GroupNode.cs

using System;
using System.Collections.Generic;
using System.Text;
using System.Threading.Tasks;
using Waher.Events;
using Waher.Groups.Commands;
using Waher.Persistence;
using Waher.Persistence.Attributes;
using Waher.Persistence.Filters;
using Waher.Runtime.Collections;
using Waher.Runtime.Language;
using Waher.Runtime.Threading;
using Waher.Things;
using Waher.Things.Attributes;
using Waher.Things.DisplayableParameters;
using Waher.Things.SourceEvents;
 
namespace Waher.Groups
{
    [CollectionName("Groups")]
    [TypeName(TypeNameSerialization.FullName)]
    [ArchivingTime]
    [Index("NodeId")]
    [Index("ParentId", "NodeId")]
    public abstract class GroupNode : IGroupNode
    {
        private Guid objectId = Guid.Empty;
        private Guid parentId = Guid.Empty;
        private GroupNode parent = null;
        private string nodeId = string.Empty;
        private string oldId = null;
        private NodeState state = NodeState.None;
        private List<GroupNode> children = null;
        private int siblingOrdinal = 0;
        private bool childrenLoaded = false;
        private readonly object synchObject = new object();
        private DateTime created = DateTime.Now;
        private DateTime updated = DateTime.MinValue;
        private ThingReference thingReference = null;
 
        public GroupNode()
        {
        }
 
        public static implicit operator ThingReference(GroupNode Node)
        {
            Node.thingReference ??= new ThingReference(Node.nodeId, Node.SourceId, Node.Partition);
 
            return Node.thingReference;
        }
 
        public override bool Equals(object obj)
        {
            if (!(obj is IThingReference Ref))
                return false;
            else
                return this.nodeId == Ref.NodeId && this.SourceId == Ref.SourceId && this.Partition == Ref.Partition;
        }
 
        public override int GetHashCode()
        {
            return this.nodeId.GetHashCode() ^
                this.SourceId.GetHashCode() ^
                this.Partition.GetHashCode();
        }
 
        [ObjectId]
        public Guid ObjectId
        {
            get => this.objectId;
            set => this.objectId = value;
        }
 
        public Guid ParentId
        {
            get => this.parentId;
            set => this.parentId = value;
        }
 
        public DateTime Created
        {
            get => this.created;
            set => this.created = value;
        }
 
        [DefaultValueDateTimeMinValue]
        public DateTime Updated
        {
            get => this.updated;
            set => this.updated = value;
        }
 
        [DefaultValue(0)]
        public int SiblingOrdinal
        {
            get => this.siblingOrdinal;
            set => this.siblingOrdinal = value;
        }
 
        [Header(2, "Group ID:", 0)]
        [Page(3, "Group", 0)]
        [ToolTip(4, "Group identity in the collection of groups.")]
        [Required]
        public string NodeId
        {
            get => this.nodeId;
            set
            {
                this.nodeId = value;
                this.thingReference = null;
 
                if (this.oldId is null && !string.IsNullOrEmpty(value))
                    this.oldId = value;
            }
        }
 
        [IgnoreMember]
        public string SourceId => GroupSource.SourceID;
 
        [IgnoreMember]
        public string Partition => string.Empty;
 
        public override string ToString()
        {
            StringBuilder sb = new StringBuilder();
            Language Language = Translator.GetDefaultLanguageAsync().Result;
 
            sb.Append(this.nodeId);
            sb.Append(" (");
            sb.Append(this.GetTypeNameAsync(Language).Result);
            sb.Append(")");
 
            foreach (Parameter P in this.GetDisplayableParametersAsync(Language, RequestOrigin.Empty).Result)
            {
                sb.Append(", ");
                sb.Append(P.Name);
                sb.Append("=");
                sb.Append(P.StringValue);
            }
 
