package main

import (
	"context"
	"encoding/json"
	"fmt"
	"log/slog"
	"net/http"
	"os"
	"os/signal"
	"syscall"
	"time"

	"github.com/jackc/pgx/v5/pgxpool"
	"github.com/scottyah/paragliding/internal/client"
	"github.com/scottyah/paragliding/internal/config"
	"github.com/scottyah/paragliding/internal/database"
	"github.com/scottyah/paragliding/internal/model"
	"github.com/scottyah/paragliding/internal/repository"
	"github.com/scottyah/paragliding/internal/server"
	"github.com/scottyah/paragliding/internal/service"
)

func main() {
	// Setup structured logging
	logger := slog.New(slog.NewJSONHandler(os.Stdout, &slog.HandlerOptions{
		Level: slog.LevelInfo,
	}))
	slog.SetDefault(logger)

	// Load configuration
	cfg, err := config.Load()
	if err != nil {
		logger.Error("failed to load configuration", "error", err)
		os.Exit(1)
	}

	logger.Info("configuration loaded",
		"port", cfg.Port,
		"location", cfg.LocationName,
		"fetch_interval", cfg.FetchInterval,
	)

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

	// Connect to PostgreSQL with retry
	dbpool, err := connectDatabaseWithRetry(ctx, cfg.DatabaseURL, logger, 30*time.Second)
	if err != nil {
		logger.Error("failed to connect to database", "error", err)
		os.Exit(1)
	}
	defer dbpool.Close()

	logger.Info("connected to database")

	// Run database migrations
	if err := database.RunMigrations(cfg.DatabaseURL, logger); err != nil {
		logger.Error("failed to run migrations", "error", err)
		os.Exit(1)
	}

	// Initialize services
	weatherClient := client.NewOpenMeteoClient(client.OpenMeteoConfig{
		Latitude:  cfg.LocationLat,
		Longitude: cfg.LocationLon,
		Timezone:  cfg.Timezone,
	})

	weatherRepo := repository.NewWeatherRepository(dbpool)
	assessmentSvc := service.NewAssessmentService()

	// Create weather service (handles caching and API rate limiting)
	weatherSvc := service.NewWeatherService(service.WeatherServiceConfig{
		Client: weatherClient,
		Repo:   weatherRepo,
		Logger: logger,
	})

	// Create HTTP server
	srv := server.New(cfg.Addr(), logger)

	// Setup routes with handler
	handler := &Handler{
		logger:        logger,
		db:            dbpool,
		config:        cfg,
		weatherSvc:    weatherSvc,
		assessmentSvc: assessmentSvc,
	}
	srv.SetupRoutes(handler)

	// Start background weather fetcher
	fetcher := &WeatherFetcher{
		logger:     logger,
		config:     cfg,
		weatherSvc: weatherSvc,
		stopChan:   make(chan struct{}),
	}
	go fetcher.Start(ctx)

	// Start HTTP server in a goroutine
	serverErrors := make(chan error, 1)
	go func() {
		serverErrors <- srv.Start()
	}()

	// Wait for interrupt signal or server error
	shutdown := make(chan os.Signal, 1)
	signal.Notify(shutdown, os.Interrupt, syscall.SIGTERM)

	select {
	case err := <-serverErrors:
		logger.Error("server error", "error", err)
	case sig := <-shutdown:
		logger.Info("shutdown signal received", "signal", sig)

		// Stop background fetcher
		close(fetcher.stopChan)

		// Give outstanding requests time to complete
		ctx, cancel := context.WithTimeout(context.Background(), 15*time.Second)
		defer cancel()

		if err := srv.Shutdown(ctx); err != nil {
			logger.Error("graceful shutdown failed", "error", err)
			os.Exit(1)
		}

		logger.Info("server stopped gracefully")
	}
}

// connectDatabaseWithRetry establishes a connection pool to PostgreSQL with exponential backoff
func connectDatabaseWithRetry(ctx context.Context, databaseURL string, logger *slog.Logger, maxWait time.Duration) (*pgxpool.Pool, error) {
	pgConfig, err := pgxpool.ParseConfig(databaseURL)
	if err != nil {
		return nil, fmt.Errorf("failed to parse database URL: %w", err)
	}

