using Prefab.Catalog.Api.Data;

namespace Prefab.Catalog.Api.Workers;

/// <summary>
/// Background service for seeding data. Collects seed tasks from a channel and executes them concurrently.
/// </summary>
public class DataSeeder(IServiceProvider serviceProvider, IConfiguration configuration, ILogger<DataSeeder> logger) : BackgroundService
{
    private readonly int _workerCount = configuration.GetValue("DataSeederWorkerCount", 4);

    protected override async Task ExecuteAsync(CancellationToken stoppingToken)
    {
        await WaitForDatabaseAsync(stoppingToken);

        var tasks = new List<Task>();

        for (var i = 0; i < _workerCount; i++)
        {
            tasks.Add(Task.Run(async () =>
            {
                await foreach (var seedTask in Prefab.Data.Seeder.Extensions.Channel.Reader.ReadAllAsync(stoppingToken))
                {
                    try
                    {
                        await seedTask(serviceProvider, stoppingToken);
                        logger.LogInformation("Seed task executed successfully.");
                    }
                    catch (Exception ex)
                    {
                        logger.LogError(ex, "Error executing seed task.");
                        // Optionally, add retry logic here.
                    }
                }
            }, stoppingToken));
        }

        await Task.WhenAll(tasks);
    }

    private async Task WaitForDatabaseAsync(CancellationToken stoppingToken)
    {
        var hasLoggedWait = false;

        while (!stoppingToken.IsCancellationRequested)
        {
            try
            {
                using var scope = serviceProvider.CreateScope();
                var db = scope.ServiceProvider.GetRequiredService<AppDb>();

                if (await db.Database.CanConnectAsync(stoppingToken))
                {
                    if (hasLoggedWait)
                    {
                        logger.LogInformation("Database connectivity confirmed. Starting seed workers.");
                    }

                    return;
                }
            }
            catch (Exception ex)
            {
                logger.LogDebug(ex, "Database connectivity probe failed; retrying.");
            }

            if (!hasLoggedWait)
            {
                logger.LogInformation("Waiting for database availability before processing seed tasks...");
                hasLoggedWait = true;
            }

            await Task.Delay(TimeSpan.FromSeconds(1), stoppingToken);
        }
    }
}