/*
 * SPDX-License-Identifier: Apache-2.0
 *
 * The OpenSearch Contributors require contributions made to
 * this file be licensed under the Apache-2.0 license or a
 * compatible open source license.
 */

/*
 * Licensed to Elasticsearch under one or more contributor
 * license agreements. See the NOTICE file distributed with
 * this work for additional information regarding copyright
 * ownership. Elasticsearch licenses this file to you 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.
 */

/*
 * Modifications Copyright OpenSearch Contributors. See
 * GitHub history for details.
 */

package org.opensearch.client;

import java.util.Iterator;
import java.util.List;
import java.util.Map;
import java.util.Objects;

/**
 * Both {@link PreferHasAttributeNodeSelector} and {@link HasAttributeNodeSelector} will work the same
 * if there is a {@link Node} with particular attribute in the attributes,
 * but {@link PreferHasAttributeNodeSelector} will select another {@link Node}s even if there is no {@link Node}
 * with particular attribute in the attributes.
 */
public final class PreferHasAttributeNodeSelector implements NodeSelector {
    private final String key;
    private final String value;

    /**
     * Creates a {@link PreferHasAttributeNodeSelector} instance with the given key value pair.
     *
     * @param key attribute key
     * @param value attribute value
     */
    public PreferHasAttributeNodeSelector(String key, String value) {
        this.key = key;
        this.value = value;
    }

    /**
     * Select the {@link Node}s to which to send requests.
     * @param nodes the {@link Node}s targeted for the sending requests
     */
    @Override
    public void select(Iterable<Node> nodes) {
        boolean foundAtLeastOne = false;

        for (Node node : nodes) {
            Map<String, List<String>> attributes = node.getAttributes();

            if (attributes == null) {
                continue;
            }

            List<String> values = attributes.get(key);

            if (values == null) {
                continue;
            }

            if (values.contains(value)) {
                foundAtLeastOne = true;
                break;
            }
        }

        if (foundAtLeastOne) {
            Iterator<Node> nodeIterator = nodes.iterator();
            while (nodeIterator.hasNext()) {
                Map<String, List<String>> attributes = nodeIterator.next().getAttributes();

                if (attributes == null) {
                    continue;
                }

                List<String> values = attributes.get(key);

                if (values == null || !values.contains(value)) {
                    nodeIterator.remove();
                }
            }
        }
    }

    /**
     * Compare two node selectors for equality
     * @param o node selector instance to compare with
     */
    @Override
    public boolean equals(Object o) {
        if (this == o) {
            return true;
        }
        if (o == null || getClass() != o.getClass()) {
            return false;
        }
        PreferHasAttributeNodeSelector that = (PreferHasAttributeNodeSelector) o;
        return Objects.equals(key, that.key) && Objects.equals(value, that.value);
    }

    /**
     * Calculate the hash code of the node selector
     */
    @Override
    public int hashCode() {
        return Objects.hash(key, value);
    }

    /**
     * Convert this node selector to string representation
     */
    @Override
    public String toString() {
        return key + "=" + value;
    }
}
