/**
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF licenses this file
 * to you 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 edu.uci.ics.hivesterix.serde.lazy;

import java.util.ArrayList;
import java.util.Arrays;
import java.util.List;

import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;
import org.apache.hadoop.hive.serde2.objectinspector.ObjectInspector;
import org.apache.hadoop.hive.serde2.objectinspector.StructField;
import org.apache.hadoop.hive.serde2.objectinspector.StructObjectInspector;

import edu.uci.ics.hivesterix.serde.lazy.LazyUtils.RecordInfo;
import edu.uci.ics.hivesterix.serde.lazy.objectinspector.LazyStructObjectInspector;

/**
 * LazyStruct is serialized as follows: start A B A B A B end bytes[] ->
 * |-----|---------|--- ... ---|-----|---------|
 * Section A is one null-byte, corresponding to eight struct fields in Section
 * B. Each bit indicates whether the corresponding field is null (0) or not null
 * (1). Each field is a LazyObject.
 * Following B, there is another section A and B. This pattern repeats until the
 * all struct fields are serialized.
 */
public class LazyStruct extends LazyNonPrimitive<LazyStructObjectInspector> {

    private static Log LOG = LogFactory.getLog(LazyStruct.class.getName());

    /**
     * Whether the data is already parsed or not.
     */
    boolean parsed;

    /**
     * The fields of the struct.
     */
    @SuppressWarnings("rawtypes")
    LazyObject[] fields;

    /**
     * Whether a field is initialized or not.
     */
    boolean[] fieldInited;

    /**
     * Whether a field is null or not. Because length is 0 does not means the
     * field is null. In particular, a 0-length string is not null.
     */
    boolean[] fieldIsNull;

    /**
     * The start positions and lengths of struct fields. Only valid when the
     * data is parsed.
     */
    int[] fieldStart;
    int[] fieldLength;

    /**
     * Construct a LazyStruct object with an ObjectInspector.
     */
    protected LazyStruct(LazyStructObjectInspector oi) {
        super(oi);
    }

    @Override
    public void init(byte[] bytes, int start, int length) {
        super.init(bytes, start, length);
        parsed = false;
    }

    RecordInfo recordInfo = new LazyUtils.RecordInfo();
    boolean missingFieldWarned = false;
    boolean extraFieldWarned = false;

    /**
     * Parse the byte[] and fill fieldStart, fieldLength, fieldInited and
     * fieldIsNull.
     */
    private void parse() {

        List<? extends StructField> fieldRefs = ((StructObjectInspector) oi).getAllStructFieldRefs();

        if (fields == null) {
            fields = new LazyObject[fieldRefs.size()];
            for (int i = 0; i < fields.length; i++) {
                ObjectInspector insp = fieldRefs.get(i).getFieldObjectInspector();
                fields[i] = insp == null ? null : LazyFactory.createLazyObject(insp);
            }
            fieldInited = new boolean[fields.length];
            fieldIsNull = new boolean[fields.length];
            fieldStart = new int[fields.length];
            fieldLength = new int[fields.length];
        }

        /**
         * Please note that one null byte is followed by eight fields, then more
         * null byte and fields.
         */

        int fieldId = 0;
        int structByteEnd = start + length;

        byte nullByte = bytes[start];
        int lastFieldByteEnd = start + 1;
        // Go through all bytes in the byte[]
        for (int i = 0; i < fields.length; i++) {
            fieldIsNull[i] = true;
            if ((nullByte & (1 << (i % 8))) != 0) {
                fieldIsNull[i] = false;
                LazyUtils.checkObjectByteInfo(fieldRefs.get(i).getFieldObjectInspector(), bytes, lastFieldByteEnd,
                        recordInfo);
                fieldStart[i] = lastFieldByteEnd + recordInfo.elementOffset;
                fieldLength[i] = recordInfo.elementSize;
                lastFieldByteEnd = fieldStart[i] + fieldLength[i];
            }

            // count how many fields are there
            if (lastFieldByteEnd <= structByteEnd) {
                fieldId++;
            }
            // next byte is a null byte if there are more bytes to go
            if (7 == (i % 8)) {
                if (lastFieldByteEnd < structByteEnd) {
                    nullByte = bytes[lastFieldByteEnd];
                    lastFieldByteEnd++;
                } else {
                    // otherwise all null afterwards
                    nullByte = 0;
                    lastFieldByteEnd++;
                }
            }
        }

        // Extra bytes at the end?
        if (!extraFieldWarned && lastFieldByteEnd < structByteEnd) {
            extraFieldWarned = true;
            LOG.warn("Extra bytes detected at the end of the row! Ignoring similar " + "problems.");
        }

        // Missing fields?
        if (!missingFieldWarned && lastFieldByteEnd > structByteEnd) {
            missingFieldWarned = true;
            LOG.warn("Missing fields! Expected " + fields.length + " fields but " + "only got " + fieldId
                    + "! Ignoring similar problems.");
        }

        Arrays.fill(fieldInited, false);
        parsed = true;
    }

    /**
     * Get one field out of the struct.
     * If the field is a primitive field, return the actual object. Otherwise
     * return the LazyObject. This is because PrimitiveObjectInspector does not
     * have control over the object used by the user - the user simply directly
     * use the Object instead of going through Object
     * PrimitiveObjectInspector.get(Object).
     * 
     * @param fieldID
     *            The field ID
     * @return The field as a LazyObject
     */
    public Object getField(int fieldID) {
        if (!parsed) {
            parse();
        }
        return uncheckedGetField(fieldID);
    }

    /**
     * Get the field out of the row without checking parsed. This is called by
     * both getField and getFieldsAsList.
     * 
     * @param fieldID
     *            The id of the field starting from 0.
     * @return The value of the field
     */
    private Object uncheckedGetField(int fieldID) {
        // Test the length first so in most cases we avoid doing a byte[]
        // comparison.
        if (fieldIsNull[fieldID]) {
            return null;
        }
        if (!fieldInited[fieldID]) {
            fieldInited[fieldID] = true;
            fields[fieldID].init(bytes, fieldStart[fieldID], fieldLength[fieldID]);
        }
        return fields[fieldID].getObject();
    }

    ArrayList<Object> cachedList;

    /**
     * Get the values of the fields as an ArrayList.
     * 
     * @return The values of the fields as an ArrayList.
     */
    public ArrayList<Object> getFieldsAsList() {
        if (!parsed) {
            parse();
        }
        if (cachedList == null) {
            cachedList = new ArrayList<Object>();
        } else {
            cachedList.clear();
        }
        for (int i = 0; i < fields.length; i++) {
            cachedList.add(uncheckedGetField(i));
        }
        return cachedList;
    }

    @Override
    public Object getObject() {
        return this;
    }
}