Untitled

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;

namespace Patterns
{
    /// <summary>
    /// Represents a pattern node
    /// </summary>
    class PatternNode
    {
        private Dictionary<Dimension, ItemType> _terminators = new Dictionary<Dimension, ItemType>(DimensionEqualityComparer.Default);
        // You may want to flip this to a dictionary instead - depending on how many items you have.
        private PatternNode[] _nodes;
        private static readonly int _nodesCount;

        static PatternNode()
        {
            var max = 0;
            foreach (int val in Enum.GetValues(typeof(ItemType)))
            {
                max = Math.Max(max, val);
            }
            _nodesCount = max + 1;
        }

        /// <summary>
        /// Gets the <see cref="Patterns.PatternNode"/> with the specified item type.
        /// </summary>
        public PatternNode this[ItemType next]
        {
            get
            {
                if (_nodes == null)
                    return null;
                return _nodes[(int)next];
            }
        }

        /// <summary>
        /// Gets or sets the <see cref="Patterns.ItemType"/> with the specified dimension.
        /// </summary>
        public ItemType this[Dimension dimension]
        {
            get
            {
                ItemType result;
                if (!_terminators.TryGetValue(dimension, out result))
                    return ItemType.Nothing;
                return result;
            }
        }

        /// <summary>
        /// Initializes a new instance of the <see cref="PatternNode"/> class.
        /// </summary>
        public PatternNode()
        {
        }

        /// <summary>
        /// Adds the specified terminator.
        /// </summary>
        /// <param name="dimension">The dimension.</param>
        /// <param name="next">Type of the item.</param>
        public void Add(Dimension dimension, ItemType itemType)
        {
            _terminators.Add(dimension, itemType);
        }

        /// <summary>
        /// Creates or gets a node for the specified item type.
        /// </summary>
        /// <param name="next">The next item type.</param>
        public PatternNode Add(ItemType next)
        {
            // Definitely not thread safe.
            var nodes = _nodes ?? (_nodes = new PatternNode[_nodesCount]);
            return _nodes[(int)next] ?? (_nodes[(int)next] = new PatternNode());
        }
    }
}