// (c) Copyright Ascensio System SIA 2010-2022
//
// This program is a free software product.
// You can redistribute it and/or modify it under the terms
// of the GNU Affero General Public License (AGPL) version 3 as published by the Free Software
// Foundation. In accordance with Section 7(a) of the GNU AGPL its Section 15 shall be amended
// to the effect that Ascensio System SIA expressly excludes the warranty of non-infringement of
// any third-party rights.
//
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// of MERCHANTABILITY or FITNESS FOR A PARTICULAR  PURPOSE. For details, see
// the GNU AGPL at: http://www.gnu.org/licenses/agpl-3.0.html
//
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//
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// display Appropriate Legal Notices, as required under Section 5 of the GNU AGPL version 3.
//
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// distributing the program. Pursuant to Section 7(e) we decline to grant you any rights under
// trademark law for use of our trademarks.
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// content are licensed under the terms of the Creative Commons Attribution-ShareAlike 4.0
// International. See the License terms at http://creativecommons.org/licenses/by-sa/4.0/legalcode

namespace ASC.EventBus;

public partial class InMemoryEventBusSubscriptionsManager : IEventBusSubscriptionsManager
{
    private readonly Dictionary<string, List<SubscriptionInfo>> _handlers;
    private readonly List<Type> _eventTypes;

    public event EventHandler<string> OnEventRemoved;

    public InMemoryEventBusSubscriptionsManager()
    {
        _handlers = new Dictionary<string, List<SubscriptionInfo>>();
        _eventTypes = new List<Type>();
    }

    public bool IsEmpty => _handlers is { Count: 0 };
    public void Clear() => _handlers.Clear();

    public void AddDynamicSubscription<TH>(string eventName)
        where TH : IDynamicIntegrationEventHandler
    {
        DoAddSubscription(typeof(TH), eventName, isDynamic: true);
    }

    public void AddSubscription<T, TH>()
        where T : IntegrationEvent
        where TH : IIntegrationEventHandler<T>
    {
        var eventName = GetEventKey<T>();

        DoAddSubscription(typeof(TH), eventName, isDynamic: false);

        if (!_eventTypes.Contains(typeof(T)))
        {
            _eventTypes.Add(typeof(T));
        }
    }

    private void DoAddSubscription(Type handlerType, string eventName, bool isDynamic)
    {
        if (!HasSubscriptionsForEvent(eventName))
        {
            _handlers.Add(eventName, new List<SubscriptionInfo>());
        }

        if (_handlers[eventName].Any(s => s.HandlerType == handlerType))
        {
            throw new ArgumentException(
                $"Handler Type {handlerType.Name} already registered for '{eventName}'", nameof(handlerType));
        }

        if (isDynamic)
        {
            _handlers[eventName].Add(SubscriptionInfo.Dynamic(handlerType));
        }
        else
        {
            _handlers[eventName].Add(SubscriptionInfo.Typed(handlerType));
        }
    }


    public void RemoveDynamicSubscription<TH>(string eventName)
        where TH : IDynamicIntegrationEventHandler
    {
        var handlerToRemove = FindDynamicSubscriptionToRemove<TH>(eventName);
        DoRemoveHandler(eventName, handlerToRemove);
    }


    public void RemoveSubscription<T, TH>()
        where TH : IIntegrationEventHandler<T>
        where T : IntegrationEvent
    {
        var handlerToRemove = FindSubscriptionToRemove<T, TH>();
        var eventName = GetEventKey<T>();
        DoRemoveHandler(eventName, handlerToRemove);
    }


    private void DoRemoveHandler(string eventName, SubscriptionInfo subsToRemove)
    {
        if (subsToRemove != null)
        {
            _handlers[eventName].Remove(subsToRemove);
            if (!_handlers[eventName].Any())
            {
                _handlers.Remove(eventName);
                var eventType = _eventTypes.SingleOrDefault(e => e.Name == eventName);
                if (eventType != null)
                {
                    _eventTypes.Remove(eventType);
                }
                RaiseOnEventRemoved(eventName);
            }

        }
    }

    public IEnumerable<SubscriptionInfo> GetHandlersForEvent<T>() where T : IntegrationEvent
    {
        var key = GetEventKey<T>();
        return GetHandlersForEvent(key);
    }
    public IEnumerable<SubscriptionInfo> GetHandlersForEvent(string eventName) => _handlers[eventName];

    private void RaiseOnEventRemoved(string eventName)
    {
        var handler = OnEventRemoved;
        handler?.Invoke(this, eventName);
    }


    private SubscriptionInfo FindDynamicSubscriptionToRemove<TH>(string eventName)
        where TH : IDynamicIntegrationEventHandler
    {
        return DoFindSubscriptionToRemove(eventName, typeof(TH));
    }


    private SubscriptionInfo FindSubscriptionToRemove<T, TH>()
            where T : IntegrationEvent
            where TH : IIntegrationEventHandler<T>
    {
        var eventName = GetEventKey<T>();
        return DoFindSubscriptionToRemove(eventName, typeof(TH));
    }

    private SubscriptionInfo DoFindSubscriptionToRemove(string eventName, Type handlerType)
    {
        if (!HasSubscriptionsForEvent(eventName))
        {
            return null;
        }

        return _handlers[eventName].SingleOrDefault(s => s.HandlerType == handlerType);

    }

    public bool HasSubscriptionsForEvent<T>() where T : IntegrationEvent
    {
        var key = GetEventKey<T>();
        return HasSubscriptionsForEvent(key);
    }
    public bool HasSubscriptionsForEvent(string eventName) => _handlers.ContainsKey(eventName);

    public Type GetEventTypeByName(string eventName) => _eventTypes.SingleOrDefault(t => t.Name == eventName);

    public string GetEventKey<T>()
    {
        return typeof(T).Name;
    }
}