using System;
using System.Collections.Generic;
using System.Threading;
using System.Threading.Tasks;
using Microsoft.Extensions.Logging;

namespace StellaOps.Scanner.Worker.Processing;

public sealed class ScanJobProcessor
{
    private readonly IReadOnlyDictionary<string, IScanStageExecutor> _executors;
    private readonly ScanProgressReporter _progressReporter;
    private readonly ILogger<ScanJobProcessor> _logger;

    public ScanJobProcessor(IEnumerable<IScanStageExecutor> executors, ScanProgressReporter progressReporter, ILogger<ScanJobProcessor> logger)
    {
        _progressReporter = progressReporter ?? throw new ArgumentNullException(nameof(progressReporter));
        _logger = logger ?? throw new ArgumentNullException(nameof(logger));

        var map = new Dictionary<string, IScanStageExecutor>(StringComparer.OrdinalIgnoreCase);
        foreach (var executor in executors ?? Array.Empty<IScanStageExecutor>())
        {
            if (executor is null || string.IsNullOrWhiteSpace(executor.StageName))
            {
                continue;
            }

            map[executor.StageName] = executor;
        }

        foreach (var stage in ScanStageNames.Ordered)
        {
            if (map.ContainsKey(stage))
            {
                continue;
            }

            map[stage] = new NoOpStageExecutor(stage);
            _logger.LogDebug("No executor registered for stage {Stage}; using no-op placeholder.", stage);
        }

        _executors = map;
    }

    public async ValueTask ExecuteAsync(ScanJobContext context, CancellationToken cancellationToken)
    {
        ArgumentNullException.ThrowIfNull(context);

        foreach (var stage in ScanStageNames.Ordered)
        {
            cancellationToken.ThrowIfCancellationRequested();

            if (!_executors.TryGetValue(stage, out var executor))
            {
                continue;
            }

            await _progressReporter.ExecuteStageAsync(
                context,
                stage,
                executor.ExecuteAsync,
                cancellationToken).ConfigureAwait(false);
        }
    }
}