package main

import (
	"context"
	"encoding/json"
	"fmt"
	"log/slog"
	"os"
	"os/signal"
	"strconv"
	"strings"
	"syscall"
	"time"

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

type PublisherConfig struct {
	// FMI API
	FMIEndpoint string `env:"FMI_ENDPOINT"`

	// Observation
	StationID     int           `env:"STATION_ID"`
	ObsPollEvery  time.Duration `env:"OBS_POLL_EVERY"`
	ObsSafetyLag  time.Duration `env:"OBS_SAFETY_LAG"`
	ObsTimestep   int           `env:"OBS_TIMESTEP"`
	WatermarkFile string        `env:"WATERMARK_FILE"`

	// Forecast
	FcPollEvery time.Duration `env:"FC_POLL_EVERY"`
	HelLat      float64       `env:"HEL_LAT"`
	HelLon      float64       `env:"HEL_LON"`

	// MQTT
	MQTTBroker     string        `env:"MQTT_BROKER"`
	MQTTClientID   string        `env:"MQTT_CLIENT_ID"`
	MQTTUsername   string        `env:"MQTT_USERNAME"`
	MQTTPassword   string        `env:"MQTT_PASSWORD"`
	MQTTKeepAlive  time.Duration `env:"MQTT_KEEP_ALIVE"`
	MQTTSessionExp time.Duration `env:"MQTT_SESSION_EXP"`

	// Application
	LogLevel    string        `env:"LOG_LEVEL"`
	HTTPTimeout time.Duration `env:"HTTP_TIMEOUT"`
}

func loadPublisherConfig() *PublisherConfig {
	_ = godotenv.Load()

	return &PublisherConfig{
		FMIEndpoint:    weather.GetEnv("FMI_ENDPOINT", "https://opendata.fmi.fi/wfs"),
		StationID:      weather.ParseInt(weather.GetEnv("STATION_ID", "100968")),
		ObsPollEvery:   weather.ParseDuration(weather.GetEnv("OBS_POLL_EVERY", "5m")),
		ObsSafetyLag:   weather.ParseDuration(weather.GetEnv("OBS_SAFETY_LAG", "2m")),
		ObsTimestep:    weather.ParseInt(weather.GetEnv("OBS_TIMESTEP", "60")),
		WatermarkFile:  weather.GetEnv("WATERMARK_FILE", "obs_watermark.txt"),
		FcPollEvery:    weather.ParseDuration(weather.GetEnv("FC_POLL_EVERY", "1h")),
		HelLat:         weather.ParseFloat(weather.GetEnv("HEL_LAT", "60.1699")),
		HelLon:         weather.ParseFloat(weather.GetEnv("HEL_LON", "24.9384")),
		MQTTBroker:     weather.GetEnv("MQTT_BROKER", "tcp://localhost:1883"),
		MQTTClientID:   weather.GetEnv("MQTT_CLIENT_ID", "fmi-publisher"),
		MQTTUsername:   weather.GetEnv("MQTT_USERNAME", ""),
		MQTTPassword:   weather.GetEnv("MQTT_PASSWORD", ""),
		MQTTKeepAlive:  weather.ParseDuration(weather.GetEnv("MQTT_KEEP_ALIVE", "60s")),
		MQTTSessionExp: weather.ParseDuration(weather.GetEnv("MQTT_SESSION_EXP", "1h")),
		LogLevel:       weather.GetEnv("LOG_LEVEL", "info"),
		HTTPTimeout:    weather.ParseDuration(weather.GetEnv("HTTP_TIMEOUT", "30s")),
	}
}

func loadWatermark(filename string) time.Time {
	b, err := os.ReadFile(filename)
	if err != nil {
		return time.Now().UTC().Add(-24 * time.Hour)
	}
	sec, err := strconv.ParseInt(strings.TrimSpace(string(b)), 10, 64)
	if err != nil {
		return time.Now().UTC().Add(-24 * time.Hour)
	}
	return time.Unix(sec, 0).UTC()
}

func storeWatermark(filename string, t time.Time) error {
	data := []byte(fmt.Sprintf("%d", t.Unix()))
	return os.WriteFile(filename, data, 0644)
}

func publishObservation(cm *autopaho.ConnectionManager, obs weather.Observation, logger *slog.Logger) error {
	topic := fmt.Sprintf("weather/obs/fmi/%d/%s", obs.Station, obs.Parameter)

