package database

import (
	"context"
	"fmt"
	"log"
	"os"
	"strconv"
	"time"

	_ "github.com/jackc/pgx/v5/stdlib"
	_ "github.com/joho/godotenv/autoload"
	"gorm.io/driver/postgres"
	"gorm.io/gorm"
)

type Service interface {
	Health() map[string]string
	Close() error
	GetDB() *gorm.DB
}

type service struct {
	db *gorm.DB
}

var (
	hostSimrs     = os.Getenv("POSTGRE_DB_HOST")
	userNameSimrs = os.Getenv("POSTGRE_DB_USER")
	passwordSimrs = os.Getenv("POSTGRE_DB_PASS")
	dbNameSimrs   = os.Getenv("POSTGRE_DB_NAME")
	portSimrs     = os.Getenv("POSTGRE_DB_PORT")
	dbInstance    *service
)

func New() Service {
	// Reuse Connection
	if dbInstance != nil {
		return dbInstance
	}
	simrs := fmt.Sprintf("host=%s user=%s password=%s dbname=%s port=%s sslmode=disable TimeZone=Asia/Jakarta", hostSimrs, userNameSimrs, passwordSimrs, dbNameSimrs, portSimrs)

	SimrsDB, err := gorm.Open(postgres.Open(simrs), &gorm.Config{})
	if err != nil {
		log.Fatal("Failed to connect to SIM database: ", err)
	} else {
		log.Println("Successfully connected to the database")
	}
	dbInstance = &service{
		db: SimrsDB,
	}
	return dbInstance
}

// Health checks the health of the database connection by pinging the database.
// It returns a map with keys indicating various health statistics.
func (s *service) Health() map[string]string {
	ctx, cancel := context.WithTimeout(context.Background(), 10*time.Second)
	defer cancel()

	stats := make(map[string]string)

	// Ping the database using GORM
	db, err := s.db.DB() // Retrieve the underlying sql.DB instance from GORM
	if err != nil {
		stats["status"] = "down"
		stats["error"] = fmt.Sprintf("failed to get sql.DB from GORM: %v", err)
		log.Fatalf("failed to get sql.DB from GORM: %v", err) // Log the error and terminate the program
		return stats
	}

	err = db.PingContext(ctx)
	if err != nil {
		stats["status"] = "down"
		stats["error"] = fmt.Sprintf("db down: %v", err)
		log.Fatalf("db down: %v", err) // Log the error and terminate the program
		return stats
	}

	// Database is up, add more statistics
	stats["status"] = "up"
	stats["message"] = "It's healthy"

	// Get database stats
	dbStats := db.Stats()
	stats["open_connections"] = strconv.Itoa(dbStats.OpenConnections)
	stats["in_use"] = strconv.Itoa(dbStats.InUse)
	stats["idle"] = strconv.Itoa(dbStats.Idle)
	stats["wait_count"] = strconv.FormatInt(dbStats.WaitCount, 10)
	stats["wait_duration"] = dbStats.WaitDuration.String()
	stats["max_idle_closed"] = strconv.FormatInt(dbStats.MaxIdleClosed, 10)
	stats["max_lifetime_closed"] = strconv.FormatInt(dbStats.MaxLifetimeClosed, 10)

	// Evaluate stats to provide a health message
	if dbStats.OpenConnections > 40 { // Assuming 50 is the max for this example
		stats["message"] = "The database is experiencing heavy load."
	}

	if dbStats.WaitCount > 1000 {
		stats["message"] = "The database has a high number of wait events, indicating potential bottlenecks."
	}

	if dbStats.MaxIdleClosed > int64(dbStats.OpenConnections)/2 {
		stats["message"] = "Many idle connections are being closed, consider revising the connection pool settings."
	}

	if dbStats.MaxLifetimeClosed > int64(dbStats.OpenConnections)/2 {
		stats["message"] = "Many connections are being closed due to max lifetime, consider increasing max lifetime or revising the connection usage pattern."
	}

	return stats
}

// Close closes the database connection.
// It logs a message indicating the disconnection from the specific database.
// If the connection is successfully closed, it returns nil.
// If an error occurs while closing the connection, it returns the error.
func (s *service) Close() error {
	db, err := s.db.DB() // Retrieve the underlying sql.DB instance from GORM
	if err != nil {
		log.Printf("Failed to retrieve sql.DB from GORM: %v", err)
		return err
	}

	err = db.Close()
	if err != nil {
		log.Printf("Error closing the database connection: %v", err)
		return err
	}

	log.Printf("Disconnected from database successfully")
	return nil
}

func (s *service) GetDB() *gorm.DB {
	return s.db
}