ByondManager.cs

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using Microsoft.Extensions.Logging;
using System;
using System.Collections.Generic;
using System.Linq;
using System.Net;
using System.Text;
using System.Threading;
using System.Threading.Tasks;
using Tgstation.Server.Api;
using Tgstation.Server.Api.Models;
using Tgstation.Server.Host.Components.Events;
using Tgstation.Server.Host.Core;
using Tgstation.Server.Host.IO;
using Tgstation.Server.Host.Jobs;

namespace Tgstation.Server.Host.Components.Byond
{
    sealed class ByondManager : IByondManager
    {
        public const string BinPath = "byond/bin";

        const string CfgDirectoryName = "cfg";

        const string TrustedDmbFileName = "trusted.txt";

        const string VersionFileName = "Version.txt";

        const string ActiveVersionFileName = "ActiveVersion.txt";

        public Version ActiveVersion { get; private set; }

        public IReadOnlyList<Version> InstalledVersions
        {
            get
            {
                lock (installedVersions)
                    return installedVersions.Select(x => Version.Parse(x.Key).Semver()).ToList();
            }
        }

        readonly IIOManager ioManager;

        readonly IByondInstaller byondInstaller;

        readonly IEventConsumer eventConsumer;

        readonly ILogger<ByondManager> logger;

        readonly Dictionary<string, Task> installedVersions;

        readonly SemaphoreSlim semaphore;

        static string VersionKey(Version version) => new Version(version.Major, version.Minor).ToString();

        public ByondManager(IIOManager ioManager, IByondInstaller byondInstaller, IEventConsumer eventConsumer, ILogger<ByondManager> logger)
        {
            this.ioManager = ioManager ?? throw new ArgumentNullException(nameof(ioManager));
            this.byondInstaller = byondInstaller ?? throw new ArgumentNullException(nameof(byondInstaller));
            this.eventConsumer = eventConsumer ?? throw new ArgumentNullException(nameof(eventConsumer));
            this.logger = logger ?? throw new ArgumentNullException(nameof(logger));

            installedVersions = new Dictionary<string, Task>();
            semaphore = new SemaphoreSlim(1);
        }

        public void Dispose() => semaphore.Dispose();

        async Task InstallVersion(Version version, CancellationToken cancellationToken)
        {
            var ourTcs = new TaskCompletionSource<object>();
            Task inProgressTask;

            var versionKey = VersionKey(version);
            bool installed;
            lock (installedVersions)
            {
                installed = installedVersions.TryGetValue(versionKey, out inProgressTask);
                if (!installed)
                    installedVersions.Add(versionKey, ourTcs.Task);
            }

            if (installed)
                using (cancellationToken.Register(() => ourTcs.SetCanceled()))
                {
                    await Task.WhenAny(ourTcs.Task, inProgressTask).ConfigureAwait(false);
                    cancellationToken.ThrowIfCancellationRequested();
                    return;
                }
            else
                logger.LogDebug("Requested BYOND version {0} not currently installed. Doing so now...");

            // okay up to us to install it then
            try
            {
                await eventConsumer.HandleEvent(EventType.ByondInstallStart, new List<string> { versionKey }, cancellationToken).ConfigureAwait(false);
                var downloadTask = byondInstaller.DownloadVersion(version, cancellationToken);

                await ioManager.DeleteDirectory(versionKey, cancellationToken).ConfigureAwait(false);

                try
                {
                    var download = await downloadTask.ConfigureAwait(false);
                    await ioManager.CreateDirectory(versionKey, cancellationToken).ConfigureAwait(false);

                    var extractPath = ioManager.ResolvePath(versionKey);
                    logger.LogTrace("Extracting downloaded BYOND zip to {0}...", extractPath);
                    await ioManager.ZipToDirectory(extractPath, download, cancellationToken).ConfigureAwait(false);
                    await byondInstaller.InstallByond(extractPath, version, cancellationToken).ConfigureAwait(false);

                    // make sure to do this last because this is what tells us we have a valid version in the future
                    await ioManager.WriteAllBytes(ioManager.ConcatPath(versionKey, VersionFileName), Encoding.UTF8.GetBytes(version.ToString()), cancellationToken).ConfigureAwait(false);
                }
                catch (WebException e)
                {
                    // since the user can easily provide non-exitent version numbers, we'll turn this into a JobException
                    throw new JobException(ErrorCode.ByondDownloadFail, e);
                }
                catch (OperationCanceledException)
                {
                    throw;
                }
                catch
                {
                    await ioManager.DeleteDirectory(versionKey, cancellationToken).ConfigureAwait(false);
                    throw;
                }

                ourTcs.SetResult(null);
            }
            catch (Exception e)
            {
                if (!(e is OperationCanceledException))
                    await eventConsumer.HandleEvent(EventType.ByondInstallFail, new List<string> { e.Message }, cancellationToken).ConfigureAwait(false);
                lock (installedVersions)
                    installedVersions.Remove(versionKey);
                ourTcs.SetException(e);
                throw;
            }
        }

