feat: Validate string format 'email'

Author: thced

src/main/java/com/retailsvc/http/validate/DefaultValidator.java

@@ -43,11 +43,14 @@ public final class DefaultValidator implements Validator {
 
   private record FormatCheck(Predicate<String> isValid, String message) {}
 
+  private static final Pattern EMAIL = Pattern.compile("^[^\\s@]+@[^\\s@]+\\.[^\\s@]+$");
+
   private static final Map<String, FormatCheck> FORMAT_CHECKS =
       Map.of(
           "uuid", new FormatCheck(DefaultValidator::isUuid, "not a valid uuid"),
           "date", new FormatCheck(DefaultValidator::isDate, "not a valid date"),
-          "date-time", new FormatCheck(DefaultValidator::isDateTime, "not a valid date-time"));
+          "date-time", new FormatCheck(DefaultValidator::isDateTime, "not a valid date-time"),
+          "email", new FormatCheck(s -> EMAIL.matcher(s).matches(), "not a valid email"));
 
   private final Function<String, Schema> refResolver;
   private final ConcurrentMap<String, Pattern> compiledPatterns = new ConcurrentHashMap<>();

src/test/java/com/retailsvc/http/validate/StringIntegerNumberTest.java

@@ -67,6 +67,18 @@ void stringFormatUuid() {
         .isEqualTo("format");
   }
 
+  @Test
+  void stringFormatEmail() {
+    StringSchema s = new StringSchema(Set.of(TypeName.STRING), null, null, null, "email", null);
+    assertThatCode(() -> v.validate("user@example.com", s, "/v")).doesNotThrowAnyException();
+    assertThatThrownBy(() -> v.validate("not-an-email", s, "/v"))
+        .extracting(t -> ((ValidationException) t).error().keyword())
+        .isEqualTo("format");
+    assertThatThrownBy(() -> v.validate("missing@dot", s, "/v"))
+        .extracting(t -> ((ValidationException) t).error().keyword())
+        .isEqualTo("format");
+  }
+
   @Test
   void integerWithMinMax() {
     IntegerSchema s =