/*
 * Copyright Elasticsearch B.V. and/or licensed to Elasticsearch B.V. under one
 * or more contributor license agreements. Licensed under the Elastic License
 * 2.0 and the Server Side Public License, v 1; you may not use this file except
 * in compliance with, at your election, the Elastic License 2.0 or the Server
 * Side Public License, v 1.
 */

package org.elasticsearch.repositories.fs;

import org.apache.logging.log4j.LogManager;
import org.apache.logging.log4j.Logger;
import org.elasticsearch.cluster.metadata.RepositoryMetadata;
import org.elasticsearch.cluster.service.ClusterService;
import org.elasticsearch.common.blobstore.BlobPath;
import org.elasticsearch.common.blobstore.BlobStore;
import org.elasticsearch.common.blobstore.fs.FsBlobStore;
import org.elasticsearch.common.settings.Setting;
import org.elasticsearch.common.settings.Setting.Property;
import org.elasticsearch.common.unit.ByteSizeValue;
import org.elasticsearch.common.util.BigArrays;
import org.elasticsearch.common.xcontent.NamedXContentRegistry;
import org.elasticsearch.env.Environment;
import org.elasticsearch.indices.recovery.RecoverySettings;
import org.elasticsearch.repositories.RepositoryException;
import org.elasticsearch.repositories.blobstore.BlobStoreRepository;

import java.nio.file.Path;
import java.util.function.Function;

/**
 * Shared file system implementation of the BlobStoreRepository
 * <p>
 * Shared file system repository supports the following settings
 * <dl>
 * <dt>{@code location}</dt><dd>Path to the root of repository. This is mandatory parameter.</dd>
 * <dt>{@code concurrent_streams}</dt><dd>Number of concurrent read/write stream (per repository on each node). Defaults to 5.</dd>
 * <dt>{@code chunk_size}</dt><dd>Large file can be divided into chunks. This parameter specifies the chunk size.
 *      Defaults to not chucked.</dd>
 * <dt>{@code compress}</dt><dd>If set to true metadata files will be stored compressed. Defaults to false.</dd>
 * </dl>
 */
public class FsRepository extends BlobStoreRepository {
    private static final Logger logger = LogManager.getLogger(FsRepository.class);

    public static final String TYPE = "fs";

    public static final Setting<String> LOCATION_SETTING =
        new Setting<>("location", "", Function.identity(), Property.NodeScope);
    public static final Setting<String> REPOSITORIES_LOCATION_SETTING =
        new Setting<>("repositories.fs.location", LOCATION_SETTING, Function.identity(), Property.NodeScope);
    public static final Setting<ByteSizeValue> CHUNK_SIZE_SETTING = Setting.byteSizeSetting("chunk_size",
            new ByteSizeValue(Long.MAX_VALUE), new ByteSizeValue(5), new ByteSizeValue(Long.MAX_VALUE), Property.NodeScope);
    public static final Setting<ByteSizeValue> REPOSITORIES_CHUNK_SIZE_SETTING = Setting.byteSizeSetting("repositories.fs.chunk_size",
        new ByteSizeValue(Long.MAX_VALUE), new ByteSizeValue(5), new ByteSizeValue(Long.MAX_VALUE), Property.NodeScope);
    public static final Setting<Boolean> COMPRESS_SETTING = Setting.boolSetting("compress", false, Property.NodeScope);
    public static final Setting<Boolean> REPOSITORIES_COMPRESS_SETTING =
        Setting.boolSetting("repositories.fs.compress", false, Property.NodeScope, Property.Deprecated);
    private final Environment environment;

    private ByteSizeValue chunkSize;

    private final BlobPath basePath;

    /**
     * Constructs a shared file system repository.
     */
    public FsRepository(RepositoryMetadata metadata, Environment environment, NamedXContentRegistry namedXContentRegistry,
                        ClusterService clusterService, BigArrays bigArrays, RecoverySettings recoverySettings) {
        super(metadata, calculateCompress(metadata, environment), namedXContentRegistry, clusterService, bigArrays, recoverySettings);
        this.environment = environment;
        String location = REPOSITORIES_LOCATION_SETTING.get(metadata.settings());
        if (location.isEmpty()) {
            logger.warn("the repository location is missing, it should point to a shared file system location"
                + " that is available on all master and data nodes");
            throw new RepositoryException(metadata.name(), "missing location");
        }
        Path locationFile = environment.resolveRepoFile(location);
        if (locationFile == null) {
            if (environment.repoFiles().length > 0) {
                logger.warn("The specified location [{}] doesn't start with any "
                    + "repository paths specified by the path.repo setting: [{}] ", location, environment.repoFiles());
                throw new RepositoryException(metadata.name(), "location [" + location
                    + "] doesn't match any of the locations specified by path.repo");
            } else {
                logger.warn("The specified location [{}] should start with a repository path specified by"
                    + " the path.repo setting, but the path.repo setting was not set on this node", location);
                throw new RepositoryException(metadata.name(), "location [" + location
                    + "] doesn't match any of the locations specified by path.repo because this setting is empty");
            }
        }

        if (CHUNK_SIZE_SETTING.exists(metadata.settings())) {
            this.chunkSize = CHUNK_SIZE_SETTING.get(metadata.settings());
        } else {
            this.chunkSize = REPOSITORIES_CHUNK_SIZE_SETTING.get(environment.settings());
        }
        this.basePath = BlobPath.cleanPath();
    }

    private static boolean calculateCompress(RepositoryMetadata metadata, Environment environment) {
        return COMPRESS_SETTING.exists(metadata.settings())
            ? COMPRESS_SETTING.get(metadata.settings()) : REPOSITORIES_COMPRESS_SETTING.get(environment.settings());
    }

    @Override
    protected BlobStore createBlobStore() throws Exception {
        final String location = REPOSITORIES_LOCATION_SETTING.get(getMetadata().settings());
        final Path locationFile = environment.resolveRepoFile(location);
        return new FsBlobStore(bufferSize, locationFile, isReadOnly());
    }

    @Override
    protected ByteSizeValue chunkSize() {
        return chunkSize;
    }

    @Override
    public BlobPath basePath() {
        return basePath;
    }

    @Override
    public boolean hasAtomicOverwrites() {
        // We overwrite a file by deleting the old file and then renaming the new file into place, which is not atomic.
        // Also on Windows the overwrite may fail if the file is opened for reading at the time.
        return false;
    }
}
