Fixes: #4597 Parse URI path with an endpoint

Adds functionality to LinkGenerator to parse a URI path given a way to
find an endpoint. This is the replacement for various machinications
using the global route collection and `RouteData.Routers` in earlier
versions.

For now I'm just adding a way to do this using Endpoint Name since it's
a pretty low level feature. Endpoint Name is also very direct, so it
feels good for something like this.

I added this to LinkGenerator because I think it feels like the right
thing do, despite the naming conflict. I don't really want to create a
new top-level service for this.

Author: Ryan Nowak

src/Http/Routing/ref/Microsoft.AspNetCore.Routing.netcoreapp3.0.cs

@@ -193,6 +193,15 @@ public static partial class LinkGeneratorRouteValuesAddressExtensions
         public static string GetUriByRouteValues(this Microsoft.AspNetCore.Routing.LinkGenerator generator, Microsoft.AspNetCore.Http.HttpContext httpContext, string routeName, object values, string scheme = null, Microsoft.AspNetCore.Http.HostString? host = default(Microsoft.AspNetCore.Http.HostString?), Microsoft.AspNetCore.Http.PathString? pathBase = default(Microsoft.AspNetCore.Http.PathString?), Microsoft.AspNetCore.Http.FragmentString fragment = default(Microsoft.AspNetCore.Http.FragmentString), Microsoft.AspNetCore.Routing.LinkOptions options = null) { throw null; }
         public static string GetUriByRouteValues(this Microsoft.AspNetCore.Routing.LinkGenerator generator, string routeName, object values, string scheme, Microsoft.AspNetCore.Http.HostString host, Microsoft.AspNetCore.Http.PathString pathBase = default(Microsoft.AspNetCore.Http.PathString), Microsoft.AspNetCore.Http.FragmentString fragment = default(Microsoft.AspNetCore.Http.FragmentString), Microsoft.AspNetCore.Routing.LinkOptions options = null) { throw null; }
     }
+    public abstract partial class LinkParser
+    {
+        protected LinkParser() { }
+        public abstract Microsoft.AspNetCore.Routing.RouteValueDictionary ParsePathByAddress<TAddress>(TAddress address, Microsoft.AspNetCore.Http.PathString path);
+    }
+    public static partial class LinkParserEndpointNameAddressExtensions
+    {
+        public static Microsoft.AspNetCore.Routing.RouteValueDictionary ParsePathByEndpointName(this Microsoft.AspNetCore.Routing.LinkParser parser, string endpointName, Microsoft.AspNetCore.Http.PathString path) { throw null; }
+    }
     public abstract partial class MatcherPolicy
     {
         protected MatcherPolicy() { }

