Refactor CoRIM display to use DisplayOptions

cmd/corimDisplay.go

@@ -8,13 +8,22 @@ import (
 	"encoding/json"
 	"errors"
 	"fmt"
+	"io"
+	"os"
 
 	"github.com/spf13/afero"
 	"github.com/spf13/cobra"
+
 	"github.com/veraison/corim/corim"
 	"github.com/veraison/corim/cots"
 )
 
+// displayOptions holds output and rendering configuration.
+type DisplayOptions struct {
+	Writer   io.Writer
+	ShowTags bool
+}
+
 var (
 	corimDisplayCorimFile *string
 	corimDisplayShowTags  *bool
@@ -28,7 +37,7 @@ func NewCorimDisplayCmd() *cobra.Command {
 		Short: "display the content of a CoRIM as JSON",
 		Long: `display the content of a CoRIM as JSON
 
-	Display the contents of the signed CoRIM signed-corim.cbor 
+	Display the contents of the signed CoRIM signed-corim.cbor
 
 	  cocli corim display --file signed-corim.cbor
 
@@ -37,13 +46,17 @@ func NewCorimDisplayCmd() *cobra.Command {
 
 	  cocli corim display --file yet-another-signed-corim.cbor --show-tags
 	`,
-
 		RunE: func(cmd *cobra.Command, args []string) error {
 			if err := checkCorimDisplayArgs(); err != nil {
 				return err
 			}
 
-			return display(*corimDisplayCorimFile, *corimDisplayShowTags)
+			// Prepare our display options
+			opts := &DisplayOptions{
+				Writer:   os.Stdout,
+				ShowTags: *corimDisplayShowTags,
+			}
+			return display(*corimDisplayCorimFile, opts)
 		},
 	}
 
@@ -57,108 +70,103 @@ func checkCorimDisplayArgs() error {
 	if corimDisplayCorimFile == nil || *corimDisplayCorimFile == "" {
 		return errors.New("no CoRIM supplied")
 	}
-
 	return nil
 }
 
-func displaySignedCorim(s corim.SignedCorim, corimFile string, showTags bool) error {
+// displaySignedCorim marshals the signed CoRIM to JSON and prints it.
+func displaySignedCorim(s corim.SignedCorim, corimFile string, opts *DisplayOptions) error {
 	metaJSON, err := json.MarshalIndent(&s.Meta, "", "  ")
 	if err != nil {
 		return fmt.Errorf("error encoding CoRIM Meta from %s: %w", corimFile, err)
 	}
 
-	fmt.Println("Meta:")
-	fmt.Println(string(metaJSON))
+	fmt.Fprintln(opts.Writer, "Meta:")
+	fmt.Fprintln(opts.Writer, string(metaJSON))
 
 	corimJSON, err := json.MarshalIndent(&s.UnsignedCorim, "", "  ")
 	if err != nil {
 		return fmt.Errorf("error encoding unsigned CoRIM from %s: %w", corimFile, err)
 	}
 
-	fmt.Println("CoRIM:")
-	fmt.Println(string(corimJSON))
+	fmt.Fprintln(opts.Writer, "CoRIM:")
+	fmt.Fprintln(opts.Writer, string(corimJSON))
 
-	if showTags {
-		fmt.Println("Tags:")
-		displayTags(s.UnsignedCorim.Tags)
+	if opts.ShowTags {
+		fmt.Fprintln(opts.Writer, "Tags:")
+		displayTags(s.UnsignedCorim.Tags, opts)
 	}
 
 	return nil
 }
 
-func displayUnsignedCorim(u corim.UnsignedCorim, corimFile string, showTags bool) error {
+// displayUnsignedCorim marshals the unsigned CoRIM to JSON and prints it.
+func displayUnsignedCorim(u corim.UnsignedCorim, corimFile string, opts *DisplayOptions) error {
 	corimJSON, err := json.MarshalIndent(&u, "", "  ")
 	if err != nil {
 		return fmt.Errorf("error encoding unsigned CoRIM from %s: %w", corimFile, err)
 	}
 