            return sb.ToString();
        }
 
        public virtual Task LogErrorAsync(string Body)
        {
            return this.LogMessageAsync(MessageType.Error, string.Empty, Body);
        }
 
        public virtual Task LogErrorAsync(string EventId, string Body)
        {
            return this.LogMessageAsync(MessageType.Error, EventId, Body);
        }
 
        public virtual Task LogWarningAsync(string Body)
        {
            return this.LogMessageAsync(MessageType.Warning, string.Empty, Body);
        }
 
        public virtual Task LogWarningAsync(string EventId, string Body)
        {
            return this.LogMessageAsync(MessageType.Warning, EventId, Body);
        }
 
        public virtual Task LogInformationAsync(string Body)
        {
            return this.LogMessageAsync(MessageType.Information, string.Empty, Body);
        }
 
        public virtual Task LogInformationAsync(string EventId, string Body)
        {
            return this.LogMessageAsync(MessageType.Information, EventId, Body);
        }
 
        public virtual Task LogMessageAsync(MessageType Type, string Body)
        {
            return this.LogMessageAsync(Type, string.Empty, Body);
        }
 
        public virtual async Task LogMessageAsync(MessageType Type, string EventId, string Body)
        {
            if (this.objectId == Guid.Empty)
                return;
 
            bool Updated = false;
 
            foreach (GroupMessage Message in await Database.Find<GroupMessage>(new FilterAnd(
                new FilterFieldEqualTo("NodeId", this.objectId),
                new FilterFieldEqualTo("Type", Type),
                new FilterFieldEqualTo("EventId", EventId),
                new FilterFieldEqualTo("Body", Body))))
            {
                Message.Updated = DateTime.Now;
                Message.Count++;
 
                await Database.Update(Message);
                Updated = true;
 
                break;
            }
 
            if (!Updated)
            {
                GroupMessage Msg = new GroupMessage(this.objectId, DateTime.Now, Type, EventId, Body)
                {
                    NodeId = this.objectId
                };
 
                await Database.Insert(Msg);
            }
 
            switch (Type)
            {
                case MessageType.Error:
                    if (this.state < NodeState.ErrorUnsigned)
                    {
                        this.state = NodeState.ErrorUnsigned;
                        await Database.Update(this);
                        await this.RaiseUpdate();
                    }
                    break;
 
                case MessageType.Warning:
                    if (this.state < NodeState.WarningUnsigned)
                    {
                        this.state = NodeState.WarningUnsigned;
                        await Database.Update(this);
                        await this.RaiseUpdate();
                    }
                    break;
 
                case MessageType.Information:
                    if (this.state < NodeState.Information)
                    {
                        this.state = NodeState.Information;
                        await Database.Update(this);
                        await this.RaiseUpdate();
                    }
                    break;
            }
 
            switch (Type)
            {
                case MessageType.Information:
                    Log.Informational(Body, this.nodeId, string.Empty, EventId, EventLevel.Minor);
                    break;
 
                case MessageType.Warning:
                    Log.Warning(Body, this.nodeId, string.Empty, EventId, EventLevel.Minor);
                    break;
 
                case MessageType.Error:
                    Log.Error(Body, this.nodeId, string.Empty, EventId, EventLevel.Minor);
                    break;
            }
 
            await this.NodeStateChanged();
        }
 
        internal async Task NodeStateChanged()
        {
            await GroupSource.NewEvent(new NodeStatusChanged()
            {
                Messages = await this.GetMessageArrayAsync(RequestOrigin.Empty),
                State = this.state,
                NodeId = this.NodeId,
                Partition = this.Partition,
                SourceId = this.SourceId,
                Timestamp = DateTime.UtcNow
            });
        }
 
        public virtual Task<bool> RemoveErrorAsync()
        {
            return this.RemoveMessageAsync(MessageType.Error, string.Empty);
        }
 
        public virtual Task<bool> RemoveErrorAsync(string EventId)
        {
            return this.RemoveMessageAsync(MessageType.Error, EventId);
        }
 
