//------------------------------------------------------------------------------
// <copyright file="XmlILIndex.cs" company="Microsoft">
//     Copyright (c) Microsoft Corporation.  All rights reserved.
// </copyright>
// <owner current="true" primary="true">Microsoft</owner>
//------------------------------------------------------------------------------

using System.Collections.Generic;
using System.ComponentModel;
using System.Diagnostics;
using System.Xml.XPath;

namespace System.Xml.Xsl.Runtime {

    /// <summary>
    /// This class manages nodes from one input document, indexed by key value(s).
    /// </summary>
    [EditorBrowsable(EditorBrowsableState.Never)]
    public sealed class XmlILIndex {
        private Dictionary<string, XmlQueryNodeSequence> table;

        /// <summary>
        /// This constructor is internal so that external users cannot construct it (and therefore we do not have to test it separately).
        /// </summary>
        internal XmlILIndex() {
            this.table = new Dictionary<string, XmlQueryNodeSequence>();
        }

        /// <summary>
        /// Add a node indexed by the specified key value.
        /// </summary>
        public void Add(string key, XPathNavigator navigator) {
            XmlQueryNodeSequence seq;

            if (!this.table.TryGetValue(key, out seq)) {
                // Create a new sequence and add it to the index
                seq = new XmlQueryNodeSequence();
                seq.AddClone(navigator);
                this.table.Add(key, seq);
            }
            else {
                // The nodes are guaranteed to be added in document order with possible duplicates.
                // Add node to the existing sequence if it differs from the last one.
                Debug.Assert(navigator.ComparePosition(seq[seq.Count - 1]) >= 0, "Index nodes must be added in document order");
                if (!navigator.IsSamePosition(seq[seq.Count - 1])) {
                    seq.AddClone(navigator);
                }
            }
        }

        /// <summary>
        /// Lookup a sequence of nodes that are indexed by the specified key value.
        /// Return a non-null empty sequence, if there are no nodes associated with the key.
        /// </summary>
        public XmlQueryNodeSequence Lookup(string key) {
            XmlQueryNodeSequence seq;

            if (!this.table.TryGetValue(key, out seq))
                seq = new XmlQueryNodeSequence();

            return seq;
        }
    }
}