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(Re)Aggregates host level statistics across clusters and writes both host and cluster statistics to various destinations.
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/*
 * Copyright 2014 Groupon.com
 *
 * 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.arpnetworking.configuration.jackson;

import com.arpnetworking.commons.builder.OvalBuilder;
import com.arpnetworking.commons.jackson.databind.ObjectMapperFactory;
import com.arpnetworking.logback.annotations.LogValue;
import com.arpnetworking.steno.LogValueMapFactory;
import com.fasterxml.jackson.databind.JsonNode;
import com.fasterxml.jackson.databind.ObjectMapper;
import net.sf.oval.constraint.NotNull;

import java.util.Optional;
import java.util.function.Function;

/**
 * Abstract base class for JsonSource implementations.
 *
 * @author Ville Koskela (ville dot koskela at inscopemetrics dot com)
 */
public abstract class BaseJsonNodeSource implements JsonNodeSource {

    /**
     * Generate a Steno log compatible representation.
     *
     * @return Steno log compatible representation.
     */
    @LogValue
    public Object toLogValue() {
        return LogValueMapFactory.builder(this)
                .put("objectMapper", _objectMapper)
                .build();
    }

    @Override
    public String toString() {
        return toLogValue().toString();
    }

    /**
     * Find the JsonNode if one exists from a specified root node
     * given a sequence of keys to look-up.
     *
     * @param node The root JsonNode.
     * @param keys The sequence of keys to search for.
     * @return The Optional JsonNode instance.
     */
    protected static Optional getValue(final Optional node, final String... keys) {
        JsonNode jsonNode = node.orElse(null);
        for (final String key : keys) {
            if (jsonNode == null) {
                break;
            }
            jsonNode = jsonNode.get(key);
        }
        return Optional.ofNullable(jsonNode);
    }

    /**
     * Protected constructor.
     *
     * @param builder Instance of Builder.
     */
    protected BaseJsonNodeSource(final Builder builder) {
        _objectMapper = builder._objectMapper;
    }

    protected final ObjectMapper _objectMapper;

    /**
     * Builder for BaseJsonNodeSource.
     *
     * @param  type of the builder
     * @param  type of the object to be built
     */
    protected abstract static class Builder, S extends JsonNodeSource> extends OvalBuilder {

        /**
         * Protected constructor for subclasses.
         *
         * @param targetConstructor The constructor for the concrete type to be created by this builder.
         */
        @SuppressWarnings(value = {"rawtypes", "unchecked"})
        protected Builder(final Function targetConstructor) {
            super((Function) targetConstructor);
        }

        /**
         * Set the ObjectMapper instance. Optional. Default is
         * created by ObjectMapperFactory. Cannot be null.
         *
         * @param value The ObjectMapper instance.
         * @return This Builder instance.
         */
        public T setObjectMapper(final ObjectMapper value) {
            _objectMapper = value;
            return self();
        }

        /**
         * Called by setters to always return appropriate subclass of
         * Builder, even from setters of base class.
         *
         * @return instance with correct Builder class type.
         */
        protected abstract T self();

        @NotNull
        protected ObjectMapper _objectMapper = ObjectMapperFactory.getInstance();
    }
}