//
// pending.cs: Pending method implementation
//
// Authors:
//   Miguel de Icaza (miguel@gnu.org)
//   Marek Safar (marek.safar@gmail.com)
//
// Dual licensed under the terms of the MIT X11 or GNU GPL
//
// Copyright 2001, 2002 Ximian, Inc (http://www.ximian.com)
// Copyright 2003-2008 Novell, Inc.
//

using System.Collections.Generic;
using System.Linq;

#if STATIC
using IKVM.Reflection;
using IKVM.Reflection.Emit;
#else
using System.Reflection;
using System.Reflection.Emit;
#endif

namespace Mono.CSharp {

	struct TypeAndMethods {
		public TypeSpec          type;
		public IList<MethodSpec> methods;

		// 
		// Whether it is optional, this is used to allow the explicit/implicit
		// implementation when a base class already implements an interface. 
		//
		// For example:
		//
		// class X : IA { }  class Y : X, IA { IA.Explicit (); }
		//
		public bool          optional;
				
		//
		// This flag on the method says `We found a match, but
		// because it was private, we could not use the match
		//
		public MethodData [] found;

		// If a method is defined here, then we always need to
		// create a proxy for it.  This is used when implementing
		// an interface's indexer with a different IndexerName.
		public MethodSpec [] need_proxy;
	}

	public class PendingImplementation
	{
		/// <summary>
		///   The container for this PendingImplementation
		/// </summary>
		TypeContainer container;
		
		/// <summary>
		///   This is the array of TypeAndMethods that describes the pending implementations
		///   (both interfaces and abstract methods in base class)
		/// </summary>
		TypeAndMethods [] pending_implementations;

		PendingImplementation (TypeContainer container, MissingInterfacesInfo[] missing_ifaces, MethodSpec[] abstract_methods, int total)
		{
			var type_builder = container.Definition;
			
			this.container = container;
			pending_implementations = new TypeAndMethods [total];

			int i = 0;
			if (abstract_methods != null) {
				int count = abstract_methods.Length;
				pending_implementations [i].methods = new MethodSpec [count];
				pending_implementations [i].need_proxy = new MethodSpec [count];

				pending_implementations [i].methods = abstract_methods;
				pending_implementations [i].found = new MethodData [count];
				pending_implementations [i].type = type_builder;
				++i;
			}

			foreach (MissingInterfacesInfo missing in missing_ifaces) {
				var iface = missing.Type;
				var mi = MemberCache.GetInterfaceMethods (iface);

				int count = mi.Count;
				pending_implementations [i].type = iface;
				pending_implementations [i].optional = missing.Optional;
				pending_implementations [i].methods = mi;
				pending_implementations [i].found = new MethodData [count];
				pending_implementations [i].need_proxy = new MethodSpec [count];
				i++;
			}
		}

		struct MissingInterfacesInfo {
			public TypeSpec Type;
			public bool Optional;

			public MissingInterfacesInfo (TypeSpec t)
			{
				Type = t;
				Optional = false;
			}
		}

		static MissingInterfacesInfo [] EmptyMissingInterfacesInfo = new MissingInterfacesInfo [0];
		
		static MissingInterfacesInfo [] GetMissingInterfaces (TypeContainer container)
		{
			//
			// Notice that Interfaces will only return the interfaces that the Type
			// is supposed to implement, not all the interfaces that the type implements.
			//
			var impl = container.Definition.Interfaces;

			if (impl == null || impl.Count == 0)
				return EmptyMissingInterfacesInfo;

			MissingInterfacesInfo[] ret = new MissingInterfacesInfo[impl.Count];

			for (int i = 0; i < impl.Count; i++)
				ret [i] = new MissingInterfacesInfo (impl [i]);

