using System.Net;
using System.Net.Http.Json;
using System.Text.Json;
using FluentAssertions;
using Microsoft.EntityFrameworkCore;
using Microsoft.Extensions.DependencyInjection;
using Microsoft.Extensions.Logging;
using StackExchange.Redis;

[Collection("Integration")]
public class ConcurrencyTests : IAsyncLifetime
{
    private readonly ApiFixture _fixture;
    private readonly HttpClient _http;

    public ConcurrencyTests(ApiFixture fixture)
    {
        _fixture = fixture;
        _http = fixture.CreateClient();
        _http.ClearAuth();
        _http.AsAdmin();
    }

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

        var redis = scope.ServiceProvider.GetRequiredService<IConnectionMultiplexer>();
        var server = redis.GetServer(redis.GetEndPoints().First());
        await server.FlushDatabaseAsync(1);
    }

    public Task DisposeAsync() => Task.CompletedTask;

    // -----------------------------------------------------------------------
    //  Parallel patient registration — each must get a unique MRN
    // -----------------------------------------------------------------------

    [Fact]
    public async Task ParallelPatientRegistration_AllGetUniqueMrns()
    {
        const int parallelCount = 10;

        var tasks = Enumerable.Range(0, parallelCount).Select(i =>
        {
            var client = _fixture.CreateClient();
            client.ClearAuth();
            client.AsAdmin();
            return client.PostAsJsonAsync(
                "/api/v1/patients",
                new RegisterPatientRequest(
                    $"Parallel{i}", "Patient",
                    new DateOnly(1980, 1, 1).AddDays(i), "Female"));
        });

        var responses = await Task.WhenAll(tasks);

        var patientIds = new List<Guid>();
        foreach (var resp in responses)
        {
            resp.StatusCode.Should().Be(HttpStatusCode.Created);
            var body = await resp.Content.ReadFromJsonAsync<JsonDocument>();
            patientIds.Add(body!.RootElement.GetProperty("data").GetProperty("id").GetGuid());
        }

        patientIds.Should().OnlyHaveUniqueItems("every parallel registration must receive a distinct ID");

        using var scope = _fixture.Services.CreateScope();
        var db = scope.ServiceProvider.GetRequiredService<AppDbContext>();

        var mrns = await db.Patients
            .Where(p => patientIds.Contains(p.Id))
            .Select(p => p.Mrn)
            .ToListAsync();

        mrns.Should().HaveCount(parallelCount);
        mrns.Should().OnlyHaveUniqueItems("every parallel registration must receive a distinct MRN");
    }

    // -----------------------------------------------------------------------
    //  Parallel SOFA_SEPSIS alerts for same encounter — only one bundle
    // -----------------------------------------------------------------------

    [Fact]
    public async Task ParallelSepsisAlerts_SingleBundleCreated()
    {
        var (patientId, encounterId) = await SeedPatientAndEncounterAsync();
        const int parallelCount = 5;

        using var scope = _fixture.Services.CreateScope();
        var db = scope.ServiceProvider.GetRequiredService<AppDbContext>();

        var alertIds = new List<Guid>();
        for (var i = 0; i < parallelCount; i++)
        {
            var alertId = Guid.NewGuid();
            db.ClinicalAlerts.Add(new ClinicalAlert
            {
                Id = alertId,
                EncounterId = encounterId,
                PatientId = patientId,
                AlertType = AlertType.SofaSepsis,
                Severity = AlertSeverity.Critical,
                Details = $"SOFA delta +{i + 2}",
                Status = AlertStatus.Open,
                TriggeredAt = DateTimeOffset.UtcNow
            });
            alertIds.Add(alertId);
        }
        await db.SaveChangesAsync();

