/*
 * Copyright 2008-present MongoDB, 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.
 */

package com.mongodb.internal.connection;

import com.mongodb.MongoInternalException;
import org.bson.ByteBuf;

import static com.mongodb.internal.connection.MessageHeader.MESSAGE_HEADER_LENGTH;
import static com.mongodb.internal.connection.OpCode.OP_MSG;
import static com.mongodb.internal.connection.OpCode.OP_REPLY;
import static java.lang.String.format;

Contains the details of a reply from a MongoDB server.
@mongodb.driver.manual
../meta-driver/latest/legacy/mongodb-wire-protocol/#database-response-messages Database Response Messages/**
 * Contains the details of a reply from a MongoDB server.
 *
 * @mongodb.driver.manual ../meta-driver/latest/legacy/mongodb-wire-protocol/#database-response-messages Database Response Messages
 */
public final class ReplyHeader {
    
The length of the OP_REPLY header in the MongoDB wire protocol.
/**
     * The length of the OP_REPLY header in the MongoDB wire protocol.
     */
    public static final int REPLY_HEADER_LENGTH = 20;

    
The length of the OP_REPLY header plus the length of the standard message header
/**
     * The length of the OP_REPLY header plus the length of the standard message header
     */
    public static final int TOTAL_REPLY_HEADER_LENGTH = REPLY_HEADER_LENGTH + MESSAGE_HEADER_LENGTH;

    private static final int CURSOR_NOT_FOUND_RESPONSE_FLAG = 1;
    private static final int QUERY_FAILURE_RESPONSE_FLAG = 2;

    private final int messageLength;
    private final int requestId;
    private final int responseTo;
    private final int responseFlags;
    private final long cursorId;
    private final int startingFrom;
    private final int numberReturned;
    private final int opMsgFlagBits;

    ReplyHeader(final ByteBuf header, final MessageHeader messageHeader) {
        this(messageHeader.getMessageLength(), messageHeader.getOpCode(), messageHeader, header);
    }

    ReplyHeader(final ByteBuf header, final CompressedHeader compressedHeader) {
        this(compressedHeader.getUncompressedSize() + MESSAGE_HEADER_LENGTH, compressedHeader.getOriginalOpcode(),
                compressedHeader.getMessageHeader(), header);
    }

    private ReplyHeader(final int messageLength, final int opCode, final MessageHeader messageHeader, final ByteBuf header) {
        this.messageLength = messageLength;
        this.requestId = messageHeader.getRequestId();
        this.responseTo = messageHeader.getResponseTo();
        if (opCode == OP_MSG.getValue()) {
            responseFlags = 0;
            cursorId = 0;
            startingFrom = 0;
            numberReturned = 1;

            opMsgFlagBits = header.getInt();
            header.get();  // ignore payload type
        } else if (opCode == OP_REPLY.getValue()) {
            if (messageLength < TOTAL_REPLY_HEADER_LENGTH) {
                throw new MongoInternalException(format("The reply message length %d is less than the mimimum message length %d",
                        messageLength, TOTAL_REPLY_HEADER_LENGTH));
            }

            responseFlags = header.getInt();
            cursorId = header.getLong();
            startingFrom = header.getInt();
            numberReturned = header.getInt();
            opMsgFlagBits = 0;

            if (numberReturned < 0) {
                throw new MongoInternalException(format("The reply message number of returned documents, %d, is less than 0",
                        numberReturned));
            }
        } else {
            throw new MongoInternalException(format("Unexpected reply message opCode %d", opCode));
        }
    }


    
Gets the total size of the message in bytes. This total includes the 4 bytes that holds the message length.
Returns:
the total message size, including all of the header/**
     * Gets the total size of the message in bytes. This total includes the 4 bytes that holds the message length.
     *
     * @return the total message size, including all of the header
     */
    public int getMessageLength() {
        return messageLength;
    }

    
This is a client or database-generated identifier that uniquely identifies this message. Along with the responseTo field in responses, clients can use this to associate query responses with the originating query. 
Returns:
the identifier for this message/**
     * This is a client or database-generated identifier that uniquely identifies this message. Along with the {@code responseTo} field in
     * responses, clients can use this to associate query responses with the originating query.
     *
     * @return the identifier for this message
     */
    public int getRequestId() {
        return requestId;
    }

    
Along with the requestID field in queries, clients can use this to associate query responses with the originating query.
Returns:
the request ID from the original request/**
     * Along with the requestID field in queries, clients can use this to associate query responses with the originating query.
     *
     * @return the request ID from the original request
     */
    public int getResponseTo() {
        return responseTo;
    }

    
Gets additional information about the response.

