/*
 * (C) Copyright 2016 Nuxeo SA (http://nuxeo.com/) and others.
 *
 * Licensed 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.nuxeo.ecm.platform.importer.queue.consumer;

import com.codahale.metrics.Counter;
import com.codahale.metrics.MetricRegistry;
import com.codahale.metrics.SharedMetricRegistries;
import com.codahale.metrics.Timer;

import org.nuxeo.common.utils.ExceptionUtils;
import org.nuxeo.ecm.core.api.CoreSession;
import org.nuxeo.ecm.core.api.DocumentModel;
import org.nuxeo.ecm.core.api.DocumentRef;
import org.nuxeo.ecm.core.api.UnrestrictedSessionRunner;
import org.nuxeo.ecm.platform.importer.log.ImporterLogger;
import org.nuxeo.ecm.platform.importer.queue.AbstractTaskRunner;
import org.nuxeo.ecm.platform.importer.source.SourceNode;
import org.nuxeo.runtime.metrics.MetricsService;
import org.nuxeo.runtime.transaction.TransactionHelper;

import java.util.concurrent.BlockingQueue;
import java.util.concurrent.TimeUnit;

import static java.lang.Thread.currentThread;
import static org.nuxeo.runtime.transaction.TransactionHelper.startTransaction;

/**
 * @since 8.3
 */
public abstract class AbstractConsumer extends AbstractTaskRunner implements Consumer {

    protected final Batch batch;

    protected final String repositoryName;

    protected final BlockingQueue<SourceNode> queue;

    protected final DocumentRef rootRef;

    protected long startTime = 0;

    protected long lastCheckTime = 0;

    protected long lastCount = 0;

    protected static final long CHECK_INTERVAL = 2000;

    protected double lastImediatThroughput = 0;

    protected String originatingUsername;

    protected ImporterLogger log = null;

    protected boolean replayMode = true;

    protected String threadName;

    protected final MetricRegistry registry = SharedMetricRegistries.getOrCreate(MetricsService.class.getName());

    protected final Timer processTimer;

    protected final Timer commitTimer;

    protected final Counter retryCount;

    protected final Counter failCount;

    protected final Counter consumerCount;

    public AbstractConsumer(ImporterLogger log, DocumentModel root, int batchSize, BlockingQueue<SourceNode> queue) {
        this.log = log;
        repositoryName = root.getRepositoryName();
        this.batch = new Batch(batchSize);
        this.queue = queue;
        rootRef = root.getRef();

        processTimer = registry.timer(MetricRegistry.name("nuxeo", "importer", "queue", "consumer", "import"));
        commitTimer = registry.timer(MetricRegistry.name("nuxeo", "importer", "queue", "consumer", "commit"));
        retryCount = registry.counter(MetricRegistry.name("nuxeo", "importer", "queue", "consumer", "retry"));
        failCount = registry.counter(MetricRegistry.name("nuxeo", "importer", "queue", "consumer", "fail"));
        consumerCount = registry.counter(MetricRegistry.name("nuxeo", "importer", "queue", "consumer"));

        log.info("Create consumer root:" + root.getPathAsString() + " batchSize: " + batchSize);
    }

    @Override
    public void run() {
        threadName = currentThread().getName();
        started = true;
        startTime = System.currentTimeMillis();
        lastCheckTime = startTime;
        consumerCount.inc();
        try {
            runImport();
        } catch (Exception e) {
            log.error("Unexpected End of consumer after " + getNbProcessed() + " nodes.", e);
            ExceptionUtils.checkInterrupt(e);
            runDrainer();
            error = e;
        } finally {
            completed = true;
            started = false;
            consumerCount.dec();
        }
    }

    protected void runDrainer() {
        // consumer is broken but we drain the queue to prevent blocking the producer
        markThreadName("draining");
        log.error("Consumer is broken, draining the queue to rejected");
        do {
            try {
                SourceNode src = queue.poll(1, TimeUnit.SECONDS);
                if (src == null && canStop) {
                    log.info("End of broken consumer, processed node: " + getNbProcessed());
                    break;
                } else if (src != null) {
                    log.error("Consumer is broken reject node: " + src.getName());
                    onSourceNodeException(src, error);
                }
            } catch (InterruptedException e) {
                log.error("Interrupted exception received, stopping consumer");
                break;
            }
        } while(true);
    }

    private void markThreadName(String mark) {
        Thread.currentThread().setName(Thread.currentThread().getName() + "-" + mark);
    }

