using Microsoft.AspNetCore.Mvc;
using StellaOps.JobEngine.Core.Scale;
using static StellaOps.Localization.T;

namespace StellaOps.JobEngine.WebService.Endpoints;

/// <summary>
/// Endpoints for autoscaling metrics and load shedding status.
/// </summary>
public static class ScaleEndpoints
{
    /// <summary>
    /// Maps scale endpoints to the route builder.
    /// </summary>
    public static IEndpointRouteBuilder MapScaleEndpoints(this IEndpointRouteBuilder app)
    {
        var group = app.MapGroup("/scale")
            .WithTags("Scaling")
            .AllowAnonymous();

        // Autoscaling metrics for KEDA/HPA
        group.MapGet("/metrics", GetAutoscaleMetrics)
            .WithName("Orchestrator_AutoscaleMetrics")
            .WithDescription(_t("orchestrator.scale.metrics_description"));

        // Prometheus-compatible metrics endpoint
        group.MapGet("/metrics/prometheus", GetPrometheusMetrics)
            .WithName("Orchestrator_PrometheusScaleMetrics")
            .WithDescription(_t("orchestrator.scale.prometheus_description"));

        // Load shedding status
        group.MapGet("/load", GetLoadStatus)
            .WithName("Orchestrator_LoadStatus")
            .WithDescription(_t("orchestrator.scale.load_description"));

        // Scale snapshot for debugging
        group.MapGet("/snapshot", GetScaleSnapshot)
            .WithName("Orchestrator_ScaleSnapshot")
            .WithDescription(_t("orchestrator.scale.snapshot_description"));

        // Startup probe (slower to pass, includes warmup check)
        app.MapGet("/startupz", GetStartupStatus)
            .WithName("Orchestrator_StartupProbe")
            .WithTags("Health")
            .WithDescription(_t("orchestrator.scale.startupz_description"))
            .AllowAnonymous();

        return app;
    }

    private static IResult GetAutoscaleMetrics(
        [FromServices] ScaleMetrics scaleMetrics)
    {
        var metrics = scaleMetrics.GetAutoscaleMetrics();
        return Results.Ok(metrics);
    }

    private static IResult GetPrometheusMetrics(
        [FromServices] ScaleMetrics scaleMetrics,
        [FromServices] LoadShedder loadShedder)
    {
        var metrics = scaleMetrics.GetAutoscaleMetrics();
        var loadStatus = loadShedder.GetStatus();

        // Format as Prometheus text exposition
        var lines = new List<string>
        {
            "# HELP orchestrator_queue_depth Current number of pending jobs",
            "# TYPE orchestrator_queue_depth gauge",
            $"orchestrator_queue_depth {metrics.QueueDepth}",
            "",
            "# HELP orchestrator_active_jobs Current number of active jobs",
            "# TYPE orchestrator_active_jobs gauge",
            $"orchestrator_active_jobs {metrics.ActiveJobs}",
            "",
            "# HELP orchestrator_dispatch_latency_p95_ms P95 dispatch latency in milliseconds",
            "# TYPE orchestrator_dispatch_latency_p95_ms gauge",
            $"orchestrator_dispatch_latency_p95_ms {metrics.DispatchLatencyP95Ms:F2}",
            "",
            "# HELP orchestrator_dispatch_latency_p99_ms P99 dispatch latency in milliseconds",
            "# TYPE orchestrator_dispatch_latency_p99_ms gauge",
            $"orchestrator_dispatch_latency_p99_ms {metrics.DispatchLatencyP99Ms:F2}",
            "",
            "# HELP orchestrator_recommended_replicas Recommended replica count for autoscaling",
            "# TYPE orchestrator_recommended_replicas gauge",
            $"orchestrator_recommended_replicas {metrics.RecommendedReplicas}",
            "",
            "# HELP orchestrator_under_pressure Whether the system is under pressure (1=yes, 0=no)",
            "# TYPE orchestrator_under_pressure gauge",
            $"orchestrator_under_pressure {(metrics.IsUnderPressure ? 1 : 0)}",
            "",
            "# HELP orchestrator_load_factor Current load factor (1.0 = at target)",
            "# TYPE orchestrator_load_factor gauge",
            $"orchestrator_load_factor {loadStatus.LoadFactor:F3}",
            "",
            "# HELP orchestrator_load_shedding_state Current load shedding state (0=normal, 1=warning, 2=critical, 3=emergency)",
            "# TYPE orchestrator_load_shedding_state gauge",
            $"orchestrator_load_shedding_state {(int)loadStatus.State}",
            "",
            "# HELP orchestrator_scale_samples Number of latency samples in measurement window",
            "# TYPE orchestrator_scale_samples gauge",
            $"orchestrator_scale_samples {metrics.SamplesInWindow}"
        };

