// 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.Threading.Tasks;
using Microsoft.AspNetCore.Http;
using Microsoft.AspNetCore.Http.Features;
using Microsoft.Extensions.Caching.Memory;
using Microsoft.Extensions.Logging.Testing;
using Microsoft.Extensions.Primitives;
using Microsoft.Net.Http.Headers;
using Xunit;

namespace Microsoft.AspNetCore.ResponseCaching.Tests
{
    public class ResponseCachingMiddlewareTests
    {
        [Fact]
        public async Task TryServeFromCacheAsync_OnlyIfCached_Serves504()
        {
            var cache = new TestResponseCache();
            var sink = new TestSink();
            var middleware = TestUtils.CreateTestMiddleware(testSink: sink, cache: cache, keyProvider: new TestResponseCachingKeyProvider());
            var context = TestUtils.CreateTestContext();
            context.HttpContext.Request.Headers[HeaderNames.CacheControl] = new CacheControlHeaderValue()
            {
                OnlyIfCached = true
            }.ToString();

            Assert.True(await middleware.TryServeFromCacheAsync(context));
            Assert.Equal(StatusCodes.Status504GatewayTimeout, context.HttpContext.Response.StatusCode);
            TestUtils.AssertLoggedMessages(
                sink.Writes,
                LoggedMessage.GatewayTimeoutServed);
        }

        [Fact]
        public async Task TryServeFromCacheAsync_CachedResponseNotFound_Fails()
        {
            var cache = new TestResponseCache();
            var sink = new TestSink();
            var middleware = TestUtils.CreateTestMiddleware(testSink: sink, cache: cache, keyProvider: new TestResponseCachingKeyProvider("BaseKey"));
            var context = TestUtils.CreateTestContext();

            Assert.False(await middleware.TryServeFromCacheAsync(context));
            Assert.Equal(1, cache.GetCount);
            TestUtils.AssertLoggedMessages(
                sink.Writes,
                LoggedMessage.NoResponseServed);
        }

        [Fact]
        public async Task TryServeFromCacheAsync_CachedResponseFound_Succeeds()
        {
            var cache = new TestResponseCache();
            var sink = new TestSink();
            var middleware = TestUtils.CreateTestMiddleware(testSink: sink, cache: cache, keyProvider: new TestResponseCachingKeyProvider("BaseKey"));
            var context = TestUtils.CreateTestContext();

            await cache.SetAsync(
                "BaseKey",
                new CachedResponse()
                {
                    Headers = new HeaderDictionary(),
                    Body = new SegmentReadStream(new List<byte[]>(0), 0)
                },
                TimeSpan.Zero);

            Assert.True(await middleware.TryServeFromCacheAsync(context));
            Assert.Equal(1, cache.GetCount);
            TestUtils.AssertLoggedMessages(
                sink.Writes,
                LoggedMessage.CachedResponseServed);
        }

        [Fact]
        public async Task TryServeFromCacheAsync_CachedResponseFound_OverwritesExistingHeaders()
        {
            var cache = new TestResponseCache();
            var sink = new TestSink();
            var middleware = TestUtils.CreateTestMiddleware(testSink: sink, cache: cache, keyProvider: new TestResponseCachingKeyProvider("BaseKey"));
            var context = TestUtils.CreateTestContext();

            context.HttpContext.Response.Headers["MyHeader"] = "OldValue";
            await cache.SetAsync(
                "BaseKey",
                new CachedResponse()
                {
                    Headers = new HeaderDictionary()
                    {
                        { "MyHeader", "NewValue" }
                    },
                    Body = new SegmentReadStream(new List<byte[]>(0), 0)
                },
                TimeSpan.Zero);

            Assert.True(await middleware.TryServeFromCacheAsync(context));
            Assert.Equal("NewValue", context.HttpContext.Response.Headers["MyHeader"]);
            Assert.Equal(1, cache.GetCount);
            TestUtils.AssertLoggedMessages(
                sink.Writes,
                LoggedMessage.CachedResponseServed);
        }

        [Fact]
        public async Task TryServeFromCacheAsync_VaryByRuleFound_CachedResponseNotFound_Fails()
        {
            var cache = new TestResponseCache();
            var sink = new TestSink();
            var middleware = TestUtils.CreateTestMiddleware(testSink: sink, cache: cache, keyProvider: new TestResponseCachingKeyProvider("BaseKey", "VaryKey"));
            var context = TestUtils.CreateTestContext();

            await cache.SetAsync(
                "BaseKey",
                new CachedVaryByRules(),
                TimeSpan.Zero);

            Assert.False(await middleware.TryServeFromCacheAsync(context));
            Assert.Equal(2, cache.GetCount);
            TestUtils.AssertLoggedMessages(
                sink.Writes,
                LoggedMessage.NoResponseServed);
        }

