// Copyright 2017 Yahoo Holdings. Licensed under the terms of the Apache 2.0 license. See LICENSE in the project root.
package com.yahoo.config.provision.serialization;

import com.yahoo.config.provision.AllocatedHosts;
import com.yahoo.config.provision.ClusterMembership;
import com.yahoo.config.provision.DockerImage;
import com.yahoo.config.provision.HostSpec;
import com.yahoo.config.provision.NodeResources;
import com.yahoo.slime.ArrayTraverser;
import com.yahoo.slime.Cursor;
import com.yahoo.slime.Inspector;
import com.yahoo.slime.Slime;
import com.yahoo.slime.SlimeUtils;

import java.io.IOException;
import java.util.ArrayList;
import java.util.LinkedHashSet;
import java.util.List;
import java.util.Optional;
import java.util.Set;

/**
 * The hosts allocated to an application.
 * This can be serialized to/from JSON.
 * This is immutable.
 *
 * @author Ulf Lilleengen
 * @author bratseth
 */
public class AllocatedHostsSerializer {

    // WARNING: Since there are multiple servers in a ZooKeeper cluster and they upgrade one by one
    //          (and rewrite all nodes on startup), changes to the serialized format must be made
    //          such that what is serialized on version N+1 can be read by version N:
    //          - ADDING FIELDS: Always ok
    //          - REMOVING FIELDS: Stop reading the field first. Stop writing it on a later version.
    //          - CHANGING THE FORMAT OF A FIELD: Don't do it bro.

    private static final String mappingKey = "mapping";
    private static final String hostSpecKey = "hostSpec";
    private static final String hostSpecHostNameKey = "hostName";
    private static final String aliasesKey = "aliases";
    private static final String hostSpecMembershipKey = "membership";

    private static final String realResourcesKey = "realResources";
    private static final String advertisedResourcesKey = "advertisedResources";

    // Flavor can be removed when all allocated nodes are docker nodes
    private static final String flavorKey = "flavor";

    private static final String resourcesKey = "resources";
    private static final String requestedResourcesKey = "requestedResources";
    private static final String vcpuKey = "vcpu";
    private static final String memoryKey = "memory";
    private static final String diskKey = "disk";
    private static final String bandwidthKey = "bandwidth";
    private static final String diskSpeedKey = "diskSpeed";
    private static final String storageTypeKey = "storageType";

    /** Wanted version */
    private static final String hostSpecVespaVersionKey = "vespaVersion";

    /** Wanted docker image repo */
    private static final String hostSpecDockerImageRepoKey = "dockerImageRepo";

    /** Current version */
    private static final String hostSpecCurrentVespaVersionKey = "currentVespaVersion";
    private static final String hostSpecNetworkPortsKey = "ports";


    public static byte[] toJson(AllocatedHosts allocatedHosts) throws IOException {
        Slime slime = new Slime();
        toSlime(allocatedHosts, slime.setObject());
        return SlimeUtils.toJsonBytes(slime);
    }

    public static void toSlime(AllocatedHosts allocatedHosts, Cursor cursor) {
        Cursor array = cursor.setArray(mappingKey);
        for (HostSpec host : allocatedHosts.getHosts())
            toSlime(host, array.addObject().setObject(hostSpecKey));
    }

    private static void toSlime(HostSpec host, Cursor object) {
        object.setString(hostSpecHostNameKey, host.hostname());
        aliasesToSlime(host, object);
        host.membership().ifPresent(membership -> {
            object.setString(hostSpecMembershipKey, membership.stringValue());
            object.setString(hostSpecVespaVersionKey, membership.cluster().vespaVersion().toFullString());
            membership.cluster().dockerImageRepo().ifPresent(repo -> {
                object.setString(hostSpecDockerImageRepoKey, repo.repository());
            });
        });
        toSlime(host.realResources(), object.setObject(realResourcesKey));
        toSlime(host.advertisedResources(), object.setObject(advertisedResourcesKey));
        host.requestedResources().ifPresent(resources -> toSlime(resources, object.setObject(requestedResourcesKey)));
        host.version().ifPresent(version -> object.setString(hostSpecCurrentVespaVersionKey, version.toFullString()));
        host.networkPorts().ifPresent(ports -> NetworkPortsSerializer.toSlime(ports, object.setArray(hostSpecNetworkPortsKey)));
    }

    private static void aliasesToSlime(HostSpec spec, Cursor cursor) {
        if (spec.aliases().isEmpty()) return;
        Cursor aliases = cursor.setArray(aliasesKey);
        for (String alias : spec.aliases())
            aliases.addString(alias);
    }

    private static void toSlime(NodeResources resources, Cursor resourcesObject) {
        resourcesObject.setDouble(vcpuKey, resources.vcpu());
        resourcesObject.setDouble(memoryKey, resources.memoryGb());
        resourcesObject.setDouble(diskKey, resources.diskGb());
        resourcesObject.setDouble(bandwidthKey, resources.bandwidthGbps());
        resourcesObject.setString(diskSpeedKey, diskSpeedToString(resources.diskSpeed()));
        resourcesObject.setString(storageTypeKey, storageTypeToString(resources.storageType()));
    }