			// we really should not get here because Object doesnt implement any
			// interfaces. But it could implement something internal, so we have
			// to handle that case.
			if (container.BaseType == null)
				return ret;
			
			var base_impls = container.BaseType.Interfaces;
			if (base_impls != null) {
				foreach (TypeSpec t in base_impls) {
					for (int i = 0; i < ret.Length; i++) {
						if (t == ret[i].Type) {
							ret[i].Optional = true;
							break;
						}
					}
				}
			}

			return ret;
		}
		
		//
		// Factory method: if there are pending implementation methods, we return a PendingImplementation
		// object, otherwise we return null.
		//
		// Register method implementations are either abstract methods
		// flagged as such on the base class or interface methods
		//
		static public PendingImplementation GetPendingImplementations (TypeContainer container)
		{
			TypeSpec b = container.BaseType;

			var missing_interfaces = GetMissingInterfaces (container);

			//
			// If we are implementing an abstract class, and we are not
			// ourselves abstract, and there are abstract methods (C# allows
			// abstract classes that have no abstract methods), then allocate
			// one slot.
			//
			// We also pre-compute the methods.
			//
			bool implementing_abstract = ((b != null) && b.IsAbstract && (container.ModFlags & Modifiers.ABSTRACT) == 0);
			MethodSpec[] abstract_methods = null;

			if (implementing_abstract){
				var am = MemberCache.GetNotImplementedAbstractMethods (b);

				if (am == null) {
					implementing_abstract = false;
				} else {
					abstract_methods = new MethodSpec[am.Count];
					am.CopyTo (abstract_methods, 0);
				}
			}
			
			int total = missing_interfaces.Length +  (implementing_abstract ? 1 : 0);
			if (total == 0)
				return null;

			return new PendingImplementation (container, missing_interfaces, abstract_methods, total);
		}

		public enum Operation {
			//
			// If you change this, review the whole InterfaceMethod routine as there
			// are a couple of assumptions on these three states
			//
			Lookup, ClearOne, ClearAll
		}

		/// <summary>
		///   Whether the specified method is an interface method implementation
		/// </summary>
		public MethodSpec IsInterfaceMethod (MemberName name, TypeSpec ifaceType, MethodData method)
		{
			return InterfaceMethod (name, ifaceType, method, Operation.Lookup);
		}

		public void ImplementMethod (MemberName name, TypeSpec ifaceType, MethodData method, bool clear_one) 
		{
			InterfaceMethod (name, ifaceType, method, clear_one ? Operation.ClearOne : Operation.ClearAll);
		}

		/// <remarks>
		///   If a method in Type `t' (or null to look in all interfaces
		///   and the base abstract class) with name `Name', return type `ret_type' and
		///   arguments `args' implements an interface, this method will
		///   return the MethodInfo that this method implements.
		///
		///   If `name' is null, we operate solely on the method's signature.  This is for
		///   instance used when implementing indexers.
		///
		///   The `Operation op' controls whether to lookup, clear the pending bit, or clear
		///   all the methods with the given signature.
		///
		///   The `MethodInfo need_proxy' is used when we're implementing an interface's
		///   indexer in a class.  If the new indexer's IndexerName does not match the one
		///   that was used in the interface, then we always need to create a proxy for it.
		///
		/// </remarks>
		public MethodSpec InterfaceMethod (MemberName name, TypeSpec iType, MethodData method, Operation op)
		{
			if (pending_implementations == null)
				return null;

			TypeSpec ret_type = method.method.ReturnType;
			ParametersCompiled args = method.method.ParameterInfo;
			bool is_indexer = method.method is Indexer.SetIndexerMethod || method.method is Indexer.GetIndexerMethod;

			foreach (TypeAndMethods tm in pending_implementations){
				if (!(iType == null || tm.type == iType))
					continue;

				int method_count = tm.methods.Count;
				MethodSpec m;
				for (int i = 0; i < method_count; i++){
					m = tm.methods [i];

					if (m == null)
						continue;

					if (is_indexer) {
						if (!m.IsAccessor || m.Parameters.IsEmpty)
							continue;
					} else {
						if (name.Name != m.Name)
							continue;

						if (m.Arity != name.Arity)
							continue;
					}

					if (!TypeSpecComparer.Override.IsEqual (m.Parameters, args))
						continue;

					if (!TypeSpecComparer.Override.IsEqual (m.ReturnType, ret_type)) {
						tm.found[i] = method;
						continue;
					}

