using FluentAssertions;
using Microsoft.EntityFrameworkCore;
using Microsoft.Extensions.DependencyInjection;
using StackExchange.Redis;

[Collection("Integration")]
public class SirsDetectorTests : IAsyncLifetime
{
    private readonly ApiFixture _fixture;
    private Guid _encounterId;
    private Guid _patientId;

    public SirsDetectorTests(ApiFixture fixture) => _fixture = fixture;

    public async Task InitializeAsync()
    {
        // Reset PostgreSQL test data
        using var scope = _fixture.Services.CreateScope();
        var db = scope.ServiceProvider.GetRequiredService<AppDbContext>();
        await DbResetHelper.ResetAsync(db);

        var patient = new Patient
        {
            Id = Guid.NewGuid(), Mrn = "MRN-SIRS-001", FirstName = "SIRS", LastName = "Test",
            DateOfBirth = new DateOnly(1960, 1, 1), Gender = "M",
            CreatedAt = DateTimeOffset.UtcNow
        };
        var encounter = new Encounter
        {
            Id = Guid.NewGuid(), PatientId = patient.Id, EncounterType = EncounterType.Inpatient,
            Status = EncounterStatus.Active, Department = Department.Icu,
            AttendingPhysician = "Dr. SIRS", AdmittedAt = DateTimeOffset.UtcNow,
            CreatedAt = DateTimeOffset.UtcNow
        };
        db.Patients.Add(patient);
        db.Encounters.Add(encounter);
        await db.SaveChangesAsync();

        _patientId = patient.Id;
        _encounterId = encounter.Id;

        // Flush all SIRS keys for this encounter from Redis
        var redis = scope.ServiceProvider.GetRequiredService<IConnectionMultiplexer>();
        var cache = redis.GetDatabase();
        foreach (var key in SirsEvaluator.AllCriterionKeys(_encounterId))
            await cache.KeyDeleteAsync(key);
    }

    public Task DisposeAsync() => Task.CompletedTask;

    private SirsDetector CreateDetector()
    {
        using var scope = _fixture.Services.CreateScope();
        return scope.ServiceProvider.GetRequiredService<SirsDetector>();
    }

    // Test 1: one criterion met — insufficient for alert
    [Fact]
    public async Task OneCriterion_NoAlert()
    {
        using var scope = _fixture.Services.CreateScope();
        var detector = scope.ServiceProvider.GetRequiredService<SirsDetector>();

        var result = await detector.ProcessObservationAsync(
            _encounterId, _patientId, "HEART_RATE", 95m);

        result.Outcome.Should().Be(SirsOutcome.InsufficientCriteria);
        result.ActiveCount.Should().Be(1);

        // Verify Redis key was set
        var redis = scope.ServiceProvider.GetRequiredService<IConnectionMultiplexer>();
        var ttl = await redis.GetDatabase()
            .KeyTimeToLiveAsync(SirsEvaluator.CriterionKey(_encounterId, "HEART_RATE"));
        ttl.Should().NotBeNull().And.BeGreaterThan(TimeSpan.Zero);
    }

    // Test 2: two criteria met — SEPSIS_WARNING alert created
    [Fact]
    public async Task TwoCriteriaMet_AlertCreated()
    {
        using var scope = _fixture.Services.CreateScope();
        var detector = scope.ServiceProvider.GetRequiredService<SirsDetector>();
        var db = scope.ServiceProvider.GetRequiredService<AppDbContext>();

        // Tachycardia
        var r1 = await detector.ProcessObservationAsync(
            _encounterId, _patientId, "HEART_RATE", 95m);
        r1.Outcome.Should().Be(SirsOutcome.InsufficientCriteria);

        // Fever — now count = 2 → alert
        var r2 = await detector.ProcessObservationAsync(
            _encounterId, _patientId, "TEMP_C", 38.5m);
        r2.Outcome.Should().Be(SirsOutcome.AlertCreated);

        // Verify clinical_alert row in PostgreSQL
        var alert = await db.ClinicalAlerts.SingleAsync();
        alert.AlertType.Should().Be(AlertType.SepsisWarning);
        alert.Severity.Should().Be(AlertSeverity.Critical);
        alert.Status.Should().Be(AlertStatus.Open);
        alert.EncounterId.Should().Be(_encounterId);
        alert.PatientId.Should().Be(_patientId);

        // Verify outbox event was written in the same transaction
        var outbox = await db.OutboxEvents.SingleAsync();
        outbox.Topic.Should().Be("alert.generated");
        outbox.PartitionKey.Should().Be(_encounterId.ToString());
    }

