/*
 * Copyright (c) Contributors, http://opensimulator.org/
 * See CONTRIBUTORS.TXT for a full list of copyright holders.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions are met:
 *     * Redistributions of source code must retain the above copyright
 *       notice, this list of conditions and the following disclaimer.
 *     * Redistributions in binary form must reproduce the above copyright
 *       notice, this list of conditions and the following disclaimer in the
 *       documentation and/or other materials provided with the distribution.
 *     * Neither the name of the OpenSimulator Project nor the
 *       names of its contributors may be used to endorse or promote products
 *       derived from this software without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE DEVELOPERS ``AS IS'' AND ANY
 * EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
 * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
 * DISCLAIMED. IN NO EVENT SHALL THE CONTRIBUTORS BE LIABLE FOR ANY
 * DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
 * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
 * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
 * ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
 * SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 */

using System;
using System.Collections.Generic;
using System.IO;
using System.Reflection;
using log4net;
using Mono.Addins;

namespace OpenSim.Framework
{
    /// <summary>
    /// Exception thrown if an incorrect number of plugins are loaded
    /// </summary>
    public class PluginConstraintViolatedException : Exception
    {
        public PluginConstraintViolatedException () : base() {}
        public PluginConstraintViolatedException (string msg) : base(msg) {}
        public PluginConstraintViolatedException (string msg, Exception e) : base(msg, e) {}
    }

    /// <summary>
    /// Classes wishing to impose constraints on plugin loading must implement
    /// this class and pass it to PluginLoader AddConstraint()
    /// </summary>
    public interface IPluginConstraint
    {
        string Message { get; }
        bool Apply(string extpoint);
    }

    /// <summary>
    /// Classes wishing to select specific plugins from a range of possible options
    /// must implement this class and pass it to PluginLoader Load()
    /// </summary>
    public interface IPluginFilter
    {
        bool Apply(PluginExtensionNode plugin);
    }

    /// <summary>
    /// Generic Plugin Loader
    /// </summary>
    public class PluginLoader <T> : IDisposable where T : IPlugin
    {
        private const int max_loadable_plugins = 10000;

        private List<T> loaded = new List<T>();
        private List<string> extpoints = new List<string>();
        private PluginInitialiserBase initialiser;

        private Dictionary<string,IPluginConstraint> constraints
            = new Dictionary<string,IPluginConstraint>();

        private Dictionary<string,IPluginFilter> filters
            = new Dictionary<string,IPluginFilter>();

        private static readonly ILog log
            = LogManager.GetLogger(MethodBase.GetCurrentMethod().DeclaringType);

        public PluginInitialiserBase Initialiser
        {
            set { initialiser = value; }
            get { return initialiser; }
        }

        public List<T> Plugins
        {
            get { return loaded; }
        }

        public T Plugin
        {
            get { return (loaded.Count == 1)? loaded [0] : default (T); }
        }

        public PluginLoader()
        {
            Initialiser = new PluginInitialiserBase();
            initialise_plugin_dir_(".");
        }

        public PluginLoader(PluginInitialiserBase init)
        {
            Initialiser = init;
            initialise_plugin_dir_(".");
        }

        public PluginLoader(PluginInitialiserBase init, string dir)
        {
            Initialiser = init;
            initialise_plugin_dir_(dir);
        }

        public void Add(string extpoint)
        {
            if (extpoints.Contains(extpoint))
                return;

            extpoints.Add(extpoint);
        }

        public void Add(string extpoint, IPluginConstraint cons)
        {
            Add(extpoint);
            AddConstraint(extpoint, cons);
        }

        public void Add(string extpoint, IPluginFilter filter)
        {
            Add(extpoint);
            AddFilter(extpoint, filter);
        }

        public void AddConstraint(string extpoint, IPluginConstraint cons)
        {
            constraints.Add(extpoint, cons);
        }

        public void AddFilter(string extpoint, IPluginFilter filter)
        {
            filters.Add(extpoint, filter);
        }

        public void Load(string extpoint)
        {
            Add(extpoint);
            Load();
        }

        public void Load()
        {
            foreach (string ext in extpoints)
            {
                log.Info("[PLUGINS]: Loading extension point " + ext);

                if (constraints.ContainsKey(ext))
                {
                    IPluginConstraint cons = constraints[ext];
                    if (cons.Apply(ext))
                        log.Error("[PLUGINS]: " + ext + " failed constraint: " + cons.Message);
                }

