// 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.Globalization;
using System.Net;
using System.Net.Http;
using System.Threading.Tasks;
using Microsoft.AspNetCore.Builder;
using Microsoft.AspNetCore.TestHost;
using Xunit;

namespace Microsoft.AspNetCore.StaticFiles
{
    public class CacheHeaderTests
    {
        [Fact]
        public async Task ServerShouldReturnETag()
        {
            TestServer server = StaticFilesTestServer.Create(app => app.UseFileServer());

            HttpResponseMessage response = await server.CreateClient().GetAsync("http://localhost/SubFolder/extra.xml");
            Assert.NotNull(response.Headers.ETag);
            Assert.NotNull(response.Headers.ETag.Tag);
        }

        [Fact]
        public async Task SameETagShouldBeReturnedAgain()
        {
            TestServer server = StaticFilesTestServer.Create(app => app.UseFileServer());

            HttpResponseMessage response1 = await server.CreateClient().GetAsync("http://localhost/SubFolder/extra.xml");
            HttpResponseMessage response2 = await server.CreateClient().GetAsync("http://localhost/SubFolder/extra.xml");
            Assert.Equal(response2.Headers.ETag, response1.Headers.ETag);
        }

        // 14.24 If-Match
        // If none of the entity tags match, or if "*" is given and no current
        // entity exists, the server MUST NOT perform the requested method, and
        // MUST return a 412 (Precondition Failed) response. This behavior is
        // most useful when the client wants to prevent an updating method, such
        // as PUT, from modifying a resource that has changed since the client
        // last retrieved it.

        [Theory]
        [MemberData(nameof(SupportedMethods))]
        public async Task IfMatchShouldReturn412WhenNotListed(HttpMethod method)
        {
            TestServer server = StaticFilesTestServer.Create(app => app.UseFileServer());
            var req = new HttpRequestMessage(method, "http://localhost/SubFolder/extra.xml");
            req.Headers.Add("If-Match", "\"fake\"");
            HttpResponseMessage resp = await server.CreateClient().SendAsync(req);
            Assert.Equal(HttpStatusCode.PreconditionFailed, resp.StatusCode);
        }

        [Theory]
        [MemberData(nameof(SupportedMethods))]
        public async Task IfMatchShouldBeServedWhenListed(HttpMethod method)
        {
            TestServer server = StaticFilesTestServer.Create(app => app.UseFileServer());
            HttpResponseMessage original = await server.CreateClient().GetAsync("http://localhost/SubFolder/extra.xml");

            var req = new HttpRequestMessage(method, "http://localhost/SubFolder/extra.xml");
            req.Headers.Add("If-Match", original.Headers.ETag.ToString());
            HttpResponseMessage resp = await server.CreateClient().SendAsync(req);
            Assert.Equal(HttpStatusCode.OK, resp.StatusCode);
        }

        [Theory]
        [MemberData(nameof(SupportedMethods))]
        public async Task IfMatchShouldBeServedForAstrisk(HttpMethod method)
        {
            TestServer server = StaticFilesTestServer.Create(app => app.UseFileServer());
            var req = new HttpRequestMessage(method, "http://localhost/SubFolder/extra.xml");
            req.Headers.Add("If-Match", "*");
            HttpResponseMessage resp = await server.CreateClient().SendAsync(req);
            Assert.Equal(HttpStatusCode.OK, resp.StatusCode);
        }

        [Theory]
        [MemberData(nameof(UnsupportedMethods))]
        public async Task IfMatchShouldBeIgnoredForUnsupportedMethods(HttpMethod method)
        {
            TestServer server = StaticFilesTestServer.Create(app => app.UseFileServer());
            var req = new HttpRequestMessage(method, "http://localhost/SubFolder/extra.xml");
            req.Headers.Add("If-Match", "*");
            HttpResponseMessage resp = await server.CreateClient().SendAsync(req);
            Assert.Equal(HttpStatusCode.NotFound, resp.StatusCode);
        }

        // 14.26 If-None-Match
        // If any of the entity tags match the entity tag of the entity that
        // would have been returned in the response to a similar GET request
        // (without the If-None-Match header) on that resource, or if "*" is
        // given and any current entity exists for that resource, then the
        // server MUST NOT perform the requested method, unless required to do
        // so because the resource's modification date fails to match that
        // supplied in an If-Modified-Since header field in the request.
        // Instead, if the request method was GET or HEAD, the server SHOULD
        // respond with a 304 (Not Modified) response, including the cache-
        // related header fields (particularly ETag) of one of the entities that
        // matched. For all other request methods, the server MUST respond with
        // a status of 412 (Precondition Failed).

