/**
 * Copyright 2005-2015 The Kuali Foundation
 *
 * Licensed under the Educational Community 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.opensource.org/licenses/ecl2.php
 *
 * 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.kuali.rice.kim.service.impl;

import java.util.ArrayList;
import java.util.Arrays;
import java.util.Collections;
import java.util.Comparator;
import java.util.HashSet;
import java.util.List;
import java.util.Set;
import java.util.concurrent.Callable;
import java.util.concurrent.ConcurrentLinkedQueue;
import java.util.concurrent.TimeUnit;
import java.util.concurrent.atomic.AtomicBoolean;
import java.util.concurrent.atomic.AtomicInteger;

import org.apache.commons.lang.StringUtils;
import org.apache.log4j.Level;
import org.apache.log4j.Logger;
import org.kuali.rice.core.api.config.property.ConfigurationService;
import org.kuali.rice.core.api.criteria.QueryByCriteria;
import org.kuali.rice.kim.api.KimConstants;
import org.kuali.rice.kim.api.identity.entity.EntityDefault;
import org.kuali.rice.kim.api.identity.principal.Principal;
import org.kuali.rice.kim.impl.identity.EntityDefaultInfoCacheBo;
import org.kuali.rice.kim.impl.identity.IdentityArchiveService;
import org.kuali.rice.krad.data.DataObjectService;
import org.kuali.rice.ksb.service.KSBServiceLocator;
import org.springframework.beans.factory.DisposableBean;
import org.springframework.beans.factory.InitializingBean;
import org.springframework.transaction.PlatformTransactionManager;
import org.springframework.transaction.TransactionStatus;
import org.springframework.transaction.support.TransactionCallback;
import org.springframework.transaction.support.TransactionTemplate;

/**
 * This is the default implementation for the IdentityArchiveService.
 * @see IdentityArchiveService
 *
 * @author Kuali Rice Team (rice.collab@kuali.org)
 */
public class IdentityArchiveServiceImpl implements IdentityArchiveService, InitializingBean, DisposableBean {
        private static final Logger LOG = Logger.getLogger( IdentityArchiveServiceImpl.class );

        protected DataObjectService dataObjectService;
        protected ConfigurationService kualiConfigurationService;
        protected PlatformTransactionManager transactionManager;

        protected static final String EXEC_INTERVAL_SECS = "kim.identityArchiveServiceImpl.executionIntervalSeconds";
        protected static final String MAX_WRITE_QUEUE_SIZE = "kim.identityArchiveServiceImpl.maxWriteQueueSize";
        protected static final int EXECUTION_INTERVAL_SECONDS_DEFAULT = 600; // by default, flush the write queue this often
        protected static final int MAX_WRITE_QUEUE_SIZE_DEFAULT = 300; // cache this many KEDI's before forcing write

        protected final WriteQueue writeQueue = new WriteQueue();
        protected final EntityArchiveWriter writer = new EntityArchiveWriter();

        // all this ceremony just decorates the writer so it logs a message first, and converts the Callable to Runnable
        protected final Runnable maxQueueSizeExceededWriter =
                new CallableAdapter(new PreLogCallableWrapper<Boolean>(writer, Level.DEBUG, "max size exceeded, flushing write queue"));

        // ditto
        protected final Runnable scheduledWriter =
                new CallableAdapter(new PreLogCallableWrapper<Boolean>(writer, Level.DEBUG, "scheduled write out, flushing write queue"));

        // ditto
        protected final Runnable shutdownWriter =
                new CallableAdapter(new PreLogCallableWrapper<Boolean>(writer, Level.DEBUG, "rice is shutting down, flushing write queue"));

        protected int getExecutionIntervalSeconds() {
                final String prop = kualiConfigurationService.getPropertyValueAsString(EXEC_INTERVAL_SECS);
                try {
                        return Integer.valueOf(prop).intValue();
                } catch (NumberFormatException e) {
                        return EXECUTION_INTERVAL_SECONDS_DEFAULT;
                }
        }

        protected int getMaxWriteQueueSize() {
                final String prop = kualiConfigurationService.getPropertyValueAsString(MAX_WRITE_QUEUE_SIZE);
                try {
                        return Integer.valueOf(prop).intValue();
                } catch (NumberFormatException e) {
                        return MAX_WRITE_QUEUE_SIZE_DEFAULT;
                }
        }

        @Override
        public EntityDefault getEntityDefaultFromArchive( String entityId ) {
        if (StringUtils.isBlank(entityId)) {
            throw new IllegalArgumentException("entityId is blank");
        }

        List<EntityDefaultInfoCacheBo> results = dataObjectService.findMatching(EntityDefaultInfoCacheBo.class,
                QueryByCriteria.Builder.forAttribute(KimConstants.PrimaryKeyConstants.SUB_ENTITY_ID, entityId).build() ).getResults();
        EntityDefaultInfoCacheBo cachedValue = null;
        if ( !results.isEmpty() ) {
            cachedValue = results.get(0);
        }

        return (cachedValue == null) ? null : cachedValue.convertCacheToEntityDefaultInfo();
    }

