/*
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You under the Apache License, Version 2.0
 * (the "License"); you may not use this file except in compliance with
 * the License.  You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package org.apache.nifi.connectable;

import org.apache.commons.lang3.StringUtils;
import org.apache.commons.lang3.builder.EqualsBuilder;
import org.apache.commons.lang3.builder.HashCodeBuilder;
import org.apache.nifi.authorization.AccessDeniedException;
import org.apache.nifi.authorization.AuthorizationResult;
import org.apache.nifi.authorization.AuthorizationResult.Result;
import org.apache.nifi.authorization.Authorizer;
import org.apache.nifi.authorization.RequestAction;
import org.apache.nifi.authorization.Resource;
import org.apache.nifi.authorization.resource.Authorizable;
import org.apache.nifi.authorization.user.NiFiUser;
import org.apache.nifi.controller.ProcessScheduler;
import org.apache.nifi.controller.queue.ConnectionEventListener;
import org.apache.nifi.controller.queue.FlowFileQueue;
import org.apache.nifi.controller.queue.FlowFileQueueFactory;
import org.apache.nifi.controller.queue.LoadBalanceStrategy;
import org.apache.nifi.controller.queue.PollStrategy;
import org.apache.nifi.controller.repository.FlowFileRecord;
import org.apache.nifi.groups.ProcessGroup;
import org.apache.nifi.processor.FlowFileFilter;
import org.apache.nifi.processor.Relationship;
import org.apache.nifi.remote.RemoteGroupPort;
import org.apache.nifi.scheduling.SchedulingStrategy;

import java.util.ArrayList;
import java.util.Collection;
import java.util.Collections;
import java.util.List;
import java.util.Map;
import java.util.Optional;
import java.util.Set;
import java.util.UUID;
import java.util.concurrent.atomic.AtomicInteger;
import java.util.concurrent.atomic.AtomicLong;
import java.util.concurrent.atomic.AtomicReference;
import java.util.stream.Collectors;

/**
 * Models a connection between connectable components. A connection may contain
 * one or more relationships that map the source component to the destination
 * component.
 */
public final class StandardConnection implements Connection, ConnectionEventListener {
    public static final long DEFAULT_Z_INDEX = 0;

    private final String id;
    private final AtomicReference<ProcessGroup> processGroup;
    private final AtomicReference<String> name;
    private final AtomicReference<List<Position>> bendPoints;
    private final Connectable source;
    private final AtomicReference<Connectable> destination;
    private final AtomicReference<Collection<Relationship>> relationships;
    private final AtomicInteger labelIndex = new AtomicInteger(1);
    private final AtomicLong zIndex = new AtomicLong(DEFAULT_Z_INDEX);
    private final AtomicReference<String> versionedComponentId = new AtomicReference<>();
    private final ProcessScheduler scheduler;
    private final int hashCode;

    private volatile FlowFileQueue flowFileQueue;

    private StandardConnection(final Builder builder) {
        id = builder.id;
        name = new AtomicReference<>(builder.name);
        bendPoints = new AtomicReference<>(Collections.unmodifiableList(new ArrayList<>(builder.bendPoints)));
        processGroup = new AtomicReference<>(builder.processGroup);
        source = builder.source;
        destination = new AtomicReference<>(builder.destination);
        relationships = new AtomicReference<>(Collections.unmodifiableCollection(builder.relationships));
        scheduler = builder.scheduler;

        flowFileQueue = builder.flowFileQueueFactory.createFlowFileQueue(LoadBalanceStrategy.DO_NOT_LOAD_BALANCE, null, this, processGroup.get());
        hashCode = new HashCodeBuilder(7, 67).append(id).toHashCode();
    }

    @Override
    public ProcessGroup getProcessGroup() {
        return processGroup.get();
    }

    @Override
    public String getIdentifier() {
        return id;
    }

    @Override
    public String getName() {
        return name.get();
    }

    @Override
    public void setName(final String name) {
        this.name.set(name);
    }

    @Override
    public Authorizable getParentAuthorizable() {
        return getProcessGroup();
    }

    @Override
    public Resource getResource() {
        return new Resource() {
            @Override
            public String getIdentifier() {
                return "/connections/" + StandardConnection.this.getIdentifier();
            }

