ref(color): simplify the color interface

The `Sequence` function doesn't need to have a bg argument, this should
be the job of the styler to apply bg specific modifications.

Make `ANSIColor` into a struct with a `bg` flag.

ansicolors.go

@@ -1,23 +1,23 @@
 package termenv
 
 // ANSI color codes
-const (
-	ANSIBlack ANSIColor = iota
-	ANSIRed
-	ANSIGreen
-	ANSIYellow
-	ANSIBlue
-	ANSIMagenta
-	ANSICyan
-	ANSIWhite
-	ANSIBrightBlack
-	ANSIBrightRed
-	ANSIBrightGreen
-	ANSIBrightYellow
-	ANSIBrightBlue
-	ANSIBrightMagenta
-	ANSIBrightCyan
-	ANSIBrightWhite
+var (
+	ANSIBlack         = ANSIColor{Color: 0}
+	ANSIRed           = ANSIColor{Color: 1}
+	ANSIGreen         = ANSIColor{Color: 2}
+	ANSIYellow        = ANSIColor{Color: 3}
+	ANSIBlue          = ANSIColor{Color: 4}
+	ANSIMagenta       = ANSIColor{Color: 5}
+	ANSICyan          = ANSIColor{Color: 6}
+	ANSIWhite         = ANSIColor{Color: 7}
+	ANSIBrightBlack   = ANSIColor{Color: 8}
+	ANSIBrightRed     = ANSIColor{Color: 9}
+	ANSIBrightGreen   = ANSIColor{Color: 10}
+	ANSIBrightYellow  = ANSIColor{Color: 11}
+	ANSIBrightBlue    = ANSIColor{Color: 12}
+	ANSIBrightMagenta = ANSIColor{Color: 13}
+	ANSIBrightCyan    = ANSIColor{Color: 14}
+	ANSIBrightWhite   = ANSIColor{Color: 15}
 )
 
 // RGB values of ANSI colors (0-255).

color.go

@@ -14,17 +14,30 @@ var (
 	ErrInvalidColor = errors.New("invalid color")
 )
 
+const (
+	// Foreground sequence code.
+	ForegroudSeq = "38"
+	// Background sequence code.
+	BackgroundSeq = "48"
+)
+
 // Foreground and Background sequence codes
 const (
-	Foreground = "38"
-	Background = "48"
+	// Foreground sequence code.
+	//
+	// Deprecated: use ForegroudSeq
+	Foreground = ForegroudSeq
+	// Background sequence code.
+	//
+	// Deprecated: use BackgroundSeq
+	Background = BackgroundSeq
 )
 
 // Color is an interface implemented by all colors that can be converted to an
 // ANSI sequence.
 type Color interface {
 	// Sequence returns the ANSI Sequence for the color.
-	Sequence(bg bool) string
+	Sequence() string
 }
 
 // NoColor is a nop for terminals that don't support colors.
@@ -35,10 +48,13 @@ func (c NoColor) String() string {
 }
 
 // ANSIColor is a color (0-15) as defined by the ANSI Standard.
-type ANSIColor int
+type ANSIColor struct {
+	Color int
+	bg    bool
+}
 
 func (c ANSIColor) String() string {
-	return ansiHex[c]
+	return ansiHex[c.Color]
 }
 
 // ANSI256Color is a color (16-255) as defined by the ANSI Standard.
@@ -58,7 +74,7 @@ func ConvertToRGB(c Color) colorful.Color {
 	case RGBColor:
 		hex = string(v)
 	case ANSIColor:
-		hex = ansiHex[v]
+		hex = ansiHex[v.Color]
 	case ANSI256Color:
 		hex = ansiHex[v]
 	}
@@ -68,18 +84,18 @@ func ConvertToRGB(c Color) colorful.Color {
 }
 
 // Sequence returns the ANSI Sequence for the color.
-func (c NoColor) Sequence(bg bool) string {
+func (c NoColor) Sequence() string {
 	return ""
 }
 