        [Fact]
        public async Task TryServeFromCacheAsync_VaryByRuleFound_CachedResponseFound_Succeeds()
        {
            var cache = new TestResponseCache();
            var sink = new TestSink();
            var middleware = TestUtils.CreateTestMiddleware(testSink: sink, cache: cache, keyProvider: new TestResponseCachingKeyProvider("BaseKey", new[] { "VaryKey", "VaryKey2" }));
            var context = TestUtils.CreateTestContext();

            await cache.SetAsync(
                "BaseKey",
                new CachedVaryByRules(),
                TimeSpan.Zero);
            await cache.SetAsync(
                "BaseKeyVaryKey2",
                new CachedResponse()
                {
                    Headers = new HeaderDictionary(),
                    Body = new SegmentReadStream(new List<byte[]>(0), 0)
                },
                TimeSpan.Zero);

            Assert.True(await middleware.TryServeFromCacheAsync(context));
            Assert.Equal(3, cache.GetCount);
            TestUtils.AssertLoggedMessages(
                sink.Writes,
                LoggedMessage.CachedResponseServed);
        }

        [Fact]
        public async Task TryServeFromCacheAsync_CachedResponseFound_Serves304IfPossible()
        {
            var cache = new TestResponseCache();
            var sink = new TestSink();
            var middleware = TestUtils.CreateTestMiddleware(testSink: sink, cache: cache, keyProvider: new TestResponseCachingKeyProvider("BaseKey"));
            var context = TestUtils.CreateTestContext();
            context.HttpContext.Request.Headers[HeaderNames.IfNoneMatch] = "*";

            await cache.SetAsync(
                "BaseKey",
                new CachedResponse()
                {
                    Body = new SegmentReadStream(new List<byte[]>(0), 0)
                },
                TimeSpan.Zero);

            Assert.True(await middleware.TryServeFromCacheAsync(context));
            Assert.Equal(1, cache.GetCount);
            TestUtils.AssertLoggedMessages(
                sink.Writes,
                LoggedMessage.NotModifiedServed);
        }

        [Fact]
        public void ContentIsNotModified_NotConditionalRequest_False()
        {
            var sink = new TestSink();
            var context = TestUtils.CreateTestContext(sink);
            context.CachedResponseHeaders = new HeaderDictionary();

            Assert.False(ResponseCachingMiddleware.ContentIsNotModified(context));
            Assert.Empty(sink.Writes);
        }

        [Fact]
        public void ContentIsNotModified_IfModifiedSince_FallsbackToDateHeader()
        {
            var utcNow = DateTimeOffset.UtcNow;
            var sink = new TestSink();
            var context = TestUtils.CreateTestContext(sink);
            context.CachedResponseHeaders = new HeaderDictionary();

            context.HttpContext.Request.Headers[HeaderNames.IfModifiedSince] = HeaderUtilities.FormatDate(utcNow);

            // Verify modifications in the past succeeds
            context.CachedResponseHeaders[HeaderNames.Date] = HeaderUtilities.FormatDate(utcNow - TimeSpan.FromSeconds(10));
            Assert.True(ResponseCachingMiddleware.ContentIsNotModified(context));
            Assert.Single(sink.Writes);

            // Verify modifications at present succeeds
            context.CachedResponseHeaders[HeaderNames.Date] = HeaderUtilities.FormatDate(utcNow);
            Assert.True(ResponseCachingMiddleware.ContentIsNotModified(context));
            Assert.Equal(2, sink.Writes.Count);

            // Verify modifications in the future fails
            context.CachedResponseHeaders[HeaderNames.Date] = HeaderUtilities.FormatDate(utcNow + TimeSpan.FromSeconds(10));
            Assert.False(ResponseCachingMiddleware.ContentIsNotModified(context));

            // Verify logging
            TestUtils.AssertLoggedMessages(
                sink.Writes,
                LoggedMessage.NotModifiedIfModifiedSinceSatisfied,
                LoggedMessage.NotModifiedIfModifiedSinceSatisfied);
        }

        [Fact]
        public void ContentIsNotModified_IfModifiedSince_LastModifiedOverridesDateHeader()
        {
            var utcNow = DateTimeOffset.UtcNow;
            var sink = new TestSink();
            var context = TestUtils.CreateTestContext(sink);
            context.CachedResponseHeaders = new HeaderDictionary();

            context.HttpContext.Request.Headers[HeaderNames.IfModifiedSince] = HeaderUtilities.FormatDate(utcNow);

            // Verify modifications in the past succeeds
            context.CachedResponseHeaders[HeaderNames.Date] = HeaderUtilities.FormatDate(utcNow + TimeSpan.FromSeconds(10));
            context.CachedResponseHeaders[HeaderNames.LastModified] = HeaderUtilities.FormatDate(utcNow - TimeSpan.FromSeconds(10));
            Assert.True(ResponseCachingMiddleware.ContentIsNotModified(context));
            Assert.Single(sink.Writes);

