using ClaudeDo.Worker.Config;
using ClaudeDo.Worker.Hub;
using ClaudeDo.Worker.Usage.Interfaces;

namespace ClaudeDo.Worker.Usage;

/// <summary>
/// Polls <see cref="IUsageClient"/> on <see cref="WorkerConfig.UsagePollIntervalSeconds"/> and keeps
/// <see cref="UsageState"/> current. Polls once immediately at startup. A failure is logged as a
/// warning at most once per distinct error message, to avoid log spam on a persistent outage.
/// Broadcasts <see cref="HubBroadcaster.UsageUpdated"/> after every poll cycle, success or failure,
/// so the UI can reflect a stale/blocked state as soon as it happens.
/// </summary>
public sealed class UsageMonitorService : BackgroundService
{
    private readonly IUsageClient _client;
    private readonly UsageState _state;
    private readonly WorkerConfig _config;
    private readonly ILogger<UsageMonitorService> _logger;
    private readonly UsageSnapshotBuilder _snapshotBuilder;
    private readonly HubBroadcaster _broadcaster;
    private string? _lastLoggedError;

    public UsageMonitorService(
        IUsageClient client, UsageState state, WorkerConfig config, ILogger<UsageMonitorService> logger,
        UsageSnapshotBuilder snapshotBuilder, HubBroadcaster broadcaster)
    {
        _client = client;
        _state = state;
        _config = config;
        _logger = logger;
        _snapshotBuilder = snapshotBuilder;
        _broadcaster = broadcaster;
    }

    protected override async Task ExecuteAsync(CancellationToken stoppingToken)
    {
        while (!stoppingToken.IsCancellationRequested)
        {
            await TickAsync(stoppingToken);

            try
            {
                await Task.Delay(TimeSpan.FromSeconds(_config.UsagePollIntervalSeconds), stoppingToken);
            }
            catch (OperationCanceledException)
            {
                return;
            }
        }
    }

    internal async Task TickAsync(CancellationToken ct)
    {
        try
        {
            var snapshot = await _client.GetUsageAsync(ct);
            _state.ReportSuccess(snapshot);
            _lastLoggedError = null;
        }
        catch (OperationCanceledException) when (ct.IsCancellationRequested)
        {
            throw;
        }
        catch (Exception ex)
        {
            _state.ReportFailure(ex.Message, DateTime.UtcNow);

            if (_lastLoggedError != ex.Message)
            {
                _logger.LogWarning(ex, "UsageMonitorService: failed to fetch usage: {Message}", ex.Message);
                _lastLoggedError = ex.Message;
            }
        }

        var dto = await _snapshotBuilder.BuildAsync(ct);
        await _broadcaster.UsageUpdated(dto);
    }
}