using System;
using System.Collections.Generic;
using System.Drawing;
using JD.Kernel.Classes;
using JD.Kernel.StaticHelpers;
using JD.LogService;
using JD.TeaBoxAddinSystem.Addins.Description;
using JD.TeaBoxAddinSystem.Addins.Description.Conditions;
using JD.TeaBoxAddinSystem.Addins.Internal;

namespace JD.TeaBoxAddinSystem.Addins
{
    /// <summary>
    /// Addin Manager.
    /// </summary>
    public static class AddinManager
    {
        private static readonly object m_lock = new object();
        private static readonly AddinSessionService m_sessionService = new AddinSessionService();
        private static readonly List<ILogger> m_loggers = new List<ILogger>();
        private static Implementation m_implementation = new Implementation();
        
        /// <summary>
        /// Loggers can listen to addin events as well as addin loading errors.
        /// </summary>
        public static IList<ILogger> Loggers
        {
            get
            {
                return m_loggers;
            }
        }

        /// <summary>
        /// Loaded addins.
        /// </summary>
        public static ICollection<Addin> LoadedAddins
        {
            get
            {
                return SessionService.LoadedAddins;
            }
        }

        /// <summary>
        /// Loaded Extension Type Sets.
        /// </summary>
        public static IReadOnlyDictionary<string, ExtensionTypeSet> ExtensionTypeSets
        {
            get
            {
                return SessionService.ExtensionTypeSets;
            }
        }

        /// <summary>
        /// Loaded Condition Types.
        /// </summary>
        public static IReadOnlyDictionary<string, ConditionType> ConditionTypes
        {
            get
            {
                return SessionService.ConditionTypes;
            }
        }

        /// <summary>
        /// Loaded extension points.
        /// </summary>
        public static IReadOnlyDictionary<string, ExtensionPoint> ExtensionPoints
        {
            get
            {
                return SessionService.ExtensionPoints;
            }
        }

        /// <summary>
        /// Extension tree.
        /// </summary>
        public static TreeNode ExtensionTree
        {
            get
            {
                return SessionService.ExtensionTree;
            }
        }

        internal static AddinSessionService SessionService
        {
            get
            {
                return m_sessionService;
            }
        }
        
        static AddinManager()
        {
            AppDomain.CurrentDomain.AssemblyResolve += CurrentDomain_AssemblyResolve;
        }
        
        /// <summary>
        /// Returns whether the given <paramref name="addin"/> is loaded.
        /// </summary>
        /// <param name="addin"></param>
        /// <returns></returns>
        public static bool IsAddinLoaded(Addin addin)
        {
            return SessionService.IsAddinLoaded(addin);
        }

        /// <summary>
        /// Returns whether the given <paramref name="module"/> is loaded.
        /// </summary>
        /// <param name="module"></param>
        /// <returns></returns>
        public static bool IsModuleLoaded(Module module)
        {
            return SessionService.IsModuleLoaded(module);
        }

        /// <summary>
        /// Loads the given <paramref name="addin"/>.
        /// </summary>
        /// <param name="addin"></param>
        public static bool LoadAddin(Addin addin)
        {
            return SessionService.LoadAddin(addin);
        }

        /// <summary>
        /// Unloads the given <paramref name="addin"/>.
        /// </summary>
        /// <param name="addin"></param>
        public static bool UnloadAddin(Addin addin)
        {
            return SessionService.UnloadAddin(addin);
        }

        /// <summary>
        /// Unloads all the loaded <see cref="Addin"/>s.
        /// </summary>
        public static void UnloadAllAddins()
        {
            UnloadAllAddins(false);
        }

        /// <summary>
        /// Unloads all the loaded <see cref="Addin"/>s. Used for tests mostly.
        /// </summary>
        /// <param name="destroyHandlers">Whether to destroy event handlers.</param>
        public static void UnloadAllAddins(bool destroyHandlers)
        {
            SessionService.UnloadAllAddins(destroyHandlers);
        }

        /// <summary>
        /// This method will reevaluate all the loaded <see cref="PolledConditionNode"/>s.
        /// </summary>
        /// <remarks>
        /// Call this periodically in your application. The more frequent the better but 
        /// there's a performance cost associated with it.
        /// </remarks>
        public static void ReevaluatePolledConditionNodes()
        {
            SessionService.ConditionManager.ReevaluatePolledConditionNodes();
        }
        