        public virtual Task<bool> RemoveWarningAsync()
        {
            return this.RemoveMessageAsync(MessageType.Warning, string.Empty);
        }
 
        public virtual Task<bool> RemoveWarningAsync(string EventId)
        {
            return this.RemoveMessageAsync(MessageType.Warning, EventId);
        }
 
        public virtual Task<bool> RemoveInformationAsync()
        {
            return this.RemoveMessageAsync(MessageType.Information, string.Empty);
        }
 
        public virtual Task<bool> RemoveInformationAsync(string EventId)
        {
            return this.RemoveMessageAsync(MessageType.Information, EventId);
        }
 
        public virtual Task<bool> RemoveMessageAsync(MessageType Type)
        {
            return this.RemoveMessageAsync(Type, string.Empty);
        }
 
        public virtual async Task<bool> RemoveMessageAsync(MessageType Type, string EventId)
        {
            if (this.objectId == Guid.Empty)
                return false;
 
            bool Removed = false;
 
            foreach (GroupMessage Message in await Database.FindDelete<GroupMessage>(new FilterAnd(
                new FilterFieldEqualTo("NodeId", this.objectId),
                new FilterFieldEqualTo("Type", Type),
                new FilterFieldEqualTo("EventId", EventId))))
            {
                Removed = true;
 
                switch (Type)
                {
                    case MessageType.Error:
                        Log.Informational("Error removed: " + Message.Body, this.nodeId, string.Empty, string.Empty, EventLevel.Minor);
                        break;
 
                    case MessageType.Warning:
                        Log.Informational("Warning removed: " + Message.Body, this.nodeId, string.Empty, string.Empty, EventLevel.Minor);
                        break;
                }
            }
 
            if (Removed)
            {
                bool ErrorsFound = false;
                bool WarningsFound = false;
                bool InformationFound = false;
 
                foreach (GroupMessage Message in await Database.Find<GroupMessage>(new FilterFieldEqualTo("NodeId", this.objectId)))
                {
                    switch (Type)
                    {
                        case MessageType.Error:
                            ErrorsFound = true;
                            break;
 
                        case MessageType.Warning:
                            WarningsFound = true;
                            break;
 
                        case MessageType.Information:
                            InformationFound = true;
                            break;
                    }
                }
 
                NodeState NewStateSigned;
                NodeState NewStateUnsigned;
 
                if (ErrorsFound)
                {
                    NewStateSigned = NodeState.ErrorSigned;
                    NewStateUnsigned = NodeState.ErrorUnsigned;
                }
                else if (WarningsFound)
                {
                    NewStateSigned = NodeState.WarningSigned;
                    NewStateUnsigned = NodeState.WarningUnsigned;
                }
                else if (InformationFound)
                {
                    NewStateSigned = NodeState.Information;
                    NewStateUnsigned = NodeState.Information;
                }
                else
                {
                    NewStateSigned = NodeState.None;
                    NewStateUnsigned = NodeState.None;
                }
 
                switch (this.state)
                {
                    case NodeState.ErrorSigned:
                    case NodeState.WarningSigned:
                        if (this.state != NewStateSigned)
                        {
                            this.state = NewStateSigned;
                            await Database.Update(this);
                            await this.RaiseUpdate();
                        }
                        break;
 
                    default:
                        if (this.state != NewStateUnsigned)
                        {
                            this.state = NewStateUnsigned;
                            await Database.Update(this);
                            await this.RaiseUpdate();
                        }
                        break;
                }
 
                await this.NodeStateChanged();
            }
 
            return Removed;
        }
 
        public event EventHandlerAsync OnUpdate = null;
 
        internal Task RaiseUpdate()
        {
            return this.OnUpdate.Raise(this, EventArgs.Empty);
        }
 
