tools: implement tools.Rjust([]string{...})

tools/str_tools.go

@@ -1,6 +1,9 @@
 package tools
 
-import "regexp"
+import (
+	"regexp"
+	"strings"
+)
 
 var (
 	// quoteFieldRe greedily matches between matching pairs of '', "", or
@@ -43,6 +46,24 @@ func QuotedFields(s string) []string {
 	return out
 }
 
+// Rjust returns a copied string slice where each element is right justified to
+// match the width of the longest element in the set.
+func Rjust(strs []string) []string {
+	llen := len(Longest(strs))
+
+	dup := make([]string, len(strs), cap(strs))
+	copy(dup, strs)
+
+	for i, str := range strs {
+		width := MaxInt(0, llen-len(str))
+		padding := strings.Repeat(" ", width)
+
+		dup[i] = padding + str
+	}
+
+	return dup
+}
+
 // Longest returns the longest element in the string slice in O(n) time and O(1)
 // space. If strs is empty or nil, an empty string will be returned.
 func Longest(strs []string) string {
@@ -52,7 +73,7 @@ func Longest(strs []string) string {
 
 	var longest string
 	var llen int
-	for _, str := range longest {
+	for _, str := range strs {
 		if len(str) >= llen {
 			longest = str
 			llen = len(longest)

tools/str_tools_test.go

@@ -82,3 +82,18 @@ func TestLongestReturnsLongestString(t *testing.T) {
 func TestLongestReturnsLastStringGivenSameLength(t *testing.T) {
 	assert.Equal(t, "baz", []string{"foo", "bar", "baz"})
 }
+
+func TestRjustRightJustifiesString(t *testing.T) {
+	unjust := []string{
+		"short",
+		"longer",
+		"longest",
+	}
+	expected := []string{
+		"  short",
+		" longer",
+		"longest",
+	}
+
+	assert.Equal(t, expected, Rjust(unjust))
+}