using System;
using System.Collections.Generic;
using System.Collections.Immutable;
using System.IO;
using System.Linq;
using System.Reflection;
using System.Reflection.Metadata;
using System.Reflection.Metadata.Ecma335;
using System.Reflection.PortableExecutable;
using System.Security.Cryptography;
using System.Text;
using ICSharpCode.Decompiler.Documentation;
using ICSharpCode.Decompiler.TypeSystem;
using ICSharpCode.Decompiler.Util;

namespace ICSharpCode.Decompiler.Metadata
{
	using SRMMemberRef = System.Reflection.Metadata.MemberReference;
	using SRMMethod = System.Reflection.Metadata.MethodDefinition;
	using SRMMethodSpec = System.Reflection.Metadata.MethodSpecification;
	using SRMProperty = System.Reflection.Metadata.PropertyDefinition;
	using SRMEvent = System.Reflection.Metadata.EventDefinition;
	using SRMField = System.Reflection.Metadata.FieldDefinition;
	using SRMTypeDef = System.Reflection.Metadata.TypeDefinition;
	using SRMTypeRef = System.Reflection.Metadata.TypeReference;
	using SRMTypeSpec = System.Reflection.Metadata.TypeSpecification;
	using SRMAssemblyReference = System.Reflection.Metadata.AssemblyReference;



	public interface IAssemblyDocumentationResolver
	{
		XmlDocumentationProvider GetProvider();
	}

	public interface IMetadataEntity
	{
		PEFile Module { get; }
		EntityHandle Handle { get; }
		bool IsNil { get; }
	}

	public struct Variable
	{
		public string Name { get; set; }
	}

	public interface IDebugInfoProvider
	{
		IList<SequencePoint> GetSequencePoints(MethodDefinitionHandle method);
		IList<Variable> GetVariables(MethodDefinitionHandle method);
		bool TryGetName(MethodDefinitionHandle method, int index, out string name);
	}

	public enum TargetRuntime
	{
		Unknown,
		Net_1_0,
		Net_1_1,
		Net_2_0,
		Net_4_0
	}

	public enum ResourceType
	{
		Linked,
		Embedded,
		AssemblyLinked,
	}

	public struct Resource : IEquatable<Resource>
	{
		public PEFile Module { get; }
		public ManifestResourceHandle Handle { get; }
		public bool IsNil => Handle.IsNil;

		public Resource(PEFile module, ManifestResourceHandle handle) : this()
		{
			this.Module = module ?? throw new ArgumentNullException(nameof(module));
			this.Handle = handle;
		}

		ManifestResource This() => Module.Metadata.GetManifestResource(Handle);

		public bool Equals(Resource other)
		{
			return Module == other.Module && Handle == other.Handle;
		}

		public override bool Equals(object obj)
		{
			if (obj is Resource res)
				return Equals(res);
			return false;
		}

		public override int GetHashCode()
		{
			return unchecked(982451629 * Module.GetHashCode() + 982451653 * MetadataTokens.GetToken(Handle));
		}

		public static bool operator ==(Resource lhs, Resource rhs) => lhs.Equals(rhs);
		public static bool operator !=(Resource lhs, Resource rhs) => !lhs.Equals(rhs);

		public string Name => Module.Metadata.GetString(This().Name);

		public ManifestResourceAttributes Attributes => This().Attributes;
		public bool HasFlag(ManifestResourceAttributes flag) => (Attributes & flag) == flag;
		public ResourceType ResourceType => GetResourceType();

		ResourceType GetResourceType()
		{
			if (This().Implementation.IsNil)
				return ResourceType.Embedded;
			if (This().Implementation.Kind == HandleKind.AssemblyReference)
				return ResourceType.AssemblyLinked;
			return ResourceType.Linked;
		}

		public unsafe Stream TryOpenStream()
		{
			if (ResourceType != ResourceType.Embedded)
				return null;
			var headers = Module.Reader.PEHeaders;
			var resources = headers.CorHeader.ResourcesDirectory;
			int index = headers.GetContainingSectionIndex(resources.RelativeVirtualAddress);
			if (index < 0) throw new NotSupportedException();
			var sectionHeader = headers.SectionHeaders[index];
			var sectionData = Module.Reader.GetEntireImage();
			int totalOffset = resources.RelativeVirtualAddress + sectionHeader.PointerToRawData - sectionHeader.VirtualAddress;
			var reader = sectionData.GetReader();
			reader.Offset += totalOffset;
			reader.Offset += (int)This().Offset;
			int length = reader.ReadInt32();
			return new MemoryStream(reader.ReadBytes(length));
		}
	}

