// -----------------------------------------------------------------------------
// EpssIngestJob.cs
// Sprint: SPRINT_3410_0001_0001_epss_ingestion_storage
// Task: EPSS-3410-009
// Description: Background job that ingests EPSS data from online or bundle sources.
// -----------------------------------------------------------------------------

using System.Diagnostics;
using Microsoft.Extensions.Hosting;
using Microsoft.Extensions.Logging;
using Microsoft.Extensions.Options;
using StellaOps.Scanner.Storage.Epss;
using StellaOps.Scanner.Storage.Repositories;

namespace StellaOps.Scanner.Worker.Processing;

/// <summary>
/// Options for the EPSS ingestion job.
/// </summary>
public sealed class EpssIngestOptions
{
    /// <summary>
    /// Configuration section name.
    /// </summary>
    public const string SectionName = "Epss:Ingest";

    /// <summary>
    /// Whether the job is enabled. Default: true.
    /// </summary>
    public bool Enabled { get; set; } = true;

    /// <summary>
    /// Cron schedule for EPSS ingestion. Default: "0 5 0 * * *" (00:05 UTC daily).
    /// </summary>
    public string Schedule { get; set; } = "0 5 0 * * *";

    /// <summary>
    /// Source type: "online" or "bundle". Default: "online".
    /// </summary>
    public string SourceType { get; set; } = "online";

    /// <summary>
    /// Bundle path for air-gapped ingestion (when SourceType is "bundle").
    /// </summary>
    public string? BundlePath { get; set; }

    /// <summary>
    /// Initial delay before first run. Default: 30 seconds.
    /// </summary>
    public TimeSpan InitialDelay { get; set; } = TimeSpan.FromSeconds(30);

    /// <summary>
    /// Retry delay on failure. Default: 5 minutes.
    /// </summary>
    public TimeSpan RetryDelay { get; set; } = TimeSpan.FromMinutes(5);

    /// <summary>
    /// Maximum retry attempts. Default: 3.
    /// </summary>
    public int MaxRetries { get; set; } = 3;
}

/// <summary>
/// Background service that ingests EPSS data on a schedule.
/// Supports online (FIRST.org) and offline (bundle) sources.
/// </summary>
public sealed class EpssIngestJob : BackgroundService
{
    private readonly IEpssRepository _repository;
    private readonly EpssOnlineSource _onlineSource;
    private readonly EpssBundleSource _bundleSource;
    private readonly EpssCsvStreamParser _parser;
    private readonly IOptions<EpssIngestOptions> _options;
    private readonly TimeProvider _timeProvider;
    private readonly ILogger<EpssIngestJob> _logger;
    private readonly ActivitySource _activitySource = new("StellaOps.Scanner.EpssIngest");

    public EpssIngestJob(
        IEpssRepository repository,
        EpssOnlineSource onlineSource,
        EpssBundleSource bundleSource,
        EpssCsvStreamParser parser,
        IOptions<EpssIngestOptions> options,
        TimeProvider timeProvider,
        ILogger<EpssIngestJob> logger)
    {
        _repository = repository ?? throw new ArgumentNullException(nameof(repository));
        _onlineSource = onlineSource ?? throw new ArgumentNullException(nameof(onlineSource));
        _bundleSource = bundleSource ?? throw new ArgumentNullException(nameof(bundleSource));
        _parser = parser ?? throw new ArgumentNullException(nameof(parser));
        _options = options ?? throw new ArgumentNullException(nameof(options));
        _timeProvider = timeProvider ?? throw new ArgumentNullException(nameof(timeProvider));
        _logger = logger ?? throw new ArgumentNullException(nameof(logger));
    }

    protected override async Task ExecuteAsync(CancellationToken stoppingToken)
    {
        _logger.LogInformation("EPSS ingest job started");

        var opts = _options.Value;

        if (!opts.Enabled)
        {
            _logger.LogInformation("EPSS ingest job is disabled");
            return;
        }

        // Initial delay to let the system stabilize
        await Task.Delay(opts.InitialDelay, stoppingToken);

        while (!stoppingToken.IsCancellationRequested)
        {
            var now = _timeProvider.GetUtcNow();
            var nextRun = ComputeNextRun(now, opts.Schedule);
            var delay = nextRun - now;

            if (delay > TimeSpan.Zero)
            {
                _logger.LogDebug("EPSS ingest job waiting until {NextRun}", nextRun);
                await Task.Delay(delay, stoppingToken);
            }

            if (stoppingToken.IsCancellationRequested)
            {
                break;
            }

            await RunIngestionWithRetryAsync(stoppingToken);
        }

        _logger.LogInformation("EPSS ingest job stopped");
    }

    /// <summary>
    /// Runs ingestion for a specific date. Used by tests and manual triggers.
    /// </summary>
    public async Task IngestAsync(DateOnly modelDate, CancellationToken cancellationToken = default)
    {
        using var activity = _activitySource.StartActivity("epss.ingest", ActivityKind.Internal);
        activity?.SetTag("epss.model_date", modelDate.ToString("yyyy-MM-dd"));

        var opts = _options.Value;
        var stopwatch = Stopwatch.StartNew();

