitY, 0f));

        if (!ground.Raycast(ray, out float distance))
        {
            return;
        }

        Vector3 world = ray.GetPoint(distance);
        int cell = DeployGrid.SnapToCellClamped(world);

        if (cell == currentCell) return;
        currentCell = cell;

        var flow = DefenseGameFlowController.Instance;
        bool blocked = cell < 0 || (flow != null && flow.IsCellOccupied(cell));

        if (cell >= 0)
        {
            ghost.transform.position = DeployGrid.CellPosition(cell);
            if (DeployHighlight.Instance != null) DeployHighlight.Instance.Show(cell, blocked);
        }
        else
        {
            // 没吸附到格位：幽灵跟着指针但压暗提示不可放置
            ghost.transform.position = new Vector3(world.x, DeployGrid.UnitY, world.z);
            if (DeployHighlight.Instance != null) DeployHighlight.Instance.Hide();
        }
    }

    private void DestroyGhost()
    {
        if (ghost == null) return;

        foreach (var renderer in ghost.GetComponentsInChildren<Renderer>(true))
        {
            if (renderer.sharedMaterials == null) continue;
            foreach (var mat in renderer.sharedMaterials)
            {
                if (mat != null && mat != ghostHiddenMaterial) Destroy(mat);
            }
        }

        Destroy(ghost);
        ghost = null;
    }

    private void OnDisable()
    {
        if (dragging)
        {
            dragging = false;
            if (canvasGroup != null)
            {
                canvasGroup.alpha = 1f;
                canvasGroup.blocksRaycasts = true;
            }
            if (DeployHighlight.Instance != null) DeployHighlight.Instance.Hide();
        }
        DestroyGhost();
    }
}