package database

import (
	"billit/internal/models"
	"context"
	"database/sql"
	"fmt"
	"log"
	"os"
	"strconv"
	"time"

	_ "github.com/mattn/go-sqlite3"
)

// Service represents the database service interface
type Service interface {
	// Health returns database health status
	Health() map[string]string

	// Close closes the database connection
	Close() error

	// Buyer methods
	CreateBuyerDetails(userID string, name string, details string) (*models.BuyerDetails, error)
	UpdateBuyerDetails(id string, userID string, name string, details string) error
	GetBuyerDetails(id string, userID string) (*models.BuyerDetails, error)
	GetAllBuyerDetails(userID string) ([]models.BuyerDetails, error)
	DeleteBuyerDetails(id string, userID string) error

	// User methods
	CreateUser(email, passwordHash string) (*models.User, error)
	GetUserByEmail(email string) (*models.User, error)
	GetUserByID(id string) (*models.User, error)
	UpdateUserPassword(id string, passwordHash string) error
	UpdateUserDetails(id string, companyDetails string, bankDetails string, invoicePrefix string) error

	// Invoice methods
	GetNextInvoiceNumber(userID string) (string, error)
	CreateInvoice(id string, humanReadableID string, data interface{}, userID string) error
	GetInvoice(id string, userID string) (*models.Invoice, error)
	GetAllInvoices(userID string) ([]models.Invoice, error)
	GetRecentInvoices(userID string, limit int) ([]models.Invoice, error)

	// Product methods
	CreateProduct(p models.Product, userID string) error
	UpdateProduct(p models.Product, userID string) error
	GetAllProducts(userID string) ([]models.Product, error)
	GetProductBySKU(sku string, userID string) (*models.Product, error)
	DeleteProduct(sku string, userID string) error
	GetRecentProducts(userID string, limit int) ([]models.Product, error)
}

type service struct {
	db *sql.DB
}

var dbInstance *service

// New creates a new database service
func New() Service {
	// Reuse connection if already established
	if dbInstance != nil {
		return dbInstance
	}

	dbPath := os.Getenv("DB_PATH")
	if dbPath == "" {
		dbPath = "./db/dev.db"
	}

	db, err := sql.Open("sqlite3", dbPath)
	if err != nil {
		log.Fatal(err)
	}

	// Check connection
	if err := db.Ping(); err != nil {
		log.Fatal("Could not ping database:", err)
	}

	dbInstance = &service{
		db: db,
	}

	return dbInstance
}

// Health checks the health of the database connection
func (s *service) Health() map[string]string {
	ctx, cancel := context.WithTimeout(context.Background(), 1*time.Second)
	defer cancel()

	stats := make(map[string]string)

	// Ping the database
	err := s.db.PingContext(ctx)
	if err != nil {
		stats["status"] = "down"
		stats["error"] = fmt.Sprintf("db down: %v", err)
		log.Printf("db down: %v", err)
		return stats
	}

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

	// Get database stats
	dbStats := s.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)

	if dbStats.OpenConnections > 40 {
		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 connection usage."
	}

	return stats
}

// Close closes the database connection
func (s *service) Close() error {
	return s.db.Close()
}