using System.Text.Json;
using Microsoft.Extensions.Hosting;
using WxAgent.Core;

namespace WxAgent.Service;

public interface IAgentEventSource
{
    IAsyncEnumerable<AgentEvent> ListenAsync(CancellationToken cancellationToken);
}

public sealed class EventPump(IAgentBackend backend, EventHub hub, ServiceOptions options, RemoteEventQueue? remoteQueue = null) : BackgroundService
{
    protected override async Task ExecuteAsync(CancellationToken stoppingToken)
    {
        if (backend is not IAgentEventSource source || backend.Capabilities.All(c => c.Operation != "listener-events" || !c.Enabled)) return;
        while (!stoppingToken.IsCancellationRequested)
        {
            try
            {
                await foreach (var item in source.ListenAsync(stoppingToken))
                {
                    var runtime = await LoadRuntimeConfigurationAsync(options, stoppingToken);
                    if (remoteQueue is not null && runtime.Remote.IsConfigured && item.Kind == "message"
                        && item.ChatId is { Length: > 0 } chatId && item.ChatType is { } chatType)
                    {
                        _ = remoteQueue.Enqueue(runtime.Reporting, runtime.Remote.NodeId!, item.AccountId, chatId, chatType,
                            item.Kind, item.At, item.Content);
                    }
                    var localItem = item with { Content = null };
                    foreach (var credential in options.ReadCredentials())
                        if (credential.AccountIds.Length == 0 || credential.AccountIds.Contains(item.AccountId, StringComparer.Ordinal))
                            hub.Publish(credential.PrincipalId, localItem);
                }
            }
            catch (OperationCanceledException) when (stoppingToken.IsCancellationRequested) { return; }
            catch (Exception) { await Task.Delay(TimeSpan.FromSeconds(2), stoppingToken); }
        }
    }

    private static async Task<RemoteNodeConfiguration> LoadRuntimeConfigurationAsync(ServiceOptions options, CancellationToken cancellationToken)
    {
        if (string.IsNullOrWhiteSpace(options.RemoteConfigurationFile))
            return new RemoteNodeConfiguration { Remote = options.Remote ?? new RemoteAgentOptions(), Reporting = options.Reporting };
        try
        {
            return await RemoteNodeConfigurationStore.LoadAsync(options.RemoteConfigurationFile, cancellationToken);
        }
        catch (Exception exception) when (exception is IOException or JsonException or WxAgentException)
        {
            return new RemoteNodeConfiguration();
        }
    }
}