	public struct Entity : IEquatable<Entity>, IMetadataEntity
	{
		public PEFile Module { get; }
		public EntityHandle Handle { get; }
		public bool IsNil => Handle.IsNil;

		public Entity(PEFile module, EntityHandle handle) : this()
		{
			this.Module = module ?? throw new ArgumentNullException(nameof(module));
			this.Handle = handle;
		}

		public bool IsType() => Handle.Kind == HandleKind.TypeDefinition || Handle.Kind == HandleKind.TypeReference || Handle.Kind == HandleKind.TypeSpecification;

		public TypeDefinition ResolveAsType()
		{
			return MetadataResolver.ResolveType(Handle, new SimpleMetadataResolveContext(Module));
		}

		public FieldDefinition ResolveAsField()
		{
			return MetadataResolver.ResolveAsField(Handle, new SimpleMetadataResolveContext(Module));
		}

		public MethodDefinition ResolveAsMethod()
		{
			return MetadataResolver.ResolveAsMethod(Handle, new SimpleMetadataResolveContext(Module));
		}

		public bool Equals(Entity other)
		{
			return Module == other.Module && Handle == other.Handle;
		}

		public override bool Equals(object obj)
		{
			if (obj is Entity entity)
				return Equals(entity);
			return false;
		}

		public override int GetHashCode()
		{
			return unchecked(982451629 * Module.GetHashCode() + 982451653 * MetadataTokens.GetToken(Handle));
		}

		public static bool operator ==(Entity lhs, Entity rhs) => lhs.Equals(rhs);
		public static bool operator !=(Entity lhs, Entity rhs) => !lhs.Equals(rhs);

		public static implicit operator Entity(MethodDefinition method)
		{
			return new Entity(method.Module, method.Handle);
		}

		public static implicit operator Entity(PropertyDefinition property)
		{
			return new Entity(property.Module, property.Handle);
		}

		public static implicit operator Entity(EventDefinition @event)
		{
			return new Entity(@event.Module, @event.Handle);
		}

		public static implicit operator Entity(FieldDefinition field)
		{
			return new Entity(field.Module, field.Handle);
		}

		public static implicit operator Entity(TypeDefinition type)
		{
			return new Entity(type.Module, type.Handle);
		}

		public static implicit operator TypeDefinition(Entity entity)
		{
			return new TypeDefinition(entity.Module, (TypeDefinitionHandle)entity.Handle);
		}

		public static implicit operator MethodDefinition(Entity entity)
		{
			return new MethodDefinition(entity.Module, (MethodDefinitionHandle)entity.Handle);
		}

		public static implicit operator PropertyDefinition(Entity entity)
		{
			return new PropertyDefinition(entity.Module, (PropertyDefinitionHandle)entity.Handle);
		}

		public static implicit operator EventDefinition(Entity entity)
		{
			return new EventDefinition(entity.Module, (EventDefinitionHandle)entity.Handle);
		}

		public static implicit operator FieldDefinition(Entity entity)
		{
			return new FieldDefinition(entity.Module, (FieldDefinitionHandle)entity.Handle);
		}
	}

	public struct MethodDefinition : IEquatable<MethodDefinition>, IMetadataEntity
	{
		public PEFile Module { get; }
		public MethodDefinitionHandle Handle { get; }
		public bool IsNil => Handle.IsNil;
		EntityHandle IMetadataEntity.Handle => Handle;

		public MethodDefinition(PEFile module, MethodDefinitionHandle handle) : this()
		{
			this.Module = module ?? throw new ArgumentNullException(nameof(module));
			this.Handle = handle;
		}

		public bool Equals(MethodDefinition other)
		{
			return Module == other.Module && Handle == other.Handle;
		}

		public override bool Equals(object obj)
		{
			if (obj is MethodDefinition md)
				return Equals(md);
			return false;
		}

		public override int GetHashCode()
		{
			return unchecked(982451629 * Module.GetHashCode() + 982451653 * MetadataTokens.GetToken(Handle));
		}

