using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.IO;
using Duplicati.Library.Main.Database;
using Duplicati.Library.Main.Volumes;
using Duplicati.Library.Interface;
using System.Threading.Tasks;
using CoCoL;
using System.Threading;
using Duplicati.Library.Utility;

namespace Duplicati.Library.Main.Operation
{
    /// <summary>
    /// The backup handler is the primary function,
    /// which performs a backup of the given sources
    /// to the chosen destination
    /// </summary>
    internal class BackupHandler : IDisposable
    {    
        private readonly Options m_options;
        private string m_backendurl;

        private LocalBackupDatabase m_database;

        private Library.Utility.IFilter m_filter;
        private Library.Utility.IFilter m_sourceFilter;

        private BackupResults m_result;

        public BackupHandler(string backendurl, Options options, BackupResults results)
        {
            m_options = options;
            m_result = results;
            m_backendurl = backendurl;
                            
            if (options.AllowPassphraseChange)
                throw new UserInformationException(Strings.Common.PassphraseChangeUnsupported);
        }
        
        public static Snapshots.ISnapshotService GetSnapshot(string[] sources, Options options, ILogWriter log)
        {
            try
            {
                if (options.SnapShotStrategy != Options.OptimizationStrategy.Off)
                    return Duplicati.Library.Snapshots.SnapshotUtility.CreateSnapshot(sources, options.RawOptions);
            }
            catch (Exception ex)
            {
                if (options.SnapShotStrategy == Options.OptimizationStrategy.Required)
                    throw;
                else if (options.SnapShotStrategy == Options.OptimizationStrategy.On)
                    log.AddWarning(Strings.Common.SnapshotFailedError(ex.ToString()), ex);
            }

            return Library.Utility.Utility.IsClientLinux ?
                (Library.Snapshots.ISnapshotService)new Duplicati.Library.Snapshots.NoSnapshotLinux(sources, options.RawOptions)
                    :
                (Library.Snapshots.ISnapshotService)new Duplicati.Library.Snapshots.NoSnapshotWindows(sources, options.RawOptions);
        }

        private void PreBackupVerify(BackendManager backend, string protectedfile)
        {
            m_result.OperationProgressUpdater.UpdatePhase(OperationPhase.Backup_PreBackupVerify);
            using(new Logging.Timer("PreBackupVerify"))
            {
                try
                {
                    if (m_options.NoBackendverification)
                    {
                        FilelistProcessor.VerifyLocalList(backend, m_options, m_database, m_result.BackendWriter);
                        UpdateStorageStatsFromDatabase(backend.QuotaInfo);
                    }
                    else
                        FilelistProcessor.VerifyRemoteList(backend, m_options, m_database, m_result.BackendWriter, protectedfile);
                }
                catch (Exception ex)
                {
                    if (m_options.AutoCleanup)
                    {
                        m_result.AddWarning("Backend verification failed, attempting automatic cleanup", ex);
                        m_result.RepairResults = new RepairResults(m_result);
                        new RepairHandler(backend.BackendUrl, m_options, (RepairResults)m_result.RepairResults).Run();

                        m_result.AddMessage("Backend cleanup finished, retrying verification");
                        FilelistProcessor.VerifyRemoteList(backend, m_options, m_database, m_result.BackendWriter);
                    }
                    else
                        throw;
                }
            }
        }

        /// <summary>
        /// Performs the bulk of work by starting all relevant processes
        /// </summary>
        private static async Task RunMainOperation(Snapshots.ISnapshotService snapshot, Backup.BackupDatabase database, Backup.BackupStatsCollector stats, Options options, IFilter sourcefilter, IFilter filter, BackupResults result, Common.ITaskReader taskreader, long lastfilesetid)
        {
            using(new Logging.Timer("BackupMainOperation"))
            {
                // Make sure the CompressionHints table is initialized, otherwise all workers will initialize it
                var tb = options.CompressionHints.Count;

