package session

import (
	"errors"
	"log"
)

var errTransactionNotStartedYet = errors.New("worm: transaction is not started yet")

var (
	_DEBUG_TRANSACTION_BEGIN    = "[DEBUG] [worm] [sid-%d] Begin transaction."
	_DEBUG_TRANSACTION_COMMIT   = "[DEBUG] [worm] [sid-%d] Commit transaction."
	_DEBUG_TRANSACTION_ROLLBACK = "[DEBUG] [worm] [sid-%d] Rollback transaction."
)

// Begin 开始事务
func (own *Session) Begin() (err error) {
	if own.debug {
		log.Printf(_DEBUG_TRANSACTION_BEGIN, own.id)
	}

	own.tx, err = own.db.Begin()
	return err
}

// Commit 提交事务
func (own *Session) Commit() (err error) {
	if own.tx == nil {
		return errTransactionNotStartedYet
	}

	if own.debug {
		log.Printf(_DEBUG_TRANSACTION_COMMIT, own.id)
	}

	if err = own.tx.Commit(); err == nil {
		own.tx = nil
	}

	return
}

// Rollback 回滚事务
func (own *Session) Rollback() (err error) {
	if own.tx == nil {
		return errTransactionNotStartedYet
	}

	if own.debug {
		log.Printf(_DEBUG_TRANSACTION_ROLLBACK, own.id)
	}

	if err = own.tx.Rollback(); err == nil {
		own.tx = nil
	}

	return
}