// Licensed to the .NET Foundation under one or more agreements.
// The .NET Foundation licenses this file to you under the MIT license.

using System;

using Internal.NativeFormat;
using Internal.Runtime;
using Internal.Text;
using Internal.TypeSystem;
using Internal.TypeSystem.Interop;

namespace ILCompiler.DependencyAnalysis
{
    /// <summary>
    /// Represents a hash table of struct marshalling stub types generated into the image.
    /// </summary>
    internal sealed class StructMarshallingStubMapNode : ObjectNode, ISymbolDefinitionNode
    {
        private readonly ExternalReferencesTableNode _externalReferences;
        private readonly InteropStateManager _interopStateManager;

        public StructMarshallingStubMapNode(ExternalReferencesTableNode externalReferences, InteropStateManager interopStateManager)
        {
            _externalReferences = externalReferences;
            _interopStateManager = interopStateManager;
        }

        public void AppendMangledName(NameMangler nameMangler, Utf8StringBuilder sb)
        {
            sb.Append(nameMangler.CompilationUnitPrefix).Append("__struct_marshalling_stub_map"u8);
        }
        public int Offset => 0;
        public override bool IsShareable => false;

        public override ObjectNodeSection GetSection(NodeFactory factory) => _externalReferences.GetSection(factory);

        public override bool StaticDependenciesAreComputed => true;

        protected override string GetName(NodeFactory factory) => this.GetMangledName(factory.NameMangler);

        public override ObjectData GetData(NodeFactory factory, bool relocsOnly = false)
        {
            // This node does not trigger generation of other nodes.
            if (relocsOnly)
                return new ObjectData(Array.Empty<byte>(), Array.Empty<Relocation>(), 1, new ISymbolDefinitionNode[] { this });

            var writer = new NativeWriter();
            var typeMapHashTable = new VertexHashtable();

            Section hashTableSection = writer.NewSection();
            hashTableSection.Place(typeMapHashTable);

            foreach (var structType in factory.MetadataManager.GetTypesWithStructMarshalling())
            {
                // the order of data written is as follows:
                //  managed struct type
                //  NumFields<< 2 | (HasInvalidLayout ? (2:0)) | (MarshallingRequired ? (1:0))
                //  If !HasInvalidLayout
                //    If MarshallingRequired:
                //      size
                //      struct marshalling thunk
                //      struct unmarshalling thunk
                //      struct cleanup thunk
                //    For each field field:
                //      name
                //      offset

                var nativeType = _interopStateManager.GetStructMarshallingNativeType(structType);

                Vertex marshallingData = null;
                Vertex fieldOffsetData = null;
                uint header;

                if (!nativeType.HasInvalidLayout)
                {
                    if (MarshalHelpers.IsStructMarshallingRequired(structType))
                    {
                        Vertex thunks = writer.GetTuple(
                            writer.GetUnsignedConstant(_externalReferences.GetIndex(factory.MethodEntrypoint(_interopStateManager.GetStructMarshallingManagedToNativeThunk(structType)))),
                            writer.GetUnsignedConstant(_externalReferences.GetIndex(factory.MethodEntrypoint(_interopStateManager.GetStructMarshallingNativeToManagedThunk(structType)))),
                            writer.GetUnsignedConstant(_externalReferences.GetIndex(factory.MethodEntrypoint(_interopStateManager.GetStructMarshallingCleanupThunk(structType)))));

                        uint size = (uint)nativeType.InstanceFieldSize.AsInt;
                        marshallingData = writer.GetTuple(writer.GetUnsignedConstant(size), thunks);
                    }

                    for (int i = 0; i < nativeType.Fields.Length; i++)
                    {
                        var row = writer.GetTuple(
                            writer.GetStringConstant(nativeType.Fields[i].GetName()),
                            writer.GetUnsignedConstant((uint)nativeType.Fields[i].Offset.AsInt)
                            );

                        fieldOffsetData = (fieldOffsetData != null) ? writer.GetTuple(fieldOffsetData, row) : row;
                    }

                    header = (uint)((marshallingData != null) ? InteropDataConstants.HasMarshallers : 0) |
                            (uint)(nativeType.Fields.Length << InteropDataConstants.FieldCountShift);
                }
                else
                {
                    header = InteropDataConstants.HasInvalidLayout;
                }

                Vertex data = writer.GetUnsignedConstant(header);
                if (marshallingData != null)
                    data = writer.GetTuple(data, marshallingData);

                if (fieldOffsetData != null)
                    data = writer.GetTuple(data, fieldOffsetData);

                Vertex vertex = writer.GetTuple(
                    writer.GetUnsignedConstant(_externalReferences.GetIndex(factory.NecessaryTypeSymbol(structType))),
                    data
                );

                int hashCode = structType.GetHashCode();
                typeMapHashTable.Append((uint)hashCode, hashTableSection.Place(vertex));
            }

            byte[] hashTableBytes = writer.Save();

            return new ObjectData(hashTableBytes, Array.Empty<Relocation>(), 1, new ISymbolDefinitionNode[] { this });
        }

        protected internal override int Phase => (int)ObjectNodePhase.Ordered;
        public override int ClassCode => (int)ObjectNodeOrder.StructMarshallingStubMapNode;
    }
}