            @Override
            public String getName() {
                String name = StandardConnection.this.getName();

                final Collection<Relationship> relationships = getRelationships();
                if (name == null && relationships != null && !relationships.isEmpty()) {
                    name = StringUtils.join(relationships.stream().map(Relationship::getName).collect(Collectors.toSet()), ", ");
                }

                if (name == null) {
                    name = "Connection";
                }

                return name;
            }

            @Override
            public String getSafeDescription() {
                return "Connection " + StandardConnection.this.getIdentifier();
            }
        };
    }

    @Override
    public void triggerDestinationEvent() {
        if (getDestination().getSchedulingStrategy() == SchedulingStrategy.EVENT_DRIVEN) {
            scheduler.registerEvent(getDestination());
        }
    }

    @Override
    public void triggerSourceEvent() {
        if (getSource().getSchedulingStrategy() == SchedulingStrategy.EVENT_DRIVEN) {
            scheduler.registerEvent(getSource());
        }
    }

    @Override
    public Authorizable getSourceAuthorizable() {
        final Connectable sourceConnectable = getSource();
        final Authorizable sourceAuthorizable;

        // if the source is a remote group port, authorize according to the RPG
        if (sourceConnectable instanceof RemoteGroupPort) {
            sourceAuthorizable = ((RemoteGroupPort) sourceConnectable).getRemoteProcessGroup();
        } else {
            sourceAuthorizable = sourceConnectable;
        }

        return sourceAuthorizable;
    }

    @Override
    public Authorizable getDestinationAuthorizable() {
        final Connectable destinationConnectable = getDestination();
        final Authorizable destinationAuthorizable;

        // if the destination is a remote group port, authorize according to the RPG
        if (destinationConnectable instanceof RemoteGroupPort) {
            destinationAuthorizable = ((RemoteGroupPort) destinationConnectable).getRemoteProcessGroup();
        } else {
            destinationAuthorizable = destinationConnectable;
        }

        return destinationAuthorizable;
    }

    @Override
    public AuthorizationResult checkAuthorization(Authorizer authorizer, RequestAction action, NiFiUser user, Map<String, String> resourceContext) {
        if (user == null) {
            return AuthorizationResult.denied("Unknown user.");
        }

        // check the source
        final AuthorizationResult sourceResult = getSourceAuthorizable().checkAuthorization(authorizer, action, user, resourceContext);
        if (Result.Denied.equals(sourceResult.getResult())) {
            return sourceResult;
        }

        // check the destination
        return getDestinationAuthorizable().checkAuthorization(authorizer, action, user, resourceContext);
    }

    @Override
    public void authorize(Authorizer authorizer, RequestAction action, NiFiUser user, Map<String, String> resourceContext) throws AccessDeniedException {
        if (user == null) {
            throw new AccessDeniedException("Unknown user.");
        }

        getSourceAuthorizable().authorize(authorizer, action, user, resourceContext);
        getDestinationAuthorizable().authorize(authorizer, action, user, resourceContext);
    }

    @Override
    public List<Position> getBendPoints() {
        return bendPoints.get();
    }

    @Override
    public void setBendPoints(final List<Position> position) {
        this.bendPoints.set(Collections.unmodifiableList(new ArrayList<>(position)));
    }

    @Override
    public int getLabelIndex() {
        return labelIndex.get();
    }

    @Override
    public void setLabelIndex(final int labelIndex) {
        this.labelIndex.set(labelIndex);
    }

    @Override
    public long getZIndex() {
        return zIndex.get();
    }

    @Override
    public void setZIndex(final long zIndex) {
        this.zIndex.set(zIndex);
    }

    @Override
    public Connectable getSource() {
        return source;
    }

    @Override
    public Connectable getDestination() {
        return destination.get();
    }

    @Override
    public Collection<Relationship> getRelationships() {
        return relationships.get();
    }

    @Override
    public FlowFileQueue getFlowFileQueue() {
        return flowFileQueue;
    }

    @Override
    public void setProcessGroup(final ProcessGroup newGroup) {
        final ProcessGroup currentGroup = this.processGroup.get();
        try {
            this.processGroup.set(newGroup);
        } catch (final RuntimeException e) {
            this.processGroup.set(currentGroup);
            throw e;
        }
    }