            // Verify modifications at present
            context.CachedResponseHeaders[HeaderNames.Date] = HeaderUtilities.FormatDate(utcNow + TimeSpan.FromSeconds(10));
            context.CachedResponseHeaders[HeaderNames.LastModified] = HeaderUtilities.FormatDate(utcNow);
            Assert.True(ResponseCachingMiddleware.ContentIsNotModified(context));
            Assert.Equal(2, sink.Writes.Count);

            // Verify modifications in the future fails
            context.CachedResponseHeaders[HeaderNames.Date] = HeaderUtilities.FormatDate(utcNow - TimeSpan.FromSeconds(10));
            context.CachedResponseHeaders[HeaderNames.LastModified] = HeaderUtilities.FormatDate(utcNow + TimeSpan.FromSeconds(10));
            Assert.False(ResponseCachingMiddleware.ContentIsNotModified(context));

            // Verify logging
            TestUtils.AssertLoggedMessages(
                sink.Writes,
                LoggedMessage.NotModifiedIfModifiedSinceSatisfied,
                LoggedMessage.NotModifiedIfModifiedSinceSatisfied);
        }

        [Fact]
        public void ContentIsNotModified_IfNoneMatch_Overrides_IfModifiedSince_ToTrue()
        {
            var utcNow = DateTimeOffset.UtcNow;
            var sink = new TestSink();
            var context = TestUtils.CreateTestContext(sink);
            context.CachedResponseHeaders = new HeaderDictionary();

            // This would fail the IfModifiedSince checks
            context.HttpContext.Request.Headers[HeaderNames.IfModifiedSince] = HeaderUtilities.FormatDate(utcNow);
            context.CachedResponseHeaders[HeaderNames.LastModified] = HeaderUtilities.FormatDate(utcNow + TimeSpan.FromSeconds(10));

            context.HttpContext.Request.Headers[HeaderNames.IfNoneMatch] = EntityTagHeaderValue.Any.ToString();
            Assert.True(ResponseCachingMiddleware.ContentIsNotModified(context));
            TestUtils.AssertLoggedMessages(
                sink.Writes,
                LoggedMessage.NotModifiedIfNoneMatchStar);
        }

        [Fact]
        public void ContentIsNotModified_IfNoneMatch_Overrides_IfModifiedSince_ToFalse()
        {
            var utcNow = DateTimeOffset.UtcNow;
            var sink = new TestSink();
            var context = TestUtils.CreateTestContext(sink);
            context.CachedResponseHeaders = new HeaderDictionary();

            // This would pass the IfModifiedSince checks
            context.HttpContext.Request.Headers[HeaderNames.IfModifiedSince] = HeaderUtilities.FormatDate(utcNow);
            context.CachedResponseHeaders[HeaderNames.LastModified] = HeaderUtilities.FormatDate(utcNow - TimeSpan.FromSeconds(10));

            context.HttpContext.Request.Headers[HeaderNames.IfNoneMatch] = "\"E1\"";
            Assert.False(ResponseCachingMiddleware.ContentIsNotModified(context));
            Assert.Empty(sink.Writes);
        }

        [Fact]
        public void ContentIsNotModified_IfNoneMatch_AnyWithoutETagInResponse_False()
        {
            var sink = new TestSink();
            var context = TestUtils.CreateTestContext(sink);
            context.CachedResponseHeaders = new HeaderDictionary();
            context.HttpContext.Request.Headers[HeaderNames.IfNoneMatch] = "\"E1\"";

            Assert.False(ResponseCachingMiddleware.ContentIsNotModified(context));
            Assert.Empty(sink.Writes);
        }

        public static TheoryData<EntityTagHeaderValue, EntityTagHeaderValue> EquivalentWeakETags
        {
            get
            {
                return new TheoryData<EntityTagHeaderValue, EntityTagHeaderValue>
                {
                    { new EntityTagHeaderValue("\"tag\""), new EntityTagHeaderValue("\"tag\"") },
                    { new EntityTagHeaderValue("\"tag\"", true), new EntityTagHeaderValue("\"tag\"") },
                    { new EntityTagHeaderValue("\"tag\""), new EntityTagHeaderValue("\"tag\"", true) },
                    { new EntityTagHeaderValue("\"tag\"", true), new EntityTagHeaderValue("\"tag\"", true) }
                };
            }
        }

        [Theory]
        [MemberData(nameof(EquivalentWeakETags))]
        public void  ContentIsNotModified_IfNoneMatch_ExplicitWithMatch_True(EntityTagHeaderValue responseETag, EntityTagHeaderValue requestETag)
        {
            var sink = new TestSink();
            var context = TestUtils.CreateTestContext(sink);
            context.CachedResponseHeaders = new HeaderDictionary();
            context.CachedResponseHeaders[HeaderNames.ETag] = responseETag.ToString();
            context.HttpContext.Request.Headers[HeaderNames.IfNoneMatch] = requestETag.ToString();

