feat(undent): add initial implementation of String, Stringf, and Bytes

undent.go

@@ -0,0 +1,73 @@
+// Package undent removes leading indentation/white-space from strings and byte
+// slices.
+package undent
+
+import (
+	"fmt"
+	"regexp"
+)
+
+var matcher = regexp.MustCompile(`(?m)^([ \t]*)(?:\S)`)
+
+// Bytes removes leading indentation/white-space from given byte slice.
+func Bytes(b []byte) []byte {
+	matches := matcher.FindAll(b, -1)
+	if len(matches) == 0 {
+		return b
+	}
+
+	index := 0
+	length := len(matches[0])
+
+	for i, s := range matches[1:] {
+		l := len(s)
+		if l < length {
+			index = i + 1
+			length = l
+		}
+	}
+
+	if length <= 1 {
+		return b
+	}
+	indent := matches[index][0 : length-1]
+
+	return regexp.MustCompile(
+		`(?m)^`+regexp.QuoteMeta(string(indent)),
+	).ReplaceAllLiteral(b, []byte{})
+}
+
+// String removes leading indentation/white-space from given string.
+func String(s string) string {
+	matches := matcher.FindAllString(s, -1)
+	if len(matches) == 0 {
+		return s
+	}
+
+	index := 0
+	length := len(matches[0])
+
+	for i, s := range matches[1:] {
+		l := len(s)
+		if l < length {
+			index = i + 1
+			length = l
+		}
+	}
+
+	if length <= 1 {
+		return s
+	}
+	indent := matches[index][0 : length-1]
+
+	return regexp.MustCompile(
+		`(?m)^`+regexp.QuoteMeta(indent),
+	).ReplaceAllLiteralString(s, "")
+}
+
+// Stringf removes leading indentation/white-space from given format string
+// before passing format and all additional arguments to fmt.Sprintf, returning
+// the result.
+func Stringf(format string, a ...interface{}) string {
+	return fmt.Sprintf(String(format), a...)
+}