                Task all;
                using(new ChannelScope())
                {
                    all = Task.WhenAll(
                        new [] 
                        {
                            Backup.DataBlockProcessor.Run(database, options, taskreader),
                            Backup.FileBlockProcessor.Run(snapshot, options, database, stats, taskreader),
                            Backup.StreamBlockSplitter.Run(options, database, taskreader),
                            Backup.FileEnumerationProcess.Run(snapshot, options.FileAttributeFilter, sourcefilter, filter, options.SymlinkPolicy, options.HardlinkPolicy, options.ChangedFilelist, taskreader),
                            Backup.FilePreFilterProcess.Run(snapshot, options, stats, database),
                            Backup.MetadataPreProcess.Run(snapshot, options, database, lastfilesetid),
                            Backup.SpillCollectorProcess.Run(options, database, taskreader),
                            Backup.ProgressHandler.Run(result)
                        }
                        // Spawn additional block hashers
                        .Union(
                            Enumerable.Range(0, options.ConcurrencyBlockHashers - 1).Select(x => Backup.StreamBlockSplitter.Run(options, database, taskreader))
                        )
                        // Spawn additional compressors
                        .Union(
                            Enumerable.Range(0, options.ConcurrencyCompressors - 1).Select(x => Backup.DataBlockProcessor.Run(database, options, taskreader))
                        )
                    );
                }

                await all;

                if (options.ChangedFilelist != null && options.ChangedFilelist.Length >= 1)
                    await database.AppendFilesFromPreviousSetAsync(options.DeletedFilelist);
                
                result.OperationProgressUpdater.UpdatefileCount(result.ExaminedFiles, result.SizeOfExaminedFiles, true);
            }
        }

        private void CompactIfRequired(BackendManager backend, long lastVolumeSize)
        {
            var currentIsSmall = lastVolumeSize != -1 && lastVolumeSize <= m_options.SmallFileSize;

            if (m_options.KeepTime.Ticks > 0 || m_options.KeepVersions != 0 || m_options.RetentionPolicy.Count > 0)
            {
                m_result.OperationProgressUpdater.UpdatePhase(OperationPhase.Backup_Delete);
                m_result.DeleteResults = new DeleteResults(m_result);
                using(var db = new LocalDeleteDatabase(m_database))
                    new DeleteHandler(backend.BackendUrl, m_options, (DeleteResults)m_result.DeleteResults).DoRun(db, true, currentIsSmall, backend);

            }
            else if (currentIsSmall && !m_options.NoAutoCompact)
            {
                m_result.OperationProgressUpdater.UpdatePhase(OperationPhase.Backup_Compact);
                m_result.CompactResults = new CompactResults(m_result);
                using(var db = new LocalDeleteDatabase(m_database))
                    new CompactHandler(backend.BackendUrl, m_options, (CompactResults)m_result.CompactResults).DoCompact(db, true, backend);
            }
        }

        private void PostBackupVerification(BackendManager backend)
        {
            m_result.OperationProgressUpdater.UpdatePhase(OperationPhase.Backup_PostBackupVerify);
                using(new Logging.Timer("AfterBackupVerify"))
            FilelistProcessor.VerifyRemoteList(backend, m_options, m_database, m_result.BackendWriter);
            backend.WaitForEmpty();

            if (m_options.BackupTestSampleCount > 0 && m_database.GetRemoteVolumes().Count() > 0)
            {
                m_result.OperationProgressUpdater.UpdatePhase(OperationPhase.Backup_PostBackupTest);
                m_result.TestResults = new TestResults(m_result);

                using(var testdb = new LocalTestDatabase(m_database))
                    new TestHandler(m_backendurl, m_options, (TestResults)m_result.TestResults)
                        .DoRun(m_options.BackupTestSampleCount, testdb, backend);
            }
        }

