/*
 * 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", the "GNU Affero General Public License v3.0 only", 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", the "GNU Affero General Public
 * License v3.0 only", or the "Server Side Public License, v 1".
 */

package org.elasticsearch.action.admin.cluster.stats;

import org.elasticsearch.action.FailedNodeException;
import org.elasticsearch.action.support.TransportAction;
import org.elasticsearch.action.support.nodes.BaseNodesResponse;
import org.elasticsearch.cluster.ClusterName;
import org.elasticsearch.cluster.ClusterSnapshotStats;
import org.elasticsearch.cluster.health.ClusterHealthStatus;
import org.elasticsearch.common.Strings;
import org.elasticsearch.common.io.stream.StreamInput;
import org.elasticsearch.common.io.stream.StreamOutput;
import org.elasticsearch.common.unit.ByteSizeValue;
import org.elasticsearch.xcontent.ToXContentFragment;
import org.elasticsearch.xcontent.XContentBuilder;

import java.io.IOException;
import java.util.List;
import java.util.Locale;
import java.util.Map;
import java.util.Set;

public class ClusterStatsResponse extends BaseNodesResponse<ClusterStatsNodeResponse> implements ToXContentFragment {

    final ClusterStatsNodes nodesStats;
    final ClusterStatsIndices indicesStats;
    final ClusterHealthStatus status;
    final ClusterSnapshotStats clusterSnapshotStats;
    final RepositoryUsageStats repositoryUsageStats;
    final CCSTelemetrySnapshot ccsMetrics;
    final CCSTelemetrySnapshot esqlMetrics;
    final long timestamp;
    final String clusterUUID;
    private final Map<String, RemoteClusterStats> remoteClustersStats;

    public static final String CCS_TELEMETRY_FIELD_NAME = "_search";
    public static final String ESQL_TELEMETRY_FIELD_NAME = "_esql";

    public ClusterStatsResponse(
        long timestamp,
        String clusterUUID,
        ClusterName clusterName,
        List<ClusterStatsNodeResponse> nodes,
        List<FailedNodeException> failures,
        MappingStats mappingStats,
        AnalysisStats analysisStats,
        VersionStats versionStats,
        ClusterSnapshotStats clusterSnapshotStats,
        Map<String, RemoteClusterStats> remoteClustersStats
    ) {
        super(clusterName, nodes, failures);
        this.clusterUUID = clusterUUID;
        this.timestamp = timestamp;
        nodesStats = new ClusterStatsNodes(nodes);
        indicesStats = new ClusterStatsIndices(nodes, mappingStats, analysisStats, versionStats);
        ccsMetrics = new CCSTelemetrySnapshot();
        esqlMetrics = new CCSTelemetrySnapshot().setUseMRT(false);
        ClusterHealthStatus status = null;
        for (ClusterStatsNodeResponse response : nodes) {
            // only the master node populates the status
            if (response.clusterStatus() != null) {
                status = response.clusterStatus();
                break;
            }
        }
        nodes.forEach(node -> {
            ccsMetrics.add(node.getSearchCcsMetrics());
            esqlMetrics.add(node.getEsqlCcsMetrics());
        });
        this.status = status;
        this.clusterSnapshotStats = clusterSnapshotStats;

        this.repositoryUsageStats = nodes.stream()
            .map(ClusterStatsNodeResponse::repositoryUsageStats)
            // only populated on snapshot nodes (i.e. master and data nodes)
            .filter(r -> r.isEmpty() == false)
            // stats should be the same on every node so just pick one of them
            .findAny()
            .orElse(RepositoryUsageStats.EMPTY);
        this.remoteClustersStats = remoteClustersStats;
    }

    public String getClusterUUID() {
        return this.clusterUUID;
    }

    public long getTimestamp() {
        return this.timestamp;
    }

    public ClusterHealthStatus getStatus() {
        return this.status;
    }

    public ClusterStatsNodes getNodesStats() {
        return nodesStats;
    }

    public ClusterStatsIndices getIndicesStats() {
        return indicesStats;
    }

    public CCSTelemetrySnapshot getCcsMetrics() {
        return ccsMetrics;
    }

    public Map<String, RemoteClusterStats> getRemoteClustersStats() {
        return remoteClustersStats;
    }

