// Licensed to the .NET Foundation under one or more agreements.
// The .NET Foundation licenses this file to you under the MIT license.
 
using System.Reflection;
using Microsoft.Internal;
 
namespace System.ComponentModel.Composition.ReflectionModel
{
    // Instead of representing properties as an actual PropertyInfo, we need to
    // represent them as two MethodInfo objects one for each accessor. This is so
    // that cached attribute part can go from a metadata token -> XXXInfo without
    // needing to walk all members of a particular type. Unfortunately, (probably
    // because you never see one of them in an IL stream), Reflection does not allow
    // you to go from a metadata token -> PropertyInfo like it does with types,
    // fields, and methods.
 
    internal sealed class ReflectionProperty : ReflectionWritableMember
    {
        private readonly MethodInfo? _getMethod;
        private readonly MethodInfo? _setMethod;
 
        public ReflectionProperty(MethodInfo? getMethod, MethodInfo? setMethod)
        {
            if (getMethod == null && setMethod == null)
            {
                throw new Exception(SR.Diagnostic_InternalExceptionMessage);
            }
 
            _getMethod = getMethod;
            _setMethod = setMethod;
        }
 
        public override MemberInfo UnderlyingMember
        {
            get { return UnderlyingGetMethod ?? UnderlyingSetMethod!; }
        }
 
        public override bool CanRead
        {
            get { return UnderlyingGetMethod != null; }
        }
 
        public override bool CanWrite
        {
            get { return UnderlyingSetMethod != null; }
        }
 
        public MethodInfo? UnderlyingGetMethod
        {
            get { return _getMethod; }
        }
 
        public MethodInfo? UnderlyingSetMethod
        {
            get { return _setMethod; }
        }
 
        public override string Name
        {
            get
            {
                MethodInfo method = UnderlyingGetMethod ?? UnderlyingSetMethod!;
 
                string name = method.Name;
 
                if (name.Length <= 4)
                {
                    throw new Exception(SR.Diagnostic_InternalExceptionMessage);
                }
 
 
                // Remove 'get_' or 'set_'
                return name.Substring(4);
            }
        }
 
        public override string GetDisplayName()
        {
            return ReflectionServices.GetDisplayName(DeclaringType, Name);
        }
 
        public override bool RequiresInstance
        {
            get
            {
                MethodInfo method = UnderlyingGetMethod ?? UnderlyingSetMethod!;
 
                return !method.IsStatic;
            }
        }
 
        public override Type ReturnType
        {
            get
            {
                if (UnderlyingGetMethod != null)
                {
                    return UnderlyingGetMethod.ReturnType;
                }
 
                ParameterInfo[] parameters = UnderlyingSetMethod!.GetParameters();
 
                if (parameters.Length == 0)
                {
                    throw new Exception(SR.Diagnostic_InternalExceptionMessage);
                }
                return parameters[parameters.Length - 1].ParameterType;
            }
        }
 
        public override ReflectionItemType ItemType
        {
            get { return ReflectionItemType.Property; }
        }
 
        public override object? GetValue(object? instance)
        {
            if (_getMethod == null)
            {
                throw new Exception(SR.Diagnostic_InternalExceptionMessage);
            }
 
            return UnderlyingGetMethod!.SafeInvoke(instance);
        }
 
        public override void SetValue(object? instance, object? value)
        {
            if (_setMethod == null)
            {
                throw new Exception(SR.Diagnostic_InternalExceptionMessage);
            }
            UnderlyingSetMethod!.SafeInvoke(instance, value);
        }
 
    }
}