Added function to load colors from a config file

color.go

@@ -2,8 +2,12 @@ package main
 
 import (
 	"fmt"
+	"os"
+	"strconv"
+	"strings"
 
 	colorData "github.com/fatih/color"
+	"gopkg.in/yaml.v2"
 )
 
 // A color represents a possible color, which text can be printed out in.
@@ -14,6 +18,14 @@ type color struct {
 	colorObj *colorData.Color
 }
 
+// A RGB represents a Red, Blue, Green trio of values. Each value is represented as
+// an int.
+type RGB struct {
+	red   int
+	blue  int
+	green int
+}
+
 // The following is a list of all possible colors, stored in a map.
 var possibleColors map[string]color = map[string]color{
 	"BLACK":   {"BLACK", colorData.New(colorData.FgBlack)},
@@ -59,3 +71,89 @@ func newColorMust(colorString string) color {
 		return clr
 	}
 }
+
+// isValidColorName returns true if the given string only contains uppercase alphabetic
+// characters.
+func isValidColorName(colorName string) bool {
+	for _, ch := range colorName {
+		if ch > 'Z' || ch < 'A' {
+			return false
+		}
+	}
+	return true
+}
+
+// stringToRGB takes a string representing an RGB trio. 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.
+func stringToRGB(rgbString string) (*RGB, error) {
+	values := strings.Split(rgbString, " ")
+	// There must be three space-separated strings.
+	if len(values) != 3 {
+		// 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.")
+	}
+	// 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])
+	if err != nil {
+		return nil, fmt.Errorf("Error parsing RED integer: Invalid value.")
+	}
+	if toReturn.red < 0 || toReturn.red > 255 {
+		return nil, fmt.Errorf("Error parsing RED integer: Out-of-bounds.")
+	}
+	toReturn.blue, err = strconv.Atoi(values[1])
+	if err != nil {
+		return nil, fmt.Errorf("Error parsing BLUE integer: Invalid value.")
+	}
+	if toReturn.blue < 0 || toReturn.blue > 255 {
+		return nil, fmt.Errorf("Error parsing BLUE integer: Out-of-bounds.")
+	}
+	toReturn.green, err = strconv.Atoi(values[2])
+	if err != nil {
+		return nil, fmt.Errorf("Error parsing GREEN integer: Invalid value.")
+	}
+	if toReturn.green < 0 || toReturn.green > 255 {
+		return nil, fmt.Errorf("Error parsing GREEN integer: Out-of-bounds.")
+	}
+	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>
+//
+// Note that the color must be capitalized (and not contain spaces), and the R, G and B
+// values must be from 0 to 255.
+func loadColorsFromFile(filepath string) error {
+	data, err := os.ReadFile(filepath)
+	if err != nil {
+		panic(err)
+	}
+	// Read color config file into a MapSlice
+	tempMapSlice := yaml.MapSlice{}
+	if err := yaml.Unmarshal(data, &tempMapSlice); err != nil {
+		return fmt.Errorf("Unable to read color config file: %s", filepath)
+	}
+
+	for _, item := range tempMapSlice {
+		if !(isValidColorName(item.Key.(string))) {
+			return fmt.Errorf("Invalid color name: %s", item.Key.(string))
+		}
+		var rgb *RGB
+		if rgb, err = stringToRGB(item.Value.(string)); err != nil {
+			return fmt.Errorf("Invalid RGB trio: %s", item.Value.(string))
+		}
+		// 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))}
+
+	}
+
+	return nil
+}