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// Licensed to the .NET Foundation under one or more agreements.
// The .NET Foundation licenses this file to you under the MIT license.
using System;
using System.Collections.Generic;
using System.Globalization;
using System.Linq;
using Microsoft.AspNetCore.Http;
namespace Microsoft.AspNetCore.Routing.Constraints;
/// <summary>
/// Constrains the HTTP method of request or a route.
/// </summary>
public class HttpMethodRouteConstraint : IRouteConstraint
{
/// <summary>
/// Creates a new instance of <see cref="HttpMethodRouteConstraint"/> that accepts the HTTP methods specified
/// by <paramref name="allowedMethods"/>.
/// </summary>
/// <param name="allowedMethods">The allowed HTTP methods.</param>
public HttpMethodRouteConstraint(params string[] allowedMethods)
{
if (allowedMethods == null)
{
throw new ArgumentNullException(nameof(allowedMethods));
}
AllowedMethods = new List<string>(allowedMethods);
}
/// <summary>
/// Gets the HTTP methods allowed by the constraint.
/// </summary>
public IList<string> AllowedMethods { get; }
/// <inheritdoc />
public virtual bool Match(
HttpContext? httpContext,
IRouter? route,
string routeKey,
RouteValueDictionary values,
RouteDirection routeDirection)
{
if (routeKey == null)
{
throw new ArgumentNullException(nameof(routeKey));
}
if (values == null)
{
throw new ArgumentNullException(nameof(values));
}
switch (routeDirection)
{
case RouteDirection.IncomingRequest:
// Only required for constraining incoming requests
if (httpContext == null)
{
throw new ArgumentNullException(nameof(httpContext));
}
return AllowedMethods.Contains(httpContext.Request.Method, StringComparer.OrdinalIgnoreCase);
case RouteDirection.UrlGeneration:
// We need to see if the user specified the HTTP method explicitly. Consider these two routes:
//
// a) Route: template = "/{foo}", Constraints = { httpMethod = new HttpMethodRouteConstraint("GET") }
// b) Route: template = "/{foo}", Constraints = { httpMethod = new HttpMethodRouteConstraint("POST") }
//
// A user might know ahead of time that a URI he/she is generating might be used with a particular HTTP
// method. If a URI will be used for an HTTP POST but we match on (a) while generating the URI, then
// the HTTP GET-specific route will be used for URI generation, which might have undesired behavior.
//
// To prevent this, a user might call GetVirtualPath(..., { httpMethod = "POST" }) to
// signal that they are generating a URI that will be used for an HTTP POST, so they want the URI
// generation to be performed by the (b) route instead of the (a) route, consistent with what would
// happen on incoming requests.
if (!values.TryGetValue(routeKey, out var obj))
{
return true;
}
return AllowedMethods.Contains(Convert.ToString(obj, CultureInfo.InvariantCulture), StringComparer.OrdinalIgnoreCase);
default:
throw new ArgumentOutOfRangeException(nameof(routeDirection));
}
}
}
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