            Assert.True(ResponseCachingMiddleware.ContentIsNotModified(context));
            TestUtils.AssertLoggedMessages(
                sink.Writes,
                LoggedMessage.NotModifiedIfNoneMatchMatched);
        }

        [Fact]
        public void ContentIsNotModified_IfNoneMatch_ExplicitWithoutMatch_False()
        {
            var sink = new TestSink();
            var context = TestUtils.CreateTestContext(sink);
            context.CachedResponseHeaders = new HeaderDictionary();
            context.CachedResponseHeaders[HeaderNames.ETag] = "\"E2\"";
            context.HttpContext.Request.Headers[HeaderNames.IfNoneMatch] = "\"E1\"";

            Assert.False(ResponseCachingMiddleware.ContentIsNotModified(context));
            Assert.Empty(sink.Writes);
        }

        [Fact]
        public void ContentIsNotModified_IfNoneMatch_MatchesAtLeastOneValue_True()
        {
            var sink = new TestSink();
            var context = TestUtils.CreateTestContext(sink);
            context.CachedResponseHeaders = new HeaderDictionary();
            context.CachedResponseHeaders[HeaderNames.ETag] = "\"E2\"";
            context.HttpContext.Request.Headers[HeaderNames.IfNoneMatch] = new string[] { "\"E0\", \"E1\"", "\"E1\", \"E2\"" };

            Assert.True(ResponseCachingMiddleware.ContentIsNotModified(context));
            TestUtils.AssertLoggedMessages(
                sink.Writes,
                LoggedMessage.NotModifiedIfNoneMatchMatched);
        }

        [Fact]
        public async Task StartResponsegAsync_IfAllowResponseCaptureIsTrue_SetsResponseTime()
        {
            var clock = new TestClock
            {
                UtcNow = DateTimeOffset.UtcNow
            };
            var middleware = TestUtils.CreateTestMiddleware(options: new ResponseCachingOptions
            {
                SystemClock = clock
            });
            var context = TestUtils.CreateTestContext();
            context.ResponseTime = null;

            await middleware.StartResponseAsync(context);

            Assert.Equal(clock.UtcNow, context.ResponseTime);
        }

        [Fact]
        public async Task StartResponseAsync_IfAllowResponseCaptureIsTrue_SetsResponseTimeOnlyOnce()
        {
            var clock = new TestClock
            {
                UtcNow = DateTimeOffset.UtcNow
            };
            var middleware = TestUtils.CreateTestMiddleware(options: new ResponseCachingOptions
            {
                SystemClock = clock
            });
            var context = TestUtils.CreateTestContext();
            var initialTime = clock.UtcNow;
            context.ResponseTime = null;

            await middleware.StartResponseAsync(context);
            Assert.Equal(initialTime, context.ResponseTime);

            clock.UtcNow += TimeSpan.FromSeconds(10);

            await middleware.StartResponseAsync(context);
            Assert.NotEqual(clock.UtcNow, context.ResponseTime);
            Assert.Equal(initialTime, context.ResponseTime);
        }

        [Fact]
        public async Task FinalizeCacheHeadersAsync_UpdateShouldCacheResponse_IfResponseCacheable()
        {
            var sink = new TestSink();
            var middleware = TestUtils.CreateTestMiddleware(testSink: sink, policyProvider: new ResponseCachingPolicyProvider());
            var context = TestUtils.CreateTestContext();

            context.HttpContext.Response.Headers[HeaderNames.CacheControl] = new CacheControlHeaderValue()
            {
                Public = true
            }.ToString();

            Assert.False(context.ShouldCacheResponse);

            await middleware.FinalizeCacheHeadersAsync(context);

            Assert.True(context.ShouldCacheResponse);
            Assert.Empty(sink.Writes);
        }

        [Fact]
        public async Task FinalizeCacheHeadersAsync_DoNotUpdateShouldCacheResponse_IfResponseIsNotCacheable()
        {
            var sink = new TestSink();
            var middleware = TestUtils.CreateTestMiddleware(testSink: sink, policyProvider: new ResponseCachingPolicyProvider());
            var context = TestUtils.CreateTestContext();

            middleware.ShimResponseStream(context);

            await middleware.FinalizeCacheHeadersAsync(context);

            Assert.False(context.ShouldCacheResponse);
            Assert.Empty(sink.Writes);
        }

        [Fact]
        public async Task FinalizeCacheHeadersAsync_DefaultResponseValidity_Is10Seconds()
        {
            var sink = new TestSink();
            var middleware = TestUtils.CreateTestMiddleware(testSink: sink);
            var context = TestUtils.CreateTestContext();

            await middleware.FinalizeCacheHeadersAsync(context);

