using System;
using System.Linq;
using System.Reflection;
using UnityEngine;
using Object = UnityEngine.Object;

namespace SerializableFunc
{
    [Serializable]
    public class SerializableAction
    {
        [SerializeField] private Object targetObject;
        [SerializeField] private string methodName;

        private Action cachedAction;

        private static readonly BindingFlags SuitableMethodsFlags =
            BindingFlags.FlattenHierarchy | BindingFlags.Public | BindingFlags.Instance;

        public Object TargetObject
        {
            get => targetObject;
            set => targetObject = value;
        }

        public string MethodName
        {
            get => methodName;
            set => methodName = value;
        }

        private Action GetAction()
        {
            if (targetObject == null || string.IsNullOrWhiteSpace(methodName)) return null;
            if (cachedAction == null)
            {
                MethodInfo info = targetObject
                    .GetType()
                    .GetMethods(SuitableMethodsFlags)
                    .FirstOrDefault(IsTargetMethodInfo);

                if (info == null)
                {
                    throw new MissingMethodException(
                        $"Object \"{targetObject.name}\" is missing target void method: {methodName}"
                    );
                }

                cachedAction = (Action)Delegate.CreateDelegate(typeof(Action), targetObject, methodName);
            }

            return cachedAction;
        }

        private bool IsTargetMethodInfo(MethodInfo methodInfo)
        {
            if (!string.Equals(methodInfo.Name, methodName, StringComparison.InvariantCulture))
                return false;

            if (methodInfo.ReturnType != typeof(void))
                return false;

            // Only allow parameterless void methods for this version
            if (methodInfo.GetParameters().Length != 0)
                return false;

            return true;
        }

        public void Invoke()
        {
            GetAction()?.Invoke();
        }

        public static implicit operator Action(SerializableAction serializableAction)
        {
            return serializableAction?.GetAction();
        }
    }
}