// -----------------------------------------------------------------------------
// ValkeyFailureTests.cs
// Sprint: SPRINT_5100_0005_0001_router_chaos_suite
// Task: T4 - Valkey Failure Injection
// Description: Test router behavior when Valkey cache fails.
// -----------------------------------------------------------------------------

using System.Diagnostics;
using System.Net;
using FluentAssertions;
using StellaOps.Chaos.Router.Tests.Fixtures;

namespace StellaOps.Chaos.Router.Tests;

[Trait("Category", "Chaos")]
[Trait("Category", "Valkey")]
[Collection("ValkeyTests")]
public class ValkeyFailureTests : IClassFixture<RouterWithValkeyFixture>, IAsyncLifetime
{
    private readonly RouterWithValkeyFixture _fixture;

    public ValkeyFailureTests(RouterWithValkeyFixture fixture)
    {
        _fixture = fixture;
    }

    public async Task InitializeAsync()
    {
        await _fixture.StartValkeyAsync();
    }

    public Task DisposeAsync()
    {
        return Task.CompletedTask;
    }

    [Fact]
    public async Task Router_ValkeyDown_FallsBackToLocal()
    {
        // Arrange
        var client = _fixture.CreateClient();

        // Verify normal operation with Valkey
        var response1 = await client.PostAsync("/api/v1/scan", RouterTestFixture.CreateScanRequest());
        var initialSuccess = response1.IsSuccessStatusCode ||
                            response1.StatusCode == HttpStatusCode.TooManyRequests;

        // Kill Valkey
        await _fixture.StopValkeyAsync();

        // Wait for router to detect Valkey is down
        await Task.Delay(2000);

        // Act - Router should degrade gracefully
        var response2 = await client.PostAsync("/api/v1/scan", RouterTestFixture.CreateScanRequest());

        // Assert - Should still work with local rate limiter or return controlled error
        var validStatuses = new[]
        {
            HttpStatusCode.OK,
            HttpStatusCode.Accepted,
            HttpStatusCode.TooManyRequests,
            HttpStatusCode.ServiceUnavailable
        };

        response2.StatusCode.Should().BeOneOf(validStatuses,
            "Router should fall back to local rate limiting when Valkey is down");

        // Restore Valkey for other tests
        await _fixture.StartValkeyAsync();
    }

    [Fact]
    public async Task Router_ValkeyReconnect_ResumesDistributedLimiting()
    {
        // Arrange
        var client = _fixture.CreateClient();

        // Kill and restart Valkey
        await _fixture.StopValkeyAsync();
        await Task.Delay(3000);
        await _fixture.StartValkeyAsync();
        await Task.Delay(2000);  // Allow reconnection

        // Act - Send some requests after Valkey restart
        var responses = new List<HttpResponseMessage>();
        for (var i = 0; i < 10; i++)
        {
            responses.Add(await client.PostAsync("/api/v1/scan", RouterTestFixture.CreateScanRequest()));
            await Task.Delay(100);
        }

        // Assert - Requests should be processed
        var successCount = responses.Count(r =>
            r.IsSuccessStatusCode || r.StatusCode == HttpStatusCode.TooManyRequests);

        successCount.Should().BeGreaterThan(0,
            "Router should resume processing after Valkey reconnect");

        // Optional: Check metrics for distributed limiting active
        var metricsResponse = await client.GetAsync("/metrics");
        if (metricsResponse.IsSuccessStatusCode)
        {
            var metrics = await metricsResponse.Content.ReadAsStringAsync();
            Console.WriteLine("Metrics available after Valkey reconnect");
            // Log whether distributed backend is active
        }
    }

    [Fact]
    public async Task Router_ValkeyLatency_DoesNotBlock()
    {
        // Arrange
        await _fixture.ConfigureValkeyLatencyAsync(TimeSpan.FromSeconds(2));

        var client = _fixture.CreateClient();
        var stopwatch = Stopwatch.StartNew();

        // Act
        var response = await client.PostAsync("/api/v1/scan", RouterTestFixture.CreateScanRequest());

        stopwatch.Stop();

        // Assert - Request should complete without waiting for slow Valkey
        // The router should have a timeout for cache operations
        stopwatch.Elapsed.Should().BeLessThan(TimeSpan.FromSeconds(5),
            "Slow Valkey should not significantly block request processing");

        // Request should still be valid
        var validStatuses = new[]
        {
            HttpStatusCode.OK,
            HttpStatusCode.Accepted,
            HttpStatusCode.TooManyRequests,
            HttpStatusCode.ServiceUnavailable
        };

        response.StatusCode.Should().BeOneOf(validStatuses);

        Console.WriteLine($"Request completed in {stopwatch.ElapsedMilliseconds}ms with slow Valkey");
    }

    [Fact]
    public async Task Router_ValkeyFlap_HandlesGracefully()
    {
        // Arrange
        var client = _fixture.CreateClient();
        var successCount = 0;
        var errorCount = 0;

        // Act - Simulate Valkey flapping
        for (var cycle = 0; cycle < 3; cycle++)
        {
            // Valkey up
            await _fixture.StartValkeyAsync();
            await Task.Delay(1000);

            for (var i = 0; i < 5; i++)
            {
                var response = await client.PostAsync("/api/v1/scan", RouterTestFixture.CreateScanRequest());
                if (response.IsSuccessStatusCode) successCount++;
                else errorCount++;
            }

            // Valkey down
            await _fixture.StopValkeyAsync();
            await Task.Delay(1000);

            for (var i = 0; i < 5; i++)
            {
                var response = await client.PostAsync("/api/v1/scan", RouterTestFixture.CreateScanRequest());
                if (response.IsSuccessStatusCode) successCount++;
                else if (response.StatusCode == HttpStatusCode.TooManyRequests)
                    successCount++; // Throttled is acceptable
                else errorCount++;
            }
        }

        // Assert
        var totalRequests = successCount + errorCount;
        var successRate = (double)successCount / totalRequests;

        Console.WriteLine($"Valkey flap test: {successCount}/{totalRequests} successful ({successRate:P2})");

        successRate.Should().BeGreaterOrEqualTo(0.5,
            "Router should handle at least 50% of requests during Valkey flapping");
    }

    [Fact]
    public async Task Router_ValkeyConnectionExhaustion_DoesNotCrash()
    {
        // Arrange
        var client = _fixture.CreateClient();

        // Create many parallel requests that might exhaust Valkey connections
        var tasks = Enumerable.Range(0, 500)
            .Select(_ => client.PostAsync("/api/v1/scan", RouterTestFixture.CreateScanRequest()));

        // Act
        var responses = await Task.WhenAll(tasks);

        // Assert - Router should not crash
        var validResponses = responses.Count(r =>
            r.StatusCode == HttpStatusCode.OK ||
            r.StatusCode == HttpStatusCode.Accepted ||
            r.StatusCode == HttpStatusCode.TooManyRequests ||
            r.StatusCode == HttpStatusCode.ServiceUnavailable);

        validResponses.Should().Be(responses.Length,
            "All responses should be valid HTTP responses");

        // Verify router is still responsive after burst
        var healthCheck = await client.GetAsync("/health");
        // Router health endpoint should respond
        Console.WriteLine($"Health check after burst: {healthCheck.StatusCode}");
    }
}