            Assert.Equal(TimeSpan.FromSeconds(10), context.CachedResponseValidFor);
            Assert.Empty(sink.Writes);
        }

        [Fact]
        public async Task FinalizeCacheHeadersAsync_ResponseValidity_UseExpiryIfAvailable()
        {
            var clock = new TestClock
            {
                UtcNow = DateTimeOffset.MinValue
            };
            var sink = new TestSink();
            var middleware = TestUtils.CreateTestMiddleware(testSink: sink, options: new ResponseCachingOptions
            {
                SystemClock = clock
            });
            var context = TestUtils.CreateTestContext();

            context.ResponseTime = clock.UtcNow;
            context.HttpContext.Response.Headers[HeaderNames.Expires] = HeaderUtilities.FormatDate(clock.UtcNow + TimeSpan.FromSeconds(11));

            await middleware.FinalizeCacheHeadersAsync(context);

            Assert.Equal(TimeSpan.FromSeconds(11), context.CachedResponseValidFor);
            Assert.Empty(sink.Writes);
        }

        [Fact]
        public async Task FinalizeCacheHeadersAsync_ResponseValidity_UseMaxAgeIfAvailable()
        {
            var clock = new TestClock
            {
                UtcNow = DateTimeOffset.UtcNow
            };
            var sink = new TestSink();
            var middleware = TestUtils.CreateTestMiddleware(testSink: sink, options: new ResponseCachingOptions
            {
                SystemClock = clock
            });
            var context = TestUtils.CreateTestContext();

            context.ResponseTime = clock.UtcNow;
            context.HttpContext.Response.Headers[HeaderNames.CacheControl] = new CacheControlHeaderValue()
            {
                MaxAge = TimeSpan.FromSeconds(12)
            }.ToString();

            context.HttpContext.Response.Headers[HeaderNames.Expires] = HeaderUtilities.FormatDate(clock.UtcNow + TimeSpan.FromSeconds(11));

            await middleware.FinalizeCacheHeadersAsync(context);

            Assert.Equal(TimeSpan.FromSeconds(12), context.CachedResponseValidFor);
            Assert.Empty(sink.Writes);
        }

        [Fact]
        public async Task FinalizeCacheHeadersAsync_ResponseValidity_UseSharedMaxAgeIfAvailable()
        {
            var clock = new TestClock
            {
                UtcNow = DateTimeOffset.UtcNow
            };
            var sink = new TestSink();
            var middleware = TestUtils.CreateTestMiddleware(testSink: sink, options: new ResponseCachingOptions
            {
                SystemClock = clock
            });
            var context = TestUtils.CreateTestContext();

            context.ResponseTime = clock.UtcNow;
            context.HttpContext.Response.Headers[HeaderNames.CacheControl] = new CacheControlHeaderValue()
            {
                MaxAge = TimeSpan.FromSeconds(12),
                SharedMaxAge = TimeSpan.FromSeconds(13)
            }.ToString();
            context.HttpContext.Response.Headers[HeaderNames.Expires] = HeaderUtilities.FormatDate(clock.UtcNow + TimeSpan.FromSeconds(11));

            await middleware.FinalizeCacheHeadersAsync(context);

            Assert.Equal(TimeSpan.FromSeconds(13), context.CachedResponseValidFor);
            Assert.Empty(sink.Writes);
        }

        [Fact]
        public async Task FinalizeCacheHeadersAsync_UpdateCachedVaryByRules_IfNotEquivalentToPrevious()
        {
            var cache = new TestResponseCache();
            var sink = new TestSink();
            var middleware = TestUtils.CreateTestMiddleware(testSink: sink, cache: cache);
            var context = TestUtils.CreateTestContext();

            context.HttpContext.Response.Headers[HeaderNames.Vary] = new StringValues(new[] { "headerA", "HEADERB", "HEADERc" });
            context.HttpContext.Features.Set<IResponseCachingFeature>(new ResponseCachingFeature()
            {
                VaryByQueryKeys = new StringValues(new[] { "queryB", "QUERYA" })
            });
            var cachedVaryByRules = new CachedVaryByRules()
            {
                Headers = new StringValues(new[] { "HeaderA", "HeaderB" }),
                QueryKeys = new StringValues(new[] { "QueryA", "QueryB" })
            };
            context.CachedVaryByRules = cachedVaryByRules;

            await middleware.FinalizeCacheHeadersAsync(context);

            Assert.Equal(1, cache.SetCount);
            Assert.NotSame(cachedVaryByRules, context.CachedVaryByRules);
            TestUtils.AssertLoggedMessages(
                sink.Writes,
                LoggedMessage.VaryByRulesUpdated);
        }

