// Copyright Yahoo. Licensed under the terms of the Apache 2.0 license. See LICENSE in the project root.
package com.yahoo.vespa.model.application.validation.change;

import com.yahoo.config.application.api.ValidationId;
import com.yahoo.config.model.api.ConfigChangeAction;
import com.yahoo.config.model.deploy.DeployState;
import com.yahoo.config.provision.ClusterResources;
import com.yahoo.config.provision.ClusterSpec;
import com.yahoo.config.provision.NodeResources;
import com.yahoo.vespa.model.VespaModel;

import java.util.List;

/**
 * Checks that no cluster sizes are reduced too much in one go.
 *
 * @author bratseth
 */
public class ResourcesReductionValidator implements ChangeValidator {

    @Override
    public List<ConfigChangeAction> validate(VespaModel current, VespaModel next, DeployState deployState) {
        for (var clusterId : current.allClusters()) {
            if (next.allClusters().contains(clusterId))
                validate(clusterId, current, next, deployState);
        }
        return List.of();
    }

    private void validate(ClusterSpec.Id clusterId,
                          VespaModel currentModel,
                          VespaModel nextModel,
                          DeployState deployState) {
        ClusterResources current = clusterResources(clusterId, currentModel);
        ClusterResources next = clusterResources(clusterId, nextModel);
        if (current == null || next == null) return; // No request recording - test
        if (current.nodeResources().isUnspecified() || next.nodeResources().isUnspecified()) {
            // Self-hosted - unspecified resources; compare node count
            int currentNodes = current.nodes();
            int nextNodes = next.nodes();
            if (nextNodes < 0.5 * currentNodes && nextNodes != currentNodes - 1) {
                deployState.validationOverrides().invalid(ValidationId.resourcesReduction,
                                  "Size reduction in '" + clusterId.value() + "' is too large: " +
                                  "To guard against mistakes, the new max nodes must be at least 50% of the current nodes. " +
                                  "Current nodes: " + currentNodes + ", new nodes: " + nextNodes,
                                  deployState.now());
            }
        }
        else {
            NodeResources currentResources = current.totalResources();
            NodeResources nextResources = next.totalResources();
            if (nextResources.vcpu() < 0.5 * currentResources.vcpu() ||
                nextResources.memoryGb() < 0.5 * currentResources.memoryGb() ||
                nextResources.diskGb() < 0.5 * currentResources.diskGb())
                deployState.validationOverrides().invalid(ValidationId.resourcesReduction,
                                  "Resource reduction in '" + clusterId.value() + "' is too large: " +
                                  "To guard against mistakes, the new max resources must be at least 50% of the current " +
                                  "max resources in all dimensions. " +
                                  "Current: " + currentResources.withBandwidthGbps(0) + // (don't output bandwidth here)
                                  ", new: " + nextResources.withBandwidthGbps(0),
                                  deployState.now());
        }

    }

    /**
     * If the given requested cluster resources does not specify node resources, return them with
     * the current node resources of the cluster, as that is what unspecified resources actually resolved to.
     * This will always yield specified node resources on hosted instances and never on self-hosted instances.
     */
    private ClusterResources clusterResources(ClusterSpec.Id id, VespaModel model) {
        if ( ! model.provisioned().all().containsKey(id)) return null;

        ClusterResources resources = model.provisioned().all().get(id).maxResources();
        if ( ! resources.nodeResources().isUnspecified()) return resources;

        var containerCluster = model.getContainerClusters().get(id.value());
        if (containerCluster != null) {
            if ( ! containerCluster.getContainers().isEmpty())
                return resources.with(containerCluster.getContainers().get(0).getHostResource().advertisedResources());
        }

        var contentCluster = model.getContentClusters().get(id.value());
        if (contentCluster != null) {
            var searchCluster = contentCluster.getSearch();
            if ( ! searchCluster.getSearchNodes().isEmpty())
                return resources.with(searchCluster.getSearchNodes().get(0).getHostResource().advertisedResources());
        }

        return resources; // only expected for admin clusters
    }

}