        /// <summary>
        /// Gets an extension node at the given <paramref name="path"/>.
        /// </summary>
        /// <param name="path"></param>
        /// <returns></returns>
        public static ExtensionNode GetExtensionNode(string path)
        {
            TreeNode node = ExtensionTree[path];

            if (node == null)
            {
                return null;
            }

            return node.ExtensionNode;
        }

        /// <summary>
        /// Gets a list of extension nodes at the given <paramref name="path"/> with type <typeparamref name="T"/>.
        /// </summary>
        /// <remarks>
        /// This method returns only the objects of type <typeparamref name="T"/> and ignores other nodes.
        /// </remarks>
        /// <typeparam name="T">Type of extension nodes.</typeparam>
        /// <param name="path"></param>
        /// <returns>A non null list of extension nodes of type <typeparamref name="T"/>. List may be empty if the path does not exist.</returns>
        public static IEnumerable<T> GetExtensionNodes<T>(string path) where T : ExtensionNode
        {
            return m_implementation.GetExtensionNodes<T>(path);
        }

        /// <summary>
        /// Gets a list of extension objects at a given <paramref name="path"/>.
        /// </summary>
        /// <remarks>
        /// Returns an empty collection when path does not exists.
        /// </remarks>
        /// <typeparam name="T"></typeparam>
        /// <param name="path"></param>
        /// <returns></returns>
        public static IList<T> GetExtensionObjects<T>(string path)
        {
            return m_implementation.GetExtensionObjects<T>(path);
        }

        /// <summary>
        /// Creates a new list of extension objects from the given <paramref name="path"/>.
        /// </summary>
        /// <remarks>
        /// This method returns only the objects of type <typeparamref name="T"/> and ignores other created objects.
        /// </remarks>
        /// <typeparam name="T"></typeparam>
        /// <param name="path"></param>
        /// <returns></returns>
        public static IEnumerable<T> CreateExtensionObjects<T>(string path) where T : class
        {
            ExtensionNode node = GetExtensionNode(path);

            if (node == null)
            {
                yield break;
            }

            foreach (ExtensionNode childNode in node.ChildNodes)
            {
                object extensionObject = childNode.CreateExtensionObject();
                if (!(extensionObject is T))
                {
                    throw new ArgumentException(
                        $"Extension node {childNode.FullPath} created object {extensionObject} which is not of the expected type {typeof(T).Name}");
                }

                yield return (T)extensionObject;
            }
        }

        /// <summary>
        /// Registers the given <paramref name="handler"/> on the <see cref="ExtensionNode"/> at the given <paramref name="path"/>.
        /// </summary>
        /// <param name="path"></param>
        /// <param name="handler"></param>
        public static void AddExtensionChangedHandler(string path, EventHandler<ExtensionNodeChangedEventArgs> handler)
        {
            SessionService.AddExtensionChangedHandler(path, handler);
        }

        /// <summary>
        /// Unregisters the given <paramref name="handler"/> on the <see cref="ExtensionNode"/> at the given <paramref name="path"/>.
        /// </summary>
        /// <param name="path"></param>
        /// <param name="handler"></param>
        public static void RemoveExtensionChangedHandler(string path, EventHandler<ExtensionNodeChangedEventArgs> handler)
        {
            SessionService.RemoveExtensionChangedHandler(path, handler);
        }

        /// <summary>
        /// For testing purposes, let swap the implementation.
        /// </summary>
        public static IDisposable UseMockImplementation(Implementation implementation)
        {
            Throw.IfNull(implementation, "implementation");

            m_implementation = implementation;
            return new DisposableHelper(delegate
            {
                m_implementation = new Implementation();
            });
        }

        public static Image GetImage(string imageName)
        {
            return m_implementation.GetImage(imageName);
        }
        
        internal static void Log(LogEvent @event)
        {
            m_loggers.ForEach(logger => logger.Log(@event));
        }
        
        private static System.Reflection.Assembly CurrentDomain_AssemblyResolve(object sender, ResolveEventArgs args)
        {
            return SessionService.GetAssembly(args.Name);
        }
    }
}