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// Package print provides helpers for structured output printing.
package print
import (
"fmt"
"io"
"strings"
"text/tabwriter"
)
// DefaultIndent is the default string for one level of indentation.
const DefaultIndent = "\t"
// Printer provides convenience methods for structured output printing.
// Specifically it stores any errors encountered so error checking does not have
// to be done on every print call. Also provides helpers for managing indentation.
type Printer struct {
out io.Writer
level int // current indentation level
indent string // indentation string
pending bool // if there's a pending indentation
err error // saved error from printing
}
// New builds a printer writing to w.
func New(w io.Writer) Printer {
return Printer{
out: w,
indent: DefaultIndent,
}
}
// SetIndentString configures the string used for one level of indentation.
func (p *Printer) SetIndentString(indent string) {
p.indent = indent
}
// Indent by one level.
func (p *Printer) Indent() {
p.level++
}
// Dedent by one level.
func (p *Printer) Dedent() {
p.level--
}
// Linef prints a formatted line.
func (p *Printer) Linef(format string, args ...interface{}) {
p.Printf(format, args...)
p.NL()
}
// NL prints a newline.
func (p *Printer) NL() {
p.Printf("\n")
p.pending = true
}
// Printf prints formatted output.
func (p *Printer) Printf(format string, args ...interface{}) {
if p.err != nil {
return
}
if p.pending {
indent := strings.Repeat(p.indent, p.level)
format = indent + format
p.pending = false
}
_, err := fmt.Fprintf(p.out, format, args...)
p.SetError(err)
}
// Error returns the first error that occurred so far, if any.
func (p *Printer) Error() error {
return p.err
}
// SetError records a possible error.
func (p *Printer) SetError(err error) {
if p.err == nil {
p.err = err
}
}
// TabWriter provides tabwriter.Writer functionality with the Printer interface.
type TabWriter struct {
tw *tabwriter.Writer
Printer
}
// NewTabWriter builds a TabWriter. Arguments are the same as for tabwriter.NewWriter.
func NewTabWriter(w io.Writer, minwidth, tabwidth, padding int, padchar byte, flags uint) *TabWriter {
tw := tabwriter.NewWriter(w, minwidth, tabwidth, padding, padchar, flags)
return &TabWriter{
tw: tw,
Printer: New(tw),
}
}
// Flush the tabwriter.
func (p *TabWriter) Flush() {
p.SetError(p.tw.Flush())
}
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