com.github.jknack.handlebars.helper.NumberHelper.java Source code

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Here is the source code for com.github.jknack.handlebars.helper.NumberHelper.java

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/**
 * Copyright (c) 2012-2013 Edgar Espina
 *
 * This file is part of Handlebars.java.
 *
 * 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 com.github.jknack.handlebars.helper;

import static org.apache.commons.lang3.Validate.notNull;

import java.io.IOException;

import com.github.jknack.handlebars.Handlebars;
import com.github.jknack.handlebars.Helper;
import com.github.jknack.handlebars.Options;

/**
 * Commons number function helpers.
 *
 * @author https://github.com/Jarlakxen
 */
public enum NumberHelper implements Helper<Object> {

    /**
     * You can use the isEven helper to return a value only if the first argument
     * is even. Otherwise return null.
     *
     * <li class="{{isEven value "leftBox"}}">
     *
     * If value is 2, the output will be "leftBox".
     *
     */
    isEven {
        @Override
        public CharSequence safeApply(final Number value, final Options options) {
            return isEven(value) ? options.param(0, "even") : null;
        }
    },

    /**
     * You can use the isOdd helper to return a value only if the first argument
     * is odd. Otherwise return null.
     *
     * <li class="{{isOdd value "rightBox"}}">
     *
     * If value is 3, the output will be "rightBox".
     *
     */
    isOdd {
        @Override
        public CharSequence safeApply(final Number value, final Options options) {
            return !isEven(value) ? options.param(0, "odd") : null;
        }
    },

    /**
     * You can use the stripes helper to return different value if the passed
     * argument is odd or even.
     *
     * <tr class="{{stripes value "row-even" "row-odd"}}">
     *
     * If value is 2, the output will be "row-even".
     *
     */
    stripes {
        @Override
        public CharSequence safeApply(final Number value, final Options options) {
            return isEven(value) ? options.param(0, "even") : options.param(1, "odd");
        }
    };

    @Override
    public CharSequence apply(final Object context, final Options options) throws IOException {
        if (context instanceof Number) {
            return safeApply((Number) context, options);
        }
        return null;
    }

    /**
     * Apply the helper to the context.
     *
     * @param value
     *        The context object (param=0).
     * @param options
     *        The options object.
     * @return A string result.
     */
    protected abstract CharSequence safeApply(final Number value, final Options options);

    /**
     * Apply the helper to the context.
     *
     * @param value
     *        The number value.
     * @return true is even, false is odd
     */
    protected boolean isEven(final Number value) {
        return value.intValue() % 2 == 0;
    }

    /**
     * Register the helper in a handlebars instance.
     *
     * @param handlebars
     *        A handlebars object. Required.
     */
    public void registerHelper(final Handlebars handlebars) {
        notNull(handlebars, "The handlebars is required.");
        handlebars.registerHelper(this.name(), this);
    }

    /**
     * Register all the number helpers.
     *
     * @param handlebars
     *        The helper's owner. Required.
     */
    public static void register(final Handlebars handlebars) {
        notNull(handlebars, "A handlebars object is required.");
        NumberHelper[] helpers = values();
        for (NumberHelper helper : helpers) {
            helper.registerHelper(handlebars);
        }
    }
}