src/Http/Routing/src/DefaultLinkParser.cs

@@ -0,0 +1,236 @@
+// 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.Collections.Concurrent;
+using System.Collections.Generic;
+using System.Linq;
+using Microsoft.AspNetCore.Http;
+using Microsoft.Extensions.DependencyInjection;
+using Microsoft.Extensions.Logging;
+
+namespace Microsoft.AspNetCore.Routing
+{
+    internal class DefaultLinkParser : LinkParser, IDisposable
+    {
+        private readonly ParameterPolicyFactory _parameterPolicyFactory;
+        private readonly ILogger<DefaultLinkParser> _logger;
+        private readonly IServiceProvider _serviceProvider;
+
+        // Caches RoutePatternMatcher instances
+        private readonly DataSourceDependentCache<ConcurrentDictionary<RouteEndpoint, MatcherState>> _matcherCache;
+
+        // Used to initialize RoutePatternMatcher and constraint instances
+        private readonly Func<RouteEndpoint, MatcherState> _createMatcher;
+
+        public DefaultLinkParser(
+            ParameterPolicyFactory parameterPolicyFactory,
+            EndpointDataSource dataSource,
+            ILogger<DefaultLinkParser> logger,
+            IServiceProvider serviceProvider)
+        {
+            _parameterPolicyFactory = parameterPolicyFactory;
+            _logger = logger;
+            _serviceProvider = serviceProvider;
+
+            // We cache RoutePatternMatcher instances per-Endpoint for performance, but we want to wipe out
+            // that cache is the endpoints change so that we don't allow unbounded memory growth.
+            _matcherCache = new DataSourceDependentCache<ConcurrentDictionary<RouteEndpoint, MatcherState>>(dataSource, (_) =>
+            {
+                // We don't eagerly fill this cache because there's no real reason to. Unlike URL matching, we don't
+                // need to build a big data structure up front to be correct.
+                return new ConcurrentDictionary<RouteEndpoint, MatcherState>();
+            });
+
+            // Cached to avoid per-call allocation of a delegate on lookup.
+            _createMatcher = CreateRoutePatternMatcher;
+        }
+
+        public override RouteValueDictionary ParsePathByAddress<TAddress>(TAddress address, PathString path)
+        {
+            var endpoints = GetEndpoints(address);
+            if (endpoints.Count == 0)
+            {
+                return null;
+            }
+
+            for (var i = 0; i < endpoints.Count; i++)
+            {
+                var endpoint = endpoints[i];
+                if (TryParse(endpoint, path, out var values))
+                {
+                    Log.PathParsingSucceeded(_logger, path, endpoints);
+                    return values;
+                }
+            }
+
+            Log.PathParsingFailed(_logger, path, endpoints);
+            return null;
+        }
+
+        private List<RouteEndpoint> GetEndpoints<TAddress>(TAddress address)
+        {
+            var addressingScheme = _serviceProvider.GetRequiredService<IEndpointAddressScheme<TAddress>>();
+            var endpoints = addressingScheme.FindEndpoints(address).OfType<RouteEndpoint>().ToList();
+
+            if (endpoints.Count == 0)
+            {
+                Log.EndpointsNotFound(_logger, address);
+            }
+            else
+            {
+                Log.EndpointsFound(_logger, address, endpoints);
+            }
+
+            return endpoints;
+        }
+
+
+        private MatcherState CreateRoutePatternMatcher(RouteEndpoint endpoint)
+        {
+            var constraints = new Dictionary<string, List<IRouteConstraint>>(StringComparer.OrdinalIgnoreCase);
+
+            var policies = endpoint.RoutePattern.ParameterPolicies;
+            foreach (var kvp in policies)
+            {
+                var constraintsForParameter = new List<IRouteConstraint>();
+                var parameter = endpoint.RoutePattern.GetParameter(kvp.Key);
+                for (var i = 0; i < kvp.Value.Count; i++)
+                {
+                    var policy = _parameterPolicyFactory.Create(parameter, kvp.Value[i]);
+                    if (policy is IRouteConstraint constraint)
+                    {
+                        constraintsForParameter.Add(constraint);
+                    }
+                }
+
+                if (constraintsForParameter.Count > 0)
+                {
+                    constraints.Add(kvp.Key, constraintsForParameter);
+                }
+            }
+
+            var matcher = new RoutePatternMatcher(endpoint.RoutePattern, new RouteValueDictionary(endpoint.RoutePattern.Defaults));
+            return new MatcherState(matcher, constraints);
+        }
+
+        // Internal for testing
+        internal MatcherState GetMatcherState(RouteEndpoint endpoint) => _matcherCache.EnsureInitialized().GetOrAdd(endpoint, _createMatcher);
+
+        // Internal for testing
