// Copyright Yahoo. Licensed under the terms of the Apache 2.0 license. See LICENSE in the project root.
package com.yahoo.container.jdisc.messagebus;

import com.yahoo.component.annotation.Inject;
import com.yahoo.component.AbstractComponent;
import com.yahoo.container.jdisc.ContainerMbusConfig;
import com.yahoo.document.DocumentTypeManager;
import com.yahoo.document.DocumentUtil;
import com.yahoo.documentapi.messagebus.loadtypes.LoadTypeSet;
import com.yahoo.documentapi.messagebus.protocol.DocumentProtocol;
import com.yahoo.documentapi.messagebus.protocol.DocumentProtocolPoliciesConfig;
import com.yahoo.jdisc.ReferencedResource;
import com.yahoo.jdisc.References;
import com.yahoo.jdisc.ResourceReference;
import com.yahoo.jdisc.SharedResource;
import com.yahoo.messagebus.ConfigAgent;
import com.yahoo.messagebus.DynamicThrottlePolicy;
import com.yahoo.messagebus.IntermediateSessionParams;
import com.yahoo.messagebus.MessageBus;
import com.yahoo.messagebus.MessageBusParams;
import com.yahoo.messagebus.MessagebusConfig;
import com.yahoo.messagebus.Protocol;
import com.yahoo.messagebus.SourceSessionParams;
import com.yahoo.messagebus.StaticThrottlePolicy;
import com.yahoo.messagebus.ThrottlePolicy;
import com.yahoo.messagebus.network.NetworkMultiplexer;
import com.yahoo.messagebus.shared.SharedIntermediateSession;
import com.yahoo.messagebus.shared.SharedMessageBus;
import com.yahoo.messagebus.shared.SharedSourceSession;
import com.yahoo.vespa.config.content.DistributionConfig;
import com.yahoo.vespa.config.content.LoadTypeConfig;
import com.yahoo.yolean.concurrent.Memoized;

import java.util.HashMap;
import java.util.Map;
import java.util.function.Supplier;
import java.util.logging.Level;
import java.util.logging.Logger;

/**
 * Class to encapsulate access to slobrok sessions.
 *
 * @author Steinar Knutsen
 * @author Einar Rosenvinge
 */
// TODO jonmv: Remove this: only used with more than one entry by FeedHandlerV3, where only timeout varies.
// rant: This whole construct is because DI at one point didn't exist, so getting hold of a shared resource
//       or session was hard(?), and one resorted to routing through the Container, using URIs, to the correct
//       MbusClient, with or without throttling. This introduced the problem of ownership during shutdown,
//       which was solved with manual reference counting. This is all much better solved with DI, which (now)
//       owns everything, and does component shutdown in reverse construction order, which is always right.
//       So for the sake of everyone's mental health, this should all just be removed now! I suspect this is
//       even the case for Request; we can track in handlers, and warn when requests have been misplaced.
public final class SessionCache extends AbstractComponent {

    private static final Logger log = Logger.getLogger(SessionCache.class.getName());

    private final Memoized<SharedMessageBus, RuntimeException> messageBus;

    private final Object intermediateLock = new Object();
    private final Map<String, SharedIntermediateSession> intermediates = new HashMap<>();
    private final IntermediateSessionCreator intermediatesCreator = new IntermediateSessionCreator();

    private final Object sourceLock = new Object();
    private final Map<SourceSessionKey, SharedSourceSession> sources = new HashMap<>();
    private final SourceSessionCreator sourcesCreator = new SourceSessionCreator();

    @Inject
    public SessionCache(NetworkMultiplexerProvider nets, ContainerMbusConfig containerMbusConfig,
                        DocumentTypeManager documentTypeManager,
                        MessagebusConfig messagebusConfig,
                        DocumentProtocolPoliciesConfig policiesConfig,
                        DistributionConfig distributionConfig) {
        this(nets::net, containerMbusConfig, documentTypeManager,
             null/*TODO: Remove on Vespa 8*/, messagebusConfig, policiesConfig, distributionConfig);