        public static async Task<string> GetUniqueGroupId(string GroupId)
        {
            using Semaphore Semaphore = await Semaphores.BeginWrite("Groups." + GroupId);
            string Suffix = string.Empty;
            string s;
 
            int i = 1;
 
            while (true)
            {
                if (await Database.FindFirstIgnoreRest<GroupNode>(
                    new FilterFieldEqualTo("NodeId", s = GroupId + Suffix)) is null)
                {
                    return s;
                }
 
                i++;
                Suffix = " (" + i.ToString() + ")";
            }
        }
 
        #region INode
 
        [IgnoreMember]
        public virtual string LocalId => this.NodeId;
 
        [IgnoreMember]
        public virtual string LogId => this.NodeId;
 
        public abstract Task<string> GetTypeNameAsync(Language Language);
 
        [IgnoreMember]
        public bool HasChildren
        {
            get
            {
                if (!this.childrenLoaded)
                    this.LoadChildren().Wait();
 
                return !(this.children is null) && this.children.Count > 0;
            }
        }
 
        public virtual bool ChildrenOrdered => false;
 
        [IgnoreMember]
        public virtual bool IsReadable => this is ISensor;
 
        [IgnoreMember]
        public virtual bool IsControllable => this is IActuator;
 
        [IgnoreMember]
        public virtual bool HasCommands => true;
 
        [IgnoreMember]
        [Obsolete("Use the asynchronous GetParent() method instead.")]
        public INode Parent => this.GetParent().Result;
 
        public async Task<INode> GetParent()
        {
            if (!(this.parent is null))
                return this.parent;
 
            if (this.parentId == Guid.Empty)
                return null;
 
            this.parent = await this.LoadParent();
            if (this.parent is null)
                throw new Exception("Parent not found.");
 
            return this.parent;
        }
 
        public async Task<T> GetAncestor<T>()
            where T : INode
        {
            INode Loop = await this.GetParent();
 
            while (!(Loop is null))
            {
                if (Loop is T Ancestor)
                    return Ancestor;
                else if (Loop is GroupNode GroupNode)
                    Loop = await GroupNode.GetParent();
                else
                    Loop = Loop.Parent;
            }
 
            return default;
        }
 
        [IgnoreMember]
        public DateTime LastChanged
        {
            get
            {
                if (this.updated == DateTime.MinValue)
                    return this.created;
                else
                    return this.updated;
            }
        }
 
        [DefaultValue(NodeState.None)]
        public NodeState State
        {
            get => this.state;
            set => this.state = value;
        }
 
        [IgnoreMember]
        public Task<IEnumerable<INode>> ChildNodes
        {
            get
            {
                return this.GetChildNodes();
            }
        }
 
        private async Task<IEnumerable<INode>> GetChildNodes()
        {
            if (!this.childrenLoaded)
                await this.LoadChildren();
 
            lock (this.synchObject)
            {
                if (this.children is null)
                    return Array.Empty<INode>();
                else
                    return this.children.ToArray();
            }
        }
 
        private async Task LoadChildren()
        {
            List<GroupNode> Children = new List<GroupNode>();
            GroupNode[] ToUpdate = null;
 
            foreach (GroupNode Node in await Database.Find<GroupNode>(
                new FilterFieldEqualTo("ParentId", this.objectId)))
            {
                Children.Add(GroupSource.RegisterNode(Node));
            }
 
            lock (this.synchObject)
            {
                this.children = null;
 
                if (Children.Count > 0)
                {
                    foreach (GroupNode Child in Children)
                        Child.parent = this;
 
