package database

import (
	domain "RenewCMS/internal/domain/update"
	"bufio"
	"os"
	"time"
)

const (
	dumpFileExtension        = ".sql"
	dumpPartialFileExtension = ".partial"
)

type DumpBackup struct {
	open      func() (DumpSource, error)
	directory string
	now       func() time.Time
	dialect   dumpDialect
}

var _ domain.DatabaseBackup = &DumpBackup{}

func NewDumpBackup(open func() (DumpSource, error), directory string, now func() time.Time) *DumpBackup {
	return &DumpBackup{open: open, directory: directory, now: now, dialect: mysqlDumpDialect}
}

func (b *DumpBackup) Backup() (string, error) {
	target, err := newBackupTarget(b.directory, b.now(), dumpFileExtension)
	if err != nil {
		return "", err
	}
	if err := b.writeAtomically(target); err != nil {
		return "", err
	}
	if err := pruneBackups(b.directory, dumpFileExtension); err != nil {
		return "", err
	}
	return target, nil
}

func (b *DumpBackup) writeAtomically(target string) error {
	partial := target + dumpPartialFileExtension
	if err := b.writePartial(partial); err != nil {
		_ = os.Remove(partial)
		return err
	}
	if err := os.Rename(partial, target); err != nil {
		_ = os.Remove(partial)
		return err
	}
	return nil
}

func (b *DumpBackup) writePartial(partial string) error {
	source, err := b.open()
	if err != nil {
		return err
	}
	defer source.Close()

	file, err := os.OpenFile(partial, os.O_WRONLY|os.O_CREATE|os.O_EXCL, 0o600)
	if err != nil {
		return err
	}
	buffered := bufio.NewWriter(file)
	if err := writeDump(buffered, source, b.dialect); err != nil {
		_ = file.Close()
		return err
	}
	if err := buffered.Flush(); err != nil {
		_ = file.Close()
		return err
	}
	if err := file.Sync(); err != nil {
		_ = file.Close()
		return err
	}
	return file.Close()
}