add a new x/sqlx sub-package and example

x/sqlx/util.go

@@ -0,0 +1,42 @@
+package sqlx
+
+import "strings"
+
+// snakeCase converts a given string to a friendly snake case, e.g.
+// - userId to user_id
+// - ID     to id
+// - ProviderAPIKey to provider_api_key
+// - Option to option
+func snakeCase(camel string) string {
+	var (
+		b            strings.Builder
+		prevWasUpper bool
+	)
+
+	for i, c := range camel {
+		if isUppercase(c) { // it's upper.
+			if b.Len() > 0 && !prevWasUpper { // it's not the first and the previous was not uppercased too (e.g  "ID").
+				b.WriteRune('_')
+			} else { // check for XxxAPIKey, it should be written as xxx_api_key.
+				next := i + 1
+				if next > 1 && len(camel)-1 > next {
+					if !isUppercase(rune(camel[next])) {
+						b.WriteRune('_')
+					}
+				}
+			}
+
+			b.WriteRune(c - 'A' + 'a') // write its lowercase version.
+			prevWasUpper = true
+		} else {
+			b.WriteRune(c) // write it as it is, it's already lowercased.
+			prevWasUpper = false
+		}
+	}
+
+	return b.String()
+}
+
+func isUppercase(c rune) bool {
+	return 'A' <= c && c <= 'Z'
+}