// Copyright (C) 2025, The Duplicati Team
// https://duplicati.com, hello@duplicati.com
// 
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// Software is furnished to do so, subject to the following conditions:
// 
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using CoCoL;
using Duplicati.Library.Main.Operation.Common;
using Duplicati.Library.Main.Volumes;
using System;
using System.Collections.Generic;
using System.Threading.Tasks;

namespace Duplicati.Library.Main.Operation.Backup
{
    internal class SpillVolumeRequest
    {
        public BlockVolumeWriter BlockVolume { get; private set; }
        public TemporaryIndexVolume IndexVolume { get; private set; }

        public SpillVolumeRequest(BlockVolumeWriter blockvolume, TemporaryIndexVolume indexvolume)
        {
            BlockVolume = blockvolume;
            IndexVolume = indexvolume;
        }
    }

    /// <summary>
    /// This process just waits until all block processes are terminated
    /// and collects the non-written volumes.
    /// All remaining volumes are re-packed into one or more filled
    /// volumes and uploaded
    /// </summary>
    internal static class SpillCollectorProcess
    {
        public static Task Run(Channels channels, Options options, BackupDatabase database, IBackendManager backendManager, ITaskReader taskreader)
        {
            return AutomationExtensions.RunTask(
            new
            {
                Input = channels.SpillPickup.AsRead()
            },

            async self =>
            {
                var lst = new List<SpillVolumeRequest>();

                while (!await self.Input.IsRetiredAsync.ConfigureAwait(false))
                    try
                    {
                        lst.Add(await self.Input.ReadAsync().ConfigureAwait(false));
                    }
                    catch (Exception ex)
                    {
                        if (ex.IsRetiredException())
                            break;
                        throw;
                    }

                async Task<SpillVolumeRequest> GetNextTarget(SpillVolumeRequest source)
                {
                    SpillVolumeRequest target = null;
                    if (lst.Count == 0)
                    {
                        // No more targets, make one
                        target = new SpillVolumeRequest(new BlockVolumeWriter(options), source.IndexVolume == null ? null : new TemporaryIndexVolume(options));
                        target.BlockVolume.VolumeID = await database.RegisterRemoteVolumeAsync(target.BlockVolume.RemoteFilename, RemoteVolumeType.Blocks, RemoteVolumeState.Temporary).ConfigureAwait(false);
                    }
                    else
                    {
                        // Grab the next target
                        target = lst[0];
                        lst.RemoveAt(0);
                    }

                    // We copy all blocklisthashes as they are pre-filtered to be unique
                    if (source.IndexVolume != null)
                        source.IndexVolume.CopyTo(target.IndexVolume, true);

                    return target;
                }


                while (lst.Count > 1)
                {
                    // We ignore the stop signal, but not the pause and terminate
                    await taskreader.ProgressRendevouz().ConfigureAwait(false);

                    SpillVolumeRequest target = null;
                    var source = lst[0];

                    // Finalize the current work
                    source.BlockVolume.Close();

                    // Remove it from the list of active operations
                    lst.RemoveAt(0);

                    var buffer = new byte[options.Blocksize];

                    using (var rd = new BlockVolumeReader(options.CompressionModule, source.BlockVolume.LocalFilename, options))
                    {
                        // Make sure we process the blocklisthashes, even if the blockvolume is empty
                        target = await GetNextTarget(source).ConfigureAwait(false);

                        foreach (var file in rd.Blocks)
                        {
                            // Grab a target
                            if (target == null)
                                target = await GetNextTarget(source).ConfigureAwait(false);

                            var len = rd.ReadBlock(file.Key, buffer);
                            target.BlockVolume.AddBlock(file.Key, buffer, 0, len, Duplicati.Library.Interface.CompressionHint.Default);
                            await database.MoveBlockToVolumeAsync(file.Key, len, source.BlockVolume.VolumeID, target.BlockVolume.VolumeID).ConfigureAwait(false);

                            if (target.IndexVolume != null)
                                target.IndexVolume.AddBlock(file.Key, len);

                            if (target.BlockVolume.Filesize > options.VolumeSize - options.Blocksize)
                            {
                                target.BlockVolume.Close();
                                await UploadVolumeAndIndex(target, options, database, backendManager, taskreader).ConfigureAwait(false);
                                target = null;
                            }
                        }
                    }

                    // Make sure they are out of the database
                    System.IO.File.Delete(source.BlockVolume.LocalFilename);
                    await database.SafeDeleteRemoteVolumeAsync(source.BlockVolume.RemoteFilename).ConfigureAwait(false);

                    // Re-inject the target if it has content
                    if (target != null)
                        lst.Insert(lst.Count == 0 ? 0 : 1, target);
                }

                foreach (var n in lst)
                {
                    // We ignore the stop signal, but not the pause and terminate
                    await taskreader.ProgressRendevouz().ConfigureAwait(false);

                    n.BlockVolume.Close();
                    await UploadVolumeAndIndex(n, options, database, backendManager, taskreader).ConfigureAwait(false);
                }

            });
        }

        private static async Task UploadVolumeAndIndex(SpillVolumeRequest target, Options options, BackupDatabase database, IBackendManager backendManager, ITaskReader taskreader)
        {
            IndexVolumeWriter indexVolumeCopy = null;
            if (target.IndexVolume != null)
            {
                // TODO: It is much easier to let the BackendManager deal with index files,
                // but it adds a bit of strain to the database
                indexVolumeCopy = await target.IndexVolume.CreateVolume(target.BlockVolume.RemoteFilename, options, database).ConfigureAwait(false);
                // Create link before upload is started, it will be removed later if upload fails
                await database.AddIndexBlockLinkAsync(indexVolumeCopy.VolumeID, target.BlockVolume.VolumeID).ConfigureAwait(false);
            }

            await backendManager.PutAsync(target.BlockVolume, indexVolumeCopy, null, false, taskreader.ProgressToken).ConfigureAwait(false);
        }
    }
}