                IPluginFilter filter = null;

                if (filters.ContainsKey(ext))
                    filter = filters[ext];

                List<T> loadedPlugins = new List<T>();
                foreach (PluginExtensionNode node in AddinManager.GetExtensionNodes(ext))
                {
                    log.Info("[PLUGINS]: Trying plugin " + node.Path);

                    if ((filter != null) && (filter.Apply(node) == false))
                        continue;

                    T plugin = (T)node.CreateInstance();
                    loadedPlugins.Add(plugin);
                }

                // We do Initialise() in a second loop after CreateInstance
                // So that modules who need init before others can do it
                // Example: Script Engine Component System needs to load its components before RegionLoader starts
                foreach (T plugin in loadedPlugins)
                {
                    Initialiser.Initialise(plugin);
                    Plugins.Add(plugin);
                }
            }
        }

        /// <summary>
        /// Unregisters Mono.Addins event handlers, allowing temporary Mono.Addins
        /// data to be garbage collected. Since the plugins created by this loader
        /// are meant to outlive the loader itself, they must be disposed separately
        /// </summary>
        public void Dispose()
        {
            AddinManager.AddinLoadError -= on_addinloaderror_;
            AddinManager.AddinLoaded -= on_addinloaded_;
        }

        private void initialise_plugin_dir_(string dir)
        {
            if (AddinManager.IsInitialized == true)
                return;

            log.Info("[PLUGINS]: Initializing addin manager");

            AddinManager.AddinLoadError += on_addinloaderror_;
            AddinManager.AddinLoaded += on_addinloaded_;

            clear_registry_(dir);

            suppress_console_output_(true);
            AddinManager.Initialize(dir);
            AddinManager.Registry.Update(null);
            suppress_console_output_(false);
        }

        private void on_addinloaded_(object sender, AddinEventArgs args)
        {
            log.Info ("[PLUGINS]: Plugin Loaded: " + args.AddinId);
        }

        private void on_addinloaderror_(object sender, AddinErrorEventArgs args)
        {
            if (args.Exception == null)
                log.Error ("[PLUGINS]: Plugin Error: "
                        + args.Message);
            else
                log.Error ("[PLUGINS]: Plugin Error: "
                        + args.Exception.Message + "\n"
                        + args.Exception.StackTrace);
        }

        private void clear_registry_(string dir)
        {
            // The Mono addin manager (in Mono.Addins.dll version 0.2.0.0)
            // occasionally seems to corrupt its addin cache
            // Hence, as a temporary solution we'll remove it before each startup

            try
            {
                if (Directory.Exists(dir + "/addin-db-000"))
                    Directory.Delete(dir + "/addin-db-000", true);

                if (Directory.Exists(dir + "/addin-db-001"))
                    Directory.Delete(dir + "/addin-db-001", true);
            }
            catch (IOException)
            {
                // If multiple services are started simultaneously, they may
                // each test whether the directory exists at the same time, and
                // attempt to delete the directory at the same time. However,
                // one of the services will likely succeed first, causing the
                // second service to throw an IOException. We catch it here and
                // continue on our merry way.
                // Mike 2008.08.01, patch from Zaki
            }
        }

        private static TextWriter prev_console_;
        public void suppress_console_output_(bool save)
        {
            if (save)
            {
                prev_console_ = System.Console.Out;
                System.Console.SetOut(new StreamWriter(Stream.Null));
            }
            else
            {
                if (prev_console_ != null)
                    System.Console.SetOut(prev_console_);
            }
        }
    }

    public class PluginExtensionNode : ExtensionNode
    {
        [NodeAttribute]
        string id = "";

