// Copyright (c) .NET Foundation. All rights reserved.
// Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.

using System;
using System.Threading.Tasks;

namespace Microsoft.AspNetCore.Mvc.Infrastructure
{
    /// <summary>
    /// Provides a mapping from the return value of an action to an <see cref="IActionResult"/>
    /// for request processing.
    /// </summary>
    /// <remarks>
    /// The default implementation of this service handles the conversion of 
    /// <see cref="ActionResult{TValue}"/> to an <see cref="IActionResult"/> during request
    /// processing as well as the mapping of <see cref="ActionResult{TValue}"/> to <c>TValue</c>
    /// during API Explorer processing.
    /// </remarks>
    public interface IActionResultTypeMapper
    {
        /// <summary>
        /// Gets the result data type that corresponds to <paramref name="returnType"/>. This
        /// method will not be called for actions that return <c>void</c> or an <see cref="IActionResult"/>
        /// type.
        /// </summary>
        /// <param name="returnType">The declared return type of an action.</param>
        /// <returns>A <see cref="Type"/> that represents the response data.</returns>
        /// <remarks>
        /// Prior to calling this method, the infrastructure will unwrap <see cref="Task{TResult}"/> or
        /// other task-like types.
        /// </remarks>
        Type GetResultDataType(Type returnType);

        /// <summary>
        /// Converts the result of an action to an <see cref="IActionResult"/> for response processing.
        /// This method will be not be called when a method returns <c>void</c> or an
        /// <see cref="IActionResult"/> value.
        /// </summary>
        /// <param name="value">The action return value. May be <c>null</c>.</param>
        /// <param name="returnType">The declared return type.</param>
        /// <returns>An <see cref="IActionResult"/> for response processing.</returns>
        /// <remarks>
        /// Prior to calling this method, the infrastructure will unwrap <see cref="Task{TResult}"/> or
        /// other task-like types.
        /// </remarks>
        IActionResult Convert(object value, Type returnType);
    }
}
