Kando command for creating phase output (#4021)

* Kando command for creating phase output

* Fix typo

* Minor improvements

pkg/kando/kando.go

@@ -27,5 +27,6 @@ func newRootCommand() *cobra.Command {
 		Version: version.VersionString(),
 	}
 	rootCmd.AddCommand(newLocationCommand())
+	rootCmd.AddCommand(newOutputCommand())
 	return rootCmd
 }

pkg/kando/output.go

@@ -0,0 +1,34 @@
+package kando
+
+import (
+	"github.com/pkg/errors"
+	"github.com/spf13/cobra"
+
+	"github.com/kanisterio/kanister/pkg/output"
+)
+
+func newOutputCommand() *cobra.Command {
+	cmd := &cobra.Command{
+		Use:   "output <key> <value>",
+		Short: "Create phase output with given key:value",
+		Args: func(c *cobra.Command, args []string) error {
+			return validateArguments(c, args)
+		},
+		// TODO: Example invocations
+		RunE: func(c *cobra.Command, args []string) error {
+			return runOutputCommand(c, args)
+		},
+	}
+	return cmd
+}
+
+func validateArguments(c *cobra.Command, args []string) error {
+	if err := cobra.ExactArgs(2); err != nil {
+		return errors.New("Command requires exactly two arguments")
+	}
+	return output.ValidateKey(args[0])
+}
+
+func runOutputCommand(c *cobra.Command, args []string) error {
+	return output.PrintOutput(args[0], args[1])
+}

pkg/output/output.go

@@ -0,0 +1,54 @@
+package output
+
+import (
+	"encoding/json"
+	"fmt"
+	"regexp"
+
+	"github.com/pkg/errors"
+)
+
+const (
+	phaseOpString = "###Phase-output###:"
+)
+
+type Output struct {
+	Key   string `json:"key"`
+	Value string `json:"value"`
+}
+
+func marshalOutput(key, value string) (string, error) {
+	out := &Output{
+		Key:   key,
+		Value: value,
+	}
+	outString, err := json.Marshal(out)
+	if err != nil {
+		return "", errors.Wrapf(err, "Failed to marshall key-value pair")
+	}
+	return string(outString), nil
+}
+
+// ValidateKey validates the key argument
+func ValidateKey(key string) error {
+	// key should be non-empty
+	if key == "" {
+		return errors.New("Key should not be empty")
+	}
+	// key can contain only alpha numeric characters and underscore
+	valid := regexp.MustCompile("^[a-zA-Z0-9_]*$").MatchString
+	if !valid(key) {
+		return errors.New("Key should contain only alphanumeric characters and underscore")
+	}
+	return nil
+}
+
+// PrintOutput runs the `kando output` command
+func PrintOutput(key, value string) error {
+	outString, err := marshalOutput(key, value)
+	if err != nil {
+		return err
+	}
+	fmt.Println(phaseOpString, outString)
+	return nil
+}

pkg/output/output_test.go

@@ -0,0 +1,31 @@
+package output
+
+import (
+	"testing"
+
+	. "gopkg.in/check.v1"
+)
+
+// Hook up gocheck into the "go test" runner.
+func Test(t *testing.T) { TestingT(t) }
+
+type OutputSuite struct{}
+
+var _ = Suite(&OutputSuite{})
+
+func (s *OutputSuite) TestValidateKey(c *C) {
+	for _, tc := range []struct {
+		key     string
+		checker Checker
+	}{
+		{"validKey", IsNil},
+		{"validKey2", IsNil},
+		{"valid_key", IsNil},
+		{"invalid-key", NotNil},
+		{"invalid.key", NotNil},
+		{"`invalidKey", NotNil},
+	} {
+		err := ValidateKey(tc.key)
+		c.Check(err, tc.checker, Commentf("Key (%s) failed!", tc.key))
+	}
+}