        _logger.LogInformation("Starting EPSS ingestion for {ModelDate}", modelDate);

        try
        {
            // Get source based on configuration
            IEpssSource source = opts.SourceType.Equals("bundle", StringComparison.OrdinalIgnoreCase)
                ? _bundleSource
                : _onlineSource;

            // Retrieve the EPSS file
            var sourceFile = await source.GetAsync(modelDate, cancellationToken).ConfigureAwait(false);

            _logger.LogInformation(
                "Retrieved EPSS file from {SourceUri}, size={Size}",
                sourceFile.SourceUri,
                sourceFile.Content.Length);

            // Begin import run
            var importRun = await _repository.BeginImportAsync(
                modelDate,
                sourceFile.SourceUri,
                _timeProvider.GetUtcNow(),
                sourceFile.FileSha256,
                cancellationToken).ConfigureAwait(false);

            _logger.LogDebug("Created import run {ImportRunId}", importRun.ImportRunId);

            try
            {
                // Parse and write snapshot
                await using var stream = new MemoryStream(sourceFile.Content);
                var session = _parser.ParseGzip(stream);

                var writeResult = await _repository.WriteSnapshotAsync(
                    importRun.ImportRunId,
                    modelDate,
                    _timeProvider.GetUtcNow(),
                    session,
                    cancellationToken).ConfigureAwait(false);

                // Mark success
                await _repository.MarkImportSucceededAsync(
                    importRun.ImportRunId,
                    session.RowCount,
                    session.DecompressedSha256,
                    session.ModelVersionTag,
                    session.PublishedDate,
                    cancellationToken).ConfigureAwait(false);

                stopwatch.Stop();

                _logger.LogInformation(
                    "EPSS ingestion completed: modelDate={ModelDate}, rows={RowCount}, cves={CveCount}, duration={Duration}ms",
                    modelDate,
                    writeResult.RowCount,
                    writeResult.DistinctCveCount,
                    stopwatch.ElapsedMilliseconds);

                activity?.SetTag("epss.row_count", writeResult.RowCount);
                activity?.SetTag("epss.cve_count", writeResult.DistinctCveCount);
                activity?.SetTag("epss.duration_ms", stopwatch.ElapsedMilliseconds);
            }
            catch (Exception ex)
            {
                await _repository.MarkImportFailedAsync(
                    importRun.ImportRunId,
                    ex.Message,
                    cancellationToken).ConfigureAwait(false);

                throw;
            }
        }
        catch (Exception ex)
        {
            _logger.LogError(ex, "EPSS ingestion failed for {ModelDate}", modelDate);
            activity?.SetStatus(ActivityStatusCode.Error, ex.Message);
            throw;
        }
    }

    private async Task RunIngestionWithRetryAsync(CancellationToken cancellationToken)
    {
        var opts = _options.Value;
        var modelDate = DateOnly.FromDateTime(_timeProvider.GetUtcNow().UtcDateTime);

        for (var attempt = 1; attempt <= opts.MaxRetries; attempt++)
        {
            try
            {
                await IngestAsync(modelDate, cancellationToken);
                return;
            }
            catch (Exception ex) when (attempt < opts.MaxRetries)
            {
                _logger.LogWarning(
                    ex,
                    "EPSS ingestion attempt {Attempt}/{MaxRetries} failed, retrying in {RetryDelay}",
                    attempt,
                    opts.MaxRetries,
                    opts.RetryDelay);

                await Task.Delay(opts.RetryDelay, cancellationToken);
            }
            catch (Exception ex)
            {
                _logger.LogError(
                    ex,
                    "EPSS ingestion failed after {MaxRetries} attempts",
                    opts.MaxRetries);
            }
        }
    }

    private static DateTimeOffset ComputeNextRun(DateTimeOffset now, string cronSchedule)
    {
        // Simple cron parser for "0 5 0 * * *" (seconds minutes hours day month dayOfWeek)
        // For MVP, we just schedule for 00:05 UTC the next day
        var today = now.UtcDateTime.Date;
        var scheduledTime = today.AddMinutes(5);

        if (now.UtcDateTime > scheduledTime)
        {
            scheduledTime = scheduledTime.AddDays(1);
        }

        return new DateTimeOffset(scheduledTime, TimeSpan.Zero);
    }
}