using Api.SeaHavenIndustries.Observability;
using Data.SeaHavenIndustries;
using Microsoft.EntityFrameworkCore;
using Sentry;

namespace Api.SeaHavenIndustries.Helper
{
    public class VendorDocumentScanWorker : BackgroundService
    {
        private readonly IServiceScopeFactory _scopeFactory;
        private readonly IWebHostEnvironment _environment;
        private readonly ILogger<VendorDocumentScanWorker> _logger;
        private readonly IHub _sentryHub;

        public VendorDocumentScanWorker(
            IServiceScopeFactory scopeFactory,
            IWebHostEnvironment environment,
            ILogger<VendorDocumentScanWorker> logger,
            IHub sentryHub)
        {
            _scopeFactory = scopeFactory;
            _environment = environment;
            _logger = logger;
            _sentryHub = sentryHub;
        }

        protected override async Task ExecuteAsync(CancellationToken stoppingToken)
        {
            while (!stoppingToken.IsCancellationRequested)
            {
                await ScanPendingAsync(stoppingToken);
                await Task.Delay(TimeSpan.FromSeconds(30), stoppingToken);
            }
        }

        private async Task ScanPendingAsync(CancellationToken cancellationToken)
        {
            using var transaction = SentryObservability.BeginBackgroundTransaction(
                _sentryHub,
                "vendor-documents.scan-pending",
                $"{nameof(VendorDocumentScanWorker)}.{nameof(ScanPendingAsync)}");
            try
            {
                using var scope = _scopeFactory.CreateScope();
                var db = scope.ServiceProvider.GetRequiredService<ApplicationDbContext>();
                var scanner = scope.ServiceProvider.GetRequiredService<IDocumentScanner>();
                var pending = await db.VendorCompletionDocuments
                    .Where(document => document.ScanStatus == "Pending")
                    .OrderBy(document => document.CreatedDate)
                    .Take(20)
                    .ToListAsync(cancellationToken);

                foreach (var document in pending)
                {
                    var path = VendorDocumentStorage.ResolvePath(_environment.ContentRootPath, document);
                    var result = await scanner.ScanAsync(path, cancellationToken);
                    if (result == DocumentScanResult.Unavailable)
                    {
                        _logger.LogWarning("Vendor document scan service unavailable; document {DocumentId} remains quarantined", document.Id);
                        continue;
                    }

                    document.ScanStatus = result == DocumentScanResult.Passed ? "Passed" : "Rejected";
                    document.ReviewStatus = result == DocumentScanResult.Passed ? "Processing" : "Rejected";
                    document.RejectionReason = result == DocumentScanResult.Infected
                        ? "The upload failed malware scanning."
                        : document.RejectionReason;
                    document.ScannedAt = DateTime.UtcNow;
                    document.LastModificationTime = DateTime.UtcNow;
                    await db.SaveChangesAsync(cancellationToken);

                    if (result == DocumentScanResult.Infected && File.Exists(path))
                        File.Delete(path);
                }

                transaction.FinishOk();
            }
            catch (OperationCanceledException)
            {
                transaction.FinishCancelled();
                throw;
            }
            catch (Exception ex)
            {
                transaction.FinishError(ex);
                throw;
            }
        }
    }

    public static class VendorDocumentStorage
    {
        public static string Root(string contentRoot) =>
            Path.Combine(contentRoot, "App_Data", "vendor-documents");

        public static string ResolvePath(string contentRoot, int vendorId, int dispatchId, string storedFileName) =>
            Path.Combine(Root(contentRoot), vendorId.ToString(), dispatchId.ToString(), storedFileName);

        public static string ResolvePath(string contentRoot, VendorCompletionDocument document) =>
            ResolvePath(contentRoot, document.VendorId, document.DispatchId, document.StoredFileName);
    }
}