        [Theory]
        [MemberData(nameof(SupportedMethods))]
        public async Task IfNoneMatchShouldReturn304ForMatching(HttpMethod method)
        {
            TestServer server = StaticFilesTestServer.Create(app => app.UseFileServer());
            HttpResponseMessage resp1 = await server.CreateClient().GetAsync("http://localhost/SubFolder/extra.xml");

            var req2 = new HttpRequestMessage(method, "http://localhost/SubFolder/extra.xml");
            req2.Headers.Add("If-None-Match", resp1.Headers.ETag.ToString());
            HttpResponseMessage resp2 = await server.CreateClient().SendAsync(req2);
            Assert.Equal(HttpStatusCode.NotModified, resp2.StatusCode);
        }

        [Theory]
        [MemberData(nameof(SupportedMethods))]
        public async Task IfNoneMatchAllShouldReturn304ForMatching(HttpMethod method)
        {
            TestServer server = StaticFilesTestServer.Create(app => app.UseFileServer());
            HttpResponseMessage resp1 = await server.CreateClient().GetAsync("http://localhost/SubFolder/extra.xml");

            var req2 = new HttpRequestMessage(method, "http://localhost/SubFolder/extra.xml");
            req2.Headers.Add("If-None-Match", "*");
            HttpResponseMessage resp2 = await server.CreateClient().SendAsync(req2);
            Assert.Equal(HttpStatusCode.NotModified, resp2.StatusCode);
        }

        [Theory]
        [MemberData(nameof(UnsupportedMethods))]
        public async Task IfNoneMatchShouldBeIgnoredForNonTwoHundredAnd304Responses(HttpMethod method)
        {
            TestServer server = StaticFilesTestServer.Create(app => app.UseFileServer());
            HttpResponseMessage resp1 = await server.CreateClient().GetAsync("http://localhost/SubFolder/extra.xml");

            var req2 = new HttpRequestMessage(method, "http://localhost/SubFolder/extra.xml");
            req2.Headers.Add("If-None-Match", resp1.Headers.ETag.ToString());
            HttpResponseMessage resp2 = await server.CreateClient().SendAsync(req2);
            Assert.Equal(HttpStatusCode.NotFound, resp2.StatusCode);
        }

        // 14.26 If-None-Match
        // If none of the entity tags match, then the server MAY perform the
        // requested method as if the If-None-Match header field did not exist,
        // but MUST also ignore any If-Modified-Since header field(s) in the
        // request. That is, if no entity tags match, then the server MUST NOT
        // return a 304 (Not Modified) response.

        // A server MUST use the strong comparison function (see section 13.3.3)
        // to compare the entity tags in If-Match.

        [Theory]
        [MemberData(nameof(SupportedMethods))]
        public async Task ServerShouldReturnLastModified(HttpMethod method)
        {
            TestServer server = StaticFilesTestServer.Create(app => app.UseFileServer());

            HttpResponseMessage response = await server.CreateClient().SendAsync(
                new HttpRequestMessage(method, "http://localhost/SubFolder/extra.xml"));

            Assert.NotNull(response.Content.Headers.LastModified);
            // Verify that DateTimeOffset is UTC
            Assert.Equal(response.Content.Headers.LastModified.Value.Offset, TimeSpan.Zero);
        }

        // 13.3.4
        // An HTTP/1.1 origin server, upon receiving a conditional request that
        // includes both a Last-Modified date (e.g., in an If-Modified-Since or
        // If-Unmodified-Since header field) and one or more entity tags (e.g.,
        // in an If-Match, If-None-Match, or If-Range header field) as cache
        // validators, MUST NOT return a response status of 304 (Not Modified)
        // unless doing so is consistent with all of the conditional header
        // fields in the request.

        [Theory]
        [MemberData(nameof(SupportedMethods))]
        public async Task MatchingBothConditionsReturnsNotModified(HttpMethod method)
        {
            TestServer server = StaticFilesTestServer.Create(app => app.UseFileServer());
            HttpResponseMessage resp1 = await server
                .CreateRequest("/SubFolder/extra.xml")
                .SendAsync(method.Method);

            HttpResponseMessage resp2 = await server
                .CreateRequest("/SubFolder/extra.xml")
                .AddHeader("If-None-Match", resp1.Headers.ETag.ToString())
                .And(req => req.Headers.IfModifiedSince = resp1.Content.Headers.LastModified)
                .SendAsync(method.Method);

