// 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.Generic;
using System.Linq;
using System.Threading.Tasks;
using Microsoft.AspNetCore.Http;
using Microsoft.AspNetCore.Routing.Constraints;
using Microsoft.AspNetCore.Routing.EndpointFinders;
using Microsoft.AspNetCore.Routing.Internal;
using Microsoft.AspNetCore.Routing.Matchers;
using Microsoft.AspNetCore.Routing.TestObjects;
using Microsoft.Extensions.Logging.Abstractions;
using Microsoft.Extensions.ObjectPool;
using Microsoft.Extensions.Options;
using Moq;
using Xunit;

namespace Microsoft.AspNetCore.Routing
{
    public class DefaultLinkGeneratorTest
    {
        [Fact]
        public void GetLink_Success()
        {
            // Arrange
            var endpoint = CreateEndpoint("{controller}");
            var linkGenerator = CreateLinkGenerator();
            var context = CreateRouteValuesContext(new { controller = "Home" });

            // Act
            var link = linkGenerator.GetLink(
                httpContext: null,
                new[] { endpoint },
                context.ExplicitValues,
                context.AmbientValues);

            // Assert
            Assert.Equal("/Home", link);
        }

        [Fact]
        public void GetLink_Fail_ThrowsException()
        {
            // Arrange
            var expectedMessage = "Could not find a matching endpoint to generate a link.";
            var endpoint = CreateEndpoint("{controller}/{action}");
            var linkGenerator = CreateLinkGenerator();
            var context = CreateRouteValuesContext(new { controller = "Home" });

            // Act & Assert
            var exception = Assert.Throws<InvalidOperationException>(
                () => linkGenerator.GetLink(
                    httpContext: null,
                    new[] { endpoint },
                    context.ExplicitValues,
                    context.AmbientValues));
            Assert.Equal(expectedMessage, exception.Message);
        }

        [Fact]
        public void TryGetLink_Fail()
        {
            // Arrange
            var endpoint = CreateEndpoint("{controller}/{action}");
            var linkGenerator = CreateLinkGenerator();
            var context = CreateRouteValuesContext(new { controller = "Home" });

            // Act
            var canGenerateLink = linkGenerator.TryGetLink(
                httpContext: null,
                new[] { endpoint },
                context.ExplicitValues,
                context.AmbientValues,
                out var link);

            // Assert
            Assert.False(canGenerateLink);
            Assert.Null(link);
        }

        [Fact]
        public void GetLink_MultipleEndpoints_Success()
        {
            // Arrange
            var endpoint1 = CreateEndpoint("{controller}/{action}/{id?}");
            var endpoint2 = CreateEndpoint("{controller}/{action}");
            var endpoint3 = CreateEndpoint("{controller}");
            var linkGenerator = CreateLinkGenerator();
            var context = CreateRouteValuesContext(new { controller = "Home", action = "Index", id = "10" });

            // Act
            var link = linkGenerator.GetLink(
                httpContext: null,
                new[] { endpoint1, endpoint2, endpoint3 },
                context.ExplicitValues,
                context.AmbientValues);

            // Assert
            Assert.Equal("/Home/Index/10", link);
        }

        [Fact]
        public void GetLink_MultipleEndpoints_Success2()
        {
            // Arrange
            var endpoint1 = CreateEndpoint("{controller}/{action}/{id}");
            var endpoint2 = CreateEndpoint("{controller}/{action}");
            var endpoint3 = CreateEndpoint("{controller}");
            var linkGenerator = CreateLinkGenerator();
            var context = CreateRouteValuesContext(new { controller = "Home", action = "Index" });

            // Act
            var link = linkGenerator.GetLink(
                httpContext: null,
                new[] { endpoint1, endpoint2, endpoint3 },
                context.ExplicitValues,
                context.AmbientValues);

            // Assert
            Assert.Equal("/Home/Index", link);
        }

        [Fact]
        public void GetLink_EncodesValues()
        {
            // Arrange
            var endpoint = CreateEndpoint("{controller}/{action}");
            var linkGenerator = CreateLinkGenerator();
            var context = CreateRouteValuesContext(
                suppliedValues: new { name = "name with %special #characters" },
                ambientValues: new { controller = "Home", action = "Index" });