        /// <summary>
        /// Handler for computing backend statistics, without relying on a remote folder listing
        /// </summary>
        /// <param name="quota">The backend quota information</param>
        private void UpdateStorageStatsFromDatabase(IQuotaInfo quota)
        {
            if (m_result.BackendWriter != null)
            {
                m_result.BackendWriter.KnownFileCount = m_database.GetRemoteVolumes().Count();
                m_result.BackendWriter.KnownFileSize = m_database.GetRemoteVolumes().Select(x => Math.Max(0, x.Size)).Sum();

                m_result.BackendWriter.UnknownFileCount = 0;
                m_result.BackendWriter.UnknownFileSize = 0;

                m_result.BackendWriter.BackupListCount = m_database.FilesetTimes.Count();
                m_result.BackendWriter.LastBackupDate = m_database.FilesetTimes.FirstOrDefault().Value.ToLocalTime();

                if (quota != null)
                {
                    m_result.BackendWriter.TotalQuotaSpace = quota.TotalQuotaSpace;
                    m_result.BackendWriter.FreeQuotaSpace = quota.FreeQuotaSpace;
                }
            }

            m_result.BackendWriter.AssignedQuotaSpace = m_options.QuotaSize;
        }

        public void Run(string[] sources, Library.Utility.IFilter filter)
        {
            RunAsync(sources, filter).WaitForTaskOrThrow();
        }

        private static Exception BuildException(Exception source, params Task[] tasks)
        {
            if (tasks == null || tasks.Length == 0)
                return source;

            var ex = new List<Exception>();
            ex.Add(source);

            foreach(var t in tasks)
                if (t != null)
                {
                    if (!t.IsCompleted && !t.IsFaulted && !t.IsCanceled)
                        t.Wait(500);

                    if (t.IsFaulted && t.Exception != null)
                        ex.Add(t.Exception);
                }

            if (ex.Count == 1)
                return ex.First();
            else
                return new AggregateException(ex.First().Message, ex);
        }

        private static async Task<long> FlushBackend(BackupResults result, IWriteChannel<Backup.IUploadRequest> uploadtarget, Task uploader)
        {
            var flushReq = new Backup.FlushRequest();

            // Wait for upload completion
            result.OperationProgressUpdater.UpdatePhase(OperationPhase.Backup_WaitForUpload);
            await uploadtarget.WriteAsync(flushReq).ConfigureAwait(false);

            // In case the uploader crashes, we grab the exception here
            if (await Task.WhenAny(uploader, flushReq.LastWriteSizeAync) == uploader)
                await uploader;

            // Grab the size of the last uploaded volume
            return await flushReq.LastWriteSizeAync;
        }

        private async Task RunAsync(string[] sources, Library.Utility.IFilter filter)
        {
            m_result.OperationProgressUpdater.UpdatePhase(OperationPhase.Backup_Begin);                        
            
            // New isolated scope for each operation
            using(new IsolatedChannelScope(Operation.Common.Channels.LogChannel))
            using(m_database = new LocalBackupDatabase(m_options.Dbpath, m_options))
            {
                m_result.SetDatabase(m_database);
                m_result.Dryrun = m_options.Dryrun;

                // Check the database integrity
                Utility.UpdateOptionsFromDb(m_database, m_options);
                Utility.VerifyParameters(m_database, m_options);

                var probe_path = m_database.GetFirstPath();
                if (probe_path != null && Duplicati.Library.Utility.Utility.GuessDirSeparator(probe_path) != System.IO.Path.DirectorySeparatorChar.ToString())
                    throw new UserInformationException(string.Format("The backup contains files that belong to another operating system. Proceeding with a backup would cause the database to contain paths from two different operation systems, which is not supported. To proceed without losing remote data, delete all filesets and make sure the --{0} option is set, then run the backup again to re-use the existing data on the remote store.", "no-auto-compact"));

                if (m_database.PartiallyRecreated)
                    throw new UserInformationException("The database was only partially recreated. This database may be incomplete and the repair process is not allowed to alter remote files as that could result in data loss.");
                
                if (m_database.RepairInProgress)
                    throw new UserInformationException("The database was attempted repaired, but the repair did not complete. This database may be incomplete and the backup process cannot continue. You may delete the local database and attempt to repair it again.");

