using UnityEditor;
using UnityEngine;

// UIMask 材质面板的"下拉框 -> 隐藏属性"绘制器基类。
// ShaderLab 的 Blend / Cull 只接受数字属性，没法用枚举直接切换，
// 所以由绘制器把下拉框的选项写进隐藏属性。
// 每次绘制面板都会同步一次，所以从其它 shader（例如 URP/Lit 也有同名的
// _SrcBlend / _DstBlend / _Cull）切过来的材质会被自动纠正。
// 注意：attribute 的名字必须是子类的简单类名，Unity 按类名查找绘制器。
public abstract class UIMaskEnumDrawer : MaterialPropertyDrawer
{
    protected abstract string[] Options { get; }

    // 把下拉框当前选项同步到材质上的隐藏属性
    protected abstract void Apply(MaterialEditor editor, int index);

    public override void OnGUI(Rect position, MaterialProperty prop, string label, MaterialEditor editor)
    {
        EditorGUI.BeginChangeCheck();
        int index = Mathf.Clamp(Mathf.RoundToInt(prop.floatValue), 0, Options.Length - 1);
        index = EditorGUI.Popup(position, label, index, Options);
        if (EditorGUI.EndChangeCheck())
        {
            prop.floatValue = index;
        }

        Apply(editor, index);
    }

    public override float GetPropertyHeight(MaterialProperty prop, string label, MaterialEditor editor)
    {
        return EditorGUIUtility.singleLineHeight;
    }

    protected void SetValue(MaterialEditor editor, string propertyName, float value)
    {
        foreach (Object target in editor.targets)
        {
            var material = target as Material;
            if (material == null || !material.HasProperty(propertyName))
            {
                continue;
            }

            if (!Mathf.Approximately(material.GetFloat(propertyName), value))
            {
                material.SetFloat(propertyName, value);
            }
        }
    }
}

// 混合模式：加色 / 普通混合
// 数值对应 UnityEngine.Rendering.BlendMode：SrcAlpha=5, One=1, OneMinusSrcAlpha=10
public class UIMaskBlendMode : UIMaskEnumDrawer
{
    private static readonly string[] Items = { "Additive", "AlphaBlend" };

    protected override string[] Options => Items;

    protected override void Apply(MaterialEditor editor, int index)
    {
        SetValue(editor, "_SrcBlend", (float)UnityEngine.Rendering.BlendMode.SrcAlpha);
        SetValue(editor, "_DstBlend", index == 0
            ? (float)UnityEngine.Rendering.BlendMode.One
            : (float)UnityEngine.Rendering.BlendMode.OneMinusSrcAlpha);
    }
}

// 渲染面：只渲染前面 / 只渲染后面 / 双面
// ShaderLab 的 Cull 取值：Off=0（双面）、Front=1（剔除正面，即只渲染后面）、Back=2（剔除背面，即只渲染前面）
public class UIMaskRenderFace : UIMaskEnumDrawer
{
    private const float CullOff = 0f;
    private const float CullFront = 1f;
    private const float CullBack = 2f;

    private static readonly string[] Items = { "前面", "背面", "双面" };

    protected override string[] Options => Items;

    protected override void Apply(MaterialEditor editor, int index)
    {
        float cull = index == 0 ? CullBack : (index == 1 ? CullFront : CullOff);
        SetValue(editor, "_Cull", cull);
    }
}

// 贴图通道：R / G / B / A（值直接被 shader 采样时使用，不需要写隐藏属性）
// 默认 A（index = 3）
public class UIMaskChannel : UIMaskEnumDrawer
{
    private static readonly string[] Items = { "R 通道", "G 通道", "B 通道", "A 通道" };

    protected override string[] Options => Items;

    protected override void Apply(MaterialEditor editor, int index)
    {
        // 下拉框的值本身就是要采样的通道号，无需同步到别的属性
    }
}