            // Act
            var link = linkGenerator.GetLink(
                httpContext: null,
                new[] { endpoint },
                context.ExplicitValues,
                context.AmbientValues);

            // Assert
            Assert.Equal("/Home/Index?name=name%20with%20%25special%20%23characters", link);
        }

        [Fact]
        public void GetLink_ForListOfStrings()
        {
            // Arrange
            var endpoint = CreateEndpoint("{controller}/{action}");
            var linkGenerator = CreateLinkGenerator();
            var context = CreateRouteValuesContext(
                new { color = new List<string> { "red", "green", "blue" } },
                new { controller = "Home", action = "Index" });

            // Act
            var link = linkGenerator.GetLink(
                httpContext: null,
                new[] { endpoint },
                context.ExplicitValues,
                context.AmbientValues);

            // Assert
            Assert.Equal("/Home/Index?color=red&color=green&color=blue", link);
        }

        [Fact]
        public void GetLink_ForListOfInts()
        {
            // Arrange
            var endpoint = CreateEndpoint("{controller}/{action}");
            var linkGenerator = CreateLinkGenerator();
            var context = CreateRouteValuesContext(
                new { items = new List<int> { 10, 20, 30 } },
                new { controller = "Home", action = "Index" });

            // Act
            var link = linkGenerator.GetLink(
                httpContext: null,
                new[] { endpoint },
                context.ExplicitValues,
                context.AmbientValues);

            // Assert
            Assert.Equal("/Home/Index?items=10&items=20&items=30", link);
        }

        [Fact]
        public void GetLink_ForList_Empty()
        {
            // Arrange
            var endpoint = CreateEndpoint("{controller}/{action}");
            var linkGenerator = CreateLinkGenerator();
            var context = CreateRouteValuesContext(
                new { color = new List<string> { } },
                new { controller = "Home", action = "Index" });

            // Act
            var link = linkGenerator.GetLink(
                httpContext: null,
                new[] { endpoint },
                context.ExplicitValues,
                context.AmbientValues);

            // Assert
            Assert.Equal("/Home/Index", link);
        }

        [Fact]
        public void GetLink_ForList_StringWorkaround()
        {
            // Arrange
            var endpoint = CreateEndpoint("{controller}/{action}");
            var linkGenerator = CreateLinkGenerator();
            var context = CreateRouteValuesContext(
                new { page = 1, color = new List<string> { "red", "green", "blue" }, message = "textfortest" },
                new { controller = "Home", action = "Index" });

            // Act
            var link = linkGenerator.GetLink(
                httpContext: null,
                new[] { endpoint },
                context.ExplicitValues,
                context.AmbientValues);

            // Assert
            Assert.Equal("/Home/Index?page=1&color=red&color=green&color=blue&message=textfortest", link);
        }

        [Fact]
        public void GetLink_Success_AmbientValues()
        {
            // Arrange
            var endpoint = CreateEndpoint("{controller}/{action}");
            var linkGenerator = CreateLinkGenerator();
            var context = CreateRouteValuesContext(
                suppliedValues: new { action = "Index" },
                ambientValues: new { controller = "Home" });

            // Act
            var link = linkGenerator.GetLink(
                httpContext: null,
                new[] { endpoint },
                context.ExplicitValues,
                context.AmbientValues);

            // Assert
            Assert.Equal("/Home/Index", link);
        }

        [Fact]
        public void RouteGenerationRejectsConstraints()
        {
            // Arrange
            var context = CreateRouteValuesContext(new { p1 = "abcd" });
            var linkGenerator = CreateLinkGenerator();
            var matchProcessorReferences = new List<MatchProcessorReference>();
            matchProcessorReferences.Add(new MatchProcessorReference("p2", new RegexRouteConstraint("\\d{4}")));
            var endpoint = CreateEndpoint(
                "{p1}/{p2}",
                new { p2 = "catchall" },
                matchProcessorReferences: matchProcessorReferences);