    @Override
        public EntityDefault getEntityDefaultFromArchiveByPrincipalId(String principalId) {
        if (StringUtils.isBlank(principalId)) {
            throw new IllegalArgumentException("principalId is blank");
        }

        EntityDefaultInfoCacheBo cachedValue = dataObjectService.find(EntityDefaultInfoCacheBo.class, principalId);
        return (cachedValue == null) ? null : cachedValue.convertCacheToEntityDefaultInfo();
    }

    @Override
        public EntityDefault getEntityDefaultFromArchiveByPrincipalName(String principalName) {
        if (StringUtils.isBlank(principalName)) {
            throw new IllegalArgumentException("principalName is blank");
        }

        List<EntityDefaultInfoCacheBo> entities = dataObjectService.findMatching(EntityDefaultInfoCacheBo.class,
                QueryByCriteria.Builder.forAttribute("principalName", principalName).build()).getResults();
        return entities.isEmpty() ? null : entities.get(0).convertCacheToEntityDefaultInfo();
    }

    @Override
    public EntityDefault getEntityDefaultFromArchiveByEmployeeId(String employeeId) {
        if (StringUtils.isBlank(employeeId)) {
            throw new IllegalArgumentException("employeeId is blank");
        }
        List<EntityDefaultInfoCacheBo> entities = dataObjectService.findMatching(EntityDefaultInfoCacheBo.class,
                QueryByCriteria.Builder.forAttribute("employeeId", employeeId).build()).getResults();
        return entities.isEmpty() ? null : entities.get(0).convertCacheToEntityDefaultInfo();
    }

    @Override
        public void saveEntityDefaultToArchive(EntityDefault entity) {
        if (entity == null) {
            throw new IllegalArgumentException("entity is blank");
        }

        // if the max size has been reached, schedule now
        if (getMaxWriteQueueSize() <= writeQueue.offerAndGetSize(entity) /* <- this enqueues the KEDI */ &&
                        writer.requestSubmit()) {
                KSBServiceLocator.getThreadPool().execute(maxQueueSizeExceededWriter);
        }
    }

    @Override
    public void flushToArchive() {
        writer.call();
    }

        public void setKualiConfigurationService(
                        ConfigurationService kualiConfigurationService) {
                this.kualiConfigurationService = kualiConfigurationService;
        }

    public void setTransactionManager(PlatformTransactionManager txMgr) {
        this.transactionManager = txMgr;
    }

    /** schedule the writer on the KSB scheduled pool. */
        @Override
        public void afterPropertiesSet() throws Exception {
                LOG.info("scheduling writer...");
                KSBServiceLocator.getScheduledPool().scheduleAtFixedRate(scheduledWriter,
                                getExecutionIntervalSeconds(), getExecutionIntervalSeconds(), TimeUnit.SECONDS);
        }

        /** flush the write queue immediately. */
        @Override
        public void destroy() throws Exception {
                shutdownWriter.run();
        }

        /**
         * store the person to the database, but do this an alternate thread to
         * prevent transaction issues since this service is non-transactional
         *
         * @author Kuali Rice Team (rice.collab@kuali.org)
         *
         */
        protected class EntityArchiveWriter implements Callable {

                // flag used to prevent multiple processes from being submitted at once
                AtomicBoolean currentlySubmitted = new AtomicBoolean(false);

                private final Comparator<Comparable> nullSafeComparator = new Comparator<Comparable>() {
                        @Override
                        public int compare(Comparable i1, Comparable i2) {
                                if (i1 != null && i2 != null) {
                                        return i1.compareTo(i2);
                                } else if (i1 == null) {
                                        if (i2 == null) {
                                                return 0;
                                        } else {
                                                return -1;
                                        }
                                } else { // if (entityId2 == null) {
                                        return 1;
                                }
                        };
                };

                /**
                 * Comparator that attempts to impose a total ordering on EntityDefault instances
                 */
                protected final Comparator<EntityDefault> kediComparator = new Comparator<EntityDefault>() {
                        /**
                         * compares by entityId value
                         * @see java.util.Comparator#compare(java.lang.Object, java.lang.Object)
                         */
                        @Override
                        public int compare(EntityDefault o1, EntityDefault o2) {
                                String entityId1 = (o1 == null) ? null : o1.getEntityId();
                                String entityId2 = (o2 == null) ? null : o2.getEntityId();

                                int result = nullSafeComparator.compare(entityId1, entityId2);

                                if (result == 0) {
                                        result = getPrincipalIdsString(o1).compareTo(getPrincipalIdsString(o2));
                                }