        return Results.Text(string.Join("\n", lines), "text/plain");
    }

    private static IResult GetLoadStatus(
        [FromServices] LoadShedder loadShedder)
    {
        var status = loadShedder.GetStatus();
        return Results.Ok(status);
    }

    private static IResult GetScaleSnapshot(
        [FromServices] ScaleMetrics scaleMetrics,
        [FromServices] LoadShedder loadShedder)
    {
        var snapshot = scaleMetrics.GetSnapshot();
        var loadStatus = loadShedder.GetStatus();

        return Results.Ok(new
        {
            snapshot.Timestamp,
            snapshot.TotalQueueDepth,
            snapshot.TotalActiveJobs,
            DispatchLatency = new
            {
                snapshot.DispatchLatency.Count,
                snapshot.DispatchLatency.Min,
                snapshot.DispatchLatency.Max,
                snapshot.DispatchLatency.Avg,
                snapshot.DispatchLatency.P50,
                snapshot.DispatchLatency.P95,
                snapshot.DispatchLatency.P99
            },
            LoadShedding = new
            {
                loadStatus.State,
                loadStatus.LoadFactor,
                loadStatus.IsSheddingLoad,
                loadStatus.AcceptingPriority,
                loadStatus.RecommendedDelayMs
            },
            QueueDepthByKey = snapshot.QueueDepthByKey,
            ActiveJobsByKey = snapshot.ActiveJobsByKey
        });
    }

    private static IResult GetStartupStatus(
        [FromServices] ScaleMetrics scaleMetrics,
        [FromServices] StartupProbe startupProbe)
    {
        if (!startupProbe.IsReady)
        {
            return Results.Json(new StartupResponse(
                Status: "starting",
                Ready: false,
                UptimeSeconds: startupProbe.UptimeSeconds,
                WarmupComplete: startupProbe.WarmupComplete,
                Message: startupProbe.StatusMessage),
                statusCode: StatusCodes.Status503ServiceUnavailable);
        }

        return Results.Ok(new StartupResponse(
            Status: "started",
            Ready: true,
            UptimeSeconds: startupProbe.UptimeSeconds,
            WarmupComplete: startupProbe.WarmupComplete,
            Message: "Service is ready"));
    }
}

/// <summary>
/// Startup probe response.
/// </summary>
public sealed record StartupResponse(
    string Status,
    bool Ready,
    double UptimeSeconds,
    bool WarmupComplete,
    string Message);

/// <summary>
/// Startup probe service that tracks warmup status.
/// </summary>
public sealed class StartupProbe
{
    private readonly DateTimeOffset _startTime = DateTimeOffset.UtcNow;
    private readonly TimeSpan _minWarmupTime;
    private volatile bool _warmupComplete;
    private string _statusMessage = "Starting up";

    public StartupProbe(TimeSpan? minWarmupTime = null)
    {
        _minWarmupTime = minWarmupTime ?? TimeSpan.FromSeconds(5);
    }

    /// <summary>
    /// Gets whether the service is ready.
    /// </summary>
    public bool IsReady => WarmupComplete;

    /// <summary>
    /// Gets whether warmup has completed.
    /// </summary>
    public bool WarmupComplete
    {
        get
        {
            if (_warmupComplete) return true;

            // Auto-complete warmup after minimum time
            if (UptimeSeconds >= _minWarmupTime.TotalSeconds)
            {
                _warmupComplete = true;
                _statusMessage = "Warmup complete";
            }

            return _warmupComplete;
        }
    }

    /// <summary>
    /// Gets the uptime in seconds.
    /// </summary>
    public double UptimeSeconds => (DateTimeOffset.UtcNow - _startTime).TotalSeconds;

    /// <summary>
    /// Gets the current status message.
    /// </summary>
    public string StatusMessage => _statusMessage;

    /// <summary>
    /// Marks warmup as complete.
    /// </summary>
    public void MarkWarmupComplete()
    {
        _warmupComplete = true;
        _statusMessage = "Warmup complete";
    }

    /// <summary>
    /// Updates the status message.
    /// </summary>
    public void SetStatus(string message)
    {
        _statusMessage = message;
    }
}