        var tasks = alertIds.Select(alertId =>
        {
            return Task.Run(async () =>
            {
                using var innerScope = _fixture.Services.CreateScope();
                var handler = innerScope.ServiceProvider.GetRequiredService<SepsisAlertHandler>();
                await handler.OnSepsisAlertCreatedAsync(
                    encounterId, alertId, AlertType.SofaSepsis, CancellationToken.None);
            });
        });

        await Task.WhenAll(tasks);

        var bundleCount = await db.SepsisBundles
            .AsNoTracking()
            .CountAsync(b => b.EncounterId == encounterId);

        bundleCount.Should().Be(1, "concurrent SOFA_SEPSIS alerts must produce exactly one bundle");

        var orderCount = await db.Orders
            .AsNoTracking()
            .CountAsync(o => o.EncounterId == encounterId);

        orderCount.Should().Be(4, "only one bundle's orders (4) should exist");
    }

    // -----------------------------------------------------------------------
    //  Parallel observation ingest with same idempotency key — single record
    // -----------------------------------------------------------------------

    [Fact]
    public async Task ParallelObservationIngest_SameIdempotencyKey_SingleRecord()
    {
        var (_, encounterId) = await SeedPatientAndEncounterAsync();
        await SeedThresholdsAsync();

        const int parallelCount = 5;
        var idempotencyKey = $"device-parallel-{Guid.NewGuid():N}";

        var tasks = Enumerable.Range(0, parallelCount).Select(_ =>
        {
            var client = _fixture.CreateClient();
            client.ClearAuth();
            client.AsAdmin();
            return client.PostAsJsonAsync(
                $"/api/v1/encounters/{encounterId}/observations",
                new BatchIngestRequest(new List<IngestObservationRequest>
                {
                    new("HEART_RATE", 78, "bpm", ObservationSource.Device,
                        DateTimeOffset.UtcNow, idempotencyKey)
                }));
        });

        var responses = await Task.WhenAll(tasks);

        foreach (var resp in responses)
            resp.StatusCode.Should().Be(HttpStatusCode.Created);

        using var scope = _fixture.Services.CreateScope();
        var db = scope.ServiceProvider.GetRequiredService<AppDbContext>();

        var obsCount = await db.Observations
            .CountAsync(o => o.EncounterId == encounterId);

        obsCount.Should().Be(1, "parallel ingests with the same idempotency key must produce exactly one record");
    }

    // -----------------------------------------------------------------------
    //  Parallel observation ingest without idempotency key — all succeed
    // -----------------------------------------------------------------------

    [Fact]
    public async Task ParallelObservationIngest_NoIdempotencyKey_AllCreateRecords()
    {
        var (_, encounterId) = await SeedPatientAndEncounterAsync();
        await SeedThresholdsAsync();

        const int parallelCount = 5;

        var tasks = Enumerable.Range(0, parallelCount).Select(i =>
        {
            var client = _fixture.CreateClient();
            client.ClearAuth();
            client.AsAdmin();
            return client.PostAsJsonAsync(
                $"/api/v1/encounters/{encounterId}/observations",
                new BatchIngestRequest(new List<IngestObservationRequest>
                {
                    new("HEART_RATE", 70 + i, "bpm", ObservationSource.Device,
                        DateTimeOffset.UtcNow, null)
                }));
        });

        var responses = await Task.WhenAll(tasks);

        foreach (var resp in responses)
            resp.StatusCode.Should().Be(HttpStatusCode.Created);

        using var scope = _fixture.Services.CreateScope();
        var db = scope.ServiceProvider.GetRequiredService<AppDbContext>();

        var obsCount = await db.Observations
            .CountAsync(o => o.EncounterId == encounterId);

        obsCount.Should().Be(parallelCount,
            "each observation without an idempotency key is distinct and must be stored");
    }

    // -----------------------------------------------------------------------
    //  Parallel encounter open — duplicate active encounter rejected
    // -----------------------------------------------------------------------

