// Licensed to the .NET Foundation under one or more agreements.
// The .NET Foundation licenses this file to you under the MIT license.
 
using System.Globalization;
 
namespace Microsoft.Extensions.Validation.Localization;
 
/// <summary>
/// Formats a validation error message template with attribute-specific arguments.
/// Used by the validation localization pipeline to produce fully formatted error messages
/// from localized templates that contain positional placeholders beyond <c>{0}</c> (the display name).
/// </summary>
/// <remarks>
/// <para>
/// To add formatting support for a custom validation attribute, you have two options:
/// </para>
/// <list type="number">
///   <item>
///     <description>
///     Implement <see cref="IValidationAttributeFormatter"/> directly on the attribute itself.
///     <see cref="ValidationAttributeFormatterRegistry"/> checks for this first and uses the
///     attribute as its own formatter automatically.
///     </description>
///   </item>
///   <item>
///     <description>
///     Create a separate <see cref="IValidationAttributeFormatter"/> implementation and register
///     it via <see cref="ValidationLocalizationOptions.AttributeFormatters"/> by calling
///     <see cref="ValidationAttributeFormatterRegistry.AddFormatter{TAttribute}(Func{TAttribute, IValidationAttributeFormatter})"/>.
///     </description>
///   </item>
/// </list>
/// <example>
/// The following example shows how to register a formatter for a custom attribute:
/// <code>
/// public class MyAttributeFormatter(MyAttribute attribute) : IValidationAttributeFormatter
/// {
///     public string FormatErrorMessage(CultureInfo culture, string messageTemplate, string displayName)
///         => string.Format(culture, messageTemplate, displayName, attribute.CustomProperty);
/// }
///
/// // Register it in Program.cs:
/// builder.Services.AddValidationLocalization(options =&gt;
///     options.AttributeFormatters.AddFormatter&lt;MyAttribute&gt;(
///         attribute =&gt; new MyAttributeFormatter(attribute)));
/// </code>
/// </example>
/// </remarks>
public interface IValidationAttributeFormatter
{
    /// <summary>
    /// Formats the specified <paramref name="messageTemplate"/> by substituting attribute-specific
    /// arguments alongside the <paramref name="displayName"/>.
    /// </summary>
    /// <param name="culture">The <see cref="CultureInfo"/> to use when formatting.</param>
    /// <param name="messageTemplate">The error message template containing format placeholders.</param>
    /// <param name="displayName">The resolved display name of the member being validated.</param>
    /// <returns>The fully formatted error message.</returns>
    string FormatErrorMessage(CultureInfo culture, string messageTemplate, string displayName);
}