//
// System.Data.Constraint.cs
//
// Author:
//	Franklin Wise <gracenote@earthlink.net>
//	Daniel Morgan
//      Tim Coleman (tim@timcoleman.com)
//   
//
// (C) Ximian, Inc. 2002
// Copyright (C) Tim Coleman, 2002
//

using System;
using System.Collections;
using System.ComponentModel;
using System.Runtime.InteropServices;
using System.Runtime.Serialization;

namespace System.Data {
	[Serializable]
	internal delegate void DelegateConstraintNameChange (object sender, string newName);

	[DefaultProperty ("ConstraintName")]	
	[Serializable]
	[TypeConverterAttribute (typeof (ConstraintConverter))]
	public abstract class Constraint 
	{
		internal event DelegateConstraintNameChange BeforeConstraintNameChange;

		//if constraintName is not set then a name is 
		//created when it is added to
		//the ConstraintCollection
		//it can not be set to null, empty or duplicate
		//once it has been added to the collection
		private string _constraintName;
		private PropertyCollection _properties;

		private Index _index;

		//Used for membership checking
		private ConstraintCollection _constraintCollection;

		DataSet dataSet;

		protected Constraint () 
		{
			dataSet = null;
			_properties = new PropertyCollection();
		}

		[CLSCompliant (false)]
		protected internal virtual DataSet _DataSet {
			get { return dataSet; }
		}

		[DataCategory ("Data")]
		[DataSysDescription ("Indicates the name of this constraint.")]
		[DefaultValue ("")]
		public virtual string ConstraintName {
			get{ return "" + _constraintName; } 
			set{
				//This should only throw an exception when it
				//is a member of a ConstraintCollection which
				//means we should let the ConstraintCollection
				//handle exceptions when this value changes
				_onConstraintNameChange(value);
				_constraintName = value;
			}
		}

		[Browsable (false)]
		[DataCategory ("Data")]
		[DataSysDescription ("The collection that holds custom user information.")]
		public PropertyCollection ExtendedProperties {
			get { return _properties; }
		}

		[DataSysDescription ("Indicates the table of this constraint.")]
		public abstract DataTable Table {
			get;
		}

		internal ConstraintCollection ConstraintCollection {
			get{ return _constraintCollection; }
			set{ _constraintCollection = value; }
		}
		
		private void _onConstraintNameChange (string newName)
		{
			if (null != BeforeConstraintNameChange)
			{
				BeforeConstraintNameChange (this, newName);
			}
		}

		//call once before adding a constraint to a collection
		//will throw an exception to prevent the add if a rule is broken
		internal virtual void AddToConstraintCollectionSetup (ConstraintCollection collection)
		{
		}
					
		internal virtual void AssertConstraint ()
		{
		}
		
		internal virtual void AssertConstraint (DataRow row)
		{
		}

		internal virtual void RollbackAssert (DataRow row)
		{
		}

		//call once before removing a constraint to a collection
		//can throw an exception to prevent the removal
		internal virtual void RemoveFromConstraintCollectionCleanup (ConstraintCollection collection)
		{
		}

		[MonoTODO]
		protected void CheckStateForProperty ()
		{
			throw new NotImplementedException ();
		}

		protected internal void SetDataSet (DataSet dataSet)
		{
			this.dataSet = dataSet;
		}

		internal Index Index
		{
			get {
				return _index;
			}
			set {
				_index = value;
			}
		}

		protected internal void UpdateIndex (DataRow row)
		{
			if (row.RowState == DataRowState.Detached || row.RowState == DataRowState.Unchanged)
				Index.Insert (new Node (row), DataRowVersion.Default);
			else if ((row.RowState == DataRowState.Modified) || (row.RowState == DataRowState.Added)) {
				// first we check if the values of the key changed.
				bool keyChanged = false;
				for (int i = 0; i < Index.Columns.Length; i++) {
					if (row[Index.Columns[i], DataRowVersion.Default] != row[Index.Columns[i], DataRowVersion.Current]) {
						keyChanged = true;
					}
				}
				// if key changed we first try to insert a new node 
				// and,if succeded, we delete the row's old node.
				if (keyChanged) 
				{
					// insert new node for the row
					// note : may throw if not succeded
					Index.Insert (new Node (row), DataRowVersion.Default);

					// delete the row's node
					Index.Delete(row);					
				}
			}
		}

		protected internal void RollbackIndex (DataRow row)
		{
			Node n = Index.Find(row, DataRowVersion.Default);
			if ( n == null)
				throw new ConstraintException("Row was not found in constraint index");

			// first remove the node inserted as a result of last AssertConstraint on the row 
			Index.Delete(n);
			
			// if the row is not detached we should add back to the index 
			// node corresponding to row value before AssertConstraint was called
			if(row.RowState != DataRowState.Detached){
				// since index before we updated index was ok, insert should always suceed
				// maybe we still need to try/catch here
				Index.Insert(new Node(row), DataRowVersion.Current);
			}
		}


		/// <summary>
		/// Gets the ConstraintName, if there is one, as a string. 
		/// </summary>
		public override string ToString () 
		{
			return "" + _constraintName;
		}

	}
}