                    ToUpdate = this.SortChildrenAfterLoadLocked(Children);
                    this.children = Children;
                }
 
                this.childrenLoaded = true;
            }
 
            if (!(ToUpdate is null))
                await Database.Update(ToUpdate);
        }
 
        protected virtual GroupNode[] SortChildrenAfterLoadLocked(List<GroupNode> Children)
        {
            if (this.ChildrenOrdered)
            {
                Children.Sort((n1, n2) => n1.siblingOrdinal.CompareTo(n2.siblingOrdinal));
                return this.CheckOrderLocked(Children);
            }
            else
            {
                Children.Sort((n1, n2) => n1.nodeId.CompareTo(n2.nodeId));
                return null;
            }
        }
 
        protected virtual GroupNode[] CheckOrderLocked(List<GroupNode> Children)
        {
            if (this.ChildrenOrdered)
            {
                ChunkedList<GroupNode> ToUpdate = null;
                int Expected = 0;
 
                foreach (GroupNode Child in Children)
                {
                    if (Child.SiblingOrdinal != Expected)
                    {
                        ToUpdate ??= new ChunkedList<GroupNode>();
                        ToUpdate.Add(Child);
                        Child.siblingOrdinal = Expected;
                    }
 
                    Expected++;
                }
                return ToUpdate?.ToArray();
            }
            else
                return null;
        }
 
        internal async Task<GroupNode> LoadParent()
        {
            if (!(this.parent is null))
                return this.parent;
 
            if (this.parentId == Guid.Empty)
                return null;
 
            this.parent = await Database.LoadObject<GroupNode>(this.parentId);
            GroupSource.RegisterNode(this.parent);
 
            return this.parent;
        }
 
        public virtual Task<bool> CanViewAsync(RequestOrigin Caller)
        {
            return Task.FromResult(Caller.HasPrivilege("Source." + GroupSource.SourceID + ".Node.View"));
        }
 
        public virtual Task<bool> CanEditAsync(RequestOrigin Caller)
        {
            return Task.FromResult(Caller.HasPrivilege("Source." + GroupSource.SourceID + ".Node.Edit"));
        }
 
        public virtual Task<bool> CanAddAsync(RequestOrigin Caller)
        {
            return Task.FromResult(Caller.HasPrivilege("Source." + GroupSource.SourceID + ".Node.Add"));
        }
 
        public virtual Task<bool> CanDestroyAsync(RequestOrigin Caller)
        {
            return Task.FromResult(Caller.HasPrivilege("Source." + GroupSource.SourceID + ".Node.Destroy"));
        }
 
        public virtual async Task<IEnumerable<Parameter>> GetDisplayableParametersAsync(Language Language, RequestOrigin Caller)
        {
            Namespace Namespace = await Language.GetNamespaceAsync(typeof(GroupNode).Namespace)
                ?? await Language.CreateNamespaceAsync(typeof(GroupNode).Namespace);
 
            LinkedList<Parameter> Result = new LinkedList<Parameter>();
            Result.AddLast(new StringParameter("NodeId", await Namespace.GetStringAsync(5, "Group ID"), this.nodeId));
            Result.AddLast(new StringParameter("Type", await Namespace.GetStringAsync(6, "Type"), await this.GetTypeNameAsync(Language)));
 
            if (!(this.parent is null))
                Result.AddLast(new StringParameter("ParentId", await Namespace.GetStringAsync(7, "Parent ID"), this.parent.nodeId));
 
            if (!this.childrenLoaded)
                await this.LoadChildren();
 
            if (!(this.children is null))
            {
                int i;
 
                lock (this.synchObject)
                {
                    i = this.children.Count;
                }
 
                Result.AddLast(new Int32Parameter("NrChildren", await Namespace.GetStringAsync(8, "#Children"), i));
            }
 
            string s = this.state switch
            {
                NodeState.Information => await Namespace.GetStringAsync(9, "Information"),
                NodeState.WarningUnsigned => await Namespace.GetStringAsync(10, "Unsigned Warning"),
                NodeState.WarningSigned => await Namespace.GetStringAsync(11, "Warning"),
                NodeState.ErrorUnsigned => await Namespace.GetStringAsync(12, "Unsigned Error"),
                NodeState.ErrorSigned => await Namespace.GetStringAsync(13, "Error"),
                _ => null,
            };
 
            if (!string.IsNullOrEmpty(s))
                Result.AddLast(new StringParameter("State", await Namespace.GetStringAsync(14, "State"), s));
 
