using Microsoft.Extensions.Hosting;
using Microsoft.Extensions.Logging;
using Microsoft.Extensions.Options;
using WIDESEAWCS_S7Simulator.Core.Enums;
using WIDESEAWCS_S7Simulator.Core.Interfaces;
using WIDESEAWCS_S7Simulator.Core.Protocol;

namespace WIDESEAWCS_S7Simulator.Application.Protocol;

/// <summary>
/// Application 层的协议轮询服务。
/// 按配置编排模板与规则，并触发对应处理器执行。
/// </summary>
public class ProtocolMonitoringHostedService : BackgroundService
{
    private readonly ISimulatorInstanceManager _instanceManager;
    private readonly IProtocolTemplateService _templateService;
    private readonly Dictionary<string, IDeviceProtocolHandler> _protocolHandlers;
    private readonly ILogger<ProtocolMonitoringHostedService> _logger;
    private readonly ProtocolMonitoringOptions _options;
    private readonly Dictionary<string, ProtocolRuntimeState> _runtimeStates = new(StringComparer.OrdinalIgnoreCase);

    public ProtocolMonitoringHostedService(
        ISimulatorInstanceManager instanceManager,
        IProtocolTemplateService templateService,
        IOptions<ProtocolMonitoringOptions> options,
        IEnumerable<IDeviceProtocolHandler> protocolHandlers,
        ILogger<ProtocolMonitoringHostedService> logger)
    {
        _instanceManager = instanceManager;
        _templateService = templateService;
        _protocolHandlers = protocolHandlers.ToDictionary(x => x.ProtocolName, StringComparer.OrdinalIgnoreCase);
        _logger = logger;
        _options = options.Value;
    }

    protected override async Task ExecuteAsync(CancellationToken stoppingToken)
    {
        var intervalMs = Math.Max(50, _options.PollingIntervalMs);

        while (!stoppingToken.IsCancellationRequested)
        {
            try
            {
                var bindings = _options.TemplateBindings;

                foreach (var instance in _instanceManager.GetAllInstances())
                {
                    if (instance.GetState().Status != InstanceStatus.Running)
                    {
                        continue;
                    }

                    var templateId = instance.Config.ProtocolTemplateId;
                    if (string.IsNullOrWhiteSpace(templateId))
                    {
                        continue;
                    }

                    var binding = bindings.FirstOrDefault(x => string.Equals(x.TemplateId, templateId, StringComparison.OrdinalIgnoreCase));
                    if (binding == null)
                    {
                        continue;
                    }

                    if (!_protocolHandlers.TryGetValue(binding.ProtocolName, out var protocolHandler))
                    {
                        continue;
                    }

                    var template = await _templateService.GetByIdAsync(templateId);
                    if (template == null)
                    {
                        continue;
                    }

                    if (!_runtimeStates.TryGetValue(instance.Config.Id, out var runtimeState))
                    {
                        runtimeState = new ProtocolRuntimeState();
                        _runtimeStates[instance.Config.Id] = runtimeState;
                    }

                    // 每轮先把实例当前内存同步到 MemoryStore，再执行规则处理。
                    var memoryData = instance.ExportMemory();
                    instance.MemoryStore.Import(memoryData);

                    var changed = protocolHandler.Process(instance.MemoryStore, template, runtimeState);

                    // 处理器有变更时，回写到 PLC 运行内存。
                    if (changed)
                    {
                        var updated = instance.MemoryStore.Export();
                        instance.ImportMemory(updated);
                    }
                }
            }
            catch (Exception ex)
            {
                _logger.LogWarning(ex, "Protocol monitoring loop failed.");
            }

            await Task.Delay(intervalMs, stoppingToken);
        }
    }
}