                // If there is no filter, we set an empty filter to simplify the code
                // If there is a filter, we make sure that the sources are included
                m_filter = filter ?? new Library.Utility.FilterExpression();
                m_sourceFilter = new Library.Utility.FilterExpression(sources, true);

                Task parallelScanner = null;
                Task uploader = null;
                try
                {
                    // Setup runners and instances here
                    using(var db = new Backup.BackupDatabase(m_database, m_options))
                    //using(var backend = new BackendManager(m_backendurl, m_options, m_result.BackendWriter, m_database))
                    using(var filesetvolume = new FilesetVolumeWriter(m_options, m_database.OperationTimestamp))
                    using(var stats = new Backup.BackupStatsCollector(m_result))
                    using(var bk = new Common.BackendHandler(m_options, m_backendurl, db, stats, m_result.TaskReader))
                    // Keep a reference to these channels to avoid shutdown
                    using(var logtarget = ChannelManager.GetChannel(Common.Channels.LogChannel.ForWrite))
                    using(var uploadtarget = ChannelManager.GetChannel(Backup.Channels.BackendRequest.ForWrite))
                    using(var backend = new BackendManager(m_backendurl, m_options, m_result.BackendWriter, m_database, bk))
                    {
                        long filesetid;
                        var counterToken = new CancellationTokenSource();
                        using(var snapshot = GetSnapshot(sources, m_options, m_result))
                        {
                            try
                            {
                                // Start parallel scan, or use the database
                                if (m_options.ChangedFilelist == null || m_options.ChangedFilelist.Length < 1)
                                {
                                    if (m_options.DisableFileScanner)
                                    {
                                        var d = m_database.GetLastBackupFileCountAndSize();
                                        m_result.OperationProgressUpdater.UpdatefileCount(d.Item1, d.Item2, true);
                                    }
                                    else
                                    {
                                        parallelScanner = Backup.CountFilesHandler.Run(snapshot, m_result, m_options, m_sourceFilter, m_filter, m_result.TaskReader, counterToken.Token);
                                    }
                                }


                                // Make sure the database is sane
                                await db.VerifyConsistencyAsync(m_options.Blocksize, m_options.BlockhashSize, true);

                                // Start the uploader process
                                uploader = Backup.BackendUploader.Run(bk, m_options, db, m_result, m_result.TaskReader, stats);

                                // If we have an interrupted backup, grab the 
                                string lasttempfilelist = null;
                                long lasttempfileid = -1;
                                if (!m_options.DisableSyntheticFilelist)
                                {
                                    var candidates = (await db.GetIncompleteFilesetsAsync()).OrderBy(x => x.Value).ToArray();
                                    if (candidates.Length > 0)
                                    {
                                        lasttempfileid = candidates.Last().Key;
                                        lasttempfilelist = m_database.GetRemoteVolumeFromID(lasttempfileid).Name;
                                    }
                                }

                                // TODO: Rewrite to using the uploader process, or the BackendHandler interface
                                // Do a remote verification, unless disabled
                                PreBackupVerify(backend, lasttempfilelist);

                                // If the previous backup was interrupted, send a synthetic list
                                await Backup.UploadSyntheticFilelist.Run(db, m_options, m_result, m_result.TaskReader, lasttempfilelist, lasttempfileid);

                                // Grab the previous backup ID, if any
                                var prevfileset = m_database.FilesetTimes.FirstOrDefault();
                                if (prevfileset.Value.ToUniversalTime() > m_database.OperationTimestamp.ToUniversalTime())
                                    throw new Exception(string.Format("The previous backup has time {0}, but this backup has time {1}. Something is wrong with the clock.", prevfileset.Value.ToLocalTime(), m_database.OperationTimestamp.ToLocalTime()));
                                
                                var lastfilesetid = prevfileset.Value.Ticks == 0 ? -1 : prevfileset.Key;

                                // Rebuild any index files that are missing
                                await Backup.RecreateMissingIndexFiles.Run(db, m_options, m_result, m_result.TaskReader);

                                // This should be removed as the lookups are no longer used
                                m_database.BuildLookupTable(m_options);