    [Fact]
    public async Task ParallelEncounterOpen_SameType_OnlyOneSucceeds()
    {
        var patientId = await CreatePatientViaApiAsync();
        const int parallelCount = 5;

        var tasks = Enumerable.Range(0, parallelCount).Select(_ =>
        {
            var client = _fixture.CreateClient();
            client.ClearAuth();
            client.AsAdmin();
            return client.PostAsJsonAsync(
                $"/api/v1/patients/{patientId}/encounters",
                new OpenEncounterRequest(EncounterType.Inpatient, Department.Icu, "Dr. Race"));
        });

        var responses = await Task.WhenAll(tasks);

        var created = responses.Count(r => r.StatusCode == HttpStatusCode.Created);
        var conflicts = responses.Count(r => r.StatusCode == HttpStatusCode.Conflict);

        created.Should().BeGreaterThanOrEqualTo(1, "at least one encounter must be created");
        (created + conflicts).Should().Be(parallelCount,
            "all responses must be either Created or Conflict");

        using var scope = _fixture.Services.CreateScope();
        var db = scope.ServiceProvider.GetRequiredService<AppDbContext>();

        var activeCount = await db.Encounters
            .CountAsync(e => e.PatientId == patientId
                          && e.EncounterType == EncounterType.Inpatient
                          && e.Status == EncounterStatus.Active);

        activeCount.Should().Be(1,
            "only one active encounter of the same type should exist per patient");
    }

    // -----------------------------------------------------------------------
    //  Helpers
    // -----------------------------------------------------------------------

    private async Task<(Guid PatientId, Guid EncounterId)> SeedPatientAndEncounterAsync()
    {
        using var scope = _fixture.Services.CreateScope();
        var db = scope.ServiceProvider.GetRequiredService<AppDbContext>();

        var patient = new Patient
        {
            Id = Guid.NewGuid(),
            Mrn = $"MRN-CONC-{Guid.NewGuid():N}"[..20],
            FirstName = "Concurrent",
            LastName = "Test",
            DateOfBirth = new DateOnly(1975, 6, 15),
            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. Concurrent",
            AdmittedAt = DateTimeOffset.UtcNow,
            CreatedAt = DateTimeOffset.UtcNow
        };

        db.Patients.Add(patient);
        db.Encounters.Add(encounter);
        await db.SaveChangesAsync();

        return (patient.Id, encounter.Id);
    }

    private async Task SeedThresholdsAsync()
    {
        using var scope = _fixture.Services.CreateScope();
        var db = scope.ServiceProvider.GetRequiredService<AppDbContext>();

        if (!await db.AlertThresholds.AnyAsync(t => t.ObservationCode == "HEART_RATE"))
        {
            db.AlertThresholds.Add(new AlertThreshold
            {
                Id = Guid.NewGuid(),
                ObservationCode = "HEART_RATE",
                DisplayName = "Heart Rate",
                Unit = "bpm",
                CriticalLow = 30,
                WarningLow = 50,
                WarningHigh = 100,
                CriticalHigh = 150,
                CreatedAt = DateTimeOffset.UtcNow
            });
            await db.SaveChangesAsync();
        }

        var redis = scope.ServiceProvider.GetRequiredService<IConnectionMultiplexer>();
        await redis.GetDatabase(1).StringSetAsync(
            "threshold:HEART_RATE",
            """{"ObservationCode":"HEART_RATE","CriticalLow":30,"WarningLow":50,"WarningHigh":100,"CriticalHigh":150}""");
    }

    private async Task<Guid> CreatePatientViaApiAsync()
    {
        var resp = await _http.PostAsJsonAsync(
            "/api/v1/patients",
            new RegisterPatientRequest("Race", "Condition",
                new DateOnly(1985, 3, 20), "Male"));
        resp.EnsureSuccessStatusCode();

        var body = await resp.Content.ReadFromJsonAsync<JsonDocument>();
        return body!.RootElement.GetProperty("data").GetProperty("id").GetGuid();
    }
}