+        internal bool TryParse(RouteEndpoint endpoint, PathString path, out RouteValueDictionary values)
+        {
+            var (matcher, constraints) = GetMatcherState(endpoint);
+
+            values = new RouteValueDictionary();
+            if (!matcher.TryMatch(path, values))
+            {
+                values = null;
+                return false;
+            }
+
+            foreach (var kvp in constraints)
+            {
+                for (var i = 0; i < kvp.Value.Count; i++)
+                {
+                    var constraint = kvp.Value[i];
+                    if (!constraint.Match(httpContext: null, NullRouter.Instance, kvp.Key, values, RouteDirection.IncomingRequest))
+                    {
+                        values = null;
+                        return false;
+                    }
+                }
+            }
+
+            return true;
+        }
+
+        public void Dispose()
+        {
+            _matcherCache.Dispose();
+        }
+
+        // internal for testing
+        internal readonly struct MatcherState
+        {
+            public readonly RoutePatternMatcher Matcher;
+            public readonly Dictionary<string, List<IRouteConstraint>> Constraints;
+
+            public MatcherState(RoutePatternMatcher matcher, Dictionary<string, List<IRouteConstraint>> constraints)
+            {
+                Matcher = matcher;
+                Constraints = constraints;
+            }
+
+            public void Deconstruct(out RoutePatternMatcher matcher, out Dictionary<string, List<IRouteConstraint>> constraints)
+            {
+                matcher = Matcher;
+                constraints = Constraints;
+            }
+        }
+
+        private static class Log
+        {
+            public static class EventIds
+            {
+                public static readonly EventId EndpointsFound = new EventId(100, "EndpointsFound");
+                public static readonly EventId EndpointsNotFound = new EventId(101, "EndpointsNotFound");
+
+                public static readonly EventId PathParsingSucceeded = new EventId(102, "PathParsingSucceeded");
+                public static readonly EventId PathParsingFailed = new EventId(103, "PathParsingFailed");
+            }
+
+            private static readonly Action<ILogger, IEnumerable<string>, object, Exception> _endpointsFound = LoggerMessage.Define<IEnumerable<string>, object>(
+                LogLevel.Debug,
+                EventIds.EndpointsFound,
+                "Found the endpoints {Endpoints} for address {Address}");
+
+            private static readonly Action<ILogger, object, Exception> _endpointsNotFound = LoggerMessage.Define<object>(
+                LogLevel.Debug,
+                EventIds.EndpointsNotFound,
+                "No endpoints found for address {Address}");
+
+            private static readonly Action<ILogger, IEnumerable<string>, string, Exception> _pathParsingSucceeded = LoggerMessage.Define<IEnumerable<string>, string>(
+                LogLevel.Debug,
+                EventIds.PathParsingSucceeded,
+                "Path parsing succeeded for endpoints {Endpoints} and URI path {URI}");
+
+            private static readonly Action<ILogger, IEnumerable<string>, string, Exception> _pathParsingFailed = LoggerMessage.Define<IEnumerable<string>, string>(
+                LogLevel.Debug,
+                EventIds.PathParsingFailed,
+                "Path parsing failed for endpoints {Endpoints} and URI path {URI}");
+
+            public static void EndpointsFound(ILogger logger, object address, IEnumerable<Endpoint> endpoints)
+            {
+                // Checking level again to avoid allocation on the common path
+                if (logger.IsEnabled(LogLevel.Debug))
+                {
+                    _endpointsFound(logger, endpoints.Select(e => e.DisplayName), address, null);
+                }
+            }
+
+            public static void EndpointsNotFound(ILogger logger, object address)
+            {
+                _endpointsNotFound(logger, address, null);
+            }
+
+            public static void PathParsingSucceeded(ILogger logger, PathString path, IEnumerable<Endpoint> endpoints)
+            {
+                // Checking level again to avoid allocation on the common path
+                if (logger.IsEnabled(LogLevel.Debug))
+                {
+                    _pathParsingSucceeded(logger, endpoints.Select(e => e.DisplayName), path.Value, null);
+                }
+            }
+
+            public static void PathParsingFailed(ILogger logger, PathString path, IEnumerable<Endpoint> endpoints)
+            {
+                // Checking level again to avoid allocation on the common path
+                if (logger.IsEnabled(LogLevel.Debug))
+                {
+                    _pathParsingFailed(logger, endpoints.Select(e => e.DisplayName), path.Value, null);
+                }
+            }
+        }
+    }
+}

