package database

import (
	"database/sql"
	"fmt"
	"log"
	"os"
	"regexp"
	"time"

	_ "github.com/go-sql-driver/mysql"
)

var DB *sql.DB

func InitDB() error {

	if err := ensureDatabaseExists(); err != nil {
		return err
	}

	if err := connectToDatabase(); err != nil {
		return err
	}

	if err := ensureTablesExist(); err != nil {
		return err
	}

	log.Println("Database initialized successfully")
	return nil
}

func ensureDatabaseExists() error {
	dsn := getDSN("")

	db, err := sql.Open("mysql", dsn)
	if err != nil {
		return fmt.Errorf("failed to connect to database server: %w", err)
	}
	defer db.Close()

	// Get database name from environment
	dbName := os.Getenv("DB_NAME")

	// Check if database exists, create if not
	var exists bool
	err = db.QueryRow("SELECT EXISTS(SELECT 1 FROM information_schema.schemata WHERE schema_name = ?)", dbName).Scan(&exists)
	if err != nil {
		return fmt.Errorf("failed to check database existence: %w", err)
	}

	if !exists {
		if !isValidDatabaseName(dbName) {
			return fmt.Errorf("invalid database name: %s", dbName)
		}
		_, err = db.Exec("CREATE DATABASE `" + dbName + "` CHARACTER SET utf8mb4 COLLATE utf8mb4_unicode_ci")

		if err != nil {
			return fmt.Errorf("failed to create database: %w", err)
		}
	}

	return nil
}

func connectToDatabase() error {
	dsn := getDSN(os.Getenv("DB_NAME"))

	var err error
	DB, err = sql.Open("mysql", dsn)
	if err != nil {
		return fmt.Errorf("failed to connect to database: %w", err)
	}

	DB.SetMaxOpenConns(25)
	DB.SetMaxIdleConns(25)
	DB.SetConnMaxLifetime(5 * time.Minute)

	return nil
}

func ensureTablesExist() error {

	_, err := DB.Exec(`
        CREATE TABLE IF NOT EXISTS contacts (
            id INT AUTO_INCREMENT PRIMARY KEY,
            name VARCHAR(120) NOT NULL,
            company VARCHAR(120) NOT NULL,
            phone VARCHAR(15) NOT NULL
        ) DEFAULT CHARSET=utf8mb4 COLLATE=utf8mb4_unicode_ci;
    `)

	if err != nil {
		return fmt.Errorf("failed to create contacts table: %w", err)
	}

	return nil
}

func CloseDB() {
	if DB != nil {
		DB.Close()
	}
}

func getDSN(dbName string) string {
	user := os.Getenv("DB_USER")
	password := os.Getenv("DB_PASSWORD")
	host := os.Getenv("DB_HOST")
	port := os.Getenv("DB_PORT")

	dsn := fmt.Sprintf("%s:%s@tcp(%s:%s)/", user, password, host, port)
	if dbName != "" {
		dsn += dbName
	}
	dsn += "?parseTime=true&charset=utf8mb4&collation=utf8mb4_unicode_ci"

	return dsn
}

func isValidDatabaseName(name string) bool {
	matched, _ := regexp.MatchString(`^[a-zA-Z0-9_-]+$`, name)
	return matched && len(name) > 0 && len(name) <= 64
}