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 *     following disclaimer. 
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 *     copyright notice, this list of conditions and the 
 *     following disclaimer in the documentation and/or other 
 *     materials provided with the distribution. 
 * 
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using System.Collections.Generic;
using System.ComponentModel;
using XenAPI;

namespace XenAdmin.Actions.GUIActions
{

    /// <summary>
    /// MeddlingActionManager handles task events, categorises tasks depending upon whether they
    /// are ours or not, and creates MeddlingAction instances when necessary
    /// </summary>
    public class MeddlingActionManager
    {
        private static readonly log4net.ILog log = log4net.LogManager.GetLogger(System.Reflection.MethodBase.GetCurrentMethod().DeclaringType);

        /// <summary>
        /// Tasks that we've seen, but haven't categorised yet.  May only be acccesed under the DictionaryLock.
        /// </summary>
        private static readonly List<string> UnmatchedTasks = new List<string>();

        /// <summary>
        /// Tasks that we've categorised as not being ours, and the corresponding MeddlingAction that we created.  May
        /// only be accessed under the DictionaryLock.
        /// </summary>
        private static readonly Dictionary<string, MeddlingAction> MatchedTasks = new Dictionary<string, MeddlingAction>();

        private static readonly object DictionaryLock = new object();

        public static void TaskCollectionChanged(object sender, CollectionChangeEventArgs e)
        {
            lock (DictionaryLock)
            {
                Task task = (Task)e.Element;
                if (e.Action == CollectionChangeAction.Add)
                {
                    if (!UnmatchedTasks.Contains(task.opaque_ref))
                    {
                        task.PropertyChanged += Task_PropertyChanged;
                        UnmatchedTasks.Add(task.opaque_ref);
                    }
                }
                else if (e.Action == CollectionChangeAction.Remove)
                {
                    task.PropertyChanged -= Task_PropertyChanged;
                    if (MatchedTasks.TryGetValue(task.opaque_ref, out MeddlingAction a))
                        a.Update(task, true);

                    UnmatchedTasks.Remove(task.opaque_ref);
                    MatchedTasks.Remove(task.opaque_ref);
                }
                else
                {
                    log.DebugFormat($"Unmatched action from sender -- Action: {e.Action}; Task: {task.opaque_ref}");
                }
            }
        }

        public static void ForceAddTask(Task task)
        {
            TaskCollectionChanged(task, new CollectionChangeEventArgs(CollectionChangeAction.Add, task));
        }

        public static void Task_PropertyChanged(object sender, PropertyChangedEventArgs e)
        {
            Task task = (Task)sender;
            lock (DictionaryLock)
            {
                if (UnmatchedTasks.Contains(task.opaque_ref))
                {
                    if (MeddlingAction.IsTaskUnwanted(task))
                    {
                        task.PropertyChanged -= Task_PropertyChanged;
                        UnmatchedTasks.Remove(task.opaque_ref);
                    }
                    else if (MeddlingAction.IsTaskSuitable(task))
                    {
                        var a = new MeddlingAction(task);
                        UnmatchedTasks.Remove(task.opaque_ref);
                        MatchedTasks[task.opaque_ref] = a;
                    }
                    else
                    {
                        log.DebugFormat("Unmatched meddling task skipped -- " + task.opaque_ref);
                    }
                }
                else if (MatchedTasks.TryGetValue(task.opaque_ref, out MeddlingAction a))
                {
                    if (task.status == task_status_type.success)
                    {
                        task.PropertyChanged -= Task_PropertyChanged;
                        a.Update(task, true);
                        MatchedTasks.Remove(task.opaque_ref);
                    }
                    else
                    {
                        a.Update(task, false);
                    }
                }
                else
                {
                    // else - it is a hidden (etc..) task that has called already and been removed from unmatched 
                    //(and not put into matched) - so ignore it
                    log.DebugFormat("Uncategorised meddling task skipped -- " + task.opaque_ref);
                }
            }
        }
    }
}