Readarr/src/NzbDrone.Common/Composition/ContainerBuilderBase.cs

using System;
using System.Collections.Generic;
using System.IO;
using System.Linq;
using System.Reflection;
using System.Runtime.InteropServices;
using System.Runtime.Loader;
using NzbDrone.Common.EnvironmentInfo;
using NzbDrone.Common.Messaging;
using TinyIoC;

namespace NzbDrone.Common.Composition
{
    public abstract class ContainerBuilderBase
    {
        private readonly List<Type> _loadedTypes;

        protected IContainer Container { get; }

        protected ContainerBuilderBase(IStartupContext args, List<string> assemblies)
        {
            _loadedTypes = new List<Type>();

            assemblies.Add(OsInfo.IsWindows ? "Readarr.Windows" : "Readarr.Mono");
            assemblies.Add("Readarr.Common");

            var startupPath = AppDomain.CurrentDomain.BaseDirectory;

            foreach (var assemblyName in assemblies)
            {
                _loadedTypes.AddRange(AssemblyLoadContext.Default.LoadFromAssemblyPath(Path.Combine(startupPath, $"{assemblyName}.dll")).GetTypes());
            }

            AppDomain.CurrentDomain.AssemblyResolve += new ResolveEventHandler(ContainerResolveEventHandler);
            RegisterSQLiteResolver();

            Container = new Container(new TinyIoCContainer(), _loadedTypes);
            AutoRegisterInterfaces();
            Container.Register(args);
        }

        private static Assembly ContainerResolveEventHandler(object sender, ResolveEventArgs args)
        {
            var resolver = new AssemblyDependencyResolver(args.RequestingAssembly.Location);
            var assemblyPath = resolver.ResolveAssemblyToPath(new AssemblyName(args.Name));

            if (assemblyPath == null)
            {
                return null;
            }

            return AssemblyLoadContext.Default.LoadFromAssemblyPath(assemblyPath);
        }

        public static void RegisterSQLiteResolver()
        {
            // This ensures we look for sqlite3 using libsqlite3.so.0 on Linux and not libsqlite3.so which
            // is less likely to exist.
            var sqliteAssembly = AssemblyLoadContext.Default.LoadFromAssemblyPath(
                Path.Combine(AppDomain.CurrentDomain.BaseDirectory, "System.Data.SQLite.dll"));

            try
            {
                NativeLibrary.SetDllImportResolver(sqliteAssembly, LoadSqliteNativeLib);
            }
            catch (InvalidOperationException)
            {
                // This can only be set once per assembly
                // Catch required for NzbDrone.Host tests
            }
        }

        private static IntPtr LoadSqliteNativeLib(string libraryName, Assembly assembly, DllImportSearchPath? dllImportSearchPath)
        {
            var mappedName = OsInfo.IsLinux && libraryName == "sqlite3" ? "libsqlite3.so.0" : libraryName;
            return NativeLibrary.Load(mappedName, assembly, dllImportSearchPath);
        }

        private void AutoRegisterInterfaces()
        {
            var loadedInterfaces = _loadedTypes.Where(t => t.IsInterface).ToList();
            var implementedInterfaces = _loadedTypes.SelectMany(t => t.GetInterfaces());

            var contracts = loadedInterfaces.Union(implementedInterfaces).Where(c => !c.IsGenericTypeDefinition && !string.IsNullOrWhiteSpace(c.FullName))
                .Where(c => !c.FullName.StartsWith("System"))
                .Except(new List<Type> { typeof(IMessage), typeof(IEvent), typeof(IContainer) }).Distinct().OrderBy(c => c.FullName);

            foreach (var contract in contracts)
            {
                AutoRegisterImplementations(contract);
            }
        }

        protected void AutoRegisterImplementations<TContract>()
        {
            AutoRegisterImplementations(typeof(TContract));
        }

        private void AutoRegisterImplementations(Type contractType)
        {
            var implementations = Container.GetImplementations(contractType).Where(c => !c.IsGenericTypeDefinition).ToList();

            if (implementations.Count == 0)
            {
                return;
            }

            if (implementations.Count == 1)
            {
                var impl = implementations.Single();
                Container.RegisterSingleton(contractType, impl);
            }
            else
            {
                Container.RegisterAllAsSingleton(contractType, implementations);
            }
        }
    }
}