    protected void runImport() {

        UnrestrictedSessionRunner runner = new UnrestrictedSessionRunner(repositoryName, originatingUsername) {
            @Override
            public void run() {
                log.info("Consumer running");
                SourceNode src;
                while (true) {
                    try {
                        src = queue.poll(1, TimeUnit.SECONDS);
                    } catch (InterruptedException e) {
                        log.error("Interrupted exception received, stopping consumer");
                        break;
                    }
                    if (src == null) {
                        log.debug("Poll timeout, queue size:" + queue.size());
                        if (canStop) {
                            log.info("End of consumer, processed node: " + getNbProcessed());
                            break;
                        }
                        continue;
                    }
                    incrementProcessed();
                    batch.add(src);
                    Timer.Context stopWatch = processTimer.time();
                    try {
                        setThreadName(src);
                        process(session, src);
                        restoreThreadName();
                    } catch (Exception e) {
                        log.error("Exception while consuming node: " + src.getName(), e);
                        ExceptionUtils.checkInterrupt(e);
                        TransactionHelper.setTransactionRollbackOnly();
                    } finally {
                        stopWatch.stop();
                    }
                    commitIfNeededOrReplayBatch(src);
                }
                commitOrReplayBatch();

            }

            private void restoreThreadName() {
                currentThread().setName(threadName);
            }

            private void setThreadName(SourceNode src) {
                String name = threadName + "-" + nbProcessed;
                if (src != null) {
                    name += "-" + src.getName();
                } else {
                    name += "-null";
                }
                currentThread().setName(name);
            }

            private void commitIfNeededOrReplayBatch(SourceNode lastSrc) {
                if (TransactionHelper.isTransactionMarkedRollback()) {
                    log.error("Transaction marked as rollback while processing node: " + lastSrc.getName());
                    rollbackAndReplayBatch(session);
                } else {
                    commitIfNeeded(session);
                }
            }

            private void commitOrReplayBatch() {
                if (TransactionHelper.isTransactionMarkedRollback()) {
                    rollbackAndReplayBatch(session);
                } else {
                    commit(session);
                }
            }

        };

        if (!TransactionHelper.isTransactionActiveOrMarkedRollback()) {
            // This is needed to acquire a session
            startTransaction();
        }
        runner.runUnrestricted();

    }

    protected abstract void process(CoreSession session, SourceNode bh) throws Exception;

    protected void commitIfNeeded(CoreSession session) {
        if (batch.isFull()) {
            commit(session);
            long t = System.currentTimeMillis();
            if (t - lastCheckTime > CHECK_INTERVAL) {
                lastImediatThroughput = 1000 * (nbProcessed.get() - lastCount + 0.0) / (t - lastCheckTime);
                lastCount = nbProcessed.get();
                lastCheckTime = t;
            }
        }
    }

    protected void commit(CoreSession session) {
        if (batch.size() > 0) {
            Timer.Context stopWatch = commitTimer.time();
            try {
                log.debug("Commit batch of " + batch.size() + " nodes");
                session.save();
                TransactionHelper.commitOrRollbackTransaction();
                batch.clear();
                startTransaction();
            } finally {
                stopWatch.stop();
            }

        }
    }

    protected void rollbackAndReplayBatch(CoreSession session) {
        log.info("Rollback a batch of " + batch.size() + " docs");
        TransactionHelper.setTransactionRollbackOnly();
        session.save();
        TransactionHelper.commitOrRollbackTransaction();
        replayBatch(session);
        batch.clear();
        startTransaction();
    }

    /**
     * Replays the current batch in an isolated Transaction for each Source Node.
     *
     * @param session
     * @throws InterruptedException
     */
    private void replayBatch(CoreSession session) {
        if (! replayMode) {
            log.error("No replay mode, loosing the batch");
            return;
        }
        log.error("Replaying batch in isolated transaction");
        for (SourceNode node : batch.getNodes()) {
            boolean success = false;
            startTransaction();
            retryCount.inc();
            Timer.Context stopWatch = processTimer.time();
            try {
                process(session, node);
            } catch (Exception e) { // deals with interrupt below
                ExceptionUtils.checkInterrupt(e);
                onSourceNodeException(node, e);
                TransactionHelper.setTransactionRollbackOnly();
                failCount.inc();
            } finally {
                stopWatch.stop();
            }
            session.save();
            if (TransactionHelper.isTransactionMarkedRollback()) {
                onSourceNodeRollBack(node);
            } else {
                success = true;
            }
            TransactionHelper.commitOrRollbackTransaction();
            if (success) {
                log.debug("Replaying successfully node: " + node.getName());
            } else {
                log.error("Import failure after replay on node: " + node.getName());
            }
        }
    }

    /**
     * Override if you want to do more that logging the error.
     *
     * @param node
     * @param e
     */
    protected void onSourceNodeException(SourceNode node, Exception e) {
        log.error(String.format("Unable to import node [%s]", node.getName()), e);
    }

    /**
     * Override if you want to do more that logging the error.
     *
     * @param node
     */
    protected void onSourceNodeRollBack(SourceNode node) {
        log.error(String.format("Rollback while replaying consumer node [%s]", node.getName()));
    }

    public String getOriginatingUsername() {
        return originatingUsername;
    }

    public void setOriginatingUsername(String originatingUsername) {
        this.originatingUsername = originatingUsername;
    }

}