// -----------------------------------------------------------------------------
// CacheWarmupHostedService.cs
// Sprint: SPRINT_8200_0013_0001_GW_valkey_advisory_cache
// Task: VCACHE-8200-024
// Description: Background service for cache warmup on startup
// -----------------------------------------------------------------------------

using Microsoft.Extensions.Hosting;
using Microsoft.Extensions.Logging;
using Microsoft.Extensions.Options;

namespace StellaOps.Concelier.Cache.Valkey;

/// <summary>
/// Background hosted service that warms the advisory cache on application startup.
/// </summary>
public sealed class CacheWarmupHostedService : BackgroundService
{
    private readonly IAdvisoryCacheService _cacheService;
    private readonly ConcelierCacheOptions _options;
    private readonly ILogger<CacheWarmupHostedService>? _logger;

    /// <summary>
    /// Initializes a new instance of <see cref="CacheWarmupHostedService"/>.
    /// </summary>
    public CacheWarmupHostedService(
        IAdvisoryCacheService cacheService,
        IOptions<ConcelierCacheOptions> options,
        ILogger<CacheWarmupHostedService>? logger = null)
    {
        _cacheService = cacheService;
        _options = options.Value;
        _logger = logger;
    }

    /// <inheritdoc />
    protected override async Task ExecuteAsync(CancellationToken stoppingToken)
    {
        if (!_options.Enabled || !_options.EnableWarmup)
        {
            _logger?.LogInformation("Cache warmup is disabled");
            return;
        }

        // Wait a short time for the application to fully start
        await Task.Delay(TimeSpan.FromSeconds(5), stoppingToken).ConfigureAwait(false);

        _logger?.LogInformation("Starting cache warmup with limit {Limit}", _options.WarmupLimit);

        try
        {
            await _cacheService.WarmupAsync(_options.WarmupLimit, stoppingToken).ConfigureAwait(false);
            _logger?.LogInformation("Cache warmup completed successfully");
        }
        catch (OperationCanceledException) when (stoppingToken.IsCancellationRequested)
        {
            _logger?.LogInformation("Cache warmup cancelled");
        }
        catch (Exception ex)
        {
            _logger?.LogError(ex, "Cache warmup failed");
        }
    }
}