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/*
* Copyright 2014 Dominik Foerderreuther 
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package de.eleon.console.builder;

import com.google.common.base.Function;
import com.google.common.base.Optional;

import static com.google.common.base.Optional.fromNullable;

/**
 * Extend AskBuilder to answer with an Optional.
 */
public class AnswerOptional {

    private final AskBuilder askBuilder;

    AnswerOptional(AskBuilder askBuilder) {
        this.askBuilder = askBuilder;
    }

    /**
     * Return user input
     *
     * @return user input as Optional
     */
    public Optional answer() {
        return optionalOf(askBuilder.answer());
    }

    /**
     * Return user input as Optional
     *
     * @param function {@link com.google.common.base.Function} or {@link de.eleon.console.builder.functional.Transformer} for value conversion
     * @param  the return type
     * @return user input as Optional
     */
    public  Optional answer(Function function) {
        return fromNullable(askBuilder.answer(function));
    }

    /**
     * Return user input as Optional
     *
     * @param function {@link Function} or {@link de.eleon.console.builder.functional.Transformer} for value conversion
     * @param validationErrorMessage error message if function conversion fails
     * @param  the return type
     * @return user input as Optional
     */
    public  Optional answer(Function function, final String validationErrorMessage) {
        return fromNullable(askBuilder.answer(function, validationErrorMessage));
    }

    /**
     * Return user input as Optional>. Complete with enum values.
     *
     * @param enumClass Class of enum to return
     * @param  the return type
     * @return user input as enum value
     */
    public > Optional answer(final Class enumClass) {
        return fromNullable(askBuilder.answer(enumClass));
    }

    /**
     * Return user input as Optional>. Complete with enum values.
     *
     * @param enumClass Class of enum to return
     * @param validationErrorMessage error message if enum conversion fails
     * @param  the return type
     * @return user input as enum value
     */
    public > Optional answer(final Class enumClass, final String validationErrorMessage) {
        return fromNullable(askBuilder.answer(enumClass, validationErrorMessage));
    }

    private Optional optionalOf(String answer) {
        if (answer.trim().isEmpty()) return Optional.absent();
        return Optional.of(answer);
    }

}