mama-dns-tool/internal/output/output.go

// Package output renders command results as a table or as JSON.
package output

import (
	"encoding/json"
	"fmt"
	"io"
	"strings"
	"text/tabwriter"
)

// Format is a rendering mode for command output.
type Format string

// Supported formats.
const (
	Table Format = "table"
	JSON  Format = "json"
)

// Parse validates a user-supplied format name.
func Parse(s string) (Format, error) {
	switch Format(strings.ToLower(strings.TrimSpace(s))) {
	case Table, "":
		return Table, nil
	case JSON:
		return JSON, nil
	default:
		return "", fmt.Errorf("unknown output format %q: use table or json", s)
	}
}

// Write renders v according to format. Table rendering uses header and rows so
// every command lays out the same way.
func Write(w io.Writer, format Format, header []string, rows [][]string, v any) error {
	if format == JSON {
		enc := json.NewEncoder(w)
		enc.SetIndent("", "  ")
		return enc.Encode(v)
	}
	if len(header) == 0 && len(rows) == 0 {
		return nil
	}
	tw := tabwriter.NewWriter(w, 0, 0, 2, ' ', 0)
	if len(header) > 0 {
		fmt.Fprintln(tw, strings.Join(header, "\t"))
	}
	for _, row := range rows {
		fmt.Fprintln(tw, strings.Join(row, "\t"))
	}
	return tw.Flush()
}