//
// mcs/class/System.Data/System.Data/XmlDiffLoader.cs
//
// Purpose: Loads XmlDiffGrams to DataSet 
//
// class: XmlDiffLoader
// assembly: System.Data.dll
// namespace: System.Data
//
// Author:
//     Ville Palo <vi64pa@koti.soon.fi>
//
// (c)copyright 2003 Ville Palo
//
using System;
using System.Data;
using System.Xml;
using System.Xml.XPath;
using System.Collections;
using System.Globalization;

namespace System.Data {

	internal class XmlDiffLoader 
	{

		#region Fields
		enum LoadType {CURRENT, BEFORE, ERROR};
		private DataSet DSet;
		private Hashtable DiffGrRows = new Hashtable ();
		private Hashtable ErrorRows = new Hashtable ();

		#endregion // Fields

		#region ctors

		public XmlDiffLoader (DataSet DSet) 
		{
			this.DSet = DSet;
		}

		#endregion //ctors

		#region Public methods

		public void Load (XmlReader Reader) 
		{

			XmlDocument Document = BuildXmlDocument(Reader);
			
			XPathNavigator Navigator = Document.CreateNavigator ();
			bool origEnforceConstraint = DSet.EnforceConstraints;
			DSet.EnforceConstraints = false;
			LoadBefore (Navigator);
			LoadCurrent (Navigator);
			LoadErrors (Navigator);
			DSet.EnforceConstraints = origEnforceConstraint;
		}

		#endregion // Public methods

		#region Private methods

		private void LoadCurrent (XPathNavigator Navigator) 
		{			
			Navigator.MoveToRoot ();

			if (Navigator.MoveToFirstChild ()) {

				if (Navigator.Name == "diffgr:diffgram") {

					if (Navigator.MoveToFirstChild ()) {

						if (Navigator.MoveToFirstChild ()) {
							do {
								if (DSet.Tables.Contains (Navigator.LocalName))
									LoadCurrentTable(Navigator);
								else 
									throw new DataException (Locale.GetText ("Cannot load diffGram. Table '" + Navigator.LocalName + "' is missing in the destination dataset"));	
							}while (Navigator.MoveToNext());
						}
					}
				}
			}
		}

		private void LoadBefore (XPathNavigator Navigator) 
		{
			Navigator.MoveToRoot ();

			if (!Navigator.MoveToFirstChild ())
				return; // FIXME: exception
			
			if (Navigator.Name != "diffgr:diffgram")
				return; // FIXME: exception

			if (Navigator.MoveToFirstChild ()) {

				while (Navigator.Name != "diffgr:before") {

					if (!Navigator.MoveToNext ()) // there is no before
						return;
				}

				if (Navigator.MoveToFirstChild ()) {

					do {
						if (DSet.Tables.Contains (Navigator.LocalName))
							LoadBeforeTable(Navigator);
						else
							throw new DataException (Locale.GetText ("Cannot load diffGram. Table '" + Navigator.LocalName + "' is missing in the destination dataset"));
					} while (Navigator.MoveToNext ());
				}
			}
		}				 
				
					   
		private void LoadErrors (XPathNavigator Navigator) 
		{
			Navigator.MoveToRoot ();

			if (!Navigator.MoveToFirstChild ())
				return; // FIXME: exception
			
			if (Navigator.Name != "diffgr:diffgram")
				return; // FIXME: exception

			if (Navigator.MoveToFirstChild ()) {
				
				while (Navigator.Name != "diffgr:errors") {
					if (!Navigator.MoveToNext ())
						return;
				}

				if (Navigator.MoveToFirstChild ()) {

					DataRow Row = null;

					// find the row in 'current' section
					if (Navigator.MoveToFirstAttribute ()) {

						do {
							if (Navigator.Name == "diffgr:id") {
								
								if (ErrorRows.Contains (Navigator.Value))
									Row = (DataRow)ErrorRows [Navigator.Value];
							}

						} while (Navigator.MoveToNextAttribute ());
						
						Navigator.MoveToParent ();						
					}

					if (Navigator.MoveToFirstChild ()) {

						string Error = "";
						
						do {
							if (Navigator.MoveToFirstAttribute ()) {
								do {
									if (Navigator.Name == "diffgr:Error")
										Error = Navigator.Value;

								} while (Navigator.MoveToNextAttribute ());
								
								Navigator.MoveToParent ();
							}

							Row.SetColumnError (Navigator.LocalName, Error);

						} while (Navigator.MoveToNext ());
					}
				}
			}
		}

		private void LoadColumns (DataTable Table, DataRow Row, XPathNavigator Navigator, bool NewRow, LoadType loadType) 
		{
			if (Navigator.MoveToFirstChild ()) {

				do {
					if (Table.Columns.Contains (Navigator.LocalName))
						Row [Navigator.LocalName] = Navigator.Value;
					else if (DSet.Tables.Contains (Navigator.LocalName)){
						if (loadType == LoadType.BEFORE)
							LoadBeforeTable(Navigator);
						else if (loadType == LoadType.CURRENT)
							LoadCurrentTable(Navigator);
					}
										
				} while (Navigator.MoveToNext ());
				
				if (NewRow)
					Table.Rows.Add (Row);
			}
		}

		private void LoadBeforeTable (XPathNavigator Navigator) 
		{
				
			String id = null;
			DataTable Table = DSet.Tables [Navigator.LocalName];
			DataRow Row = Table.NewRow ();
							
			if (Navigator.MoveToFirstAttribute ()) {
								
				do {
					if (Navigator.Name == "diffgr:id")
						id = Navigator.Value;
								       
				} while (Navigator.MoveToNextAttribute ());
								
				Navigator.MoveToParent ();
			}
														
			LoadColumns (Table, Row, Navigator, true, LoadType.BEFORE);
			DiffGrRows.Add (id, Row); // for later use
			Row.AcceptChanges ();
		}

		private void LoadCurrentTable (XPathNavigator Navigator) 
		{
			
			DataTable Table = DSet.Tables [Navigator.LocalName];
			DataRow Row = null;
			bool NewRow = false;
			bool HasErrors = false;
			string id = "";
								
			if (Navigator.MoveToFirstAttribute ()) {
									
				do {
					// Find out was there same row in 'before' section
					if (Navigator.LocalName == "id") {
						id = Navigator.Value;
						if (DiffGrRows.Contains (id))
							Row = (DataRow)DiffGrRows [id];

					}
					else if (Navigator.LocalName == "hasErrors" && String.Compare (Navigator.Value, "true", true) == 0)
						HasErrors = true;
				} while (Navigator.MoveToNextAttribute ());

				// back to business
				Navigator.MoveToParent ();
			}

			if (Row == null) {
				Row = Table.NewRow ();
				NewRow = true;
			}
																
			LoadColumns (Table, Row, Navigator, NewRow, LoadType.CURRENT);
									
			// back to business
			Navigator.MoveToParent();
									
			if (HasErrors) // If row had errors add row to hashtable for later use
				ErrorRows.Add (id, Row);
		
		}

		private static XmlDocument BuildXmlDocument(XmlReader reader)
		{
			string endinglocalName = reader.LocalName;

			XmlDocument doc = new XmlDocument();

			// create all contents with use of ReadNode()
			do 
			{
				XmlNode n = doc.ReadNode (reader);
				if(n == null) break;
				doc.AppendChild (n);
			} while (reader.LocalName == endinglocalName);

			return doc;
		}


		#endregion // Private methods
	}
}