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/*
 * Copyright (c) 2013, Francis Galiegue 
 *
 * This program is free software: you can redistribute it and/or modify
 * it under the terms of the Lesser GNU General Public License as
 * published by the Free Software Foundation, either version 3 of the
 * License, or (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * Lesser GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program.  If not, see .
 */

package com.github.fge.jsonschema.util;

import com.fasterxml.jackson.databind.JsonNode;
import com.fasterxml.jackson.databind.node.JsonNodeFactory;
import com.github.fge.jsonschema.processing.Processor;
import com.github.fge.jsonschema.report.MessageProvider;
import com.github.fge.jsonschema.report.ProcessingMessage;
import net.jcip.annotations.Immutable;

/**
 * A wrapper over an arbitrary type to be used by processors
 *
 * Since all inputs and outputs of a {@link Processor} need to implement
 * {@link MessageProvider}, this abstract class helps to wrap values and
 * implement this interface at the same time.
 *
 * Implementations need only implement the {@link #valueAsJson()} method.
 *
 * @param  the type of the value
 */
@Immutable
public abstract class ValueHolder
    implements MessageProvider
{
    protected static final JsonNodeFactory FACTORY = JacksonUtils.nodeFactory();

    private final String name;
    protected final T value;

    /**
     * Protected constructor
     *
     * @param name the name to prefix the value with
     * @param value the value
     */
    protected ValueHolder(final String name, final T value)
    {
        this.name = name;
        this.value = value;
    }

    /**
     * Return a JSON representation of the value
     *
     * @return a {@link JsonNode}
     */
    protected abstract JsonNode valueAsJson();

    /**
     * Get the value wrapped in the instance
     *
     * @return the value
     */
    public final T getValue()
    {
        return value;
    }

    /**
     * Create a new processing message template depending on the stored value
     *
     * @return a new {@link ProcessingMessage}
     */
    @Override
    public final ProcessingMessage newMessage()
    {
        return new ProcessingMessage().put(name, valueAsJson());
    }
}