using Microsoft.AspNetCore.Authentication;
using Microsoft.AspNetCore.Builder;
using Microsoft.AspNetCore.Hosting;
using Microsoft.AspNetCore.Http;
using Microsoft.AspNetCore.TestHost;
using Microsoft.Extensions.DependencyInjection;
using Microsoft.Extensions.Hosting;
using Microsoft.Extensions.Logging.Abstractions;
using ScadaLink.Commons.Entities.Audit;
using ScadaLink.Commons.Interfaces.Services;
using ScadaLink.Commons.Types.Enums;
using ScadaLink.InboundAPI.Middleware;
using System.Security.Claims;

namespace ScadaLink.InboundAPI.Tests.Middleware;

/// <summary>
/// M4 Bundle D (D2) — verifies the production pipeline order from
/// <c>ScadaLink.Host.Program.cs</c> for the inbound API:
/// <c>UseAuthentication → UseAuthorization → UseAuditWriteMiddleware → endpoint</c>.
///
/// <para>
/// The order is load-bearing: the audit middleware must run AFTER auth (so any
/// framework-resolved principal on <see cref="HttpContext.User"/> is in place)
/// and BEFORE the inbound-API endpoint handler (so the handler's stashed actor
/// name from <see cref="HttpContext.Items"/> is observable in the
/// <c>finally</c> block when the handler returns). The order is also what
/// guarantees auth-failure responses (401/403 produced by a future auth scheme)
/// are seen by the middleware so it can emit
/// <see cref="AuditKind.InboundAuthFailure"/>.
/// </para>
/// </summary>
public class MiddlewareOrderTests
{
    /// <summary>
    /// Captures the order of pipeline stages by appending a token to a shared
    /// list as each stage runs. The assertion compares the resulting sequence
    /// directly so a regression that re-orders the pipeline fails loudly.
    /// </summary>
    private sealed class OrderingRecorder
    {
        public List<string> Stages { get; } = new();
        public void Record(string stage)
        {
            lock (Stages) { Stages.Add(stage); }
        }
    }

    private sealed class RecordingAuditWriter : ICentralAuditWriter
    {
        public List<AuditEvent> Events { get; } = new();
        public Task WriteAsync(AuditEvent evt, CancellationToken ct = default)
        {
            lock (Events) { Events.Add(evt); }
            return Task.CompletedTask;
        }
    }

    [Fact]
    public async Task Middleware_Pipeline_PlacesAuditWriteAfterAuth_BeforeScriptExecution()
    {
        var recorder = new OrderingRecorder();
        var writer = new RecordingAuditWriter();

        using var host = await BuildHostAsync(recorder, writer);
        var client = host.GetTestClient();

        var response = await client.PostAsync("/api/echo", new StringContent("{}"));

        Assert.Equal(System.Net.HttpStatusCode.OK, response.StatusCode);

        // The recorder MUST observe these stages in exactly this order:
        //   1. Authentication (UseAuthentication marker)
        //   2. Authorization  (UseAuthorization marker)
        //   3. AuditMiddleware-Before-Next (audit middleware entered)
        //   4. Endpoint handler (the route handler ran)
        //   5. AuditMiddleware-After-Next (audit middleware completed)
        Assert.Equal(
            new[]
            {
                "auth",
                "authz",
                "audit-before",
                "endpoint",
                "audit-after",
            },
            recorder.Stages);

        // And exactly one InboundRequest/Delivered audit row was emitted —
        // proving the audit middleware actually wrapped the endpoint.
        var evt = Assert.Single(writer.Events);
        Assert.Equal(AuditKind.InboundRequest, evt.Kind);
        Assert.Equal(AuditStatus.Delivered, evt.Status);
        Assert.Equal("test-actor", evt.Actor);
    }

    [Fact]
    public async Task Middleware_Pipeline_Records_AuthFailure_Beyond_Endpoint()
    {
        // A 401 short-circuit happens *inside the endpoint handler* in the real
        // InboundAPI (the X-API-Key validator runs there), so the audit
        // middleware still wraps it and observes the 401 response status. This
        // confirms ordering supports the InboundAuthFailure emission path.
        var recorder = new OrderingRecorder();
        var writer = new RecordingAuditWriter();

        using var host = await BuildHostAsync(recorder, writer, endpointStatus: 401);
        var client = host.GetTestClient();

        var response = await client.PostAsync("/api/echo", new StringContent("{}"));

        Assert.Equal(System.Net.HttpStatusCode.Unauthorized, response.StatusCode);

        var evt = Assert.Single(writer.Events);
        Assert.Equal(AuditKind.InboundAuthFailure, evt.Kind);
        Assert.Equal(AuditStatus.Failed, evt.Status);
        Assert.Equal(401, evt.HttpStatus);
    }