	// Set connection pool settings
	pgConfig.MaxConns = 25
	pgConfig.MinConns = 5
	pgConfig.MaxConnLifetime = time.Hour
	pgConfig.MaxConnIdleTime = 30 * time.Minute
	pgConfig.HealthCheckPeriod = time.Minute

	// Exponential backoff retry
	var pool *pgxpool.Pool
	backoff := 1 * time.Second
	maxBackoff := 8 * time.Second
	deadline := time.Now().Add(maxWait)

	for {
		pool, err = pgxpool.NewWithConfig(ctx, pgConfig)
		if err == nil {
			// Verify connection
			if pingErr := pool.Ping(ctx); pingErr == nil {
				return pool, nil
			} else {
				pool.Close()
				err = pingErr
			}
		}

		if time.Now().After(deadline) {
			return nil, fmt.Errorf("failed to connect to database after %v: %w", maxWait, err)
		}

		logger.Warn("database connection failed, retrying",
			"error", err,
			"retry_in", backoff,
		)

		select {
		case <-ctx.Done():
			return nil, ctx.Err()
		case <-time.After(backoff):
		}

		// Exponential backoff with cap
		backoff *= 2
		if backoff > maxBackoff {
			backoff = maxBackoff
		}
	}
}

// Handler implements the RouteHandler interface
type Handler struct {
	logger        *slog.Logger
	db            *pgxpool.Pool
	config        *config.Config
	weatherSvc    *service.WeatherService
	assessmentSvc *service.AssessmentService
}

// Health handles health check requests
func (h *Handler) Health(w http.ResponseWriter, r *http.Request) {
	ctx, cancel := context.WithTimeout(r.Context(), 5*time.Second)
	defer cancel()

	// Check database connectivity
	if err := h.db.Ping(ctx); err != nil {
		h.logger.Error("health check failed", "error", err)
		server.RespondError(w, 503, "database unavailable")
		return
	}

	server.RespondJSON(w, 200, map[string]interface{}{
		"status":    "healthy",
		"timestamp": time.Now().UTC(),
		"location":  h.config.LocationName,
	})
}

// GetCurrentWeather handles current weather requests
func (h *Handler) GetCurrentWeather(w http.ResponseWriter, r *http.Request) {
	ctx := r.Context()

	// Get current weather from service (handles caching, DB, and rate-limited API fallback)
	weatherData, err := h.weatherSvc.GetCurrentWeather(ctx)
	if err != nil {
		h.logger.Error("failed to get current weather", "error", err)
		server.RespondError(w, 500, "failed to fetch weather data")
		return
	}

	if len(weatherData.Points) == 0 {
		server.RespondError(w, 500, "no current weather data available")
		return
	}

	current := weatherData.Points[0]

	// Get all points for assessment
	allPoints, err := h.weatherSvc.GetAllPoints(ctx)
	if err != nil {
		h.logger.Warn("failed to get points for assessment", "error", err)
		allPoints = weatherData.Points
	}

	// Get default thresholds and assess conditions
	thresholds := model.DefaultThresholds()
	assessment := h.assessmentSvc.Evaluate(allPoints, thresholds)

	response := map[string]interface{}{
		"timestamp": weatherData.FetchedAt.UTC(),
		"location": map[string]interface{}{
			"name": h.config.LocationName,
			"lat":  h.config.LocationLat,
			"lon":  h.config.LocationLon,
		},
		"current": map[string]interface{}{
			"windSpeed":     current.WindSpeedMPH,
			"windDirection": current.WindDirection,
			"windGust":      current.WindGustMPH,
			"time":          current.Time,
		},
		"assessment": assessment,
		"source":     weatherData.Source,
	}

	server.RespondJSON(w, 200, response)
}

// GetForecast handles weather forecast requests
func (h *Handler) GetForecast(w http.ResponseWriter, r *http.Request) {
	ctx := r.Context()

	// Get forecast from service (handles caching, DB, and rate-limited API fallback)
	weatherData, err := h.weatherSvc.GetForecast(ctx)
	if err != nil {
		h.logger.Error("failed to get forecast", "error", err)
		server.RespondError(w, 500, "failed to fetch forecast data")
		return
	}

	// Get default thresholds
	thresholds := model.DefaultThresholds()