            Assert.Equal(HttpStatusCode.NotModified, resp2.StatusCode);
        }


        [Theory]
        [MemberData(nameof(SupportedMethods))]
        public async Task MatchingAtLeastOneETagReturnsNotModified(HttpMethod method)
        {
            TestServer server = StaticFilesTestServer.Create(app => app.UseFileServer());
            HttpResponseMessage resp1 = await server
                .CreateRequest("/SubFolder/extra.xml")
                .SendAsync(method.Method);
            var etag = resp1.Headers.ETag.ToString();

            HttpResponseMessage resp2 = await server
                .CreateRequest("/SubFolder/extra.xml")
                .AddHeader("If-Match", etag + ", " + etag)
                .SendAsync(method.Method);

            Assert.Equal(HttpStatusCode.OK, resp2.StatusCode);

            HttpResponseMessage resp3 = await server
                .CreateRequest("/SubFolder/extra.xml")
                .AddHeader("If-Match", etag+ ", \"badetag\"")
                .SendAsync(method.Method);

            Assert.Equal(HttpStatusCode.OK, resp3.StatusCode);
        }

        [Theory]
        [MemberData(nameof(SupportedMethods))]
        public async Task MissingEitherOrBothConditionsReturnsNormally(HttpMethod method)
        {
            TestServer server = StaticFilesTestServer.Create(app => app.UseFileServer());
            HttpResponseMessage resp1 = await server
                .CreateRequest("/SubFolder/extra.xml")
                .SendAsync(method.Method);

            DateTimeOffset lastModified = resp1.Content.Headers.LastModified.Value;
            DateTimeOffset pastDate = lastModified.AddHours(-1);
            DateTimeOffset furtureDate = lastModified.AddHours(1);

            HttpResponseMessage resp2 = await server
                .CreateRequest("/SubFolder/extra.xml")
                .AddHeader("If-None-Match", "\"fake\"")
                .And(req => req.Headers.IfModifiedSince = lastModified)
                .SendAsync(method.Method);

            HttpResponseMessage resp3 = await server
                .CreateRequest("/SubFolder/extra.xml")
                .AddHeader("If-None-Match", resp1.Headers.ETag.ToString())
                .And(req => req.Headers.IfModifiedSince = pastDate)
                .SendAsync(method.Method);

            HttpResponseMessage resp4 = await server
                .CreateRequest("/SubFolder/extra.xml")
                .AddHeader("If-None-Match", "\"fake\"")
                .And(req => req.Headers.IfModifiedSince = furtureDate)
                .SendAsync(method.Method);

            Assert.Equal(HttpStatusCode.OK, resp2.StatusCode);
            Assert.Equal(HttpStatusCode.OK, resp3.StatusCode);
            Assert.Equal(HttpStatusCode.OK, resp4.StatusCode);
        }

        // 14.25 If-Modified-Since
        // The If-Modified-Since request-header field is used with a method to
        // make it conditional: if the requested variant has not been modified
        // since the time specified in this field, an entity will not be
        // returned from the server; instead, a 304 (not modified) response will
        // be returned without any message-body.

        // a) If the request would normally result in anything other than a
        //   200 (OK) status, or if the passed If-Modified-Since date is
        //   invalid, the response is exactly the same as for a normal GET.
        //   A date which is later than the server's current time is
        //   invalid.
        [Theory]
        [MemberData(nameof(SupportedMethods))]
        public async Task InvalidIfModifiedSinceDateFormatGivesNormalGet(HttpMethod method)
        {
            TestServer server = StaticFilesTestServer.Create(app => app.UseFileServer());

            HttpResponseMessage res = await server
                .CreateRequest("/SubFolder/extra.xml")
                .AddHeader("If-Modified-Since", "bad-date")
                .SendAsync(method.Method);

            Assert.Equal(HttpStatusCode.OK, res.StatusCode);
        }

        [Theory]
        [MemberData(nameof(SupportedMethods))]
        public async Task FutureIfModifiedSinceDateFormatGivesNormalGet(HttpMethod method)
        {
            TestServer server = StaticFilesTestServer.Create(app => app.UseFileServer());

            HttpResponseMessage res = await server
                .CreateRequest("/SubFolder/extra.xml")
                .And(req => req.Headers.IfModifiedSince = DateTimeOffset.Now.AddYears(1))
                .SendAsync(method.Method);

            Assert.Equal(HttpStatusCode.OK, res.StatusCode);
        }

        // b) If the variant has been modified since the If-Modified-Since
        //   date, the response is exactly the same as for a normal GET.

        // c) If the variant has not been modified since a valid If-
        //   Modified-Since date, the server SHOULD return a 304 (Not
        //   Modified) response.

