chore: expose tabwriter so InfluxDB can use it (#295)

pkg/tabwriter/tabwriter.go

@@ -0,0 +1,68 @@
+package tabwriter
+
+import (
+	"fmt"
+	"io"
+	"strings"
+	"text/tabwriter"
+)
+
+// TabWriter wraps tab writer headers logic.
+type TabWriter struct {
+	writer      *tabwriter.Writer
+	headers     []string
+	hideHeaders bool
+}
+
+// NewTabWriter creates a new tab writer.
+func NewTabWriter(w io.Writer, hideHeaders bool) *TabWriter {
+	return &TabWriter{
+		writer:      tabwriter.NewWriter(w, 0, 8, 1, '\t', 0),
+		hideHeaders: hideHeaders,
+	}
+}
+
+// WriteHeaders will Write headers.
+func (w *TabWriter) WriteHeaders(h ...string) error {
+	w.headers = h
+	if !w.hideHeaders {
+		if _, err := fmt.Fprintln(w.writer, strings.Join(h, "\t")); err != nil {
+			return err
+		}
+	}
+	return nil
+}
+
+// Write will Write the map into embed tab writer.
+func (w *TabWriter) Write(m map[string]interface{}) error {
+	body := make([]interface{}, len(w.headers))
+	types := make([]string, len(w.headers))
+	for i, h := range w.headers {
+		v := m[h]
+		body[i] = v
+		types[i] = formatStringType(v)
+	}
+	formatString := strings.Join(types, "\t")
+	if _, err := fmt.Fprintf(w.writer, formatString+"\n", body...); err != nil {
+		return err
+	}
+	return nil
+}
+
+// Flush should be called after the last call to Write to ensure
+// that any data buffered in the Writer is written to output. Any
+// incomplete escape sequence at the end is considered
+// complete for formatting purposes.
+func (w *TabWriter) Flush() error {
+	return w.writer.Flush()
+}
+
+func formatStringType(v interface{}) string {
+	switch v.(type) {
+	case int:
+		return "%d"
+	case string:
+		return "%s"
+	}
+	return "%v"
+}

pkg/tabwriter/tabwriter_test.go

@@ -0,0 +1,38 @@
+package tabwriter_test
+
+import (
+	"bytes"
+	"testing"
+
+	"github.com/influxdata/influx-cli/v2/pkg/tabwriter"
+	"github.com/stretchr/testify/require"
+)
+
+func Test_WriteHeaders(t *testing.T) {
+	out := bytes.Buffer{}
+	w := tabwriter.NewTabWriter(&out, false)
+	require.NoError(t, w.WriteHeaders("foo", "bar", "baz"))
+	require.NoError(t, w.Flush())
+	require.Equal(t, "foo\tbar\tbaz\n", out.String())
+}
+
+func Test_WriteHeadersDisabled(t *testing.T) {
+	out := bytes.Buffer{}
+	w := tabwriter.NewTabWriter(&out, true)
+	require.NoError(t, w.WriteHeaders("foo", "bar", "baz"))
+	require.NoError(t, w.Flush())
+	require.Empty(t, out.String())
+}
+
+func Test_Write(t *testing.T) {
+	out := bytes.Buffer{}
+	w := tabwriter.NewTabWriter(&out, true)
+	require.NoError(t, w.WriteHeaders("foo", "bar", "baz"))
+	require.NoError(t, w.Write(map[string]interface{}{
+		"bar": 123,
+		"foo": "a string!",
+		"baz": false,
+	}))
+	require.NoError(t, w.Flush())
+	require.Equal(t, "a string!\t123\tfalse\n", out.String())
+}