using System;
using System.Linq;
using System.Reflection;
using Module.Inspector.Editor.Utilities;
using UnityEditor;
using UnityEngine;

namespace Module.Inspector.Editor
{
    [CustomPropertyDrawer(typeof(PopupFromConstAttribute))]
    internal sealed class PopupFromConstAttributeDrawer : DrawerPropertyDrawer
    {
        private GUIContent[] names;
        private string[] values;
        
        public override bool Draw(Rect position, DrawerPropertyAttribute attribute, SerializedProperty property, GUIContent label, EditorPropertyUtility.Result result)
        {
            if (property.propertyType != SerializedPropertyType.String)
                return false;
            
            var att = (PopupFromConstAttribute)attribute;
            FetchConstArray(att);
                
            EditorGUI.BeginChangeCheck();
            EditorGUI.BeginProperty(position, label, property);
            {
                int index = Array.IndexOf(values, property.stringValue);
                int newIndex = EditorGUI.Popup(position, label, index, names);

                if (newIndex != -1 && index != newIndex)
                    property.stringValue = values[newIndex];
            }
            EditorGUI.EndProperty();
            bool changed = EditorGUI.EndChangeCheck();

            if (changed)
                property.serializedObject.ApplyModifiedProperties();
            
            return true;
        }
        
        public override string GetErrorMessage(SerializedProperty property)
        {
            return "Only supports integers";
        }

        private void FetchConstArray(PopupFromConstAttribute attribute)
        {
            if (names != null)
                return;

            FieldInfo[] fields = attribute.type.GetFields(BindingFlags.Public | BindingFlags.Static | BindingFlags.FlattenHierarchy)
                                          .Where(fi => fi.IsLiteral && !fi.IsInitOnly && fi.FieldType == typeof(string))
                                          .ToArray();

            names = new GUIContent[fields.Length + 1];
            values = new string[fields.Length + 1];
            
            names[0] = new GUIContent("-- Empty --");
            values[0] = string.Empty;

            for (var i = 0; i < fields.Length; i++)
            {
                FieldInfo fi = fields[i];
                var value = (string)fi.GetValue(null);
                
                names[i + 1] = new GUIContent(value);
                values[i + 1] = value;
            }
        }
    }
}