Make a factory method for PaintBrush (validate styles)

README.md

@@ -19,11 +19,11 @@ color.bold.cprintln('Hello World')
 ```v
 import color
 
-brush := color.PaintBrush{
+brush := color.new_brush(
     fg: color.rgb(0, 0, 0)!
     bg: color.hex(0xffffff)!
-    styles: [color.bold, color.underline, color.italic]
+    style: [color.bold, color.underline, color.italic]
-}
+)!
 
 brush.cprintln('Hello World')
 ```

builder_error2.v

@@ -3,11 +3,11 @@ module main
 import color
 
 fn main() {
-	p := color.PaintBrush{
+	p := color.new_brush(
 		fg: color.rgb(0, 0, 0)!
 		bg: color.hex(0xffffff)!
-		styles: [color.bold, color.underline, color.italic]
+		style: [color.bold, color.underline, color.italic]
-	}
+	)!
 
 	p.cprintln('Hello World')
 }

color/paintbrush.v

@@ -1,10 +1,36 @@
 module color
 
+[noinit]
 pub struct PaintBrush {
 pub:
-	fg     ?Color
+	fg    ?Color
-	bg     ?Color
+	bg    ?Color
-	styles []Style
+	style []Style
+}
+
+[params]
+pub struct PaintBrushParams {
+	fg    ?Color
+	bg    ?Color
+	style []Style
+}
+
+pub fn new_brush(p PaintBrushParams) !PaintBrush {
+	mut count := map[Style]int{}
+
+	for style in p.style {
+		count[style]++
+
+		if count[style] > 1 {
+			return error('Multiple of the same style was provided')
+		}
+	}
+
+	return PaintBrush{
+		fg: p.fg
+		bg: p.bg
+		style: p.style
+	}
 }
 
 pub fn (p &PaintBrush) render(msg string) string {
@@ -20,7 +46,7 @@ pub fn (p &PaintBrush) render(msg string) string {
 	if bg := p.bg {
 		result = bg.render(result)
 	}
-	for style in p.styles {
+	for style in p.style {
 		result = style.render(result)
 	}