            // Act
            var canGenerateLink = linkGenerator.TryGetLink(
                new DefaultHttpContext(),
                new[] { endpoint },
                context.ExplicitValues,
                context.AmbientValues,
                out var link);

            // Assert
            Assert.False(canGenerateLink);
        }

        [Fact]
        public void RouteGenerationAcceptsConstraints()
        {
            // Arrange
            var context = CreateRouteValuesContext(new { p1 = "hello", p2 = "1234" });
            var linkGenerator = CreateLinkGenerator();
            var matchProcessorReferences = new List<MatchProcessorReference>();
            matchProcessorReferences.Add(new MatchProcessorReference("p2", new RegexRouteConstraint("\\d{4}")));
            var endpoint = CreateEndpoint(
                "{p1}/{p2}",
                new { p2 = "catchall" },
                matchProcessorReferences);

            // Act
            var canGenerateLink = linkGenerator.TryGetLink(
                new DefaultHttpContext(),
                new[] { endpoint },
                context.ExplicitValues,
                context.AmbientValues,
                out var link);

            // Assert
            Assert.True(canGenerateLink);
            Assert.Equal("/hello/1234", link);
        }

        [Fact]
        public void RouteWithCatchAllRejectsConstraints()
        {
            // Arrange
            var context = CreateRouteValuesContext(new { p1 = "abcd" });
            var linkGenerator = CreateLinkGenerator();
            var matchProcessorReferences = new List<MatchProcessorReference>();
            matchProcessorReferences.Add(new MatchProcessorReference("p2", new RegexRouteConstraint("\\d{4}")));
            var endpoint = CreateEndpoint(
                "{p1}/{*p2}",
                new { p2 = "catchall" },
                matchProcessorReferences: matchProcessorReferences);

            // Act
            var canGenerateLink = linkGenerator.TryGetLink(
                new DefaultHttpContext(),
                new[] { endpoint },
                context.ExplicitValues,
                context.AmbientValues,
                out var link);

            // Assert
            Assert.False(canGenerateLink);
        }

        [Fact]
        public void RouteWithCatchAllAcceptsConstraints()
        {
            // Arrange
            var context = CreateRouteValuesContext(new { p1 = "hello", p2 = "1234" });
            var linkGenerator = CreateLinkGenerator();
            var matchProcessorReferences = new List<MatchProcessorReference>();
            matchProcessorReferences.Add(new MatchProcessorReference("p2", new RegexRouteConstraint("\\d{4}")));
            var endpoint = CreateEndpoint(
                "{p1}/{*p2}",
                new { p2 = "catchall" },
                matchProcessorReferences);

            // Act
            var canGenerateLink = linkGenerator.TryGetLink(
                new DefaultHttpContext(),
                new[] { endpoint },
                context.ExplicitValues,
                context.AmbientValues,
                out var link);

            // Assert
            Assert.True(canGenerateLink);
            Assert.Equal("/hello/1234", link);
        }

        [Fact]
        public void GetLinkWithNonParameterConstraintReturnsUrlWithoutQueryString()
        {
            // Arrange
            var context = CreateRouteValuesContext(new { p1 = "hello", p2 = "1234" });
            var linkGenerator = CreateLinkGenerator();
            var target = new Mock<IRouteConstraint>();
            target
                .Setup(
                    e => e.Match(
                        It.IsAny<HttpContext>(),
                        It.IsAny<IRouter>(),
                        It.IsAny<string>(),
                        It.IsAny<RouteValueDictionary>(),
                        It.IsAny<RouteDirection>()))
                .Returns(true)
                .Verifiable();

            var endpoint = CreateEndpoint(
                "{p1}/{p2}",
                defaultValues: new { p2 = "catchall" },
                matchProcessorReferences: new List<MatchProcessorReference>
                {
                    new MatchProcessorReference("p2", target.Object)
                });

            // Act
            var canGenerateLink = linkGenerator.TryGetLink(
                new DefaultHttpContext(),
                new[] { endpoint },
                context.ExplicitValues,
                context.AmbientValues,
                out var link);

            // Assert
            Assert.True(canGenerateLink);
            Assert.Equal("/hello/1234", link);
            target.VerifyAll();
        }

