//
// TreeNode.cs
//
// Author:
//   Lluis Sanchez Gual
//
// Copyright (C) 2007 Novell, Inc (http://www.novell.com)
//
// Permission is hereby granted, free of charge, to any person obtaining
// a copy of this software and associated documentation files (the
// "Software"), to deal in the Software without restriction, including
// without limitation the rights to use, copy, modify, merge, publish,
// distribute, sublicense, and/or sell copies of the Software, and to
// permit persons to whom the Software is furnished to do so, subject to
// the following conditions:
// 
// The above copyright notice and this permission notice shall be
// included in all copies or substantial portions of the Software.
// 
// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
// EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
// MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
// NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE
// LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION
// OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
// WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
//


using System;
using System.Text;
using System.Collections;
using Mono.Addins.Description;
using System.Collections.Generic;
using System.Collections.Immutable;
using System.Threading;

namespace Mono.Addins
{
	class TreeNode
	{
		ImmutableArray<TreeNode> children;

		ImmutableArray<TreeNode>.Builder childrenBuilder;
		ExtensionContextTransaction buildTransaction;

		ExtensionNode extensionNode;
		bool childrenFromExtensionsLoaded;
		string id;
		TreeNode parent;
		ExtensionNodeSet nodeTypes;
		ExtensionPoint extensionPoint;
		BaseCondition condition;
		protected AddinEngine addinEngine;

		public TreeNode (AddinEngine addinEngine, string id)
		{
			this.id = id;
			this.addinEngine = addinEngine;

			children = ImmutableArray<TreeNode>.Empty;

			// Root node
			if (id.Length == 0)
				childrenFromExtensionsLoaded = true;
		}
		
		public AddinEngine AddinEngine {
			get { return addinEngine; }
		}
		
		internal void AttachExtensionNode (ExtensionNode enode)
		{
			if (Interlocked.CompareExchange (ref extensionNode, enode, null) != null) {
				// Another thread already assigned the node
				return;
			}

			if (extensionNode != null)
				extensionNode.SetTreeNode (this);
		}
		
		public string Id {
			get { return id; }
		}
		
		public ExtensionNode ExtensionNode {
			get {
				if (extensionNode == null && extensionPoint != null) {
					var newNode = new ExtensionNode ();
					newNode.SetData (addinEngine, extensionPoint.RootAddin, null, null);
					AttachExtensionNode (newNode);
				}
				return extensionNode;
			}
		}

		public void NotifyAddinUnloaded ()
		{
			extensionNode?.NotifyAddinUnloaded ();
		}

		public void NotifyAddinLoaded ()
		{
			extensionNode?.NotifyAddinLoaded ();
		}

		public bool HasExtensionNode {
			get {
				return extensionNode != null || extensionPoint != null;
			}
		}

		public string AddinId {
			get {
				return extensionNode != null ? extensionNode.AddinId : extensionPoint?.RootAddin;
			}
		}

		public ExtensionPoint ExtensionPoint {
			get { return extensionPoint; }
			set { extensionPoint = value; }
		}
		
		public ExtensionNodeSet ExtensionNodeSet {
			get { return nodeTypes; }
			set { nodeTypes = value; }
		}
		
		public TreeNode Parent {
			get { return parent; }
		}
		
		public BaseCondition Condition {
			get { return condition; }
			set {
				condition = value;
			}
		}
		
		public virtual ExtensionContext Context {
			get {
				if (parent != null)
					return parent.Context;
				else
					return null;
			}
		}
		
		public bool IsEnabled {
			get {
				if (condition == null)
					return true;
				ExtensionContext ctx = Context;
				if (ctx == null)
					return true;
				else
					return condition.Evaluate (ctx);
			}
		}
		
		public bool ChildrenFromExtensionsLoaded {
			get { return childrenFromExtensionsLoaded; }
		}
		
		public void AddChildNode (ExtensionContextTransaction transaction, TreeNode node)
		{
			node.SetParent(transaction, this);

			if (childrenBuilder != null)
				childrenBuilder.Add (node);
			else
				children = children.Add (node);

			transaction.ReportChildrenChanged (this);
		}

		public void InsertChild (ExtensionContextTransaction transaction, int n, TreeNode node)
		{
			node.SetParent (transaction, this);

			if (childrenBuilder != null)
				childrenBuilder.Insert (n, node);
			else
				children = children.Insert (n, node);

			transaction.ReportChildrenChanged (this);
		}

		public void RemoveChild (ExtensionContextTransaction transaction, TreeNode node)
		{
			node.SetParent (transaction, null);

