Add email validation

src/main/java/it/aboutbits/springboot/testing/validation/core/BaseRuleBuilder.java

@@ -1,6 +1,7 @@
 package it.aboutbits.springboot.testing.validation.core;
 
 import it.aboutbits.springboot.testing.validation.rule.BetweenRule;
+import it.aboutbits.springboot.testing.validation.rule.EmailRule;
 import it.aboutbits.springboot.testing.validation.rule.FutureRule;
 import it.aboutbits.springboot.testing.validation.rule.MaxRule;
 import it.aboutbits.springboot.testing.validation.rule.MinRule;
@@ -35,6 +36,7 @@
 public abstract class BaseRuleBuilder<R extends BaseRuleBuilder<R>> implements
         ValidationRulesData,
         BetweenRule<R>,
+        EmailRule<R>,
         FutureRule<R>,
         MaxRule<R>,
         MinRule<R>,

src/main/java/it/aboutbits/springboot/testing/validation/rule/EmailRule.java

@@ -0,0 +1,22 @@
+package it.aboutbits.springboot.testing.validation.rule;
+
+import com.google.errorprone.annotations.CheckReturnValue;
+import it.aboutbits.springboot.testing.validation.core.BaseRuleBuilder;
+import it.aboutbits.springboot.testing.validation.core.Rule;
+import it.aboutbits.springboot.testing.validation.core.ValidationRulesData;
+import it.aboutbits.springboot.testing.validation.source.InvalidEmailValueSource;
+import org.jspecify.annotations.NullMarked;
+
+@SuppressWarnings("unchecked")
+@NullMarked
+public interface EmailRule<V extends BaseRuleBuilder<?>> extends ValidationRulesData {
+    /// Bean validation considers `null` and blank values to be valid e-mail addresses.
+    /// Combine this rule with `notNull` or `notBlank` if the property must be present.
+    @CheckReturnValue
+    default V email(String property) {
+        addRule(
+                new Rule(property, InvalidEmailValueSource.class)
+        );
+        return (V) this;
+    }
+}

src/main/java/it/aboutbits/springboot/testing/validation/source/InvalidEmailValueSource.java

@@ -0,0 +1,47 @@
+package it.aboutbits.springboot.testing.validation.source;
+
+import it.aboutbits.springboot.testing.validation.core.ValueSource;
+import org.jspecify.annotations.NullMarked;
+import org.jspecify.annotations.Nullable;
+
+import java.util.HashMap;
+import java.util.Map;
+import java.util.function.Function;
+import java.util.stream.Stream;
+
+@NullMarked
+public class InvalidEmailValueSource implements ValueSource {
+    private static final Map<Class<?>, Function<Object[], Stream<?>>> TYPE_SOURCES = new HashMap<>();
+
+    static {
+        TYPE_SOURCES.put(
+                String.class,
+                (Object[] args) -> Stream.of(
+                        "plainaddress",
+                        "@example.com",
+                        "someone@",
+                        "someone@@example.com",
+                        "some one@example.com",
+                        "someone@exam ple.com",
+                        "someone@example..com",
+                        "someone@.example.com"
+                )
+        );
+    }
+
+    @SuppressWarnings("unused")
+    public static void registerType(Class<?> type, Function<Object[], Stream<?>> source) {
+        TYPE_SOURCES.put(type, source);
+    }
+
+    @Override
+    @SuppressWarnings("unchecked")
+    public <T> Stream<@Nullable T> values(Class<T> propertyClass, Object... args) {
+        var sourceFunction = TYPE_SOURCES.get(propertyClass);
+        if (sourceFunction != null) {
+            return (Stream<@Nullable T>) sourceFunction.apply(args);
+        }
+
+        throw new IllegalArgumentException("Property class not supported!");
+    }
+}

src/test/java/it/aboutbits/springboot/testing/validation/ValidationAssertTest.java

@@ -6,6 +6,7 @@
 import it.aboutbits.springboot.toolbox.type.ScaledBigDecimal;
 import it.aboutbits.springboot.toolbox.validation.annotation.ValidPassword;
 import jakarta.validation.Valid;
+import jakarta.validation.constraints.Email;
 import jakarta.validation.constraints.Future;
 import jakarta.validation.constraints.Max;
 import jakarta.validation.constraints.Min;
@@ -188,6 +189,11 @@ public record SomeValidParameter(
             @ValidPassword
             String password,
 
+            // Email
+            @Email String email,
+            @Email @Nullable String nullableEmail,
+            @Email @NotBlank String requiredEmail,
+
             // Not validated
             Object notValidated
     ) {
@@ -333,6 +339,13 @@ void testWithBeanValidation() {
                 // ValidPassword
                 .validPassword("password", 8, 50)
 
+                // Email
+                .email("email")
+                .email("nullableEmail")
+                .nullable("nullableEmail")
+                .email("requiredEmail")
+                .notBlank("requiredEmail")
+
                 // Not validated
                 .notValidated("notValidated")
                 .isCompliant();
@@ -476,6 +489,13 @@ void invalidParameter_shouldFail() {
                         // ValidPassword
                         .validPassword("password", 8, 50)
 
+                        // Email
+                        .email("email")
+                        .email("nullableEmail")
+                        .nullable("nullableEmail")
+                        .email("requiredEmail")
+                        .notBlank("requiredEmail")
+
                         // Not validated
                         .notValidated("notValidated")
                         .isCompliant());
@@ -620,6 +640,13 @@ void propertyMissingRule_shouldFail() {
                         // ValidPassword
                         .validPassword("password", 8, 50)
 
+                        // Email
+                        .email("email")
+                        .email("nullableEmail")
+                        .nullable("nullableEmail")
+                        .email("requiredEmail")
+                        .notBlank("requiredEmail")
+
                         // Not validated
                         .notValidated("notValidated")
                         .isCompliant());
@@ -922,6 +949,11 @@ private static SomeValidParameter getSomeValidParameter() {
                 // ValidPassword
                 "password123",
 
+                // Email
+                "someone@example.com",
+                null,
+                "required@example.com",
+
                 // Not validated
                 null
         );