base code | coloring format v1 (foreground and/or background) | only _real_ issue for now, text cannot contain the character '$' due to regexp mechanism

colors.go

@@ -0,0 +1,82 @@
+package clifmt
+
+import (
+	"fmt"
+	"io"
+	"strconv"
+)
+
+type terminalColor uint32
+
+var colorMap = make(map[string]terminalColor)
+
+func init() {
+	colorMap["red"] = 0xff0000
+	colorMap["green"] = 0x00ff00
+	colorMap["blue"] = 0x0000ff
+}
+
+// fromName returns the integer value of a color name
+// from the built-in color map ; it is case insensitive
+func fromName(s string) (terminalColor, error) {
+	value, ok := colorMap[s]
+	if !ok {
+		return 0, fmt.Errorf("unknown color name '%'", s)
+	}
+	return value, nil
+}
+
+// fromHex returns the integer value associated with
+// an hexadecimal string (full-sized or short version)
+// the format is 'abc' or 'abcdef'
+func fromHex(s string) (terminalColor, error) {
+	if len(s) != 3 && len(s) != 6 {
+		return 0, fmt.Errorf("expect a size of 3 or 6 (remove the '#' prefix)")
+	}
+
+	// short version
+	input := s
+	if len(s) == 3 {
+		input = fmt.Sprintf("%c%c%c%c%c%c", s[0], s[0], s[1], s[1], s[2], s[2])
+	}
+
+	n, err := strconv.ParseUint(input, 16, 32)
+	if err != nil {
+		return 0, err
+	}
+
+	return terminalColor(n), nil
+}
+
+// parseColor tries to parse a color string (can be a name or an hexa value)
+func parseColor(s string) (terminalColor, error) {
+
+	// (0) ...
+	if len(s) < 1 {
+		return 0, io.ErrUnexpectedEOF
+	}
+
+	// (1) hexa
+	if s[0] == '#' {
+		return fromHex(s[1:])
+	}
+
+	// (2) name
+	return fromName(s)
+
+}
+
+// Red component of the color
+func (c terminalColor) Red() uint8 {
+	return uint8((c >> 16) & 0xff)
+}
+
+// Green component of the color
+func (c terminalColor) Green() uint8 {
+	return uint8((c >> 8) & 0xff)
+}
+
+// Blue component of the color
+func (c terminalColor) Blue() uint8 {
+	return uint8(c & 0xff)
+}

printer.go

@@ -0,0 +1,85 @@
+package clifmt
+
+import (
+	"fmt"
+	"regexp"
+)
+
+// extractor helps extract features from the coloring format defined as follows :
+//
+// - [Color] -> [a-z]       # named color
+// - [Color] -> #[0-9a-f]{3} # hexa color (shortcode)
+// - [Color] -> #[0-9a-f]{6} # hexa color (full-sized)
+// - [Text] -> ANY
+// - [Format] -> ${Text}(Color:Color) # foreground, background colors
+// - [Format] -> ${Text}(Color)       # foreground color only
+// - [Format] -> ${Text}(:Color)      # background color only
+var extractor = regexp.MustCompile(`(?m)\${([^$]+)}\(((?:[a-z]+|#(?:[0-9a-f]{3}|[0-9a-f]{6})))?(?:\:((?:[a-z]+|#(?:[0-9a-f]{3}|[0-9a-f]{6}))))?\)`)
+
+func Printf(format string, a ...interface{}) error {
+	// 1. Pre-process format with 'fmt'
+	input := fmt.Sprintf(format, a...)
+	output := ""
+	cursor := int(0)
+
+	// 2. extract color format matches
+	for _, match := range extractor.FindAllStringSubmatchIndex(input, -1) {
+		// (1) add gap between input start OR previous match
+		output += input[cursor:match[0]]
+		cursor = match[1]
+
+		// (2) extract features
+		var (
+			err         = error(nil)
+			text        = ""
+			sForeground = ""
+			sBackground = ""
+			foreground  = terminalColor(0)
+			background  = terminalColor(0)
+		)
+
+		if match[3]-match[2] > 0 {
+			text = input[match[2]:match[3]]
+		}
+		if match[5]-match[4] > 0 {
+			sForeground = input[match[4]:match[5]]
+			foreground, err = parseColor(sForeground)
+			if err != nil {
+				return err
+			}
+		}
+		if match[7]-match[6] > 0 {
+			sBackground = input[match[6]:match[7]]
+			background, err = parseColor(sBackground)
+			if err != nil {
+				return err
+			}
+		}
+
+		// (3) replace text with colorized text
+		if len(sForeground) > 0 {
+			text = colorize(text, true, foreground)
+		}
+		if len(sBackground) > 0 {
+			text = colorize(text, false, background)
+		}
+		output += text
+	}
+
+	// 3. Add end of input
+	if cursor < len(input)-1 {
+		output += input[cursor:]
+	}
+
+	// 3. print final output
+	fmt.Print(output)
+	return nil
+}
+
+func colorize(text string, foregound bool, color terminalColor) string {
+	if foregound {
+		return fmt.Sprintf("\033[38;2;%d;%d;%dm%s\033[0m", color.Red(), color.Green(), color.Blue(), text)
+	}
+
+	return fmt.Sprintf("\033[48;2;%d;%d;%dm%s\033[0m", color.Red(), color.Green(), color.Blue(), text)
+}