using Microsoft.AspNetCore.Mvc;
using StellaOps.JobEngine.Infrastructure.Postgres;
using static StellaOps.Localization.T;

namespace StellaOps.JobEngine.WebService.Endpoints;

/// <summary>
/// Health and readiness probe endpoints.
/// </summary>
public static class HealthEndpoints
{
    /// <summary>
    /// Maps health endpoints to the route builder.
    /// </summary>
    public static IEndpointRouteBuilder MapHealthEndpoints(this IEndpointRouteBuilder app)
    {
        app.MapGet("/healthz", GetHealth)
            .WithName("Orchestrator_Health")
            .WithTags("Health")
            .WithDescription(_t("orchestrator.health.liveness_description"))
            .AllowAnonymous();

        app.MapGet("/readyz", GetReadiness)
            .WithName("Orchestrator_Readiness")
            .WithTags("Health")
            .WithDescription(_t("orchestrator.health.readiness_description"))
            .AllowAnonymous();

        app.MapGet("/livez", GetLiveness)
            .WithName("Orchestrator_Liveness")
            .WithTags("Health")
            .WithDescription(_t("orchestrator.health.liveness_description"))
            .AllowAnonymous();

        app.MapGet("/health/details", GetHealthDetails)
            .WithName("Orchestrator_HealthDetails")
            .WithTags("Health")
            .WithDescription(_t("orchestrator.health.deep_description"))
            .AllowAnonymous();

        return app;
    }

    private static IResult GetHealth([FromServices] TimeProvider timeProvider)
    {
        return Results.Ok(new HealthResponse("ok", timeProvider.GetUtcNow()));
    }

    private static async Task<IResult> GetReadiness(
        [FromServices] JobEngineDataSource dataSource,
        [FromServices] TimeProvider timeProvider,
        CancellationToken cancellationToken)
    {
        try
        {
            // Check database connectivity
            var dbHealthy = await CheckDatabaseAsync(dataSource, cancellationToken).ConfigureAwait(false);

            if (!dbHealthy)
            {
                return Results.Json(
                    new ReadinessResponse("not_ready", timeProvider.GetUtcNow(), new Dictionary<string, string>
                    {
                        ["database"] = "unhealthy"
                    }),
                    statusCode: StatusCodes.Status503ServiceUnavailable);
            }

            return Results.Ok(new ReadinessResponse("ready", timeProvider.GetUtcNow(), new Dictionary<string, string>
            {
                ["database"] = "healthy"
            }));
        }
        catch (Exception ex)
        {
            return Results.Json(
                new ReadinessResponse("not_ready", timeProvider.GetUtcNow(), new Dictionary<string, string>
                {
                    ["database"] = $"error: {ex.Message}"
                }),
                statusCode: StatusCodes.Status503ServiceUnavailable);
        }
    }

    private static IResult GetLiveness([FromServices] TimeProvider timeProvider)
    {
        // Liveness just checks the process is alive
        return Results.Ok(new HealthResponse("alive", timeProvider.GetUtcNow()));
    }

    private static async Task<IResult> GetHealthDetails(
        [FromServices] JobEngineDataSource dataSource,
        [FromServices] TimeProvider timeProvider,
        CancellationToken cancellationToken)
    {
        var checks = new Dictionary<string, HealthCheckResult>();
        var overallHealthy = true;

        // Database check
        try
        {
            var dbHealthy = await CheckDatabaseAsync(dataSource, cancellationToken).ConfigureAwait(false);
            checks["database"] = new HealthCheckResult(
                dbHealthy ? "healthy" : "unhealthy",
                dbHealthy ? null : "Connection test failed",
                timeProvider.GetUtcNow());
            overallHealthy &= dbHealthy;
        }
        catch (Exception ex)
        {
            checks["database"] = new HealthCheckResult("unhealthy", ex.Message, timeProvider.GetUtcNow());
            overallHealthy = false;
        }

        // Memory check
        var memoryInfo = GC.GetGCMemoryInfo();
        var memoryUsedMb = GC.GetTotalMemory(false) / (1024.0 * 1024.0);
        var memoryLimitMb = memoryInfo.TotalAvailableMemoryBytes / (1024.0 * 1024.0);
        var memoryHealthy = memoryUsedMb < memoryLimitMb * 0.9; // < 90% threshold

        checks["memory"] = new HealthCheckResult(
            memoryHealthy ? "healthy" : "degraded",
            $"Used: {memoryUsedMb:F2} MB",
            timeProvider.GetUtcNow());

        // Thread pool check
        ThreadPool.GetAvailableThreads(out var workerThreads, out var completionPortThreads);
        ThreadPool.GetMaxThreads(out var maxWorkerThreads, out var maxCompletionPortThreads);
        var threadPoolHealthy = workerThreads > maxWorkerThreads * 0.1; // > 10% available

        checks["threadPool"] = new HealthCheckResult(
            threadPoolHealthy ? "healthy" : "degraded",
            $"Worker threads available: {workerThreads}/{maxWorkerThreads}",
            timeProvider.GetUtcNow());

        var response = new HealthDetailsResponse(
            overallHealthy ? "healthy" : "unhealthy",
            timeProvider.GetUtcNow(),
            checks);

        return overallHealthy
            ? Results.Ok(response)
            : Results.Json(response, statusCode: StatusCodes.Status503ServiceUnavailable);
    }

    private static async Task<bool> CheckDatabaseAsync(JobEngineDataSource dataSource, CancellationToken cancellationToken)
    {
        try
        {
            // Use a system tenant for health checks
            await using var connection = await dataSource.OpenConnectionAsync("_system", "health", cancellationToken).ConfigureAwait(false);
            await using var command = connection.CreateCommand();
            command.CommandText = "SELECT 1";
            await command.ExecuteScalarAsync(cancellationToken).ConfigureAwait(false);
            return true;
        }
        catch
        {
            return false;
        }
    }
}

/// <summary>
/// Basic health response.
/// </summary>
public sealed record HealthResponse(string Status, DateTimeOffset Timestamp);

/// <summary>
/// Readiness response with dependency status.
/// </summary>
public sealed record ReadinessResponse(
    string Status,
    DateTimeOffset Timestamp,
    IReadOnlyDictionary<string, string> Dependencies);

/// <summary>
/// Individual health check result.
/// </summary>
public sealed record HealthCheckResult(
    string Status,
    string? Details,
    DateTimeOffset CheckedAt);

/// <summary>
/// Detailed health response with all checks.
/// </summary>
public sealed record HealthDetailsResponse(
    string Status,
    DateTimeOffset Timestamp,
    IReadOnlyDictionary<string, HealthCheckResult> Checks);