using System.Collections.Generic;
using JD.Kernel.Classes;
using JD.Kernel.StaticHelpers;

namespace JD.TeaBoxAddinSystem.Addins
{
    public class ActionHandlerRepository<THandler>
        where THandler : class
    {
        #region Variables

        private readonly Dictionary<string, Reference<THandler>> m_handlers = new Dictionary<string, Reference<THandler>>();

        #endregion

        #region Constructor

        public ActionHandlerRepository(string extensionPath)
        {
            Throw.IfEmpty(extensionPath, "extensionPath");

            Init(extensionPath);
        }

        /// <summary>
        /// Ctor for unit test purpose.
        /// </summary>
        protected ActionHandlerRepository()
        {
        }

        #endregion

        #region Methods

        protected void Init(string extensionPath)
        {
            System.Diagnostics.Debug.Assert(!string.IsNullOrEmpty(extensionPath));

            foreach (HandlerExtensionNode<THandler> node in GetExtensionNodes(extensionPath))
            {
                if (!string.IsNullOrEmpty(node.ActionId))
                {
                    if (!m_handlers.ContainsKey(node.ActionId))
                    {
                        m_handlers.Add(node.ActionId, node.Handler);
                    }
                    else
                    {
                        LogService.LogService.LogError("More than one action handler registered with action {0}.", node.ActionId);
                    }
                }
            }
        }

        /// <summary>
        /// Virtual for unit test purpose.
        /// </summary>
        protected virtual IEnumerable<HandlerExtensionNode<THandler>> GetExtensionNodes(string extensionPath)
        {
            return AddinManager.GetExtensionNodes<HandlerExtensionNode<THandler>>(extensionPath);
        }

        /// <summary>
        /// Virtual for unit test purpose.
        /// </summary>
        public virtual bool TryGetHandler(string actionId, out THandler handler)
        {
            Reference<THandler> reference;
            if (m_handlers.TryGetValue(actionId, out reference))
            {
                handler = reference.Value;
            }
            else
            {
                handler = null;
            }

            return handler != null;
        }

        /// <summary>
        /// Adds manually the handler in the handler list.
        /// </summary>
        /// <returns>False if an handler was already present for that action id.</returns>
        public bool AddHandler(string actionId, THandler handler)
        {
            Reference<THandler> reference;
            if (!m_handlers.TryGetValue(actionId, out reference))
            {
                m_handlers.Add(actionId, Reference<THandler>.FromValue(handler));
                return true;
            }
            return false;
        }

        #endregion
    }
}