        // Any ambient values from the current request should be visible to constraint, even
        // if they have nothing to do with the route generating a link
        [Fact]
        public void GetLink_ConstraintsSeeAmbientValues()
        {
            // Arrange
            var constraint = new CapturingConstraint();
            var linkGenerator = CreateLinkGenerator();
            var endpoint = CreateEndpoint(
                template: "slug/Home/Store",
                defaultValues: new { controller = "Home", action = "Store" },
                matchProcessorReferences: new List<MatchProcessorReference>()
                {
                    new MatchProcessorReference("c", constraint)
                });

            var context = CreateRouteValuesContext(
                suppliedValues: new { action = "Store" },
                ambientValues: new { controller = "Home", action = "Blog", extra = "42" });

            var expectedValues = new RouteValueDictionary(
                new { controller = "Home", action = "Store", extra = "42" });

            // Act
            var canGenerateLink = linkGenerator.TryGetLink(
                new DefaultHttpContext(),
                new[] { endpoint },
                context.ExplicitValues,
                context.AmbientValues,
                out var link);

            // Assert
            Assert.True(canGenerateLink);
            Assert.Equal("/slug/Home/Store", link);
            Assert.Equal(expectedValues.OrderBy(kvp => kvp.Key), constraint.Values.OrderBy(kvp => kvp.Key));
        }

        // Non-parameter default values from the routing generating a link are not in the 'values'
        // collection when constraints are processed.
        [Fact]
        public void GetLink_ConstraintsDontSeeDefaults_WhenTheyArentParameters()
        {
            // Arrange
            var constraint = new CapturingConstraint();
            var linkGenerator = CreateLinkGenerator();
            var endpoint = CreateEndpoint(
                template: "slug/Home/Store",
                defaultValues: new { controller = "Home", action = "Store", otherthing = "17" },
                matchProcessorReferences: new List<MatchProcessorReference>()
                {
                    new MatchProcessorReference("c", constraint)
                });

            var context = CreateRouteValuesContext(
                suppliedValues: new { action = "Store" },
                ambientValues: new { controller = "Home", action = "Blog" });

            var expectedValues = new RouteValueDictionary(
                new { controller = "Home", action = "Store" });

            // Act
            var link = linkGenerator.GetLink(
                new DefaultHttpContext(),
                new[] { endpoint },
                context.ExplicitValues,
                context.AmbientValues);

            // Assert
            Assert.Equal("/slug/Home/Store", link);
            Assert.Equal(expectedValues.OrderBy(kvp => kvp.Key), constraint.Values.OrderBy(kvp => kvp.Key));
        }

        // Default values are visible to the constraint when they are used to fill a parameter.
        [Fact]
        public void GetLink_ConstraintsSeesDefault_WhenThereItsAParamter()
        {
            // Arrange
            var constraint = new CapturingConstraint();
            var linkGenerator = CreateLinkGenerator();
            var endpoint = CreateEndpoint(
                template: "slug/{controller}/{action}",
                defaultValues: new { action = "Index" },
                matchProcessorReferences: new List<MatchProcessorReference>()
                {
                    new MatchProcessorReference("c", constraint)
                });

            var context = CreateRouteValuesContext(
                suppliedValues: new { controller = "Shopping" },
                ambientValues: new { controller = "Home", action = "Blog" });

            var expectedValues = new RouteValueDictionary(
                new { controller = "Shopping", action = "Index" });

            // Act
            var link = linkGenerator.GetLink(
                new DefaultHttpContext(),
                new[] { endpoint },
                context.ExplicitValues,
                context.AmbientValues);

            // Assert
            Assert.Equal("/slug/Shopping", link);
            Assert.Equal(expectedValues, constraint.Values);
        }

