Whoops forgot new files

app/src/main/java/it/chalmers/gamma/adapter/primary/web/ValidatedWith.java

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+package it.chalmers.gamma.adapter.primary.web;
+
+import static java.lang.annotation.ElementType.FIELD;
+import static java.lang.annotation.RetentionPolicy.RUNTIME;
+
+import it.chalmers.gamma.app.validation.Validator;
+import java.lang.annotation.Retention;
+import java.lang.annotation.Target;
+
+@Retention(RUNTIME)
+@Target(FIELD)
+public @interface ValidatedWith {
+  Class<? extends Validator<?>> value();
+}

app/src/main/java/it/chalmers/gamma/adapter/primary/web/WebValidationHelper.java

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+package it.chalmers.gamma.adapter.primary.web;
+
+import it.chalmers.gamma.app.validation.FailedValidation;
+import it.chalmers.gamma.app.validation.ValidationResult;
+import it.chalmers.gamma.app.validation.Validator;
+import java.lang.reflect.Field;
+import java.lang.reflect.InvocationTargetException;
+import org.springframework.validation.BindingResult;
+import org.springframework.validation.FieldError;
+
+public class WebValidationHelper {
+
+  public static void validateObject(Object obj, BindingResult bindingResult) {
+    Field[] fields = obj.getClass().getDeclaredFields();
+    for (Field field : fields) {
+      ValidatedWith validatedWith = field.getAnnotation(ValidatedWith.class);
+      if (validatedWith != null) {
+        field.setAccessible(true);
+        try {
+          Validator<Object> validator =
+              (Validator<Object>) validatedWith.value().getDeclaredConstructor().newInstance();
+          Object fieldValue = field.get(obj);
+          ValidationResult validationResult = validator.validate(fieldValue);
+          if (validationResult instanceof FailedValidation failedValidation) {
+            bindingResult.addError(
+                new FieldError(
+                    "form",
+                    field.getName(),
+                    fieldValue,
+                    true,
+                    null,
+                    null,
+                    failedValidation.message()));
+          }
+        } catch (NoSuchMethodException
+            | InstantiationException
+            | IllegalAccessException
+            | InvocationTargetException e) {
+          throw new RuntimeException(e);
+        }
+      }
+    }
+  }
+}

app/src/main/java/it/chalmers/gamma/app/validation/FailedValidation.java

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+package it.chalmers.gamma.app.validation;
+
+public record FailedValidation(String message) implements ValidationResult {}

app/src/main/java/it/chalmers/gamma/app/validation/SuccessfulValidation.java

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+package it.chalmers.gamma.app.validation;
+
+public record SuccessfulValidation() implements ValidationResult {}

app/src/main/java/it/chalmers/gamma/app/validation/ValidationHelper.java

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+package it.chalmers.gamma.app.validation;
+
+import java.util.function.Function;
+import org.springframework.web.util.HtmlUtils;
+
+public class ValidationHelper {
+
+  @SafeVarargs
+  public static <T> Validator<T> withValidators(Validator<T>... validators) {
+    return value -> {
+      for (Validator<T> validator : validators) {
+        if (validator.validate(value) instanceof FailedValidation failedValidation) {
+          return failedValidation;
+        }
+      }
+
+      return new SuccessfulValidation();
+    };
+  }
+
+  public static Validator<String> IS_NOT_EMPTY =
+      value -> result(!(value == null || value.isEmpty()), "Cannot be empty");
+
+  public static Validator<String> SANITIZED_HTML =
+      value ->
+          result(
+              value.equals(HtmlUtils.htmlEscape(value, "UTF-8")),
+              "Cannot have illegal html characters");
+
+  public static Function<Integer, Validator<String>> MAX_LENGTH =
+      (maxLength) ->
+          value -> result(value.length() <= maxLength, "Must be between 1 and " + maxLength);
+
+  public static Function<Integer, Validator<String>> MIN_LENGTH =
+      (minLength) -> value -> result(value.length() >= minLength, "Must be at least " + minLength);
+
+  public static ValidationResult result(boolean valid, String message) {
+    if (valid) {
+      return new SuccessfulValidation();
+    } else {
+      return new FailedValidation(message);
+    }
+  }
+
+  public static <T> void throwIfFailed(ValidationResult validationResult) {
+    if (validationResult instanceof FailedValidation failedValidation) {
+      throw new IllegalArgumentException(failedValidation.message());
+    }
+  }
+}

app/src/main/java/it/chalmers/gamma/app/validation/ValidationResult.java

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+package it.chalmers.gamma.app.validation;
+
+public sealed interface ValidationResult permits FailedValidation, SuccessfulValidation {}

app/src/main/java/it/chalmers/gamma/app/validation/Validator.java

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+package it.chalmers.gamma.app.validation;
+
+public interface Validator<T> {
+  ValidationResult validate(T value);
+}

app/src/main/resources/templates/common/content-too-large.html

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+<th:block th:replace="~{common/alert :: error('File is larger than 2MB')}"/>

app/src/main/resources/templates/home/failed-to-edit-me-avatar.html

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+<th:block th:replace="common/alert ::error('Failed to upload avatar. Is it a JPG, GIF or PNG?')"></th:block>