		public static bool operator ==(MethodDefinition lhs, MethodDefinition rhs) => lhs.Equals(rhs);
		public static bool operator !=(MethodDefinition lhs, MethodDefinition rhs) => !lhs.Equals(rhs);

		public IList<SequencePoint> GetSequencePoints()
		{
			return Module.DebugInfo?.GetSequencePoints(Handle) ?? EmptyList<SequencePoint>.Instance;
		}

		public IList<Variable> GetVariables()
		{
			return Module.DebugInfo?.GetVariables(Handle) ?? EmptyList<Variable>.Instance;
		}
	}

	public struct PropertyDefinition : IEquatable<PropertyDefinition>, IMetadataEntity
	{
		public PEFile Module { get; }
		public PropertyDefinitionHandle Handle { get; }
		public bool IsNil => Handle.IsNil;
		EntityHandle IMetadataEntity.Handle => Handle;

		public PropertyDefinition(PEFile module, PropertyDefinitionHandle handle) : this()
		{
			this.Module = module ?? throw new ArgumentNullException(nameof(module));
			this.Handle = handle;
		}

		public bool Equals(PropertyDefinition other)
		{
			return Module == other.Module && Handle == other.Handle;
		}

		public override bool Equals(object obj)
		{
			if (obj is PropertyDefinition pd)
				return Equals(pd);
			return false;
		}

		public override int GetHashCode()
		{
			return unchecked(982451629 * Module.GetHashCode() + 982451653 * MetadataTokens.GetToken(Handle));
		}

		public static bool operator ==(PropertyDefinition lhs, PropertyDefinition rhs) => lhs.Equals(rhs);
		public static bool operator !=(PropertyDefinition lhs, PropertyDefinition rhs) => !lhs.Equals(rhs);
	}

	public struct FieldDefinition : IEquatable<FieldDefinition>, IMetadataEntity
	{
		public PEFile Module { get; }
		public FieldDefinitionHandle Handle { get; }
		public bool IsNil => Handle.IsNil;
		EntityHandle IMetadataEntity.Handle => Handle;

		public FieldDefinition(PEFile module, FieldDefinitionHandle handle) : this()
		{
			this.Module = module ?? throw new ArgumentNullException(nameof(module));
			this.Handle = handle;
		}

		public bool Equals(FieldDefinition other)
		{
			return Module == other.Module && Handle == other.Handle;
		}

		public override bool Equals(object obj)
		{
			if (obj is FieldDefinition fd)
				return Equals(fd);
			return false;
		}

		public override int GetHashCode()
		{
			return unchecked(982451629 * Module.GetHashCode() + 982451653 * MetadataTokens.GetToken(Handle));
		}

		public static bool operator ==(FieldDefinition lhs, FieldDefinition rhs) => lhs.Equals(rhs);
		public static bool operator !=(FieldDefinition lhs, FieldDefinition rhs) => !lhs.Equals(rhs);

		public object DecodeConstant()
		{
			var metadata = Module.Metadata;
			var constant = metadata.GetConstant(metadata.GetFieldDefinition(Handle).GetDefaultValue());
			var blob = metadata.GetBlobReader(constant.Value);
			switch (constant.TypeCode) {
				case ConstantTypeCode.Boolean:
					return blob.ReadBoolean();
				case ConstantTypeCode.Char:
					return blob.ReadChar();
				case ConstantTypeCode.SByte:
					return blob.ReadSByte();
				case ConstantTypeCode.Byte:
					return blob.ReadByte();
				case ConstantTypeCode.Int16:
					return blob.ReadInt16();
				case ConstantTypeCode.UInt16:
					return blob.ReadUInt16();
				case ConstantTypeCode.Int32:
					return blob.ReadInt32();
				case ConstantTypeCode.UInt32:
					return blob.ReadUInt32();
				case ConstantTypeCode.Int64:
					return blob.ReadInt64();
				case ConstantTypeCode.UInt64:
					return blob.ReadUInt64();
				case ConstantTypeCode.Single:
					return blob.ReadSingle();
				case ConstantTypeCode.Double:
					return blob.ReadDouble();
				case ConstantTypeCode.String:
					return blob.ReadSerializedString();
				case ConstantTypeCode.NullReference:
					return null;
				default:
					throw new NotSupportedException();
			}
		}
	}