    
0 - CursorNotFound: Set when getMore is called but the cursor id is not valid at the server. Returned with zero
    results.
    
1 - QueryFailure: Set when query failed. Results consist of one document containing an "$err" field describing the
    failure.
    
2 - ShardConfigStale: Drivers should ignore this. Only mongos will ever see this set, in which case,
    it needs to update config from the server.
    
3 - AwaitCapable: Set when the server supports the AwaitData Query option. If it doesn't,
    a client should sleep a little between getMore's of a Tailable cursor. Mongod version 1.6 supports AwaitData and thus always
    sets AwaitCapable.
    
4-31 - Reserved: Ignore

Returns:
bit vector - see details above/**
     * Gets additional information about the response.
     * <ul>
     *     <li>0 - <i>CursorNotFound</i>: Set when getMore is called but the cursor id is not valid at the server. Returned with zero
     *     results.</li>
     *     <li>1 - <i>QueryFailure</i>: Set when query failed. Results consist of one document containing an "$err" field describing the
     *     failure.
     *     <li>2 - <i>ShardConfigStale</i>: Drivers should ignore this. Only mongos will ever see this set, in which case,
     *     it needs to update config from the server.
     *     <li>3 - <i>AwaitCapable</i>: Set when the server supports the AwaitData Query option. If it doesn't,
     *     a client should sleep a little between getMore's of a Tailable cursor. Mongod version 1.6 supports AwaitData and thus always
     *     sets AwaitCapable.
     *     <li>4-31 - <i>Reserved</i>: Ignore
     * </ul>
     *
     * @return bit vector - see details above
     */
    public int getResponseFlags() {
        return responseFlags;
    }

    
Gets the cursor ID that this response is a part of. If there are no more documents to fetch from the server, the cursor ID will be 0.
This cursor ID must be used in any messages used to get more data, and also must be closed by the client when no longer needed.
Returns:
cursor ID to use if the client needs to fetch more from the server/**
     * Gets the cursor ID that this response is a part of. If there are no more documents to fetch from the server, the cursor ID will be 0.
     * This cursor ID must be used in any messages used to get more data, and also must be closed by the client when no longer needed.
     *
     * @return cursor ID to use if the client needs to fetch more from the server
     */
    public long getCursorId() {
        return cursorId;
    }

    
Returns the position in the cursor that is the start point of this reply.
Returns:
where in the cursor this reply is starting/**
     * Returns the position in the cursor that is the start point of this reply.
     *
     * @return where in the cursor this reply is starting
     */
    public int getStartingFrom() {
        return startingFrom;
    }

    
Gets the number of documents to expect in the body of this reply.
Returns:
number of documents in the reply/**
     * Gets the number of documents to expect in the body of this reply.
     *
     * @return number of documents in the reply
     */
    public int getNumberReturned() {
        return numberReturned;
    }

    
Gets whether this query was performed with a cursor ID that was not valid on the server.
Returns:
true if this reply indicates the request to get more data was performed with a cursor ID that's not valid on the server/**
     * Gets whether this query was performed with a cursor ID that was not valid on the server.
     *
     * @return true if this reply indicates the request to get more data was performed with a cursor ID that's not valid on the server
     */
    public boolean isCursorNotFound() {
        return (responseFlags & CURSOR_NOT_FOUND_RESPONSE_FLAG) == CURSOR_NOT_FOUND_RESPONSE_FLAG;
    }

    
Gets whether the query failed or not.
Returns:
true if this reply indicates the query failed./**
     * Gets whether the query failed or not.
     *
     * @return true if this reply indicates the query failed.
     */
    public boolean isQueryFailure() {
        return (responseFlags & QUERY_FAILURE_RESPONSE_FLAG) == QUERY_FAILURE_RESPONSE_FLAG;
    }

    // for unit testing
    int getOpMsgFlagBits() {
        return opMsgFlagBits;
    }
}