    }

    /**
     * @deprecated load types are deprecated. Use constructor without LoadTypeSet instead.
     */
    @Deprecated(forRemoval = true) // TODO: Remove on Vespa 8
    public SessionCache(Supplier<NetworkMultiplexer> net, ContainerMbusConfig containerMbusConfig,
                        DocumentTypeManager documentTypeManager,
                        LoadTypeConfig loadTypeConfig, MessagebusConfig messagebusConfig,
                        DocumentProtocolPoliciesConfig policiesConfig,
                        DistributionConfig distributionConfig) {
        this(net,
             containerMbusConfig,
             messagebusConfig,
             new DocumentProtocol(documentTypeManager,
                                  policiesConfig,
                                  distributionConfig));
    }

    public SessionCache(Supplier<NetworkMultiplexer> net, ContainerMbusConfig containerMbusConfig,
                        MessagebusConfig messagebusConfig, Protocol protocol) {
        this.messageBus = new Memoized<>(() -> createSharedMessageBus(net.get(), containerMbusConfig, messagebusConfig, protocol),
                                         SharedMessageBus::release);
    }

    @Override
    public void deconstruct() {
        messageBus.close();
    }

    // Lazily create shared message bus.
    private SharedMessageBus bus() {
        return messageBus.get();
    }

    private static SharedMessageBus createSharedMessageBus(NetworkMultiplexer net,
                                                           ContainerMbusConfig mbusConfig,
                                                           MessagebusConfig messagebusConfig,
                                                           Protocol protocol) {
        MessageBusParams mbusParams = new MessageBusParams().addProtocol(protocol);

        int maxPendingSize = DocumentUtil
                .calculateMaxPendingSize(mbusConfig.maxConcurrentFactor(), mbusConfig.documentExpansionFactor(),
                        mbusConfig.containerCoreMemory());
        logSystemInfo(mbusConfig, maxPendingSize);

        mbusParams.setMaxPendingCount(mbusConfig.maxpendingcount());
        mbusParams.setMaxPendingSize(maxPendingSize);

        MessageBus bus = new MessageBus(net, mbusParams);
        new ConfigAgent(messagebusConfig, bus); // Configure the wrapped MessageBus with a routing table.
        return new SharedMessageBus(bus);
    }

    private static void logSystemInfo(ContainerMbusConfig containerMbusConfig, long maxPendingSize) {
        log.log(Level.FINE,
                "Running with maximum heap size of " + (Runtime.getRuntime().maxMemory() / 1024L / 1024L) + " MB");
        log.log(Level.CONFIG,
                "Amount of memory reserved for container core: " + containerMbusConfig.containerCoreMemory() + " MB.");
        log.log(Level.CONFIG,
                "Running with document expansion factor " + containerMbusConfig.documentExpansionFactor() + "");

        String msgLimit =
                (containerMbusConfig.maxpendingcount() == 0) ? "unlimited" : "" + containerMbusConfig.maxpendingcount();
        log.log(Level.CONFIG, ("Starting message bus with max " + msgLimit + " pending messages and max " +
                (((double) (maxPendingSize / 1024L)) / 1024.0d) + " pending megabytes."));
    }

    ReferencedResource<SharedIntermediateSession> retainIntermediate(final IntermediateSessionParams p) {
        return intermediatesCreator.retain(intermediateLock, intermediates, p);
    }

    public ReferencedResource<SharedSourceSession> retainSource(final SourceSessionParams p) {
        return sourcesCreator.retain(sourceLock, sources, p);
    }

    private abstract static class SessionCreator<PARAMS, KEY, SESSION extends SharedResource> {

        abstract SESSION create(PARAMS p);

        abstract KEY buildKey(PARAMS p);

        abstract void logReuse(SESSION session);