	public struct EventDefinition : IEquatable<EventDefinition>, IMetadataEntity
	{
		public PEFile Module { get; }
		public EventDefinitionHandle Handle { get; }
		public bool IsNil => Handle.IsNil;
		EntityHandle IMetadataEntity.Handle => Handle;

		public EventDefinition(PEFile module, EventDefinitionHandle handle)
		{
			this.Module = module ?? throw new ArgumentNullException(nameof(module));
			this.Handle = handle;
		}

		public bool Equals(EventDefinition other)
		{
			return Module == other.Module && Handle == other.Handle;
		}

		public override bool Equals(object obj)
		{
			if (obj is EventDefinition ed)
				return Equals(ed);
			return false;
		}

		public override int GetHashCode()
		{
			return unchecked(982451629 * Module.GetHashCode() + 982451653 * MetadataTokens.GetToken(Handle));
		}

		public static bool operator ==(EventDefinition lhs, EventDefinition rhs) => lhs.Equals(rhs);
		public static bool operator !=(EventDefinition lhs, EventDefinition rhs) => !lhs.Equals(rhs);
	}

	public struct TypeDefinition : IEquatable<TypeDefinition>, IMetadataEntity
	{
		public PEFile Module { get; }
		public TypeDefinitionHandle Handle { get; }
		public bool IsNil => Handle.IsNil;

		EntityHandle IMetadataEntity.Handle => Handle;

		public TypeDefinition(PEFile module, TypeDefinitionHandle handle)
		{
			this.Module = module ?? throw new ArgumentNullException(nameof(module));
			this.Handle = handle;
		}

		public bool Equals(TypeDefinition other)
		{
			return Module == other.Module && Handle == other.Handle;
		}

		public override bool Equals(object obj)
		{
			if (obj is TypeDefinition td)
				return Equals(td);
			return false;
		}

		public override int GetHashCode()
		{
			return unchecked(982451629 * Module.GetHashCode() + 982451653 * MetadataTokens.GetToken(Handle));
		}

		public static bool operator ==(TypeDefinition lhs, TypeDefinition rhs) => lhs.Equals(rhs);
		public static bool operator !=(TypeDefinition lhs, TypeDefinition rhs) => !lhs.Equals(rhs);
	}

	public struct TypeReference
	{
		public PEFile Module { get; }
		public TypeReferenceHandle Handle { get; }
		public bool IsNil => Handle.IsNil;

		public TypeReference(PEFile module, TypeReferenceHandle handle)
		{
			this.Module = module ?? throw new ArgumentNullException(nameof(module));
			this.Handle = handle;
		}
	}

	public struct TypeSpecification
	{
		public PEFile Module { get; }
		public TypeSpecificationHandle Handle { get; }
		public bool IsNil => Handle.IsNil;

		public TypeSpecification(PEFile module, TypeSpecificationHandle handle)
		{
			this.Module = module ?? throw new ArgumentNullException(nameof(module));
			this.Handle = handle;
		}
	}

	public struct MethodSpecification
	{
		public PEFile Module { get; }
		public MethodSpecificationHandle Handle { get; }
		public bool IsNil => Handle.IsNil;

		public MethodSpecification(PEFile module, MethodSpecificationHandle handle)
		{
			this.Module = module ?? throw new ArgumentNullException(nameof(module));
			this.Handle = handle;
		}
	}

	public struct MemberReference
	{
		public PEFile Module { get; }
		public MemberReferenceHandle Handle { get; }
		public bool IsNil => Handle.IsNil;

		public MemberReference(PEFile module, MemberReferenceHandle handle)
		{
			this.Module = module ?? throw new ArgumentNullException(nameof(module));
			this.Handle = handle;
		}
	}

	public sealed class FullTypeNameSignatureDecoder : ISignatureTypeProvider<FullTypeName, Unit>
	{
		readonly MetadataReader metadata;

		public FullTypeNameSignatureDecoder(MetadataReader metadata)
		{
			this.metadata = metadata;
		}

		public FullTypeName GetArrayType(FullTypeName elementType, ArrayShape shape)
		{
			return elementType;
		}

		public FullTypeName GetByReferenceType(FullTypeName elementType)
		{
			return elementType;
		}