    @Override
    public void setRelationships(final Collection<Relationship> newRelationships) {
        final Collection<Relationship> currentRelationships = relationships.get();
        if (currentRelationships.equals(newRelationships)) {
            return;
        }

        try {
            getSource().verifyCanUpdate();
        } catch (final IllegalStateException ise) {
            throw new IllegalStateException("Cannot update the relationships for Connection", ise);
        }

        try {
            this.relationships.set(new ArrayList<>(newRelationships));
            getSource().updateConnection(this);
        } catch (final RuntimeException e) {
            this.relationships.set(currentRelationships);
            throw e;
        }
    }

    @Override
    public void setDestination(final Connectable newDestination) {
        final Connectable previousDestination = destination.get();
        if (previousDestination.equals(newDestination)) {
            return;
        }

        if (previousDestination.isRunning() && !(previousDestination instanceof Funnel || previousDestination instanceof LocalPort)) {
            throw new IllegalStateException("Cannot change destination of Connection because the current destination is running");
        }

        if (getFlowFileQueue().isUnacknowledgedFlowFile()) {
            throw new IllegalStateException("Cannot change destination of Connection because FlowFiles from this Connection are currently held by " + previousDestination);
        }

        if (newDestination instanceof Funnel && newDestination.equals(source)) {
            throw new IllegalStateException("Funnels do not support self-looping connections.");
        }

        try {
            previousDestination.removeConnection(this);
            this.destination.set(newDestination);
            getSource().updateConnection(this);

            newDestination.addConnection(this);
            scheduler.registerEvent(newDestination);
        } catch (final RuntimeException e) {
            this.destination.set(previousDestination);
            throw e;
        }
    }

    @Override
    public void lock() {
        flowFileQueue.lock();
    }

    @Override
    public void unlock() {
        flowFileQueue.unlock();
    }

    @Override
    public List<FlowFileRecord> poll(final FlowFileFilter filter, final Set<FlowFileRecord> expiredRecords) {
        return flowFileQueue.poll(filter, expiredRecords, PollStrategy.UNPENALIZED_FLOWFILES);
    }

    @Override
    public FlowFileRecord poll(final Set<FlowFileRecord> expiredRecords) {
        return flowFileQueue.poll(expiredRecords, PollStrategy.UNPENALIZED_FLOWFILES);
    }

    @Override
    public boolean equals(final Object other) {
        if (!(other instanceof Connection)) {
            return false;
        }
        final Connection con = (Connection) other;
        return new EqualsBuilder().append(id, con.getIdentifier()).isEquals();
    }

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

    @Override
    public String toString() {
        return "Connection[ID=" + getIdentifier() + ", Source ID=" + getSource().getIdentifier() + ", Dest ID=" + getDestination().getIdentifier() + "]";
    }

    /**
     * Gives this Connection ownership of the given FlowFile and allows the
     * Connection to hold on to the FlowFile but NOT provide the FlowFile to
     * consumers. This allows us to ensure that the Connection is not deleted
     * during the middle of a Session commit.
     *
     * @param flowFile to add
     */
    @Override
    public void enqueue(final FlowFileRecord flowFile) {
        flowFileQueue.put(flowFile);
    }

    @Override
    public void enqueue(final Collection<FlowFileRecord> flowFiles) {
        flowFileQueue.putAll(flowFiles);
    }

    public static class Builder {

        private final ProcessScheduler scheduler;

        private String id = UUID.randomUUID().toString();
        private String name;
        private List<Position> bendPoints = new ArrayList<>();
        private ProcessGroup processGroup;
        private Connectable source;
        private Connectable destination;
        private Collection<Relationship> relationships;
        private FlowFileQueueFactory flowFileQueueFactory;
        private boolean clustered = false;

        public Builder(final ProcessScheduler scheduler) {
            this.scheduler = scheduler;
        }

        public Builder id(final String id) {
            this.id = id;
            return this;
        }

        public Builder source(final Connectable source) {
            this.source = source;
            return this;
        }

        public Builder processGroup(final ProcessGroup group) {
            this.processGroup = group;
            return this;
        }

        public Builder destination(final Connectable destination) {
            this.destination = destination;
            return this;
        }

        public Builder relationships(final Collection<Relationship> relationships) {
            this.relationships = new ArrayList<>(relationships);
            return this;
        }

        public Builder name(final String name) {
            this.name = name;
            return this;
        }

