package mysql

import (
	"errors"
	"fmt"

	"gorm.io/gorm"
	"zestack.dev/env"
)

func PublicDatabase() string {
	return env.String("DB_NAME")
}

func TenantBasename() string {
	return env.String("TENANT_BASENAME", "tenant_")
}

func TenantDatabase(tenant uint) string {
	if tenant == 0 {
		return PublicDatabase()
	}
	return fmt.Sprintf("%s%d", TenantBasename(), tenant)
}

func UseDatabase(tx *gorm.DB, database string) (reset func() error, err error) {
	if database == "" {
		err = errors.New("database name is empty")
		tx.AddError(err)
		return
	}

	if database == CurrentDatabase(tx) {
		reset = func() error { return nil }
		return
	}

	sql := "USE " + tx.Statement.Quote(database)
	if execErr := tx.Exec(sql).Error; execErr != nil {
		err = fmt.Errorf("failed to set database %q: %w", database, execErr)
		tx.AddError(err)
		return
	}

	reset = func() error {
		publicDatabase := PublicDatabase()
		if database == publicDatabase {
			return nil
		}
		return tx.Exec("USE " + tx.Statement.Quote(publicDatabase)).Error
	}

	return
}

func CurrentDatabase(tx *gorm.DB) string {
	var database string
	tx.Raw("SELECT DATABASE()").Row().Scan(&database)
	return database
}