Add enum const generation

- Make postgres name its enums
- Add way to filter columns by whether or not they're an enum
- Split parsing of enums into name & values
- Add strmangle check functions: IsEnumNormal, ShouldTitleCaseEnum
- Add new strmangle enum functions to template test
- Implement a set type called "once" inside the templates so that we can
  ensure certain things only generate one time via some unique name.

strmangle/strmangle.go

@@ -17,7 +17,9 @@ var (
 	idAlphabet    = []byte("abcdefghijklmnopqrstuvwxyz")
 	smartQuoteRgx = regexp.MustCompile(`^(?i)"?[a-z_][_a-z0-9]*"?(\."?[_a-z][_a-z0-9]*"?)*(\.\*)?$`)
 
-	rgxEnum = regexp.MustCompile(`^enum\((,?'[^']+')+\)$`)
+	rgxEnum            = regexp.MustCompile(`^enum(\.[a-z_]+)?\((,?'[^']+')+\)$`)
+	rgxEnumIsOK        = regexp.MustCompile(`^(?i)[a-z][a-z0-9_]*$`)
+	rgxEnumShouldTitle = regexp.MustCompile(`^[a-z][a-z0-9_]*$`)
 )
 
 var uppercaseWords = map[string]struct{}{
@@ -577,15 +579,54 @@ func GenerateIgnoreTags(tags []string) string {
 	return buf.String()
 }
 
-// ParseEnum takes a string that looks like:
-// enum('one','two') and returns the strings one, two
-func ParseEnum(s string) []string {
+// ParseEnumVals returns the values from an enum string
+//
+// Postgres and MySQL drivers return different values
+// psql:  enum.enum_name('values'...)
+// mysql: enum('values'...)
+func ParseEnumVals(s string) []string {
 	if !rgxEnum.MatchString(s) {
 		return nil
 	}
 
-	s = strings.TrimPrefix(s, "enum('")
-	s = strings.TrimSuffix(s, "')")
-
+	startIndex := strings.IndexByte(s, '(')
+	s = s[startIndex+2 : len(s)-2]
 	return strings.Split(s, "','")
 }
+
+// ParseEnumName returns the name portion of an enum if it exists
+//
+// Postgres and MySQL drivers return different values
+// psql:  enum.enum_name('values'...)
+// mysql: enum('values'...)
+// In the case of mysql, the name will never return anything
+func ParseEnumName(s string) string {
+	if !rgxEnum.MatchString(s) {
+		return ""
+	}
+
+	endIndex := strings.IndexByte(s, '(')
+	s = s[:endIndex]
+	startIndex := strings.IndexByte(s, '.')
+	if startIndex < 0 {
+		return ""
+	}
+
+	return s[startIndex+1:]
+}
+
+// IsEnumNormal checks a set of eval values to see if they're "normal"
+func IsEnumNormal(values []string) bool {
+	for _, v := range values {
+		if !rgxEnumIsOK.MatchString(v) {
+			return false
+		}
+	}
+
+	return true
+}
+
+// ShouldTitleCaseEnum checks a value to see if it's title-case-able
+func ShouldTitleCaseEnum(value string) bool {
+	return rgxEnumShouldTitle.MatchString(value)
+}