using System.Net;
using System.Net.Sockets;
using System.Text.Json;
using FinalFactory.Rendezvous.Server.Diagnostics;
using Microsoft.AspNetCore.Builder;
using Microsoft.AspNetCore.Hosting;
using Microsoft.Extensions.DependencyInjection;
using Microsoft.Extensions.Options;

namespace FinalFactory.Rendezvous.Tests.Diagnostics;

public sealed class DiagnosticDashboardTests
{
    [Fact]
    public void ConfigurationRequiresBoundedUniqueAllowListedScopes()
    {
        Assert.Empty(ValidOptions().Validate());
        Assert.Empty(new DiagnosticDashboardOptions().Validate());

        DiagnosticDashboardOptions invalid = ValidOptions() with
        {
            PollIntervalSeconds = 1,
            MaximumRenderedSessions = 501,
            Scopes =
            [
                new DiagnosticDashboardScope
                {
                    GameId = "INVALID",
                    EnvironmentId = "smoke",
                    ProtocolVersions = [0, 0],
                    Regions = ["INVALID", "INVALID"],
                },
                new DiagnosticDashboardScope
                {
                    GameId = "INVALID",
                    EnvironmentId = "smoke",
                    ProtocolVersions = [1],
                    Regions = ["local"],
                },
            ],
        };

        IReadOnlyList<string> errors = invalid.Validate();
        Assert.Contains(errors, error => error.Contains("PollIntervalSeconds", StringComparison.Ordinal));
        Assert.Contains(errors, error => error.Contains("MaximumRenderedSessions", StringComparison.Ordinal));
        Assert.Contains(errors, error => error.Contains("invalid game", StringComparison.Ordinal));
        Assert.Contains(errors, error => error.Contains("protocol versions", StringComparison.Ordinal));
        Assert.Contains(errors, error => error.Contains("regions", StringComparison.Ordinal));
        Assert.Contains(errors, error => error.Contains("duplicate", StringComparison.Ordinal));

        DiagnosticDashboardOptions nullBound = ValidOptions() with
        {
            Scopes = null!,
        };
        Assert.Contains(
            nullBound.Validate(),
            error => error.Contains("Scopes must contain", StringComparison.Ordinal));
        DiagnosticDashboardOptions nullScope = ValidOptions() with
        {
            Scopes = [null!],
        };
        Assert.Contains(
            nullScope.Validate(),
            error => error.Contains("null entries", StringComparison.Ordinal));
        DiagnosticDashboardOptions nullCollections = ValidOptions() with
        {
            Scopes =
            [
                new DiagnosticDashboardScope
                {
                    GameId = null!,
                    EnvironmentId = null!,
                    ProtocolVersions = null!,
                    Regions = null!,
                },
            ],
        };
        Assert.True(nullCollections.Validate().Count >= 3);
    }

    [Fact]
    public async Task DisabledDashboardHasNoPublicAssetOrConfigurationSurface()
    {
        await using DashboardHost host = await DashboardHost.StartAsync(new());

        Assert.Equal(HttpStatusCode.NotFound, (await host.Client.GetAsync("diagnostics/")).StatusCode);
        Assert.Equal(HttpStatusCode.NotFound, (await host.Client.GetAsync("diagnostics/app.mjs")).StatusCode);
        Assert.Equal(HttpStatusCode.NotFound, (await host.Client.GetAsync("diagnostics/config.json")).StatusCode);
    }

    [Fact]
    public async Task EnabledDashboardServesOnlyHardenedSameOriginReadOnlyAssets()
    {
        await using DashboardHost host = await DashboardHost.StartAsync(ValidOptions());
        using HttpRequestMessage request = new(HttpMethod.Get, "diagnostics/");
        request.Headers.Add("Origin", "https://hostile.example");
        using HttpResponseMessage response = await host.Client.SendAsync(request);
        string html = await response.Content.ReadAsStringAsync();

