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public class LoginPresenterImpl implements LoginContract.Presenter {

    public static final String TAG = LoginPresenterImpl.class.getSimpleName();

    @NonNull
    private ApiService apiService;
    private LoginContract.View loginView;


    public LoginPresenterImpl(LoginContract.View loginView) {
        this.loginView = loginView;
        loginView.setPresenter(this);
    }

    @Override
    public void start() {

    }

    @Override
    public void login(final String username, final String password) {
        if (false == isUsernameValid(username)) {
            return;
        }
        if (false == isPasswordValid(password)) {
            return;
        }

        // todo: uncomment when back end will be available
        //requestLogin(username, password);
        fakeLogin(username, password);
    }

    private boolean isUsernameValid(String username) {
        if (TextUtils.isEmpty(username)) {
            loginView.showUsernameValidationError(R.string.validation_error_empty_field);
            return false;
        }
        return true;
    }

    private boolean isPasswordValid(String password) {
        if (TextUtils.isEmpty(password)) {
            loginView.showPasswordValidationError(R.string.validation_error_empty_field);
            return false;
        }
        if (password.length() < 8) {
            loginView.showPasswordValidationError(R.string.validation_error_to_few_chars);
            return false;
        }
        if (false == isPasswordMatchesPattern(password)) {
            loginView.showPasswordValidationError(R.string.validation_error_do_not_use_special_chars);
            return false;
        }
        return true;
    }

    private boolean isPasswordMatchesPattern(String password) {
        // only alphabeticals or digits, no special chars
        final String pattern = "^[a-zA-Z0-9]*$";
        return password.matches(pattern);
    }

    private void requestLogin(String username, String password) {
        LogUtil.d(TAG, "requestLogin: " + username + ", " + password);

        loginView.showProgress(true);

        // Initialize the city endpoint
        apiService = new RetrofitHelper().getLoginService();

        apiService.login(username, password).enqueue(new Callback<LoginResponse>() {
            @Override
            public void onResponse(Call<LoginResponse> call, Response<LoginResponse> response) {
                LogUtil.d(TAG, "onResponse: " + response);

                String token = null;
                try {
                    JSONObject jsonObject = new JSONObject(response.body().toString());
                    token = jsonObject.getString("token");
                } catch (JSONException e) {
                    e.printStackTrace();
                }
                loginView.showProgress(false);

                // todo: save token to prefs
                loginView.onLoginSuccess();
            }

            @Override
            public void onFailure(Call<LoginResponse> call, Throwable t) {
                LogUtil.d(TAG, "onFailure");

                loginView.showProgress(false);
                loginView.onLoginError(t.getMessage());
            }
        });
    }


    private void fakeLogin(String username, String password) {
        loginView.showProgress(true);

        new Handler().postDelayed(new Runnable() {
            @Override
            public void run() {
                loginView.showProgress(false);
                onFakeSuccess();
            }
        }, 3000);
    }

    private void onFakeSuccess() {
        loginView.onLoginSuccess();
    }
}