// 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.Threading.Tasks;
using Microsoft.AspNetCore.Http;
using Microsoft.AspNetCore.Routing.Patterns;
using Xunit;

namespace Microsoft.AspNetCore.Routing.Matchers
{
    public class DefaultEndpointSelectorTest
    {
        [Fact]
        public async Task SelectAsync_NoCandidates_DoesNothing()
        {
            // Arrange
            var endpoints = new MatcherEndpoint[] { };
            var scores = new int[] { };
            var candidateSet = CreateCandidateSet(endpoints, scores);

            var (httpContext, feature) = CreateContext();
            var selector = CreateSelector();

            // Act
            await selector.SelectAsync(httpContext, feature, candidateSet);

            // Assert
            Assert.Null(feature.Endpoint);
        }

        [Fact]
        public async Task SelectAsync_NoValidCandidates_DoesNothing()
        {
            // Arrange
            var endpoints = new MatcherEndpoint[] { CreateEndpoint("/test"), };
            var scores = new int[] { 0, };
            var candidateSet = CreateCandidateSet(endpoints, scores);

            candidateSet[0].Values = new RouteValueDictionary();
            candidateSet[0].IsValidCandidate = false;

            var (httpContext, feature) = CreateContext();
            var selector = CreateSelector();

            // Act
            await selector.SelectAsync(httpContext, feature, candidateSet);

            // Assert
            Assert.Null(feature.Endpoint);
            Assert.Null(feature.Values);
        }

        [Fact]
        public async Task SelectAsync_SingleCandidate_ChoosesCandidate()
        {
            // Arrange
            var endpoints = new MatcherEndpoint[] { CreateEndpoint("/test"), };
            var scores = new int[] { 0, };
            var candidateSet = CreateCandidateSet(endpoints, scores);

            candidateSet[0].Values = new RouteValueDictionary();
            candidateSet[0].IsValidCandidate = true;

            var (httpContext, feature) = CreateContext();
            var selector = CreateSelector();

            // Act
            await selector.SelectAsync(httpContext, feature, candidateSet);

            // Assert
            Assert.Same(endpoints[0], feature.Endpoint);
            Assert.Same(endpoints[0].Invoker, feature.Invoker);
            Assert.NotNull(feature.Values);
        }

        [Fact]
        public async Task SelectAsync_SingleValidCandidate_ChoosesCandidate()
        {
            // Arrange
            var endpoints = new MatcherEndpoint[] { CreateEndpoint("/test1"), CreateEndpoint("/test2"), };
            var scores = new int[] { 0, 0 };
            var candidateSet = CreateCandidateSet(endpoints, scores);
            
            candidateSet[0].IsValidCandidate = false;
            candidateSet[1].IsValidCandidate = true;

            var (httpContext, feature) = CreateContext();
            var selector = CreateSelector();

            // Act
            await selector.SelectAsync(httpContext, feature, candidateSet);

            // Assert
            Assert.Same(endpoints[1], feature.Endpoint);
        }

        [Fact]
        public async Task SelectAsync_SingleValidCandidateInGroup_ChoosesCandidate()
        {
            // Arrange
            var endpoints = new MatcherEndpoint[] { CreateEndpoint("/test1"), CreateEndpoint("/test2"), CreateEndpoint("/test3"), };
            var scores = new int[] { 0, 0, 1 };
            var candidateSet = CreateCandidateSet(endpoints, scores);

            candidateSet[0].IsValidCandidate = false;
            candidateSet[1].IsValidCandidate = true;
            candidateSet[2].IsValidCandidate = true;

            var (httpContext, feature) = CreateContext();
            var selector = CreateSelector();

            // Act
            await selector.SelectAsync(httpContext, feature, candidateSet);

            // Assert
            Assert.Same(endpoints[1], feature.Endpoint);
        }

        [Fact]
        public async Task SelectAsync_ManyGroupsLastCandidate_ChoosesCandidate()
        {
            // Arrange
            var endpoints = new MatcherEndpoint[] 
            {
                CreateEndpoint("/test1"),
                CreateEndpoint("/test2"),
                CreateEndpoint("/test3"),
                CreateEndpoint("/test4"),
                CreateEndpoint("/test5"),
            };
            var scores = new int[] { 0, 1, 2, 3, 4 };
            var candidateSet = CreateCandidateSet(endpoints, scores);

            candidateSet[0].IsValidCandidate = false;
            candidateSet[1].IsValidCandidate = false;
            candidateSet[2].IsValidCandidate = false;
            candidateSet[3].IsValidCandidate = false;
            candidateSet[4].IsValidCandidate = true;

            var (httpContext, feature) = CreateContext();
            var selector = CreateSelector();

            // Act
            await selector.SelectAsync(httpContext, feature, candidateSet);

            // Assert
            Assert.Same(endpoints[4], feature.Endpoint);
        }

        [Fact]
        public async Task SelectAsync_MultipleValidCandidatesInGroup_ReportsAmbiguity()
        {
            // Arrange
            var endpoints = new MatcherEndpoint[] { CreateEndpoint("/test1"), CreateEndpoint("/test2"), CreateEndpoint("/test3"), };
            var scores = new int[] { 0, 1, 1 };
            var candidateSet = CreateCandidateSet(endpoints, scores);

            candidateSet[0].IsValidCandidate = false;
            candidateSet[1].IsValidCandidate = true;
            candidateSet[2].IsValidCandidate = true;

            var (httpContext, feature) = CreateContext();
            var selector = CreateSelector();

            // Act
            var ex = await Assert.ThrowsAsync<AmbiguousMatchException>(() => selector.SelectAsync(httpContext, feature, candidateSet));

            // Assert
            Assert.Equal(
@"The request matched multiple endpoints. Matches: 

test: /test2
test: /test3", ex.Message);
            Assert.Null(feature.Endpoint);
        }

        private static (HttpContext httpContext, IEndpointFeature feature) CreateContext()
        {
            return (new DefaultHttpContext(), new EndpointFeature());
        }

        private static MatcherEndpoint CreateEndpoint(string template)
        {
            return new MatcherEndpoint(
                MatcherEndpoint.EmptyInvoker,
                RoutePatternFactory.Parse(template),
                new RouteValueDictionary(),
                0,
                EndpointMetadataCollection.Empty,
                $"test: {template}");
        }

        private static CandidateSet CreateCandidateSet(MatcherEndpoint[] endpoints, int[] scores)
        {
            return new CandidateSet(endpoints, scores);
        }

        private static DefaultEndpointSelector CreateSelector()
        {
            return new DefaultEndpointSelector();
        }
    }
}