        Assert.True(response.IsSuccessStatusCode, html);
        Assert.Equal("text/html", response.Content.Headers.ContentType?.MediaType);
        Assert.Equal("DENY", Header(response, "X-Frame-Options"));
        Assert.Equal("nosniff", Header(response, "X-Content-Type-Options"));
        Assert.Equal("no-referrer", Header(response, "Referrer-Policy"));
        Assert.Contains("default-src 'none'", Header(response, "Content-Security-Policy"), StringComparison.Ordinal);
        Assert.Contains("connect-src 'self'", Header(response, "Content-Security-Policy"), StringComparison.Ordinal);
        Assert.Contains("frame-ancestors 'none'", Header(response, "Content-Security-Policy"), StringComparison.Ordinal);
        Assert.False(response.Headers.Contains("Access-Control-Allow-Origin"));
        Assert.Contains("<html lang=\"en\">", html, StringComparison.Ordinal);
        Assert.Contains("href=\"#main-content\"", html, StringComparison.Ordinal);
        Assert.Contains("aria-live=\"polite\"", html, StringComparison.Ordinal);
        Assert.Contains("type=\"module\" src=\"/diagnostics/app.mjs\"", html, StringComparison.Ordinal);
        Assert.DoesNotContain("<script src=\"http", html, StringComparison.OrdinalIgnoreCase);
        Assert.DoesNotContain("/v1/operator", html, StringComparison.OrdinalIgnoreCase);

        using HttpResponseMessage scriptResponse = await host.Client.GetAsync("diagnostics/app.mjs");
        string script = await scriptResponse.Content.ReadAsStringAsync();
        Assert.Equal("text/javascript", scriptResponse.Content.Headers.ContentType?.MediaType);
        Assert.DoesNotContain("/v1/operator", script, StringComparison.OrdinalIgnoreCase);
        Assert.DoesNotContain("Authorization", script, StringComparison.OrdinalIgnoreCase);
        Assert.DoesNotContain("innerHTML", script, StringComparison.Ordinal);
    }

    [Fact]
    public async Task BrowserConfigurationContainsOnlyTheExplicitPublicAllowList()
    {
        await using DashboardHost host = await DashboardHost.StartAsync(ValidOptions());
        using HttpResponseMessage response = await host.Client.GetAsync("diagnostics/config.json");
        using JsonDocument document = JsonDocument.Parse(await response.Content.ReadAsStringAsync());
        JsonElement root = document.RootElement;

        Assert.Equal(HttpStatusCode.OK, response.StatusCode);
        Assert.Equal(1, root.GetProperty("contractVersion").GetInt32());
        Assert.Equal(10, root.GetProperty("pollIntervalSeconds").GetInt32());
        JsonElement scope = Assert.Single(root.GetProperty("scopes").EnumerateArray());
        Assert.Equal("space-game", scope.GetProperty("gameId").GetString());
        Assert.Equal("smoke", scope.GetProperty("environmentId").GetString());
        Assert.Equal("public", scope.GetProperty("visibility").GetString());
        string json = root.GetRawText();
        Assert.DoesNotContain("http", json, StringComparison.OrdinalIgnoreCase);
        Assert.DoesNotContain("credential", json, StringComparison.OrdinalIgnoreCase);
        Assert.DoesNotContain("token", json, StringComparison.OrdinalIgnoreCase);
        Assert.DoesNotContain("endpoint", json, StringComparison.OrdinalIgnoreCase);
    }

    private static string Header(HttpResponseMessage response, string name) =>
        Assert.Single(response.Headers.GetValues(name));

    private static DiagnosticDashboardOptions ValidOptions() => new()
    {
        Enabled = true,
        PollIntervalSeconds = 10,
        MaximumRenderedSessions = 100,
        Scopes =
        [
            new DiagnosticDashboardScope
            {
                GameId = "space-game",
                EnvironmentId = "smoke",
                ProtocolVersions = [1, 2],
                Regions = ["local"],
            },
        ],
    };

    private sealed class DashboardHost : IAsyncDisposable
    {
        private readonly WebApplication _application;

        private DashboardHost(WebApplication application, HttpClient client)
        {
            _application = application;
            Client = client;
        }

        public HttpClient Client { get; }

        public static async Task<DashboardHost> StartAsync(DiagnosticDashboardOptions options)
        {
            int port = ReserveTcpPort();
            string address = $"http://127.0.0.1:{port}";
            WebApplicationBuilder builder = WebApplication.CreateBuilder();
            builder.WebHost.UseUrls(address);
            builder.Services.AddSingleton(Options.Create(options));
            WebApplication application = builder.Build();
            application.MapDiagnosticDashboardEndpoints();
            await application.StartAsync();
            return new(application, new HttpClient { BaseAddress = new Uri(address) });
        }

        public async ValueTask DisposeAsync()
        {
            Client.Dispose();
            await _application.StopAsync();
            await _application.DisposeAsync();
        }

        private static int ReserveTcpPort()
        {
            using TcpListener listener = new(IPAddress.Loopback, 0);
            listener.Start();
            return ((IPEndPoint)listener.LocalEndpoint).Port;
        }
    }
}