src/Http/Routing/src/LinkParser.cs

@@ -0,0 +1,37 @@
+// 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 Microsoft.AspNetCore.Http;
+
+namespace Microsoft.AspNetCore.Routing
+{
+    /// <summary>
+    /// Defines a contract to parse URIs using information from routing.
+    /// </summary>
+    public abstract class LinkParser
+    {
+        /// <summary>
+        /// Attempts to parse the provided <paramref name="path"/> using the route pattern
+        /// specified by the <see cref="Endpoint"/> matching <paramref name="address"/>.
+        /// </summary>
+        /// <typeparam name="TAddress">The address type.</typeparam>
+        /// <param name="address">The address value. Used to resolve endpoints.</param>
+        /// <param name="path">The URI path to parse.</param>
+        /// <returns>
+        /// A <see cref="RouteValueDictionary"/> with the parsed values if parsing is successful; 
+        /// otherwise <c>null</c>.
+        /// </returns>
+        /// <remarks>
+        /// <para>
+        /// <see cref="ParsePathByAddress{TAddress}(TAddress, PathString)"/> will attempt to first resolve
+        /// <see cref="Endpoint"/> instances that match <paramref name="address"/> and then use the route
+        /// pattern associated with each endpoint to parse the URL path. 
+        /// </para>
+        /// <para>
+        /// The parsing operation will fail and return <c>null</c> if either no endpoints are found or none
+        /// of the route patterns match the provided URI path.
+        /// </para>
+        /// </remarks>
+        public abstract RouteValueDictionary ParsePathByAddress<TAddress>(TAddress address, PathString path);
+    }
+}

src/Http/Routing/src/LinkParserEndpointNameAddressExtensions.cs

@@ -0,0 +1,54 @@
+// 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.Http;
+
+namespace Microsoft.AspNetCore.Routing
+{
+    /// <summary>
+    /// Extension methods for using <see cref="LinkParser"/> with an endpoint name.
+    /// </summary>
+    public static class LinkParserEndpointNameAddressExtensions
+    {
+        /// <summary>
+        /// Attempts to parse the provided <paramref name="path"/> using the route pattern
+        /// specified by the <see cref="Endpoint"/> matching <paramref name="endpointName"/>.
+        /// </summary>
+        /// <param name="parser">The <see cref="LinkGenerator"/>.</param>
+        /// <param name="endpointName">The endpoint name. Used to resolve endpoints.</param>
+        /// <param name="path">The URI path to parse.</param>
+        /// <returns>
+        /// A <see cref="RouteValueDictionary"/> with the parsed values if parsing is successful; 
+        /// otherwise <c>null</c>.
+        /// </returns>
+        /// <remarks>
+        /// <para>
+        /// <see cref="ParsePathByEndpointName(LinkParser, string, PathString)"/> will attempt to first resolve
+        /// <see cref="Endpoint"/> instances that match <paramref name="endpointName"/> and then use the route
+        /// pattern associated with each endpoint to parse the URL path. 
+        /// </para>
+        /// <para>
+        /// The parsing operation will fail and return <c>null</c> if either no endpoints are found or none
+        /// of the route patterns match the provided URI path.
+        /// </para>
+        /// </remarks>
+        public static RouteValueDictionary ParsePathByEndpointName(
+            this LinkParser parser,
+            string endpointName,
+            PathString path)
+        {
+            if (parser == null)
+            {
+                throw new ArgumentNullException(nameof(parser));
+            }
+
+            if (endpointName == null)
+            {
+                throw new ArgumentNullException(nameof(endpointName));
+            }
+
+            return parser.ParsePathByAddress<string>(endpointName, path);
+        }
+    }
+}