        ReferencedResource<SESSION> retain(Object lock, Map<KEY, SESSION> registry, PARAMS p) {
            SESSION session;
            ResourceReference sessionReference;
            KEY key = buildKey(p);
            // this lock is held for a horribly long time, but I see no way of
            // making it slimmer
            synchronized (lock) {
                session = registry.get(key);
                if (session == null) {
                    session = createAndStore(registry, p, key);
                    sessionReference = References.fromResource(session);
                } else {
                    try {
                        sessionReference = session.refer(this);
                        logReuse(session);
                    } catch (final IllegalStateException e) {
                        session = createAndStore(registry, p, key);
                        sessionReference = References.fromResource(session);
                    }
                }
            }
            return new ReferencedResource<>(session, sessionReference);
        }

        SESSION createAndStore(Map<KEY, SESSION> registry, PARAMS p, KEY key) {
            SESSION session = create(p);
            registry.put(key, session);
            return session;
        }

    }

    private class SourceSessionCreator
            extends SessionCreator<SourceSessionParams, SourceSessionKey, SharedSourceSession> {

        @Override
        SharedSourceSession create(SourceSessionParams p) {
            log.log(Level.FINE, "Creating new source session.");
            return bus().newSourceSession(p);
        }

        @Override
        SourceSessionKey buildKey(SourceSessionParams p) {
            return new SourceSessionKey(p);
        }

        @Override
        void logReuse(final SharedSourceSession session) {
            log.log(Level.FINE, "Reusing source session.");
        }
    }

    private class IntermediateSessionCreator
            extends SessionCreator<IntermediateSessionParams, String, SharedIntermediateSession> {

        @Override
        SharedIntermediateSession create(IntermediateSessionParams p) {
            log.log(Level.FINE, "Creating new intermediate session " + p.getName() + "");
            return bus().newIntermediateSession(p);
        }

        @Override
        String buildKey(IntermediateSessionParams p) {
            return p.getName();
        }

        @Override
        void logReuse(SharedIntermediateSession session) {
            log.log(Level.FINE, "Reusing intermediate session " + session.name() + "");
        }
    }

    static class ThrottlePolicySignature {

        @Override
        public int hashCode() {
            return getClass().hashCode();
        }

    }

    static class StaticThrottlePolicySignature extends ThrottlePolicySignature {

        private final int maxPendingCount;
        private final long maxPendingSize;

        StaticThrottlePolicySignature(final StaticThrottlePolicy policy) {
            maxPendingCount = policy.getMaxPendingCount();
            maxPendingSize = policy.getMaxPendingSize();
        }

        @Override
        public int hashCode() {
            int prime = 31;
            int result = super.hashCode();
            result = prime * result + maxPendingCount;
            result = prime * result
                    + (int) (maxPendingSize ^ (maxPendingSize >>> 32));
            return result;
        }

        @Override
        public boolean equals(final Object obj) {
            if (this == obj) {
                return true;
            }
            if (getClass() != obj.getClass()) {
                return false;
            }
            final StaticThrottlePolicySignature other = (StaticThrottlePolicySignature) obj;
            if (maxPendingCount != other.maxPendingCount) {
                return false;
            }
            if (maxPendingSize != other.maxPendingSize) {
                return false;
            }
            return true;
        }

    }

    static class DynamicThrottlePolicySignature extends ThrottlePolicySignature {

        private final int maxPending;
        private final double maxWindowSize;
        private final double minWindowSize;
        private final double windowSizeBackoff;
        private final double windowSizeIncrement;

        DynamicThrottlePolicySignature(final DynamicThrottlePolicy policy) {
            maxPending = policy.getMaxPendingCount();
            maxWindowSize = policy.getMaxWindowSize();
            minWindowSize = policy.getMinWindowSize();
            windowSizeBackoff = policy.getWindowSizeBackOff();
            windowSizeIncrement = policy.getWindowSizeIncrement();
        }

