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：Additive / Alpha / Alpha Premultiplied / Opaque
// 数值对应 UnityEngine.Rendering.BlendMode：SrcAlpha=5, One=1, OneMinusSrcAlpha=10, Zero=0
// Opaque 会同时打开 ZWrite（不透明需要写深度），其余模式 ZWrite = 0
public class UIMaskBlendMode : UIMaskEnumDrawer
{
    private static readonly string[] Items = { "Additive", "Alpha", "Alpha Premultiplied", "Opaque" };

    protected override string[] Options => Items;

    protected override void Apply(MaterialEditor editor, int index)
    {
        const float srcAlpha = (float)UnityEngine.Rendering.BlendMode.SrcAlpha;                 // 5
        const float one = (float)UnityEngine.Rendering.BlendMode.One;                           // 1
        const float oneMinusSrcAlpha = (float)UnityEngine.Rendering.BlendMode.OneMinusSrcAlpha; // 10
        const float zero = (float)UnityEngine.Rendering.BlendMode.Zero;                         // 0

        switch (index)
        {
            case 1: // Alpha：标准透明混合
                SetValue(editor, "_SrcBlend", srcAlpha);
                SetValue(editor, "_DstBlend", oneMinusSrcAlpha);
                SetValue(editor, "_ZWrite", 0f);
                break;

            case 2: // Alpha Premultiplied：颜色已预乘 alpha，源因子用 One
                SetValue(editor, "_SrcBlend", one);
                SetValue(editor, "_DstBlend", oneMinusSrcAlpha);
                SetValue(editor, "_ZWrite", 0f);
                break;

            case 3: // Opaque：不混合 + 写深度
                SetValue(editor, "_SrcBlend", one);
                SetValue(editor, "_DstBlend", zero);
                SetValue(editor, "_ZWrite", 1f);
                break;

            default: // Additive：SrcAlpha + One
                SetValue(editor, "_SrcBlend", srcAlpha);
                SetValue(editor, "_DstBlend", one);
                SetValue(editor, "_ZWrite", 0f);
                break;
        }
    }
}

// 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
    }
}

// 通用模块：粒子自定义数据通道下拉框（shader 里写 [CustomDataChannel]）
// 选项 9 项：null / Custom1.xyzw / Custom2.xyzw；值 0=null，1~4=Custom1，5~8=Custom2
// 右侧会提示该通道是否已被同一材质上的其它参数占用
//（约定：属性名里含 "CustomChannel" 的都会被统计，以后新增参数只要按这个命名即可自动纳入）
// shader 侧配套函数：CustomDataChannelValue(custom1, custom2, channel) → 取对应通道的值
public class CustomDataChannel : MaterialPropertyDrawer
{
    private static readonly string[] Items =
    {
        "null",
        "Custom1.x", "Custom1.y", "Custom1.z", "Custom1.w",
        "Custom2.x", "Custom2.y", "Custom2.z", "Custom2.w"
    };

    private const float HintWidth = 150f;

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

    public override void OnGUI(Rect position, MaterialProperty prop, string label, MaterialEditor editor)
    {
        Rect popupRect = new Rect(position.x, position.y, Mathf.Max(60f, position.width - HintWidth - 4f), position.height);
        Rect hintRect = new Rect(position.xMax - HintWidth, position.y, HintWidth, position.height);

        int index = Mathf.Clamp(Mathf.RoundToInt(prop.floatValue), 0, Items.Length - 1);

        EditorGUI.BeginChangeCheck();
        EditorGUI.showMixedValue = prop.hasMixedValue;
        index = EditorGUI.Popup(popupRect, label, index, Items);
        EditorGUI.showMixedValue = false;
        if (EditorGUI.EndChangeCheck())
        {
            prop.floatValue = index;
        }

        bool occupied;
        string hint = DescribeOccupation(editor, prop, index, out occupied);
        var hintContent = new GUIContent(hint, "数据来自粒子系统的「自定义数据」模块；"
            + "还需要在粒子渲染器的「自定义顶点流」里按 UV、Custom1.xyzw、Custom2.xyzw 的顺序勾选对应通道。");

        Color oldColor = GUI.color;
        if (index == 0)
        {
            GUI.color = new Color(0.7f, 0.7f, 0.7f);
        }
        else
        {
            GUI.color = occupied ? new Color(1f, 0.72f, 0.25f) : new Color(0.55f, 0.85f, 0.55f);
        }
        EditorGUI.LabelField(hintRect, hintContent, EditorStyles.miniLabel);
        GUI.color = oldColor;
    }

    private static string DescribeOccupation(MaterialEditor editor, MaterialProperty prop, int index, out bool occupied)
    {
        occupied = false;

        if (index == 0)
        {
            return "未使用";
        }

        var material = editor.targets.Length > 0 ? editor.targets[0] as Material : null;
        if (material == null)
        {
            return string.Empty;
        }

        Shader shader = material.shader;
        int count = ShaderUtil.GetPropertyCount(shader);
        var owners = new System.Collections.Generic.List<string>();

        for (int i = 0; i < count; i++)
        {
            string name = ShaderUtil.GetPropertyName(shader, i);
            if (name == prop.name || !name.Contains("CustomChannel"))
            {
                continue;
            }
            if (!material.HasProperty(name) || Mathf.RoundToInt(material.GetFloat(name)) != index)
            {
                continue;
            }

            string description = ShaderUtil.GetPropertyDescription(shader, i);
            owners.Add(string.IsNullOrEmpty(description) ? name : description);
        }

        if (owners.Count == 0)
        {
            return "未占用";
        }

        occupied = true;
        return owners.Count == 1
            ? "已被 " + owners[0] + " 占用"
            : "已被 " + owners[0] + " 等 " + owners.Count + " 处占用";
    }
}