// Copyright (C) 2024, The Duplicati Team
// https://duplicati.com, hello@duplicati.com
// 
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// copy of this software and associated documentation files (the "Software"), 
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// and/or sell copies of the Software, and to permit persons to whom the 
// Software is furnished to do so, subject to the following conditions:
// 
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// 
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// OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, 
// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE 
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using CoCoL;
using Duplicati.Library.Main.Operation.Common;
using Duplicati.Library.Main.Volumes;
using System;
using System.Threading.Tasks;
using static Duplicati.Library.Main.Operation.Common.BackendHandler;

namespace Duplicati.Library.Main.Operation.Backup
{
    /// <summary>
    /// This class receives data blocks, registers then in the database.
    /// New blocks are added to a compressed archive and sent
    /// to the uploader
    /// </summary>
    internal static class DataBlockProcessor
    {
        public static Task Run(BackupDatabase database, Options options, ITaskReader taskreader)
        {
            return AutomationExtensions.RunTask(
            new
            {
                Input = Channels.OutputBlocks.ForRead,
                Output = Channels.BackendRequest.ForWrite,
                SpillPickup = Channels.SpillPickup.ForWrite,
            },

            async self =>
            {
                var noIndexFiles = options.IndexfilePolicy == Options.IndexFileStrategy.None;
                var fullIndexFiles = options.IndexfilePolicy == Options.IndexFileStrategy.Full;

                BlockVolumeWriter blockvolume = null;
                TemporaryIndexVolume indexvolume = null;

                try
                {
                    while (true)
                    {
                        var b = await self.Input.ReadAsync();

                        // Lazy-start a new block volume
                        if (blockvolume == null)
                        {
                            // Before we start a new volume, probe to see if it exists
                            // This will delay creation of volumes for differential backups
                            // There can be a race, such that two workers determine that
                            // the block is missing, but this will be solved by the AddBlock call
                            // which runs atomically
                            if (await database.FindBlockIDAsync(b.HashKey, b.Size) >= 0)
                            {
                                b.TaskCompletion.TrySetResult(false);
                                continue;
                            }

                            blockvolume = new BlockVolumeWriter(options);
                            blockvolume.VolumeID = await database.RegisterRemoteVolumeAsync(blockvolume.RemoteFilename, RemoteVolumeType.Blocks, RemoteVolumeState.Temporary);

                            indexvolume = noIndexFiles ? null : new TemporaryIndexVolume(options);
                        }

                        var newBlock = await database.AddBlockAsync(b.HashKey, b.Size, blockvolume.VolumeID);
                        b.TaskCompletion.TrySetResult(newBlock);

                        if (newBlock)
                        {
                            blockvolume.AddBlock(b.HashKey, b.Data, b.Offset, (int)b.Size, b.Hint);
                            if (indexvolume != null)
                            {
                                indexvolume.AddBlock(b.HashKey, b.Size);
                                if (b.IsBlocklistHashes && fullIndexFiles)
                                    indexvolume.AddBlockListHash(b.HashKey, b.Size, b.Data);
                            }

                            // If the volume is full, send to upload
                            if (blockvolume.Filesize > options.VolumeSize - options.Blocksize)
                            {
                                //When uploading a new volume, we register the volumes and then flush the transaction
                                // this ensures that the local database and remote storage are as closely related as possible
                                await database.UpdateRemoteVolumeAsync(blockvolume.RemoteFilename, RemoteVolumeState.Uploading, -1, null);

                                blockvolume.Close();

                                await database.CommitTransactionAsync("CommitAddBlockToOutputFlush");

                                FileEntryItem blockEntry = blockvolume.CreateFileEntryForUpload(options);

                                TemporaryIndexVolume indexVolumeCopy = null;
                                if (indexvolume != null)
                                {
                                    indexVolumeCopy = new TemporaryIndexVolume(options);
                                    indexvolume.CopyTo(indexVolumeCopy, false);
                                }

                                var uploadRequest = new VolumeUploadRequest(blockvolume, blockEntry, indexVolumeCopy, options, database);

                                blockvolume = null;
                                indexvolume = null;

                                // Write to output at the end here to prevent sending a full volume to the SpillCollector
                                await self.Output.WriteAsync(uploadRequest);
                            }

                        }

                        // We ignore the stop signal, but not the pause and terminate
                        await taskreader.ProgressAsync;
                    }
                }
                catch (Exception ex)
                {
                    if (ex.IsRetiredException())
                    {
                        // If we have collected data, merge all pending volumes into a single volume
                        if (blockvolume != null && blockvolume.SourceSize > 0)
                        {
                            await self.SpillPickup.WriteAsync(new SpillVolumeRequest(blockvolume, indexvolume));
                        }
                    }

                    throw;
                }
            });
        }
    }
}