        // Default values from the routing generating a link are in the 'values' collection when
        // constraints are processed - IFF they are specified as values or ambient values.
        [Fact]
        public void GetLink_ConstraintsSeeDefaults_IfTheyAreSpecifiedOrAmbient()
        {
            // Arrange
            var constraint = new CapturingConstraint();
            var linkGenerator = CreateLinkGenerator();
            var endpoint = CreateEndpoint(
                template: "slug/Home/Store",
                defaultValues: new { controller = "Home", action = "Store", otherthing = "17", thirdthing = "13" },
                matchProcessorReferences: new List<MatchProcessorReference>()
                {
                    new MatchProcessorReference("c", constraint)
                });

            var context = CreateRouteValuesContext(
                suppliedValues: new { action = "Store", thirdthing = "13" },
                ambientValues: new { controller = "Home", action = "Blog", otherthing = "17" });

            var expectedValues = new RouteValueDictionary(
                new { controller = "Home", action = "Store", otherthing = "17", thirdthing = "13" });

            // Act
            var link = linkGenerator.GetLink(
                new DefaultHttpContext(),
                new[] { endpoint },
                context.ExplicitValues,
                context.AmbientValues);

            // Assert
            Assert.Equal("/slug/Home/Store", link);
            Assert.Equal(expectedValues.OrderBy(kvp => kvp.Key), constraint.Values.OrderBy(kvp => kvp.Key));
        }

        [Fact]
        public void GetLink_InlineConstraints_Success()
        {
            // Arrange
            var linkGenerator = CreateLinkGenerator();
            var endpoint = CreateEndpoint(
                template: "Home/Index/{id}",
                defaultValues: new { controller = "Home", action = "Index" },
                matchProcessorReferences: new List<MatchProcessorReference>()
                {
                    new MatchProcessorReference("id", "int")
                });
            var context = CreateRouteValuesContext(
                suppliedValues: new { action = "Index", controller = "Home", id = 4 });

            // Act
            var link = linkGenerator.GetLink(
                new DefaultHttpContext(),
                new[] { endpoint },
                context.ExplicitValues,
                context.AmbientValues);

            // Assert
            Assert.Equal("/Home/Index/4", link);
        }

        [Fact]
        public void GetLink_InlineConstraints_NonMatchingvalue()
        {
            // Arrange
            var linkGenerator = CreateLinkGenerator();
            var endpoint = CreateEndpoint(
                template: "Home/Index/{id}",
                defaultValues: new { controller = "Home", action = "Index" },
                matchProcessorReferences: new List<MatchProcessorReference>()
                {
                    new MatchProcessorReference("id", "int")
                });
            var context = CreateRouteValuesContext(
                suppliedValues: new { action = "Index", controller = "Home", id = "not-an-integer" });

            // Act
            var canGenerateLink = linkGenerator.TryGetLink(
                new DefaultHttpContext(),
                new[] { endpoint },
                context.ExplicitValues,
                context.AmbientValues,
                out var link);

            // Assert
            Assert.False(canGenerateLink);
        }

        [Fact]
        public void GetLink_InlineConstraints_OptionalParameter_ValuePresent()
        {
            // Arrange
            var linkGenerator = CreateLinkGenerator();
            var endpoint = CreateEndpoint(
                template: "Home/Index/{id}",
                defaultValues: new { controller = "Home", action = "Index" },
                matchProcessorReferences: new List<MatchProcessorReference>()
                {
                    new MatchProcessorReference("id", optional: true, "int")
                });
            var context = CreateRouteValuesContext(
                suppliedValues: new { action = "Index", controller = "Home", id = 98 });

            // Act
            var link = linkGenerator.GetLink(
                new DefaultHttpContext(),
                new[] { endpoint },
                context.ExplicitValues,
                context.AmbientValues);

            // Assert
            Assert.Equal("/Home/Index/98", link);
        }

        [Fact]
        public void GetLink_InlineConstraints_OptionalParameter_ValueNotPresent()
        {
            // Arrange
            var linkGenerator = CreateLinkGenerator();
            var endpoint = CreateEndpoint(
                template: "Home/Index/{id?}",
                defaultValues: new { controller = "Home", action = "Index" },
                matchProcessorReferences: new List<MatchProcessorReference>()
                {
                    new MatchProcessorReference("id", optional: true, "int")
                });
            var context = CreateRouteValuesContext(
                suppliedValues: new { action = "Index", controller = "Home" });

