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/*
 Copyright 2013 Red Hat, Inc. and/or its affiliates.

 This file is part of lightblue.

 This program is free software: you can redistribute it and/or modify
 it under the terms of the GNU General Public License as published by
 the Free Software Foundation, either version 3 of the License, or
 (at your option) any later version.

 This program is distributed in the hope that it will be useful,
 but WITHOUT ANY WARRANTY; without even the implied warranty of
 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 GNU General Public License for more details.

 You should have received a copy of the GNU General Public License
 along with this program.  If not, see .
 */
package com.redhat.lightblue.eval;

import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

import com.fasterxml.jackson.databind.JsonNode;
import com.redhat.lightblue.crud.CrudConstants;
import com.redhat.lightblue.metadata.FieldTreeNode;
import com.redhat.lightblue.query.ValueComparisonExpression;
import com.redhat.lightblue.query.BinaryComparisonOperator;
import com.redhat.lightblue.util.Path;
import com.redhat.lightblue.util.KeyValueCursor;

public class ValueComparisonEvaluator extends QueryEvaluator {

    private static final Logger LOGGER = LoggerFactory.getLogger(ValueComparisonEvaluator.class);

    private final FieldTreeNode fieldMd;
    private final Path field;
    private final BinaryComparisonOperator operator;
    private final Object value;

    /**
     * Constructs evaluator for {field op value} style comparison
     *
     * @param expr The expression
     * @param md Entity metadata
     */
    public ValueComparisonEvaluator(ValueComparisonExpression expr, FieldTreeNode context) {
        this.field = expr.getField();
        fieldMd = context.resolve(field);
        if (fieldMd == null) {
            throw new EvaluationError(expr, CrudConstants.ERR_FIELD_NOT_THERE + field);
        }
        operator = expr.getOp();
        value = expr.getRvalue().getValue();
        LOGGER.debug("ctor {} {} {}", field, operator, value);
    }

    @Override
    public boolean evaluate(QueryEvaluationContext ctx) {
        LOGGER.debug("evaluate {} {} {}", field, operator, value);
        KeyValueCursor cursor = ctx.getNodes(field);
        while (cursor.hasNext()) {
            cursor.next();
            JsonNode valueNode = cursor.getCurrentValue();
            Object docValue;
            if (valueNode != null) {
                docValue = fieldMd.getType().fromJson(valueNode);
            } else {
                docValue = null;
            }
            LOGGER.debug(" value={}", valueNode);
            int result = fieldMd.getType().compare(docValue, value);
            LOGGER.debug(" result={}", result);
            ctx.setResult(operator.apply(result));
            if (ctx.getResult()) {
                break;
            }
        }
        return ctx.getResult();
    }
}