using UnityEngine;
using UnityEngine.UI;

public class ScratchMask : MonoBehaviour
{
    public RawImage maskImage;       // 黑白图
    public Texture2D brushTex;       // 笔刷纹理
    Camera uiCamera;          // Canvas 摄像机
    public int rtResolution = 1024;  // 遮罩精度
    private Texture2D readTex;       // 遮罩纹理
    bool HasRevealed = false;
    public float revealThreshold = 0.8f; // 擦除面积阈值 (30%)

    private RenderTexture maskRT;
    private Material mat;

    void Start()
    {
        // 创建遮罩 RT
        maskRT = new RenderTexture(rtResolution, rtResolution, 0);
        maskRT.Create();
        uiCamera = Camera.main;
        // 填满为白色（遮罩默认不透明）
        RenderTexture.active = maskRT;
        GL.Clear(true, true, Color.white);
        RenderTexture.active = null;

        // 获取材质并设置遮罩纹理
        mat = maskImage.material;
        mat.SetTexture("_MaskTex", maskRT);
    }

    void Update()
    {
        if (Input.GetMouseButton(0))
        {
            Vector2 localPos;
            RectTransformUtility.ScreenPointToLocalPointInRectangle(
                maskImage.rectTransform,
                Input.mousePosition,
                uiCamera,
                out localPos
            );

            Vector2 uv = new Vector2(
                (localPos.x + maskImage.rectTransform.rect.width / 2) / maskImage.rectTransform.rect.width,
                (localPos.y + maskImage.rectTransform.rect.height / 2) / maskImage.rectTransform.rect.height
            );

            DrawBrush(uv);
            CheckRevealProgress();
        }
    }

    void DrawBrush(Vector2 uv)
    {
        // int px = (int)(uv.x * maskRT.width);
        // int py = (int)(uv.y * maskRT.height);
        int px = (int)(uv.x * maskRT.width);
        // 反转 Y：
        int py = maskRT.height - (int)(uv.y * maskRT.height);

        RenderTexture.active = maskRT;
        GL.PushMatrix();
        GL.LoadPixelMatrix(0, maskRT.width, maskRT.height, 0);
        // GL.LoadPixelMatrix(0, maskRT.width, 0, maskRT.height);

        Graphics.DrawTexture(
            new Rect(px - brushTex.width / 2, py - brushTex.height / 2, brushTex.width, brushTex.height),
            brushTex
        );

        GL.PopMatrix();
        RenderTexture.active = null;
    }

    void CheckRevealProgress()
    {
        if (HasRevealed) return;

        RenderTexture.active = maskRT;

        if (readTex == null)
            readTex = new Texture2D(maskRT.width, maskRT.height, TextureFormat.RGB24, false);

        readTex.ReadPixels(new Rect(0, 0, maskRT.width, maskRT.height), 0, 0);
        readTex.Apply();

        int clearCount = 0;
        Color[] pixels = readTex.GetPixels();

        foreach (var pixel in pixels)
        {
            if (pixel.r < 0.5f) // 黑色（已擦除）
                clearCount++;
        }

        float percent = clearCount / (float)pixels.Length;

        if (percent > revealThreshold)
        {
            Debug.Log("✔️ 已擦除足够区域，显示彩色图！");
            RevealColorImage();
            HasRevealed = true;
        }

        RenderTexture.active = null;
    }
    
    void RevealColorImage()
    {
        maskImage.gameObject.SetActive(false); // 隐藏黑白图
        // 或者：maskImage.color = new Color(1,1,1,0);
    }
}