        [Fact]
        public async Task FinalizeCacheHeadersAsync_UpdateCachedVaryByRules_IfEquivalentToPrevious()
        {
            var cache = new TestResponseCache();
            var sink = new TestSink();
            var middleware = TestUtils.CreateTestMiddleware(testSink: sink, cache: cache);
            var context = TestUtils.CreateTestContext();

            context.HttpContext.Response.Headers[HeaderNames.Vary] = new StringValues(new[] { "headerA", "HEADERB" });
            context.HttpContext.Features.Set<IResponseCachingFeature>(new ResponseCachingFeature()
            {
                VaryByQueryKeys = new StringValues(new[] { "queryB", "QUERYA" })
            });
            var cachedVaryByRules = new CachedVaryByRules()
            {
                VaryByKeyPrefix = FastGuid.NewGuid().IdString,
                Headers = new StringValues(new[] { "HEADERA", "HEADERB" }),
                QueryKeys = new StringValues(new[] { "QUERYA", "QUERYB" })
            };
            context.CachedVaryByRules = cachedVaryByRules;

            await middleware.FinalizeCacheHeadersAsync(context);

            // An update to the cache is always made but the entry should be the same
            Assert.Equal(1, cache.SetCount);
            Assert.Same(cachedVaryByRules, context.CachedVaryByRules);
            TestUtils.AssertLoggedMessages(
                sink.Writes,
                LoggedMessage.VaryByRulesUpdated);
        }

        public static TheoryData<StringValues> NullOrEmptyVaryRules
        {
            get
            {
                return new TheoryData<StringValues>
                {
                    default(StringValues),
                    StringValues.Empty,
                    new StringValues((string)null),
                    new StringValues(string.Empty),
                    new StringValues((string[])null),
                    new StringValues(new string[0]),
                    new StringValues(new string[] { null }),
                    new StringValues(new string[] { string.Empty })
                };
            }
        }

        [Theory]
        [MemberData(nameof(NullOrEmptyVaryRules))]
        public async Task FinalizeCacheHeadersAsync_UpdateCachedVaryByRules_NullOrEmptyRules(StringValues vary)
        {
            var cache = new TestResponseCache();
            var sink = new TestSink();
            var middleware = TestUtils.CreateTestMiddleware(testSink: sink, cache: cache);
            var context = TestUtils.CreateTestContext();

            context.HttpContext.Response.Headers[HeaderNames.Vary] = vary;
            context.HttpContext.Features.Set<IResponseCachingFeature>(new ResponseCachingFeature()
            {
                VaryByQueryKeys = vary
            });

            await middleware.FinalizeCacheHeadersAsync(context);

            // Vary rules should not be updated
            Assert.Equal(0, cache.SetCount);
            Assert.Empty(sink.Writes);
        }

        [Fact]
        public async Task FinalizeCacheHeadersAsync_AddsDate_IfNoneSpecified()
        {
            var utcNow = DateTimeOffset.UtcNow;
            var sink = new TestSink();
            var middleware = TestUtils.CreateTestMiddleware(testSink: sink);
            var context = TestUtils.CreateTestContext();
            // ResponseTime is the actual value that's used to set the Date header in FinalizeCacheHeadersAsync
            context.ResponseTime = utcNow;

            Assert.True(StringValues.IsNullOrEmpty(context.HttpContext.Response.Headers[HeaderNames.Date]));

            await middleware.FinalizeCacheHeadersAsync(context);

            Assert.Equal(HeaderUtilities.FormatDate(utcNow), context.HttpContext.Response.Headers[HeaderNames.Date]);
            Assert.Empty(sink.Writes);
        }

        [Fact]
        public async Task FinalizeCacheHeadersAsync_DoNotAddDate_IfSpecified()
        {
            var utcNow = DateTimeOffset.MinValue;
            var sink = new TestSink();
            var middleware = TestUtils.CreateTestMiddleware(testSink: sink);
            var context = TestUtils.CreateTestContext();

            context.HttpContext.Response.Headers[HeaderNames.Date] = HeaderUtilities.FormatDate(utcNow);
            context.ResponseTime = utcNow + TimeSpan.FromSeconds(10);

            Assert.Equal(HeaderUtilities.FormatDate(utcNow), context.HttpContext.Response.Headers[HeaderNames.Date]);

            await middleware.FinalizeCacheHeadersAsync(context);

            Assert.Equal(HeaderUtilities.FormatDate(utcNow), context.HttpContext.Response.Headers[HeaderNames.Date]);
            Assert.Empty(sink.Writes);
        }

        [Fact]
        public async Task FinalizeCacheHeadersAsync_StoresCachedResponse_InState()
        {
            var sink = new TestSink();
            var middleware = TestUtils.CreateTestMiddleware(testSink: sink);
            var context = TestUtils.CreateTestContext();

