/*

  * #%L

  * Command.java - mongodb-async-driver - Allanbank Consulting, Inc.

  * %%

  * Copyright (C) 2011 - 2014 Allanbank Consulting, Inc.

  * %%

  * 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.

  * #L%

  */

 package com.allanbank.mongodb.client.message;

 import java.io.IOException;

 import java.util.Iterator;

 import com.allanbank.mongodb.ReadPreference;

 import com.allanbank.mongodb.bson.Document;

 import com.allanbank.mongodb.bson.Element;

 import com.allanbank.mongodb.bson.impl.EmptyDocument;

 import com.allanbank.mongodb.bson.io.BsonOutputStream;

 import com.allanbank.mongodb.bson.io.BufferingBsonOutputStream;

 import com.allanbank.mongodb.bson.io.StringEncoder;

 import com.allanbank.mongodb.client.Operation;

 import com.allanbank.mongodb.client.VersionRange;

 import com.allanbank.mongodb.error.DocumentToLargeException;

 /**

  * Helper class to make generating command queries easier. Commands are

  * communicated to the server as {@link Operation#QUERY} messages. We don't use

  * the Query class as a base class as it adds a lot of weight to the commands.

  * 

  * @api.no This class is <b>NOT</b> part of the drivers API. This class may be

  *         mutated in incompatible ways between any two releases of the driver.

  * @copyright 2011-2013, Allanbank Consulting, Inc., All Rights Reserved

  */

 public class Command extends AbstractMessage {

     /** The collection to use when issuing commands to the database. */

     public static final String COMMAND_COLLECTION = "$cmd";

     /** The amount of head room for jumbo documents. */

     private static final int HEADROOM = 16 * 1024;

     /**

      * If true then the command document is allowed to slightly exceed the

      * document size limit.

      */

     private boolean myAllowJumbo = false;

     /** The command's document. */

     private final Document myCommand;

     /** The command's document to use in routing decisions. */

     private final Document myRoutingDocument;

     /**

      * Create a new Command.

      * 

      * @param databaseName

      *            The name of the database.

      * @param collectionName

      *            The name of the collection the command is using. This should

      *            be the real collection and not {@value #COMMAND_COLLECTION} if

      *            the real collection is known.

      * @param commandDocument

      *            The command document containing the command and options.

      */

     public Command(final String databaseName, final String collectionName,

             final Document commandDocument) {

         this(databaseName, collectionName, commandDocument,

                 ReadPreference.PRIMARY);

     }

     /**

      * Create a new Command.

      * 

      * @param databaseName

      *            The name of the database.

      * @param collectionName

      *            The name of the collection the command is using. This should

      *            be the real collection and not {@value #COMMAND_COLLECTION} if

      *            the real collection is known.

      * @param commandDocument

      *            The command document containing the command and options.

      * @param routingDocument

      *            The document that should be used for routing the command.

      * @param readPreference

      *            The preference for which servers to use to retrieve the

      *            results.

      * @param requiredServerVersion

      *            The required version of the server to support processing the

      *            message.

      */

     public Command(final String databaseName, final String collectionName,

             final Document commandDocument, final Document routingDocument,

             final ReadPreference readPreference,

             final VersionRange requiredServerVersion) {

         super(databaseName, collectionName, readPreference,

                 requiredServerVersion);

         myCommand = commandDocument;

         myRoutingDocument = routingDocument;

     }

     /**

      * Create a new Command.

      * 

      * @param databaseName

      *            The name of the database.

      * @param collectionName

      *            The name of the collection the command is using. This should

      *            be the real collection and not {@value #COMMAND_COLLECTION} if

      *            the real collection is known.

      * @param commandDocument

      *            The command document containing the command and options.

      * @param readPreference

      *            The preference for which servers to use to retrieve the

      *            results.

      */

     public Command(final String databaseName, final String collectionName,

             final Document commandDocument, final ReadPreference readPreference) {

         this(databaseName, collectionName, commandDocument, readPreference,

                 null);

     }

     /**

      * Create a new Command.

      * 

      * @param databaseName

      *            The name of the database.

      * @param collectionName

      *            The name of the collection the command is using. This should

      *            be the real collection and not {@value #COMMAND_COLLECTION} if

      *            the real collection is known.

      * @param commandDocument

      *            The command document containing the command and options.

      * @param readPreference

      *            The preference for which servers to use to retrieve the

      *            results.

      * @param requiredServerVersion

      *            The required version of the server to support processing the

      *            message.

      */

     public Command(final String databaseName, final String collectionName,

             final Document commandDocument,

             final ReadPreference readPreference,

             final VersionRange requiredServerVersion) {

         this(databaseName, collectionName, commandDocument,

                 EmptyDocument.INSTANCE, readPreference, requiredServerVersion);

     }

     /**

      * Determines if the passed object is of this same type as this object and

      * if so that its fields are equal.

      * 

      * @param object

      *            The object to compare to.

      * 

      * @see java.lang.Object#equals(java.lang.Object)

      */

     @Override

     public boolean equals(final Object object) {

         boolean result = false;

         if (this == object) {

             result = true;

         }

         else if ((object != null) && (getClass() == object.getClass())) {

             final Command other = (Command) object;

             result = super.equals(object) && myCommand.equals(other.myCommand);

         }

         return result;

     }

     /**

      * Returns the command's document.

      * 

      * @return The command's document.

