#nullable enable

using System;
using System.Collections.Generic;
using System.IO;
using System.Linq;
using Mono.Cecil;

namespace ShrinkSDK.CodeGen
{

internal sealed class PathAssemblyResolver : IAssemblyResolver
{
    private readonly Dictionary<string, string> _paths = new(StringComparer.OrdinalIgnoreCase);
    private readonly Dictionary<string, AssemblyDefinition> _assemblies = new(StringComparer.OrdinalIgnoreCase);
    private AssemblyDefinition? _self;

    public PathAssemblyResolver(IEnumerable<string> references)
    {
        foreach (var path in references.Where(File.Exists))
            _paths[Path.GetFileNameWithoutExtension(path)] = Path.GetFullPath(path);
    }

    public void SetSelf(AssemblyDefinition assembly) => _self = assembly;

    public AssemblyDefinition? Resolve(AssemblyNameReference name) => Resolve(name, new ReaderParameters());

    public AssemblyDefinition? Resolve(AssemblyNameReference name, ReaderParameters parameters)
    {
        if (string.Equals(name.Name, _self?.Name.Name, StringComparison.OrdinalIgnoreCase))
            return _self;
        if (_assemblies.TryGetValue(name.Name, out var cached))
            return cached;
        if (!_paths.TryGetValue(name.Name, out var path))
            return null;

        parameters.AssemblyResolver = this;
        parameters.ReadingMode = ReadingMode.Immediate;
        var assembly = AssemblyDefinition.ReadAssembly(path, parameters);
        _assemblies[name.Name] = assembly;
        return assembly;
    }

    public void Dispose()
    {
        foreach (var assembly in _assemblies.Values)
            assembly.Dispose();
        _assemblies.Clear();
    }
}
}