// This file is part of YamlDotNet - A .NET library for YAML.
// Copyright (c) Antoine Aubry and contributors
//
// Permission is hereby granted, free of charge, to any person obtaining a copy of
// this software and associated documentation files (the "Software"), to deal in
// the Software without restriction, including without limitation the rights to
// use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies
// of the Software, and to permit persons to whom the Software is furnished to do
// so, subject to the following conditions:
//
// The above copyright notice and this permission notice shall be included in all
// copies or substantial portions of the Software.
//
// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
// OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
// SOFTWARE.

#if !NET20

using System;
using System.Diagnostics.CodeAnalysis;
using System.Linq.Expressions;
using System.Reflection;

namespace YamlDotNet.Helpers
{
    public static class ExpressionExtensions
    {
        /// <summary>
        /// Returns the <see cref="PropertyInfo" /> that describes the property that
        /// is being returned in an expression in the form:
        /// <code>
        ///   x => x.SomeProperty
        /// </code>
        /// </summary>
        public static PropertyInfo AsProperty(this LambdaExpression propertyAccessor)
        {
            var property = TryGetMemberExpression<PropertyInfo>(propertyAccessor);
            if (property == null)
            {
                throw new ArgumentException("Expected a lambda expression in the form: x => x.SomeProperty", nameof(propertyAccessor));
            }

            return property;
        }

        [return: MaybeNull]
        private static TMemberInfo TryGetMemberExpression<TMemberInfo>(LambdaExpression lambdaExpression)
            where TMemberInfo : MemberInfo
        {
            if (lambdaExpression.Parameters.Count != 1)
            {
                return null;
            }

            var body = lambdaExpression.Body;

            if (body is UnaryExpression castExpression)
            {
                if (castExpression.NodeType != ExpressionType.Convert)
                {
                    return null;
                }

                body = castExpression.Operand;
            }

            if (body is MemberExpression memberExpression)
            {
                if (memberExpression.Expression != lambdaExpression.Parameters[0])
                {
                    return null;
                }

                return memberExpression.Member as TMemberInfo;
            }
            return null;
        }
    }
}
#endif
