feat: Validate string format 'regex'

Author: thced

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

@@ -38,6 +38,7 @@
 import java.util.function.Function;
 import java.util.function.Predicate;
 import java.util.regex.Pattern;
+import java.util.regex.PatternSyntaxException;
 
 public final class DefaultValidator implements Validator {
 
@@ -84,7 +85,8 @@ private record FormatCheck(Predicate<String> isValid, String message) {}
               "hostname",
               new FormatCheck(s -> HOSTNAME.matcher(s).matches(), "not a valid hostname")),
           Map.entry("ipv4", new FormatCheck(s -> IPV4.matcher(s).matches(), "not a valid ipv4")),
-          Map.entry("ipv6", new FormatCheck(s -> IPV6.matcher(s).matches(), "not a valid ipv6")));
+          Map.entry("ipv6", new FormatCheck(s -> IPV6.matcher(s).matches(), "not a valid ipv6")),
+          Map.entry("regex", new FormatCheck(DefaultValidator::isRegex, "not a valid regex")));
 
   private final Function<String, Schema> refResolver;
   private final ConcurrentMap<String, Pattern> compiledPatterns = new ConcurrentHashMap<>();
@@ -200,6 +202,15 @@ private static boolean isUri(String s) {
     }
   }
 
+  private static boolean isRegex(String s) {
+    try {
+      Pattern.compile(s);
+      return true;
+    } catch (PatternSyntaxException _) {
+      return false;
+    }
+  }
+
   private static boolean isUriReference(String s) {
     try {
       new URI(s);

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

@@ -187,6 +187,16 @@ void numberAcceptsDoublesAndIntegers() {
         .isEqualTo("maximum");
   }
 
+  @Test
+  void stringFormatRegex() {
+    StringSchema s = new StringSchema(Set.of(TypeName.STRING), null, null, null, "regex", null);
+    assertThatCode(() -> v.validate("^[a-z]+$", s, "/v")).doesNotThrowAnyException();
+    assertThatCode(() -> v.validate("\\d{3}-\\d{4}", s, "/v")).doesNotThrowAnyException();
+    assertThatThrownBy(() -> v.validate("[invalid", s, "/v"))
+        .extracting(t -> ((ValidationException) t).error().keyword())
+        .isEqualTo("format");
+  }
+
   @Test
   void stringRejectsNonString() {
     StringSchema s = new StringSchema(Set.of(TypeName.STRING), null, null, null, null, null);