            // Act
            var link = linkGenerator.GetLink(
                new DefaultHttpContext(),
                new[] { endpoint },
                context.ExplicitValues,
                context.AmbientValues);

            // Assert
            Assert.Equal("/Home/Index", link);
        }

        [Fact]
        public void GetLink_InlineConstraints_OptionalParameter_ValuePresent_ConstraintFails()
        {
            // Arrange
            var linkGenerator = CreateLinkGenerator();
            var endpoint = CreateEndpoint(
                template: "Home/Index/{id}",
                defaultValues: new { controller = "Home", action = "Index" },
                matchProcessorReferences: new List<MatchProcessorReference>()
                {
                    new MatchProcessorReference("id", optional: true, "int")
                });
            var context = CreateRouteValuesContext(
                suppliedValues: new { action = "Index", controller = "Home", id = "not-an-integer" });

            // Act
            var canGenerateLink = linkGenerator.TryGetLink(
                new DefaultHttpContext(),
                new[] { endpoint },
                context.ExplicitValues,
                context.AmbientValues,
                out var link);

            // Assert
            Assert.False(canGenerateLink);
        }

        [Fact]
        public void GetLink_InlineConstraints_CompositeInlineConstraint()
        {
            // Arrange
            var linkGenerator = CreateLinkGenerator();
            var endpoint = CreateEndpoint(
                template: "Home/Index/{id}",
                defaultValues: new { controller = "Home", action = "Index" },
                matchProcessorReferences: new List<MatchProcessorReference>()
                {
                    new MatchProcessorReference("id", "int"),
                    new MatchProcessorReference("id", "range(1,20)")
                });
            var context = CreateRouteValuesContext(
                suppliedValues: new { action = "Index", controller = "Home", id = 14 });

            // Act
            var link = linkGenerator.GetLink(
                new DefaultHttpContext(),
                new[] { endpoint },
                context.ExplicitValues,
                context.AmbientValues);

            // Assert
            Assert.Equal("/Home/Index/14", link);
        }

        [Fact]
        public void GetLink_InlineConstraints_CompositeInlineConstraint_Fails()
        {
            // Arrange
            var linkGenerator = CreateLinkGenerator();
            var endpoint = CreateEndpoint(
                template: "Home/Index/{id}",
                defaultValues: new { controller = "Home", action = "Index" },
                matchProcessorReferences: new List<MatchProcessorReference>()
                {
                    new MatchProcessorReference("id", "int"),
                    new MatchProcessorReference("id", "range(1,20)")
                });
            var context = CreateRouteValuesContext(
                suppliedValues: new { action = "Index", controller = "Home", id = 50 });

            // Act
            var canGenerateLink = linkGenerator.TryGetLink(
                new DefaultHttpContext(),
                new[] { endpoint },
                context.ExplicitValues,
                context.AmbientValues,
                out var link);

            // Assert
            Assert.False(canGenerateLink);
        }

        [Fact]
        public void GetLink_InlineConstraints_CompositeConstraint_FromConstructor()
        {
            // Arrange
            var constraint = new MaxLengthRouteConstraint(20);
            var linkGenerator = CreateLinkGenerator();
            var endpoint = CreateEndpoint(
                template: "Home/Index/{name}",
                defaultValues: new { controller = "Home", action = "Index" },
                matchProcessorReferences: new List<MatchProcessorReference>()
                {
                    new MatchProcessorReference("name", constraint)
                });
            var context = CreateRouteValuesContext(
                suppliedValues: new { action = "Index", controller = "Home", name = "products" });

            // Act
            var link = linkGenerator.GetLink(
                new DefaultHttpContext(),
                new[] { endpoint },
                context.ExplicitValues,
                context.AmbientValues);

            // Assert
            Assert.Equal("/Home/Index/products", link);
        }

        [Fact]
        public void GetLink_OptionalParameter_ParameterPresentInValues()
        {
            // Arrange
            var endpoint = CreateEndpoint("{controller}/{action}/{name?}");
            var linkGenerator = CreateLinkGenerator();
            var context = CreateRouteValuesContext(
                suppliedValues: new { action = "Index", controller = "Home", name = "products" });