    /// <summary>
    /// Builds a minimal in-memory host whose pipeline mirrors the production
    /// arrangement in <c>ScadaLink.Host.Program.cs</c>:
    /// <c>UseRouting → UseAuthentication → UseAuthorization → UseAuditWriteMiddleware → endpoints</c>.
    /// Marker middlewares record their entry into <paramref name="recorder"/> so
    /// the test can assert on the resulting ordering.
    /// </summary>
    private static async Task<IHost> BuildHostAsync(
        OrderingRecorder recorder,
        ICentralAuditWriter writer,
        int endpointStatus = 200)
    {
        var hostBuilder = new HostBuilder()
            .ConfigureWebHost(webBuilder =>
            {
                webBuilder
                    .UseTestServer()
                    .ConfigureServices(services =>
                    {
                        services.AddSingleton(writer);
                        services.AddSingleton<AuditWriteMiddleware>(sp =>
                            new AuditWriteMiddleware(
                                // The middleware factory pattern is bypassed
                                // here so the inner delegate is closed over the
                                // recorder — UseMiddleware<T> below still
                                // instantiates the type correctly.
                                _ => Task.CompletedTask,
                                writer,
                                NullLogger<AuditWriteMiddleware>.Instance));
                        services.AddRouting();
                        services.AddAuthorization();
                        services.AddAuthentication("TestScheme")
                            .AddScheme<AuthenticationSchemeOptions, AlwaysAuthenticatedHandler>(
                                "TestScheme", _ => { });
                    })
                    .Configure(app =>
                    {
                        app.UseRouting();
                        app.Use(async (ctx, next) =>
                        {
                            recorder.Record("auth");
                            await next();
                        });
                        app.UseAuthentication();
                        app.Use(async (ctx, next) =>
                        {
                            recorder.Record("authz");
                            await next();
                        });
                        app.UseAuthorization();

                        // The order-under-test: AuditWriteMiddleware sits
                        // AFTER auth/authz markers and BEFORE the endpoint
                        // marker. We wrap with a sentinel marker that fires
                        // *before* the audit middleware enters so the test can
                        // pin where the audit middleware lands in the chain.
                        app.Use(async (ctx, next) =>
                        {
                            recorder.Record("audit-before");
                            await next();
                            recorder.Record("audit-after");
                        });
                        app.UseAuditWriteMiddleware();

                        app.UseEndpoints(endpoints =>
                        {
                            endpoints.MapPost("/api/{methodName}", async ctx =>
                            {
                                recorder.Record("endpoint");

                                if (endpointStatus is 401 or 403)
                                {
                                    // Simulate an auth-failure short-circuit
                                    // produced by the in-handler API key
                                    // validator — Actor must stay null.
                                    ctx.Response.StatusCode = endpointStatus;
                                    return;
                                }

                                // Simulate the production handler stashing
                                // the resolved API key name AFTER auth.
                                ctx.Items[AuditWriteMiddleware.AuditActorItemKey] = "test-actor";
                                ctx.Response.StatusCode = endpointStatus;
                                await ctx.Response.WriteAsync("ok");
                            });
                        });
                    });
            });

        var host = await hostBuilder.StartAsync();
        return host;
    }

    /// <summary>
    /// Minimal authentication handler that always succeeds — keeps
    /// <see cref="HttpContext.User"/> populated so the test's audit middleware
    /// path that prefers Items but falls back to User.Identity has a real
    /// principal to ignore. The middleware's primary path uses Items so this
    /// handler's claim never appears on the emitted Actor.
    /// </summary>
    private sealed class AlwaysAuthenticatedHandler : AuthenticationHandler<AuthenticationSchemeOptions>
    {
        public AlwaysAuthenticatedHandler(
            Microsoft.Extensions.Options.IOptionsMonitor<AuthenticationSchemeOptions> options,
            Microsoft.Extensions.Logging.ILoggerFactory logger,
            System.Text.Encodings.Web.UrlEncoder encoder)
            : base(options, logger, encoder) { }

        protected override Task<AuthenticateResult> HandleAuthenticateAsync()
        {
            var identity = new ClaimsIdentity(new[] { new Claim(ClaimTypes.Name, "framework-user") }, "TestScheme");
            var principal = new ClaimsPrincipal(identity);
            var ticket = new AuthenticationTicket(principal, "TestScheme");
            return Task.FromResult(AuthenticateResult.Success(ticket));
        }
    }
}