using System;
using System.Collections.Generic;
using System.IO;
using System.Reflection;
using System.Runtime.Loader;

namespace GodotPlugins
{
    public class PluginLoadContext : AssemblyLoadContext
    {
        private readonly AssemblyDependencyResolver _resolver;
        private readonly ICollection<string> _sharedAssemblies;
        private readonly AssemblyLoadContext _mainLoadContext;

        public string? AssemblyLoadedPath { get; private set; }

        public PluginLoadContext(string pluginPath, ICollection<string> sharedAssemblies,
            AssemblyLoadContext mainLoadContext)
            : base(isCollectible: true)
        {
            _resolver = new AssemblyDependencyResolver(pluginPath);
            _sharedAssemblies = sharedAssemblies;
            _mainLoadContext = mainLoadContext;
        }

        protected override Assembly? Load(AssemblyName assemblyName)
        {
            if (assemblyName.Name == null)
                return null;

            if (_sharedAssemblies.Contains(assemblyName.Name))
                return _mainLoadContext.LoadFromAssemblyName(assemblyName);

            string? assemblyPath = _resolver.ResolveAssemblyToPath(assemblyName);
            if (assemblyPath != null)
            {
                AssemblyLoadedPath = assemblyPath;

                // Load in memory to prevent locking the file
                using var assemblyFile = File.Open(assemblyPath, FileMode.Open, FileAccess.Read, FileShare.Read);
                string pdbPath = Path.ChangeExtension(assemblyPath, ".pdb");

                if (File.Exists(pdbPath))
                {
                    using var pdbFile = File.Open(pdbPath, FileMode.Open, FileAccess.Read, FileShare.Read);
                    return LoadFromStream(assemblyFile, pdbFile);
                }

                return LoadFromStream(assemblyFile);
            }

            return null;
        }

        protected override IntPtr LoadUnmanagedDll(string unmanagedDllName)
        {
            string? libraryPath = _resolver.ResolveUnmanagedDllToPath(unmanagedDllName);
            if (libraryPath != null)
                return LoadUnmanagedDllFromPath(libraryPath);

            return IntPtr.Zero;
        }
    }
}