// 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 Microsoft.AspNetCore.Mvc.ActionConstraints;

namespace Microsoft.AspNetCore.Mvc.Internal
{
    /// <summary>
    /// A default implementation of <see cref="IActionConstraintProvider"/>.
    /// </summary>
    /// <remarks>
    /// This provider is able to provide an <see cref="IActionConstraint"/> instance when the
    /// <see cref="IActionConstraintMetadata"/> implements <see cref="IActionConstraint"/> or
    /// <see cref="IActionConstraintFactory"/>/
    /// </remarks>
    public class DefaultActionConstraintProvider : IActionConstraintProvider
    {
        /// <inheritdoc />
        public int Order => -1000;

        /// <inheritdoc />
        public void OnProvidersExecuting(ActionConstraintProviderContext context)
        {
            if (context == null)
            {
                throw new ArgumentNullException(nameof(context));
            }

            for (var i = 0; i < context.Results.Count; i++)
            {
                ProvideConstraint(context.Results[i], context.HttpContext.RequestServices);
            }
        }

        /// <inheritdoc />
        public void OnProvidersExecuted(ActionConstraintProviderContext context)
        {
        }

        private void ProvideConstraint(ActionConstraintItem item, IServiceProvider services)
        {
            // Don't overwrite anything that was done by a previous provider.
            if (item.Constraint != null)
            {
                return;
            }

            var constraint = item.Metadata as IActionConstraint;
            if (constraint != null)
            {
                item.Constraint = constraint;
                item.IsReusable = true;
                return;
            }

            var factory = item.Metadata as IActionConstraintFactory;
            if (factory != null)
            {
                item.Constraint = factory.CreateInstance(services);
                item.IsReusable = factory.IsReusable;
                return;
            }
        }
    }
}