                                return result;
                        }

                        /**
                         * This method builds a newline delimited String containing the identity's principal IDs in sorted order
                         *
                         * @param entity
                         * @return
                         */
                        private String getPrincipalIdsString(EntityDefault entity) {
                                String result = "";
                                if (entity != null) {
                                        List<Principal> principals = entity.getPrincipals();
                                        if (principals != null) {
                                                if (principals.size() == 1) { // one
                                                        result = principals.get(0).getPrincipalId();
                                                } else { // multiple
                                                        String [] ids = new String [principals.size()];
                                                        int insertIndex = 0;
                                                        for (Principal principal : principals) {
                                                                ids[insertIndex++] = principal.getPrincipalId();
                                                        }
                                                        Arrays.sort(ids);
                                                        result = StringUtils.join(ids, "\n");
                                                }
                                        }
                                }
                                return result;
                        }
                };

                public boolean requestSubmit() {
                        return currentlySubmitted.compareAndSet(false, true);
                }

                /**
                 * Call that tries to flush the write queue.
                 * @see Callable#call()
                 */
                @Override
                public Object call() {
                        try {
                                // the strategy is to grab chunks of entities, dedupe & sort them, and insert them in a big
                                // batch to reduce transaction overhead.  Sorting is done so insertion order is guaranteed, which
                                // prevents deadlocks between concurrent writers to the database.
                                TransactionTemplate template = new TransactionTemplate(transactionManager);
                                template.execute(new TransactionCallback() {
                                        @Override
                                        public Object doInTransaction(TransactionStatus status) {
                                                EntityDefault entity = null;
                                                ArrayList<EntityDefault> entitiesToInsert = new ArrayList<EntityDefault>(getMaxWriteQueueSize());
                                                Set<String> deduper = new HashSet<String>(getMaxWriteQueueSize());

                                                // order is important in this conditional so that elements aren't dequeued and then ignored
                                                while (entitiesToInsert.size() < getMaxWriteQueueSize() && null != (entity = writeQueue.poll())) {
                            //Added an if condition to check whether an entity has a principal
                            if (entity.getPrincipals().size() > 0 && deduper.add(entity.getEntityId())) {
                                                                entitiesToInsert.add(entity);
                                                        }
                                                }

                                                Collections.sort(entitiesToInsert, kediComparator);
                                                for (EntityDefault entityToInsert : entitiesToInsert) {
                                                        dataObjectService.save( new EntityDefaultInfoCacheBo( entityToInsert ) );
                                                }
                                                return null;
                                        }
                                });
                        } finally { // make sure our running flag is unset, otherwise we'll never run again
                                currentlySubmitted.compareAndSet(true, false);
                        }

                        return Boolean.TRUE;
                }
        }

        /**
         * A class encapsulating a {@link ConcurrentLinkedQueue} and an {@link AtomicInteger} to
         * provide fast offer(enqueue)/poll(dequeue) and size checking.  Size may be approximate due to concurrent
         * activity, but for our purposes that is fine.
         *
         * @author Kuali Rice Team (rice.collab@kuali.org)
         *
         */
        protected static class WriteQueue {
                AtomicInteger writeQueueSize = new AtomicInteger(0);
                ConcurrentLinkedQueue<EntityDefault> queue = new ConcurrentLinkedQueue<EntityDefault>();

                public int offerAndGetSize(EntityDefault entity) {
                        queue.add(entity);
                        return writeQueueSize.incrementAndGet();
                }

                protected EntityDefault poll() {
                        EntityDefault result = queue.poll();
                        if (result != null) { writeQueueSize.decrementAndGet(); }
                        return result;
                }
        }

        /**
         * decorator for a callable to log a message before it is executed
         *
         * @author Kuali Rice Team (rice.collab@kuali.org)
         *
         */
        protected static class PreLogCallableWrapper<A> implements Callable<A> {

            protected final Callable inner;
            protected final Level level;
            protected final String message;

                public PreLogCallableWrapper(Callable inner, Level level, String message) {
                        this.inner = inner;
                        this.level = level;
                        this.message = message;
                }

                /**
                 * logs the message then calls the inner Callable
                 *
                 * @see java.util.concurrent.Callable#call()
                 */
                @Override
                @SuppressWarnings("unchecked")
                public A call() throws Exception {
                        LOG.log(level, message);
                        return (A)inner.call();
                }
        }

        /**
         * Adapts a Callable to be Runnable
         *
         * @author Kuali Rice Team (rice.collab@kuali.org)
         *
         */
        protected static class CallableAdapter implements Runnable {

                private final Callable callable;

                public CallableAdapter(Callable callable) {
                        this.callable = callable;
                }

                @Override
                public void run() {
                        try {
                                callable.call();
                        } catch (Exception e) {
                                throw new RuntimeException(e);
                        }
                }
        }

    /**
     * @param dataObjectService the dataObjectService to set
     */
    public void setDataObjectService(DataObjectService dataObjectService) {
        this.dataObjectService = dataObjectService;
    }
}