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

using System.Runtime.CompilerServices;

namespace System.Reflection.Metadata.Ecma335
{
    internal static class HasCustomDebugInformationTag
    {
        internal const int NumberOfBits = 5;
        internal const int LargeRowSize = 0x00000001 << (16 - NumberOfBits);

        internal const uint MethodDef = 0x00000000;
        internal const uint Field = 0x00000001;
        internal const uint TypeRef = 0x00000002;
        internal const uint TypeDef = 0x00000003;
        internal const uint Param = 0x00000004;
        internal const uint InterfaceImpl = 0x00000005;
        internal const uint MemberRef = 0x00000006;
        internal const uint Module = 0x00000007;
        internal const uint DeclSecurity = 0x00000008;
        internal const uint Property = 0x00000009;
        internal const uint Event = 0x0000000A;
        internal const uint StandAloneSig = 0x0000000B;
        internal const uint ModuleRef = 0x0000000C;
        internal const uint TypeSpec = 0x0000000D;
        internal const uint Assembly = 0x0000000E;
        internal const uint AssemblyRef = 0x0000000F;
        internal const uint File = 0x00000010;
        internal const uint ExportedType = 0x00000011;
        internal const uint ManifestResource = 0x00000012;
        internal const uint GenericParam = 0x00000013;
        internal const uint GenericParamConstraint = 0x00000014;
        internal const uint MethodSpec = 0x00000015;

        internal const uint Document = 0x00000016;
        internal const uint LocalScope = 0x00000017;
        internal const uint LocalVariable = 0x00000018;
        internal const uint LocalConstant = 0x00000019;
        internal const uint Import = 0x0000001a;

        internal const uint TagMask = 0x0000001F;

        // Arbitrary value not equal to any of the token types in the array. This includes 0 which is TokenTypeIds.Module.
        internal const uint InvalidTokenType = uint.MaxValue;

        internal static ReadOnlySpan<uint> TagToTokenTypeArray =>
        [
            TokenTypeIds.MethodDef,
            TokenTypeIds.FieldDef,
            TokenTypeIds.TypeRef,
            TokenTypeIds.TypeDef,
            TokenTypeIds.ParamDef,
            TokenTypeIds.InterfaceImpl,
            TokenTypeIds.MemberRef,
            TokenTypeIds.Module,
            TokenTypeIds.DeclSecurity,
            TokenTypeIds.Property,
            TokenTypeIds.Event,
            TokenTypeIds.Signature,
            TokenTypeIds.ModuleRef,
            TokenTypeIds.TypeSpec,
            TokenTypeIds.Assembly,
            TokenTypeIds.AssemblyRef,
            TokenTypeIds.File,
            TokenTypeIds.ExportedType,
            TokenTypeIds.ManifestResource,
            TokenTypeIds.GenericParam,
            TokenTypeIds.GenericParamConstraint,
            TokenTypeIds.MethodSpec,

            TokenTypeIds.Document,
            TokenTypeIds.LocalScope,
            TokenTypeIds.LocalVariable,
            TokenTypeIds.LocalConstant,
            TokenTypeIds.ImportScope,

            InvalidTokenType,
            InvalidTokenType,
            InvalidTokenType,
            InvalidTokenType,
            InvalidTokenType
        ];

        internal const TableMask TablesReferenced =
          TableMask.MethodDef
          | TableMask.Field
          | TableMask.TypeRef
          | TableMask.TypeDef
          | TableMask.Param
          | TableMask.InterfaceImpl
          | TableMask.MemberRef
          | TableMask.Module
          | TableMask.DeclSecurity
          | TableMask.Property
          | TableMask.Event
          | TableMask.StandAloneSig
          | TableMask.ModuleRef
          | TableMask.TypeSpec
          | TableMask.Assembly
          | TableMask.AssemblyRef
          | TableMask.File
          | TableMask.ExportedType
          | TableMask.ManifestResource
          | TableMask.GenericParam
          | TableMask.GenericParamConstraint
          | TableMask.MethodSpec
          | TableMask.Document
          | TableMask.LocalScope
          | TableMask.LocalVariable
          | TableMask.LocalConstant
          | TableMask.ImportScope;

