Implement snake_case

helpers.go

@@ -1,6 +1,7 @@
 package goose
 
 import (
+	"bytes"
 	"strings"
 	"unicode"
 	"unicode/utf8"
@@ -8,16 +9,16 @@ import (
 
 type camelSnakeStateMachine int
 
-const (
-	begin         camelSnakeStateMachine = iota // 0
-	firstAlphaNum                               // 1
-	alphaNum                                    // 2
-	delimiter                                   // 3
+const ( //                                           _$$_This is some text, OK?!
+	idle          camelSnakeStateMachine = iota // 0 ↑                     ↑   ↑
+	firstAlphaNum                               // 1     ↑    ↑  ↑    ↑     ↑
+	alphaNum                                    // 2      ↑↑↑  ↑  ↑↑↑  ↑↑↑   ↑
+	delimiter                                   // 3         ↑  ↑    ↑    ↑   ↑
 )
 
 func (s camelSnakeStateMachine) next(r rune) camelSnakeStateMachine {
 	switch s {
-	case begin:
+	case idle:
 		if isAlphaNum(r) {
 			return firstAlphaNum
 		}
@@ -35,7 +36,7 @@ func (s camelSnakeStateMachine) next(r rune) camelSnakeStateMachine {
 		if isAlphaNum(r) {
 			return firstAlphaNum
 		} else {
-			return begin
+			return idle
 		}
 	}
 	return s
@@ -44,7 +45,7 @@ func (s camelSnakeStateMachine) next(r rune) camelSnakeStateMachine {
 func camelCase(str string) string {
 	var b strings.Builder
 
-	stateMachine := begin
+	stateMachine := idle
 	for i := 0; i < len(str); {
 		r, size := utf8.DecodeRuneInString(str[i:])
 		i += size
@@ -67,6 +68,27 @@ func lowerCamelCase(str string) string {
 	return strings.ToLower(str[:1]) + str[1:]
 }
 
+func snakeCase(str string) string {
+	var b bytes.Buffer
+
+	stateMachine := idle
+	for i := 0; i < len(str); {
+		r, size := utf8.DecodeRuneInString(str[i:])
+		i += size
+		stateMachine = stateMachine.next(r)
+		switch stateMachine {
+		case firstAlphaNum, alphaNum:
+			b.WriteRune(unicode.ToLower(r))
+		case delimiter:
+			b.WriteByte('_')
+		}
+	}
+	if stateMachine == idle {
+		return string(bytes.TrimSuffix(b.Bytes(), []byte{'_'}))
+	}
+	return b.String()
+}
+
 func isAlphaNum(r rune) bool {
 	return unicode.IsLetter(r) || unicode.IsNumber(r)
 }

helpers_test.go

@@ -16,10 +16,10 @@ func TestCamelSnake(t *testing.T) {
 
 	for _, test := range tt {
 		if got := lowerCamelCase(test.in); got != test.camel {
-			t.Errorf("unexpected lower camel for input(%q), got %q, want %q", test.in, got, test.camel)
+			t.Errorf("unexpected lowerCamelCase for input(%q), got %q, want %q", test.in, got, test.camel)
+		}
+		if got := snakeCase(test.in); got != test.snake {
+			t.Errorf("unexpected snake_case for input(%q), got %q, want %q", test.in, got, test.snake)
 		}
-		// if got := snake(test.in); got != test.snake {
-		// 	t.Error("unexpected snake for input(%q), got %q, want %q", test.in, got, test.snake)
-		// }
 	}
 }