                                // Prepare the operation by registering the filelist
                                m_result.OperationProgressUpdater.UpdatePhase(OperationPhase.Backup_ProcessingFiles);

                                var repcnt = 0;
                                while(repcnt < 100 && await db.GetRemoteVolumeIDAsync(filesetvolume.RemoteFilename) >= 0)
                                    filesetvolume.ResetRemoteFilename(m_options, m_database.OperationTimestamp.AddSeconds(repcnt++));

                                if (await db.GetRemoteVolumeIDAsync(filesetvolume.RemoteFilename) >= 0)
                                    throw new Exception("Unable to generate a unique fileset name");

                                var filesetvolumeid = await db.RegisterRemoteVolumeAsync(filesetvolume.RemoteFilename, RemoteVolumeType.Files, RemoteVolumeState.Temporary);
                                filesetid = await db.CreateFilesetAsync(filesetvolumeid, VolumeBase.ParseFilename(filesetvolume.RemoteFilename).Time);

                                // Run the backup operation
                                if (await m_result.TaskReader.ProgressAsync)
                                    await RunMainOperation(snapshot, db, stats, m_options, m_sourceFilter, m_filter, m_result, m_result.TaskReader, lastfilesetid);
                            }
                            finally
                            {
                                //If the scanner is still running for some reason, make sure we kill it now 
                                counterToken.Cancel();
                            }
                        }

                        // Ensure the database is in a sane state after adding data
                        using(new Logging.Timer("VerifyConsistency"))
                            await db.VerifyConsistencyAsync(m_options.Blocksize, m_options.BlockhashSize, false);

                        // Send the actual filelist
                        if (await m_result.TaskReader.ProgressAsync)
                            await Backup.UploadRealFilelist.Run(m_result, db, m_options, filesetvolume, filesetid, m_result.TaskReader);

                        // Wait for upload completion
                        m_result.OperationProgressUpdater.UpdatePhase(OperationPhase.Backup_WaitForUpload);
                        var lastVolumeSize = await FlushBackend(m_result, uploadtarget, uploader);

                        // Make sure we have the database up-to-date
                        await db.CommitTransactionAsync("CommitAfterUpload");
                            		                                        
                        if (await m_result.TaskReader.ProgressAsync)
                            CompactIfRequired(backend, lastVolumeSize);

                        if (m_options.UploadVerificationFile && await m_result.TaskReader.ProgressAsync)
                        {
                            m_result.OperationProgressUpdater.UpdatePhase(OperationPhase.Backup_VerificationUpload);
                            FilelistProcessor.UploadVerificationFile(backend, m_options, m_result.BackendWriter, m_database);
                        }

                        if (m_options.Dryrun)
                        {
                            m_database.RollbackTransaction(true);
                        }
                        else
                        {
                            m_database.CommitTransaction("CommitFinalizingBackup");
                                
                            if (m_result.TaskControlRendevouz() != TaskControlState.Stop)
                            {
                                if (m_options.NoBackendverification)
                                    UpdateStorageStatsFromDatabase(bk.QuotaInfo);
                                else
                                    PostBackupVerification(backend);
                            }
                        }
                        
                        m_database.WriteResults();                    
                        m_database.PurgeLogData(m_options.LogRetention);
                        m_database.CommitTransaction("AllDone", false);

                        if (m_options.AutoVacuum)
                        {
                            m_database.Vacuum();
                        }
                        m_result.OperationProgressUpdater.UpdatePhase(OperationPhase.Backup_Complete);
                        return;
                    }
                }
                catch (Exception ex)
                {
                    var aex = BuildException(ex, uploader, parallelScanner);
                    m_result.AddError("Fatal error", aex);
                    if (aex == ex)
                        throw;
                    
                    throw aex;
                }
                finally
                {
                    if (parallelScanner != null && !parallelScanner.IsCompleted)
                        parallelScanner.Wait(500);
                }
            }
        }

        public void Dispose()
        {
            if (m_result.EndTime.Ticks == 0)
                m_result.EndTime = DateTime.UtcNow;
        }
    }
}