    // Test 3: third criterion met while alert already open — no second alert
    [Fact]
    public async Task ThreeCriteriaMet_NoSecondAlert()
    {
        using var scope = _fixture.Services.CreateScope();
        var detector = scope.ServiceProvider.GetRequiredService<SirsDetector>();
        var db = scope.ServiceProvider.GetRequiredService<AppDbContext>();

        await detector.ProcessObservationAsync(_encounterId, _patientId, "HEART_RATE", 95m);
        await detector.ProcessObservationAsync(_encounterId, _patientId, "TEMP_C", 38.5m);
        // Third criterion (tachypnea) — alert already open
        var r3 = await detector.ProcessObservationAsync(
            _encounterId, _patientId, "RESP_RATE", 22m);

        r3.Outcome.Should().Be(SirsOutcome.AlertAlreadyOpen);

        // Still exactly one alert — the WHERE NOT EXISTS prevented a duplicate
        var alertCount = await db.ClinicalAlerts.CountAsync();
        alertCount.Should().Be(1, "a second SEPSIS_WARNING must not be created while one is already open");
    }

    // Test 4: criterion clears — Redis key deleted, alert remains open
    //
    // This is the most important test in Phase 5. It verifies:
    // (a) The DEL path works when a criterion is no longer met.
    // (b) Clearing a criterion does not resolve the existing alert — the clinical
    //     workflow requires explicit acknowledgment. A patient whose temperature
    //     normalises may still be septic; the alert is for the clinician to evaluate.
    [Fact]
    public async Task CriterionClears_KeyDeleted_AlertRemainsOpen()
    {
        using var scope = _fixture.Services.CreateScope();
        var detector = scope.ServiceProvider.GetRequiredService<SirsDetector>();
        var db = scope.ServiceProvider.GetRequiredService<AppDbContext>();
        var redis = scope.ServiceProvider.GetRequiredService<IConnectionMultiplexer>();
        var cache = redis.GetDatabase();

        // Establish two criteria and create the alert
        await detector.ProcessObservationAsync(_encounterId, _patientId, "HEART_RATE", 95m);
        await detector.ProcessObservationAsync(_encounterId, _patientId, "TEMP_C", 38.5m);

        // Temperature normalises
        var result = await detector.ProcessObservationAsync(
            _encounterId, _patientId, "TEMP_C", 37.0m);

        // TEMP_C key must be gone from Redis
        var tempKeyExists = await cache.KeyExistsAsync(
            SirsEvaluator.CriterionKey(_encounterId, "TEMP_C"));
        tempKeyExists.Should().BeFalse("a cleared criterion must be deleted from Redis immediately");

        // HEART_RATE key must still exist (criterion still met)
        var hrKeyExists = await cache.KeyExistsAsync(
            SirsEvaluator.CriterionKey(_encounterId, "HEART_RATE"));
        hrKeyExists.Should().BeTrue("an active criterion must remain until its own TTL or a clearing observation");

        // Active count is now 1, but alert must stay open
        result.Outcome.Should().Be(SirsOutcome.InsufficientCriteria);
        result.ActiveCount.Should().Be(1);

        var alert = await db.ClinicalAlerts.SingleAsync();
        alert.Status.Should().Be(AlertStatus.Open,
            "the existing alert is not auto-resolved when criteria drop below 2 — " +
            "clinical acknowledgment is required");
    }

    // Test 5: at-least-once redelivery — idempotency under simulated crash
    [Fact]
    public async Task DuplicateObservationEvent_AlertCreatedOnce()
    {
        using var scope = _fixture.Services.CreateScope();
        var detector = scope.ServiceProvider.GetRequiredService<SirsDetector>();
        var db = scope.ServiceProvider.GetRequiredService<AppDbContext>();

        await detector.ProcessObservationAsync(_encounterId, _patientId, "HEART_RATE", 95m);

        // Simulate: the consumer crashes after this call completes but before committing
        // the Kafka offset. On restart, the same observation is redelivered.
        await detector.ProcessObservationAsync(_encounterId, _patientId, "TEMP_C", 38.5m);
        await detector.ProcessObservationAsync(_encounterId, _patientId, "TEMP_C", 38.5m); // duplicate

        var alertCount = await db.ClinicalAlerts.CountAsync();
        alertCount.Should().Be(1, "WHERE NOT EXISTS prevents duplicate alert on redelivery");

        var outboxCount = await db.OutboxEvents.CountAsync();
        outboxCount.Should().Be(1, "outbox event must be written exactly once");
    }

    // Test 6: non-SIRS code — engine ignores it entirely
    [Fact]
    public async Task NonSirsCode_NoRedisInteraction()
    {
        using var scope = _fixture.Services.CreateScope();
        var detector = scope.ServiceProvider.GetRequiredService<SirsDetector>();
        var redis = scope.ServiceProvider.GetRequiredService<IConnectionMultiplexer>();

        var result = await detector.ProcessObservationAsync(
            _encounterId, _patientId, "POTASSIUM_MEQ_L", 3.2m);

        result.Outcome.Should().Be(SirsOutcome.NotSirsCode);

        // No SIRS keys were created for this encounter
        var anyKey = await redis.GetDatabase()
            .KeyExistsAsync(SirsEvaluator.CriterionKey(_encounterId, "POTASSIUM_MEQ_L"));
        anyKey.Should().BeFalse();
    }
}