package main

import (
	"context"
	"encoding/json"
	"fmt"
	"log/slog"
	"net/url"
	"os"
	"os/signal"
	"strings"
	"sync"
	"syscall"
	"time"

	"github.com/eclipse/paho.golang/autopaho"
	"github.com/eclipse/paho.golang/paho"
	"github.com/joho/godotenv"
	"hub/internal/weather"
)

// MessageHandler wraps the function to process incoming messages
type MessageHandler func(*paho.Publish)

func main() {
	// Load environment variables
	_ = godotenv.Load()

	// Load configuration
	cfg := weather.LoadSubscriberConfig()

	// Setup logging
	var logLevel slog.Level
	switch strings.ToLower(cfg.LogLevel) {
	case "debug":
		logLevel = slog.LevelDebug
	case "warn", "warning":
		logLevel = slog.LevelWarn
	case "error":
		logLevel = slog.LevelError
	default:
		logLevel = slog.LevelInfo
	}

	logger := slog.New(slog.NewJSONHandler(os.Stdout, &slog.HandlerOptions{
		Level: logLevel,
	}))

	// Create context for graceful shutdown
	ctx, cancel := context.WithCancel(context.Background())
	defer cancel()

	// Handle signals
	sigChan := make(chan os.Signal, 1)
	signal.Notify(sigChan, syscall.SIGINT, syscall.SIGTERM)

	go func() {
		sig := <-sigChan
		logger.Info("Received signal", "signal", sig)
		cancel()
	}()

	// Run the subscriber
	logger.Info("Starting MQTT v5 subscriber for FMI weather data",
		"broker", cfg.MQTTBroker,
		"topics", cfg.Topics,
		"qos", cfg.QoS)

	if err := runSubscriber(ctx, cfg, logger); err != nil {
		logger.Error("Subscriber failed", "error", err)
		os.Exit(1)
	}

	logger.Info("Subscriber stopped gracefully")
}

func runSubscriber(ctx context.Context, cfg *weather.SubscriberConfig, logger *slog.Logger) error {
	// Initialize statistics
	stats := weather.InitTopicStats()
	statsMutex := &sync.RWMutex{}

	// Create MQTT client with custom configuration
	serverURL, err := url.Parse(cfg.MQTTBroker)
	if err != nil {
		return fmt.Errorf("invalid MQTT broker URL: %w", err)
	}

	// Create message handler
	messageHandler := func(pr paho.PublishReceived) (bool, error) {
		go handleMessage(pr.Packet, logger, stats, statsMutex)
		return true, nil
	}

	// Client configuration
	cliCfg := autopaho.ClientConfig{
		ServerUrls: []*url.URL{serverURL},
		KeepAlive:  uint16(cfg.MQTTKeepAlive.Seconds()),
		ClientConfig: paho.ClientConfig{
			ClientID: fmt.Sprintf("%s-%d", cfg.MQTTClientID, os.Getpid()),
			OnPublishReceived: []func(paho.PublishReceived) (bool, error){
				messageHandler,
			},
			OnServerDisconnect: func(d *paho.Disconnect) {
				if d != nil && d.ReasonCode != 0 {
					logger.Warn("MQTT disconnected", "reason", d.ReasonCode)
				} else {
					logger.Info("MQTT disconnected gracefully")
				}
			},
		},
		ConnectUsername: cfg.MQTTUsername,
		ConnectPassword: []byte(cfg.MQTTPassword),
		ConnectTimeout:  30 * time.Second,
	}

	cliCfg.CleanStartOnInitialConnection = false
	cliCfg.SessionExpiryInterval = uint32(cfg.MQTTSessionExp.Seconds())

	// Connection callbacks
	cliCfg.OnConnectionUp = func(cm *autopaho.ConnectionManager, connAck *paho.Connack) {
		logger.Info("MQTT v5 connected",
			"session_present", connAck.SessionPresent,
			"keep_alive", cfg.MQTTKeepAlive)

		// Subscribe to topics after connection is established
		if len(cfg.Topics) > 0 {
			subscriptions := make([]paho.SubscribeOptions, len(cfg.Topics))
			for i, topic := range cfg.Topics {
				subscriptions[i] = paho.SubscribeOptions{
					Topic: topic,
					QoS:   byte(cfg.QoS),
				}
			}

			ctx, cancel := context.WithTimeout(context.Background(), 10*time.Second)
			defer cancel()

			// FIXED: SubscriptionIdentifier is a pointer
			subID := int(1)
			subProps := &paho.SubscribeProperties{
				SubscriptionIdentifier: &subID,
			}

			if _, err := cm.Subscribe(ctx, &paho.Subscribe{
				Subscriptions: subscriptions,
				Properties:    subProps,
			}); err != nil {
				logger.Error("Failed to subscribe", "error", err)
			} else {
				logger.Info("Subscribed to topics",
					"topics", cfg.Topics,
					"qos", cfg.QoS)
			}
		}
	}

	cliCfg.OnConnectError = func(err error) {
		logger.Error("MQTT connection error", "error", err)
	}