	// Safe JSON structure
	type SafeObservation struct {
		Station   int                  `json:"station"`
		Parameter string               `json:"parameter"`
		Time      time.Time            `json:"time"`
		Value     *weather.JSONFloat64 `json:"value,omitempty"`
	}

	var safeValue *weather.JSONFloat64
	if obs.Value != nil {
		v := weather.JSONFloat64(*obs.Value)
		safeValue = &v
	}

	safeObs := SafeObservation{
		Station:   obs.Station,
		Parameter: obs.Parameter,
		Time:      obs.Time,
		Value:     safeValue,
	}

	b, err := json.Marshal(safeObs)
	if err != nil {
		return err
	}

	// MQTT v5 publish properties
	props := &paho.PublishProperties{
		User: []paho.UserProperty{
			{Key: "station_id", Value: fmt.Sprintf("%d", obs.Station)},
			{Key: "parameter", Value: obs.Parameter},
			{Key: "observation_time", Value: obs.Time.Format(time.RFC3339)},
			{Key: "data_type", Value: "observation"},
			{Key: "source", Value: "fmi"},
		},
	}

	pb := &paho.Publish{
		Topic:      topic,
		QoS:        1,
		Retain:     false,
		Payload:    b,
		Properties: props,
	}

	// Publish with context timeout
	ctx, cancel := context.WithTimeout(context.Background(), 5*time.Second)
	defer cancel()

	_, err = cm.Publish(ctx, pb)
	if err != nil {
		return fmt.Errorf("failed to publish observation: %w", err)
	}

	logger.Debug("Published observation",
		"topic", topic,
		"station", obs.Station,
		"parameter", obs.Parameter,
		"value", obs.Value,
		"time", obs.Time)

	return nil
}

func publishForecast(cm *autopaho.ConnectionManager, fc weather.ForecastValue, logger *slog.Logger) error {
	topic := fmt.Sprintf(
		"weather/forecast/fmi/harmonie/helsinki/run=%s/%s",
		fc.RunTime.Format(time.RFC3339),
		fc.Parameter,
	)

	// Safe JSON structure
	type SafeForecastValue struct {
		Location struct {
			Lat float64 `json:"lat"`
			Lon float64 `json:"lon"`
		} `json:"location"`
		Model        string               `json:"model"`
		RunTime      time.Time            `json:"run_time"`
		ForecastTime time.Time            `json:"forecast_time"`
		Parameter    string               `json:"parameter"`
		Value        *weather.JSONFloat64 `json:"value,omitempty"`
	}

	var safeValue *weather.JSONFloat64
	if fc.Value != nil {
		v := weather.JSONFloat64(*fc.Value)
		safeValue = &v
	}

	safeFc := SafeForecastValue{
		Location:     fc.Location,
		Model:        fc.Model,
		RunTime:      fc.RunTime,
		ForecastTime: fc.ForecastTime,
		Parameter:    fc.Parameter,
		Value:        safeValue,
	}

	b, err := json.Marshal(safeFc)
	if err != nil {
		return err
	}

	// MQTT v5 publish properties
	props := &paho.PublishProperties{
		User: []paho.UserProperty{
			{Key: "model", Value: fc.Model},
			{Key: "parameter", Value: fc.Parameter},
			{Key: "run_time", Value: fc.RunTime.Format(time.RFC3339)},
			{Key: "forecast_time", Value: fc.ForecastTime.Format(time.RFC3339)},
			{Key: "data_type", Value: "forecast"},
			{Key: "source", Value: "fmi"},
			{Key: "location_lat", Value: fmt.Sprintf("%.4f", fc.Location.Lat)},
			{Key: "location_lon", Value: fmt.Sprintf("%.4f", fc.Location.Lon)},
		},
	}

	pb := &paho.Publish{
		Topic:      topic,
		QoS:        1,
		Retain:     true, // Forecasts are retained since they don't change
		Payload:    b,
		Properties: props,
	}

	// Publish with context timeout
	ctx, cancel := context.WithTimeout(context.Background(), 5*time.Second)
	defer cancel()

	_, err = cm.Publish(ctx, pb)
	if err != nil {
		return fmt.Errorf("failed to publish forecast: %w", err)
	}

	logger.Debug("Published forecast",
		"topic", topic,
		"parameter", fc.Parameter,
		"run_time", fc.RunTime,
		"forecast_time", fc.ForecastTime)

	return nil
}

func runPublisher(ctx context.Context, cfg *PublisherConfig, logger *slog.Logger) error {
	// Load initial state
	lastObs := loadWatermark(cfg.WatermarkFile)
	lastFcRun := time.Time{}

