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Configuration Core module.
There is a newer version: 4.1.1
/*
 * Copyright (c) 2020, 2022 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.ArrayList;
import java.util.Arrays;
import java.util.Collections;
import java.util.LinkedList;
import java.util.List;
import java.util.Objects;

/**
 * Implementation of {@link Config.Key Config Key}.
 */
class ConfigKeyImpl implements Config.Key {
    private final String name;
    private final ConfigKeyImpl parent;
    private final List path;
    private final String fullKey;

    private ConfigKeyImpl(ConfigKeyImpl parent, String name) {
        Objects.requireNonNull(name, "name is mandatory");

        if (name.contains(".")) {
            throw new IllegalArgumentException("Illegal key token format. Dot character ('.') is not supported.");
        }

        this.parent = parent;
        List path = new ArrayList<>();
        StringBuilder fullSB = new StringBuilder();
        if (parent != null) {
            path.addAll(parent.path);
            fullSB.append(parent.fullKey);
        }
        if (!name.isEmpty()) {
            if (fullSB.length() > 0) {
                fullSB.append(".");
            }
            path.add(name);
            fullSB.append(name);
        }
        this.name = Config.Key.unescapeName(name);
        this.path = Collections.unmodifiableList(path);
        this.fullKey = fullSB.toString();
    }

    @Override
    public ConfigKeyImpl parent() {
        if (isRoot()) {
            throw new IllegalStateException("Attempting to get parent of a root node. Guard by isRoot instead");
        }
        return parent;
    }

    @Override
    public boolean isRoot() {
        return (null == parent);
    }

    /**
     * Creates new root instance of ConfigKeyImpl.
     *
     * @return new instance of ConfigKeyImpl.
     */
    static ConfigKeyImpl of() {
        return new ConfigKeyImpl(null, "");
    }

    /**
     * Creates new instance of ConfigKeyImpl.
     *
     * @param key key
     * @return new instance of ConfigKeyImpl.
     */
    static ConfigKeyImpl of(String key) {
        return of().child(key);
    }

    /**
     * Creates new child instance of ConfigKeyImpl.
     *
     * @param key sub-key
     * @return new child instance of ConfigKeyImpl.
     */
    ConfigKeyImpl child(String key) {
        return child(Arrays.asList(key.split("\\.")));
    }

    /**
     * Creates new child instance of ConfigKeyImpl.
     *
     * @param key sub-key
     * @return new child instance of ConfigKeyImpl.
     */
    @Override
    public ConfigKeyImpl child(io.helidon.common.config.Config.Key key) {
        final List path;
        if (key instanceof ConfigKeyImpl) {
            path = ((ConfigKeyImpl) key).path;
        } else {
            path = new LinkedList<>();
            while (!key.isRoot()) {
                path.add(0, key.name());
                key = key.parent();
            }
        }
        return child(path);
    }

    private ConfigKeyImpl child(List path) {
        ConfigKeyImpl result = this;
        for (String name : path) {
            if (name.isEmpty()) {
                continue;
            }
            result = new ConfigKeyImpl(result, name);
        }
        return result;
    }

    @Override
    public String name() {
        return name;
    }

    @Override
    public String toString() {
        return fullKey;
    }

    @Override
    public boolean equals(Object o) {
        if (this == o) {
            return true;
        }
        if (!(o instanceof io.helidon.common.config.Config.Key)) {
            return false;
        }
        io.helidon.common.config.Config.Key key = (io.helidon.common.config.Config.Key) o;
        return Objects.equals(name(), key.name())
                && Objects.equals(isRoot(), key.isRoot())
                && (isRoot() || Objects.equals(parent(), key.parent()));
    }

    @Override
    public int hashCode() {
        return Objects.hash(name, parent);
    }

    @Override
    public int compareTo(io.helidon.common.config.Config.Key that) {
        return toString().compareTo(that.toString());
    }

}