// Copyright Vespa.ai. Licensed under the terms of the Apache 2.0 license. See LICENSE in the project root.

package com.yahoo.vespa.config.server;

import com.yahoo.component.annotation.Inject;
import com.yahoo.cloud.config.ConfigserverConfig;
import com.yahoo.config.model.api.ApplicationInfo;
import com.yahoo.config.model.api.SuperModel;
import com.yahoo.config.model.api.SuperModelListener;
import com.yahoo.config.model.api.SuperModelProvider;
import com.yahoo.config.provision.ApplicationId;
import com.yahoo.config.provision.Zone;
import com.yahoo.vespa.config.GenerationCounter;
import com.yahoo.vespa.config.server.application.ApplicationVersions;
import com.yahoo.vespa.config.server.model.SuperModelConfigProvider;
import com.yahoo.vespa.flags.FlagSource;

import java.time.Instant;
import java.util.ArrayList;
import java.util.List;
import java.util.Optional;
import java.util.Set;
import java.util.logging.Level;
import java.util.logging.Logger;

/**
 * Provides a SuperModel - a model of all application instances,  and makes it stays
 * up to date as applications are added, redeployed, and removed.
 */
public class SuperModelManager implements SuperModelProvider {
    private static final Logger logger = Logger.getLogger(SuperModelManager.class.getName());

    private final Zone zone;

    private final Object monitor = new Object();
    private final FlagSource flagSource;
    private SuperModelConfigProvider superModelConfigProvider;  // Guarded by 'this' monitor
    private final List<SuperModelListener> listeners = new ArrayList<>();  // Guarded by 'this' monitor

    // Generation of the super model
    private long generation;
    private final long masterGeneration; // ConfigserverConfig's generation
    private final GenerationCounter generationCounter;

    // The initial set of applications to be deployed on bootstrap.
    private final Optional<Set<ApplicationId>> bootstrapApplicationSet = Optional.empty();

    @Inject
    public SuperModelManager(ConfigserverConfig configserverConfig,
                             Zone zone,
                             GenerationCounter generationCounter,
                             FlagSource flagSource) {
        this.flagSource = flagSource;
        this.zone = zone;
        this.generationCounter = generationCounter;
        this.masterGeneration = configserverConfig.masterGeneration();
        makeNewSuperModelConfigProvider(new SuperModel());
    }

    @Override
    public SuperModel getSuperModel() {
        synchronized (monitor) {
            return superModelConfigProvider.getSuperModel();
        }
    }

    public SuperModelConfigProvider getSuperModelConfigProvider() {
        synchronized (monitor) {
            return superModelConfigProvider;
        }
    }

    public long getGeneration() {
        synchronized (monitor) {
            return generation;
        }
    }

    @Override
    public void registerListener(SuperModelListener listener) {
        synchronized (monitor) {
            listeners.add(listener);
            SuperModel superModel = superModelConfigProvider.getSuperModel();
            superModel.getAllApplicationInfos().forEach(application -> listener.applicationActivated(superModel, application));

            if (superModel.isComplete()) {
                listener.notifyOfCompleteness(superModel);
            }
        }
    }

    public void configActivated(ApplicationVersions applicationVersions) {
        synchronized (monitor) {
            // TODO: Should supermodel care about multiple versions?
            ApplicationInfo applicationInfo = applicationVersions
                    .getForVersionOrLatest(Optional.empty(), Instant.now())
                    .toApplicationInfo();

            SuperModel newSuperModel = superModelConfigProvider.getSuperModel()
                    .cloneAndSetApplication(applicationInfo);

            generationCounter.increment();
            makeNewSuperModelConfigProvider(newSuperModel);
            listeners.forEach(listener -> listener.applicationActivated(newSuperModel, applicationInfo));
        }
    }

    public void applicationRemoved(ApplicationId applicationId) {
        synchronized (monitor) {
            bootstrapApplicationSet.ifPresent(set -> set.remove(applicationId));

            SuperModel newSuperModel = this.superModelConfigProvider
                    .getSuperModel()
                    .cloneAndRemoveApplication(applicationId);
            generationCounter.increment();
            makeNewSuperModelConfigProvider(newSuperModel);
            listeners.forEach(listener -> listener.applicationRemoved(newSuperModel, applicationId));
        }
    }

    public void markAsComplete() {
        // Invoked on component graph bootstrap (even before ConfigServerBootstrap),
        // there is no need to bump generation counter.
        logger.log(Level.FINE, "Super model is complete");
        SuperModel newSuperModel = getSuperModel().cloneAsComplete();
        superModelConfigProvider = new SuperModelConfigProvider(newSuperModel, zone, flagSource);
        listeners.forEach(listener -> listener.notifyOfCompleteness(newSuperModel));
    }

    private void makeNewSuperModelConfigProvider(SuperModel newSuperModel) {
        generation = masterGeneration + generationCounter.get();
        superModelConfigProvider = new SuperModelConfigProvider(newSuperModel, zone, flagSource);
    }
}