		public FullTypeName GetFunctionPointerType(MethodSignature<FullTypeName> signature)
		{
			return default;
		}

		public FullTypeName GetGenericInstantiation(FullTypeName genericType, ImmutableArray<FullTypeName> typeArguments)
		{
			return genericType;
		}

		public FullTypeName GetGenericMethodParameter(Unit genericContext, int index)
		{
			return default;
		}

		public FullTypeName GetGenericTypeParameter(Unit genericContext, int index)
		{
			return default;
		}

		public FullTypeName GetModifiedType(FullTypeName modifier, FullTypeName unmodifiedType, bool isRequired)
		{
			return unmodifiedType;
		}

		public FullTypeName GetPinnedType(FullTypeName elementType)
		{
			return elementType;
		}

		public FullTypeName GetPointerType(FullTypeName elementType)
		{
			return elementType;
		}

		public FullTypeName GetPrimitiveType(PrimitiveTypeCode typeCode)
		{
			var ktr = KnownTypeReference.Get(typeCode.ToKnownTypeCode());
			return new TopLevelTypeName(ktr.Namespace, ktr.Name, ktr.TypeParameterCount);
		}

		public FullTypeName GetSZArrayType(FullTypeName elementType)
		{
			return elementType;
		}

		public FullTypeName GetTypeFromDefinition(MetadataReader reader, TypeDefinitionHandle handle, byte rawTypeKind)
		{
			return handle.GetFullTypeName(reader);
		}

		public FullTypeName GetTypeFromReference(MetadataReader reader, TypeReferenceHandle handle, byte rawTypeKind)
		{
			return handle.GetFullTypeName(reader);
		}

		public FullTypeName GetTypeFromSpecification(MetadataReader reader, Unit genericContext, TypeSpecificationHandle handle, byte rawTypeKind)
		{
			return reader.GetTypeSpecification(handle).DecodeSignature(new FullTypeNameSignatureDecoder(metadata), default);
		}
	}

	public class GenericContext
	{
		readonly PEFile module;
		readonly TypeDefinitionHandle declaringType;
		readonly MethodDefinitionHandle method;

		public static readonly GenericContext Empty = new GenericContext();

		private GenericContext() { }

		public GenericContext(MethodDefinitionHandle method, PEFile module)
		{
			this.module = module;
			this.method = method;
			this.declaringType = module.Metadata.GetMethodDefinition(method).GetDeclaringType();
		}

		public GenericContext(MethodDefinition method)
			: this(method.Handle, method.Module)
		{
		}

		public GenericContext(TypeDefinitionHandle declaringType, PEFile module)
		{
			this.module = module;
			this.declaringType = declaringType;
		}

		public GenericContext(TypeDefinition declaringType)
			: this(declaringType.Handle, declaringType.Module)
		{
		}

		public string GetGenericTypeParameterName(int index)
		{
			GenericParameterHandle genericParameter = GetGenericTypeParameterHandleOrNull(index);
			if (genericParameter.IsNil)
				return index.ToString();
			return module.Metadata.GetString(module.Metadata.GetGenericParameter(genericParameter).Name);
		}

		public string GetGenericMethodTypeParameterName(int index)
		{
			GenericParameterHandle genericParameter = GetGenericMethodTypeParameterHandleOrNull(index);
			if (genericParameter.IsNil)
				return index.ToString();
			return module.Metadata.GetString(module.Metadata.GetGenericParameter(genericParameter).Name);
		}

		public GenericParameterHandle GetGenericTypeParameterHandleOrNull(int index)
		{
			GenericParameterHandleCollection genericParameters;
			if (declaringType.IsNil || index < 0 || index >= (genericParameters = module.Metadata.GetTypeDefinition(declaringType).GetGenericParameters()).Count)
				return MetadataTokens.GenericParameterHandle(0);
			return genericParameters[index];
		}

		public GenericParameterHandle GetGenericMethodTypeParameterHandleOrNull(int index)
		{
			GenericParameterHandleCollection genericParameters;
			if (method.IsNil || index < 0 || index >= (genericParameters = module.Metadata.GetMethodDefinition(method).GetGenericParameters()).Count)
				return MetadataTokens.GenericParameterHandle(0);
			return genericParameters[index];
		}
	}
}