// allGCPPrinters calls gcp.List, then calls gcp.Printer, one goroutine per
// printer. This is a fast way to fetch all printers with corresponding CDD
// info, which the List API does not provide.
//
// The second return value is a map of GCPID -> queued print job quantity.
func allGCPPrinters(gcp *gcp.GoogleCloudPrint) ([]lib.Printer, map[string]uint, error) {
ids, err := gcp.List()
if err != nil {
return nil, nil, err
}
type response struct {
printer *lib.Printer
queuedJobsCount uint
err error
}
ch := make(chan response)
for id := range ids {
go func(id string) {
printer, queuedJobsCount, err := gcp.Printer(id)
ch <- response{printer, queuedJobsCount, err}
}(id)
}
errs := make([]error, 0)
printers := make([]lib.Printer, 0, len(ids))
queuedJobsCount := make(map[string]uint)
for _ = range ids {
r := <-ch
if r.err != nil {
errs = append(errs, r.err)
continue
}
printers = append(printers, *r.printer)
if r.queuedJobsCount > 0 {
queuedJobsCount[r.printer.GCPID] = r.queuedJobsCount
}
}
if len(errs) == 0 {
return printers, queuedJobsCount, nil
} else if len(errs) == 1 {
return nil, nil, errs[0]
} else {
// Return an error that is somewhat human-readable.
b := bytes.NewBufferString(fmt.Sprintf("%d errors: ", len(errs)))
for i, err := range errs {
if i > 0 {
b.WriteString(", ")
}
b.WriteString(err.Error())
}
return nil, nil, errors.New(b.String())
}
}