            // Act
            var link = linkGenerator.GetLink(
                httpContext: null,
                new[] { endpoint },
                context.ExplicitValues,
                context.AmbientValues);

            // Assert
            Assert.Equal("/Home/Index/products", link);
        }

        [Fact]
        public void GetLink_OptionalParameter_ParameterNotPresentInValues()
        {
            // Arrange
            var endpoint = CreateEndpoint("{controller}/{action}/{name?}");
            var linkGenerator = CreateLinkGenerator();
            var context = CreateRouteValuesContext(
                suppliedValues: new { action = "Index", controller = "Home" });

            // Act
            var link = linkGenerator.GetLink(
                httpContext: null,
                new[] { endpoint },
                context.ExplicitValues,
                context.AmbientValues);

            // Assert
            Assert.Equal("/Home/Index", link);
        }

        [Fact]
        public void GetLink_OptionalParameter_ParameterPresentInValuesAndDefaults()
        {
            // Arrange
            var endpoint = CreateEndpoint(
                template: "{controller}/{action}/{name?}",
                defaultValues: new { name = "default-products" });
            var linkGenerator = CreateLinkGenerator();
            var context = CreateRouteValuesContext(
                suppliedValues: new { action = "Index", controller = "Home", name = "products" });

            // Act
            var link = linkGenerator.GetLink(
                httpContext: null,
                new[] { endpoint },
                context.ExplicitValues,
                context.AmbientValues);

            // Assert
            Assert.Equal("/Home/Index/products", link);
        }

        [Fact]
        public void GetLink_OptionalParameter_ParameterNotPresentInValues_PresentInDefaults()
        {
            // Arrange
            var endpoint = CreateEndpoint(
                template: "{controller}/{action}/{name?}",
                defaultValues: new { name = "products" });
            var linkGenerator = CreateLinkGenerator();
            var context = CreateRouteValuesContext(
                suppliedValues: new { action = "Index", controller = "Home" });

            // Act
            var link = linkGenerator.GetLink(
                httpContext: null,
                new[] { endpoint },
                context.ExplicitValues,
                context.AmbientValues);

            // Assert
            Assert.Equal("/Home/Index", link);
        }

        [Fact]
        public void GetLink_ParameterNotPresentInTemplate_PresentInValues()
        {
            // Arrange
            var endpoint = CreateEndpoint("{controller}/{action}/{name}");
            var linkGenerator = CreateLinkGenerator();
            var context = CreateRouteValuesContext(
                suppliedValues: new { action = "Index", controller = "Home", name = "products", format = "json" });

            // Act
            var link = linkGenerator.GetLink(
                httpContext: null,
                new[] { endpoint },
                context.ExplicitValues,
                context.AmbientValues);

            // Assert
            Assert.Equal("/Home/Index/products?format=json", link);
        }

        [Fact]
        public void GetLink_OptionalParameter_FollowedByDotAfterSlash_ParameterPresent()
        {
            // Arrange
            var linkGenerator = CreateLinkGenerator();
            var endpoint = CreateEndpoint(
                template: "{controller}/{action}/.{name?}");

            var context = CreateRouteValuesContext(
                suppliedValues: new { action = "Index", controller = "Home", name = "products" });

            // Act
            var link = linkGenerator.GetLink(
                new DefaultHttpContext(),
                new[] { endpoint },
                context.ExplicitValues,
                context.AmbientValues);

            // Assert
            Assert.Equal("/Home/Index/.products", link);
        }

        [Fact]
        public void GetLink_OptionalParameter_FollowedByDotAfterSlash_ParameterNotPresent()
        {
            // Arrange
            var linkGenerator = CreateLinkGenerator();
            var endpoint = CreateEndpoint("{controller}/{action}/.{name?}");

            var context = CreateRouteValuesContext(
                suppliedValues: new { action = "Index", controller = "Home" });

            // Act
            var link = linkGenerator.GetLink(
                new DefaultHttpContext(),
                new[] { endpoint },
                context.ExplicitValues,
                context.AmbientValues);

