using System;
using System.Collections.Generic;
using TechbloxModdingAPI.Events;

namespace TechbloxModdingAPI.Utility
{
    /// <summary>
    /// Wraps the event handler in a try-catch block to avoid propagating exceptions.
    /// </summary>
    /// <typeparam name="T">The event arguments type</typeparam>
    public struct WrappedHandler<T>
    {
        private EventHandler<T> eventHandler;

        /// <summary>
        /// Store wrappers so we can unregister them properly
        /// </summary>
        private static Dictionary<EventHandler<T>, EventHandler<T>> wrappers =
            new Dictionary<EventHandler<T>, EventHandler<T>>();

        public static WrappedHandler<T> operator +(WrappedHandler<T> original, EventHandler<T> added)
        {
            EventHandler<T> wrapped = (sender, e) =>
            {
                try
                {
                    added(sender, e);
                }
                catch (Exception e1)
                {
                    EventRuntimeException wrappedException =
                        new EventRuntimeException($"EventHandler with arg type {typeof(T).Name} threw an exception",
                            e1);
                    Logging.LogWarning(wrappedException.ToString());
                }
            };
            wrappers.Add(added, wrapped);
            return new WrappedHandler<T> { eventHandler = original.eventHandler + wrapped };
        }

        public static WrappedHandler<T> operator -(WrappedHandler<T> original, EventHandler<T> removed)
        {
            if (!wrappers.TryGetValue(removed, out var wrapped)) return original;
            wrappers.Remove(removed);
            return new WrappedHandler<T> { eventHandler = original.eventHandler - wrapped };
        }

        public void Invoke(object sender, T args)
        {
            eventHandler?.Invoke(sender, args);
        }
    }
}