        @Override
        public int hashCode() {
            int prime = 31;
            int result = super.hashCode();
            result = prime * result + maxPending;
            long temp;
            temp = Double.doubleToLongBits(maxWindowSize);
            result = prime * result + (int) (temp ^ (temp >>> 32));
            temp = Double.doubleToLongBits(minWindowSize);
            result = prime * result + (int) (temp ^ (temp >>> 32));
            temp = Double.doubleToLongBits(windowSizeBackoff);
            result = prime * result + (int) (temp ^ (temp >>> 32));
            temp = Double.doubleToLongBits(windowSizeIncrement);
            result = prime * result + (int) (temp ^ (temp >>> 32));
            return result;
        }

        @Override
        public boolean equals(Object obj) {
            if (this == obj) {
                return true;
            }
            if (getClass() != obj.getClass()) {
                return false;
            }
            DynamicThrottlePolicySignature other = (DynamicThrottlePolicySignature) obj;
            if (maxPending != other.maxPending) {
                return false;
            }
            if (Double.doubleToLongBits(maxWindowSize) != Double.doubleToLongBits(other.maxWindowSize)) {
                return false;
            }
            if (Double.doubleToLongBits(minWindowSize) != Double
                    .doubleToLongBits(other.minWindowSize)) {
                return false;
            }
            if (Double.doubleToLongBits(windowSizeBackoff) != Double.doubleToLongBits(other.windowSizeBackoff)) {
                return false;
            }
            if (Double.doubleToLongBits(windowSizeIncrement) != Double.doubleToLongBits(other.windowSizeIncrement)) {
                return false;
            }
            return true;
        }

    }

    static class UnknownThrottlePolicySignature extends ThrottlePolicySignature {

        private final ThrottlePolicy policy;

        UnknownThrottlePolicySignature(final ThrottlePolicy policy) {
            this.policy = policy;
        }

        @Override
        public boolean equals(Object other) {
            if (other == null) {
                return false;
            }
            if (other.getClass() != getClass()) {
                return false;
            }
            return ((UnknownThrottlePolicySignature) other).policy == policy;
        }
    }

    static class SourceSessionKey {

        private final double timeout;
        private final ThrottlePolicySignature policy;

        SourceSessionKey(SourceSessionParams p) {
            timeout = p.getTimeout();
            policy = createSignature(p.getThrottlePolicy());
        }

        private static ThrottlePolicySignature createSignature(ThrottlePolicy policy) {
            Class<?> policyClass = policy.getClass();
            if (policyClass == DynamicThrottlePolicy.class) {
                return new DynamicThrottlePolicySignature((DynamicThrottlePolicy) policy);
            } else if (policyClass == StaticThrottlePolicy.class) {
                return new StaticThrottlePolicySignature((StaticThrottlePolicy) policy);
            } else {
                return new UnknownThrottlePolicySignature(policy);
            }
        }

        @Override
        public String toString() {
            return "SourceSessionKey{" + "timeout=" + timeout + ", policy=" + policy + '}';
        }

        @Override
        public int hashCode() {
            int prime = 31;
            int result = 1;
            result = prime * result + ((policy == null) ? 0 : policy.hashCode());
            long temp;
            temp = Double.doubleToLongBits(timeout);
            result = prime * result + (int) (temp ^ (temp >>> 32));
            return result;
        }

        @Override
        public boolean equals(Object obj) {
            if (this == obj) return true;
            if (obj == null) return false;
            if (getClass() != obj.getClass()) return false;
            SourceSessionKey other = (SourceSessionKey) obj;
            if (policy == null) {
                if (other.policy != null) return false;
            } else if (!policy.equals(other.policy)) {
                return false;
            }
            if (Double.doubleToLongBits(timeout) != Double.doubleToLongBits(other.timeout)) return false;
            return true;
        }
    }

}