            Assert.Null(context.CachedResponse);

            await middleware.FinalizeCacheHeadersAsync(context);

            Assert.NotNull(context.CachedResponse);
            Assert.Empty(sink.Writes);
        }

        [Fact]
        public async Task FinalizeCacheHeadersAsync_SplitsVaryHeaderByCommas()
        {
            var sink = new TestSink();
            var middleware = TestUtils.CreateTestMiddleware(testSink: sink);
            var context = TestUtils.CreateTestContext();

            context.HttpContext.Response.Headers[HeaderNames.Vary] = "HeaderB, heaDera";

            await middleware.FinalizeCacheHeadersAsync(context);

            Assert.Equal(new StringValues(new[] { "HEADERA", "HEADERB" }), context.CachedVaryByRules.Headers);
            TestUtils.AssertLoggedMessages(
                sink.Writes,
                LoggedMessage.VaryByRulesUpdated);
        }

        [Fact]
        public async Task FinalizeCacheBody_Cache_IfContentLengthMatches()
        {
            var cache = new TestResponseCache();
            var sink = new TestSink();
            var middleware = TestUtils.CreateTestMiddleware(testSink: sink, cache: cache);
            var context = TestUtils.CreateTestContext();

            context.ShouldCacheResponse = true;
            middleware.ShimResponseStream(context);
            context.HttpContext.Response.ContentLength = 20;

            await context.HttpContext.Response.WriteAsync(new string('0', 20));

            context.CachedResponse = new CachedResponse();
            context.BaseKey = "BaseKey";
            context.CachedResponseValidFor = TimeSpan.FromSeconds(10);

            await middleware.FinalizeCacheBodyAsync(context);

            Assert.Equal(1, cache.SetCount);
            TestUtils.AssertLoggedMessages(
                sink.Writes,
                LoggedMessage.ResponseCached);
        }

        [Fact]
        public async Task FinalizeCacheBody_DoNotCache_IfContentLengthMismatches()
        {
            var cache = new TestResponseCache();
            var sink = new TestSink();
            var middleware = TestUtils.CreateTestMiddleware(testSink: sink, cache: cache);
            var context = TestUtils.CreateTestContext();

            context.ShouldCacheResponse = true;
            middleware.ShimResponseStream(context);
            context.HttpContext.Response.ContentLength = 9;

            await context.HttpContext.Response.WriteAsync(new string('0', 10));

            context.CachedResponse = new CachedResponse();
            context.BaseKey = "BaseKey";
            context.CachedResponseValidFor = TimeSpan.FromSeconds(10);

            await middleware.FinalizeCacheBodyAsync(context);

            Assert.Equal(0, cache.SetCount);
            TestUtils.AssertLoggedMessages(
                sink.Writes,
                LoggedMessage.ResponseContentLengthMismatchNotCached);
        }

        [Fact]
        public async Task FinalizeCacheBody_Cache_IfContentLengthAbsent()
        {
            var cache = new TestResponseCache();
            var sink = new TestSink();
            var middleware = TestUtils.CreateTestMiddleware(testSink: sink, cache: cache);
            var context = TestUtils.CreateTestContext();

            context.ShouldCacheResponse = true;
            middleware.ShimResponseStream(context);

            await context.HttpContext.Response.WriteAsync(new string('0', 10));

            context.CachedResponse = new CachedResponse()
            {
                Headers = new HeaderDictionary()
            };
            context.BaseKey = "BaseKey";
            context.CachedResponseValidFor = TimeSpan.FromSeconds(10);

            await middleware.FinalizeCacheBodyAsync(context);

            Assert.Equal(1, cache.SetCount);
            TestUtils.AssertLoggedMessages(
                sink.Writes,
                LoggedMessage.ResponseCached);
        }

        [Fact]
        public async Task FinalizeCacheBody_DoNotCache_IfShouldCacheResponseFalse()
        {
            var cache = new TestResponseCache();
            var sink = new TestSink();
            var middleware = TestUtils.CreateTestMiddleware(testSink: sink, cache: cache);
            var context = TestUtils.CreateTestContext();

            middleware.ShimResponseStream(context);
            await context.HttpContext.Response.WriteAsync(new string('0', 10));
            context.ShouldCacheResponse = false;

            await middleware.FinalizeCacheBodyAsync(context);

            Assert.Equal(0, cache.SetCount);
            TestUtils.AssertLoggedMessages(
                sink.Writes,
                LoggedMessage.ResponseNotCached);
        }

        [Fact]
        public async Task FinalizeCacheBody_DoNotCache_IfBufferingDisabled()
        {
            var cache = new TestResponseCache();
            var sink = new TestSink();
            var middleware = TestUtils.CreateTestMiddleware(testSink: sink, cache: cache);
            var context = TestUtils.CreateTestContext();

            context.ShouldCacheResponse = true;
            middleware.ShimResponseStream(context);
            await context.HttpContext.Response.WriteAsync(new string('0', 10));

            context.ResponseCachingStream.DisableBuffering();

            await middleware.FinalizeCacheBodyAsync(context);

