using System;
using System.Reflection;
using UnityEditor;
using UnityEngine;

[CustomPropertyDrawer(typeof(EnumFlagAttribute))]
public class EnumFlagDrawer : PropertyDrawer {
  public override void OnGUI(Rect position, SerializedProperty property, GUIContent label) {
    EnumFlagAttribute flagSettings = (EnumFlagAttribute)attribute;
    Enum targetEnum = GetBaseProperty<Enum>(property);

    string propName = flagSettings.enumName;
    if (string.IsNullOrEmpty(propName))
      propName = property.displayName;

    EditorGUI.BeginProperty(position, label, property);
    Enum enumNew = EditorGUI.EnumFlagsField(position, propName, targetEnum);
    property.intValue = (int)Convert.ChangeType(enumNew, targetEnum.GetType());
    EditorGUI.EndProperty();
  }

  static T GetBaseProperty<T>(SerializedProperty prop) {
    // Separate the steps it takes to get to this property
    string[] separatedPaths = prop.propertyPath.Split('.');

    // Go down to the root of this serialized property
    System.Object reflectionTarget = prop.serializedObject.targetObject as object;
    // Walk down the path to get the target object
    foreach (var path in separatedPaths) {
      FieldInfo fieldInfo = reflectionTarget.GetType().GetField(path);
      reflectionTarget = fieldInfo.GetValue(reflectionTarget);
    }
    return (T)reflectionTarget;
  }
}