// Licensed to the .NET Foundation under one or more agreements.
// The .NET Foundation licenses this file to you under the MIT license.
 
using System.Collections.Concurrent;
using System.ComponentModel;
using System.ComponentModel.DataAnnotations;
using System.Linq.Expressions;
using System.Reflection;
using Microsoft.AspNetCore.Components.HotReload;
 
namespace Microsoft.AspNetCore.Components.Forms;
 
internal static class ExpressionMemberAccessor
{
    private static readonly ConcurrentDictionary<Expression, MemberInfo> _memberInfoCache = new();
    private static readonly ConcurrentDictionary<MemberInfo, string> _displayNameCache = new();
 
    static ExpressionMemberAccessor()
    {
        if (HotReloadManager.Default.MetadataUpdateSupported)
        {
            HotReloadManager.Default.OnDeltaApplied += ClearCache;
        }
    }
 
    private static MemberInfo GetMemberInfo<TValue>(Expression<Func<TValue>> accessor)
    {
        ArgumentNullException.ThrowIfNull(accessor);
 
        return _memberInfoCache.GetOrAdd(accessor, static expr =>
        {
            var lambdaExpression = (LambdaExpression)expr;
            var accessorBody = lambdaExpression.Body;
 
            if (accessorBody is UnaryExpression unaryExpression
                && unaryExpression.NodeType == ExpressionType.Convert
                && unaryExpression.Type == typeof(object))
            {
                accessorBody = unaryExpression.Operand;
            }
 
            if (accessorBody is not MemberExpression memberExpression)
            {
                throw new ArgumentException(
                    $"The provided expression contains a {accessorBody.GetType().Name} which is not supported. " +
                    $"Only simple member accessors (fields, properties) of an object are supported.");
            }
 
            return memberExpression.Member;
        });
    }
 
    public static string GetDisplayName(MemberInfo member)
    {
        ArgumentNullException.ThrowIfNull(member);
 
        return _displayNameCache.GetOrAdd(member, static m =>
        {
            var displayAttribute = m.GetCustomAttribute<DisplayAttribute>();
            if (displayAttribute is not null)
            {
                var name = displayAttribute.GetName();
                if (name is not null)
                {
                    return name;
                }
            }
 
            var displayNameAttribute = m.GetCustomAttribute<DisplayNameAttribute>();
            if (displayNameAttribute?.DisplayName is not null)
            {
                return displayNameAttribute.DisplayName;
            }
 
            return m.Name;
        });
    }
 
    public static string GetDisplayName<TValue>(Expression<Func<TValue>> accessor)
    {
        ArgumentNullException.ThrowIfNull(accessor);
        var member = GetMemberInfo(accessor);
        return GetDisplayName(member);
    }
 
    private static void ClearCache()
    {
        _memberInfoCache.Clear();
        _displayNameCache.Clear();
    }
}