// Copyright (c) AlphaSierraPapa for the SharpDevelop Team (for details please see \doc\copyright.txt)
// This code is distributed under the GNU LGPL (for details please see \doc\license.txt)

using System;
using System.Collections.Generic;
using System.Collections.ObjectModel;
using System.Collections.Specialized;
using System.Diagnostics;
using System.Globalization;
using System.Linq;

using Tango.Scripting.Editors.Document;

namespace Tango.Scripting.Editors.Xml
{
	/// <summary>
	/// Abstact base class for all types
	/// </summary>
	public abstract class AXmlObject: TextSegment
	{
		/// <summary> Empty string.  The namespace used if there is no "xmlns" specified </summary>
		public static readonly string NoNamespace = string.Empty;
		
		/// <summary> Namespace for "xml:" prefix: "http://www.w3.org/XML/1998/namespace" </summary>
		public static readonly string XmlNamespace = "http://www.w3.org/XML/1998/namespace";
		
		/// <summary> Namesapce for "xmlns:" prefix: "http://www.w3.org/2000/xmlns/" </summary>
		public static readonly string XmlnsNamespace = "http://www.w3.org/2000/xmlns/";
		
		/// <summary> Parent node. </summary>
		/// <remarks>
		/// New cached items start with null parent.
		/// Cache constraint:
		///   If cached item has parent set, then the whole subtree must be consistent
		/// </remarks>
		public AXmlObject Parent { get; set; }
		
		/// <summary>
		/// Gets the document that has owns this object.
		/// Once set, it is not changed.  Not even set to null.
		/// </summary>
		internal AXmlDocument Document { get; set; }
		
		/// <summary> Creates new object </summary>
		protected AXmlObject()
		{
			this.LastUpdatedFrom = this;
		}
		
		/// <summary> Occurs before the value of any local properties changes.  Nested changes do not cause the event to occur </summary>
		public event EventHandler<AXmlObjectEventArgs> Changing;
		
		/// <summary> Occurs after the value of any local properties changed.  Nested changes do not cause the event to occur </summary>
		public event EventHandler<AXmlObjectEventArgs> Changed;
		
		/// <summary> Raises Changing event </summary>
		protected void OnChanging()
		{
			AXmlParser.Log("Changing {0}", this);
			if (Changing != null) {
				Changing(this, new AXmlObjectEventArgs() { Object = this } );
			}
			AXmlDocument doc = this.Document;
			if (doc != null) {
				doc.OnObjectChanging(this);
			}
			// As a convenience, also rasie an event for the parent element
			AXmlTag me = this as AXmlTag;
			if (me != null && (me.IsStartOrEmptyTag || me.IsEndTag) && me.Parent is AXmlElement) {
				me.Parent.OnChanging();
			}
		}
		
		/// <summary> Raises Changed event </summary>
		protected void OnChanged()
		{
			AXmlParser.Log("Changed {0}", this);
			if (Changed != null) {
				Changed(this, new AXmlObjectEventArgs() { Object = this } );
			}
			AXmlDocument doc = this.Document;
			if (doc != null) {
				doc.OnObjectChanged(this);
			}
			// As a convenience, also rasie an event for the parent element
			AXmlTag me = this as AXmlTag;
			if (me != null && (me.IsStartOrEmptyTag || me.IsEndTag) && me.Parent is AXmlElement) {
				me.Parent.OnChanged();
			}
		}
		
		List<SyntaxError> syntaxErrors;
		
		/// <summary>
		/// The error that occured in the context of this node (excluding nested nodes)
		/// </summary>
		public IEnumerable<SyntaxError> MySyntaxErrors {
			get {
				if (syntaxErrors == null) {
					return new SyntaxError[] {};
				} else {
					return syntaxErrors;
				}
			}
		}
		
		/// <summary>
		/// The error that occured in the context of this node and all nested nodes.
		/// It has O(n) cost.
		/// </summary>
		public IEnumerable<SyntaxError> SyntaxErrors {
			get {
				return GetSelfAndAllChildren().SelectMany(obj => obj.MySyntaxErrors);
			}
		}
		
		internal void AddSyntaxError(SyntaxError error)
		{
			DebugAssert(error.Object == this, "Must own the error");
			if (this.syntaxErrors == null) this.syntaxErrors = new List<SyntaxError>();
			syntaxErrors.Add(error);
		}
		
		/// <summary> Throws exception if condition is false </summary>
		/// <remarks> Present in release mode - use only for very cheap aserts </remarks>
		protected static void Assert(bool condition, string message)
		{
			if (!condition) {
				throw new InternalException("Assertion failed: " + message);
			}
		}
		
		/// <summary> Throws exception if condition is false </summary>
		[Conditional("DEBUG")]
		protected static void DebugAssert(bool condition, string message)
		{
			if (!condition) {
				throw new InternalException("Assertion failed: " + message);
			}
		}
		
