Refactor formatting differences

cmd/config.go

@@ -2,7 +2,6 @@ package cmd
 
 import (
 	"errors"
-	"os"
 	"strings"
 
 	"github.com/aswinkarthik/csvdiff/pkg/digest"
@@ -60,27 +59,3 @@ func (c *Config) Validate() error {
 
 	return errors.New("Specified format is not valid")
 }
-
-const (
-	rowmark    = "rowmark"
-	jsonFormat = "json"
-	diffFormat = "diff"
-)
-
-// Formatter instantiates a new formatted
-// based on config.Format
-func (c *Config) Formatter() Formatter {
-	format := strings.ToLower(c.Format)
-
-	switch format {
-	case jsonFormat:
-		return &JSONFormatter{
-			Stdout: os.Stdout,
-		}
-	default:
-		return &RowMarkFormatter{
-			Stdout: os.Stdout,
-			Stderr: os.Stderr,
-		}
-	}
-}

cmd/config_test.go

@@ -45,28 +45,3 @@ func TestConfigValidate(t *testing.T) {
 	config = &cmd.Config{Format: "json"}
 	assert.NoError(t, config.Validate())
 }
-
-func TestDefaultConfigFormatter(t *testing.T) {
-	config := &cmd.Config{}
-
-	formatter, ok := config.Formatter().(*cmd.RowMarkFormatter)
-
-	assert.True(t, ok)
-	assert.NotNil(t, formatter)
-}
-
-func TestConfigFormatter(t *testing.T) {
-	var config *cmd.Config
-	var formatter cmd.Formatter
-	var ok bool
-
-	config = &cmd.Config{Format: "rowmark"}
-	formatter, ok = config.Formatter().(*cmd.RowMarkFormatter)
-	assert.True(t, ok)
-	assert.NotNil(t, formatter)
-
-	config = &cmd.Config{Format: "json"}
-	formatter, ok = config.Formatter().(*cmd.JSONFormatter)
-	assert.True(t, ok)
-	assert.NotNil(t, formatter)
-}

cmd/formatter.go

@@ -9,25 +9,47 @@ import (
 	"github.com/aswinkarthik/csvdiff/pkg/digest"
 )
 
-// Formatter defines the interface through which differences
-// can be formatted and displayed
-type Formatter interface {
-	Format(digest.Differences) error
+const (
+	rowmark    = "rowmark"
+	jsonFormat = "json"
+	diffFormat = "diff"
+)
+
+// Formatter can print the differences to stdout
+// and accompanying metadata to stderr
+type Formatter struct {
+	stdout io.Writer
+	stderr io.Writer
+	config Config
 }
 
-// RowMarkFormatter formats diff by marking each row as
-// ADDED/MODIFIED. It mutates the row and adds as a new column.
-type RowMarkFormatter struct {
-	Stdout io.Writer
-	Stderr io.Writer
+// NewFormatter can be used to create a new formatter
+func NewFormatter(stdout, stderr io.Writer, config Config) *Formatter {
+	return &Formatter{stdout: stdout, stderr: stderr, config: config}
 }
 
-// Format prints the diff to os.Stdout
-func (f *RowMarkFormatter) Format(diff digest.Differences) error {
-	fmt.Fprintf(f.Stderr, "Additions %d\n", len(diff.Additions))
-	fmt.Fprintf(f.Stderr, "Modifications %d\n", len(diff.Modifications))
-	fmt.Fprintf(f.Stderr, "Rows:\n")
-
+// Format can be used to format the differences based on config
+// to appropriate writers
+func (f *Formatter) Format(diff digest.Differences) error {
+	switch f.config.Format {
+	case jsonFormat:
+		return f.json(diff)
+	case rowmark:
+		return f.rowMark(diff)
+	default:
+		return fmt.Errorf("formatter not found")
+	}
+}
+
+// JSONFormatter formats diff to as a JSON Object
+// { "Additions": [...], "Modifications": [...] }
+func (f *Formatter) json(diff digest.Differences) error {
+	// jsonDifference is a struct to represent legacy JSON format
+	type jsonDifference struct {
+		Additions     []string
+		Modifications []string
+	}
+
 	additions := make([]string, 0, len(diff.Additions))
 	for _, addition := range diff.Additions {
 		additions = append(additions, strings.Join(addition, ","))
@@ -38,39 +60,30 @@ func (f *RowMarkFormatter) Format(diff digest.Differences) error {
 		modifications = append(modifications, strings.Join(modification.Current, ","))
 	}
 
-	for _, added := range additions {
-		_, err := fmt.Fprintf(f.Stdout, "%s,%s\n", added, "ADDED")
+	jsonDiff := jsonDifference{Additions: additions, Modifications: modifications}
+	data, err := json.MarshalIndent(jsonDiff, "", "  ")
 
