/*
 * 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.index.shard;

import org.opensearch.cluster.metadata.IndexMetadata;
import org.opensearch.cluster.routing.AllocationId;
import org.opensearch.common.Nullable;
import org.opensearch.core.xcontent.XContentBuilder;
import org.opensearch.core.xcontent.XContentParser;
import org.opensearch.common.xcontent.XContentType;
import org.opensearch.gateway.CorruptStateException;
import org.opensearch.gateway.MetadataStateFormat;

import java.io.IOException;
import java.io.OutputStream;
import java.util.Objects;

/**
 * Metadata string a shard state
 *
 * @opensearch.internal
 */
public final class ShardStateMetadata {

    private static final String SHARD_STATE_FILE_PREFIX = "state-";
    private static final String PRIMARY_KEY = "primary";
    private static final String INDEX_UUID_KEY = "index_uuid";
    private static final String ALLOCATION_ID_KEY = "allocation_id";
    private static final String INDEX_DATA_LOCATION_KEY = "index_data_location";

    /**
     * Enumeration of types of data locations for an index
     */
    public enum IndexDataLocation {
        /**
         * Indicates index data is on the local disk
         */
        LOCAL,
        /**
         * Indicates index data is remote, such as for a searchable snapshot
         * index
         */
        REMOTE
    }

    public final String indexUUID;
    public final boolean primary;
    @Nullable
    public final AllocationId allocationId; // can be null if we read from legacy format (see fromXContent and MultiDataPathUpgrader)
    public final IndexDataLocation indexDataLocation;

    public ShardStateMetadata(boolean primary, String indexUUID, AllocationId allocationId) {
        this(primary, indexUUID, allocationId, IndexDataLocation.LOCAL);
    }

    public ShardStateMetadata(boolean primary, String indexUUID, AllocationId allocationId, IndexDataLocation indexDataLocation) {
        assert indexUUID != null;
        this.primary = primary;
        this.indexUUID = indexUUID;
        this.allocationId = allocationId;
        this.indexDataLocation = Objects.requireNonNull(indexDataLocation);
    }

    @Override
    public boolean equals(Object o) {
        if (this == o) {
            return true;
        }
        if (o == null || getClass() != o.getClass()) {
            return false;
        }

        ShardStateMetadata that = (ShardStateMetadata) o;

        if (primary != that.primary) {
            return false;
        }
        if (indexUUID.equals(that.indexUUID) == false) {
            return false;
        }
        if (Objects.equals(allocationId, that.allocationId) == false) {
            return false;
        }
        if (Objects.equals(indexDataLocation, that.indexDataLocation) == false) {
            return false;
        }

        return true;
    }

    @Override
    public int hashCode() {
        int result = indexUUID.hashCode();
        result = 31 * result + (allocationId != null ? allocationId.hashCode() : 0);
        result = 31 * result + (primary ? 1 : 0);
        result = 31 * result + indexDataLocation.hashCode();
        return result;
    }

    @Override
    public String toString() {
        return "primary [" + primary + "], allocation [" + allocationId + "], index data location [" + indexDataLocation + "]";
    }

    public static final MetadataStateFormat<ShardStateMetadata> FORMAT = new MetadataStateFormat<>(SHARD_STATE_FILE_PREFIX) {

        @Override
        protected XContentBuilder newXContentBuilder(XContentType type, OutputStream stream) throws IOException {
            XContentBuilder xContentBuilder = super.newXContentBuilder(type, stream);
            xContentBuilder.prettyPrint();
            return xContentBuilder;
        }

        @Override
        public void toXContent(XContentBuilder builder, ShardStateMetadata shardStateMetadata) throws IOException {
            builder.field(PRIMARY_KEY, shardStateMetadata.primary);
            builder.field(INDEX_UUID_KEY, shardStateMetadata.indexUUID);
            if (shardStateMetadata.allocationId != null) {
                builder.field(ALLOCATION_ID_KEY, shardStateMetadata.allocationId);
            }
            // Omit the index data location field if it is LOCAL (the implicit default)
            // to maintain compatibility for local indices
            if (shardStateMetadata.indexDataLocation != IndexDataLocation.LOCAL) {
                builder.field(INDEX_DATA_LOCATION_KEY, shardStateMetadata.indexDataLocation);
            }
        }

        @Override
        public ShardStateMetadata fromXContent(XContentParser parser) throws IOException {
            XContentParser.Token token = parser.nextToken();
            if (token == null) {
                return null;
            }
            Boolean primary = null;
            String currentFieldName = null;
            String indexUUID = IndexMetadata.INDEX_UUID_NA_VALUE;
            AllocationId allocationId = null;
            IndexDataLocation indexDataLocation = IndexDataLocation.LOCAL;
            while ((token = parser.nextToken()) != XContentParser.Token.END_OBJECT) {
                if (token == XContentParser.Token.FIELD_NAME) {
                    currentFieldName = parser.currentName();
                } else if (token.isValue()) {
                    if (PRIMARY_KEY.equals(currentFieldName)) {
                        primary = parser.booleanValue();
                    } else if (INDEX_UUID_KEY.equals(currentFieldName)) {
                        indexUUID = parser.text();
                    } else if (INDEX_DATA_LOCATION_KEY.equals(currentFieldName)) {
                        final String stringValue = parser.text();
                        try {
                            indexDataLocation = IndexDataLocation.valueOf(stringValue);
                        } catch (IllegalArgumentException e) {
                            throw new CorruptStateException("unexpected value for data location [" + stringValue + "]");
                        }
                    } else {
                        throw new CorruptStateException("unexpected field in shard state [" + currentFieldName + "]");
                    }
                } else if (token == XContentParser.Token.START_OBJECT) {
                    if (ALLOCATION_ID_KEY.equals(currentFieldName)) {
                        allocationId = AllocationId.fromXContent(parser);
                    } else {
                        throw new CorruptStateException("unexpected object in shard state [" + currentFieldName + "]");
                    }
                } else {
                    throw new CorruptStateException("unexpected token in shard state [" + token.name() + "]");
                }
            }
            if (primary == null) {
                throw new CorruptStateException("missing value for [primary] in shard state");
            }
            return new ShardStateMetadata(primary, indexUUID, allocationId, indexDataLocation);
        }
    };
}