        public Builder bendPoints(final List<Position> bendPoints) {
            this.bendPoints.clear();
            this.bendPoints.addAll(bendPoints);
            return this;
        }

        public Builder addBendPoint(final Position bendPoint) {
            bendPoints.add(bendPoint);
            return this;
        }

        public Builder flowFileQueueFactory(final FlowFileQueueFactory flowFileQueueFactory) {
            this.flowFileQueueFactory = flowFileQueueFactory;
            return this;
        }

        public Builder clustered(final boolean clustered) {
            this.clustered = clustered;
            return this;
        }

        public StandardConnection build() {
            if (processGroup == null) {
                throw new IllegalStateException("Cannot build a Connection without a Process Group");
            }
            if (source == null) {
                throw new IllegalStateException("Cannot build a Connection without a Source");
            }
            if (destination == null) {
                throw new IllegalStateException("Cannot build a Connection without a Destination");
            }
            if (flowFileQueueFactory == null) {
                throw new IllegalStateException("Cannot build a Connection without a FlowFileQueueFactory");
            }

            if (relationships == null) {
                relationships = new ArrayList<>();
            }

            if (relationships.isEmpty()) {
                // ensure relationships have been specified for processors, otherwise the anonymous relationship is used
                if (source.getConnectableType() == ConnectableType.PROCESSOR) {
                    throw new IllegalStateException("Cannot build a Connection without any relationships");
                }
                relationships.add(Relationship.ANONYMOUS);
            }

            return new StandardConnection(this);
        }
    }

    @Override
    public void verifyCanUpdate() {
        // StandardConnection can always be updated
    }

    @Override
    public void verifyCanDelete() {
        if (!flowFileQueue.isEmpty()) {
            throw new IllegalStateException("Queue not empty for " + this.getIdentifier());
        }

        // The source must be stopped unless it is a Funnel. Funnels cannot be stopped & started. But if the source is a Funnel,
        // it means that its sources must also be stopped, and the check must go on recursively.
        // This is important for a case in which we have a cluster where two processors (for example) are connected with a funnel in between.
        // In this case, if a user deletes the connection between the funnel and its destination, the web request that is made will be done in two
        // phases: (1) Verify that the request is valid and (2) Delete the connection. But if we don't recursively ensure that the upstream components
        // are stopped, we could have all nodes in the cluster verify the request is valid in the first phase. But before the second phase occurs, one
        // node may now have data within the Connection, so the second phase (the delete) will fail. In that situation, the node's dataflow will differ
        // from the rest of the cluster, and the node will be kicked out of the cluster. To avoid this, we simply ensure that the source is stopped,
        // and if the source is a funnel (which can't be stopped) that its sources are stopped.
        verifySourceStoppedOrFunnel(this);

        final Connectable dest = destination.get();
        if (dest.isRunning()) {
            if (!ConnectableType.FUNNEL.equals(dest.getConnectableType())) {
                throw new IllegalStateException("Destination of Connection (" + dest.getIdentifier() + ") is running");
            }
        }
    }

    private void verifySourceStoppedOrFunnel(final Connection connection) {
        final Connectable sourceComponent = connection.getSource();
        if (!sourceComponent.isRunning()) {
            return;
        }

        final ConnectableType connectableType = sourceComponent.getConnectableType();
        if (connectableType != ConnectableType.FUNNEL) {
            // Source is running and not a funnel. Source is not considered stopped.
            throw new IllegalStateException("Upstream component of Connection (" + sourceComponent + ") is running");
        }

        // Source is a funnel and is running. We need to then check all of its upstream components.
        for (final Connection incoming : sourceComponent.getIncomingConnections()) {
            verifySourceStoppedOrFunnel(incoming);
        }
    }

    @Override
    public Optional<String> getVersionedComponentId() {
        return Optional.ofNullable(versionedComponentId.get());
    }

    @Override
    public void setVersionedComponentId(final String versionedComponentId) {
        boolean updated = false;
        while (!updated) {
            final String currentId = this.versionedComponentId.get();

            if (currentId == null) {
                updated = this.versionedComponentId.compareAndSet(null, versionedComponentId);
            } else if (currentId.equals(versionedComponentId)) {
                return;
            } else if (versionedComponentId == null) {
                updated = this.versionedComponentId.compareAndSet(currentId, null);
            } else {
                throw new IllegalStateException(this + " is already under version control");
            }
        }
    }
}