 // Sequence returns the ANSI Sequence for the color.
-func (c ANSIColor) Sequence(bg bool) string {
-	col := int(c)
-	bgMod := func(c int) int {
-		if bg {
-			return c + 10
+func (c ANSIColor) Sequence() string {
+	col := int(c.Color)
+	bgMod := func(col int) int {
+		if c.bg {
+			return col + 10
 		}
-		return c
+		return col
 	}
 
 	if col < 8 {
@@ -89,26 +105,18 @@ func (c ANSIColor) Sequence(bg bool) string {
 }
 
 // Sequence returns the ANSI Sequence for the color.
-func (c ANSI256Color) Sequence(bg bool) string {
-	prefix := Foreground
-	if bg {
-		prefix = Background
-	}
-	return fmt.Sprintf("%s;5;%d", prefix, c)
+func (c ANSI256Color) Sequence() string {
+	return fmt.Sprintf("5;%d", c)
 }
 
 // Sequence returns the ANSI Sequence for the color.
-func (c RGBColor) Sequence(bg bool) string {
+func (c RGBColor) Sequence() string {
 	f, err := colorful.Hex(string(c))
 	if err != nil {
 		return ""
 	}
 
-	prefix := Foreground
-	if bg {
-		prefix = Background
-	}
-	return fmt.Sprintf("%s;2;%d;%d;%d", prefix, uint8(f.R*255), uint8(f.G*255), uint8(f.B*255))
+	return fmt.Sprintf("2;%d;%d;%d", uint8(f.R*255), uint8(f.G*255), uint8(f.B*255))
 }
 
 func xTermColor(s string) (RGBColor, error) {
@@ -155,7 +163,7 @@ func ansi256ToANSIColor(c ANSI256Color) ANSIColor {
 		}
 	}
 
-	return ANSIColor(r)
+	return ANSIColor{Color: r}
 }
 
 func hexToANSI256Color(c colorful.Color) ANSI256Color {

profile.go

@@ -81,7 +81,7 @@ func (p Profile) Color(s string) Color {
 		}
 
 		if i < 16 {
-			c = ANSIColor(i)
+			c = ANSIColor{Color: i}
 		} else {
 			c = ANSI256Color(i)
 		}

style.go

@@ -59,15 +59,31 @@ func (t Style) Styled(s string) string {
 // Foreground sets a foreground color.
 func (t Style) Foreground(c Color) Style {
 	if c != nil {
-		t.styles = append(t.styles, c.Sequence(false))
+		if ac, ok := c.(ANSIColor); ok {
+			// ANSIColor(s) are their own sequences.
+			ac.bg = false
+			c = ac
+		} else if _, ok := c.(NoColor); !ok {
+			// NoColor can't have any sequences
+			t.styles = append(t.styles, ForegroudSeq)
+		}
+		t.styles = append(t.styles, c.Sequence())
 	}
 	return t
 }
 
 // Background sets a background color.
 func (t Style) Background(c Color) Style {
 	if c != nil {
-		t.styles = append(t.styles, c.Sequence(true))
+		if ac, ok := c.(ANSIColor); ok {
+			// ANSIColor(s) are their own sequences.
+			ac.bg = true
+			c = ac
+		} else if _, ok := c.(NoColor); !ok {
+			// NoColor can't have any sequences
+			t.styles = append(t.styles, BackgroundSeq)
+		}
+		t.styles = append(t.styles, c.Sequence())
 	}
 	return t
 }

termenv_other.go

@@ -13,12 +13,12 @@ func (o Output) ColorProfile() Profile {
 
 func (o Output) foregroundColor() Color {
 	// default gray
-	return ANSIColor(7)
+	return ANSIColor{Color: 7}
 }
 
 func (o Output) backgroundColor() Color {
 	// default black
-	return ANSIColor(0)
+	return ANSIColor{Color: 0}
 }
 
 // EnableVirtualTerminalProcessing enables virtual terminal processing on