            Result.AddLast(new DateTimeParameter("Created", await Namespace.GetStringAsync(15, "Created"), this.created));
 
            if (this.updated != DateTime.MinValue)
                Result.AddLast(new DateTimeParameter("Updated", await Namespace.GetStringAsync(16, "Updated"), this.updated));
 
            return Result;
        }
 
        public async Task<Parameter[]> GetDisplayableParameterAraryAsync(Language Language, RequestOrigin Caller)
        {
            ChunkedList<Parameter> Result = new ChunkedList<Parameter>();
            Result.AddRange(await this.GetDisplayableParametersAsync(Language, Caller));
            return Result.ToArray();
        }
 
        public virtual async Task<IEnumerable<Message>> GetMessagesAsync(RequestOrigin Caller)
        {
            IEnumerable<GroupMessage> Messages = await Database.Find<GroupMessage>(
                new FilterFieldEqualTo("NodeId", this.objectId), "Created");
            LinkedList<Message> Result = new LinkedList<Message>();
 
            foreach (GroupMessage Msg in Messages)
                Result.AddLast(new Message(Msg.Created, Msg.Type, Msg.EventId, Msg.Body));  // TODO: Include Updated & Count also.
 
            return Result;
        }
 
        public async Task<Message[]> GetMessageArrayAsync(RequestOrigin Caller)
        {
            List<Message> Result = new List<Message>();
 
            foreach (Message Msg in await this.GetMessagesAsync(Caller))
                Result.Add(Msg);
 
            return Result.ToArray();
        }
 
        public virtual async Task<bool> MoveUpAsync(RequestOrigin Caller)
        {
            if (!(await this.GetParent() is GroupNode Parent))
                return false;
            else
                return await Parent.MoveUpAsync(this, Caller);
        }
 
        public virtual async Task<bool> MoveDownAsync(RequestOrigin Caller)
        {
            if (!(await this.GetParent() is GroupNode Parent))
                return false;
            else
                return await Parent.MoveDownAsync(this, Caller);
        }
 
        public virtual async Task<bool> MoveUpAsync(GroupNode Child, RequestOrigin Caller)
        {
            if (!this.ChildrenOrdered)
                return false;
 
            if (!this.childrenLoaded)
                await this.LoadChildren();
 
            if (this.children is null)
                return false;
 
            if (!await this.CanEditAsync(Caller) || !await Child.CanEditAsync(Caller))
                return false;
 
            GroupNode Child2;
 
            lock (this.children)
            {
                int i = this.children.IndexOf(Child);
                if (i <= 0)
                    return false;
 
                Child2 = this.children[i - 1];
 
                this.children.RemoveAt(i);
                this.children.Insert(i - 1, Child);
 
                i = Child.siblingOrdinal;
                Child.siblingOrdinal = Child2.siblingOrdinal;
                Child2.siblingOrdinal = i;
            }
 
            await Database.Update(Child, Child2);
 
            await GroupSource.NewEvent(new NodeMovedUp()
            {
                NodeId = Child.NodeId,
                Partition = Child.Partition,
                SourceId = Child.SourceId,
                Timestamp = DateTime.UtcNow
            });
 
            return true;
        }
 
        public virtual async Task<bool> MoveDownAsync(GroupNode Child, RequestOrigin Caller)
        {
            if (!this.ChildrenOrdered)
                return false;
 
            if (!this.childrenLoaded)
                await this.LoadChildren();
 
            if (this.children is null)
                return false;
 
            if (!await this.CanEditAsync(Caller) || !await Child.CanEditAsync(Caller))
                return false;
 
