DataCorruptionByTimeZoneChangeProtection.cs

using ApexInvesting.Platform.Utilities;
using ApexTough.Providers;
using System;
using System.Collections.Generic;
using System.IO;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace ApexTough.TradingPlatform.Utilities {

    /// <summary>
    /// Throw this exception to indicate that NT8's operating timezone has changed, but the stored historical data has not been updated to match the new timezone.
    /// Corrupted data will be displayed if the user proceeds.
    /// </summary>
    public class DataCorruptedByTimeZoneChangeException : Exception {
        public DataCorruptedByTimeZoneChangeException(TimeZoneInfo previousTimeZone, TimeZoneInfo currentTimeZone)
            : base($"The NT8 operating timezone has changed to '{currentTimeZone.DisplayName}' but the NT8 data cache has not been cleared. Either restore the NT8 operating timezone to '{previousTimeZone.DisplayName}' or clear the NT8 data cache.") { }
    }

    /// <summary>
    /// Use this class to protect your users from inadvertently corrupting their historical data when they change the NT8 operating timezone.
    /// The NT8 operating timezone can be set by the user from the Tools -> Options -> General -> TimeZone option, but it's very important to know
    /// that users can unwittingly change the NT8 operating timezone by changing the timezone on their computer system clock.
    /// </summary>
    public static class DataCorruptionByTimeZoneChangeProtection {

        private const string DATA_FILE_NAME = "NT8/TimeZoneChangeProtectionData";

        private static bool hasDetectedIssues = false;

        /// <summary>
        /// Throws an exception if data has been corrupted by the user changing NT8's operating timezone.
        /// Call this method during toolkit bootstrap.
        /// </summary>
        public static void CheckForCorruption() {

            try {

                var savedData = FileSystemDataCache.Read<StoredData>(DATA_FILE_NAME);
                var currentTimeZoneId = NinjaTrader.Core.Globals.GeneralOptions.TimeZoneInfo.Id;

                /// If the toolkit is running for the first time, exit without error.
                if (null == savedData) return;

                /// If the timezone has not changed since last startup, exit without error.
                if (currentTimeZoneId == savedData.TimeZoneId) return;

                /// If the historical tick data cache has been cleared (files deleted), exit without error.
                if (!File.Exists(savedData.DataFileName)) return;

                /// If the historical tick data file has been modified, we know that it has most likely been updated for the new timezone,
                /// exit without error.
                if (GetHash(File.ReadAllBytes(savedData.DataFileName)) != savedData.DataFileHash) return;

                /// We have detected data corruption
                hasDetectedIssues = true;
                throw new DataCorruptedByTimeZoneChangeException(TimeZoneInfo.FindSystemTimeZoneById(savedData.TimeZoneId), NinjaTrader.Core.Globals.GeneralOptions.TimeZoneInfo);

            } finally {
                TimerUtility.Callback(TimeSpan.FromSeconds(10), SaveState);
            }
        }

        /// <summary>
        /// Stores data that will be used for corruption checking next time NT8 starts up.
        /// </summary>
        private static void SaveState() {

            if (hasDetectedIssues) {
                /// If data corruption issues were detected on system startup, don't wanna save any new data until the user has resolved the original issue. 
                /// The user has already been instructed to either change the NT8 timezone back to what it was, or clear the data cache. If the user has reverted
                /// or intends to revert the NT8 timezone setting, we would screw up the user's recovery process by overwriting state.
                return;
            }

            /// Save system state ready for checking on next startup.
            var data = new StoredData();
            data.TimeZoneId = NinjaTrader.Core.Globals.GeneralOptions.TimeZoneInfo.Id;
            data.DataFileName = GetAHistoricalTickDataFileAndHash(out data.DataFileHash);
            FileSystemDataCache.Save(DATA_FILE_NAME, data);

            // If there were no historical data files available, we'll keep retrying until we find that one has been created.
            if (null == data.DataFileName)
                TimerUtility.Callback(TimeSpan.FromSeconds(10), SaveState);
        }

        /// <summary>
        /// Chooses a filename from the historical tick data folder, ensuring that the chosen file has a length > 0 and calculates a hash for the file content.
        /// </summary>
        private static string GetAHistoricalTickDataFileAndHash(out int fileHash) {
            var baseDirectory = new DirectoryInfo(Path.Combine(NinjaTrader.Core.Globals.UserDataDir, "db", "tick"));
            foreach (var instrumentFolder in baseDirectory.GetDirectories()) {
                foreach (var fileInfo in instrumentFolder.GetFiles("*.ncd")) {
                    var bytes = File.ReadAllBytes(fileInfo.FullName);
                    if (bytes.Length > 0) {
                        fileHash = GetHash(bytes);
                        return fileInfo.FullName;
                    }
                }
            }
            fileHash = 0;
            return null;
        }

        /// <summary>
        /// Assumes that bytes.Length > 0
        /// </summary>
        private static int GetHash(byte[] bytes) {
            /// Assume that a lot of care has been put into making the string hashing function very efficient and unique.
            return ASCIIEncoding.UTF8.GetString(bytes).GetHashCode();
        }

        private class StoredData {
            public string TimeZoneId;
            public string DataFileName;
            public int DataFileHash;
        }
    }
}