Refactor Execute() function to avoid many return statements

Author: vdjagilev

cmd/root.go

@@ -153,40 +153,20 @@ func run(cmd *cobra.Command, args []string) error {
 	}
 
 	workflow.SetConfig(&config)
+	workflow.SetInputFile()
+	workflow.SetOutputFile()
 
 	err = workflow.Execute()
 	if err != nil {
 		return err
 	}
-	return nil
-}
 
-// validate is checking input from the command line
-func validate(config formatter.Config) error {
-	if !config.OutputFormat.IsValid() {
-		return fmt.Errorf("not valid format: %s, please choose html/json/md/csv", config.OutputFormat)
+	if config.Writer != nil {
+		config.Writer.Close()
 	}
-
-	// Checking if xml file is readable
-	if !config.InputFileConfig.IsStdin {
-		err := config.InputFileConfig.ExistsOpen()
-		if err != nil {
-			return fmt.Errorf("could not open XML file: %v", err)
-		}
+	if config.InputFileConfig.Source != nil {
+		config.InputFileConfig.Source.Close()
 	}
 
-	// Checking if custom template is existing and readable and
-	if config.TemplatePath != "" {
-		switch config.OutputFormat {
-		case formatter.CSVOutput:
-		case formatter.JSONOutput:
-			return fmt.Errorf("cannot set templates for the formats other than HTML or Markdown")
-		}
-		file, err := os.Open(config.TemplatePath)
-		if err != nil {
-			return fmt.Errorf("could not read template file: %v", err)
-		}
-		defer file.Close()
-	}
 	return nil
 }

cmd/root_test.go

@@ -228,6 +228,10 @@ func Test_run(t *testing.T) {
 			config: formatter.Config{
 				OutputFormat: "html",
 				ShowVersion:  false, // false by default
+				Writer:       os.Stdout,
+				InputFileConfig: formatter.InputFileConfig{
+					Source: os.Stdin,
+				},
 			},
 			args:    args{},
 			wantErr: false,
@@ -258,6 +262,14 @@ func (w *testWorkflow) SetConfig(c *formatter.Config) {
 	log.Println("testWorkflow -> SetConfig")
 }
 
+func (w *testWorkflow) SetInputFile() {
+	log.Println("testWorkflow -> SetInputFile")
+}
+
+func (w *testWorkflow) SetOutputFile() {
+	log.Println("testWorkflow -> SetOutputFile")
+}
+
 func Test_shouldShowVersion(t *testing.T) {
 	type args struct {
 		c    *formatter.Config

cmd/validation.go

@@ -0,0 +1,62 @@
+package cmd
+
+import (
+	"fmt"
+	"os"
+
+	"github.com/vdjagilev/nmap-formatter/formatter"
+)
+
+// validate is checking input from the command line
+func validate(config formatter.Config) error {
+	if !config.OutputFormat.IsValid() {
+		return fmt.Errorf("not valid format: %s, please choose html/json/md/csv", config.OutputFormat)
+	}
+
+	err := validateIOFiles(config)
+	if err != nil {
+		return err
+	}
+
+	return validateTemplateConfig(config)
+}
+
+// validateIOFiles validates whether Input files and output files exists/have permissions to be created
+func validateIOFiles(config formatter.Config) error {
+	// Checking if xml file is readable
+	if !config.InputFileConfig.IsStdin {
+		err := config.InputFileConfig.ExistsOpen()
+		if err != nil {
+			return fmt.Errorf("could not open XML file: %v", err)
+		}
+	}
+	// Checking if output file can be created and does not exist already
+	// If OutputFile == "", it means that all output goes to stdout, no check needed
+	if config.OutputFile != "" {
+		outputFile, err := os.OpenFile(string(config.OutputFile), os.O_EXCL|os.O_WRONLY|os.O_CREATE, os.ModePerm)
+		if err != nil {
+			return fmt.Errorf("unable to create output file: %s", err)
+		}
+		outputFile.Close()
+		os.Remove(string(config.OutputFile))
+	}
+	return nil
+}
+
+// validateTemplateConfig validates template config, if it has adequate output format configs and is readable
+func validateTemplateConfig(config formatter.Config) error {
+	// Checking if custom template is existing and readable and
+	if config.TemplatePath != "" {
+		switch config.OutputFormat {
+		case formatter.CSVOutput:
+		case formatter.JSONOutput:
+			return fmt.Errorf("cannot set templates for the formats other than HTML or Markdown")
+		}
+		file, err := os.Open(config.TemplatePath)
+		if err != nil {
+			return fmt.Errorf("could not read template file: %v", err)
+		}
+		defer file.Close()
+	}
+	return nil
+}

formatter/config.go

@@ -10,7 +10,7 @@ import (
 // where output will be delivered, desired output format, input file path, output file path
 // and different output options
 type Config struct {
-	Writer          io.Writer
+	Writer          io.WriteCloser
 	OutputFormat    OutputFormat
 	InputFileConfig InputFileConfig
 	OutputFile      OutputFile

formatter/config_test.go

@@ -8,7 +8,7 @@ import (
 
 func TestConfig_CustomOptionsMap(t *testing.T) {
 	type fields struct {
-		Writer          io.Writer
+		Writer          io.WriteCloser
 		OutputFormat    OutputFormat
 		InputFileConfig InputFileConfig
 		OutputFile      OutputFile

formatter/file.go

@@ -16,7 +16,7 @@ type InputFile string
 type InputFileConfig struct {
 	Path    string
 	IsStdin bool
-	Source  io.Reader
+	Source  io.ReadCloser
 }
 
 // ReadContents reads content from stdin or provided file-path

formatter/formatter_csv_test.go

@@ -617,3 +617,7 @@ func (w *csvMockedWriter) Write(p []byte) (n int, err error) {
 	w.data = p
 	return len(p), nil
 }
+
+func (w *csvMockedWriter) Close() error {
+	return nil
+}

formatter/formatter_html_test.go

@@ -22,6 +22,10 @@ func (f *testHTMLMockedFormatterWriter) Write(p []byte) (n int, err error) {
 	return len(p), nil
 }
 
+func (f *testHTMLMockedFormatterWriter) Close() error {
+	return nil
+}
+
 func TestHTMLFormatter_Format(t *testing.T) {
 	type args struct {
 		td *TemplateData

formatter/formatter_json_test.go

@@ -131,3 +131,7 @@ func (w *jsonMockedWriter) Write(p []byte) (n int, err error) {
 	w.data = p
 	return len(p), nil
 }
+
+func (w *jsonMockedWriter) Close() error {
+	return nil
+}

formatter/formatter_md_test.go

@@ -130,6 +130,10 @@ func (w *markdownMockedWriter) Write(p []byte) (n int, err error) {
 	return len(p), nil
 }
 
+func (w *markdownMockedWriter) Close() error {
+	return nil
+}
+
 func TestMarkdownFormatter_Format(t *testing.T) {
 	type args struct {
 		td *TemplateData