    public static AllocatedHosts fromJson(byte[] json) {
        return fromSlime(SlimeUtils.jsonToSlime(json).get());
    }

    public static AllocatedHosts fromSlime(Inspector inspector) {
        Inspector array = inspector.field(mappingKey);
        Set<HostSpec> hosts = new LinkedHashSet<>();
        array.traverse((ArrayTraverser)(i, host) -> {
            hosts.add(hostFromSlime(host.field(hostSpecKey)));
        });
        return AllocatedHosts.withHosts(hosts);
    }

    private static HostSpec hostFromSlime(Inspector object) {

        if (object.field(hostSpecMembershipKey).valid()) { // Hosted
            return new HostSpec(object.field(hostSpecHostNameKey).asString(),
                                nodeResourcesFromSlime(object.field(realResourcesKey)),
                                nodeResourcesFromSlime(object.field(advertisedResourcesKey)),
                                optionalNodeResourcesFromSlime(object.field(requestedResourcesKey)), // TODO: Make non-optional when we serialize NodeResources.unspecified()
                                membershipFromSlime(object),
                                optionalString(object.field(hostSpecCurrentVespaVersionKey)).map(com.yahoo.component.Version::new),
                                NetworkPortsSerializer.fromSlime(object.field(hostSpecNetworkPortsKey)),
                                optionalDockerImage(object.field(hostSpecDockerImageRepoKey)));
        }
        else {
            return new HostSpec(object.field(hostSpecHostNameKey).asString(),
                                aliasesFromSlime(object),
                                NetworkPortsSerializer.fromSlime(object.field(hostSpecNetworkPortsKey)));
        }
    }

    private static List<String> aliasesFromSlime(Inspector object) {
        if ( ! object.field(aliasesKey).valid()) return List.of();
        List<String> aliases = new ArrayList<>();
        object.field(aliasesKey).traverse((ArrayTraverser)(index, alias) -> aliases.add(alias.asString()));
        return aliases;
    }

    private static NodeResources nodeResourcesFromSlime(Inspector resources) {
        return new NodeResources(resources.field(vcpuKey).asDouble(),
                                 resources.field(memoryKey).asDouble(),
                                 resources.field(diskKey).asDouble(),
                                 resources.field(bandwidthKey).asDouble(),
                                 diskSpeedFromSlime(resources.field(diskSpeedKey)),
                                 storageTypeFromSlime(resources.field(storageTypeKey)));
    }

    private static NodeResources optionalNodeResourcesFromSlime(Inspector resources) {
        if ( ! resources.valid()) return NodeResources.unspecified();
        return nodeResourcesFromSlime(resources);
    }

    private static NodeResources.DiskSpeed diskSpeedFromSlime(Inspector diskSpeed) {
        switch (diskSpeed.asString()) {
            case "fast" : return NodeResources.DiskSpeed.fast;
            case "slow" : return NodeResources.DiskSpeed.slow;
            case "any" : return NodeResources.DiskSpeed.any;
            default: throw new IllegalStateException("Illegal disk-speed value '" + diskSpeed.asString() + "'");
        }
    }

    private static String diskSpeedToString(NodeResources.DiskSpeed diskSpeed) {
        switch (diskSpeed) {
            case fast : return "fast";
            case slow : return "slow";
            case any : return "any";
            default: throw new IllegalStateException("Illegal disk-speed value '" + diskSpeed + "'");
        }
    }

    private static NodeResources.StorageType storageTypeFromSlime(Inspector storageType) {
        switch (storageType.asString()) {
            case "remote" : return NodeResources.StorageType.remote;
            case "local" : return NodeResources.StorageType.local;
            case "any" : return NodeResources.StorageType.any;
            default: throw new IllegalStateException("Illegal storage-type value '" + storageType.asString() + "'");
        }
    }

    private static String storageTypeToString(NodeResources.StorageType storageType) {
        switch (storageType) {
            case remote : return "remote";
            case local : return "local";
            case any : return "any";
            default: throw new IllegalStateException("Illegal storage-type value '" + storageType + "'");
        }
    }

    private static ClusterMembership membershipFromSlime(Inspector object) {
        return ClusterMembership.from(object.field(hostSpecMembershipKey).asString(),
                                      com.yahoo.component.Version.fromString(object.field(hostSpecVespaVersionKey).asString()),
                                      object.field(hostSpecDockerImageRepoKey).valid()
                                              ? Optional.of(DockerImage.fromString(object.field(hostSpecDockerImageRepoKey).asString()))
                                              : Optional.empty());
    }

    private static Optional<String> optionalString(Inspector inspector) {
        if ( ! inspector.valid()) return Optional.empty();
        return Optional.of(inspector.asString());
    }

    private static Optional<DockerImage> optionalDockerImage(Inspector inspector) {
        if ( ! inspector.valid()) return Optional.empty();
        return Optional.of(DockerImage.fromString(inspector.asString()));
    }

}