feat: port stacks command from influxdb (#168)

pkg/template/out.go

@@ -0,0 +1,63 @@
+package template
+
+import (
+	"encoding/json"
+	"fmt"
+	"io"
+	"os"
+	"path/filepath"
+
+	"github.com/influxdata/influx-cli/v2/api"
+	"gopkg.in/yaml.v3"
+)
+
+type OutEncoding int
+
+const (
+	YamlEncoding OutEncoding = iota
+	JsonEncoding
+)
+
+type OutParams struct {
+	Out      io.Writer
+	Encoding OutEncoding
+}
+
+func ParseOutParams(path string, fallback io.Writer) (OutParams, func(), error) {
+	if path == "" {
+		return OutParams{Out: fallback, Encoding: YamlEncoding}, nil, nil
+	}
+
+	f, err := os.OpenFile(path, os.O_WRONLY|os.O_CREATE|os.O_TRUNC, 0600)
+	if err != nil {
+		return OutParams{}, nil, fmt.Errorf("failed to open output path %q: %w", path, err)
+	}
+	params := OutParams{Out: f}
+	switch filepath.Ext(path) {
+	case ".json":
+		params.Encoding = JsonEncoding
+	default:
+		params.Encoding = YamlEncoding
+	}
+
+	return params, func() { _ = f.Close() }, nil
+}
+
+func (o OutParams) WriteTemplate(template []api.TemplateEntry) error {
+	switch o.Encoding {
+	case JsonEncoding:
+		enc := json.NewEncoder(o.Out)
+		enc.SetIndent("", "\t")
+		return enc.Encode(template)
+	case YamlEncoding:
+		enc := yaml.NewEncoder(o.Out)
+		for _, entry := range template {
+			if err := enc.Encode(entry); err != nil {
+				return err
+			}
+		}
+	default:
+		return fmt.Errorf("encoding %q is not recognized", o.Encoding)
+	}
+	return nil
+}