using System;
using System.Collections.Generic;
using JD.TeaBoxAddinSystem.Addins.Description;

namespace JD.TeaBoxAddinSystem.Addins.Internal
{
    using ExtensionChangedEventHandler = EventHandler<ExtensionNodeChangedEventArgs>;

    internal class ChangedHandlerManager
    {
        #region Variables

        private Dictionary<string, ExtensionChangedEventHandler> m_handlers = new Dictionary<string, ExtensionChangedEventHandler>();

        #endregion

        #region Methods

        /// <summary>
        /// Adds an handler for the given path.
        /// </summary>
        /// <param name="path"></param>
        /// <param name="handler"></param>
        public void Add(string path, ExtensionChangedEventHandler handler)
        {
            System.Diagnostics.Debug.Assert(!string.IsNullOrEmpty(path));
            System.Diagnostics.Debug.Assert(handler != null);
            // Path should already be normalized.
            System.Diagnostics.Debug.Assert(path == ExtensionPoint.NormalizePath(path));

            ExtensionChangedEventHandler existingHandler;
            m_handlers.TryGetValue(path, out existingHandler);
            existingHandler += handler;
            m_handlers[path] = existingHandler;

            // Trigger it right now if the node already exists
            TreeNode existingNode = AddinManager.ExtensionTree[path];
            if (existingNode != null)
            {
                handler(null, new ExtensionNodeChangedEventArgs(existingNode));
            }
        }

        /// <summary>
        /// Removes an handler for the given path.
        /// </summary>
        /// <param name="path"></param>
        /// <param name="handler"></param>
        public void Remove(string path, ExtensionChangedEventHandler handler)
        {
            System.Diagnostics.Debug.Assert(!string.IsNullOrEmpty(path));
            System.Diagnostics.Debug.Assert(handler != null);
            // Path should already be normalized.
            System.Diagnostics.Debug.Assert(path == ExtensionPoint.NormalizePath(path));

            ExtensionChangedEventHandler existingHandler;
            if (m_handlers.TryGetValue(path, out existingHandler))
            {
                existingHandler -= handler;

                if (existingHandler == null)
                {
                    m_handlers.Remove(path);
                }
            }
        }

        /// <summary>
        /// Clears all the handlers.
        /// </summary>
        public void Clear()
        {
            m_handlers.Clear();
        }

        /// <summary>
        /// Triggers a changed event.
        /// </summary>
        /// <param name="e"></param>
        public void OnChanged(ExtensionNodeChangedEventArgs e)
        {
            ExtensionChangedEventHandler existingHandler;
            if (m_handlers.TryGetValue(e.Path, out existingHandler))
            {
                System.Diagnostics.Debug.Assert(existingHandler != null);
                existingHandler(null, e);
            }
        }        

        #endregion
    }
}