// Licensed to the .NET Foundation under one or more agreements.
// The .NET Foundation licenses this file to you under the MIT license.
// See the LICENSE file in the project root for more information.

using System.Globalization;
using System.Diagnostics;
using System.Runtime.CompilerServices;
using System.Text;

namespace System.Reflection
{
    public abstract partial class MethodBase : MemberInfo
    {
        protected MethodBase() { }

        public abstract ParameterInfo[] GetParameters();
        public abstract MethodAttributes Attributes { get; }
        public virtual MethodImplAttributes MethodImplementationFlags => GetMethodImplementationFlags();
        public abstract MethodImplAttributes GetMethodImplementationFlags();
        public virtual MethodBody? GetMethodBody() { throw new InvalidOperationException(); }
        public virtual CallingConventions CallingConvention => CallingConventions.Standard;

        public bool IsAbstract => (Attributes & MethodAttributes.Abstract) != 0;
        public bool IsConstructor =>
            // To be backward compatible we only return true for instance RTSpecialName ctors.
            this is ConstructorInfo &&
            !IsStatic &&
            (Attributes & MethodAttributes.RTSpecialName) == MethodAttributes.RTSpecialName;
        public bool IsFinal => (Attributes & MethodAttributes.Final) != 0;
        public bool IsHideBySig => (Attributes & MethodAttributes.HideBySig) != 0;
        public bool IsSpecialName => (Attributes & MethodAttributes.SpecialName) != 0;
        public bool IsStatic => (Attributes & MethodAttributes.Static) != 0;
        public bool IsVirtual => (Attributes & MethodAttributes.Virtual) != 0;

        public bool IsAssembly => (Attributes & MethodAttributes.MemberAccessMask) == MethodAttributes.Assembly;
        public bool IsFamily => (Attributes & MethodAttributes.MemberAccessMask) == MethodAttributes.Family;
        public bool IsFamilyAndAssembly => (Attributes & MethodAttributes.MemberAccessMask) == MethodAttributes.FamANDAssem;
        public bool IsFamilyOrAssembly => (Attributes & MethodAttributes.MemberAccessMask) == MethodAttributes.FamORAssem;
        public bool IsPrivate => (Attributes & MethodAttributes.MemberAccessMask) == MethodAttributes.Private;
        public bool IsPublic => (Attributes & MethodAttributes.MemberAccessMask) == MethodAttributes.Public;

        public virtual bool IsConstructedGenericMethod => IsGenericMethod && !IsGenericMethodDefinition;
        public virtual bool IsGenericMethod => false;
        public virtual bool IsGenericMethodDefinition => false;
        public virtual Type[] GetGenericArguments() { throw new NotSupportedException(SR.NotSupported_SubclassOverride); }
        public virtual bool ContainsGenericParameters => false;

        [DebuggerHidden]
        [DebuggerStepThrough]
        public object? Invoke(object? obj, object?[]? parameters) => Invoke(obj, BindingFlags.Default, binder: null, parameters: parameters, culture: null);
        public abstract object? Invoke(object? obj, BindingFlags invokeAttr, Binder? binder, object?[]? parameters, CultureInfo? culture);

        public abstract RuntimeMethodHandle MethodHandle { get; }

        public virtual bool IsSecurityCritical => throw NotImplemented.ByDesign;
        public virtual bool IsSecuritySafeCritical => throw NotImplemented.ByDesign;
        public virtual bool IsSecurityTransparent => throw NotImplemented.ByDesign;

        public override bool Equals(object? obj) => base.Equals(obj);
        public override int GetHashCode() => base.GetHashCode();

        [MethodImpl(MethodImplOptions.AggressiveInlining)]
        public static bool operator ==(MethodBase? left, MethodBase? right)
        {
            // Test "right" first to allow branch elimination when inlined for null checks (== null)
            // so it can become a simple test
            if (right is null)
            {
                // return true/false not the test result https://github.com/dotnet/coreclr/issues/914
                return (left is null) ? true : false;
            }

            // Try fast reference equality and opposite null check prior to calling the slower virtual Equals
            if ((object?)left == (object)right)
            {
                return true;
            }

            return (left is null) ? false : left.Equals(right);
        }

        public static bool operator !=(MethodBase? left, MethodBase? right) => !(left == right);

        internal const int MethodNameBufferSize = 100;

        internal static void AppendParameters(ref ValueStringBuilder sbParamList, Type[] parameterTypes, CallingConventions callingConvention)
        {
            string comma = "";

            for (int i = 0; i < parameterTypes.Length; i++)
            {
                Type t = parameterTypes[i];

                sbParamList.Append(comma);

                string typeName = t.FormatTypeName();

                // Legacy: Why use "ByRef" for by ref parameters? What language is this?
                // VB uses "ByRef" but it should precede (not follow) the parameter name.
                // Why don't we just use "&"?
                if (t.IsByRef)
                {
                    sbParamList.Append(typeName.AsSpan().TrimEnd('&'));
                    sbParamList.Append(" ByRef");
                }
                else
                {
                    sbParamList.Append(typeName);
                }

                comma = ", ";
            }

            if ((callingConvention & CallingConventions.VarArgs) == CallingConventions.VarArgs)
            {
                sbParamList.Append(comma);
                sbParamList.Append("...");
            }
        }
    }
}