exit with error if both --color and --image flags are specified

cmd/maze/action.go

@@ -42,11 +42,9 @@ func action(ctx *cli.Context) error {
 		case "":
 			maze.Print(config.Output, config.Format)
 		case "png":
-			maze.PrintPNG(config.Output, config.Format, config.Scale)
+			maze.PrintPNG(config.Output, config.Scale)
 		case "svg":
-			maze.PrintSVG(config.Output, config.Format, config.Scale)
-		default:
-			return fmt.Errorf("unsupported image format: %s", config.Image)
+			maze.PrintSVG(config.Output, config.Scale)
 		}
 	}
 	return nil

cmd/maze/config.go

@@ -2,6 +2,7 @@ package main
 
 import (
 	"errors"
+	"fmt"
 	"io"
 	"os"
 	"strconv"
@@ -108,10 +109,19 @@ func makeConfig(ctx *cli.Context) (*Config, []error) {
 	}
 
 	image := ctx.GlobalString("image")
-	if image != "" {
+	switch image {
+	case "":
+	case "png":
 		if file, ok := output.(*os.File); ok && isatty.IsTerminal(file.Fd()) {
-			errs = append(errs, errors.New("cannot write image data into the terminal\nuse -output flag"))
+			errs = append(errs, errors.New("cannot write PNG data to the terminal\nuse --output flag or redirect the output to a file"))
 		}
+		fallthrough
+	case "svg":
+		if format != maze.Default {
+			errs = append(errs, errors.New("cannot use --color and --image flags together"))
+		}
+	default:
+		errs = append(errs, fmt.Errorf("unsupported image format: %s", image))
 	}
 
 	scale := ctx.GlobalInt("scale")

maze.go

@@ -361,9 +361,9 @@ func plot(img *image.RGBA, x, y, scale int, c color.Color) {
 }
 
 // PrintPNG outputs the maze to the IO writer as PNG image
-func (maze *Maze) PrintPNG(writer io.Writer, format *Format, scale int) {
+func (maze *Maze) PrintPNG(writer io.Writer, scale int) {
 	var sb strings.Builder
-	maze.Print(&sb, format)
+	maze.Print(&sb, Default)
 	lines := strings.Split(strings.TrimSpace(sb.String()), "\n")
 	for i, line := range lines {
 		lines[i] = strings.TrimSpace(line)
@@ -400,17 +400,17 @@ func (maze *Maze) PrintPNG(writer io.Writer, format *Format, scale int) {
 }
 
 // PrintSVG outputs the maze to the IO writer as SVG image
-func (maze *Maze) PrintSVG(writer io.Writer, format *Format, scale int) {
+func (maze *Maze) PrintSVG(writer io.Writer, scale int) {
 	var sb strings.Builder
-	maze.Print(&sb, format)
+	maze.Print(&sb, Default)
 	lines := strings.Split(strings.TrimSpace(sb.String()), "\n")
 	for i, line := range lines {
 		lines[i] = strings.TrimSpace(line)
 	}
 	width := len(lines[0]) / 2
 	height := len(lines)
-	fmt.Fprintf(writer, "<svg viewBox=\"0 0 %d %d\" xmlns=\"http://www.w3.org/2000/svg\">\n", width*scale, height*scale)
-	fmt.Fprintf(writer, "<rect width=\"%d\" height=\" %d\" fill=\"white\" />\n", width*scale, height*scale)
+	fmt.Fprintf(writer, `<svg viewBox="0 0 %d %d" xmlns="http://www.w3.org/2000/svg">`+"\n", width*scale, height*scale)
+	fmt.Fprintf(writer, `<rect width="%d" height="%d" fill="white" />`+"\n", width*scale, height*scale)
 	for y := 0; y < height; y++ {
 		if y >= len(lines) {
 			continue