=== Add/Remove user and query capability interfaces

One thing we have not done with our example is allow it to add and remove users or change passwords. Users defined in our example are
also not queryable or viewable in the Admin Console. To add these enhancements, our example provider must implement
the `UserQueryProvider` and `UserRegistrationProvider` interfaces.

==== Implementing UserRegistrationProvider

Use this procedure to implement adding and removing users from the particular store, we first have to be able to save our properties
file to disk.

.PropertyFileUserStorageProvider
[source,java]
----
    public void save() {
        String path = model.getConfig().getFirst("path");
        path = EnvUtil.replace(path);
        try {
            FileOutputStream fos = new FileOutputStream(path);
            properties.store(fos, "");
            fos.close();
        } catch (IOException e) {
            throw new RuntimeException(e);
        }
    }
----

Then, the implementation of the `addUser()` and `removeUser()` methods becomes simple.

.PropertyFileUserStorageProvider
[source,java]
----
    public static final String UNSET_PASSWORD="#$!-UNSET-PASSWORD";

    @Override
    public UserModel addUser(RealmModel realm, String username) {
        synchronized (properties) {
            properties.setProperty(username, UNSET_PASSWORD);
            save();
        }
        return createAdapter(realm, username);
    }

    @Override
    public boolean removeUser(RealmModel realm, UserModel user) {
        synchronized (properties) {
            if (properties.remove(user.getUsername()) == null) return false;
            save();
            return true;
        }
    }
----

Notice that when adding a user we set the password value of the property map to be `UNSET_PASSWORD`.  We do this as
we can't have null values for a property in the property value. We also have to modify the `CredentialInputValidator`
methods to reflect this.

The `addUser()` method will be called if the provider implements the `UserRegistrationProvider` interface. If your provider has
a configuration switch to turn off adding a user, returning `null` from this method will skip the provider and call
the next one.

.PropertyFileUserStorageProvider
[source,java]
----
    @Override
    public boolean isValid(RealmModel realm, UserModel user, CredentialInput input) {
        if (!supportsCredentialType(input.getType()) || !(input instanceof UserCredentialModel)) return false;

        UserCredentialModel cred = (UserCredentialModel)input;
        String password = properties.getProperty(user.getUsername());
        if (password == null || UNSET_PASSWORD.equals(password)) return false;
        return password.equals(cred.getValue());
    }
----

Since we can now save our property file, it also makes sense to allow password updates.

.PropertyFileUserStorageProvider
[source,java]
----
    @Override
    public boolean updateCredential(RealmModel realm, UserModel user, CredentialInput input) {
        if (!(input instanceof UserCredentialModel)) return false;
        if (!input.getType().equals(PasswordCredentialModel.TYPE)) return false;
        UserCredentialModel cred = (UserCredentialModel)input;
        synchronized (properties) {
            properties.setProperty(user.getUsername(), cred.getValue());
            save();
        }
        return true;
    }
----

We can now also implement disabling a password.

.PropertyFileUserStorageProvider
[source,java]
----
    @Override
    public void disableCredentialType(RealmModel realm, UserModel user, String credentialType) {
        if (!credentialType.equals(PasswordCredentialModel.TYPE)) return;
        synchronized (properties) {
            properties.setProperty(user.getUsername(), UNSET_PASSWORD);
            save();
        }

    }

    private static final Set<String> disableableTypes = new HashSet<>();

    static {
        disableableTypes.add(PasswordCredentialModel.TYPE);
    }

    @Override
    public Stream<String> getDisableableCredentialTypes(RealmModel realm, UserModel user) {

        return disableableTypes.stream();
    }
----

With these methods implemented, you'll now be able to change and disable the password for the user in the Admin Console.

==== Implementing UserQueryProvider

Without implementing `UserQueryProvider` the Admin Console would not be able to view and manage users that were loaded
by our example provider. Let's look at implementing this interface.

.PropertyFileUserStorageProvider
[source,java]
----
    @Override
    public int getUsersCount(RealmModel realm) {
        return properties.size();
    }

    @Override
    public Stream<UserModel> searchForUserStream(RealmModel realm, String search, Integer firstResult, Integer maxResults) {
        Predicate<String> predicate = "*".equals(search) ? username -> true : username -> username.contains(search);
        return properties.keySet().stream()
                .map(String.class::cast)
                .filter(predicate)
                .skip(firstResult)
                .map(username -> getUserByUsername(realm, username))
                .limit(maxResults);
    }
----

The first declaration of `searchForUserStream()` takes a `String` parameter. In this example, the parameter represents a username that you want to search by. This string can be a substring, which explains the choice of  the `String.contains()`
method when doing the search. Notice the use of `*` to indicate to request a list of all users.
The method iterates over the key set of the property file, delegating to `getUserByUsername()` to load a user.
Notice that we are indexing this call based on the `firstResult` and `maxResults` parameter. If your external store does not support pagination, you will have to do similar logic.

.PropertyFileUserStorageProvider
[source,java]
----
    @Override
    public Stream<UserModel> searchForUserStream(RealmModel realm, Map<String, String> params, Integer firstResult, Integer maxResults) {
        // only support searching by username
        String usernameSearchString = params.get("username");
        if (usernameSearchString != null)
            return searchForUserStream(realm, usernameSearchString, firstResult, maxResults);

        // if we are not searching by username, return all users
        return searchForUserStream(realm, "*", firstResult, maxResults);
    }
----

The `searchForUserStream()` method that takes a `Map` parameter can search for a user based on first, last name, username, and email.
Only usernames are stored, so the search is based only on usernames except when the `Map` parameter does not contain the `username` attribute.
In this case, all users are returned. In that situation, the `searchForUserStream(realm, search, firstResult, maxResults)` is used.


.PropertyFileUserStorageProvider
[source,java]
----
    @Override
    public Stream<UserModel> getGroupMembersStream(RealmModel realm, GroupModel group, Integer firstResult, Integer maxResults) {
        return Stream.empty();
    }

    @Override
    public Stream<UserModel> searchForUserByUserAttributeStream(RealmModel realm, String attrName, String attrValue) {
        return Stream.empty();
    }
----

Groups or attributes are not stored, so the other methods return an empty stream.