package log

import (
	"io"
	"sync"
)

type WriteLocker interface {
	io.Writer
	sync.Locker
}

type writeLock struct {
	sync.Mutex
	io.Writer
}

// Lock wraps a WriteSyncer in a mutex to make it safe for concurrent use. In
// particular, *os.Files must be locked before use.
//
// If w is already a WriteLocker, it will be returned as is.
func Lock(w io.Writer) WriteLocker {
	if wl, ok := w.(WriteLocker); ok {
		// no need to layer on another lock
		return wl
	}
	return &writeLock{Writer: w}
}