        [NodeAttribute]
        string provider = "";

        [NodeAttribute]
        string type = "";

        Type typeobj;

        public string ID { get { return id; } }
        public string Provider { get { return provider; } }
        public string TypeName { get { return type; } }

        public Type TypeObject
        {
            get
            {
                if (typeobj != null)
                    return typeobj;

                if (type.Length == 0)
                    throw new InvalidOperationException("Type name not specified.");

                return typeobj = Addin.GetType(type, true);
            }
        }

        public object CreateInstance()
        {
            return Activator.CreateInstance(TypeObject);
        }
    }

    /// <summary>
    /// Constraint that bounds the number of plugins to be loaded.
    /// </summary>
    public class PluginCountConstraint : IPluginConstraint
    {
        private int min;
        private int max;

        public PluginCountConstraint(int exact)
        {
            min = exact;
            max = exact;
        }

        public PluginCountConstraint(int minimum, int maximum)
        {
            min = minimum;
            max = maximum;
        }

        public string Message
        {
            get
            {
                return "The number of plugins is constrained to the interval ["
                    + min + ", " + max + "]";
            }
        }

        public bool Apply (string extpoint)
        {
            int count = AddinManager.GetExtensionNodes(extpoint).Count;

            if ((count < min) || (count > max))
                throw new PluginConstraintViolatedException(Message);

            return true;
        }
    }

    /// <summary>
    /// Filters out which plugin to load based on the plugin name or names given.  Plugin names are contained in
    /// their addin.xml
    /// </summary>
    public class PluginProviderFilter : IPluginFilter
    {
        private string[] m_filters;

        /// <summary>
        /// Constructor.
        /// </summary>
        /// <param name="p">
        /// Plugin name or names on which to filter.  Multiple names should be separated by commas.
        /// </param>
        public PluginProviderFilter(string p)
        {
            m_filters = p.Split(',');

            for (int i = 0; i < m_filters.Length; i++)
            {
                m_filters[i] = m_filters[i].Trim();
            }
        }

        /// <summary>
        /// Apply this filter to the given plugin.
        /// </summary>
        /// <param name="plugin"></param>
        /// <returns>true if the plugin's name matched one of the filters, false otherwise.</returns>
        public bool Apply (PluginExtensionNode plugin)
        {
            for (int i = 0; i < m_filters.Length; i++)
            {
                if (m_filters[i] == plugin.Provider)
                {
                    return true;
                }
            }

            return false;
        }
    }

    /// <summary>
    /// Filters plugins according to their ID. Plugin IDs are contained in their addin.xml
    /// </summary>
    public class PluginIdFilter : IPluginFilter
    {
        private string[] m_filters;

        /// <summary>
        /// Constructor.
        /// </summary>
        /// <param name="p">
        /// Plugin ID or IDs on which to filter. Multiple names should be separated by commas.
        /// </param>
        public PluginIdFilter(string p)
        {
            m_filters = p.Split(',');

            for (int i = 0; i < m_filters.Length; i++)
            {
                m_filters[i] = m_filters[i].Trim();
            }
        }

        /// <summary>
        /// Apply this filter to <paramref name="plugin" />.
        /// </summary>
        /// <param name="plugin">PluginExtensionNode instance to check whether it passes the filter.</param>
        /// <returns>true if the plugin's ID matches one of the filters, false otherwise.</returns>
        public bool Apply (PluginExtensionNode plugin)
        {
            for (int i = 0; i < m_filters.Length; i++)
            {
                if (m_filters[i] == plugin.ID)
                {
                    return true;
                }
            }

            return false;
        }
    }
}