Add "ansi" package and "ansi.Colorize" function for quickly highlighting code strings

ansi/ansi.go

@@ -0,0 +1,67 @@
+package ansi
+
+import (
+	"errors"
+	"strings"
+
+	"github.com/rwinkhart/go-highlite"
+	"github.com/rwinkhart/go-highlite/syntax"
+)
+
+// Colorize takes a string of code and a language ID, and returns the code
+// with ANSI color codes applied for syntax highlighting.
+func Colorize(inputCode, languageID string) (string, error) {
+	// Load and parse the go syntax layer into a `*highlight.Def`
+	syntaxDef, err := highlite.ParseDef(syntax.Get(languageID))
+	if err != nil {
+		return "", errors.New("unable to parse syntax layer: " + err.Error())
+	}
+
+	// Make a new highlighter from the definition
+	h := highlite.NewHighlighter(syntaxDef)
+
+	// Highlight the string
+	matches := h.HighlightString(inputCode)
+
+	// We split the string into a bunch of lines
+	lines := strings.Split(inputCode, "\n")
+	var outputString strings.Builder
+
+	for lineN, l := range lines {
+		colN := 0
+		for _, c := range l {
+			if group, ok := matches[lineN][colN]; ok {
+				var colorCode string
+				switch group {
+				case highlite.Groups["statement"], highlite.Groups["green"]:
+					colorCode = "\033[32m" // Green
+				case highlite.Groups["identifier"], highlite.Groups["blue"]:
+					colorCode = "\033[94m" // Bright Blue
+				case highlite.Groups["preproc"]:
+					colorCode = "\033[91m" // Bright Red
+				case highlite.Groups["special"], highlite.Groups["red"]:
+					colorCode = "\033[31m" // Red
+				case highlite.Groups["constant.string"], highlite.Groups["constant"],
+					highlite.Groups["constant.number"], highlite.Groups["cyan"]:
+					colorCode = "\033[36m" // Cyan
+				case highlite.Groups["constant.specialChar"], highlite.Groups["magenta"]:
+					colorCode = "\033[95m" // Bright Magenta
+				case highlite.Groups["type"], highlite.Groups["yellow"]:
+					colorCode = "\033[33m" // Yellow
+				case highlite.Groups["comment"], highlite.Groups["high.green"]:
+					colorCode = "\033[92m" // Bright Green
+				default:
+					colorCode = "\033[0m" // Reset
+				}
+				outputString.WriteString(colorCode)
+			}
+			outputString.WriteRune(c)
+			colN++
+		}
+		outputString.WriteString("\033[0m") // Reset colors at end of line
+		if lineN < len(lines)-1 {           // Don't add newline after last line
+			outputString.WriteRune('\n')
+		}
+	}
+	return outputString.String(), nil
+}