Design and Implementation of an Attribute-Driven, Caching Data Abstraction Layer

using System;
using System.Collections.Generic;
using System.Collections;
using System.Globalization;
using System.Text;
using BrainTechLLC.ThreadSafeObjects;

namespace BrainTechLLC.DAL
{
	public partial class DBLayer<T> where T : DBLayer<T>, IDBLayer<T>, new()
	{
		/// <summary>
		/// Stores generated (integer) indices on the fly.  Each dictionary entry stores a property value name.  Associated
		/// with the property value name: another dictionary which maps Integer values to "rows" where property value = Integer value
		/// </summary>
		internal static Dictionary<string, Dictionary<long, ResultSet<T>>> _integerIndices = new Dictionary<string, Dictionary<long, ResultSet<T>>>(32, StringComparer.OrdinalIgnoreCase);

		/// <summary>
		/// Stores generated (string) indices on the fly.  (See above)
		/// </summary>
		internal static Dictionary<string, Dictionary<string, ResultSet<T>>> _stringIndices = new Dictionary<string, Dictionary<string, ResultSet<T>>>(32, StringComparer.OrdinalIgnoreCase);

		internal static void CheckDynamicIntIndices(PropertyNameAndValueCollection pnv, int propNameValueIndex, long numericValue, out int itemCount, out bool createdIndex, ref ResultSet<T> results)
		{
			createdIndex = false;
			Dictionary<long, ResultSet<T>> dynamicIndex;
			if (_integerIndices.TryGetValue(pnv._propertyNameAndValuePairs[propNameValueIndex]._propertyName, out dynamicIndex) == true)
			{
				ResultSet<T> indexedResults;

				if (WhereCache.CheckCacheDirty())
				{
					results.InvalidateCachedProperties();
					_integerIndices.Clear();
					_stringIndices.Clear();
					itemCount = results.RowCount;
				}
				else
				{
					// For the value we are intered in (numericValue), see if we have already stored the
					// results for a search on this value.  If so, start with this shortened result set
					// (fewer entries / rows to search)
					if (dynamicIndex.TryGetValue(numericValue, out indexedResults) == true)
					{
						itemCount = indexedResults.RowCount;
						results = indexedResults;
					}
					else
					{
						createdIndex = true;
						itemCount = results.RowCount;
					}
				}

			}
			else // no dynamic index found, but one can be made
			{
				createdIndex = true;
				itemCount = results.RowCount;
			}
		}

		internal static void CheckDynamicStringIndices(PropertyNameAndValueCollection pnv, int propNameValueIndex, string stringValue, out int itemCount, out bool createdIndex, ref ResultSet<T> results)
		{
			createdIndex = false;
			Dictionary<string, ResultSet<T>> dynamicStringIndex;

			// Handle/look for string indices
			if (_stringIndices.TryGetValue(pnv._propertyNameAndValuePairs[propNameValueIndex]._propertyName, out dynamicStringIndex) == true)
			{
				ResultSet<T> indexedResults;
				if (WhereCache.CheckCacheDirty())
				{
					results.InvalidateCachedProperties(); _integerIndices.Clear(); _stringIndices.Clear();
					itemCount = results.RowCount;
				}
				else
				{
					if (dynamicStringIndex.TryGetValue(stringValue, out indexedResults) == true)
					{
						itemCount = indexedResults.RowCount;
						results = indexedResults;
					}
					else
					{
						createdIndex = true;
						itemCount = results.RowCount;
					}
				}
			}
			else // no dynamic index found, but one can be made
			{
				createdIndex = true;
				itemCount = results.RowCount;
			}
		}		
	}
}