/*
 * Copyright (c) "Neo4j"
 * Neo4j Sweden AB [http://neo4j.com]
 *
 * This file is part of Neo4j.
 *
 * Neo4j 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 <http://www.gnu.org/licenses/>.
 */
package org.neo4j.kernel.impl.newapi;

import org.neo4j.internal.kernel.api.IndexQueryConstraints;
import org.neo4j.internal.kernel.api.PartitionedScan;
import org.neo4j.internal.kernel.api.PropertyIndexQuery;
import org.neo4j.internal.kernel.api.security.AccessMode;
import org.neo4j.internal.schema.IndexDescriptor;
import org.neo4j.io.pagecache.context.CursorContext;
import org.neo4j.kernel.api.ExecutionContext;
import org.neo4j.kernel.api.index.IndexProgressor;
import org.neo4j.kernel.impl.index.schema.PartitionedValueSeek;

public class PartitionedValueIndexCursorSeek<Cursor extends org.neo4j.internal.kernel.api.Cursor>
        implements PartitionedScan<Cursor> {
    // Read is generally not a thread-safe object.
    // This one belongs to the thread that initialised the partitioned scan.
    // Even thought the operations performed by the partitioned scan on the Read should be OK, we prefer the threads
    // working with the partition to use their own Reads.
    // In other words, using this "global" Read makes thread-safety of the scan a bit questionable.
    private final Read initialRead;
    private final PartitionedValueSeek valueSeek;
    private final PropertyIndexQuery[] query;
    private final IndexDescriptor descriptor;

    PartitionedValueIndexCursorSeek(
            Read read, IndexDescriptor descriptor, PartitionedValueSeek valueSeek, PropertyIndexQuery... query) {
        if (read.hasTxStateWithChanges()) {
            throw new IllegalStateException(
                    "Transaction contains changes; PartitionScan is only valid in Read-Only transactions.");
        }
        this.initialRead = read;
        this.descriptor = descriptor;
        this.valueSeek = valueSeek;
        this.query = query;
    }

    @Override
    public int getNumberOfPartitions() {
        return valueSeek.getNumberOfPartitions();
    }

    @Override
    public boolean reservePartition(Cursor cursor, CursorContext cursorContext, AccessMode accessMode) {
        return reservePartition(cursor, initialRead, cursorContext, accessMode);
    }

    @Override
    public boolean reservePartition(Cursor cursor, ExecutionContext executionContext) {
        return reservePartition(
                cursor,
                (org.neo4j.kernel.impl.newapi.Read) executionContext.dataRead(),
                executionContext.cursorContext(),
                executionContext.securityContext().mode());
    }

    private boolean reservePartition(Cursor cursor, Read read, CursorContext cursorContext, AccessMode accessMode) {
        final var indexCursor = (DefaultEntityValueIndexCursor<?>) cursor;
        indexCursor.setRead(read);
        final var indexProgressor = valueSeek.reservePartition(indexCursor, cursorContext);
        if (indexProgressor == IndexProgressor.EMPTY) {
            return false;
        }
        indexCursor.initialize(
                descriptor, indexProgressor, accessMode, false, false, IndexQueryConstraints.unorderedValues(), query);
        return true;
    }
}
