using UnityEngine;
using UnityEditor;

namespace BadDog.Rendering.AreaLight
{
    /// <summary>
    /// Restricts values to power-of-2 resolutions: 256, 512, 1024, 2048, 4096, 8192
    /// </summary>
    [CustomPropertyDrawer(typeof(ShadowAtlasResolutionAttribute))]
    public class ShadowAtlasResolutionDrawer : PropertyDrawer
    {
        private static readonly int[] k_AllowedResolutions = { 256, 512, 1024, 2048, 4096, 8192 };
        private static readonly string[] k_ResolutionLabels = { "256", "512", "1024", "2048", "4096", "8192" };

        public override void OnGUI(Rect position, SerializedProperty property, GUIContent label)
        {
            if (property.propertyType != SerializedPropertyType.Integer)
            {
                EditorGUI.PropertyField(position, property, label);
                return;
            }

            int currentValue = property.intValue;
            int selectedIndex = GetClosestResolutionIndex(currentValue);

            EditorGUI.BeginProperty(position, label, property);
            
            Rect popupRect = EditorGUI.PrefixLabel(position, label);
            int newIndex = EditorGUI.Popup(popupRect, selectedIndex, k_ResolutionLabels);
            
            if (newIndex != selectedIndex)
            {
                property.intValue = k_AllowedResolutions[newIndex];
            }
            else
            {
                int clampedValue = k_AllowedResolutions[selectedIndex];
                if (currentValue != clampedValue)
                {
                    property.intValue = clampedValue;
                }
            }

            EditorGUI.EndProperty();
        }

        private int GetClosestResolutionIndex(int value)
        {
            int closestIndex = 0;
            int minDiff = Mathf.Abs(value - k_AllowedResolutions[0]);

            for (int i = 1; i < k_AllowedResolutions.Length; i++)
            {
                int diff = Mathf.Abs(value - k_AllowedResolutions[i]);
                if (diff < minDiff)
                {
                    minDiff = diff;
                    closestIndex = i;
                }
            }

            return closestIndex;
        }
    }
}