	// Connect to broker
	mqttClient, err := autopaho.NewConnection(ctx, cliCfg)
	if err != nil {
		return fmt.Errorf("failed to create MQTT connection: %w", err)
	}

	// Wait for connection
	err = mqttClient.AwaitConnection(ctx)
	if err != nil {
		return fmt.Errorf("failed to establish MQTT connection: %w", err)
	}

	defer func() {
		discCtx, cancel := context.WithTimeout(context.Background(), 5*time.Second)
		defer cancel()

		if err := mqttClient.Disconnect(discCtx); err != nil {
			logger.Error("Failed to disconnect MQTT", "error", err)
		}
	}()

	logger.Info("Subscriber started and waiting for messages...")

	// Statistics reporting goroutine
	ticker := time.NewTicker(30 * time.Second)
	defer ticker.Stop()

	for {
		select {
		case <-ctx.Done():
			// Print final statistics
			statsMutex.RLock()
			finalStats := stats.MessagesReceived
			statsMutex.RUnlock()

			if len(finalStats) > 0 {
				logger.Info("Final message statistics", "stats", finalStats)
			}
			return nil

		case <-ticker.C:
			if cfg.EnableDebug {
				statsMutex.RLock()
				currentStats := stats.MessagesReceived
				statsMutex.RUnlock()

				if len(currentStats) > 0 {
					logger.Debug("Message statistics", "stats", currentStats)
				}
			}
		}
	}
}

func handleMessage(pkt *paho.Publish, logger *slog.Logger,
	stats *weather.TopicStats, mutex *sync.RWMutex) {

	// Update statistics
	mutex.Lock()
	stats.MessagesReceived[pkt.Topic]++
	stats.LastMessageTime[pkt.Topic] = time.Now()
	mutex.Unlock()

	// Route based on topic pattern
	switch {
	case strings.HasPrefix(pkt.Topic, "weather/obs/"):
		processObservationMessage(pkt, logger)
	case strings.HasPrefix(pkt.Topic, "weather/forecast/"):
		processForecastMessage(pkt, logger)
	default:
		logger.Warn("Unknown topic pattern", "topic", pkt.Topic)
		// Try to decode as generic JSON
		var data map[string]interface{}
		if err := json.Unmarshal(pkt.Payload, &data); err == nil {
			logger.Info("Generic message", "topic", pkt.Topic, "data", data)
		} else {
			logger.Info("Raw message", "topic", pkt.Topic, "payload", string(pkt.Payload))
		}
	}
}

func processObservationMessage(pkt *paho.Publish, logger *slog.Logger) {
	var obs weather.Observation
	if err := json.Unmarshal(pkt.Payload, &obs); err != nil {
		logger.Error("Failed to parse observation",
			"error", err,
			"topic", pkt.Topic)
		return
	}

	// Extract user properties
	userProps := make(map[string]string)
	if pkt.Properties != nil {
		for _, prop := range pkt.Properties.User {
			userProps[prop.Key] = prop.Value
		}
	}

	// Format value for display
	valueStr := "null"
	if obs.Value != nil {
		valueStr = fmt.Sprintf("%.2f", *obs.Value)
	}

	logger.Info("Observation received",
		"topic", pkt.Topic,
		"station", obs.Station,
		"parameter", obs.Parameter,
		"time", obs.Time.Format(time.RFC3339),
		"value", valueStr,
		"user_properties", userProps,
		"retain", pkt.Retain,
		"qos", pkt.QoS)
}

func processForecastMessage(pkt *paho.Publish, logger *slog.Logger) {
	var fc weather.ForecastValue
	if err := json.Unmarshal(pkt.Payload, &fc); err != nil {
		logger.Error("Failed to parse forecast",
			"error", err,
			"topic", pkt.Topic)
		return
	}

	// Extract user properties
	userProps := make(map[string]string)
	if pkt.Properties != nil {
		for _, prop := range pkt.Properties.User {
			userProps[prop.Key] = prop.Value
		}
	}

	// Format value for display
	valueStr := "null"
	if fc.Value != nil {
		valueStr = fmt.Sprintf("%.2f", *fc.Value)
	}

	logger.Info("Forecast received",
		"topic", pkt.Topic,
		"model", fc.Model,
		"parameter", fc.Parameter,
		"run_time", fc.RunTime.Format(time.RFC3339),
		"forecast_time", fc.ForecastTime.Format(time.RFC3339),
		"location", fmt.Sprintf("(%.4f,%.4f)", fc.Location.Lat, fc.Location.Lon),
		"value", valueStr,
		"user_properties", userProps,
		"retain", pkt.Retain,
		"qos", pkt.QoS)
}