/*
 * Copyright Elasticsearch B.V. and/or licensed to Elasticsearch B.V. under one
 * or more contributor license agreements. Licensed under the "Elastic License
 * 2.0", the "GNU Affero General Public License v3.0 only", and the "Server Side
 * Public License v 1"; you may not use this file except in compliance with, at
 * your election, the "Elastic License 2.0", the "GNU Affero General Public
 * License v3.0 only", or the "Server Side Public License, v 1".
 */

package org.elasticsearch.script.expression;

import org.apache.lucene.index.LeafReaderContext;
import org.apache.lucene.search.DoubleValues;
import org.elasticsearch.index.fielddata.IndexFieldData;
import org.elasticsearch.index.fielddata.LeafNumericFieldData;
import org.elasticsearch.index.fielddata.SortedNumericDoubleValues;

import java.io.IOException;

/**
 * ValueSource to return non-zero if a field is missing.
 * <p>
 * This is essentially sugar over !count()
 */
final class EmptyMemberValueSource extends FieldDataBasedDoubleValuesSource {

    EmptyMemberValueSource(IndexFieldData<?> fieldData) {
        super(fieldData);
    }

    @Override
    public DoubleValues getValues(LeafReaderContext leaf, DoubleValues scores) {
        LeafNumericFieldData leafData = (LeafNumericFieldData) fieldData.load(leaf);
        final SortedNumericDoubleValues values = leafData.getDoubleValues();
        return DoubleValues.withDefault(new DoubleValues() {
            @Override
            public double doubleValue() {
                return 0;
            }

            @Override
            public boolean advanceExact(int doc) throws IOException {
                return values.advanceExact(doc);
            }
        }, 1);
    }

    @Override
    public int hashCode() {
        return 31 * getClass().hashCode() + fieldData.hashCode();
    }

    @Override
    public boolean equals(Object obj) {
        if (this == obj) return true;
        if (obj == null) return false;
        if (getClass() != obj.getClass()) return false;
        EmptyMemberValueSource other = (EmptyMemberValueSource) obj;
        return fieldData.equals(other.fieldData);
    }

    @Override
    public String toString() {
        return "empty: field(" + fieldData.getFieldName() + ")";
    }

}