// Copyright 1998-2014 Epic Games, Inc. All Rights Reserved.

using System;
using System.Collections.Generic;
using System.Linq;
using System.Web.Caching;

namespace Tools.CrashReporter.CrashReportWebSite.Models
{
	/// <summary>
	/// A class to handle caching of database results on the web server.
	/// </summary>
	public class CachedDataService : IDisposable
	{
		private CrashRepository LocalCrashRepository;
		private BuggRepository BuggRepositoryInstance;

		private Cache CacheInstance;

		private const string CacheKeyPrefix = "_CachedDataService_";
		private const string CallstackKeyPrefix = "_CallStack_";
		private const string FunctionCallKeyPrefix = "_FunctionCallStack_";
		private const string UserNameKeyPrefix = "_UserName_";

		/// <summary>
		/// Link the Http context cache to a crash repository.
		/// </summary>
		/// <param name="InCache">The current Http context cache.</param>
		/// <param name="InCrashRepository">The repository to associate the cache with.</param>
		public CachedDataService( Cache InCache, CrashRepository InCrashRepository )
		{
			CacheInstance = InCache;
			LocalCrashRepository = InCrashRepository;
		}

		/// <summary>
		/// Link the Http context cache to a Bugg repository.
		/// </summary>
		/// <param name="InCache">The current Http context cache.</param>
		/// <param name="InBuggRepository">The repository to associate the cache with.</param>
		public CachedDataService( Cache InCache, BuggRepository InBuggRepository )
		{
			CacheInstance = InCache;
			BuggRepositoryInstance = InBuggRepository;
		}

		/// <summary>
		/// Implementing Dispose.
		/// </summary>
		public void Dispose()
		{
			Dispose( true );
			GC.SuppressFinalize( this );
		}

		/// <summary>
		/// Disposes the resources.
		/// </summary>
		/// <param name="Disposing">true if the Dispose call is from user code, and not system code.</param>
		protected virtual void Dispose( bool Disposing )
		{
			LocalCrashRepository.Dispose();
			BuggRepositoryInstance.Dispose();
		}

		/// <summary>
		/// Retrieve a cached (and pre-parsed) callstack container from the cache, or parse the raw callstack, and add to the cache.
		/// </summary>
		/// <param name="CurrentCrash">The crash to retrieve the parsed callstack for.</param>
		/// <returns>A parsed callstack.</returns>
		public CallStackContainer GetCallStack( Crash CurrentCrash )
		{
			string Key = CacheKeyPrefix + CallstackKeyPrefix + CurrentCrash.Id;
			CallStackContainer CallStack = ( CallStackContainer )CacheInstance[Key];
			if( CallStack == null )
			{
				CallStack = new CallStackContainer( CurrentCrash );
				CallStack.bDisplayFunctionNames = true;
				CacheInstance.Insert( Key, CallStack );
			}

			return CallStack;
		}

		/// <summary>
		/// Retrieve a list of crashes from the cache, or retrieve a list from the database, and add to the cache.
		/// </summary>
		/// <param name="DateFrom">The date of the earliest crash to consider.</param>
		/// <param name="DateTo">The date of the most recent crash to consider.</param>
		/// <returns>A list of crashes between the start and end dates.</returns>
		public List<Crash> GetCrashes( DateTime DateFrom, DateTime DateTo )
		{
			string Key = CacheKeyPrefix + DateFrom + DateTo;
			List<Crash> Data = ( List<Crash> )CacheInstance[Key];
			if( Data == null )
			{
				IQueryable<Crash> DataQuery = LocalCrashRepository.ListAll();
				DataQuery = LocalCrashRepository.FilterByDate( DataQuery, DateFrom, DateTo );
				Data = DataQuery.ToList();
				CacheInstance.Insert( Key, Data );
			}

			return Data;
		}

		/// <summary>
		/// Retrieve a list of function call names from an encoded pattern. This is either from the cache, or from the database and then added to the cache.
		/// </summary>
		/// <param name="Pattern">A callstack pattern in the form '1+3+34+2'.</param>
		/// <returns>A list of function names.</returns>
		public List<string> GetFunctionCalls( string Pattern )
		{
			string Key = CacheKeyPrefix + FunctionCallKeyPrefix + Pattern;
			List<string> FunctionCalls = ( List<string> )CacheInstance[Key];
			if( FunctionCalls == null )
			{
				string[] Ids = Pattern.Split( "+".ToCharArray() );
				List<int> IdList = new List<int>();
				foreach( string id in Ids )
				{
					int i;
					if( int.TryParse( id, out i ) )
					{
						IdList.Add( i );
					}
				}

				FunctionCalls = BuggRepositoryInstance.GetFunctionCalls( IdList );
				CacheInstance.Insert( Key, FunctionCalls );
			}

			return FunctionCalls;
		}
	}
}