			if (childrenBuilder != null)
				childrenBuilder.Remove (node);
			else
				children = children.Remove (node);

			transaction.ReportChildrenChanged (this);
		}

		void SetParent (ExtensionContextTransaction transaction, TreeNode newParent)
		{
			if (parent == newParent)
				return;

			if (this.parent != null && newParent != null)
				throw new InvalidOperationException ("Node already has a parent");

			var currentCtx = Context;
			if (currentCtx != null && currentCtx != transaction.Context)
				throw new InvalidOperationException ("Invalid context");

			this.parent = newParent;

			if (newParent != null) {
				if (newParent.Context != null)
					OnAttachedToContext (transaction);
			} else {
				if (currentCtx != null)
					OnDetachedFromContext (transaction);
			}
		}

		void OnAttachedToContext (ExtensionContextTransaction transaction)
		{
			// Once the node is part of a context, let's register the condition
			if (Condition != null)
				transaction.RegisterNodeCondition (this, Condition);

			// Propagate event to children
			foreach (var child in GetLoadedChildren ())
				child.OnAttachedToContext (transaction);
		}

		void OnDetachedFromContext (ExtensionContextTransaction transaction)
		{
			// Node being removed, unregister from context
			if (Condition != null)
				transaction.UnregisterNodeCondition (this, Condition);

			// Propagate event to children
			foreach (var child in GetLoadedChildren ())
				child.OnDetachedFromContext (transaction);
		}

		public ExtensionNode GetExtensionNode (string path, string childId)
		{
			TreeNode node = GetNode (path, childId);
			return node != null ? node.ExtensionNode : null;
		}
		
		public ExtensionNode GetExtensionNode (string path)
		{
			TreeNode node = GetNode (path);
			return node != null ? node.ExtensionNode : null;
		}
		
		public TreeNode GetNode (string path, string childId)
		{
			if (childId == null || childId.Length == 0)
				return GetNode (path);
			else
				return GetNode (path + "/" + childId);
		}
		
		public TreeNode GetNode (string path)
		{
			return GetNode (path, false);
		}

		public TreeNode GetNode(string path, bool buildPath)
		{
			return GetNode(path, buildPath, null);
		}

		public TreeNode GetNode (string path, bool buildPath, ExtensionContextTransaction transaction)
		{
			if (path.StartsWith ("/"))
				path = path.Substring (1);

			string[] parts = path.Split ('/');
			TreeNode curNode = this;

			foreach (string part in parts) {
				curNode.EnsureChildrenLoaded(transaction);
				var node = curNode.GetChildNode (part);
				if (node != null) {
					curNode = node;
					continue;
				}
				
				if (buildPath) {
					transaction = BeginContextTransaction (transaction, out var dispose);
					try {
						// Check again inside the lock, just in case
						curNode.EnsureChildrenLoaded(transaction);
						node = curNode.GetChildNode (part);
						if (node != null) {
							curNode = node;
							continue;
						}

						TreeNode newNode = new TreeNode (addinEngine, part);
						curNode.AddChildNode (transaction, newNode);
						curNode = newNode;
					} finally {
						if (dispose)
							transaction.Dispose ();
					}
				} else
					return null;
			}
			return curNode;
		}

		public TreeNode GetChildNode (string id)
		{
			var childrenList = Children;
			foreach (var node in childrenList) {
				if (node.Id == id)
					return node;
			}
			return null;
		}

		public int IndexOfChild (string id)
		{
			var childrenList = Children;
			for (int n = 0; n < childrenList.Count; n++) {
				if (childrenList [n].Id == id)
					return n;
			}
			return -1;
		}

		public IReadOnlyList<TreeNode> Children {
			get {
				if (IsInChildrenUpdateTransaction) {
					return childrenBuilder;
				}
				EnsureChildrenLoaded(null);
				return (IReadOnlyList<TreeNode>)childrenBuilder ?? (IReadOnlyList<TreeNode>)children;
			}
		}

		void EnsureChildrenLoaded(ExtensionContextTransaction transaction)
		{
			if (IsInChildrenUpdateTransaction)
				return;

			if (!childrenFromExtensionsLoaded)
			{
				transaction = BeginContextTransaction(transaction, out var disposeTransaction);
				try
				{
					if (!childrenFromExtensionsLoaded)
					{
						if (extensionPoint != null)
						{
							BeginChildrenUpdateTransaction(transaction);
							Context.LoadExtensions(transaction, GetPath(), this);
							// We have to keep the reference to the extension point, since add-ins may be loaded/unloaded
						}
					}
				}
				finally
				{
					childrenFromExtensionsLoaded = true;
					if (disposeTransaction)
						transaction.Dispose();
				}
			}
		}

