Added SGR fields to the RGB struct for bold and italic;

allow RGB values to be -1 (default color);
allow underscore in color names

color.go

@@ -18,12 +18,17 @@ type color struct {
 	colorObj *colorData.Color
 }
 
-// A RGB represents a Red, Blue, Green trio of values. Each value is represented as
-// an int.
+// A RGB represents a Red, Blue, Green trio of values, along with SGR parameters.
+// Each value is represented as an int. For info on SGR parameters, see:
+// https://en.wikipedia.org/wiki/ANSI_escape_code#Select_Graphic_Rendition_parameters
+// If 'red', 'green' and 'blue' are all -1, then the default terminal color is used.
+// If some (but not all) of them are -1, an error is thrown.
 type RGB struct {
+	sgr1  int
 	red   int
 	blue  int
 	green int
+	sgr2  int
 }
 
 // The following is a list of all possible colors, stored in a map.
@@ -76,59 +81,79 @@ func newColorMust(colorString string) color {
 // characters.
 func isValidColorName(colorName string) bool {
 	for _, ch := range colorName {
-		if ch > 'Z' || ch < 'A' {
+		if (ch > 'Z' || ch < 'A') && (ch != '_') {
 			return false
 		}
 	}
 	return true
 }
 
-// stringToRGB takes a string representing an RGB trio. It constructs and RGB type and
+// stringToRGB takes a string representing an RGB five-tuple. It constructs and RGB type and
 // returns it. Any errors encountered are returned. If an error is returned, it is safe to
-// assume that the string doesn't represent an RGB trio.
+// assume that the string doesn't represent an RGB five-tuple.
 func stringToRGB(rgbString string) (*RGB, error) {
 	values := strings.Split(rgbString, " ")
 	// There must be three space-separated strings.
-	if len(values) != 3 {
+	if len(values) != 5 {
 		// TODO: Instead of ignoring these errors and returning a generic error (as I do in the
 		// callee), wrap the error returned from this function, inside the error returned by the callee.
-		return nil, fmt.Errorf("Error parsing RGB trio.")
+		return nil, fmt.Errorf("Error parsing RGB five-tuple.")
 	}
 	// If any of the strings doesn't represent an integer (or is out of bounds), return an error.
 	// WARNING: LAZY CODE INCOMING
 	var toReturn RGB
 	var err error
-	toReturn.red, err = strconv.Atoi(values[0])
+	toReturn.sgr1, err = strconv.Atoi(values[0])
+	if err != nil {
+		return nil, fmt.Errorf("Error parsing SGR1 integer: Invalid value.")
+	}
+	if toReturn.sgr1 < 0 || toReturn.sgr1 > 107 { // Maximum value for SGR values
+		return nil, fmt.Errorf("Error parsing SGR1 integer: Out-of-bounds.")
+	}
+	toReturn.red, err = strconv.Atoi(values[1])
 	if err != nil {
 		return nil, fmt.Errorf("Error parsing RED integer: Invalid value.")
 	}
-	if toReturn.red < 0 || toReturn.red > 255 {
+	if toReturn.red < -1 || toReturn.red > 255 {
 		return nil, fmt.Errorf("Error parsing RED integer: Out-of-bounds.")
 	}
-	toReturn.blue, err = strconv.Atoi(values[1])
+	toReturn.blue, err = strconv.Atoi(values[2])
 	if err != nil {
 		return nil, fmt.Errorf("Error parsing BLUE integer: Invalid value.")
 	}
-	if toReturn.blue < 0 || toReturn.blue > 255 {
+	if toReturn.blue < -1 || toReturn.blue > 255 {
 		return nil, fmt.Errorf("Error parsing BLUE integer: Out-of-bounds.")
 	}
-	toReturn.green, err = strconv.Atoi(values[2])
+	toReturn.green, err = strconv.Atoi(values[3])
 	if err != nil {
 		return nil, fmt.Errorf("Error parsing GREEN integer: Invalid value.")
 	}
-	if toReturn.green < 0 || toReturn.green > 255 {
+	if toReturn.green < -1 || toReturn.green > 255 {
 		return nil, fmt.Errorf("Error parsing GREEN integer: Out-of-bounds.")
 	}
+	toReturn.sgr2, err = strconv.Atoi(values[4])
+	if err != nil {
+		return nil, fmt.Errorf("Error parsing SGR2 integer: Invalid value.")
+	}
+	if toReturn.sgr2 < 0 || toReturn.sgr2 > 107 {
+		return nil, fmt.Errorf("Error parsing SGR2 integer: Out-of-bounds.")
+	}
+
+	if !(toReturn.red > 0 && toReturn.blue > 0 && toReturn.green > 0) &&
+		!(toReturn.red == -1 && toReturn.green == -1 && toReturn.blue == -1) {
+		return nil, fmt.Errorf("Error parsing color: All values must be positive or -1 for default terminal color.")
+	}
 	return &toReturn, nil
 }
 
 // loadColorsFromFile loads the colors defined in the given config file, and adds them to
 // the possibleColors map. This allows the user to define custom colors at run-time.
 // The colors config file has the following syntax:
-// COLOR: <RED> <GREEN> <BLUE>
+// COLOR: <SGR1> <RED> <GREEN> <BLUE> <SGR2>
 //
 // Note that the color must be capitalized (and not contain spaces), and the R, G and B
-// values must be from 0 to 255.
+// values must be from -1 to 255 (-1 refers to the default terminal color, and all three values
+// must be -1 for this to work).
 func loadColorsFromFile(filepath string) error {
 	data, err := os.ReadFile(filepath)
 	if err != nil {
@@ -151,8 +176,28 @@ func loadColorsFromFile(filepath string) error {
 		// If we haven't returned an error yet, the color must be valid.
 		// Add it to the map. colorData.New() expects values of type colorData.Attribute,
 		// so we must cast our RGB values accordingly.
-		possibleColors[item.Key.(string)] = color{item.Key.(string), colorData.New(38, 2, colorData.Attribute(rgb.red), colorData.Attribute(rgb.blue), colorData.Attribute(rgb.green))}
-
+		// First, check if one of the color values is -1. If it is, they must all be negative (based
+		// on the check in 'stringToRGB()'). If this is the case, don't put the color values.
+		if rgb.red == -1 {
+			possibleColors[item.Key.(string)] = color{
+				item.Key.(string),
+				colorData.New(
+					colorData.Attribute(rgb.sgr2),
+				),
+			}
+		} else {
+			possibleColors[item.Key.(string)] = color{
+				item.Key.(string),
+				colorData.New(
+					colorData.Attribute(rgb.sgr1),
+					2,
+					colorData.Attribute(rgb.red),
+					colorData.Attribute(rgb.blue),
+					colorData.Attribute(rgb.green),
+					colorData.Attribute(rgb.sgr2),
+				),
+			}
+		}
 	}
 
 	return nil