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

namespace Golems
{
    // http://wiki.unity3d.com/index.php?title=EnumFlagPropertyDrawer&oldid=19986S
    [CustomPropertyDrawer(typeof(EnumFlagAttribute))]
    public class EnumFlagDrawer : PropertyDrawer
    {
        private const BindingFlags k_BindingFlags = BindingFlags.Instance | BindingFlags.Static | BindingFlags.Public |
                                                          BindingFlags.NonPublic;
        
        public override void OnGUI(Rect position, SerializedProperty property, GUIContent label)
        {
            EnumFlagAttribute flagSettings = (EnumFlagAttribute) attribute;
            Enum targetEnum = GetBaseProperty<Enum>(property);

            string propName = flagSettings.AttributeName;
            if (string.IsNullOrEmpty(propName))
                propName = property.name;

            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, k_BindingFlags);
                reflectionTarget = fieldInfo.GetValue(reflectionTarget);
            }

            return (T) reflectionTarget;
        }
    }
}