            GroupNode Child2;
 
            lock (this.children)
            {
                int c = this.children.Count;
                int i = this.children.IndexOf(Child);
                if (i < 0 || i + 1 >= c)
                    return false;
 
                Child2 = this.children[i + 1];
 
                this.children.RemoveAt(i);
                this.children.Insert(i + 1, Child);
 
                i = Child.siblingOrdinal;
                Child.siblingOrdinal = Child2.siblingOrdinal;
                Child2.siblingOrdinal = i;
            }
 
            await Database.Update(Child, Child2);
 
            await GroupSource.NewEvent(new NodeMovedDown()
            {
                NodeId = Child.NodeId,
                Partition = Child.Partition,
                SourceId = Child.SourceId,
                Timestamp = DateTime.UtcNow
            });
 
            return true;
        }
 
        public abstract Task<bool> AcceptsParentAsync(INode Parent);
 
        public abstract Task<bool> AcceptsChildAsync(INode Child);
 
        public virtual async Task AddAsync(INode Child)
        {
            if (!(Child is GroupNode Node))
                throw new Exception("Child must be a group node.");
 
            if (this.objectId == Guid.Empty)
                throw new Exception("Parent node must be persisted before you can add nodes to it.");
 
            if (!this.childrenLoaded)
                await this.LoadChildren();
 
            Node.parentId = this.objectId;
 
            GroupNode[] ToUpdate;
            GroupNode After = null;
            int c;
 
            lock (this.synchObject)
            {
                if (this.children is null)
                    this.children = new List<GroupNode>();
                else if ((c = this.children.Count) > 0)
                    After = this.children[c - 1];
 
                ToUpdate = this.CheckOrderLocked(this.children);
 
                Node.siblingOrdinal = this.children.Count;
                Node.parent = this;
 
                this.children.Add(Node);
            }
 
            if (!(ToUpdate is null))
                await Database.Update(ToUpdate);
 
            if (Node.objectId == Guid.Empty)
            {
                await Database.Insert(Node);
                GroupSource.RegisterNode(Node);
 
                Language Language = await Translator.GetDefaultLanguageAsync();
                NodeAdded Event = new NodeAdded()
                {
                    Parameters = await Node.GetDisplayableParameterAraryAsync(Language, RequestOrigin.Empty),
                    NodeType = Node.GetType().FullName,
                    Sniffable = false,
                    DisplayName = await Node.GetTypeNameAsync(Language),
                    HasChildren = Node.HasChildren,
                    ChildrenOrdered = Node.ChildrenOrdered,
                    IsReadable = Node.IsReadable,
                    IsControllable = Node.IsControllable,
                    HasCommands = Node.HasCommands,
                    ParentId = this.NodeId,
                    ParentPartition = this.Partition,
                    Updated = Node.Updated,
                    State = Node.State,
                    NodeId = Node.NodeId,
                    Partition = Node.Partition,
                    LogId = NodeAdded.EmptyIfSame(Node.LogId, Node.NodeId),
                    LocalId = NodeAdded.EmptyIfSame(Node.LocalId, Node.NodeId),
                    SourceId = Node.SourceId,
                    Timestamp = DateTime.UtcNow
                };
 
                if (this.ChildrenOrdered && !(After is null))
                {
                    Event.AfterNodeId = After.nodeId;
                    Event.AfterPartition = After.Partition;
                }
 
                await GroupSource.NewEvent(Event);
            }
            else
                await Node.NodeUpdated();
 
            await this.RaiseUpdate();
        }
 
        protected virtual async Task NodeUpdated()
        {
            this.updated = DateTime.Now;
            await Database.Update(this);
 