		/// <summary> Recursively gets self and all nested nodes. </summary>
		[System.Diagnostics.CodeAnalysis.SuppressMessage("Microsoft.Design", "CA1024:UsePropertiesWhereAppropriate",
		                                                 Justification = "Using a method makes the API look more LINQ-like and indicates that the returned collection is computed every time.")]
		public virtual IEnumerable<AXmlObject> GetSelfAndAllChildren()
		{
			return new AXmlObject[] { this };
		}
		
		/// <summary> Get all ancestors of this node </summary>
		[System.Diagnostics.CodeAnalysis.SuppressMessage("Microsoft.Design", "CA1024:UsePropertiesWhereAppropriate",
		                                                 Justification = "Using a method makes the API look more LINQ-like and indicates that the returned collection is computed every time.")]
		public IEnumerable<AXmlObject> GetAncestors()
		{
			AXmlObject curr = this.Parent;
			while(curr != null) {
				yield return curr;
				curr = curr.Parent;
			}
		}
		
		/// <summary> Call appropriate visit method on the given visitor </summary>
		public abstract void AcceptVisitor(IAXmlVisitor visitor);
		
		/// <summary> The parser tree object this object was updated from </summary>
		/// <remarks> Initialized to 'this' </remarks>
		internal AXmlObject LastUpdatedFrom { get; private set; }
		
		internal bool IsCached { get; set; }
		
		/// <summary> Is call to UpdateDataFrom is allowed? </summary>
		internal bool CanUpdateDataFrom(AXmlObject source)
		{
			return
				this.GetType() == source.GetType() &&
				this.StartOffset == source.StartOffset &&
				(this.LastUpdatedFrom == source || !this.IsCached);
		}
		
		/// <summary> Copy all data from the 'source' to this object </summary>
		/// <remarks> Returns true if any updates were done </remarks>
		internal virtual bool UpdateDataFrom(AXmlObject source)
		{
			Assert(this.GetType() == source.GetType(), "Source has different type");
			DebugAssert(this.StartOffset == source.StartOffset, "Source has different StartOffset");
			
			if (this.LastUpdatedFrom == source) {
				DebugAssert(this.EndOffset == source.EndOffset, "Source has different EndOffset");
				return false;
			}
			
			Assert(!this.IsCached, "Can not update cached item");
			Assert(source.IsCached, "Must update from cache");
			
			this.LastUpdatedFrom = source;
			this.StartOffset = source.StartOffset;
			// In some cases we are just updating objects of that same
			// type and position and hoping to be luckily right
			this.EndOffset = source.EndOffset;
			
			// Do not bother comparing - assume changed if non-null
			if (this.syntaxErrors != null || source.syntaxErrors != null) {
				// May be called again in derived class - oh, well, does not matter
				OnChanging();
				this.Document.Parser.TrackedSegments.RemoveSyntaxErrorsOf(this);
				if (source.syntaxErrors == null) {
					this.syntaxErrors = null;
				} else {
					this.syntaxErrors = new List<SyntaxError>();
					foreach(var error in source.MySyntaxErrors) {
						// The object differs, so create our own copy
						// The source still might need it in the future and we do not want to break it
						this.AddSyntaxError(error.Clone(this));
					}
				}
				this.Document.Parser.TrackedSegments.AddSyntaxErrorsOf(this);
				OnChanged();
			}
			
			return true;
		}
		
		/// <summary> Verify that the item is consistent.  Only in debug build. </summary>
		[Conditional("DEBUG")]
		internal virtual void DebugCheckConsistency(bool allowNullParent)
		{
			
		}
		
		/// <inheritdoc/>
		public override string ToString()
		{
			return string.Format(CultureInfo.InvariantCulture, "{0}({1}-{2})", this.GetType().Name.Remove(0, 4), this.StartOffset, this.EndOffset);
		}
		
		#region Helpper methods
		
		/// <summary> The part of name before ":" </summary>
		/// <returns> Empty string if not found </returns>
		protected static string GetNamespacePrefix(string name)
		{
			if (string.IsNullOrEmpty(name)) return string.Empty;
			int colonIndex = name.IndexOf(':');
			if (colonIndex != -1) {
				return name.Substring(0, colonIndex);
			} else {
				return string.Empty;
			}
		}
		
		/// <summary> The part of name after ":" </summary>
		/// <returns> Whole name if ":" not found </returns>
		protected static string GetLocalName(string name)
		{
			if (string.IsNullOrEmpty(name)) return string.Empty;
			int colonIndex = name.IndexOf(':');
			if (colonIndex != -1) {
				return name.Remove(0, colonIndex + 1);
			} else {
				return name ?? string.Empty;
			}
		}
		
		#endregion
	}
}