make sure emails are unique

src/main/java/com/commafeed/backend/dao/UserDAO.java

@@ -6,6 +6,8 @@ import javax.persistence.TypedQuery;
 import javax.persistence.criteria.CriteriaQuery;
 import javax.persistence.criteria.Root;
 
+import org.apache.commons.lang3.StringUtils;
+
 import com.commafeed.backend.model.User;
 import com.commafeed.backend.model.User_;
 
@@ -45,6 +47,9 @@ public class UserDAO extends GenericDAO<User> {
 	}
 
 	public User findByEmail(String email) {
+		if (StringUtils.isBlank(email)) {
+			return null;
+		}
 		CriteriaQuery<User> query = builder.createQuery(getType());
 		Root<User> root = query.from(getType());
 		query.where(builder.equal(root.get(User_.email), email));

src/main/java/com/commafeed/frontend/pages/PasswordRecoveryCallbackPage.java

@@ -66,7 +66,7 @@ public class PasswordRecoveryCallbackPage extends BasePage {
 					userDAO.update(user);
 					info("Password saved.");
 				} else {
-					error("Password do not match");
+					error("Passwords do not match.");
 				}
 			}
 		};

src/main/java/com/commafeed/frontend/pages/components/RegisterPanel.java

@@ -98,7 +98,18 @@ public class RegisterPanel extends Panel {
 			protected String getInputType() {
 				return "email";
 			}
-		}.add(RfcCompliantEmailAddressValidator.getInstance()));
+		}.add(RfcCompliantEmailAddressValidator.getInstance()).add(
+				new IValidator<String>() {
+					@Override
+					public void validate(IValidatable<String> validatable) {
+						String email = validatable.getValue();
+						User user = userDAO.findByEmail(email);
+						if (user != null) {
+							validatable.error(new ValidationError(
+									"Email is already taken."));
+						}
+					}
+				}));
 		form.add(new CheckBox("import", MF.m(model, p.isGoogleImport())));
 
 	}

src/main/java/com/commafeed/frontend/rest/resources/UserREST.java

@@ -108,6 +108,15 @@ public class UserREST extends AbstractResourceREST {
 	public Response save(
 			@ApiParam(required = true) ProfileModificationRequest request) {
 		User user = getUser();
+
+		Preconditions.checkArgument(StringUtils.isBlank(request.getPassword())
+				|| request.getPassword().length() >= 6);
+		if (StringUtils.isNotBlank(request.getEmail())) {
+			User u = userDAO.findByEmail(request.getEmail());
+			Preconditions.checkArgument(u == null
+					|| user.getId().equals(u.getId()));
+		}
+
 		if (StartupBean.USERNAME_DEMO.equals(user.getName())) {
 			return Response.status(Status.UNAUTHORIZED).build();
 		}