package main

import (
  "context"
  "database/sql"
  "fmt"
  "sync"
  "time"
   "io/ioutil"

  _ "github.com/jackc/pgx/v5/stdlib"
)

type DBManager struct {
  db       *sql.DB
  lock     sync.Mutex
  password string
}

func NewDBManager() *DBManager {
  password := getPasswordFromSecretStore()
  db, err := connectDB(password)
  if err != nil {
    panic(fmt.Sprintf("Failed to connect to DB: %v", err))
  }

  manager := &DBManager{
    db:       db,
    password: password,
  }

  go manager.watchPasswordChanges()

  return manager
}

func connectDB(password string) (*sql.DB, error) {
  dsn := fmt.Sprintf("postgres://myuser:%s@localhost:5432/postgres?sslmode=disable", password)
  return sql.Open("pgx", dsn)
}

func (m *DBManager) watchPasswordChanges() {
  for {
    time.Sleep(1 * time.Second)
    newPassword := getPasswordFromSecretStore()
    if newPassword != m.password {
      fmt.Println("Password changed, reconnecting...")
      m.reconnect(newPassword)
    }
  }
}

func (m *DBManager) reconnect(newPassword string) {
  m.lock.Lock()
  defer m.lock.Unlock()

  db, err := connectDB(newPassword)
  if err != nil {
    fmt.Println("Failed to reconnect to DB:", err)
    return
  }

  oldDB := m.db
  m.db = db
  m.password = newPassword

  if oldDB != nil {
    oldDB.Close()
  }
}

func getPasswordFromSecretStore() string {
        content, err := ioutil.ReadFile("mysecret") // /var/run/secrets/credentials - пример пути в поде
  if err != nil {
                panic(err) // Не делайте так в проде)
  }

  text := string(content)
        return text
}

func main() {
  manager := NewDBManager()

  ctx := context.Background()
  for {
    var now time.Time
    if err := manager.db.QueryRowContext(ctx, "SELECT NOW()").Scan(&now); err != nil {
      fmt.Println("Query failed:", err)
    } else {
      fmt.Println("DB time:", now)
    }
    time.Sleep(time.Second)
  }
}