            Assert.Equal(0, cache.SetCount);
            TestUtils.AssertLoggedMessages(
                sink.Writes,
                LoggedMessage.ResponseNotCached);
        }

        [Fact]
        public async Task FinalizeCacheBody_DoNotCache_IfSizeTooBig()
        {
            var sink = new TestSink();
            var middleware = TestUtils.CreateTestMiddleware(
                testSink: sink,
                keyProvider: new TestResponseCachingKeyProvider("BaseKey"),
                cache: new MemoryResponseCache(new MemoryCache(new MemoryCacheOptions
                {
                    SizeLimit = 100
                })));
            var context = TestUtils.CreateTestContext();

            context.ShouldCacheResponse = true;
            middleware.ShimResponseStream(context);

            await context.HttpContext.Response.WriteAsync(new string('0', 101));

            context.CachedResponse = new CachedResponse() { Headers = new HeaderDictionary() };
            context.CachedResponseValidFor = TimeSpan.FromSeconds(10);

            await middleware.FinalizeCacheBodyAsync(context);

            // The response cached message will be logged but the adding of the entry will no-op
            TestUtils.AssertLoggedMessages(
                sink.Writes,
                LoggedMessage.ResponseCached);

            // The entry cannot be retrieved
            Assert.False(await middleware.TryServeFromCacheAsync(context));
        }

        [Fact]
        public void AddResponseCachingFeature_SecondInvocation_Throws()
        {
            var httpContext = new DefaultHttpContext();

            // Should not throw
            ResponseCachingMiddleware.AddResponseCachingFeature(httpContext);

            // Should throw
            Assert.ThrowsAny<InvalidOperationException>(() => ResponseCachingMiddleware.AddResponseCachingFeature(httpContext));
        }

        private class FakeResponseFeature : HttpResponseFeature
        {
            public override void OnStarting(Func<object, Task> callback, object state) { }
        }

        [Theory]
        // If allowResponseCaching is false, other settings will not matter but are included for completeness
        [InlineData(false, false, false)]
        [InlineData(false, false, true)]
        [InlineData(false, true, false)]
        [InlineData(false, true, true)]
        [InlineData(true, false, false)]
        [InlineData(true, false, true)]
        [InlineData(true, true, false)]
        [InlineData(true, true, true)]
        public async Task Invoke_AddsResponseCachingFeature_Always(bool allowResponseCaching, bool allowCacheLookup, bool allowCacheStorage)
        {
            var responseCachingFeatureAdded = false;
            var middleware = TestUtils.CreateTestMiddleware(next: httpContext =>
            {
                responseCachingFeatureAdded = httpContext.Features.Get<IResponseCachingFeature>() != null;
                return Task.CompletedTask;
            },
            policyProvider: new TestResponseCachingPolicyProvider
            {
                AttemptResponseCachingValue = allowResponseCaching,
                AllowCacheLookupValue = allowCacheLookup,
                AllowCacheStorageValue = allowCacheStorage
            });

            var context = new DefaultHttpContext();
            context.Features.Set<IHttpResponseFeature>(new FakeResponseFeature());
            await middleware.Invoke(context);

            Assert.True(responseCachingFeatureAdded);
        }

        [Fact]
        public void GetOrderCasingNormalizedStringValues_NormalizesCasingToUpper()
        {
            var uppercaseStrings = new StringValues(new[] { "STRINGA", "STRINGB" });
            var lowercaseStrings = new StringValues(new[] { "stringA", "stringB" });

            var normalizedStrings = ResponseCachingMiddleware.GetOrderCasingNormalizedStringValues(lowercaseStrings);

            Assert.Equal(uppercaseStrings, normalizedStrings);
        }

        [Fact]
        public void GetOrderCasingNormalizedStringValues_NormalizesOrder()
        {
            var orderedStrings = new StringValues(new[] { "STRINGA", "STRINGB" });
            var reverseOrderStrings = new StringValues(new[] { "STRINGB", "STRINGA" });

            var normalizedStrings = ResponseCachingMiddleware.GetOrderCasingNormalizedStringValues(reverseOrderStrings);

            Assert.Equal(orderedStrings, normalizedStrings);
        }

        [Fact]
        public void GetOrderCasingNormalizedStringValues_PreservesCommas()
        {
            var originalStrings = new StringValues(new[] { "STRINGA, STRINGB" });

            var normalizedStrings = ResponseCachingMiddleware.GetOrderCasingNormalizedStringValues(originalStrings);

            Assert.Equal(originalStrings, normalizedStrings);
        }
    }
}
