// Licensed to the .NET Foundation under one or more agreements.
// The .NET Foundation licenses this file to you under the MIT license.
 
using Microsoft.AspNetCore.Mvc.Core;
using Microsoft.AspNetCore.Mvc.ModelBinding;
 
namespace Microsoft.AspNetCore.Mvc;
 
/// <summary>
/// An attribute that can specify a model name or type of <see cref="IModelBinder"/> to use for binding.
/// </summary>
[AttributeUsage(
 
    // Support method parameters in actions.
    AttributeTargets.Parameter |
 
    // Support properties on model DTOs.
    AttributeTargets.Property |
 
    // Support model types.
    AttributeTargets.Class |
    AttributeTargets.Enum |
    AttributeTargets.Struct,
 
    AllowMultiple = false,
    Inherited = true)]
public class ModelBinderAttribute : Attribute, IModelNameProvider, IBinderTypeProviderMetadata
{
    private BindingSource? _bindingSource;
    private Type? _binderType;
 
    /// <summary>
    /// Initializes a new instance of <see cref="ModelBinderAttribute"/>.
    /// </summary>
    public ModelBinderAttribute()
    {
    }
 
    /// <summary>
    /// Initializes a new instance of <see cref="ModelBinderAttribute"/>.
    /// </summary>
    /// <param name="binderType">A <see cref="Type"/> which implements <see cref="IModelBinder"/>.</param>
    /// <remarks>
    /// Subclass this attribute and set <see cref="BindingSource"/> if <see cref="BindingSource.Custom"/> is not
    /// correct for the specified <paramref name="binderType"/>.
    /// </remarks>
    public ModelBinderAttribute(Type binderType)
    {
        ArgumentNullException.ThrowIfNull(binderType);
 
        BinderType = binderType;
    }
 
    /// <inheritdoc />
    /// <remarks>
    /// Subclass this attribute and set <see cref="BindingSource"/> if <see cref="BindingSource.Custom"/> is not
    /// correct for the specified (non-<see langword="null"/>) <see cref="IModelBinder"/> implementation.
    /// </remarks>
    public Type? BinderType
    {
        get => _binderType;
        set
        {
            if (value != null && !typeof(IModelBinder).IsAssignableFrom(value))
            {
                throw new ArgumentException(
                    Resources.FormatBinderType_MustBeIModelBinder(
                        value.FullName,
                        typeof(IModelBinder).FullName),
                    nameof(value));
            }
 
            _binderType = value;
        }
    }
 
    /// <inheritdoc />
    /// <value>
    /// If <see cref="BinderType"/> is <see langword="null"/>, defaults to <see langword="null"/>. Otherwise,
    /// defaults to <see cref="BindingSource.Custom"/>. May be overridden in a subclass.
    /// </value>
    public virtual BindingSource? BindingSource
    {
        get
        {
            if (_bindingSource == null && BinderType != null)
            {
                return BindingSource.Custom;
            }
 
            return _bindingSource;
        }
        protected set
        {
            _bindingSource = value;
        }
    }
 
    /// <inheritdoc />
    public string? Name { get; set; }
}