		IReadOnlyList<TreeNode> GetLoadedChildren ()
		{
			if (IsInChildrenUpdateTransaction)
				return childrenBuilder;
			else
				return children;
		}

		/// <summary>
		/// Returns true if the tree node has a child update transaction in progress,
		/// and the current thread is the one that created the transaction.
		/// </summary>
		bool IsInChildrenUpdateTransaction => childrenBuilder != null && Context.IsCurrentThreadInTransaction;

		ExtensionContextTransaction BeginContextTransaction (ExtensionContextTransaction currentTransaction, out bool dispose)
		{
			if (currentTransaction != null)
			{
				dispose = false;
				return currentTransaction;
			}
			else if (IsInChildrenUpdateTransaction) {
				dispose = false;
				return buildTransaction;
			} else {
				dispose = true;
				return Context.BeginTransaction ();
			}
		}

		public void BeginChildrenUpdateTransaction (ExtensionContextTransaction transaction)
		{
			// If a transaction already started, just reuse it
			if (buildTransaction != null)
				return;

			childrenBuilder = children.ToBuilder ();
			this.buildTransaction = transaction;

			transaction.RegisterChildrenUpdateTransaction (this);
		}

		internal void CommitChildrenUpdateTransaction ()
		{
			if (buildTransaction == null)
				throw new InvalidOperationException ("No transaction started");

			children = childrenBuilder.ToImmutable ();

			var transaction = buildTransaction;
			
			childrenBuilder = null;
			buildTransaction = null;

			transaction.ReportChildrenChanged (this);
		}

		public string GetPath ()
		{
			int num=0;
			TreeNode node = this;
			while (node != null) {
				num++;
				node = node.parent;
			}
			
			string[] ids = new string [num];
			
			node = this;
			while (node != null) {
				ids [--num] = node.id;
				node = node.parent;
			}
			return string.Join ("/", ids);
		}
		
		public void NotifyAddinLoaded (RuntimeAddin ad, bool recursive)
		{
			if (extensionNode != null && extensionNode.AddinId == ad.Addin.Id)
				extensionNode.NotifyAddinLoaded ();
			if (recursive && childrenFromExtensionsLoaded) {
				foreach (TreeNode node in Children)
					node.NotifyAddinLoaded (ad, true);
			}
		}
		
		public ExtensionPoint FindLoadedExtensionPoint (string path)
		{
			if (path.StartsWith ("/"))
				path = path.Substring (1);

			string[] parts = path.Split ('/');
			TreeNode curNode = this;

			foreach (string part in parts) {
				var node = curNode.GetChildNode (part);
				if (node != null) {
					curNode = node;
					if (!curNode.ChildrenFromExtensionsLoaded)
						return null;
					if (curNode.ExtensionPoint != null)
						return curNode.ExtensionPoint;
					continue;
				}
				return null;
			}
			return null;
		}
		
		public void FindAddinNodes (string id, List<TreeNode> nodes)
		{
			if (id != null && extensionPoint != null && extensionPoint.RootAddin == id) {
				// It is an extension point created by the add-in. All nodes below this
				// extension point will be added to the list, even if they come from other add-ins.
				id = null;
			}

			if (childrenFromExtensionsLoaded) {
				// Deep-first search, to make sure children are removed before the parent.
				foreach (TreeNode node in Children)
					node.FindAddinNodes (id, nodes);
			}
			
			if (id == null || AddinId == id)
				nodes.Add (this);
		}
		
		public bool NotifyChildrenChanged ()
		{
			if (extensionNode != null)
				return extensionNode.NotifyChildChanged ();
			else
				return false;
		}

		public void ResetCachedData (ExtensionContextTransaction transaction)
		{
			if (extensionPoint != null) {
				string aid = Addin.GetIdName (extensionPoint.ParentAddinDescription.AddinId);
				RuntimeAddin ad = addinEngine.GetAddin (transaction.GetAddinEngineTransaction(), aid);
				if (ad != null)
					extensionPoint = ad.Addin.Description.ExtensionPoints [GetPath ()];
			}
			if (childrenBuilder != null) {
				foreach (TreeNode cn in childrenBuilder)
					cn.ResetCachedData (transaction);
			}

			foreach (TreeNode cn in children)
				cn.ResetCachedData (transaction);
		}
	}
}