using OOO_WriteAndClear.EventBus.Signals;
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace OOO_WriteAndClear.EventBus
{
    public class EventBus
    {
        private static EventBus? _bus = null;

        protected EventBus()
        {
            _allSubscribers = new Dictionary<string, LinkedList<object>>();
        }

        public static EventBus GetService()
        {
            if (_bus is null)
                return _bus = new EventBus();
            return _bus;
        }


        public void Subscribe<T>(Action<T> signal) where T : ISignal
        {
            string? signalName = typeof(T).FullName;
            if (signalName is null)
                throw new NotSupportedException();
            if(_allSubscribers.ContainsKey(signalName))
            {
                _allSubscribers[signalName].AddLast(signal);
                return;
            }
            LinkedList<object> newSubscribers = new LinkedList<object>();
            newSubscribers.AddFirst(signal);
            _allSubscribers.Add(signalName, newSubscribers);
        }

        public void Unsubscribe<T>(Action<T> signal) where T : ISignal
        {
            string? signalName = typeof(T).FullName;
            if (signalName is null)
                throw new NotSupportedException();
            if (!_allSubscribers.ContainsKey(signalName))
                return;
            _allSubscribers[signalName].Remove(signal);
        }

        public void Invoke<T>(T signal) where T : ISignal
        {
            string? signalName = signal.GetType().FullName;
            if (signalName is null)
                throw new NotSupportedException();
            if (!_allSubscribers.ContainsKey(signalName))
                return;
            foreach(var action in _allSubscribers[signalName])
                ((Action<T>)action)?.Invoke(signal);
        }


        private Dictionary<string, LinkedList<object>> _allSubscribers;
    }
}