package utils
 
 import (
 	"io"
 	"net"
 	"os"
 	"syscall"
 
 	"github.com/docker/docker/pkg/progress"
 	"github.com/docker/docker/pkg/streamformatter"

 	"github.com/sirupsen/logrus"

 )
 
 // WriteDistributionProgress is a helper for writing progress from chan to JSON
 // stream with an optional cancel function.
 func WriteDistributionProgress(cancelFunc func(), outStream io.Writer, progressChan <-chan progress.Progress) {

 	progressOutput := streamformatter.NewJSONProgressOutput(outStream, false)

 	operationCancelled := false
 
 	for prog := range progressChan {
 		if err := progressOutput.WriteProgress(prog); err != nil && !operationCancelled {
 			// don't log broken pipe errors as this is the normal case when a client aborts
 			if isBrokenPipe(err) {
 				logrus.Info("Pull session cancelled")
 			} else {
 				logrus.Errorf("error writing progress to client: %v", err)
 			}
 			cancelFunc()
 			operationCancelled = true
 			// Don't return, because we need to continue draining
 			// progressChan until it's closed to avoid a deadlock.
 		}
 	}
 }
 
 func isBrokenPipe(e error) bool {
 	if netErr, ok := e.(*net.OpError); ok {
 		e = netErr.Err
 		if sysErr, ok := netErr.Err.(*os.SyscallError); ok {
 			e = sysErr.Err
 		}
 	}
 	return e == syscall.EPIPE
 }