-	fmt.Println("Corim:")
-	fmt.Println(string(corimJSON))
+	fmt.Fprintln(opts.Writer, "Corim:")
+	fmt.Fprintln(opts.Writer, string(corimJSON))
 
-	if showTags {
-		fmt.Println("Tags:")
-		displayTags(u.Tags)
+	if opts.ShowTags {
+		fmt.Fprintln(opts.Writer, "Tags:")
+		displayTags(u.Tags, opts)
 	}
 
 	return nil
 }
 
-func display(corimFile string, showTags bool) error {
-	var (
-		corimCBOR []byte
-		err       error
-	)
-
-	// read the CoRIM file
-	if corimCBOR, err = afero.ReadFile(fs, corimFile); err != nil {
+// display reads the given file, decodes it as either a signed or unsigned CoRIM,
+// and then calls the appropriate display function.
+func display(corimFile string, opts *DisplayOptions) error {
+	corimCBOR, err := afero.ReadFile(fs, corimFile)
+	if err != nil {
 		return fmt.Errorf("error loading CoRIM from %s: %w", corimFile, err)
 	}
 
 	// try to decode as a signed CoRIM
 	var s corim.SignedCorim
 	if err = s.FromCOSE(corimCBOR); err == nil {
 		// successfully decoded as signed CoRIM
-		return displaySignedCorim(s, corimFile, showTags)
+		return displaySignedCorim(s, corimFile, opts)
 	}
 
 	// if decoding as signed CoRIM failed, attempt to decode as unsigned CoRIM
 	var u corim.UnsignedCorim
 	if err = u.FromCBOR(corimCBOR); err != nil {
 		return fmt.Errorf("error decoding CoRIM (signed or unsigned) from %s: %w", corimFile, err)
 	}
-
 	// successfully decoded as unsigned CoRIM
-	return displayUnsignedCorim(u, corimFile, showTags)
+	return displayUnsignedCorim(u, corimFile, opts)
 }
 
-// displayTags processes and displays embedded tags within a CoRIM.
-func displayTags(tags []corim.Tag) {
+// displayTags loops over each tag, identifies its type, and prints the JSON.
+func displayTags(tags []corim.Tag, opts *DisplayOptions) {
 	for i, t := range tags {
 		if len(t) < 4 {
-			fmt.Printf(">> skipping malformed tag at index %d\n", i)
+			fmt.Fprintf(opts.Writer, ">> skipping malformed tag at index %d\n", i)
 			continue
 		}
 
-		// Split tag identifier from data
 		cborTag, cborData := t[:3], t[3:]
-
 		hdr := fmt.Sprintf(">> [ %d ]", i)
 
 		switch {
 		case bytes.Equal(cborTag, corim.ComidTag):
 			if err := printComid(cborData, hdr); err != nil {
-				fmt.Printf(">> skipping malformed CoMID tag at index %d: %v\n", i, err)
+				fmt.Fprintf(opts.Writer, ">> skipping malformed CoMID tag at index %d: %v\n", i, err)
 			}
 		case bytes.Equal(cborTag, corim.CoswidTag):
 			if err := printCoswid(cborData, hdr); err != nil {
-				fmt.Printf(">> skipping malformed CoSWID tag at index %d: %v\n", i, err)
+				fmt.Fprintf(opts.Writer, ">> skipping malformed CoSWID tag at index %d: %v\n", i, err)
 			}
 		case bytes.Equal(cborTag, cots.CotsTag):
 			if err := printCots(cborData, hdr); err != nil {
-				fmt.Printf(">> skipping malformed CoTS tag at index %d: %v\n", i, err)
+				fmt.Fprintf(opts.Writer, ">> skipping malformed CoTS tag at index %d: %v\n", i, err)
 			}
 		default:
-			fmt.Printf(">> unmatched CBOR tag: %x\n", cborTag)
+			fmt.Fprintf(opts.Writer, ">> unmatched CBOR tag: %x\n", cborTag)
 		}
 	}
 }