            await GroupSource.NewEvent(new NodeUpdated()
            {
                Parameters = await this.GetDisplayableParameterAraryAsync(await Translator.GetDefaultLanguageAsync(), RequestOrigin.Empty),
                HasChildren = this.HasChildren,
                ChildrenOrdered = this.ChildrenOrdered,
                IsReadable = this.IsReadable,
                IsControllable = this.IsControllable,
                HasCommands = this.HasCommands,
                ParentId = (await this.GetParent()).NodeId,
                ParentPartition = this.Partition,
                Updated = this.Updated,
                State = this.State,
                NodeId = this.NodeId,
                OldId = this.oldId,
                Partition = this.Partition,
                LogId = NodeAdded.EmptyIfSame(this.LogId, this.NodeId),
                LocalId = NodeAdded.EmptyIfSame(this.LocalId, this.NodeId),
                SourceId = this.SourceId,
                Timestamp = DateTime.UtcNow
            });
 
            if (this.oldId != this.nodeId)
            {
                GroupSource.RegisterNewNodeId(this, this.oldId);
                this.oldId = this.nodeId;
            }
        }
 
        public virtual async Task UpdateAsync()
        {
            if (this.objectId != Guid.Empty)
                await this.NodeUpdated();
 
            await this.RaiseUpdate();
        }
 
        public virtual async Task<bool> RemoveAsync(INode Child)
        {
            if (!(Child is GroupNode Node))
                throw new Exception("Child must be a group node.");
 
            if (!this.childrenLoaded)
                await this.LoadChildren();
 
            GroupNode[] ToUpdate = null;
            int i;
 
            lock (this.synchObject)
            {
                if (!(this.children is null))
                {
                    i = this.children.IndexOf(Node);
                    if (i >= 0)
                    {
                        this.children.RemoveAt(i);
                        if (i == 0 && this.children.Count == 0)
                            this.children = null;
                        else
                            ToUpdate = this.CheckOrderLocked(this.children);
                    }
                }
                else
                    i = -1;
            }
 
            if (!(ToUpdate is null))
                await Database.Update(ToUpdate);
 
            Node.parentId = Guid.Empty;
            Node.parent = null;
 
            if (Node.objectId != Guid.Empty)
            {
                await Database.Update(Child);
                await this.RaiseUpdate();
 
                await GroupSource.NewEvent(new NodeRemoved()
                {
                    NodeId = Node.NodeId,
                    Partition = Node.Partition,
                    SourceId = Node.SourceId,
                    Timestamp = DateTime.UtcNow
                });
            }
 
            return i >= 0;
        }
 
        public async virtual Task DestroyAsync()
        {
            if (!(await this.GetParent() is null))
            {
                if (this.parent.childrenLoaded)
                {
                    GroupNode[] ToUpdate = null;
 
                    lock (this.parent.synchObject)
                    {
                        if (!(this.parent.children is null))
                        {
                            if (this.parent.children.Remove(this))
                            {
                                if (this.parent.children.Count == 0)
                                    this.parent.children = null;
                                else
                                    ToUpdate = this.parent.CheckOrderLocked(this.parent.children);
                            }
                        }
                    }
 
                    if (!(ToUpdate is null))
                        await Database.Update(ToUpdate);
                }
            }
 
            if (!this.childrenLoaded)
                await this.LoadChildren();
 
            if (!(this.children is null))
            {
                List<GroupNode> Children = this.children;
                this.children = null;
 
                foreach (GroupNode Child in Children)
                {
                    Child.parent = null;
                    Child.parentId = Guid.Empty;
 
                    await Child.DestroyAsync();
                }
 
                this.children = null;
            }
 
            if (this.objectId != Guid.Empty)
            {
                await Database.Delete(this);
                this.objectId = Guid.Empty;
            }
 
            GroupSource.UnregisterNode(this);
        }
 
        [IgnoreMember]
        public virtual Task<IEnumerable<ICommand>> Commands
        {
            get
            {
                return Task.FromResult<IEnumerable<ICommand>>(new ICommand[]
                {
                    new ClearMessages(this),
                    new LogMessage(this)
                });
            }
        }
 
        #endregion
    }
}