        [MethodImpl(MethodImplOptions.AggressiveInlining)]
        internal static EntityHandle ConvertToHandle(uint taggedReference)
        {
            uint tokenType = TagToTokenTypeArray[(int)(taggedReference & TagMask)];
            uint rowId = (taggedReference >> NumberOfBits);

            if (tokenType == InvalidTokenType || ((rowId & ~TokenTypeIds.RIDMask) != 0))
            {
                Throw.InvalidCodedIndex();
            }

            return new EntityHandle(tokenType | rowId);
        }

        internal static uint ConvertToTag(EntityHandle handle)
        {
            uint tokenType = handle.Type;
            uint rowId = (uint)handle.RowId;
            return (tokenType >> TokenTypeIds.RowIdBitCount) switch
            {
                TokenTypeIds.MethodDef >> TokenTypeIds.RowIdBitCount => rowId << NumberOfBits | MethodDef,
                TokenTypeIds.FieldDef >> TokenTypeIds.RowIdBitCount => rowId << NumberOfBits | Field,
                TokenTypeIds.TypeRef >> TokenTypeIds.RowIdBitCount => rowId << NumberOfBits | TypeRef,
                TokenTypeIds.TypeDef >> TokenTypeIds.RowIdBitCount => rowId << NumberOfBits | TypeDef,
                TokenTypeIds.ParamDef >> TokenTypeIds.RowIdBitCount => rowId << NumberOfBits | Param,
                TokenTypeIds.InterfaceImpl >> TokenTypeIds.RowIdBitCount => rowId << NumberOfBits | InterfaceImpl,
                TokenTypeIds.MemberRef >> TokenTypeIds.RowIdBitCount => rowId << NumberOfBits | MemberRef,
                TokenTypeIds.Module >> TokenTypeIds.RowIdBitCount => rowId << NumberOfBits | Module,
                TokenTypeIds.DeclSecurity >> TokenTypeIds.RowIdBitCount => rowId << NumberOfBits | DeclSecurity,
                TokenTypeIds.Property >> TokenTypeIds.RowIdBitCount => rowId << NumberOfBits | Property,
                TokenTypeIds.Event >> TokenTypeIds.RowIdBitCount => rowId << NumberOfBits | Event,
                TokenTypeIds.Signature >> TokenTypeIds.RowIdBitCount => rowId << NumberOfBits | StandAloneSig,
                TokenTypeIds.ModuleRef >> TokenTypeIds.RowIdBitCount => rowId << NumberOfBits | ModuleRef,
                TokenTypeIds.TypeSpec >> TokenTypeIds.RowIdBitCount => rowId << NumberOfBits | TypeSpec,
                TokenTypeIds.Assembly >> TokenTypeIds.RowIdBitCount => rowId << NumberOfBits | Assembly,
                TokenTypeIds.AssemblyRef >> TokenTypeIds.RowIdBitCount => rowId << NumberOfBits | AssemblyRef,
                TokenTypeIds.File >> TokenTypeIds.RowIdBitCount => rowId << NumberOfBits | File,
                TokenTypeIds.ExportedType >> TokenTypeIds.RowIdBitCount => rowId << NumberOfBits | ExportedType,
                TokenTypeIds.ManifestResource >> TokenTypeIds.RowIdBitCount => rowId << NumberOfBits | ManifestResource,
                TokenTypeIds.GenericParam >> TokenTypeIds.RowIdBitCount => rowId << NumberOfBits | GenericParam,
                TokenTypeIds.GenericParamConstraint >> TokenTypeIds.RowIdBitCount => rowId << NumberOfBits | GenericParamConstraint,
                TokenTypeIds.MethodSpec >> TokenTypeIds.RowIdBitCount => rowId << NumberOfBits | MethodSpec,

                TokenTypeIds.Document >> TokenTypeIds.RowIdBitCount => rowId << NumberOfBits | Document,
                TokenTypeIds.LocalScope >> TokenTypeIds.RowIdBitCount => rowId << NumberOfBits | LocalScope,
                TokenTypeIds.LocalVariable >> TokenTypeIds.RowIdBitCount => rowId << NumberOfBits | LocalVariable,
                TokenTypeIds.LocalConstant >> TokenTypeIds.RowIdBitCount => rowId << NumberOfBits | LocalConstant,
                TokenTypeIds.ImportScope >> TokenTypeIds.RowIdBitCount => rowId << NumberOfBits | Import,

                _ => 0,
            };
        }
    }
}