using UnityEditor;
using UnityEngine;

/// <summary>
/// Drawer for the RequireInterface attribute.
/// </summary>

namespace NEG.Utils
{
    [CustomPropertyDrawer(typeof(RequireInterfaceAttribute))]
    public class RequireInterfaceDrawer : PropertyDrawer
    {
        /// <summary>
        ///     Overrides GUI drawing for the attribute.
        /// </summary>
        /// <param name="position">Position.</param>
        /// <param name="property">Property.</param>
        /// <param name="label">Label.</param>
        public override void OnGUI(Rect position, SerializedProperty property, GUIContent label)
        {
            // Check if this is reference type property.
            if (property.propertyType == SerializedPropertyType.ObjectReference)
            {
                // Get attribute parameters.
                var requiredAttribute = attribute as RequireInterfaceAttribute;
                // Begin drawing property field.
                EditorGUI.BeginProperty(position, label, property);
                // Draw property field.
                property.objectReferenceValue = EditorGUI.ObjectField(position, label, property.objectReferenceValue,
                    requiredAttribute.requiredType, true);
                // Finish drawing property field.
                EditorGUI.EndProperty();
            }
            else
            {
                // If field is not reference, show error message.
                // Save previous color and change GUI to red.
                var previousColor = GUI.color;
                GUI.color = Color.red;
                // Display label with error message.
                EditorGUI.LabelField(position, label, new GUIContent("Property is not a reference type"));
                // Revert color change.
                GUI.color = previousColor;
            }
        }
    }
}