-		if err != nil {
-			return fmt.Errorf("error when formatting additions with RowMark formatter: %v", err)
-		}
+	if err != nil {
+		return fmt.Errorf("error when serializing with JSON formatter: %v", err)
 	}
 
-	for _, modified := range modifications {
-		_, err := fmt.Fprintf(f.Stdout, "%s,%s\n", modified, "MODIFIED")
-
-		if err != nil {
-			return fmt.Errorf("error when formatting modifications with RowMark formatter: %v", err)
-		}
+	_, err = f.stdout.Write(data)
 
+	if err != nil {
+		return fmt.Errorf("error when writing to writer with JSON formatter: %v", err)
 	}
 
 	return nil
 }
 
-// JSONFormatter formats diff to as a JSON Object
-type JSONFormatter struct {
-	Stdout io.Writer
-}
+// RowMarkFormatter formats diff by marking each row as
+// ADDED/MODIFIED. It mutates the row and adds as a new column.
+func (f *Formatter) rowMark(diff digest.Differences) error {
 
-// JSONDifference is a struct to represent legacy JSON format
-type JSONDifference struct {
-	Additions     []string
-	Modifications []string
-}
+	fmt.Fprintf(f.stderr, "Additions %d\n", len(diff.Additions))
+	fmt.Fprintf(f.stderr, "Modifications %d\n", len(diff.Modifications))
+	fmt.Fprintf(f.stderr, "Rows:\n")
 
-// Format prints the diff as a JSON
-func (f *JSONFormatter) Format(diff digest.Differences) error {
 	additions := make([]string, 0, len(diff.Additions))
 	for _, addition := range diff.Additions {
 		additions = append(additions, strings.Join(addition, ","))
@@ -81,17 +94,21 @@ func (f *JSONFormatter) Format(diff digest.Differences) error {
 		modifications = append(modifications, strings.Join(modification.Current, ","))
 	}
 
-	jsonDiff := JSONDifference{Additions: additions, Modifications: modifications}
-	data, err := json.MarshalIndent(jsonDiff, "", "  ")
+	for _, added := range additions {
+		_, err := fmt.Fprintf(f.stdout, "%s,%s\n", added, "ADDED")
 
-	if err != nil {
-		return fmt.Errorf("error when serializing with JSON formatter: %v", err)
+		if err != nil {
+			return fmt.Errorf("error when formatting additions with RowMark formatter: %v", err)
+		}
 	}
 
-	_, err = f.Stdout.Write(data)
+	for _, modified := range modifications {
+		_, err := fmt.Fprintf(f.stdout, "%s,%s\n", modified, "MODIFIED")
+
+		if err != nil {
+			return fmt.Errorf("error when formatting modifications with RowMark formatter: %v", err)
+		}
 
-	if err != nil {
-		return fmt.Errorf("error when writing to writer with JSON formatter: %v", err)
 	}
 
 	return nil

cmd/formatter_test.go

@@ -11,7 +11,6 @@ import (
 )
 
 func TestJSONFormat(t *testing.T) {
-	var formatter cmd.Formatter
 	diff := digest.Differences{
 		Additions:     []digest.Addition{[]string{"additions"}},
 		Modifications: []digest.Modification{digest.Modification{Current: []string{"modification"}}},
@@ -26,16 +25,16 @@ func TestJSONFormat(t *testing.T) {
 }`
 
 	var stdout bytes.Buffer
+	var stderr bytes.Buffer
 
-	formatter = &cmd.JSONFormatter{Stdout: &stdout}
+	formatter := cmd.NewFormatter(&stdout, &stderr, cmd.Config{Format: "json"})
 
 	err := formatter.Format(diff)
 	assert.NoError(t, err)
 	assert.Equal(t, expected, stdout.String())
 }
 
 func TestRowMarkFormatter(t *testing.T) {
-	var formatter cmd.Formatter
 	diff := digest.Differences{
 		Additions:     []digest.Addition{[]string{"additions"}},
 		Modifications: []digest.Modification{digest.Modification{Current: []string{"modification"}}},
@@ -51,7 +50,7 @@ Rows:
 	var stdout bytes.Buffer
 	var stderr bytes.Buffer
 
-	formatter = &cmd.RowMarkFormatter{Stdout: &stdout, Stderr: &stderr}
+	formatter := cmd.NewFormatter(&stdout, &stderr, cmd.Config{Format: "rowmark"})
 
 	err := formatter.Format(diff)
 

cmd/root.go

@@ -94,7 +94,10 @@ Most suitable for csv files created from database tables`,
 			os.Exit(2)
 		}
 
-		config.Formatter().Format(diff)
+		if err := NewFormatter(os.Stdout, os.Stderr, config).Format(diff); err != nil {
+			fmt.Fprintf(os.Stderr, "csvdiff failed: %v\n", err)
+			os.Exit(3)
+		}
 
 		return
 	},