					//
					// `need_proxy' is not null when we're implementing an
					// interface indexer and this is Clear(One/All) operation.
					//
					// If `name' is null, then we do a match solely based on the
					// signature and not on the name (this is done in the Lookup
					// for an interface indexer).
					//
					if (op != Operation.Lookup) {
						// If `t != null', then this is an explicitly interface
						// implementation and we can always clear the method.
						// `need_proxy' is not null if we're implementing an
						// interface indexer.  In this case, we need to create
						// a proxy if the implementation's IndexerName doesn't
						// match the IndexerName in the interface.
						if (m.DeclaringType.IsInterface && iType == null && name.Name != m.Name) {	// TODO: This is very expensive comparison
							tm.need_proxy[i] = method.method.Spec;
						} else {
							tm.methods[i] = null;
						}
					} else {
						tm.found [i] = method;
					}

					//
					// Lookups and ClearOne return
					//
					if (op != Operation.ClearAll)
						return m;
				}

				// If a specific type was requested, we can stop now.
				if (tm.type == iType)
					return null;
			}
			return null;
		}

		/// <summary>
		///   C# allows this kind of scenarios:
		///   interface I { void M (); }
		///   class X { public void M (); }
		///   class Y : X, I { }
		///
		///   For that case, we create an explicit implementation function
		///   I.M in Y.
		/// </summary>
		void DefineProxy (TypeSpec iface, MethodSpec base_method, MethodSpec iface_method)
		{
			// TODO: Handle nested iface names
			string proxy_name;
			var ns = iface.MemberDefinition.Namespace;
			if (string.IsNullOrEmpty (ns))
				proxy_name = iface.MemberDefinition.Name + "." + iface_method.Name;
			else
				proxy_name = ns + "." + iface.MemberDefinition.Name + "." + iface_method.Name;

			var param = iface_method.Parameters;

			MethodBuilder proxy = container.TypeBuilder.DefineMethod (
				proxy_name,
				MethodAttributes.HideBySig |
				MethodAttributes.NewSlot |
				MethodAttributes.CheckAccessOnOverride |
				MethodAttributes.Virtual,
				CallingConventions.Standard | CallingConventions.HasThis,
				base_method.ReturnType.GetMetaInfo (), param.GetMetaInfo ());

			if (iface_method.IsGeneric) {
				var gnames = iface_method.GenericDefinition.TypeParameters.Select (l => l.Name).ToArray ();
				proxy.DefineGenericParameters (gnames);
			}

			for (int i = 0; i < param.Count; i++) {
				string name = param.FixedParameters [i].Name;
				ParameterAttributes attr = ParametersCompiled.GetParameterAttribute (param.FixedParameters [i].ModFlags);
				proxy.DefineParameter (i + 1, attr, name);
			}

			int top = param.Count;
			var ec = new EmitContext (null, proxy.GetILGenerator (), null);
			// TODO: GetAllParametersArguments
			for (int i = 0; i <= top; i++)
				ParameterReference.EmitLdArg (ec, i);

			ec.Emit (OpCodes.Call, base_method);
			ec.Emit (OpCodes.Ret);

			container.TypeBuilder.DefineMethodOverride (proxy, (MethodInfo) iface_method.GetMetaInfo ());
		}
		
		/// <summary>
		///   This function tells whether one of our base classes implements
		///   the given method (which turns out, it is valid to have an interface
		///   implementation in a base
		/// </summary>
		bool BaseImplements (TypeSpec iface_type, MethodSpec mi, out MethodSpec base_method)
		{
			var base_type = container.BaseType;

