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/*
 Licensed to Diennea S.r.l. under one
 or more contributor license agreements. See the NOTICE file
 distributed with this work for additional information
 regarding copyright ownership. Diennea S.r.l. 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 herddb.utils;

import java.util.Collections;
import java.util.HashMap;
import java.util.Map;
import java.util.function.BiConsumer;

public interface DataAccessor {

    Object get(String property);

    default Map toMap() {
        HashMap res = new HashMap<>();
        forEach(res::put);
        return res;
    }

    String[] getFieldNames();

    default int getNumFields() {
        return getFieldNames().length;
    }

    default void forEach(BiConsumer consumer) {
        for (String property : getFieldNames()) {
            consumer.accept(property, get(property));
        }
    }

    default Object get(int index) {
        return get(getFieldNames()[index]);
    }

    default boolean fieldEqualsTo(int index, Object value) {
        Object val = get(index);
        if (val == null) {
            // NULL is never equal to any other value, even NULL is not equal to NULL
            return false;
        }
        return SQLRecordPredicateFunctions.objectEquals(val, value);
    }

    default boolean fieldNotEqualsTo(int index, Object value) {
        Object val = get(index);
        if (val == null) {
            // NULL is never non-equal to any other value, even NULL is not non-equal to NULL
            return false;
        }
        return SQLRecordPredicateFunctions.objectNotEquals(val, value);
    }

    default SQLRecordPredicateFunctions.CompareResult fieldCompareTo(int index, Object value) {
        Object val = get(index);
        if (val == null) {
             // NULL is not comparable
            return SQLRecordPredicateFunctions.CompareResult.NULL;
        }
        return SQLRecordPredicateFunctions.compareConsiderNull(val, value);
    }

    default Object[] getValues() {
        String[] fieldNames = getFieldNames();
        Object[] result = new Object[fieldNames.length];
        for (int i = 0; i < fieldNames.length; i++) {
            result[i] = get(fieldNames[i]);
        }
        return result;
    }

    DataAccessor NULL = new AbstractDataAccessor() {

        @Override
        public void forEach(BiConsumer consumer) {
        }

        @Override
        public Object get(int index) {
            return null;
        }

        @Override
        public boolean fieldEqualsTo(int index, Object value) {
            // nothing is "equal" to NULL
            return false;
        }

        @Override
        public boolean fieldNotEqualsTo(int index, Object value) {
            // nothing is "not equal" to NULL
            return false;
        }

        @Override
        public SQLRecordPredicateFunctions.CompareResult fieldCompareTo(int index, Object value) {
            return SQLRecordPredicateFunctions.CompareResult.NULL;
        }


        @Override
        public Object[] getValues() {
            return Constants.EMPTY_OBJECT_ARRAY;
        }

        @Override
        public Object get(String property) {
            return null;
        }

        @Override
        public Map toMap() {
            return Collections.emptyMap();
        }

        @Override
        public String[] getFieldNames() {
            return Constants.EMPTY_STRING_ARRAY;
        }

    };

    // CHECKSTYLE.OFF: MethodName
    static DataAccessor ALL_NULLS(String[] fieldNames) {
        return new AllNullsDataAccessor(fieldNames);
    }
    // CHECKSTYLE.ON: MethodName

}