            // Assert
            Assert.Equal("/Home/Index/", link);
        }

        [Fact]
        public void GetLink_OptionalParameter_InSimpleSegment()
        {
            // Arrange
            var endpoint = CreateEndpoint("{controller}/{action}/{name?}");
            var linkGenerator = CreateLinkGenerator();
            var context = CreateRouteValuesContext(
                suppliedValues: new { action = "Index", controller = "Home" });

            // Act
            var link = linkGenerator.GetLink(
                httpContext: null,
                new[] { endpoint },
                context.ExplicitValues,
                context.AmbientValues);

            // Assert
            Assert.Equal("/Home/Index", link);
        }

        [Fact]
        public void GetLink_TwoOptionalParameters_OneValueFromAmbientValues()
        {
            // Arrange
            var endpoint = CreateEndpoint("a/{b=15}/{c?}/{d?}");
            var linkGenerator = CreateLinkGenerator();
            var context = CreateRouteValuesContext(
                suppliedValues: new { },
                ambientValues: new { c = "17" });

            // Act
            var link = linkGenerator.GetLink(
                httpContext: null,
                new[] { endpoint },
                context.ExplicitValues,
                context.AmbientValues);

            // Assert
            Assert.Equal("/a/15/17", link);
        }

        [Fact]
        public void GetLink_OptionalParameterAfterDefault_OneValueFromAmbientValues()
        {
            // Arrange
            var endpoint = CreateEndpoint("a/{b=15}/{c?}");
            var linkGenerator = CreateLinkGenerator();
            var context = CreateRouteValuesContext(
               suppliedValues: new { },
               ambientValues: new { c = "17" });

            // Act
            var link = linkGenerator.GetLink(
                httpContext: null,
                new[] { endpoint },
                context.ExplicitValues,
                context.AmbientValues);

            // Assert
            Assert.Equal("/a/15/17", link);
        }

        [Fact]
        public void GetLink_TwoOptionalParametersAfterDefault_LastValueFromAmbientValues()
        {
            // Arrange
            var endpoint = CreateEndpoint("a/{b=15}/{c?}/{d?}", defaultValues: new { });
            var linkGenerator = CreateLinkGenerator();
            var context = CreateRouteValuesContext(
               suppliedValues: new { },
               ambientValues: new { d = "17" });

            // Act
            var link = linkGenerator.GetLink(
                httpContext: null,
                new[] { endpoint },
                context.ExplicitValues,
                context.AmbientValues);

            // Assert
            Assert.Equal("/a", link);
        }

        private RouteValuesBasedEndpointFinderContext CreateRouteValuesContext(object suppliedValues, object ambientValues = null)
        {
            var context = new RouteValuesBasedEndpointFinderContext();
            context.ExplicitValues = new RouteValueDictionary(suppliedValues);
            context.AmbientValues = new RouteValueDictionary(ambientValues);
            return context;
        }

        private MatcherEndpoint CreateEndpoint(
            string template,
            object defaultValues = null,
            object requiredValues = null,
            List<MatchProcessorReference> matchProcessorReferences = null,
            int order = 0,
            EndpointMetadataCollection metadata = null)
        {
            var defaults = defaultValues == null ? new RouteValueDictionary() : new RouteValueDictionary(defaultValues);
            var required = requiredValues == null ? new RouteValueDictionary() : new RouteValueDictionary(requiredValues);
            metadata = metadata ?? EndpointMetadataCollection.Empty;
            matchProcessorReferences = matchProcessorReferences ?? new List<MatchProcessorReference>();

            return new MatcherEndpoint(
                next => (httpContext) => Task.CompletedTask,
                template,
                defaults,
                required,
                matchProcessorReferences,
                order,
                metadata,
                null);
        }

        private LinkGenerator CreateLinkGenerator()
        {
            return new DefaultLinkGenerator(
                new DefaultMatchProcessorFactory(
                    Options.Create(new RouteOptions()),
                    Mock.Of<IServiceProvider>()),
                new DefaultObjectPool<UriBuildingContext>(new UriBuilderContextPooledObjectPolicy()),
                NullLogger<DefaultLinkGenerator>.Instance);
        }
    }
}