using System.Reflection.Metadata;
using System.Reflection.PortableExecutable;
using System.Security.Cryptography;

namespace CVRManager.Services;

public record AssemblyDetails(string FileName, string AssemblyName, string Version, string MelonName, string MelonVersion, string MelonAuthor, string MelonLink, string Sha256);

public static class AssemblyReader
{
    public static AssemblyDetails Read(string path)
    {
        var file = Path.GetFileName(path);
        var bytes = File.ReadAllBytes(path);
        var hash = Convert.ToBase64String(SHA256.HashData(bytes));
        string asmName = Path.GetFileNameWithoutExtension(file), version = "", mName = "", mVer = "", mAuthor = "", mLink = "";
        try
        {
            using var pe = new PEReader(new MemoryStream(bytes));
            if (pe.HasMetadata)
            {
                var md = pe.GetMetadataReader();
                var def = md.GetAssemblyDefinition();
                asmName = md.GetString(def.Name);
                version = def.Version.ToString();
                foreach (var h in def.GetCustomAttributes())
                {
                    var attr = md.GetCustomAttribute(h);
                    if (!IsMelonInfo(md, attr.Constructor)) continue;
                    var strings = attr.DecodeValue(new Provider()).FixedArguments
                        .Where(a => a.Type is PrimitiveTypeCode.String && a.Value is string).Select(a => (string)a.Value!).ToList();
                    if (strings.Count > 0) mName = strings[0];
                    if (strings.Count > 1) mVer = strings[1];
                    if (strings.Count > 2) mAuthor = strings[2];
                    if (strings.Count > 3) mLink = strings[3];
                    break;
                }
            }
        }
        catch (Exception e) when (e is BadImageFormatException or InvalidOperationException or ArgumentException) { }
        var fv = System.Diagnostics.FileVersionInfo.GetVersionInfo(path).ProductVersion?.Split('+', '-')[0];
        return new AssemblyDetails(file, asmName, string.IsNullOrEmpty(fv) ? version : fv, mName, mVer, mAuthor, mLink, hash);
    }

    static bool IsMelonInfo(MetadataReader md, EntityHandle ctor)
    {
        if (ctor.Kind != HandleKind.MemberReference) return false;
        var member = md.GetMemberReference((MemberReferenceHandle)ctor);
        if (member.Parent.Kind != HandleKind.TypeReference) return false;
        var type = md.GetTypeReference((TypeReferenceHandle)member.Parent);
        return md.GetString(type.Name) == "MelonInfoAttribute";
    }

    sealed class Provider : ICustomAttributeTypeProvider<object?>
    {
        const string SystemType = "System.Type";
        public object? GetPrimitiveType(PrimitiveTypeCode typeCode) => typeCode;
        public object? GetSystemType() => SystemType;
        public object? GetSZArrayType(object? elementType) => elementType;
        public object? GetTypeFromDefinition(MetadataReader reader, TypeDefinitionHandle handle, byte rawTypeKind) => new object();
        public object? GetTypeFromReference(MetadataReader reader, TypeReferenceHandle handle, byte rawTypeKind)
        {
            var t = reader.GetTypeReference(handle);
            return reader.GetString(t.Name) == "Type" && reader.GetString(t.Namespace) == "System" ? SystemType : new object();
        }
        public object? GetTypeFromSerializedName(string name) => name;
        public PrimitiveTypeCode GetUnderlyingEnumType(object? type) => PrimitiveTypeCode.Int32;
        public bool IsSystemType(object? type) => type is string s && s == SystemType;
    }
}