    @Override
    public void writeTo(StreamOutput out) throws IOException {
        TransportAction.localOnly();
    }

    @Override
    protected List<ClusterStatsNodeResponse> readNodesFrom(StreamInput in) throws IOException {
        return TransportAction.localOnly();
    }

    @Override
    protected void writeNodesTo(StreamOutput out, List<ClusterStatsNodeResponse> nodes) throws IOException {
        TransportAction.localOnly();
    }

    @Override
    public XContentBuilder toXContent(XContentBuilder builder, Params params) throws IOException {
        builder.field("cluster_uuid", getClusterUUID());
        builder.field("timestamp", getTimestamp());
        if (status != null) {
            builder.field("status", status.name().toLowerCase(Locale.ROOT));
        }
        builder.startObject("indices");
        indicesStats.toXContent(builder, params);
        builder.endObject();
        builder.startObject("nodes");
        nodesStats.toXContent(builder, params);
        builder.endObject();

        builder.field("snapshots");
        clusterSnapshotStats.toXContent(builder, params);

        builder.field("repositories");
        repositoryUsageStats.toXContent(builder, params);

        builder.startObject("ccs");
        if (remoteClustersStats != null) {
            builder.field("clusters", remoteClustersStats);
        }
        builder.startObject(CCS_TELEMETRY_FIELD_NAME);
        ccsMetrics.toXContent(builder, params);
        builder.endObject();

        if (esqlMetrics.getTotalCount() > 0) {
            builder.startObject(ESQL_TELEMETRY_FIELD_NAME);
            esqlMetrics.toXContent(builder, params);
            builder.endObject();
        }

        builder.endObject();

        return builder;
    }

    @Override
    public String toString() {
        return Strings.toString(this, true, true);
    }

    /**
     * Represents the information about a remote cluster.
     */
    public record RemoteClusterStats(
        String clusterUUID,
        String mode,
        boolean skipUnavailable,
        String transportCompress,
        Set<String> versions,
        String status,
        long nodesCount,
        long shardsCount,
        long indicesCount,
        long indicesBytes,
        long heapBytes,
        long memBytes
    ) implements ToXContentFragment {
        public RemoteClusterStats(String mode, boolean skipUnavailable, String transportCompress) {
            this(
                "unavailable",
                mode,
                skipUnavailable,
                transportCompress.toLowerCase(Locale.ROOT),
                Set.of(),
                "unavailable",
                0,
                0,
                0,
                0,
                0,
                0
            );
        }

        public RemoteClusterStats acceptResponse(RemoteClusterStatsResponse remoteResponse) {
            return new RemoteClusterStats(
                remoteResponse.getClusterUUID(),
                mode,
                skipUnavailable,
                transportCompress,
                remoteResponse.getVersions(),
                remoteResponse.getStatus().name().toLowerCase(Locale.ROOT),
                remoteResponse.getNodesCount(),
                remoteResponse.getShardsCount(),
                remoteResponse.getIndicesCount(),
                remoteResponse.getIndicesBytes(),
                remoteResponse.getHeapBytes(),
                remoteResponse.getMemBytes()
            );
        }

        @Override
        public XContentBuilder toXContent(XContentBuilder builder, Params params) throws IOException {
            builder.startObject();
            builder.field("cluster_uuid", clusterUUID);
            builder.field("mode", mode);
            builder.field("skip_unavailable", skipUnavailable);
            builder.field("transport.compress", transportCompress);
            builder.field("status", status);
            builder.field("version", versions);
            builder.field("nodes_count", nodesCount);
            builder.field("shards_count", shardsCount);
            builder.field("indices_count", indicesCount);
            builder.humanReadableField("indices_total_size_in_bytes", "indices_total_size", ByteSizeValue.ofBytes(indicesBytes));
            builder.humanReadableField("max_heap_in_bytes", "max_heap", ByteSizeValue.ofBytes(heapBytes));
            builder.humanReadableField("mem_total_in_bytes", "mem_total", ByteSizeValue.ofBytes(memBytes));
            builder.endObject();
            return builder;
        }
    }
}