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/*
 * 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 org.apache.phoenix.expression.function;

import java.util.Arrays;
import java.util.Collections;
import java.util.List;
import org.apache.hadoop.hbase.filter.CompareFilter.CompareOp;
import org.apache.phoenix.compile.KeyPart;
import org.apache.phoenix.expression.Expression;
import org.apache.phoenix.query.KeyRange;
import org.apache.phoenix.query.QueryConstants;
import org.apache.phoenix.schema.PColumn;
import org.apache.phoenix.schema.PTable;
import org.apache.phoenix.schema.SortOrder;
import org.apache.phoenix.schema.types.PDataType;
import org.apache.phoenix.util.ByteUtil;

abstract public class PrefixFunction extends ScalarFunction {
    public PrefixFunction() { }

    public PrefixFunction(List children) {
        super(children);
    }

    @Override
    public int getKeyFormationTraversalIndex() {
        return preservesOrder() == OrderPreserving.NO ? NO_TRAVERSAL : 0;
    }
    
    protected boolean extractNode() {
        return false;
    }

    @Override
    public KeyPart newKeyPart(final KeyPart childPart) {
        return new PrefixKeyPart(childPart);
    }

    private class PrefixKeyPart implements KeyPart {
        private final List extractNodes = extractNode() ?
                Collections.singletonList(PrefixFunction.this)
                : Collections.emptyList();
        private final KeyPart childPart;

        PrefixKeyPart(KeyPart childPart) {
            this.childPart = childPart;
        }

        @Override
        public PColumn getColumn() {
            return childPart.getColumn();
        }

        @Override
        public List getExtractNodes() {
            return extractNodes;
        }

        @Override
        public KeyRange getKeyRange(CompareOp op, Expression rhs) {
            byte[] lowerRange = KeyRange.UNBOUND;
            byte[] upperRange = KeyRange.UNBOUND;
            boolean lowerInclusive = true;
            PDataType type = getColumn().getDataType();
            switch (op) {
                case EQUAL:
                    lowerRange = evaluateExpression(rhs);
                    upperRange = ByteUtil.nextKey(lowerRange);
                    break;
                case GREATER:
                    lowerRange = ByteUtil.nextKey(evaluateExpression(rhs));
                    break;
                case LESS_OR_EQUAL:
                    upperRange = ByteUtil.nextKey(evaluateExpression(rhs));
                    lowerInclusive = false;
                    break;
                default:
                    return childPart.getKeyRange(op, rhs);
            }
            PColumn column = getColumn();
            Integer length = column.getMaxLength();
            if (type.isFixedWidth()) {
                if (length != null) { // Sanity check - shouldn't be necessary
                    // Don't pad based on current sort order, but instead use our
                    // minimum byte as otherwise we'll end up skipping rows in
                    // the case of descending, since rows with more padding appear
                    // *after* rows with no padding.
                    if (lowerRange != KeyRange.UNBOUND) {
                        lowerRange = type.pad(lowerRange, length, SortOrder.ASC);
                    }
                    if (upperRange != KeyRange.UNBOUND) {
                        upperRange = type.pad(upperRange, length, SortOrder.ASC);
                    }
                }
            } else if (column.getSortOrder() == SortOrder.DESC && getTable().rowKeyOrderOptimizable()) {
                // Append a zero byte if descending since a \xFF byte will be appended to the lowerRange
                // causing rows to be skipped that should be included. For example, with rows 'ab', 'a',
                // a lowerRange of 'a\xFF' would skip 'ab', while 'a\x00\xFF' would not.
                if (lowerRange != KeyRange.UNBOUND) {
                    lowerRange = Arrays.copyOf(lowerRange, lowerRange.length+1);
                    lowerRange[lowerRange.length-1] = QueryConstants.SEPARATOR_BYTE;
                }
            }
            KeyRange range = KeyRange.getKeyRange(lowerRange, lowerInclusive, upperRange, false);
            if (column.getSortOrder() == SortOrder.DESC) {
                range = range.invert();
            }
            return range;
        }

        @Override
        public PTable getTable() {
            return childPart.getTable();
        }
    }

}