			//
			// Setup filter with no return type to give better error message
			// about mismatch at return type when the check bellow rejects them
			//
			var filter = new MemberFilter (mi.Name, mi.Arity, MemberKind.Method, mi.Parameters, null);

			base_method = (MethodSpec) MemberCache.FindMember (base_type, filter, BindingRestriction.None);

			if (base_method == null || (base_method.Modifiers & Modifiers.PUBLIC) == 0)
				return false;

			if (base_method.DeclaringType.IsInterface)
				return false;

			if (!TypeSpecComparer.Override.IsEqual (mi.ReturnType, base_method.ReturnType))
				return false;

			if (!base_method.IsAbstract && !base_method.IsVirtual)
				// FIXME: We can avoid creating a proxy if base_method can be marked 'final virtual' instead.
				//        However, it's too late now, the MethodBuilder has already been created (see bug 377519)
				DefineProxy (iface_type, base_method, mi);

			return true;
		}

		/// <summary>
		///   Verifies that any pending abstract methods or interface methods
		///   were implemented.
		/// </summary>
		public bool VerifyPendingMethods (Report Report)
		{
			int top = pending_implementations.Length;
			bool errors = false;
			int i;
			
			for (i = 0; i < top; i++){
				TypeSpec type = pending_implementations [i].type;

				bool base_implements_type = type.IsInterface &&
					container.BaseType != null &&
					container.BaseType.ImplementsInterface (type, false);

				for (int j = 0; j < pending_implementations [i].methods.Count; ++j) {
					var mi = pending_implementations[i].methods[j];
					if (mi == null)
						continue;

					if (type.IsInterface){
						var need_proxy =
							pending_implementations [i].need_proxy [j];

						if (need_proxy != null) {
							DefineProxy (type, need_proxy, mi);
							continue;
						}

						if (pending_implementations [i].optional)
							continue;

						MethodSpec candidate = null;
						if (base_implements_type || BaseImplements (type, mi, out candidate))
							continue;

						if (candidate == null) {
							MethodData md = pending_implementations [i].found [j];
							if (md != null)
								candidate = md.method.Spec;
						}

						Report.SymbolRelatedToPreviousError (mi);
						if (candidate != null) {
							Report.SymbolRelatedToPreviousError (candidate);
							if (candidate.IsStatic) {
								Report.Error (736, container.Location,
									"`{0}' does not implement interface member `{1}' and the best implementing candidate `{2}' is static",
									container.GetSignatureForError (), mi.GetSignatureForError (), TypeManager.CSharpSignature (candidate));
							} else if ((candidate.Modifiers & Modifiers.PUBLIC) == 0) {
								Report.Error (737, container.Location,
									"`{0}' does not implement interface member `{1}' and the best implementing candidate `{2}' in not public",
									container.GetSignatureForError (), mi.GetSignatureForError (), candidate.GetSignatureForError ());
							} else {
								Report.Error (738, container.Location,
									"`{0}' does not implement interface member `{1}' and the best implementing candidate `{2}' return type `{3}' does not match interface member return type `{4}'",
									container.GetSignatureForError (), mi.GetSignatureForError (), TypeManager.CSharpSignature (candidate),
									TypeManager.CSharpName (candidate.ReturnType), TypeManager.CSharpName (mi.ReturnType));
							}
						} else {
							Report.Error (535, container.Location, "`{0}' does not implement interface member `{1}'",
								container.GetSignatureForError (), mi.GetSignatureForError ());
						}
					} else {
						Report.SymbolRelatedToPreviousError (mi);
						Report.Error (534, container.Location, "`{0}' does not implement inherited abstract member `{1}'",
							container.GetSignatureForError (), mi.GetSignatureForError ());
					}
					errors = true;
				}
			}
			return errors;
		}
	}
}