Add write to file option and small improvements

.gitignore

@@ -1 +1 @@
-.go-version
+.go-version

args.go

@@ -9,9 +9,11 @@ const (
 )
 
 type Args struct {
-	Files []string
-	Delim string
-	Pad   int
+	Files          []string
+	Delim          string
+	Pad            int
+	OutputFile     string
+	ForceOverwrite bool
 }
 
 var Delims = []string{",", ";"}
@@ -32,21 +34,21 @@ func (args *Args) ValidateAll() error {
 
 func (args *Args) validateFiles() error {
 	if len(args.Files) < 1 {
-		return fmt.Errorf(ERROR_NO_FILENAME)
+		return fmt.Errorf("%s", ERROR_NO_FILENAME)
 	}
 	return nil
 }
 
 func (args *Args) validateDelim() error {
 	if !contains(Delims, args.Delim) {
-		return fmt.Errorf("Error: delimiter should be one of %+q, but got %q", Delims, args.Delim)
+		return fmt.Errorf("error: delimiter should be one of %+q, but got %q", Delims, args.Delim)
 	}
 	return nil
 }
 
 func (args *Args) validatePad() error {
 	if args.Pad < 0 {
-		return fmt.Errorf("Error: padding should be positive integer, but got %d", args.Pad)
+		return fmt.Errorf("error: padding should be positive integer, but got %d", args.Pad)
 	}
 	return nil
 }

args_test.go

@@ -14,7 +14,7 @@ func TestArgs(t *testing.T) {
 		}
 		err := args.ValidateAll()
 		if err != nil {
-			t.Errorf(err.Error())
+			t.Error(err.Error())
 			t.Errorf("Input Args: %+v\n", args)
 		}
 	})
@@ -27,7 +27,7 @@ func TestArgs(t *testing.T) {
 		}
 		err := args.ValidateAll()
 		if err != nil {
-			t.Errorf(err.Error())
+			t.Error(err.Error())
 			t.Errorf("Input Args: %+v\n", args)
 		}
 	})

convert.go

@@ -2,6 +2,7 @@ package main
 
 import (
 	"encoding/csv"
+	"errors"
 	"fmt"
 	"os"
 	"strings"
@@ -19,8 +20,18 @@ func ConvertAll(args *Args) error {
 		if err != nil {
 			return err
 		}
-		// print markdown
-		fmt.Println(md)
+		if args.OutputFile == "" {
+			fmt.Println(md)
+		} else {
+			_, err := os.Stat(args.OutputFile)
+			if errors.Is(err, os.ErrNotExist) || args.ForceOverwrite {
+				os.WriteFile(args.OutputFile, []byte(md), 0644)
+			} else {
+				fmt.Printf(
+					"skip writing output, file exists: %s\n", args.OutputFile,
+				)
+			}
+		}
 	}
 	return nil
 }
@@ -74,9 +85,7 @@ func ArrayToMd(records [][]string, args *Args) (string, error) {
 	md := []string{}
 	md = append(md, rows[0]) // header
 	md = append(md, horiz)   // horizontal devider
-	for _, v := range rows[1:] {
-		md = append(md, v)
-	}
+	md = append(md, rows[1:]...)
 
 	return strings.Join(md, "\n"), nil
 }
@@ -99,7 +108,7 @@ func padCells(records [][]string, colSizes []int) ([][]string, error) {
 				fmt.Println(v)
 				fmt.Println(colSizes[j])
 				fmt.Println(utf8.RuneCountInString(v))
-				return nil, fmt.Errorf("Internal error: column size is bigger than max.")
+				return nil, fmt.Errorf("internal error: column size is bigger than max")
 			}
 		}
 	}

convert_test.go

@@ -22,7 +22,7 @@ func TestConvert(t *testing.T) {
 
 		md, err := Convert(testFile, args)
 		if err != nil {
-			t.Errorf(err.Error())
+			t.Error(err.Error())
 		}
 
 		if md != expected {
@@ -43,7 +43,7 @@ func TestConvert(t *testing.T) {
 
 		md, err := Convert(testFile, args)
 		if err != nil {
-			t.Errorf(err.Error())
+			t.Error(err.Error())
 		}
 
 		if md != expected {
@@ -64,7 +64,7 @@ func TestConvert(t *testing.T) {
 
 		md, err := Convert(testFile, args)
 		if err != nil {
-			t.Errorf(err.Error())
+			t.Error(err.Error())
 		}
 
 		if md != expected {
@@ -85,7 +85,7 @@ func TestConvert(t *testing.T) {
 
 		md, err := Convert(testFile, args)
 		if err != nil {
-			t.Errorf(err.Error())
+			t.Error(err.Error())
 		}
 
 		if md != expected {

main.go

@@ -30,6 +30,20 @@ func main() {
 				Usage:       "CSV delimiter, expected values: ',', ';'.",
 				Destination: &args.Delim,
 			},
+			&cli.StringFlag{
+				Name:        "output",
+				Aliases:     []string{"o"},
+				Value:       "",
+				Usage:       "Write output to file, not overwriting existing file by default",
+				Destination: &args.OutputFile,
+			},
+			&cli.BoolFlag{
+				Name:        "force",
+				Aliases:     []string{"f"},
+				Value:       false,
+				Usage:       "Force overwrite, if output file already exists",
+				Destination: &args.ForceOverwrite,
+			},
 		},
 		Action: func(c *cli.Context) error {
 			args.Files = c.Args().Slice()