        public async Task ChangeVersion(Version version, CancellationToken cancellationToken)
        {
            if (version == null)
                throw new ArgumentNullException(nameof(version));
            var versionKey = VersionKey(version);
            await InstallVersion(version, cancellationToken).ConfigureAwait(false);
            using (await SemaphoreSlimContext.Lock(semaphore, cancellationToken).ConfigureAwait(false))
            {
                await ioManager.WriteAllBytes(ActiveVersionFileName, Encoding.UTF8.GetBytes(versionKey), cancellationToken).ConfigureAwait(false);
                await eventConsumer.HandleEvent(EventType.ByondActiveVersionChange, new List<string> { ActiveVersion != null ? VersionKey(ActiveVersion) : null, versionKey }, cancellationToken).ConfigureAwait(false);
                ActiveVersion = version;
            }
        }

        public async Task<IByondExecutableLock> UseExecutables(Version requiredVersion, CancellationToken cancellationToken)
        {
            var versionToUse = requiredVersion ?? ActiveVersion;
            if (versionToUse == null)
                throw new JobException(ErrorCode.ByondNoVersionsInstalled);
            await InstallVersion(versionToUse, cancellationToken).ConfigureAwait(false);

            var versionKey = VersionKey(versionToUse);
            var binPathForVersion = ioManager.ConcatPath(versionKey, BinPath);

            logger.LogTrace("Creating ByondExecutableLock lock for version {0}", requiredVersion);
            return new ByondExecutableLock(
                ioManager,
                semaphore,
                versionToUse,
                ioManager.ResolvePath(
                    ioManager.ConcatPath(
                        binPathForVersion,
                        byondInstaller.DreamDaemonName)),
                ioManager.ResolvePath(
                    ioManager.ConcatPath(
                        binPathForVersion,
                        byondInstaller.DreamMakerName)),
                ioManager.ResolvePath(
                    ioManager.ConcatPath(
                        byondInstaller.PathToUserByondFolder,
                        CfgDirectoryName,
                        TrustedDmbFileName)));
        }

        public async Task StartAsync(CancellationToken cancellationToken)
        {
            async Task<byte[]> GetActiveVersion()
            {
                var activeVersionFileExists = await ioManager.FileExists(ActiveVersionFileName, cancellationToken).ConfigureAwait(false);
                return !activeVersionFileExists ? null : await ioManager.ReadAllBytes(ActiveVersionFileName, cancellationToken).ConfigureAwait(false);
            }

            var activeVersionBytesTask = GetActiveVersion();

            // Create local cfg directory in case it doesn't exist
            var localCfgDirectory = ioManager.ConcatPath(
                    byondInstaller.PathToUserByondFolder,
                    CfgDirectoryName);
            await ioManager.CreateDirectory(
                localCfgDirectory,
                cancellationToken).ConfigureAwait(false);

            // Delete trusted.txt so it doesn't grow too large
            var trustedFilePath =
                ioManager.ConcatPath(
                    localCfgDirectory,
                    TrustedDmbFileName);
            logger.LogTrace("Deleting trusted .dmbs file {0}", trustedFilePath);
            await ioManager.DeleteFile(
                trustedFilePath,
                cancellationToken).ConfigureAwait(false);

            var byondDirectory = ioManager.ResolvePath();
            await ioManager.CreateDirectory(byondDirectory, cancellationToken).ConfigureAwait(false);
            var directories = await ioManager.GetDirectories(byondDirectory, cancellationToken).ConfigureAwait(false);

            async Task ReadVersion(string path)
            {
                var versionFile = ioManager.ConcatPath(path, VersionFileName);
                if (!await ioManager.FileExists(versionFile, cancellationToken).ConfigureAwait(false))
                {
                    logger.LogInformation("Cleaning unparsable version path: {0}", ioManager.ResolvePath(path));
                    await ioManager.DeleteDirectory(path, cancellationToken).ConfigureAwait(false); // cleanup
                    return;
                }

                var bytes = await ioManager.ReadAllBytes(versionFile, cancellationToken).ConfigureAwait(false);
                var text = Encoding.UTF8.GetString(bytes);
                if (Version.TryParse(text, out var version))
                {
                    var key = VersionKey(version);
                    lock (installedVersions)
                        if (!installedVersions.ContainsKey(key))
                        {
                            logger.LogDebug("Adding detected BYOND version {0}...", key);
                            installedVersions.Add(key, Task.CompletedTask);
                            return;
                        }
                }

                await ioManager.DeleteDirectory(path, cancellationToken).ConfigureAwait(false);
            }

            await Task.WhenAll(directories.Select(x => ReadVersion(x))).ConfigureAwait(false);

            var activeVersionBytes = await activeVersionBytesTask.ConfigureAwait(false);
            if (activeVersionBytes != null)
            {
                var activeVersionString = Encoding.UTF8.GetString(activeVersionBytes);
                bool hasRequestedActiveVersion;
                lock (installedVersions)
                    hasRequestedActiveVersion = installedVersions.ContainsKey(activeVersionString);
                if (hasRequestedActiveVersion && Version.TryParse(activeVersionString, out var activeVersion))
                    ActiveVersion = activeVersion.Semver();
                else
                {
                    logger.LogWarning("Failed to load saved active version {0}!", activeVersionString);
                    await ioManager.DeleteFile(ActiveVersionFileName, cancellationToken).ConfigureAwait(false);
                }
            }
        }

        public Task StopAsync(CancellationToken cancellationToken) => Task.CompletedTask;
    }
}