// MongoInputSplit.java
/*
 * Copyright 2010 10gen 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.hadoop.mapred.input;

import java.io.*;
import java.util.*;

import org.apache.commons.logging.*;
import org.apache.hadoop.io.*;
import org.apache.hadoop.mapred.*;

import com.mongodb.*;
import com.mongodb.hadoop.util.*;
import com.mongodb.util.*;

@SuppressWarnings("deprecation")
public class MongoInputSplit implements Writable, InputSplit {

    public MongoInputSplit(MongoURI inputURI, DBObject query, DBObject fields, DBObject sort, int limit, int skip) {
        log.info("Creating a new MongoInputSplit for MongoURI '"
                 + inputURI
                 + "', query: '"
                 + query
                 + "', fieldSpec: '"
                 + fields
                 + "', sort: '"
                 + sort
                 + "', limit: "
                 + limit
                 + ", skip: "
                 + skip
                 + " .");
        _mongoURI = inputURI;
        _querySpec = query;
        _fieldSpec = fields;
        _sortSpec = sort;
        _limit = limit;
        _skip = skip;
    }

    public MongoInputSplit() {
    }

    public long getLength() {
        return getCursor().size();
    }

    public String[] getLocations() {
        final List<String> hosts = _mongoURI.getHosts();
        return hosts.toArray(new String[hosts.size()]);
    }

    /**
     * Serialize the Split instance
     */

    public void write(DataOutput out) throws IOException {
        final ObjectOutputStream objOut = new ObjectOutputStream((OutputStream) out);
        // TODO - Use object outputstream instead of going to <-> from string?
        out.writeUTF(_mongoURI.toString());

        out.writeUTF(JSON.serialize(_querySpec));
        out.writeUTF(JSON.serialize(_fieldSpec));
        out.writeUTF(JSON.serialize(_sortSpec));
        out.writeInt(_limit);
        out.writeInt(_skip);
        objOut.close();
    }

    public void readFields(DataInput in) throws IOException {
        final ObjectInputStream objIn = new ObjectInputStream((InputStream) in);

        _mongoURI = new MongoURI(in.readUTF());
        _querySpec = (DBObject) JSON.parse(in.readUTF());
        _fieldSpec = (DBObject) JSON.parse(in.readUTF());
        _sortSpec = (DBObject) JSON.parse(in.readUTF());
        _limit = in.readInt();
        _skip = in.readInt();

        log.info("Deserialized MongoInputSplit ... { length = "
                 + getLength()
                 + ", locations = "
                 + getLocations()
                 + ", query = "
                 + _querySpec
                 + ", fields = "
                 + _fieldSpec
                 + ", sort = "
                 + _sortSpec
                 + ", limit = "
                 + _limit
                 + ", skip = "
                 + _skip
                 + "}");

        objIn.close();
    }

    DBCursor getCursor() {
        // Return the cursor with the split's query, etc. already slotted in for
        // them.
        // todo - support limit/skip
        final DBCursor cursor = MongoConfigUtil.getCollection(_mongoURI).find(_querySpec, _fieldSpec).sort(_sortSpec);
        cursor.slaveOk();
        return cursor;
    }

    private MongoURI _mongoURI;
    private DBObject _querySpec;
    private DBObject _fieldSpec;
    private DBObject _sortSpec;
    private int _limit = 0;
    private int _skip = 0;

    private static final Log log = LogFactory.getLog(MongoInputSplit.class);

}