wabbajack/Wabbajack.Lib/Downloaders/DownloadDispatcher.cs

using System;
using System.Collections.Generic;
using System.Linq;
using System.Threading.Tasks;
using Alphaleonis.Win32.Filesystem;
using Wabbajack.Common;
using Wabbajack.Lib.Downloaders.UrlDownloaders;

namespace Wabbajack.Lib.Downloaders
{
    public static class DownloadDispatcher
    {
        public static readonly List<IDownloader> Downloaders = new List<IDownloader>()
        {
            new GameFileSourceDownloader(),
            new MegaDownloader(),
            new DropboxDownloader(),
            new GoogleDriveDownloader(),
            new ModDBDownloader(),
            new NexusDownloader(),
            new MediaFireDownloader(),
            new LoversLabDownloader(),
            new VectorPlexusDownloader(),
            new DeadlyStreamDownloader(),
            new BethesdaNetDownloader(),
            new TESAllianceDownloader(),
            new YouTubeDownloader(),
            new HTTPDownloader(),
            new ManualDownloader(),
        };

        public static readonly List<IUrlInferencer> Inferencers = new List<IUrlInferencer>()
        {
            new BethesdaNetInferencer(),
            new YoutubeInferencer()
        };

        private static readonly Dictionary<Type, IDownloader> IndexedDownloaders;

        static DownloadDispatcher()
        {
            IndexedDownloaders = Downloaders.ToDictionary(d => d.GetType());
        }

        public static async Task<AbstractDownloadState?> Infer(Uri uri)
        {
            foreach (var inf in Inferencers)
            {
                var state = await inf.Infer(uri);
                if (state != null)
                    return state;
            }
            return null;

        }

        public static T GetInstance<T>() where T : IDownloader
        {
            var inst = (T)IndexedDownloaders[typeof(T)];
            return inst;
        }

        public static async Task<AbstractDownloadState> ResolveArchive(dynamic ini, bool quickMode = false)
        {
            var states = await Task.WhenAll(Downloaders.Select(d => (Task<AbstractDownloadState>)d.GetDownloaderState(ini, quickMode)));
            return states.FirstOrDefault(result => result != null);
        }

        /// <summary>
        /// Reduced version of Resolve archive that requires less information, but only works
        /// with a single URL string
        /// </summary>
        /// <param name="ini"></param>
        /// <returns></returns>
        public static AbstractDownloadState? ResolveArchive(string url)
        {
            return Downloaders.OfType<IUrlDownloader>().Select(d => d.GetDownloaderState(url)).FirstOrDefault(result => result != null);
        }

        public static async Task PrepareAll(IEnumerable<AbstractDownloadState> states)
        {
            await Task.WhenAll(states.Select(s => s.GetDownloader().GetType())
                  .Distinct()
                  .Select(t => Downloaders.First(d => d.GetType() == t).Prepare()));
        }

        public static async Task<bool> DownloadWithPossibleUpgrade(Archive archive, AbsolutePath destination)
        {
            var success = await Download(archive, destination);
            if (success)
            {
                await destination.FileHashCachedAsync();
                return true;
            }

            Utils.Log($"Download failed, looking for upgrade");
            var upgrade = await ClientAPI.GetModUpgrade(archive.Hash);
            if (upgrade == null)
            {
                Utils.Log($"No upgrade found for {archive.Hash}");
                return false;
            }
            Utils.Log($"Upgrading via {upgrade.State.PrimaryKeyString}");
            
            Utils.Log($"Upgrading {archive.Hash}");
            var upgradePath = destination.Parent.Combine("_Upgrade_" + archive.Name);
            var upgradeResult = await Download(upgrade, upgradePath);
            if (!upgradeResult) return false;

            var patchName = $"{archive.Hash.ToHex()}_{upgrade.Hash.ToHex()}";
            var patchPath = destination.Parent.Combine("_Patch_" + patchName);

            var patchState = new Archive(new HTTPDownloader.State($"https://wabbajackcdn.b-cdn.net/updates/{patchName}"))
            {
                Name = patchName,
            };

            var patchResult = await Download(patchState, patchPath);
            if (!patchResult) return false;

            Utils.Status($"Applying Upgrade to {archive.Hash}");
            await using (var patchStream = patchPath.OpenRead())
            await using (var srcStream = upgradePath.OpenRead())
            await using (var destStream = destination.Create())
            {
                OctoDiff.Apply(srcStream, patchStream, destStream);
            }

            await destination.FileHashCachedAsync();

            return true;
        }

        private static async Task<bool> Download(Archive archive, AbsolutePath destination)
        {
            try
            {
                var result =  await archive.State.Download(archive, destination);
                if (!result) return false;

                if (!archive.Hash.IsValid) return true;
                var hash = await destination.FileHashCachedAsync();
                if (hash == archive.Hash) return true;

                Utils.Log($"Hashed download is incorrect");
                return false;

            }
            catch (Exception)
            {
                return false;
            }
        }
    }
}