	// Create MQTT client
	mqttCfg := weather.MQTTConfig{
		Broker:        cfg.MQTTBroker,
		ClientID:      cfg.MQTTClientID,
		Username:      cfg.MQTTUsername,
		Password:      cfg.MQTTPassword,
		KeepAlive:     cfg.MQTTKeepAlive,
		SessionExpiry: cfg.MQTTSessionExp,
		Timeout:       cfg.HTTPTimeout,
	}

	mqttClient, err := weather.CreateMQTTClient(ctx, mqttCfg, func(cm *autopaho.ConnectionManager, connAck *paho.Connack) {
		logger.Info("MQTT v5 connected",
			"session_present", connAck.SessionPresent,
			"keep_alive", cfg.MQTTKeepAlive)
	})
	if err != nil {
		return fmt.Errorf("failed to connect to MQTT: %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)
		}
	}()

	// Create timers
	obsTimer := time.NewTimer(0) // Start immediately
	fcTimer := time.NewTimer(0)  // Start immediately

	defer obsTimer.Stop()
	defer fcTimer.Stop()

	logger.Info("Poller started",
		"obs_interval", cfg.ObsPollEvery,
		"fc_interval", cfg.FcPollEvery,
		"mqtt_broker", cfg.MQTTBroker)

	for {
		select {
		case <-ctx.Done():
			logger.Info("Poller stopping")
			return nil

		case <-obsTimer.C:
			// Poll observations
			obsEnd := time.Now().UTC().Add(-cfg.ObsSafetyLag)
			if obsEnd.After(lastObs) {
				logger.Info("Polling observations", "from", lastObs, "to", obsEnd)

				url := weather.BuildObservationsURL(cfg.FMIEndpoint, cfg.StationID, lastObs, obsEnd, cfg.ObsTimestep)
				data, err := weather.FetchData(url, cfg.HTTPTimeout)
				if err != nil {
					logger.Error("Failed to fetch observations", "error", err)
				} else {
					obs, maxT, err := weather.ParseObservations(data, cfg.StationID, lastObs)

					if err != nil {
						logger.Error("Failed to parse observations", "error", err)
					} else if len(obs) > 0 {
						// Publish observations
						successCount := 0
						for _, o := range obs {
							if err := publishObservation(mqttClient, o, logger); err != nil {
								logger.Error("Failed to publish observation", "error", err, "station", o.Station, "parameter", o.Parameter)
							} else {
								successCount++
							}
						}

						// Update watermark
						lastObs = maxT
						if err := storeWatermark(cfg.WatermarkFile, lastObs); err != nil {
							logger.Error("Failed to store watermark", "error", err)
						}

						logger.Info("Published observations",
							"successful", successCount,
							"total", len(obs),
							"new_watermark", lastObs)
					} else {
						logger.Debug("No new observations found")
					}
				}
			}
			obsTimer.Reset(cfg.ObsPollEvery)

		case <-fcTimer.C:
			// Poll forecast
			now := time.Now().UTC()
			start := now
			end := now.Add(48 * time.Hour)

			logger.Info("Polling forecast", "from", start, "to", end)

			url := weather.BuildForecastURL(cfg.FMIEndpoint, cfg.HelLat, cfg.HelLon, start, end)
			data, err := weather.FetchData(url, cfg.HTTPTimeout)
			if err != nil {
				logger.Error("Failed to fetch forecast", "error", err)
			} else {
				fc, runTime, err := weather.ParseForecast(data, cfg.HelLat, cfg.HelLon)

				if err != nil {
					logger.Error("Failed to parse forecast", "error", err)
				} else if len(fc) > 0 && (runTime.After(lastFcRun) || lastFcRun.IsZero()) {
					// Publish forecast
					successCount := 0
					for _, f := range fc {
						if err := publishForecast(mqttClient, f, logger); err != nil {
							logger.Error("Failed to publish forecast", "error", err, "parameter", f.Parameter)
						} else {
							successCount++
						}
					}

					lastFcRun = runTime
					logger.Info("Published forecast",
						"successful", successCount,
						"total", len(fc),
						"run_time", runTime)
				} else {
					logger.Debug("No new forecast data or same run time", "run_time", runTime, "last_run", lastFcRun)
				}
			}
			fcTimer.Reset(cfg.FcPollEvery)
		}
	}
}

func main() {
	cfg := loadPublisherConfig()

	// Setup logging
	logger := slog.New(slog.NewJSONHandler(os.Stdout, &slog.HandlerOptions{
		Level: parseLogLevel(cfg.LogLevel),
	}))

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

	// Setup signal handling
	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 publisher
	logger.Info("Starting weather data publisher with MQTT v5")
	if err := runPublisher(ctx, cfg, logger); err != nil {
		logger.Error("Publisher failed", "error", err)
		os.Exit(1)
	}

	logger.Info("Publisher stopped gracefully")
}

func parseLogLevel(level string) slog.Level {
	switch strings.ToLower(level) {
	case "debug":
		return slog.LevelDebug
	case "warn", "warning":
		return slog.LevelWarn
	case "error":
		return slog.LevelError
	default:
		return slog.LevelInfo
	}
}