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Configuration Core module.
There is a newer version: 4.1.1
/*
 * Copyright (c) 2020 Oracle and/or its affiliates.
 *
 * 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 io.helidon.config;

import java.util.AbstractList;
import java.util.HashSet;
import java.util.List;
import java.util.Optional;
import java.util.Set;
import java.util.function.Function;

import io.helidon.config.spi.ConfigNode;
import io.helidon.config.spi.ConfigNode.ListNode;

import static io.helidon.config.AbstractNodeBuilderImpl.formatFrom;

/**
 * Implements {@link ListNode}.
 */
class ListNodeImpl extends AbstractList implements ListNode, MergeableNode {

    private final List elements;
    private String description;
    private final String value;

    ListNodeImpl(List elements, String value) {
        this.elements = elements;
        this.description = null;
        this.value = value;
    }

    /**
     * Wraps list node into mergeable list node.
     *
     * @param listNode original node
     * @return new instance of mergeable node or original node if already was mergeable.
     */
    static ListNodeImpl wrap(ListNode listNode, Function resolveTokenFunction) {
        if (listNode instanceof ListNodeImpl) {
            return (ListNodeImpl) listNode;
        }
        return ListNodeBuilderImpl.from(listNode)
                .value(listNode.value())
                .build();
    }

    @Override
    public MergeableNode get(int index) {
        return elements.get(index);
    }

    @Override
    public int size() {
        return elements.size();
    }

    @Override
    public MergeableNode merge(MergeableNode node) {
        switch (node.nodeType()) {
        case OBJECT:
            return mergeWithObject((ObjectNodeImpl) node);
        case LIST:
            return mergeWithList((ListNodeImpl) node);
        case VALUE:
            return new ListNodeImpl(elements, ((ValueNodeImpl) node).get());
        default:
            throw new IllegalArgumentException("Unsupported node type: " + node.getClass().getName());
        }
    }

    private MergeableNode mergeWithList(ListNodeImpl node) {
        if (node.hasValue()) {
            return node;
        }

        if (hasValue()) {
            return new ListNodeImpl(node.elements, value);
        }

        return node;
    }

    /**
     * Merges list with specified object.
     *
     * @param node object node to be merged with
     * @return new instance of node that contains merged list and object
     */
    private MergeableNode mergeWithObject(ObjectNodeImpl node) {
        Set unprocessedPeerNames = new HashSet<>(node.keySet());

        final ListNodeBuilderImpl builder = new ListNodeBuilderImpl(Function.identity());

        if (node.hasValue()) {
            builder.value(node.value());
        } else if (hasValue()) {
            builder.value(value);
        }

        for (int i = 0; i < elements.size(); i++) {
            MergeableNode element = elements.get(i);
            String name = String.valueOf(i);
            if (unprocessedPeerNames.contains(name)) {
                unprocessedPeerNames.remove(name);
                element = element.merge((MergeableNode) node.get(name));
            }
            builder.addNode(element);
        }
        if (!unprocessedPeerNames.isEmpty()) {
            throw new ConfigException(
                    String.format("Cannot merge OBJECT members %s%s with an LIST node%s.",
                                  unprocessedPeerNames,
                                  formatFrom(node.description()),
                                  formatFrom(description)));
        } else {
            return builder.build();
        }
    }

    @Override
    public String toString() {
        return "ListNode[" + elements.size() + "]" + super.toString() + "=" + value;
    }

    /**
     * Initialize diagnostics description of source of node instance.
     *
     * @param description diagnostics description
     * @return this instance
     */
    public ListNodeImpl initDescription(String description) {
        this.description = description;
        elements.forEach(node -> ObjectNodeImpl.initDescription(node, description));
        return this;
    }

    public String description() {
        return description;
    }

    @Override
    public boolean hasValue() {
        return null != value;
    }

    @Override
    public Optional value() {
        return Optional.ofNullable(value);
    }
}