Introduce formatter with default as stdout formatter

cmd/config.go

@@ -1,9 +1,11 @@
 package cmd
 
 import (
+	"errors"
 	"io"
 	"log"
 	"os"
+	"strings"
 
 	"github.com/aswinkarthik93/csvdiff/pkg/digest"
 )
@@ -18,6 +20,7 @@ func init() {
 type Config struct {
 	PrimaryKeyPositions  []int
 	ValueColumnPositions []int
+	Format               string
 	Base                 string
 	Delta                string
 	Additions            string
@@ -82,3 +85,35 @@ func getWriter(outputStream string) io.WriteCloser {
 	}
 	return os.Stdout
 }
+
+// Validate validates the config object
+// and returns error if not valid.
+func (c *Config) Validate() error {
+	allFormats := []string{stdout}
+
+	formatValid := false
+	for _, format := range allFormats {
+		if strings.ToLower(c.Format) == format {
+			formatValid = true
+		}
+	}
+
+	if !formatValid {
+		return errors.New("Specified format is not valid")
+	}
+
+	return nil
+}
+
+const (
+	stdout = "stdout"
+)
+
+// Formatter instantiates a new formatted
+// based on config.Format
+func (c *Config) Formatter() Formatter {
+	if strings.ToLower(c.Format) == stdout {
+		return &StdoutFormatter{}
+	}
+	return &StdoutFormatter{}
+}

cmd/config_test.go

@@ -1,30 +1,62 @@
-package cmd
+package cmd_test
 
 import (
 	"testing"
 
+	"github.com/aswinkarthik93/csvdiff/cmd"
 	"github.com/aswinkarthik93/csvdiff/pkg/digest"
 	"github.com/stretchr/testify/assert"
 )
 
 func TestPrimaryKeyPositions(t *testing.T) {
-	config := Config{PrimaryKeyPositions: []int{0, 1}}
+	config := cmd.Config{PrimaryKeyPositions: []int{0, 1}}
 	assert.Equal(t, digest.Positions([]int{0, 1}), config.GetPrimaryKeys())
 
-	config = Config{PrimaryKeyPositions: []int{}}
+	config = cmd.Config{PrimaryKeyPositions: []int{}}
 	assert.Equal(t, digest.Positions([]int{0}), config.GetPrimaryKeys())
 
-	config = Config{}
+	config = cmd.Config{}
 	assert.Equal(t, digest.Positions([]int{0}), config.GetPrimaryKeys())
 }
 
 func TestValueColumnPositions(t *testing.T) {
-	config := Config{ValueColumnPositions: []int{0, 1}}
+	config := cmd.Config{ValueColumnPositions: []int{0, 1}}
 	assert.Equal(t, digest.Positions([]int{0, 1}), config.GetValueColumns())
 
-	config = Config{ValueColumnPositions: []int{}}
+	config = cmd.Config{ValueColumnPositions: []int{}}
 	assert.Equal(t, digest.Positions([]int{}), config.GetValueColumns())
 
-	config = Config{}
+	config = cmd.Config{}
 	assert.Equal(t, digest.Positions([]int{}), config.GetValueColumns())
 }
+
+func TestConfigValidate(t *testing.T) {
+	var config *cmd.Config
+
+	config = &cmd.Config{}
+	assert.Error(t, config.Validate())
+
+	config = &cmd.Config{Format: "stdout"}
+	assert.NoError(t, config.Validate())
+
+	config = &cmd.Config{Format: "stdOUT"}
+	assert.NoError(t, config.Validate())
+}
+
+func TestDefaultConfigFormatter(t *testing.T) {
+	config := &cmd.Config{}
+
+	formatter, ok := config.Formatter().(*cmd.StdoutFormatter)
+
+	assert.True(t, ok)
+	assert.NotNil(t, formatter)
+}
+
+func TestStdoutConfigFormatter(t *testing.T) {
+	config := &cmd.Config{Format: "stdout"}
+
+	formatter, ok := config.Formatter().(*cmd.StdoutFormatter)
+
+	assert.True(t, ok)
+	assert.NotNil(t, formatter)
+}

cmd/formatter.go

@@ -0,0 +1,31 @@
+package cmd
+
+import (
+	"fmt"
+
+	"github.com/aswinkarthik93/csvdiff/pkg/digest"
+)
+
+// Formatter defines the interface through which differences
+// can be formatted and displayed
+type Formatter interface {
+	Format(digest.Difference)
+}
+
+// StdoutFormatter formats diff to STDOUT
+type StdoutFormatter struct{}
+
+// Format prints the diff to os.Stdout
+func (f *StdoutFormatter) Format(diff digest.Difference) {
+	fmt.Printf("Additions %d\n", len(diff.Additions))
+	fmt.Printf("Modifications %d\n", len(diff.Modifications))
+	fmt.Println("Rows:")
+
+	for _, added := range diff.Additions {
+		fmt.Printf("%s,%s\n", added, "ADDED")
+	}
+
+	for _, modified := range diff.Modifications {
+		fmt.Printf("%s,%s\n", modified, "MODIFIED")
+	}
+}

cmd/root.go

@@ -77,17 +77,7 @@ Most suitable for csv files created from database tables`,
 
 		diff := digest.Diff(baseConfig, deltaConfig)
 
-		fmt.Printf("Additions %d\n", len(diff.Additions))
-		fmt.Printf("Modifications %d\n", len(diff.Modifications))
-		fmt.Println("Rows:")
-
-		for _, added := range diff.Additions {
-			fmt.Printf("%s,%s\n", added, "ADDED")
-		}
-
-		for _, modified := range diff.Modifications {
-			fmt.Printf("%s,%s\n", modified, "MODIFIED")
-		}
+		config.Formatter().Format(diff)
 	},
 }