        [Theory]
        [MemberData(nameof(SupportedMethods))]
        public async Task IfModifiedSinceDateGreaterThanLastModifiedShouldReturn304(HttpMethod method)
        {
            TestServer server = StaticFilesTestServer.Create(app => app.UseFileServer());

            HttpResponseMessage res1 = await server
                .CreateRequest("/SubFolder/extra.xml")
                .SendAsync(method.Method);

            HttpResponseMessage res2 = await server
                .CreateRequest("/SubFolder/extra.xml")
                .And(req => req.Headers.IfModifiedSince = DateTimeOffset.Now)
                .SendAsync(method.Method);

            Assert.Equal(HttpStatusCode.NotModified, res2.StatusCode);
        }

        [Theory]
        [MemberData(nameof(SupportedMethods))]
        public async Task SuppportsIfModifiedDateFormats(HttpMethod method)
        {
            TestServer server = StaticFilesTestServer.Create(app => app.UseFileServer());
            HttpResponseMessage res1 = await server
                .CreateRequest("/SubFolder/extra.xml")
                .SendAsync(method.Method);

            var formats = new[]
            {
                "ddd, dd MMM yyyy HH:mm:ss 'GMT'",
                "dddd, dd-MMM-yy HH:mm:ss 'GMT'",
                "ddd MMM  d HH:mm:ss yyyy"
            };

            foreach (var format in formats)
            {
                HttpResponseMessage res2 = await server
                    .CreateRequest("/SubFolder/extra.xml")
                    .AddHeader("If-Modified-Since", DateTimeOffset.UtcNow.ToString(format))
                    .SendAsync(method.Method);

                Assert.Equal(HttpStatusCode.NotModified, res2.StatusCode);
            }
        }

        [Theory]
        [MemberData(nameof(SupportedMethods))]
        public async Task IfModifiedSinceDateLessThanLastModifiedShouldReturn200(HttpMethod method)
        {
            TestServer server = StaticFilesTestServer.Create(app => app.UseFileServer());

            HttpResponseMessage res1 = await server
                .CreateRequest("/SubFolder/extra.xml")
                .SendAsync(method.Method);

            HttpResponseMessage res2 = await server
                .CreateRequest("/SubFolder/extra.xml")
                .And(req => req.Headers.IfModifiedSince = DateTimeOffset.MinValue)
                .SendAsync(method.Method);

            Assert.Equal(HttpStatusCode.OK, res2.StatusCode);
        }

        [Theory]
        [MemberData(nameof(SupportedMethods))]
        public async Task InvalidIfUnmodifiedSinceDateFormatGivesNormalGet(HttpMethod method)
        {
            TestServer server = StaticFilesTestServer.Create(app => app.UseFileServer());

            HttpResponseMessage res = await server
                .CreateRequest("/SubFolder/extra.xml")
                .AddHeader("If-Unmodified-Since", "bad-date")
                .SendAsync(method.Method);

            Assert.Equal(HttpStatusCode.OK, res.StatusCode);
        }

        [Theory]
        [MemberData(nameof(SupportedMethods))]
        public async Task FutureIfUnmodifiedSinceDateFormatGivesNormalGet(HttpMethod method)
        {
            TestServer server = StaticFilesTestServer.Create(app => app.UseFileServer());

            HttpResponseMessage res = await server
                .CreateRequest("/SubFolder/extra.xml")
                .And(req => req.Headers.IfUnmodifiedSince = DateTimeOffset.Now.AddYears(1))
                .SendAsync(method.Method);

            Assert.Equal(HttpStatusCode.OK, res.StatusCode);
        }

        [Theory]
        [MemberData(nameof(SupportedMethods))]
        public async Task IfUnmodifiedSinceDateLessThanLastModifiedShouldReturn412(HttpMethod method)
        {
            TestServer server = StaticFilesTestServer.Create(app => app.UseFileServer());

            HttpResponseMessage res1 = await server
                .CreateRequest("/SubFolder/extra.xml")
                .SendAsync(method.Method);

            HttpResponseMessage res2 = await server
                .CreateRequest("/SubFolder/extra.xml")
                .And(req => req.Headers.IfUnmodifiedSince = DateTimeOffset.MinValue)
                .SendAsync(method.Method);

            Assert.Equal(HttpStatusCode.PreconditionFailed, res2.StatusCode);
        }


        public static IEnumerable<object> SupportedMethods => new[]
        {
            new [] { HttpMethod.Get },
            new [] { HttpMethod.Head }
        };

        public static IEnumerable<object> UnsupportedMethods => new[]
        {
            new [] { HttpMethod.Post },
            new [] { HttpMethod.Put },
            new [] { HttpMethod.Options },
            new [] { HttpMethod.Trace },
            new [] { new HttpMethod("VERB") }
        };
    }
}