      */

     public Document getCommand() {

         return myCommand;

     }

     /**

      * {@inheritDoc}

      * <p>

      * Overridden to return the command name.

      * </p>

      */

     @Override

     public String getOperationName() {

         // Return the value for the first element in the document.

         final Iterator<Element> iter = myCommand.iterator();

         if (iter.hasNext()) {

             return iter.next().getName();

         }

         // Not expected. Command documents should have atleast one element. Just

         // return a generic name here.

         return "command";

     }

     /**

      * Returns the routingDocument value.

      * 

      * @return The routingDocument value.

      */

     public Document getRoutingDocument() {

         return myRoutingDocument;

     }

     /**

      * Computes a reasonable hash code.

      * 

      * @return The hash code value.

      */

     @Override

     public int hashCode() {

         int result = 1;

         result = (31 * result) + super.hashCode();

         result = (31 * result) + myCommand.hashCode();

         return result;

     }

     /**

      * Returns true if the command document is allowed to slightly exceed the

      * document size limit.

      * 

      * @return True if the command document is allowed to slightly exceed the

      *         document size limit.

      */

     public boolean isAllowJumbo() {

         return myAllowJumbo;

     }

     /**

      * If set to true then the command document is allowed to slightly exceed

      * the document size limit. This allows us to pack a full size document in a

      * insert command.

      * 

      * @param allowJumbo

      *            If true then the command document is allowed to slightly

      *            exceed the document size limit.

      */

     public void setAllowJumbo(final boolean allowJumbo) {

         myAllowJumbo = allowJumbo;

     }

     /**

      * {@inheritDoc}

      * <p>

      * Overridden to return the size of the {@link Command}.

      * </p>

      */

     @Override

     public int size() {

         int size = HEADER_SIZE + 18; // See below.

         // size += 4; // flags;

         size += StringEncoder.utf8Size(myDatabaseName);

         // size += 1; // StringEncoder.utf8Size(".");

         // size += 4; // StringEncoder.utf8Size(COMMAND_COLLECTION);

         // size += 1; // \0 on the CString.

         // size += 4; // numberToSkip

         // size += 4; // numberToReturn

         size += myCommand.size();

         return size;

     }

     /**

      * {@inheritDoc}

      * <p>

      * Overridden to return a human readable form of the command.

      * </p>

      */

     @Override

     public String toString() {

         final StringBuilder builder = new StringBuilder();

         builder.append("Command[");

         builder.append(getOperationName());

         builder.append(", db=");

         builder.append(myDatabaseName);

         builder.append(", collection=");

         builder.append(myCollectionName);

         if (getReadPreference() != null) {

             builder.append(", readPreference=");

             builder.append(getReadPreference());

         }

         if (getRequiredVersionRange() != null) {

             builder.append(", requiredVersionRange=");

             builder.append(getRequiredVersionRange());

         }

         builder.append("]: ");

         builder.append(myCommand);

         return builder.toString();

     }

     /**

      * {@inheritDoc}

      * <p>

      * Overridden to make sure the command document is not too large.

      * </p>

      */

     @Override

     public void validateSize(final int maxDocumentSize)

             throws DocumentToLargeException {

         final long size = myCommand.size();

         if (isAllowJumbo()) {

             if ((maxDocumentSize + HEADROOM) < size) {

                 throw new DocumentToLargeException((int) size, maxDocumentSize

                         + HEADROOM, myCommand);

             }

         }

         else if (maxDocumentSize < size) {

             throw new DocumentToLargeException((int) size, maxDocumentSize,

                     myCommand);

         }

     }

     /**

      * {@inheritDoc}

      * <p>

      * Overridden to write the Command as a {@link Operation#QUERY} message.

      * </p>

      */

     @Override

     public void write(final int messageId, final BsonOutputStream out)

             throws IOException {

         final int numberToSkip = 0;

         final int numberToReturn = -1; // Unlimited

         final int flags = computeFlags();

         int size = HEADER_SIZE;

         size += 4; // flags;

         size += out.sizeOfCString(myDatabaseName, ".", COMMAND_COLLECTION);

         size += 4; // numberToSkip

         size += 4; // numberToReturn

         size += myCommand.size();

         writeHeader(out, messageId, 0, Operation.QUERY, size);

         out.writeInt(flags);

         out.writeCString(myDatabaseName, ".", COMMAND_COLLECTION);

         out.writeInt(numberToSkip);

         out.writeInt(numberToReturn);

         out.writeDocument(myCommand);

     }

     /**

      * {@inheritDoc}

      * <p>

      * Overridden to write the Command as a {@link Operation#QUERY} message.

      * </p>

      */

     @Override

     public void write(final int messageId, final BufferingBsonOutputStream out)

             throws IOException {

         final int numberToSkip = 0;

         final int numberToReturn = -1; // Unlimited

         final int flags = computeFlags();

         final long start = writeHeader(out, messageId, 0, Operation.QUERY);

         out.writeInt(flags);

         out.writeCString(myDatabaseName, ".", COMMAND_COLLECTION);

         out.writeInt(numberToSkip);

         out.writeInt(numberToReturn);

         out.writeDocument(myCommand);

         finishHeader(out, start);

         out.flushBuffer();

     }

     /**

      * Computes the message flags bit field.

      * 

      * @return The message flags bit field.

      */

     private int computeFlags() {

         int flags = 0;

         if (getReadPreference().isSecondaryOk()) {

             flags += Query.REPLICA_OK_FLAG_BIT;

         }

         return flags;

     }

 }