	// Find flyable windows
	windows := h.assessmentSvc.FindFlyableWindows(weatherData.Points, thresholds)

	response := map[string]interface{}{
		"generated": weatherData.FetchedAt.UTC(),
		"location": map[string]interface{}{
			"name": h.config.LocationName,
			"lat":  h.config.LocationLat,
			"lon":  h.config.LocationLon,
		},
		"forecast":          weatherData.Points,
		"flyableWindows":    windows,
		"defaultThresholds": thresholds,
		"source":            weatherData.Source,
	}

	server.RespondJSON(w, 200, response)
}

// GetHistorical handles historical weather requests
func (h *Handler) GetHistorical(w http.ResponseWriter, r *http.Request) {
	ctx := r.Context()

	// Parse date from query param (default: yesterday)
	dateStr := r.URL.Query().Get("date")
	var date time.Time
	if dateStr == "" {
		date = time.Now().AddDate(0, 0, -1)
	} else {
		var err error
		date, err = time.Parse("2006-01-02", dateStr)
		if err != nil {
			server.RespondError(w, 400, "invalid date format, use YYYY-MM-DD")
			return
		}
	}

	// Get historical data from service (handles caching and DB lookup)
	weatherData, err := h.weatherSvc.GetHistorical(ctx, date)
	if err != nil {
		h.logger.Error("failed to get historical data", "error", err)
		server.RespondError(w, 500, "failed to fetch historical data")
		return
	}

	response := map[string]interface{}{
		"date":   date.Format("2006-01-02"),
		"data":   weatherData.Points,
		"source": weatherData.Source,
	}

	server.RespondJSON(w, 200, response)
}

// AssessConditions handles paragliding condition assessment requests
func (h *Handler) AssessConditions(w http.ResponseWriter, r *http.Request) {
	ctx := r.Context()

	// Limit request body size
	r.Body = http.MaxBytesReader(w, r.Body, 1<<20) // 1MB max

	// Parse thresholds from request body
	var req struct {
		Thresholds model.Thresholds `json:"thresholds"`
	}
	if err := json.NewDecoder(r.Body).Decode(&req); err != nil {
		// Use default thresholds if not provided or invalid
		req.Thresholds = model.DefaultThresholds()
	}

	// Get weather data from service (DB-first, no API call triggered here)
	points, err := h.weatherSvc.GetAllPoints(ctx)
	if err != nil {
		h.logger.Error("failed to get weather for assessment", "error", err)
		server.RespondError(w, 500, "failed to fetch weather data")
		return
	}

	// Run assessment with provided thresholds
	assessment := h.assessmentSvc.Evaluate(points, req.Thresholds)
	windows := h.assessmentSvc.FindFlyableWindows(points, req.Thresholds)

	response := map[string]interface{}{
		"assessment":     assessment,
		"flyableWindows": windows,
		"thresholds":     req.Thresholds,
	}

	server.RespondJSON(w, 200, response)
}

// WeatherFetcher runs background weather fetching
type WeatherFetcher struct {
	logger     *slog.Logger
	config     *config.Config
	weatherSvc *service.WeatherService
	stopChan   chan struct{}
}

// Start begins the background weather fetching loop
func (f *WeatherFetcher) Start(ctx context.Context) {
	f.logger.Info("starting weather fetcher", "interval", f.config.FetchInterval)

	ticker := time.NewTicker(f.config.FetchInterval)
	defer ticker.Stop()

	// Fetch immediately on startup
	f.fetch(ctx)

	for {
		select {
		case <-ticker.C:
			f.fetch(ctx)
		case <-f.stopChan:
			f.logger.Info("stopping weather fetcher")
			return
		case <-ctx.Done():
			f.logger.Info("weather fetcher context cancelled")
			return
		}
	}
}

// fetch performs the actual weather data fetching via the weather service
func (f *WeatherFetcher) fetch(ctx context.Context) {
	f.logger.Info("fetching weather data",
		"lat", f.config.LocationLat,
		"lon", f.config.LocationLon,
	)

	// Use weather service's FetchFromAPI (bypasses rate limiting for scheduled fetches)
	points, err := f.weatherSvc.FetchFromAPI(ctx)
	if err != nil {
		f.logger.Error("failed to fetch weather data", "error", err)
		return
	}

	f.logger.Info("weather data updated successfully", "points", len(points))
}