using Microsoft.EntityFrameworkCore;
using Microsoft.Extensions.Options;
using UniVerse.Api.Options;
using UniVerse.Application.Interfaces;
using UniVerse.Domain.Enums;
using UniVerse.Infrastructure.Data;

namespace UniVerse.Api.BackgroundServices;

public sealed class ReviewAnalysisWorker : BackgroundService
{
    private readonly IServiceProvider _services;
    private readonly ReviewAnalysisQueue _queue;
    private readonly ReviewAnalysisOptions _options;
    private readonly ILogger<ReviewAnalysisWorker> _logger;

    public ReviewAnalysisWorker(
        IServiceProvider services,
        ReviewAnalysisQueue queue,
        IOptions<ReviewAnalysisOptions> options,
        ILogger<ReviewAnalysisWorker> logger)
    {
        _services = services;
        _queue = queue;
        _options = options.Value;
        _logger = logger;
    }

    protected override async Task ExecuteAsync(CancellationToken stoppingToken)
    {
        var maxConcurrency = Math.Max(1, _options.MaxConcurrentProcessing);
        _logger.LogInformation(
            "Review analysis worker started with max concurrency {MaxConcurrency}",
            maxConcurrency);

        await EnqueueExistingPendingReviewsAsync(stoppingToken);

        var workers = Enumerable.Range(1, maxConcurrency)
            .Select(workerNumber => ProcessQueueAsync(workerNumber, stoppingToken))
            .ToArray();

        try
        {
            await Task.WhenAll(workers);
        }
        catch (OperationCanceledException) when (stoppingToken.IsCancellationRequested)
        {
            _logger.LogInformation("Review analysis worker stopped");
        }
    }

    private async Task EnqueueExistingPendingReviewsAsync(CancellationToken cancellationToken)
    {
        using var scope = _services.CreateScope();
        var db = scope.ServiceProvider.GetRequiredService<AppDbContext>();

        var pendingReviewIds = await db.Reviews
            .Where(r => r.LlmStatus == ReviewLlmStatus.Pending)
            .OrderBy(r => r.CreatedAt)
            .Select(r => r.Id)
            .ToListAsync(cancellationToken);

        foreach (var reviewId in pendingReviewIds)
            await _queue.EnqueueAsync(reviewId, cancellationToken);

        if (pendingReviewIds.Count > 0)
            _logger.LogInformation(
                "Queued {ReviewCount} pending reviews for immediate analysis",
                pendingReviewIds.Count);
    }

    private async Task ProcessQueueAsync(int workerNumber, CancellationToken cancellationToken)
    {
        await foreach (var reviewId in _queue.ReadAllAsync(cancellationToken))
        {
            try
            {
                using var scope = _services.CreateScope();
                var llmService = scope.ServiceProvider.GetRequiredService<ILlmAnalysisService>();
                await llmService.AnalyzeReviewAsync(reviewId);
            }
            catch (OperationCanceledException) when (cancellationToken.IsCancellationRequested)
            {
                throw;
            }
            catch (Exception ex)
            {
                _logger.LogError(
                    ex,
                    "Review analysis worker {WorkerNumber} failed to process review {ReviewId}",
                    workerNumber,
                    reviewId);
            }
        }
    }
}